Battery’s

[expresso]

A BMS is then like a Fuse in the line

you match it the wire size - the BMS is matched to the Cell C rate and Cap. etc,

a too large BMS on a small low C rate is like having a too large fuse on the small cable - it will never blow but the wire will burn

thats what i am understanding from what your saying about the BMS


if thats correct then - i didnt know that - i always believed the BMS is capable of a certain rate and cant exceed that rate - but didnt think a lower rate would affect it this way -

now i know then

[Burgerman]

This is because a BMS only has one job. To protect the cells that a manufacturer is selling to a world full of imbeceils from being killed and returned as "faulty/failed"... So they all INSIST on a BMS being used. It a thing needed to protecttheir warranty for the ignorant masses to use lithium. Its not there for your needs, as you literally do not want or need what it does if you know what you are doing and esp in a powerchair. You do not want to be stuck in the middle of a road a night, or in the rain in winter miles from home.


As such fitting a BMS that allows more current to be withdrawn from a battery than the cells C rate allows is the same as not fitting one. Fitting a bigger BMS to the same low rate cells will kill them. So joe ebiker, then overloads the cells with his basic non current limiting "controller from cheap china" and sends them back because they lasted 3 days.

So you match the maximum BMS current to the cells maximum current rating, or preferably less if you are selling lead brick replacements to the frankly ignorant public. Or most of your sales wil be back in a week. As "faulty/wont hold a charge/wont charge/wont work/defective" etc.

So this is why you frequently see now batteries advertised as 100Ah, and 100A max BMS. And they are using smaller 1C cells. Ideally 2C cells to have some reserve for reliability reasons.

And you see some same GRP24 batteries advertised as STARTER battery. These are smaller in Ah, (physically bigger cells) but can do 300 to 1000Amp for starting engines. And use bigger higher C rated cells. Like 10 or 15C ones. And either a large Amp capacity BMS or the BMS is not in the power output circuit. It is bypassed.

[expresso]

that settles it then


everyone is shit out of luck if they cant DIY - ADD ON maybe the best option - with a BMS - then plug and play with dumb charger - ADD ON is less imitating to start off with -