BMS that can measure temperature?

[Rohan]

I met someone who said he was in the process of purchasing an older boat that has been upgraded to lithium batteries. I asked him how are they set up so the alternator doesn't burn out - and he said that it has the latest lithium batteries with a BMS that can respond to alternator temperature. Does that actually exist?


That didn't sound right to me. I can understand a BMS that would mimic a LA battery to the alternator, although I haven't heard of that either.

[smac999]

No. The external alt regulator would do it.

[hjohnson]

Pretty sure they’re conflating two things. Yes, a BMS should be monitoring battery temperature to ensure it’s not being charged when below freezing, not overheating. The REC ABMS I have does this, and it actually came into play this past winter when we had a deep cold snap (-15 for over a week). My battery dropped below freezing, and the BMS set the current limit for the battery to 0A. But as long as the battery temperature is above 0C and below about 50C, it doesn’t matter (much).

The alternator this is completely different matter, there you want to drive the alternator as hard as possible without overheating it. My wakespeed regulator has a temperature probe bolted to the back of the alternator (on the diode pack) so that it doesn’t burn it out. It also pays attention to the battery messages from the BMS. If I didn’t have an integrated system, it would also want a temperature sensor on the battery so that it can charge it safely. But in reality, the bms says “aim for 13.8V, at up to 120A” and then also sends the current voltage and current, and the Wakespeed tries to hit those targets.