So it begins...... Battery spot welder

[sternwake]

Building the 10s3p esk8 enclosure hit some snags. wjth the mold, forcing a two stage figerglass layup, but then i used the poor mans vacuum bag technique, with the wrong plastic, which then bonded to the epoxy instead of peeling off easiky and aLlowing that second layup during the chemical bond window.

Now i'll have to sand it before that second layup, and hope i can get all the wrong clear plastic bits off.
i spent about 2 minutes trying to remove the wrong plastic before having to walk away.

The JST connectors already arrived, ordered on ebay, delivered by amazon prime. The 10 amp dc to dc booster which can exceed 42v, also arrived in an amazon prime envelope, but via usps, and i only got an update this AM saying it shipped.


The Lipo battery and the little voltage monitoring device i got for it, is quite interesting comparing individual cell voltages whike charging, under load, and at rest. ive on ever charged all three together.

the JST plugs allow a 'hobby' charger to chaRge one individuL cell.
with 12v lead acid there is no way to easily discern individual cell voltage, and when a battery staRts behaving badly the answer is to abusively overcharge 5 cells, hoping that 6th one catches up and 'equalizes'


With Esk8, the BMS is basically wired as charge only, unless they have buck converters to use 12v led lights, and then only the buck converters and charger leads are wired to the BMS, the esc gets power right from battery and has its own LVD protection.

Reading the esk8 forums, i think some of the pros believe the BMS, for sure the smart bluetooth bms but also the dumb bmss too, is always actively balance charging each individual cell group.

Watching Andy, from Offgrid garage, a german guy living in australia, who does extensive bms testing, ahows even the smart ones dont realky balance all that well, and when they do, it is with tiny currents, bleeding off the top cells or charging the lowest with as little as 0.02amps.

The BMS might not even attempot to apply any balancing current until the cells get to very high states of charge, and those who onky ever charge to 4.1v, can easily have parallel packs way out of balance.


I think I m going to wire uo my bms for charge only and this means a balance wire for every series connection, for the bms, bjt im also going to wire up two 6 wire jst plugs, so i can monitor each individual parallel pa kmof cells and drain or charge them individually.

a smart BMS would monitor voltage of each parallel pack of cells, display nicely on the phone, but what about proper top balancing.
when does it occur?
what starting voltage?
with how much current?
and if uktra tiny currents, will one need to hold battery at 4.2v per cell for days to get low parLlel packs up inline?

If i charge to only 4.1vpc will my dumb daly bms even attempt to balance?

Ignorance is bliss, but i think the bms's are kften thought if as taking care of everytbing, but i reLity onky stop over temperature, over or under voktage charging or discharging.

I do intend to make a 10s3p battery with $$ 21700s and a smart BMS in the future, but i also believe i will have a separate JST connector so i can charge or discharge individual cell groups and not hooe and pray the bms is doing so on its own.