JK-BMS decision, balance cable resistance and the biggest battery test ever. Battery 2.0

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JK-BMS decision, balance cable resistance and the biggest battery test ever. Battery 2.0

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Күн бұрын

Thank you very much for all your feedback under my last video. It really helped me to make the right decision about the cable upgrade of the JK-BMS.
Do we need to pay attention to the resistance of balance cables. This was a hot discussed topic in the last video and I give you my opinion here on why I think it is not important.
The donated 'bended' cable lugs have arrived and, oh wow, are they expensive! I'm very embarrassed that someone actually gifted them to me. Thank you Dan, it is much appreciated!
Also, the single stud bus bars have arrived. With a little trick you've told me, we can modify them to a small two way bus bar. I think I will go ahead with them and mount the JK-BMS to it...
At the end I'm spoiling a bit what's next here on the channel as we approach the maybe biggest and most anticipated battery test ever...
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Пікірлер: 277

@upnorthandpersonal 2 жыл бұрын

Let's do a calculation. Rds_on = 3.2mR typical at 25C. We have 10 pairs on the top and 10 pairs at the bottom. These are configured back to back (see my post on the forum on that), gives 6.4mR per pair at 25C. These 20 back to back pairs give a resistance of 6.4/20 = 0.32mR. Heating occurring at 200A continuous, P = R I^2 = 12.8W. Should be perfectly fine with that case acting as a heat sink.

@pederb82 2 жыл бұрын

And also the length of the cable. Might get luke warm but not hot. :)

@OffGridGarageAustralia 2 жыл бұрын

Peder, length of the cable is not of interest when it comes to current capacity.

@jasondevine6014 2 жыл бұрын

Yes the limit is the rds not the current rating.

@pragmaticcosmic2826 2 жыл бұрын

In practice the current is limited by the bond wires to the chip and is much less than the stated spec...these are lab specs with an almost infinite heatsink attached....not real world hence the need for lots in parallel.

@ToBeDefined85 2 жыл бұрын

Has anyone measured the voltage drop across both FET banks ? I would like to know if the 6.4mOhm is true for a certain (high) current. Lets say 100A load. ?

@felaxchow207 2 жыл бұрын

Don’t forget it is 200°C silicone insulated wire and the max ampacity is about 200 amps for #7 AWG wire. Double that and you’re well within the tolerances. However most building cables are rated for 60°C of the same size would definitely not be able to handle that much current without the insulation melting. Your weakest point will be the terminal lugs.

@nateb3105 2 жыл бұрын

yeah 100% just reading this myself. Its all about the insulation material - i've always been looking at regular PVC which is ~100deg rated.

@OffGridGarageAustralia 2 жыл бұрын

Thanks Felax. I will sandwich the larger cable in between the two 7AWG cable lugs to have the best contact. With 80A max, I'm not expecting any dramas here.

@khamelboufeniche9854 2 жыл бұрын

Hello, the output that is not accessible with two pins surely allows the calibration or recalibration of the BMS Thank you for your videos, you always bring us a better knowledge of our facilities

@kswis 2 жыл бұрын

I've been using the jbd 4s 120 amp bms. Some poor soul took out the power pole a block away and the power was out at my neighborhood for almost 3 days. My house was the only house with lights on that didn't have a noisy ass generator humming outside all night like the guy two houses down. It was then the wife smiled and said "I'm glad your such a battery nerd" the poor bms was pegged at around 100 amps for the hole day. Still works great right now. So the bms is solid and I will be buying another

@OffGridGarageAustralia 2 жыл бұрын

Thanks for sharing, that's great!

@adon8672 2 жыл бұрын

I never knew they had less than 16s BMS. A link to the 4s and 8s?

@kswis 2 жыл бұрын

@@adon8672 there are TONZ of re-labled ones all over the net for cheap. I think overkill solar sells one as well

@teardowndan5364 2 жыл бұрын

Although 1R0 may intuitively sound like 1.0 ohm resistor, that is actually how SMD inductors large enough to have a value stamped on them are marked.

@OffGridGarageAustralia 2 жыл бұрын

Thank you.

@Poebbelmann 2 жыл бұрын

Jepp, should be a 1 uH inductor. Edit: It is Microhenry and not Millihenry.

@teardowndan5364 2 жыл бұрын

@@Poebbelmann 1uH, not mH. These high-current high-frequency SMD inductors are just a metal strip going straight through the ferrite beads glued around it. Effectively a half-turn torroidal choke squished down to a convenient SMD form factor.

@Poebbelmann 2 жыл бұрын

@@teardowndan5364 Yep, you are right!

@alexschulein7002 2 жыл бұрын

Hi Andy, i wouldn't change the BMS wires either. If it ever fails and you need to replace it you would need to alter the new BMS too, so keeping it standard improves the serviceability of your system. Oh i wouldn't worry about the resistance of your balance wires, it should measure the cell voltage when there is no load on the wire so the circuit should be high impedance when measuring. Only when the BMS is balancing it could influence the charge minorly to the cells. Even if the BMS measures the cells when wires are loaded the measurement should return to higher accuracy when the wires are no longer loaded with a balancing current.

@OffGridGarageAustralia 2 жыл бұрын

Thanks Alex. Exactly what I think too.

@mausball 2 жыл бұрын

Those FETs can only carry 180A if you can keep the junction at 25c. Because of the realities of physics, that's impossible, so they share the load through a large number of FETs to allow them to dissipate a realistic amount of power and not melt the junction. I use this same method professionally in designs that carry similar levels of current, but not at all in the same industry.

@electrojessy4270 2 жыл бұрын

👍 i was about so say this this commend need to have more likes

@OffGridGarageAustralia 2 жыл бұрын

Yes, that is correct. It says it in the specs. Th current capacity will go down with increase in temperature.

@christelting1359 Жыл бұрын

Don't forget the cable length when rating cables. It's all about the total resistance. Short lengths are perfectly acceptable with smaller gauge... just think about the traces on the PCB itself.

@christianvollmer167 2 жыл бұрын

Hey Andy, Der graue Block mit 1R0 beschriftet ist eine Induktivität ! Ich vermute mal, die ist für den Konverter der Supercaps Spannung. Und, bitte mess doch mal den Widerstand der Anschluss Leitung vom BMS. Ich glaube bei den kurzen Kabeln Spielt der Querschnitt keine Rolle. Grüsse . ..

@petleh82 2 жыл бұрын

Very good info as usual. I have a offgrid cabin, 5,8kw solar, and 800w wind turbine. So far 48v lead acid, and they are struggling now in the swedish winter. So i am always looking forward to your videos, to educate me before i make the lipo investment.. :-)

@OffGridGarageAustralia 2 жыл бұрын

Thanks Peter. How is this wind turbine going. From what I read, they are not that great and provide only little power unless it's really windy.

@petleh82 2 жыл бұрын

Off-Grid Garage Its 800 Chinese watts, at most i have been up to about 75w so far, and i have only had it for two weeks so far, and almost no wind at all yet..

@ssoffshore5111 2 жыл бұрын

@@petleh82 Now that you've had the wind power running for many months, what's your take on it?

@petleh82 2 жыл бұрын

@@ssoffshore5111 Its is now broken, the aluminum hub that holds the blades, the hexagon hole for the nut it have gotten completely round. Also when it did work it produced almost no power at all. It was a cheap ebay turbine. If you consider investing in one, i think you need to spend a bit more money on it or just go with extra solar panels..

@TheDigitalMermaid 2 жыл бұрын

Andy, you're too kind! See you Sunday! ^_^

@Shep5847 2 жыл бұрын

I bought two of those JBD BMS’s from Overkill last year and I got the ones with M6 connections and not wire leads. I prefer it over one with wires so I can make my wires the length I need for testing or playing. So far I’m happy with it but admittedly I haven’t tested to the extreme that you are testing them. I’m looking forward to the next video for sure… not that I’m not always looking forward to it. 😄

@OffGridGarageAustralia 2 жыл бұрын

Thank you. Yes, that would be the better solution if they provide just ring terminals with bolts to connect any wire to the BMS.

@bertschramm7285 2 жыл бұрын

You can leave the existing cables, cut them short, crimp them together, close to the board, and then crimp the cable size that you want for the proper size that you want, or solder instead of crimp, but all would be off the board

@OffGridGarageAustralia 2 жыл бұрын

I would rather crimp, I think, soldering short cables will melt the isolation and may also unsolder the cables on the busbar inside the case if they get hot enough...

@markmorris6357 2 жыл бұрын

Another great example of how to do it right. The smallest details matter!

@OffGridGarageAustralia 2 жыл бұрын

Thank you. Hence my videos are so long...

@egnegn123 2 жыл бұрын

I wouldn't use the busbar for connection, but instead cut the lugs of the cable and crimp the two wires on one side with the thicker wire on the other side with a crimpable cable connector . This gives a much better and reliable connection. And as mentioned below, silicon cables can handle much more current than regular cables that are limited to 70° C.

@OffGridGarageAustralia 2 жыл бұрын

I like the bus bars though in case I have to take the BMS out again.

@65bigfalconable 2 жыл бұрын

As always Andy.... entertaining and very helpful 👍

@OffGridGarageAustralia 2 жыл бұрын

Thanks 👍

@mjp0815 2 жыл бұрын

I am watching this while calibrating a SPAT at my favourite buzzbar.

@OffGridGarageAustralia 2 жыл бұрын

😁🍺

@john_in_phoenix 2 жыл бұрын

I would not replace the cables myself, but that is just because I have a LOT of experience soldering. Those would be quite the chore, and I am actually impressed by the job they did. Yes, you need a really intense heat source, not a regular soldering iron or even soldering gun. I personally would use a real busbar and not make multiple lugs on a single bolt.

@OffGridGarageAustralia 2 жыл бұрын

Thanks John.

@Juergen_Miessmer Жыл бұрын

Regarding the cables gave me the decition to buy the 200A version instead of 150A ,witch has 6 AWG cables, event though i need only around 120A. I measured the resistance beween the two 7AWG cables on the JKBMS. Its 0,5 mOhms or a bit less. As they are in series for messurement, but parallel in operation, the resistance in operation is around 0,125 mOhms. At 200A this gives a voltage drop of 25 mV, a power loss of 5W - 2,5 W per cable (on each side of the BMS). They should get warm, but not that much to be a problem for a silicone cable. If you're going to extend the cable anyway, its maybe a good idea to shorten the two 7 AWG cables in half to reduce the loss. I think it is a good decition to not solder other cables on the PCB.

@OffGridGarageAustralia Жыл бұрын

Thanks a lot for sharing these results, Juergen. I ended up, leaving the cables as they are. Maximum current is at around 80A for my setup for a few minutes only, between 30-40A is the nominal current I see through my BMSes. The cables are fine for the occasional peak power and don't really get that warm.

@MrJramirex 2 жыл бұрын

I used 2 soldering irons to remove the wires in the "Ciabatta" BMS and soldered my own PCB M6 terminals (what all those small holes are for) . Overkill solders those PCB terminals to their "Ciabatta" BMS too.

@olafschermann1592 7 ай бұрын

Maybe just shorten the cables and re-crimp them

@wayne8113 2 жыл бұрын

Thanks Andy

@OffGridGarageAustralia 2 жыл бұрын

No worries

@antoni_sk 2 жыл бұрын

Hi Andy, I wouldn't be afraid of those wires, I'd rather be afraid of the current capacity of those ring plugs. Imagine the area of the wires and the area of those ring plugs... Copper wire 10mm2 with quality insulations has current capacity min. 88A by 30°C

@kuhrd 2 жыл бұрын

For 200C tinned copper 7AWG cable in ambient tempertures at or below 40C you should be fine pulling 96.5 Amps per wire all day every day with open airflow. If you enclose it or bundle them thats when you start running into issues where you need to derate your cable. As a Fuse, each 7AWG cable is good for 562Amps before the copper will melt in open air. So for the ratings of the BMS and how short those cables are the ampacity is near perfect. It would be nice if they would upsize the wire to a much thicker gauge and provide longer cables but the Chinese suppliers don't work that way so we have what we have. The silicone cable they are using is not very expensive compared to the overall bill of materials and I wish they would offer longer cables for a few bucks more. Especially if they went the same way as the larger DALY BMSs that have the bolt on connections so you could attach 2/0 or 4/0 cable in any length you need to it but you can tell they are making them for the prebuilt battery market rather than the DIY market which I am sure is almost negligible in sales.

@OffGridGarageAustralia 2 жыл бұрын

Thanks for the info. I wonder if they would be willing to upgrade the BMS if requested. They could just add one or two more of these cables to each side. There is certainly enough room on the bus bar and PCB.

@juandilasagofficial 9 ай бұрын

The half of them is for charging transistor and the half is for discharge transistor

@luc_libv_verhaegen 2 жыл бұрын

Smashing! Sunday will be amazing indeed.

@OffGridGarageAustralia 2 жыл бұрын

Can't wait....

@jeb-zf4un 2 жыл бұрын

Just a comment to keep your stats up. Love your channel.

@OffGridGarageAustralia 2 жыл бұрын

Ha, thank you. So many comments to read through and reply...

@jondavidmcnabb 2 жыл бұрын

No bread was harmed in the making of this video.

@OffGridGarageAustralia 2 жыл бұрын

Absolutely not! 🥖🍞

@mfgxl 2 жыл бұрын

You are going to find, parallel strings of cells, is going to create many more videos that come to the conclusion that you should parallel cells into one series set up. One of my favorite statements, "they will see"

@OffGridGarageAustralia 2 жыл бұрын

We will see!

@danielardelian2 2 жыл бұрын

@@OffGridGarageAustralia "Professional" batteries that use parallel strings use a DC/DC bidirectional converter for each string to better isolate and manage the string. E.g. Tesla Megapack, Huawei LUNA2000 for residential applications, etc.

@ravnox3057 2 жыл бұрын

You could easily solder a third 10mm² cable on each side of the BMS, just spread it out to two times 5mm² on each side of the two cables that's already there :-) Just an idea.

@OffGridGarageAustralia 2 жыл бұрын

Yeah, many small cables in parallel could do the trick as well... With my 80A max, I think I leave it for now and see how we go.

@joevasquez1776 2 жыл бұрын

Jiabiada got a new 200 amp with bolt on terminals it's amazing. Just got it can't wait to hook it up

@OffGridGarageAustralia 2 жыл бұрын

All BMS should have bolts, that would be great.

@vaneay 2 жыл бұрын

the grey square is an inductor ;)

@olddigger7933 2 жыл бұрын

Maybe a BMS with protected studs would be easier for the manufacturer as well as the consumer instead of cables, especially if the studs or stud size holes could be a mounting option directly to a bar.

@OffGridGarageAustralia 2 жыл бұрын

That would be perfect, I agree.

@vaneay 2 жыл бұрын

you will need powerfull soldering iron if you proceed ( 60W to 80W ) with a massive tip to store heat and work quick on the wires.

@Sylvan_dB 2 жыл бұрын

60W to 80W is typical for a basic temperature controlled iron. I consider it an entry level as a professional tool, and it isn't near big enough to safely deal with that much thermal mass. My large soldering iron is 150W with about 8oz of copper tip, and it isn't big enough for many large jobs but it might handle that circuit board. I regularly consider adding a 300W iron. So far a torch works, but I wouldn't apply a torch directly to a circuit board like that!

@TrevorFraserAU 2 жыл бұрын

Thank you for sticking with bended!

@OffGridGarageAustralia 2 жыл бұрын

🤭

@henvan8737 2 жыл бұрын

You could cut the I/O cables and solder a longer 25 or 35mm cable to the existing ones. The current capacity is also a function of the cable length and heat specification. I believe the single nut lug is a bigger current carrying issue.

@OffGridGarageAustralia 2 жыл бұрын

The thicker 35mm wire will be sandwiched between the two thinner wires form the BMS. This will give a maximum contact are to the wires. With 80A, I'm not expecting any problems here.

@SylwerDragon 2 жыл бұрын

Hello Andy. I think i remember i did see similar claim on some component. But then ..there is mentioned that there is limit to package used..So you can't get 180A even if you wanted..case of that component will not be able handle it.. That is why so many have to be used..also there is so many of them because they can't make it same so they have to put few parallel to make it even as possible..

@OffGridGarageAustralia 2 жыл бұрын

It would need a lot of cooling. The 180A are related purely to the chip itself and its capability. The real world is however quite different. But 20 in parallel is good and allows only 10A per FET which does create almost no heat loss.

@loganv0410 2 жыл бұрын

And here I was thinking that the noise at 2:45 was your MOSFETs laughing at you.

@OffGridGarageAustralia 2 жыл бұрын

Hahaha, I thought I explain where it comes form, right? 😂

@trevortrevortsr2 2 жыл бұрын

Andy, had you thought of shortening the fly leads from the BMS and crimping on heavy ring terminals which could then be bolted individually to a piece of your chunky busbar - not only would that connect them electricly it would heat sink the shortened lenghs and stop any heat build up when leads take a high load - You could easily push 100 amps through each conductor and heat sinked short wire safely - the cooler and shorter you can keep them wires the more current they can carry - the chassis max rating is 89amp for 7AWG - think of them mosfetts - them little short legs well heat sinked carrying 180amps continous current ! Season Greetings from Wales UK

@OffGridGarageAustralia 2 жыл бұрын

Thanks Trev. That's not a bad idea actually...

@jforthewin8029 2 жыл бұрын

2 pins. Hidden. Probably for a fan if you changed the housing.

@pederb82 2 жыл бұрын

The price of angled lugs was the reason I recommended using bus bar scraps with a bolt hole in to make your angle. :) All Specialist parts like that is crazy expensive

@OffGridGarageAustralia 2 жыл бұрын

Yeah, totally overpriced... The bus bar link is a great alternative.

@stoptheirlies 2 жыл бұрын

Andy, you must use the SILICON cable chart for those cables, 7AWG Silicon, which has a much higher strand count can handle over 300 amps

@OffGridGarageAustralia 2 жыл бұрын

OK, thanks.

@excillisbank2611 2 жыл бұрын

Bonsoir, j'étais intrigué de savoir si vous alliez changé les câble du BMS ! ;-)) , mais les bus sont super et merci pour le lien d'achat.. bonne continuation et à dimanche.

@andreashanle9179 2 жыл бұрын

Dont worry too much about the BMS cable size. They are a bit small for the rated current but they are also quite short! Easiest way to reduce the resistance is to make them even shorter. Cable resistance is the specific resistance of the cable times the cable length.

@OffGridGarageAustralia 2 жыл бұрын

The length of the cable is not important in terms of current carrying capacity.

@andreashanle9179 2 жыл бұрын

@@OffGridGarageAustralia In principle correct, however, there is even a separate standard for bridge wires. What matters most is the type of installation and insulation. In this "ideal" case we have single wire in free air (optimal cooling) and silicone insulation (capable of high temperatures). A three phase cable installed in an insulated wall is a completely different can of worms.

@OffGridGarageAustralia 2 жыл бұрын

@@andreashanle9179 Yes, that is correct. The carrying capacity is dependent on the diameter of the cable, the type of insulation used and installation method.

@matthewknight5641 Жыл бұрын

I bet the un accessible pins are for a switch or maybe for some calibration from factory

@waynescheepers145 2 жыл бұрын

Don't Bother opening the Daly bms, they fill it with plastic to hide their crackpot designs. Can send photos if you like, very boring stripping them. Speaking of the Daly please label the box the Daly bms is in to - DC toy box

@OffGridGarageAustralia 2 жыл бұрын

Hahaha, great!

@Sylvan_dB 2 жыл бұрын

The cable rating is adequate - the 55 amps is not a hard limit, but a limit based on temperature rise (most likely) or on voltage drop. It sounds like a typical rating for 60C temperature operating limit for premise wiring. In your application... Obviously voltage drop will not be a factor for such short cables. You can compute a temperate rise. Assuming that is silicone insulation in free air (not another jacket or duct) it will tolerate much higher temperature than expected for premise wiring. U.S. standards were typically based on 60C operating temperature but usually 75C now and most premise wiring is rated for at least 90C - problem is finding breakers, etc for that temperature. Usually fixture/equipment wiring standards allow significantly more current even with PVC insulation because the wiring is contained in the equipment which is presumably designed to deal with the heat, and not in a wooden structure perhaps buried in insulation with several more wires. You could run some experiments if you have big enough loads, and see how hot a 10.5mm^2 cable gets at 100 amps. FWIW my tables show that at 30C ambient, a 6ga (13.3mm^2) single wire with PVC insulation can be loaded to 95 amps. The super caps are probably always in series, not parallel. 2.7v rating in parallel is completely inadequate. Oil doesn't conduct. Wet might but it takes a lot of wet for wood to conduct and your bench obviously is not wet! :)

@OffGridGarageAustralia 2 жыл бұрын

Thank you for your comment and information provided. The current carrying capacity is certainly dependent on the environment the cable or core is installed in.

@brucebugbee6604 2 жыл бұрын

On that JBD BMS if you need more wire ampacity, rather than replacing the existing wires just add an additional similarly sized wire to each side leaving the existing wires in place.

@OffGridGarageAustralia 2 жыл бұрын

I was thinking about this. I could have added two more 7AWG wires to each side and add the cut-outs in the case for them. I'll see how I go with the setup and how warm these wires actually get.

@mathewemy 2 жыл бұрын

Those wires will be "consided chassis Wiring" (in air and short). It will also be dependent on insulation type. AS3008.1.1-2017 gives you transmision info that I apply in DC design for telcom exchanges. Can't remember if it has the chassis info. Short answer they will fine at 200amps at that length. Says random person on the internet.

@solventtrapdotcom6676 2 жыл бұрын

There's an inductor directly adjacent to the 30F capacitor solder terminals.

@tryagain.k1821 Жыл бұрын

"Thin wires to BMS". Calculate or measure the R of the wires. Calculate heat generated in them at 100 A each. Estimate thermal properties of insulation and calculate surface temp of insulation. That tells you if the insulation melts. OR measure surface temp with IR spot meter at 100 A. Then calculate OR measure volt drop across cable. Then decide for yourself. You can't use normal cable current capability.

@RolandOfGileadOnYT 2 жыл бұрын

On my Jikong (JK-B2A8S20P), I have that 4 pin connector as well, it's marked as GPS, I have a 3 pin connector as well, marked as RS485. And then there's a 6 pin connector, marked in Chinese only.

@OffGridGarageAustralia 2 жыл бұрын

A GPS, ah, that's completely missing on mine. I doubt it connects via this 2-pin connector though...

@mendo3427 2 жыл бұрын

Jk bms , is a very nice unit. Bought mine also with the canbus adapter. NOT communicating with my cerbo gx victron product. Having hard time getting specs on canbus, just a notice to all

@firpofutbol 2 жыл бұрын

There is a driver for JK BMS to integrate into Cerbo GX but it doesn't use CAN, it uses RS485 I believe.

@danielardelian2 2 жыл бұрын

It would be very interesting to connect a voltmeter across the balancing supercapacitor terminals. The terminals seemed easily accessible on the back side, maybe with two alligator clips.

@OffGridGarageAustralia 2 жыл бұрын

I expect they use some sort of PWM for charging this?

@jameshancock 2 жыл бұрын

PS silicone wire at 200c rating and 7 gauge is 125 amps x 2 and it will handle even their 250 amp model no problem especially over that short distance. There isn’t a concern about the rating. I’d just get a 2 into 1 junction with 2 awg silicone on the other end and extend them and you’re fine.

@OffGridGarageAustralia 2 жыл бұрын

The cable length has nothing to do how much current a cable can carry though.

@jameshancock 2 жыл бұрын

@@OffGridGarageAustralia that’s not true. The longer the cable the more resistance and thus more heat and high voltage drop which depending on load will create a cascade feedback loop making the problem worse. That’s why all DC wire sizes are rated amps per meter. (AC for building codes is just dumbed down based on standard lengths in houses with safety fudge factor to a fixed amperage rating but the rule still applies which is why over 35 meters you have to apply derating to wires even for AC) There are a TON of calculators online that will do the math for you and calculate heat and voltage loss by distance. And as soon as the heat generated goes over the temp rating of the wire, you’re SOL because you’ll cause a fire. (Probably at some significant amperage above that rating but…) so yes, the shorter the wire the more amperage it can handle because there is less resistance and thus less heat. The purer the copper or copper versus aluminum wires also determines this rating and it is exactly that aluminum has more resistance than copper that it has a lower amp rating. It generates more heat and thus hits its ceiling faster. Either way 7 gauge silicone wire over 20 cm can easily handle 125 amps and since there are 2 it can handle 250 amps. That said if you went 50 meters with that you’d melt the wires because of the heat from resistance and this would have to size for the longer run. Which is exactly why the cables on these BMSes are short: to avoid having to size up the wires to account for derating. They are exactly the maximum length before you will get into line loss of voltage that is more significant to efficiency than the fets in the BMS.

@DPTech_workroom Жыл бұрын

Simple calculation 10mm2 copper ~ 100A can handle. You have 2 pcs of them (my BMS 150A - 7 AWG 2 cables; peak - 300A)

@jkrsecret 2 жыл бұрын

Don't forget that we need to have an accurate multimeter to if we need to calibrate it.

@alanb76 2 жыл бұрын

Spec sheets for devices like FETs give a lot of numbers that must not be taken out of context. For example the 180 amp max current at 25C case temperature means the case of the device must be cooled to 25C for the device to be able to handle that current, and there is no safety margin at that point. A reliable design must include margins and real world conditions and provide for cooling to actual ambient temperatures that are often well above 25C. So it takes a lot more devices and a good design to make a reliable product.

@OffGridGarageAustralia 2 жыл бұрын

That's correct. That's why they have like 20 FETs in parallel to spread the current among them and reduce heat.

@trevornelmes9331 2 жыл бұрын

At 15:36, that two pin connector might be an off switch connection. The BMS starts with the correct charge voltage detected, so it is not an ON switch, but it is possible that a short on those pins switches off the BMS? I would imagine they must test these BMSs when they are bare boards, and that means the capacitors might be still charged after the testing, and that might be a switch to switch off the BMS, and also to discharge the capacitors? Depending on how many test cycles they do, this would be needed.

@GabrieleBertaina 2 жыл бұрын

Andy, what about put positive and negative stickers on the bus bars? Just to be sure to be sure... to be sure... 😉

@OffGridGarageAustralia 2 жыл бұрын

Got something better ;)

@sarelwagner1099 2 жыл бұрын

Damp cloth on the area on the ends will prevent solder from melting, plus a big ass soldering iron with lots of thermal mass will solve the problem.

@anonhollmuller4032 Жыл бұрын

cables are short so i would get a connector an then increase diameterer. once i had tested how much current can flow tru a 0,6 mm square wire (230v ac!). i found 7 kw not even warm the 25m long cable (sorryly 7 do not massure the output voltage). The 3 x 2,5 kw heaters worked fine over serval weeks (around 4 months). with round 30....35 amps. The voltage drop was high....but like i say sorryly i do not read it. if from interrest i repeat and report ;)

@jamest.5001 2 жыл бұрын

If anything, just cut the bms cables short, and connect a larger cable to it, a 7gauge wire 2" long can handle a ton of current! Probably 200 amps, the cables are fine for most cases! "My opinion"

@OffGridGarageAustralia 2 жыл бұрын

Considering I'm pushing only 80A through this BMS, the cable is OK for that. Just wanted to make people aware that they may be a bit too thin for 200A continously.

@geerthaemelynck1126 2 жыл бұрын

Hi, that gray 1R0 at 11:18 is actually not a resistor but an inductor ! Google 1R0 coil...

@OffGridGarageAustralia 2 жыл бұрын

Ah right... thank you.

@NSWMods 2 жыл бұрын

Thank You To Andy For Teaching as What u Know To, Have a Great Day Mate BeSafe and Take Care

@OffGridGarageAustralia 2 жыл бұрын

Thanks you 😊

@MiguelSilva-mb6mb 2 жыл бұрын

I would not mess with the bms. In my case, my inverter suplyes 5500w, and the max discharge i would get at 48v is 114amps. Those wires can do those amps. And 114 is almost 0.5C. With 2 battery packs you would only pull 0.25C from each pack at 58amps from each pack.

@OffGridGarageAustralia 2 жыл бұрын

Yes, that was my trigger point as well. Even the cables may be undersized, it's not too important for me as my max load is ~80A at the moment.

@davidkettell6236 2 жыл бұрын

i should also point out that it is a relabeled JBD -SP10S009

@cfeigel 2 жыл бұрын

Is this correct? I'm curious what controller chip they use.

@guywhoknows 2 жыл бұрын

There max is 200w @25c so there probably operating around 150/120 watts. So around 3kw maximum through put. All chips have various specifications, you could have 600v 25amp but it may only provide 3amps at 600v and in working temps. You would need to look at the power curves and drop per oC. From the data sheet.

@giuseppevillella9445 2 жыл бұрын

Grazie i tuoi test ed esperimenti sono preziosi 👍🔋✅ è meglio confrontare diverse BMS bravo.

@mathewemy 2 жыл бұрын

and there is an inductor that square thing(ceramic inductor 1r0) at the end of the super caps. Small hence high frequency. But I could be wrong, it has happened many times.

@alsemi-back-up579 2 жыл бұрын

Great Job!!

@penandpike 2 жыл бұрын

I guess they rate it 200A because they assume that for this short length 200A is not a problem which could actually be true. of course the cable should be extended with larger one

@jamest.5001 2 жыл бұрын

It could use a pen discharge for balance, and measure the voltage when not discharging, to get accurate voltage readings, when carrying current, the wire resistance will show lower voltage, I'm thinking about getting a batrium with about 30kwh I'd like to have an amp or so balance current, but I. Could get it close manually, then let the bms handle it!! But I think we are over thinking it, and worrying over it too much, if it's within 1/10 volt, and you are not charging to max voltage, it should be great🍺 😃

@danielglang6312 2 жыл бұрын

replace the single connection bus bars with three connection bus bars. That way each ring terminal can be made more secure and not placed one upon another which would also keep the wires straighter with less effort bending to make a single connection.

@OffGridGarageAustralia 2 жыл бұрын

Yeah, I would need to connect them somehow then...

@danielglang6312 2 жыл бұрын

@@OffGridGarageAustralia One other possibility would be to remove the two ring terminals from the BMS and replacing them with a single larger ring terminal capable of holding both of the BMS wires. Perhaps also shortening the wires from the BMS before inserting into the single terminal thereby only having a very short fun of the lower capacity wires from the BMS.

@gregb1714 2 жыл бұрын

The covered bms connector might be a manufacturing test port and therefore not normally used.

@OffGridGarageAustralia 2 жыл бұрын

Or a switch to remote turn it on and off? It's only a two pin connector. Comms have usually at least three pins.

@upnorthandpersonal 2 жыл бұрын

@@OffGridGarageAustralia Did you happen to take a close-up high res picture of the PCB? I don't have a 200A version I can open right now, and the 100A version I opened a while ago doesn't have that connector. Would be nice to find out what it is for...

@ssoffshore5111 2 жыл бұрын

@@upnorthandpersonal Possibly for a different fan cooled case???

@kenwing6196 2 жыл бұрын

I dont think you should solder on the internal copper, use the existing cables, and if needed, solder external extension wires to them a few inches away from the BMS.. so you have made a good decision in my mind..

@OffGridGarageAustralia 2 жыл бұрын

Thanks Ken. It's not so much an issue for me as the max current I will pull from the batteries will be 80A at the moment, so 40A each battery bank. It was more making people aware of that issue...

@USA-GreedyMenOfNoIntegrity 2 жыл бұрын

Just use a 2ga crimp butt splice. Two 7 ga wires fit perfectly. I am also running 100A breakers.

@sorinnicolau6584 2 жыл бұрын

Nice job...well done...its gps ...out conection..sorry for my eng

@georgkeller1044 2 жыл бұрын

Hi there, you really are doing a great job explaining all the steps you go through with off grid in general and BMS in this case. Have heard of an Australien Company (NSW) who is selling a very interesting Batrium BMS? Would love to know what you think of this. I

@johthe 2 жыл бұрын

Hi! If the JK-BMS balance-lead resistans is too high it will stop, I do not remember the limit now. I tested it with breadboard and small not so good cables. /Johan

@OffGridGarageAustralia 2 жыл бұрын

Thanks for the advice, Johan!

@David_11111 2 жыл бұрын

yay

@1over137 Жыл бұрын

For every detail in a Mosfet datasheet that makes you go Ah ha! There are another 2 at least in the fine print that make you go.... Oh, ah. It's like you can buy 50W power resistors. Ever tried to put 50W through one? Don't. It will reach well over 200*C Similarly the mosfet current is theoretical. So is the resistance. They are all inter-related against various pin to pin voltages and temperature. For example the RDS(On) is quoted for a specific set of current and voltage parameters. The real fun starts with the graphs to lean the region within which you can achieve he maximum current and voltage through them without overloading the cooling system to the point you exceed where those values are valid and in the safe region. Then consider all the corner cases and failure modes. Then find out you can't get that part, so repeat for another and another and so on. I HATE mosfets. I HATE analouge electronics in general. It's all advanced maths, trig, calculus. I prefer the digital space.

@kevinmills5293 2 жыл бұрын

The resistivity of copper is 1.68e-8 OhmM which works out at about 0.168mV per cm of 7 gauge cable at 100A. With your mOhm meter, perhaps you could measure the resistance of the cables and calculate the voltage drop at 100A. I doubt it will be anything significant. Edit: I think I’m a factor of 10 out. The voltage drop would be 1.68mV.

@OffGridGarageAustralia 2 жыл бұрын

I'm not concerned about the actual voltage drop but more about the heat generated in these cables.

@kevinmills5293 2 жыл бұрын

@@OffGridGarageAustralia I calculate around 250mW (0.168mV x 15cm x 100A) for each cable with a total BMS current of 200A. You might just be able to detect a rise in temperature. Edit: I’m a factor of 10 out. Power dissipation would be 2.5W per cable which would make the cables noticeably warm.

@tjunkieu2b Жыл бұрын

@@kevinmills5293 would it then make sense and be relatively easy to shorten the 2 cables splicing a 70mm 2/0awg wire? With say 2cm length instead of 15 there should be 7x less heat, right? I am just about to install JK BMS with 160A breaker.

@marcoarpago 2 жыл бұрын

To me this last vieos are very interesting maybe most interesting

@OffGridGarageAustralia 2 жыл бұрын

Thanks for the feedback, Marco!

@kevangell-sale9090 2 жыл бұрын

Good evening its 19:11 uk time in Southern uk Kent I just like to say a big thank you. Iam in the proses of a battery build after self installing solar system. I am also watching a US site in Tex doing his own also. He is using a wooden box system. Also very dif to yours and mine but i did notice that he’s putting a thine protector between the cells in his build is of 16 cell in each Bach he has in total 3 x 16 batch that i know of i think he’s using the 3.5 volt cell and aim using the 3.2 volts with 304Ah so fare i have only got my first 16 battery’s, he was also putting the batters in a wooden clamp battery box he was clamping them all together, Is this needed as he stated the battery can expand when charged he’s using a fuse on each box he made all the boxes himself. And they look very good but his system is all floor lev an on rollers but i did notice. He first had the battery’s in par to charge the before he put them in ser. Does this have to happen all my cells before i put the BMS on

@OffGridGarageAustralia 2 жыл бұрын

Thanks Kev. I would not use any combustible material for housing a battery. I built my own battery box in a plastic crate which was OK at this time. from a safety standpoint, not recommended. There are certain regulations for housing batteries. Plastic or wood is not on the list of allowed material. In terms of compressing cells, I think we have discussed this already a while back in the videos I link here. My opinion is that compressing cells is not necessary as it causes more problems than it provides benefits or advantages. I leave a 2mm gab in between the cells so they can expand a bit if they need to. So far, I could not measure any contraction or compression in mine. kzfaq.info/get/bejne/a7plgb2jsMyUg58.html kzfaq.info/get/bejne/fMp0rJuTmt6biWw.html kzfaq.info/get/bejne/n9SpeLOW38fXdWg.html

@trevornelmes9331 2 жыл бұрын

At 9:23 you say they are 7AWG. Interesting. I have the B2A24S15P version, the 150A with 2A Balance model. So, the same as yours, except lower capacity rating, as yours is the 200A model. Mine has the same 7AWG cables. Not so much an issue at the lower rating. Also, mine does not have the lugs. The cable sheath is instead cut at half an inch (12.5mm) from the end and slid out a little, protecting the stripped cable ends, ready for lugs to be fitted. The cable run is only 4 inches (125mm), so resistance will be very low anyway, plus the strands are very fine and tinned (so called marine grade), so that will also keep the cables cooler.

@jamest.5001 2 жыл бұрын

As long as the balance leads are within a foot or so of each other, about anything goes, 18-24gauge , if you fuse it, just fuse to protect the wire, 2-5 amps fuse, shouldn't make much a difference..

@renekohli7675 2 жыл бұрын

Ich würde die Kabel austauschen. Querschnitt würde wohl reichen für diese Länge. Insgesamt wäre es aber wesentlich einfacher, längere Kabel zu verlegen. Wäre Schade um das schöne Layout Nicht mit Heissluft, sondern mit einem dicken Lötkolben. Ich vermute, dass die Kupferplatten nur an den Enden verlötet sind. Konnte es nicht genau erkennen. LG aus Zürich, HB9CAX, Dipl. El. Ing...

@richeagleton5285 2 жыл бұрын

Try an overkill solar BMS there the best made for medical equipment with 3 temp sensors vary smart. BMS look them up o love mine and I have a jk BMS to

@jameshancock 2 жыл бұрын

Likely sized so that they can hook them together which is supported.

@DanBurgaud 2 жыл бұрын

10:55 30F, 2.7V super capacitor. 11:05 what you are referring to is called "Flying Capacitor" technique, to get 2x voltage. How does JK measure current through it? I am not seeing any shunt resistor like those on Seplos, or QUCC.

@stephsoltesz6731 2 жыл бұрын

You say the BMS B & C wires are 7 AWG silicon which is actually rated for 100A ea so the pair should take 200A. Also asked the HankZor sales rep who confirmed that. I just did some quick conversion table checks and it seems that 2x7AWG (21.5mm2) = 4 AWG. But what size AWG are the harness wires ? 22ga or thicker. forgot to ask LOL. Pretty ridiculous they do not indicate the wire gauges in mm & AWG for the wires, which would certainly make ordering ring terminals easier.

@OffGridGarageAustralia 2 жыл бұрын

Under optimal conditions I can find tables which allow 73A going through a 7AWG cable. I would not trust what the sales rep tells you. They are sales persons, not technical. If they would have used 2x 4AWG, how much more would the BMS cost?

@stephsoltesz6731 2 жыл бұрын

@@OffGridGarageAustralia this is tinned braided silicone jacketed wire isn't it, not plain copper in silicone with tinned tips ? I didn't think it looked like just tips but could be wrong. There is current handling differences between the two to the best of my understanding.

@stephsoltesz6731 2 жыл бұрын

I should have also mentioned, I know better than to believe a rep, but I do read what they say.

@douglasmarquis3446 2 жыл бұрын

Andy , could you use a large butt connector to add length to the bms wires. You could get them big enough to use your crimper tool with heat shrink. Just cut off the ring terminal and install a butt connector , a longer length of wire and a new ring terminal.

@reneroman1421 2 жыл бұрын

The red cables of the JK BMS all have to be the same size?...I had to make some longer to be able to take them to the positives of the batteries...Will I have some kind of problem with the resistance of the cables?.. ..Thank you

@OffGridGarageAustralia 2 жыл бұрын

No, they don't need to be the same size or length. They are for voltage measurement, so length is not a problem. I have shortened some and extended others in my old battery box, no problem.

@MultiJamie12345 2 жыл бұрын

I ordered an 8s JK 200a BMS, and what I assume is the newer model is in a different case and doesn't come with wires. Instead it has 4 m6 female threads to bolt your own lugs to. It's more of an "open case" design, all seems similar except it seems to use 4 smaller capacitors instead of 2 large ones.

@upnorthandpersonal 2 жыл бұрын

Yeah, I saw that. Too bad they don't seem to have those in 16 cell versions, would like to test them.

@OffGridGarageAustralia 2 жыл бұрын

Yes, that is an upgrade only for the 8s version for some reason. Even it is the same 200A version as well as the 16s. I'll contact them and ask for a reason...

@monsieurd.6890 2 жыл бұрын

In fact you have to compare the cable section and the total section of the paths on the electronic board. In fact the cable is far more than the electronic paths ont the board so I think it is not a problem at all. I highly doubt the electronic board can handle 200A for a long time (8 hours ?) without dying. 200A !

@davidrogers5343 2 жыл бұрын

temp wire hookup for battery

@noelrufo1593 Жыл бұрын

Thanks uour channel. Fr.cebu.philippines

@jcreedy20 2 жыл бұрын

Why not just use some metal clamps to nip the bus bars into place whilst you solder the new cable on? That's what I would do. Place clamps as far from the solder points so there not sapping too much heat away from the point of soldering but also toward the surrounding components to keep them chilly. What gauge are the original cables out of curiosity, do they need replacing?? High strand silicone can handle about 20 - 25% more current than standard OFC of the same gauge. If that's 2 x 7 gauge high strand silicone??, it looks like silicone high strand, that should handle a fair whack of current!! More than the 65- 70 amps you think it does. I have used many hobby high strand cables, there very good!

@glencooke494 2 жыл бұрын

BENT Andy BENT !!!!!!!! Is it bended or bent? Bent is the past tense form of the verb bend, which means to make something straight become curved, or vice versa. Bended is an archaic form that has persisted in the idiom on bended knee but is nonstandard otherwise.

@OffGridGarageAustralia 2 жыл бұрын

It's actually angled. Not to mix up with angel.

@glencooke494 2 жыл бұрын

@@OffGridGarageAustralia Good on ya Andy love you content Have a great day!! from Vic

@cutlascutlas5830 Жыл бұрын

HELLO, JK BMS problem, not balancing due to high resistance in balance wires, JK-B2A25S60P

@davidkettell6236 2 жыл бұрын

Iam looking at my old overkill solar 100 amp 8s BMS and it has 2 bolt on 8 awg cables ,which could easily be upgraded ,which reminds me that i have to order a 16 s one from them.