Protecting LifeBluePO4 Lithium Batteries
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The batteries we’re protecting: I chose 2 LifeBlue 100 amp batteries in parallel. We chose 2 in parallel so that we can get a 200-amp discharge current. I chose LifeBlue’s over Battleborns because of the really impressive warranty and the SmartConnect internal Bluetooth app. I wanted to be able to see what was “going on inside” and cross-check that with the external Battery Monitor so that I could track the decreasing capacity over time. I think this will be really important over time.
I do like that the BattleBorns have built-in temperature protection. Unfortunately, I have to build that part in myself w/ these batteries. Ultimately though, I figured the warranty and BlueTooth app were harder to recreate than the thermal protection though. I know there are GBS and Winston Lithium kits out there, but I really wanted to explore this “drop in” frontier that’s happening. I expect that’s what these things are going to look like 5–10 years from now, so skipped the “build your own BMS entirely” science project. Mad props to people that bite that off, but I wanted to focus my energy elsewhere.
Anyway… I’ll stop rationalizing the decision and get on to how to protect these batteries.
Long story short, I’m protecting against overcharging using a Xantrex LinkPro Battery Monitor connected to a Blue Sea Remote Battery Switch: It’s not challenging tough to wire them both up per the provided instructions. I’m using the Low Battery Alarm Settings as detailed in the LinkPro Owner’s Manual. One needs to set up the System Properties appropriately. I set the S(tate)-O(f)-C(harge) alarm settings at really high and tight settings in order to test the system… like to turn on at 97% and turn off at 98%. I will switch this to 50% and 90% once I get the kinks all worked out. The documents on the “Dry Alarm contact terminals” were a touch sparse. I didn’t understand that it was necessary to provide one (either) side with 12v and that the other would then be the alarm signal. Once this was understood it was trivial to connect that signal to the appropriate one on the R(emote) B(attery) S(witch)… it was the brown wire for my model. This will close the RBS in response to the batteries discharging down to a prescribed level mentioned above. Then, it will be necessary to open the RBS when the batteries charge up to a certain level. The signal for this will be the inverse of the alarm signal. I’m not quite sure how best to invert the signal, but I figure it’s something simple… just an inverter or not gate or something.
