![]() It looks like they may provide at least some rudimentary form of protection from low voltage, as well as other considerations (apparently they can do brushed DC too). One option I'm currently evaluating is the VESC line of controllers. So it looks like rudimentary emulation of this protection would require somehow monitoring voltage in real-time (or reverse engineering whatever protocol Milwaukee uses) and reacting appropriately in your device's electronics.įWIW, I've found that the DIY electric skateboard and large RC communities (also high current applications) seem to take a similar approach and use "charge-only bms" in their systems design (though it appears to be at a much lower level of sophistication). Though it appears to go against the vast majority of advice regarding battery and power systems design/construction that I've come across online. After lots of thought it seems like a reasonable decision to me, especially given the price/availability of high-current protection circuits (at least that I've managed to find). It seems like Milwaukee isn't alone in this design decision, and that the majority of tool makers have chosen this design. However, the system as a whole provides regulation/protection through constant communication between the tool and battery, and it's the tool's responsibility to monitor battery conditions and adjust or cutoff as necessary.ĭoes this align with what you've learned? Where Milwaukee batteries provide a direct connection to the cells with no inline regulation or protection. Obviously the 20A breaker would limit these to low-power applications, but is there something else that makes this a bad idea for low-ish power applications?įrom my understanding, Milwaukee achieves "safe high current discharge" through the combination of both the tool and battery. ![]() So ultimately, my questions are: Is it possible to actually use a BMS like the one from the third link below as just a voltage cutoff by connecting only the positive and negative leads to the BMS, or does it need to detect voltage at each cell to function? If I can't use a BMS like that, is there a similar low voltage protection circuit some internet hero could link to that works with an 18v (5s) power tool battery thank can handle 30-50 A continuously? I can't seem to find one myself, but even a hint to a better place to look other than Ebay or Amazon would be great.Īfter doing a bit of learning about how a BMS works, I've learned that I can not use them how I was thinking.Ĭould you elaborate on this? I'm in a similar situation, and just purchased 2 of these to use m18 batteries for a number of projects/prototypes from robotics to kids ride-ons (go karts). That is part of the whole appeal to me for using them as experimental power sources. I probably wasn't clear before, but I would really like to keep the power tool batteries intact, and not tear them apart for the cells. However, I don't understand enough about BMS' to be sure it would work. I was told to look into a 5s BMS (third link below). ![]() I was looking to find something that has that low voltage cut off to prevent damaging the battery, but has a much higher amperage. I've been using some programmable low voltage cut off circuits I found on Amazon (second link below) but with a 10 A continuous, and a 20 A fuse, it wouldn't be hard for me to wreck those circuits. My problem is, they have absolutely no low voltage cut off built into the battery, only the tools. I'm currently using the Milwaukee M18 batteries which can easily supply more than 20 amps for several minutes at a time. I've started doing silly things like powering inverters off of my power tool batteries, like the Ryobi 150 Watt Inverter (first link below). Hello, I've been using my power tool batteries for many miscellaneous projects during quarantine, and I've hit a knowledge wall I can't seem to get around.
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