Good point about using batteries that have a built in cut off, unfortunately all I have are Dewalt.

i love einhell batteries got ozito rebranded ones, cheap, use em for everything, even got one in my glovebox as a ghetto jumpstarter

This should be pinned

it's true and the small relay does drain the voltage.

I used these for Bluetooth amplifier speaker builds. I set the low voltage shut off at 17v so I’m able to charge the battery again also the lcd draws 25 milli amps if you don’t shut of the power that’s why I don’t set it to 15v Incase I forget to shut the radio off all day it won’t draw to much and damage the battery I have used this almost everyday for a work radio on a construction site for 6 months and hasn’t failed it’s in a plastic ammo box it doesn’t get hot at all and I would recommend mounting it on some abs plastic with stand-offs

Ya it drains 25milli amps with the led on so if you have a 20vdc battery 16.5-17 vdc would be a safe zone in case you don’t shut it off I would like to figure out to put a small buzzer on it when it gets low sometimes when I’m working it’s nice to know when to put a fresh battery on a 5amp dewalt battery will last me about 7-8 hours of run time on a single battery running to 17vdc running them down to nothing 15.5 has given me problems in the past like not charging

Great to know. Thank you for sharing!

Did you wire both batteries to the one voltage protector?

@@PaigeSaucedo both batteries in series together for a 36v nominal system. Low voltage cutoff is somewhere around 32 if I remember.

you will need a DC Buck device for this, they are readily available on ebay for low current applications

We appreciate your time, longer comments are always welcome.

Don’t go past 16.5 min voltage Incase you don’t shut off the power to the battery the lcd will drain the battery until it’s no good

​@jimcatanzaro7808 so you're saying the device which is supposed to save the battery will actually drain the battery?

just hold both buttons down then you press one to go up or the other to go down and wait for it to stop

it fits way better if you cut the pcb corners

According to the comments from the mfg most of these boards will hold the settings no problem.

Yes, you would want to use a 12V battery rather than the 18V and then set the low voltage cut-off to 9.3 volts rather than 15.3 volts shown in the video. Although he has already given a good explanation in the video, I will try to go into a little more detail. Nominal voltage is the default, resting voltage of a battery pack. This is how the battery industry has decided to discuss and compare batteries. Nominal voltage for a lipo is 3.7 volts per cell and a fully charged lipo battery has 4.2 volts per cell. Examples are...nominal voltage of a 2 cell lipo is 7.4 volts but its charged state is 8.4 volts. Nominal voltage for a 3 cell lipo is 11.1 volts but fully charged is 12.6 volts. This is why the advertised difference between Milwaukee 18V and Dewalt 20V while in fact, they both have a 5 cell battery. 5 cell=18.5 Nominal voltage and 21 volts fully charged. Low voltage cut-off for a lipo battery is 3 volts per cell. As a precaution, most people like to stay a little higher than that to avoid a dead cell. Buy a 12 V battery and follow the same instructions from this video with but change the low voltage cutoff to 9.3 volts or higher. Some things, like the DC motor shown in the video are safe with slightly higher voltage increase. The result will be the motor spinning at a higher RPM. However, your GPS is will probably end up in smoke if you wire it up to the bigger battery. Hope that helps.

Depends on the cell chemistry, assuming lithium ion cells which are typically rated for 3.7v that means 10 cells in series will make about ~36 volt pack. Li-ions can be safely discharged to 3.0v so simply cutoff at 30v but its better for the cell life to have more buffer like 3.3v * 10 series = 33v cutoff. In the video he sets the cutoff at 15.3v so divided by 5 series = 3.03v minimum per cell which is going for as much runtime as possible with a tiny buffer

@@kwitmeh3 its weird that you can only take .7 volts from those batteries before risking damage! there's so much power left in them. Now i understand why some of my devices still crank with the 3.7 and some shut down, the latter must have the safety shut off built into the device.

you dont need to they have everything built in

No, but you should have both batteries fully charged

buy batteries and put them in the case! or do what i do, everytime someone breaks a rechargeable vacuum, laptop ,bubble gun or anything else that takes the super common 3.7 volt lithium battery , you tear it apart and save those batteries LOL i have at least 20 of those things ready for random projects.

Don't parallel two lithium batteries unless they're permanently connected and charged/discharged together. If they're "hot swappable" and you accidentally have one at full charge and the other at near empty you can easily overcurrent them as one charges the other. Bang!

do Milwaukee packs have a bms?

@@Fatcode1 no they dont. Same as dewalt. BMS is built into their tools not batteries.

Some brands need to have the tool telling the battery when it has to cut off. Therefore most likely your(or my) application/project wasn't maybe built that way. I have Bosch 18V packs ans use them to power synthesizers and small PA set and I can say the protection does not activate while I am just connecting my audio devices to + and - terminals of the battery pack. This circuitry is highly recommended for any DIY projects.