This is practically enough to ditch an entire BMS manufacturer.
This should absolutely be part of the manufacturer’s QC process prior to shipping them, and, if not, then they are a terrible BMS manufacturer and in need of replacement.
Brian i’ve seen multiple of any bms fail. This is tinfoil hat logic. QC isnt flawless.
First time I got a dud from Bestech I never bought or used another BMS from them ever again, and no other company is different.
This is like a fire extinguisher that shoots confetti instead of carbon dioxide.
Evan, a BMS is a safety device, and children’s lives can depend on it not being shitty, and being tested prior to shipping, even if that costs an extra $0.10 off their bottom line.
FWIW, i’ve used a LOT of these bms and never had a ‘dud’
Given that at least 2 batteries from the same builder have suffered the same fate, i’d say it has something to do with the settings that have been applied.
My best guess is that the bms were set to always balance, which is a bad idea unless used under close supervision to balance out a pack with a high delta
Are you running any BMS then? By that logic my experience is alone should be enough to scare you off with this logic. I had my own dead daly BMS that got super hot when charging at 2 amps and I’ve seen plenty of LLT BMS acting up
Sounds like we need a new player that prioritizes safety
I have no fuckin clue what brand this BMS is, I used to think it was BesTech years back, but I’d just call it a generic anymore. This style/model exists for 10s-13s to my knowledge, & maybe higher.
This BMS does not fuck up. If you manage to fuck it up or kill a battery with it. You should quite simply not be building or even touching batteries in esk8
In a past life I would say start by conformal coating it, but that’s just overkill anymore tbh.
So:
Fkn solder on short flexible leads w/16-18awg silicone wire to B- & C or P/whatever the fuck the solder pads are denoted as
Terminate those leads with 3.5mm bullets
Do a nice wrap in kapton tape of everything
Then do a nice wrap of fish paper
Slap some fuckin adhesive Velcro on it
Boom you have a nice, modular, un-dick-upable bee ehm ess.
This is all completely unsolicited advice but holy sheeeet too many “my BMS entirely rekt my hundreds of dollars to thousands of dollars battery” posts on the forum anymore. Don’t use a smart BMS unless you have a genuine understanding of how they work.
Personally, I’ve been waiting for the FlexiBMS Lite or w/e it’s called, will be using dumdum bms’s that have never had issues sitting connected & dormant for 2 years at one point, until FlexiBMS is in full production. Unfortunately all of Chinas manufacturing industry seems as if it’s about to get completely bent over & railed very hard in the ass in the coming weeks & months - actually, I think it’s happening as we speak. So, electrical/chip supply chains are once again going to be completely fucked, & we will probably not have a reliable source of good smart BMSs any time soon.
p.s.
If you use a BesTech D596
You deserve the high speeds faceplant coming your way.
I only say that because I also recommend wearing full safety gear at all times in esk8, full face DOT or w/e approved helmet included
So have your nice protected crash, & then throw away your D596/other dogshit discharge BMS.
even with that setting, it still has a cutoff at which it stops balancing, it defaults to something like 4.1v/cell
i really need to get at those settings.
both of these were delivered at storage charge, around the same time, somewhere around 3.75/cell. so they started low, and sat longer than anyone else ever lets them. so it’s possible the drain from the BMS/bluetooth is just more than anyone expects? but it takes a long time for that to show.
I would only expect the battery to drain if for whatever reason the bluetooth module was left enabled. Seems odd that that would happen on 2 batteries, as one device can only be connected to one battery at a time.
It’s an odd situation, i’ve left the same bms attached to batteries for over a year with no significant drain, i feel as if there is something out of the ordinary in this situation
My LLT also discharges the battery if left connected. I left my 12S5P P42A at 3.5V per cell and checked on it about half an year later… It was 2.6V per cell. That was a close call
that’s a good observation.
yah…
damn. that’s a good and discouraging observation.
I have also seen significant drain on my 12s4p p42a pack with a ltt smart bms. I don’t still have the with bms numbers but it was noticeable after 2 weeks. After removing the bms self discharge is insignificant many months later.
Always check your packs at least once a month.
I was able to power on the BMS, by feeding it ≥16.4v on the first and last balance leads.
These are the configs. They look reasonable to me.
Theories put out so far:
| # | Theory |
|---|---|
| 1 | bms+bluetooth modules drains a decent bit, and over a year it could kill 725wh battery |
| 2 | bad settings in BMS config cause it to drain unusually fast. |
| 3 | Some BMSes are duds and drain unusually fast. |
| 4 | bad wiring by battery manufacturer. |
Regarding Theory #1
rough math suggests the bms would have to consume 0.082 watts to fully drain the capacity of the battery. 725wh/365/24 then idk how much further to drain it to zero. but doesn’t seem impossible.
Agreed…
I worked it from the capacity angle and an average of about 1.3mA of current draw would drain a 16Ah pack to 2.5V/cell in 18 months. Not much longer to get to zero volts.
Pretty easy to have a bit more than 1.3mA of quiescent current with a BMS + BT module.
Also if you leave the app on in the background with it connected tor the battery I would imagine the drain would be more. (Blue light comes on)
Could be a case that whenever you’re near the battery it connects and the Bluetooth, light comes on and it drains.
I’m a big fan of Neptune bms’s. Small form factor and they have their own power switch, just turn it off when in storage, no Bluetooth power drain issues, just remember to switch it off.
Down side is that the app is only available on android.
And it’s 4 times the price.
i never connected to it. but it did most of it’s sitting with @DEEIF. I don’t think he connected to it either. but he can confirm.
but I agree the active connection seems like it would draw a decent amount more than the idle state.
