BMS for motorcycle battery?

Anyone know of a BMS that would be suitable for use in a vehicle starter battery?

They want about $170 for a 4ah motorcycle battery and I just can't bring myself to shell out that kind of cash for a battery with so little capacity. I was thinking maybe 4 15ah headway cells in series would do the trick, or maybe 4 of the high discharge 8ah headways. I'm not opposed to the idea of lipo, but the BMS would have to be rock solid, as this thing will be mounted directly under my ass. Which brings me back to my main point, I need a bms that can handle being driven by an alternator.

I doubt my alternator will put out more than 30 amps max, but it would probably fluctuate pretty significantly depending on engine speed and draw from the lighting system. I'd need to sustain about 150 to 200 "cold cranking" amps for maybe 5 or 10 seconds when starting but my current draw probably won't be any more than 20ah constant. I don't need my capacity to be higher than about 6ah, but it certainly wouldn't hurt to be closer to 10.

What do you guys think, am I on the right track? Any suggestions?

I've used 4 headway 10Ah cells top balance on my gas motorcycle with great result.
Top balanced cells don't really need BMS and Lifepo4 cells are really safe.

No BMS, eh? So you're saying I should just manually top balance the cells and have something to disconnect the pack at low voltage? Still seems like I should have some over-charge protection for each of the cells since they're basically charging every time I get on the bike.

i would stick with a bms of some kind the voltages the bike can spike at are over the maximum charge voltage

Yeah, that's what I'm thinking. I mean, why NOT balance the cells every time you drive if you can? The problem I have at this point is finding a 4 channel bms that is rated for that short 150 to 200amp discharge peak. Charging should be good, since bms modules with a 30amp charge rate are plentiful (although I probably want some sort of additional current limiting so the batteries don't murder my alternator by constantly sucking up its max current), and continuous discharge is no problem since I'll rarely be pulling more than 20amps, but a high peak rating is a necessity for this application any way I look at it.

Indubitably said:

Yeah, that's what I'm thinking. I mean, why NOT balance the cells every time you drive if you can? The problem I have at this point is finding a 4 channel bms that is rated for that short 150 to 200amp discharge peak. Charging should be good, since bms modules with a 30amp charge rate are plentiful (although I probably want some sort of additional current limiting so the batteries don't murder my alternator by constantly sucking up its max current), and continuous discharge is no problem since I'll rarely be pulling more than 20amps, but a high peak rating is a necessity for this application any way I look at it.

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use the bms output to switch a relay that bypases the bms that way lvc and hvc will still work you might need a couple of diodes for the chargeing depending on what bms you use that way you just need a bms with the charge amps raiting its how i used my bms protected pack to jump start cars in the winter

There are 4s bms with 200a fets, and 400a that need a relay.
I have some 150a bms, but I don't think they go lower than 6s.
I'm researching for a high power 12v 600ah boat stereo system.

There are several on Flea-buy. a one,(I bought one of these in the 16s flavor. pricy but decent.) a two, a tree. just for starters. Yeah they are made in China, what isn't these days.

I've been running what are now 10yr old A123 M1 cells as my car battery for 3 years now, and only check balance every 4-6 months. I've only had to balance them out twice in that period. I use a 6p4s arrangement, but a couple of friends use 4p4s with similar results.

My car's voltage regulator limits charge voltage to 14.5V, which works out perfect.

No way I'd use Deadways up under the hood with all that heat. AFAIC only A123's are robust enough to be up for the task.