[001] Jump-start car with 18V battery: How much current and voltage?

Рет қаралды 21,415

Күн бұрын

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I've seen lots of people jump start their cars with 18V lithium power tool batteries - and I've also seen all the comments descend into arguments about it being too much voltage for the car and too much current for the power tool battery. I've never seen anyone actually measure them, they all just throw around imaginary numbers to suit them.
In this video, I measure the current through the power tool battery and the voltage of the car battery whilst performing a jump start on my car. The batteries used were Milwaukee M18 5ah and 12ah.
USE MY RESULTS AND CONCLUSIONS AT YOUR OWN RISK!
Different cars, car batteries, 18v batteries, and jumper leads will yield different results and may damage your car, battery, and yourself.
00:00 Abstract
00:13 Background
00:36 Setup - type of car, conditions on the day, battery condition, batteries used
01:44 Results - 5Ah jump
02:57 Results - 12Ah jump
04:19 Results - Trickle charge
05:15 Conclusions - and all the graphs
References:
Lock your Hubs - • Tool Battery Car Jump ...
c01by25 - • Life hack drill batter...
Tales Taller - • Jumpstarting My Truck ...
Screws Nuts And Bolts - • Jump Starting Your Car...

Пікірлер: 123

@poprawa 10 ай бұрын

In Hyundai/Kia branded cars electronics in current models 17V is mostly in spec, but 18V crosses a line of setting up overvoltage DTCs and a have chance of breaking expensive things. In example of old Hyundai i10 / Kia Picanto large voltage fluctuations can reset immobilizer but not ECM or the other way around and that messes up memory - every key get's unregistered and only diagnostic equipment can register those again, also with freaking immo pin code needed to start at all.

@toolscientist 10 ай бұрын

Awesome info, thank you! I was hoping that someone that knew what they were talking about would find this video. In my graphs I get fairly big inductive spikes from failed starts. I guess they have capacitors to absorb those, or it's less sensitive to short spikes?

@frosty9595 10 ай бұрын

Sounds like a really poorly designed system if critical memory can be changed when it is not being programmed. Or perfect for a throwaway car.

@Ariccio123 10 ай бұрын

Jesus safety critical systems like this can't even stand 18v without resetting or damage?! That's comically bad. They should be able to eat at least twice the running voltage, like 30v or more...

@toolscientist Жыл бұрын

Apologies for this glorified powerpoint presentation. I filmed this nearly a year ago and have since replaced the car battery and sold the car, so I only had footage of the engine bay to work with. My next vid (testing the current in cordless power tools) has over an hour of footage to sort through, so I promise it will be better...maybe.

@BobHannent 10 ай бұрын

It's a good and informative video, this is my second video of yours I've watched and it's great value.

@revealingfacts4all 10 ай бұрын

automotive engineer here. 12v - 20v, 14 nominal is what we design for. In heavy equipment industry we design to 12-24v

@toolscientist 10 ай бұрын

Is that 20V forever, or 20V for a few hours? The pinned comment had some interesting info about Hyundai, and there lies the problem with making any conclusions - it's hard to test every car from every manufacturer. And then different health batteries, jumper leads (or cutlery!), etc. add even more variables.

@revealingfacts4all 10 ай бұрын

@@toolscientistyes, 20v forever and we also have conditions that suppliers of hardware have to meet such as surviving crank. My work is Ford Motor and GM for automotive and for heavy equipment, it's Case New Holland. In the heavy industry world, the requirements are a bit more stringent due to shock & vibe, use of power washers spraying down equipment so all our electrical connections have to be water resistant to a certain pressures. As an electrical guy I spend just as much time on environmental factors as I do electrical designs. All electrical components are typically spec'ed for a much wider temperature range and depending on the application, we have electrical designs to accomodate a standard known ISO25119 and ISO26262 (Functional Safety) where we have redundancy incorporated into the circuitry. (ok this is getting long) but suffice to say a lot goes into design and even more in testing & validating....

@anzicek 10 ай бұрын

Most cars are designed for "double jump start" there are SAE and ISO standards such as ISO 16750-2 and LV124 which stipulate 26V for 60 seconds be applied with no permanent effect on the electrical system. I have also had charging systems fail on vehicles and charge to more than 19V, in those cases some incandescent bulbs for brake lights and headlights were damaged, but that was the extent of the damage. Nice video, thanks for putting it together.

@toolscientist 10 ай бұрын

Very interesting. Any thoughts on the pinned comment about Hyundai/Kia giving electronics errors at 18V? I guess those standards are for the analogue electrical system and the electronics are much more sensitive?

@anzicek 10 ай бұрын

@@toolscientist Yes, I think both conditions can co-exist. Basically it is normal for DTCs to set above ~16-18V depending on manuf. and so forth, but those should not inhibit operation of the vehicle and should self clear if not present for several "drive cycles" It is common for automotive systems to flag this over-voltage behavior, but it should self correct if it was a jump start event, rather than persist if it is a regulation issue with the charging system. Additional info: Often the over voltage DTCs set for the purpose of disabling other diagnostics. There are diags that you do not want to run when voltage is above say 18V, for instance a solenoid valve or a seat heater coil over current diagnostic should not set because the supply voltage is too high, you want those to be "inhibited" when "T30" (battery voltage) is too high. So the T30 OV DTC would inhibit coil overcurrent DTCs. As an example.

@jagmarc 10 ай бұрын

There's just too many armchair experts and people working in the motor trade including manufacturers too saying "anything over normal battery voltage cause irrepairable damage blah blah" . Blame Hollywood movies, when a needle crosses a red line exactly 5 seconds all blows up.

@jagmarc 10 ай бұрын

A car that just stops after an alternator regulator failure isn't any good. 19 V for extended period is about right as the battery electrolyte by then has boiled away and or it's gassing the plates out of circuit

@CATA20034 10 ай бұрын

Wanted to post this comment, but I saw you already written it. Double battery test I recall is when you perform a jump-start from a 24V truck system. No failure should occur for at least 60s. For the old cars who have only a relay for the headlamps, this for sure will result in burned bulbs, I guess. The power-train will have no issues, only maybe some set DTC's.

@BorisDesmond Жыл бұрын

great to see someone actually made some proper measures when doing this. Amazing. Thank you.

@hugegamer5988 10 ай бұрын

The ability of the tool battery to push the car voltage higher is directly dependent on the state of the car battery. If the battery is dead, then it can have a high internal resistance and not be able to sink current allowing the tool battery to push the car close to 18V when the load is light like when not using the starter. If it’s in great shape, just low charge, you will be hard pressed to get it over 15V because it will want to sink several hundred amps first, on top of any loads like running a starter motor.

@bxyw 10 ай бұрын

A guy at work did this with his porsche cayenne and had no problems. When he told me I was surprised he didnt destroy any electronics.

@jmcgibbony 10 ай бұрын

Nice video mate, thanks for sharing your findings. I have a 2018 VW Transporter TDI450 with an aftermarket Bosch battery and if I leave to many accessories plugged in during the day my battery drops down to where it won't start the van. I have lost count of the number of times i have successfully jumped my van with my Milwaukee 18v 8Ah battery. No problems with the vehicle or battery... yet 😊

@FFcossag 10 ай бұрын

Excellent work, thank you for taking the time to do this! I was surprised at how well that worked - I was expecting the power tool battery to be driven significantly harder than your data shows, potentially endangering the internal fuse. Good to know that that might not be the case in a pinch!

@mojognome 10 ай бұрын

Live your style! The summary made me smile like a kid😀

@fuzz11111111 10 ай бұрын

I've started a car with a 3s 5ah RC car lipo, but I disconnected the flat battery first (so the lipo was only starting the car), and only reconnected the battery once car started.

@RRrrRRrrlandfin 7 ай бұрын

Solid quality content👌👍🏻 Thanks a lot!

@bobbg9041 10 ай бұрын

I wouldn't be surprised if Milwaukee Introduce a jump pack that uses 2 or 3 18 volt batteries to jump start your truck or can youve been off grid at the job all day with, just put in your batteries give it a few min to bring up the car batteries voltage and boom that truck you almost ran tottaly dead has just enough juice to crank over and start. The jump box also can be used as a charger for your batteries up to 4 at a time. Think about it your out on the farm working all day and your dome light drew down the trucks battery its 5 miles to get back to the barn. Pop in 2 3 4 batteries and wait for green light, crank start and drive back.

@TheBlairHouseProject 9 ай бұрын

And probably charge about $540 USD for it too. Their shit is pretty good but not worth that much more in my experience.

@NotEnoughKit 10 ай бұрын

Cool testing! Def worth subscribing!

@user-zd8wf3pl5i 8 ай бұрын

I love how scientific you made this video.

@erg0centric 10 ай бұрын

I used to start my car with two 7.2 Volt NiCad packs in series, SCR cells IIRC. Since then I have maintained my cars better. As a side note car was a Nissan Sentra with a teeny tiny gear drive starter.

@erg0centric 10 ай бұрын

Also, as an electronics professional I measured nothing and guessed.

@toolscientist 10 ай бұрын

If it smokes, it's broke. Otherwise it's all good!

@jagmarc 10 ай бұрын

Yeh! Go for it!

@slayerspam 11 ай бұрын

Cool freaking video man this is awesome!

@toolscientist 11 ай бұрын

Thanks, mate! I didn't think anyone would like this video as it's just looking at graphs, but it seems to be getting more attention in the last 2 weeks. Glad you liked it.

@MaverickBlue42 10 ай бұрын

@@toolscientist Donut media had a video, tiktok hacks or something like that showing somebody jumpstart a truck with a drill battery, so probably got more people searching about it

@lone_puppy3539 25 күн бұрын

This is great!

@TheBlairHouseProject 9 ай бұрын

Finally a real analysis. Nice work!

@toolscientist 9 ай бұрын

It's limited by my metres, so we're not really seeing what's happening during ignition. The results for before and after ignition will be pretty close, so I think it shows that the over-voltage isn't too bad. Hopefully someone with better gear does this test.

@TheBlairHouseProject 9 ай бұрын

@@toolscientist You vid a damn sight better than any other I found! You have the makings of a youtube star!

@ThriftyToolShed Жыл бұрын

I realky like your channel! The video information was well put together. The 12ah is a beast for sure. I have one on my bench right now having some issues. Hopefully I will have some troubleshooting info out soon on them. Its been an interesting look inside of the 12ah. I have seen enough here to be certain the 18650 cells would not take much of this, they give enough issues with smaller loads as it is. The 21700 will most likely take it just fine, especially 3P packs. I did find out however the the INR21700-40T1 cells do have an issue holding up under high discharge loads (capacity diminishes greatly). Samsungs data sheet seems to show the INR21700 40T3 (newer version) doesn't have that same issue. This 21V on the 12-15V system for me is just not worth the risk. Especially if the car battery is just barely too low to turn over. That is the most risk to me when the pack is full at 21V and the car just sit there with lights on etc. and now it can not quite get the engine fast enough to crank. Keep up the great videos!

@toolscientist Жыл бұрын

Thanks! I agree there's risks and I see both sides. I was happy to give it a crack on my 20yo car, but I'd be very hesitant to do it to my 4yo car. I mainly just wanted to put some real numbers out there to help the discussion

@ThriftyToolShed Жыл бұрын

@@toolscientist Absolutely!

@clems6989 10 ай бұрын

Good video, thanks..

@prestonprix1854 2 ай бұрын

Thank you for taking the time and testing that out. I found the information to be very helpful. But I would like for you to redo the video. And this time add a battery booster jumper box for comparison, Considering the cordless battery is taking the place of the jumper box. Essentially that's what it is a makeshift jumper box. You should take the two and compare them together like you just did. The jumper boxes instructions says for you to immediately disconnect the jumper box after the car is started, to prevent overcharging the battery and blowingl relays and sensors and whatnot. Once again thank you for taking the time out to showing us how it works it was a good video

@toolscientist 2 ай бұрын

Unfortunately I've sold this car and I'm not willing to do experiments on my new car as I need it.

@medman36 Жыл бұрын

Insightful

@garyradtke3252 10 ай бұрын

I have wondered why Milwaukee doesn't make a jump starter for it's M18 line or the MX Fuel line. M18 would be more reasonable even with 2 bats.

@toolscientist 10 ай бұрын

I think they've got a patent for one. Look up Doresoom tools, he occasionally does videos on new Milwaukee patents. I think his most recent one had a jump starter in it.

@dosgos 10 ай бұрын

@@toolscientist Such a great idea.

@dosstheboss100 11 ай бұрын

Very interesting I have a lot of dewalt batteries in both 12 and 20v I thought of converting my atvs to run on the 12v batteries but didn't know if it would work

@Demoralized88 10 ай бұрын

You easily could run Li-on cells in place of any 12v lead acid, provided they can crank it without overheating. The only real obstacle besides fitting it would be that you'd want to add a lithium charger off the alternator output instead of running it direct. Which could just be any 12v lithium charger, but still would require a little effort.

@qwertykeyboard5901 10 ай бұрын

I wonder how well many sealed lead acid batteries work as cranking batteries.

@fiftyoneindustries2 11 ай бұрын

Amazing Video

@toolscientist 11 ай бұрын

Thanks, mate. I actually thought this was my worst video as its just looking at graphs. Glad you liked it.

@dragan3290 10 ай бұрын

I did this with dewalt cordless 18 volt battery and my Toyota hilux with 10.5 volts at a current draw of 29 amps kicked over my v6 5VZFE engine in my hilux. The century battery only went to 14.5 volts. Imy nephew did the same on his maloo ute and it started quite quickly.

@toolscientist 10 ай бұрын

Awesome! Great to hear someone else thought to measure this. In every discussion I read on this it was all just people throwing theoretical numbers around. Sounds similar to my results with the 5ah of 33 amps and 15V. Maybe your battery was not quite fully charged?

@davewebster1627 10 ай бұрын

Can you do this for a hybrid, there are no cranking Amps

@Therealphantomzero 10 ай бұрын

Can you try using the 12v batteries instead I've had luck jumping a car with those so I'm curious to see what you get

@Tk3997 Жыл бұрын

Eh This will vary allot from car to car and case to case. I have straight up jumped my car (2 Liter 4 Cylinder) with what as probably at best a 4ah battery (it was from the cheapest ass drill from harbor freight that doesn't even give a rating on the battery), twice. I used to work nights while going to a trade school during the day and kept my tools in the trunk. So when I came out from work at 3 AM one day and found the car wouldn't turn over I got a no name drill battery and some multi-meter probes which I used to jam into the contacts, then clipped acutal jumper cables to the exposed banana plug of the probes and connected those to battery. There was enough juice still in the car battery to bring on the lights, but not turn over the motor, the drill battery easily jumped it (although it did overheat the probes pretty much instantly and start melting the plastic near the battery contacts a little). Then I forget to replace it and it ran low again a few days later and I had to do it a second time. There was zero damage to the car and the battery still worked afterward, I still own the car.

@toolscientist Жыл бұрын

Definitely. My aim was to at least give some sort of ballpark numbers. I've seen people claim that it will push the car up to 21V or that it will pull 400A from the tool battery, so I think I've somewhat disproved those extremes. In my case the car battery was very dead and wasn't even turning the instruments on, so that's why it needed the bigger battery to get it going.

@azuwan 10 ай бұрын

Can you have a look on using super capacitor as sole source or hybrid battery/super cap

@toolscientist 10 ай бұрын

Check out lasersaber: kzfaq.info/get/bejne/jrSdnruqzauYnGw.html

@jagmarc 10 ай бұрын

Correct me if I'm wrong the "7 V at beginning" car battery must had been contributing cranking current, since it seemed to be swallowing a fair current before start acting as a buffer. It only takes a fraction of one Amp hour to start an engine

@toolscientist 10 ай бұрын

Hard to tell. In the 12ah test (5:27) car battery starts at 7V and dips to 8V when cranking. So that would indicate that it was maybe still sinking current. It was getting 40A for 20s before that, so not sure where that would put the voltage. In the 5ah test (5:22) it takes 30A for 40s (but with 2 failed cranks) and settles back at 9.5V (although this fell back to 7V over the next 15min before I did the 12ah test). My feeling is that 144A is too low to start the car so the car battery must have been contributing, or my clamp meter gives wildly varying results during transients. I'd hope it does something sensible like giving the average or max/min (if the signal is obviously peaking) in each display update. I'm hoping that with more views, someone with a proper DAQ and 2 current clamps will repeat this test.

@jagmarc 10 ай бұрын

Hopefully someone repeat the tests but in meantime I can offer my own experience. I'd say the car battery was doing most of the work, and the energy it used came from the powertool battery. TYpically a completely discharged battery is capable start engine again after just a few minutes of couple amps charge. Only a fraction of an A.hr is used to start if engine primed. With leadacid battery, the majority of energy you'd put in comes back out again, if taken before it leaks away over time. So that means that '40A over 20s' energy had counted. Some of that first supplied energy though could had been used up 'repairing' a dead cell because 4-5V terminal voltage while cranking is a bit too low to start. A normal fully charged car battery V does dip down quite a lot while cranking, 8 or 9V isn't out the ordinary, I don't use clamp meters myself I prefer measuring millivoltage drop through a known resistance i.e. either end of a battery lead. 2 or 3 milliohms I think the jumper-lead cable were bit too high resistance 50 mohm.

@jaredj631 10 ай бұрын

I did this in a pinch once it works great

@arkfreebird2672 10 ай бұрын

Do this all the time!!!

@harleyhem3381 Жыл бұрын

Everything electrical in cars most of the time are designed for upto 24 volts.

@Demoralized88 10 ай бұрын

Most electrical circuits in decent products (i.e. cars) are usually rated to handle at least 2x nominal voltage - AC or DC. Every complex circuit these days has overvoltage and overcurrent protection often with self-resetting protections instead of fuses.

@Morphasella 10 ай бұрын

If I want to be good in this thing, What course should I take in university? Thank you.

@jancotolsma3782 10 ай бұрын

Nice

@Video-ee1dn Жыл бұрын

Well the measured currents and Voltages may highly depend on your car Battery and your Kickstarting leads. Maybe a good Idea to not use thick and high quality leads, or you may waste your 18V Battery. Especially with Batterys like the Makita LXT ones which desides at a certain point of abuse, that the Battery is now permanentely dead and may be not brought back into live. Even completely disconnecting the PCB and using new cells may not lead to unlock the Battery to further charging. As far as the cars electronics goes, Autotive rated semiconducters are super tough and may most likely even survive a kicksatart with a 24V truck Battery.

@toolscientist Жыл бұрын

Definitely. My car battery was quite old and deeply discharged, so it's an extreme case. The power tool battery is probably doing 80% of the work. EDIT: The last line of my comment is wrong, but leaving it there so people can learn. Thinner leads will have higher resistance, which will have more voltage across the leads and less across the car battery. It's essentially a 3 resistor circuit: li-ion resistance, jumper lead resistance, lead-acid resistance. Voltage drop across each resistor is proportional to value of resistor. So a bigger resistor will have more voltage drop. Therefore thinner leads with more resistance will drop more voltage and the car battery will see less voltage vs thick leads. THIS IS THE WRONG PART... Downside to thinner leads is that less current through power tool battery = more voltage at the car.

@giusepearturo 8 ай бұрын

make a 18650 or 21700 li-ion battery pack, replacing the car battery!!! that would be awesome, and maybe drive daily :) Great videos!!! Greetings from Colombia!

@toolscientist 8 ай бұрын

There's already some commercial options, but usually LiFePO4 prismatic cells rather than 18650/21700. More expensive, but longer cycle life than lead acid.

@giusepearturo 8 ай бұрын

@@toolscientist but your diy version with tools batteries would be awesome

@TranTek Жыл бұрын

Try using the 6.0 high output as it can take up to 50Amp per cell 2P - 100Amp

@toolscientist Жыл бұрын

On paper, the 12ah is more powerful and has less resistance. 12ah is 15.2mΩ*5/3 = 25.3mΩ, whereas 6ah is 11.6mΩ*5/2 = 29mΩ. But the Samsung 30T seems to be a lot tougher than the 40T, so the 6ah will handle the abuse better.

@TranTek Жыл бұрын

@@toolscientist yes i have not seen one really good bad beside people break the case. Torque Channel verified this Samsung 30T has way higher discharge rate, it rated at 30Amp but turns out that they can handle 50Amp where 40T struggle at 30Amp, i seen all kind of weird dead 12Ah batteries from shocking dead bank and some won’t charge properly, 8Ah has bunch of simply won’t hold charge, sagging

@poepybrown2151 10 ай бұрын

Well, charging the powertool batteries to 80% or 90% avoids having 21 Volts entering the car's electrical system, a more reasonable 18 or 19 Volts will be safer for the car.

@hugegamer5988 10 ай бұрын

The internal resistance of the battery is closely linked to how much current it can supply without the voltage dropping out. Electric motors like those used to start car engines are essentially a short circuit when stopped and by themselves will draw very very large currents on startup. A horsepower is 746 watts so a battery voltage of 12V under heavy load needs 62 amps minimum, more like 100 with real efficiency thrown in, starter motors can be 3-5 horsepower or more so you may be looking at 300 continuous amps while running and over 1200 on startup with an OEM motor. Good luck getting 1200 amps from a discount no name power tool battery.

@hugegamer5988 10 ай бұрын

Looks like data is being taken at around 2 readings per second when you need a proper scope or at least measurements on the milliseconds level.

@v12alpine 10 ай бұрын

My 5.9L cummins diesel draws insane current. Has two group 27 batteries, when they are low it takes two jump packs to get it to even turn slowly.

@toolscientist 10 ай бұрын

I did some tests with the meter in min/max mode and got similar numbers. Little 4-cyl engines don't need crazy currents. I think total starting current is ~200A, as seen from my plain start tests, so my guess is 144A from Li-ion and 30-60A from car battery. Also, this is not an alibaba battery. It's a genuine Milwaukee M18 battery, just the international version. They're using Samsung cells.

@hugegamer5988 10 ай бұрын

You must not live in a cold climate. A main reason to jumpstart here is they didn’t get a block heater and their engine oil has the consistency of hardened gorilla glue. You’ll need to double those numbers at a minimum, the hard part is the brownout when the motor is first engaged by the solenoid. But yes, 200A average for a tiny hot engine seems right, though you would benefit from a proper oscilloscope even if it’s just a repurposed low frequency audio input one as much of the interesting behavior happens on millisecond or faster time scales. You only need a short length of heavy gauge wire where you put a known current through and measure the voltage drop to get a respectable amperage measurement. @@toolscientist

@Darkipod Жыл бұрын

Very good video, question though, how did you get your measurements of current for the graph? Did you have some sort of DAQ system also in loop? Or just slowing down the video and watching what happened?

@toolscientist Жыл бұрын

Unfortunately just stepping through the video and reading the clamp meter display. So it's not the best data as it's only sampling at about 2-3Hz.

@Darkipod Жыл бұрын

@@toolscientist Thats what I was going to mention, if you did it that way your results are sort of all over the place, but you have to make due with what you have! Great video!

@jagmarc 10 ай бұрын

If just for starting and nothing else I reckon can just do away completely with a big heavy lead acid battery anyway and have instead in its place a sodacan size supercapacitor and three 18650s.

@toolscientist 10 ай бұрын

You should check out lasersaber. He's a mad-scientist that's been making car battery replacements with BIG capacitors. kzfaq.info/get/bejne/jrSdnruqzauYnGw.html

@jagmarc 10 ай бұрын

Yes, that's almost the idea, but he's mistakenly trying to replicate standard battery voltage and it shows. To go down that path would have to have a boost converter which I don't believe is possible yet. I was advocating capacitor engine start over a decade ago and I was told "it'd never work" so only a matter of time boost converter used, I'll be dead by then! @@toolscientist

@jagmarc 10 ай бұрын

By the way, there's easily enough energy in a couple of alkaline 'D' cells to start an engine. Could do it with today's tech, with a flywheel and dog clutch, driven up to speed with a tiny electric motor. Huge diesel engines were hand-started with a flywheel.

@toolscientist 10 ай бұрын

@jagmarc now you've got me thinking of silly ways to start a car. Like how long would it take a hamster in a wheel to charge up a supercap to start a car 😄

@jagmarc 10 ай бұрын

Or a solar panel as energy source to keep topped up. Capacitor is always going to give voltage trouble, it isn't a flywheel with momentum. A 'superinductor' be better .

@aussiegruber86 10 ай бұрын

How did you log this data, did you simply playback the video?

@toolscientist 10 ай бұрын

Yes, the poor man's datalogger. The transients are obviously a bit suspect.

@aussiegruber86 10 ай бұрын

@@toolscientist thanks for the quick reply, I do a lot of DAQ stuff for work and you had me looking hard lol….worked well so not complaints

@junianius 10 ай бұрын

Was always too afraid of a thermal runaway situation to actually attempt jumping a car.

@toolscientist 9 ай бұрын

The high-powered Li-ion cells are pretty safe. The only way to go wrong would be to hold the ignition on for several seconds.

@MADagain 9 ай бұрын

But will a 6amp battery workkkk??

@toolscientist 9 ай бұрын

The high-output 6ah will definitely work - it has similar power to the 12ah. If the car battery is only a bit flat, then even a 2ah might be able to give it enough of a boost to start. The 2ah can do about 50A whilst still holding 10 volts.

@donalexey 10 ай бұрын

This should be done with some supercap and a driver to get it to around 14-15 Volts and safely start the car without risk.

@toolscientist 10 ай бұрын

I've thought an array of 20 caps would work. Charge them up in 5s4p, disconnect, re-arrange busbars to make it 4s5p, then let it rip!

@donalexey 10 ай бұрын

@@toolscientist Why rearrange? Just stop charging at the desired voltage.

@jagmarc 10 ай бұрын

That's very interesting thing to try. But instead of switching caps between par/ser and connecting them to the regular 12V bus.... Isolate the starter circuit completely separate from the battery and instead have the solenoid contact feed by caps pre-charged to ~18V. The caps maintained by a few mA from a $2 boost converter fed by the regular 12V bus. Could do away with need altogether for a starting battery. If the caps are exhausted after a fail start they can be charged with a hand-crank for a few minutes! @@toolscientist

@mq1506 8 ай бұрын

I've jumped my car with an M12 battery, however it's a prius.

@OMGitzEDD 10 ай бұрын

i can confirm a 5AH dewalt battery will jump an opel/vauxhal

@dj_laundry_list 10 ай бұрын

I want to try this with the car battery disconnected, then disconnect the 18V battery immediately after startup just to see what happens

@toolscientist 10 ай бұрын

I'm sure someone has done this, just without the 18V part. You can start the car with the lead-acid and then disconnect the +ve terminal to get the same effect. Try searching for "car running without battery" or "disconnecting car battery while running". I think it'll work until you put a sudden electrical load on, like the cooling fan turning on or using the wipers. That might make the voltage from the alternator dip and stall the engine.

@dj_laundry_list 10 ай бұрын

@@toolscientist I've tried that before and driven it around and nothing happened. I guess I didn't try putting switching on a large load though. Anyway, I was mostly wondering how well the 18V would start the car without the additional current drain from the battery. I guess it's really not that much in terms of peak current

@toolscientist 10 ай бұрын

@@dj_laundry_list Ah, I see. I think the 12ah could just do it on a smaller car, especially with no jumper leads to add resistance. The 12ah dipped to 13V @ 140A, whilst the car battery was 8V, so the 12ah probably has another 80A left in it before it dips to 8V.

@dj_laundry_list 10 ай бұрын

@@toolscientistMakes sense, thanks for the explanation

@ejonesss 10 ай бұрын

18 to 20 volts into a car i hope you did not fry every electronics and total your car. you could have a case where the car battery is so old it does not have the resistance specs required to pull down the tool battery to a safe level. or a new car where you left the lights on or a faulty fan controller for the comfort controls and it drains the battery all the way down and holds the battery dead for a period of time to where the internal resistance may not be such to be able to pull down the tool battery and you could send the full 20 volts to the car and fry every electronics including the ecu (brain box) and the insurance could total the car. and repeatedly draining and charging the battery would ruin the battery very quickly allowing crude jumping to be even more damaging.

@toolscientist 10 ай бұрын

Agreed. The other possibility is someone using thinner and/or steel wire that means the voltage isn't pulled as low. Also some cars will be much more sensitive to this than others - I've heard some BMWs can't be jumped even with another car without frying stuff. It's not a good solution and a dedicated jump pack is better in every way. I just wanted to put some numbers to a question that previously only had speculation.

@villehietala9677 10 ай бұрын

@@toolscientistthis is the second time in these comments where I see you stating that thinner jump cables would make the voltage higher on the car. What's your thought process behind that? Tool battery won't dip as low as with thicker cables, but also that car battery won't jump as high. It's the jump cable that takes the hit and burns the voltage difference away, which would be a good thing, if trickle charging would be enough. Some years ago when I thought of that possibility to save my ass if my car battery dies, I calculated how long of a "jump lead" I should make from the stuff I most likely have in my car and came up with something like 10 meters of 0,5-0,8 mm2 copper signal cable to limit current to reasonable level, so that there's no way I could kill my makita batteries. Our basic electrical cables starting from 1,5mm2 would be too "good" for the job.

@toolscientist 10 ай бұрын

@@villehietala9677 good point. It's essentially a 3-resistor and 2 voltage source circuit. Increasing the jumper resistance will decrease the voltage across the other 2. I guess I was forgetting that pretty much all the voltage "gain" of the car battery is just from the resistance.

@toolscientist 10 ай бұрын

@villehietala9677 ok, the more I think about this the more I'm embarassed. I was clearly looking at the voltage of the Li-ion battery in isolation and not considering the effect of changing lead resistance on the whole circuit. Considering the whole circuit is one of the most basic concepts in electric circuits. Haha, how embarassing. Thank you for correcting me.