Cheap 48/20 BMS all fall down go Boom. ANN041-13S-20A-02N22-0804BXX
- Thread starter mickkl
- Start date
JackFlorey
100 kW
Those are burned up top-balance resistors. Replacing them will probably not solve the problem. The problem is likely:
-One dead cell; it hits max voltage right away and the balancers try (futiley) to balance it
-A shorted balancer transistor; keeps that balancer always on
-A bad comparator, such that it always thinks that cell is high
In any case you have to solve that problem before replacing those resistors.
-One dead cell; it hits max voltage right away and the balancers try (futiley) to balance it
-A shorted balancer transistor; keeps that balancer always on
-A bad comparator, such that it always thinks that cell is high
In any case you have to solve that problem before replacing those resistors.
No worries thanks. I need to get a new multimeter and check. I blew the last one up, made magic smoke. Used 10amp hole not 20amp. Actually blew the lead out of the hole, quite exciting. Dont worry was on another project.
With my limited skills I will buy another BMS, get someone who claims to be able to solder, to swap it over and see what happens.
Is a silverfish job, worth trying to fix by swapping the BMS or a cell or two.
Batteries refuse to come down in price.
With my limited skills I will buy another BMS, get someone who claims to be able to solder, to swap it over and see what happens.
Is a silverfish job, worth trying to fix by swapping the BMS or a cell or two.
Batteries refuse to come down in price.
That kind of damage happens regardless of amp setting if you connect the wires across a voltage source (like the + and - of some battery or power supply).
The amp setting and wiring can only be used in series with the current flow of whatever you're trying to measure.
I would be, too, since most of those appear to be fires waiting to happen, based on the ad copy and what we've seen here when people post disassembly and test threads.
I was thinking of getting a few of then for the 3rd wheel trailer, be less likely to die if they are a few feet away from me as opposed to under my ass. Not much has changed in 20 years. Yes can build a pack, with join the dots apart from soldering a few wires.
There is a knowledge gap, somewhere between join the dots and soldering.
Ive been trying to work out how an Amazon $150 battery becomes a $500 battery when its put in a case that costs 20 bucks.
There is a knowledge gap, somewhere between join the dots and soldering.
Ive been trying to work out how an Amazon $150 battery becomes a $500 battery when its put in a case that costs 20 bucks.
doesn't the bms have a connector for balance wires? Then you could just swap the board without soldering anything (except of two main power wires).
And anyway, i'd check the voltage on every section of the battery - looks like the resistors were burnt during charging (when trying to discharge a section) and it's on one section only - i'd suspect this section is faulty.
BTW @amberwolf do you consider $150 BMS to be too cheap to be usable? Or too expensive to risk destroying it when connecting? I'd say it's quite expensive - $15 is the cheap one.
And anyway, i'd check the voltage on every section of the battery - looks like the resistors were burnt during charging (when trying to discharge a section) and it's on one section only - i'd suspect this section is faulty.
BTW @amberwolf do you consider $150 BMS to be too cheap to be usable? Or too expensive to risk destroying it when connecting? I'd say it's quite expensive - $15 is the cheap one.
Last edited:
docw009
10 MW
Did you wire the balance connector backwards? That's what the input circuits look like when that happens?
Generally I'd guess that a $150 BMS is *probably* good, but that depends on the design of it's power-control system (FETs or contactor) and whether it can reliably disconnect cells from a load under every condition that could occur, in all the various system designs it might be used in, and the firmware design that determines when that power control system is activated.
But I expect that the device referred to by the OP as "$150 bare bones blue 48/20 off of Amazon" is a 48v 20Ah
lol blue-heatshrinked battery from one of the many firebomb-special companies that build the things out of assorted forms of garbage cells, rather than a BMS.As we've seen here in various threads, they can be bulit from grade-z "new" cells, recycled garbage scrapped "new" cells, or even random salvaged cells from discarded damaged / worn out batteries of all kinds. Sometimes they spend the money to rewrap and recap them to hide what htey are, sometimes they dont' even bother with anything more than the blue main pack covering.
They may even include a BMS with a balance function to keep the thing operational for a few cycles (assuming it gets left on the charger long enough, which could be days or weeks for the not very good ones...but I would guess most of them don't have even that, so they cannot rebalance and get worse and worse every cycle. The worst ones don't even have a functional BMS (broken, defective, incorrect design or wiring / assembly, etc), and so don't have protection against overcharging or overdischarging the worst cells in there, and those are the worst risk of fire.
Just make sure you test the cells at least for voltage to be sure they are all identical before you do anything with the battery. If the group associated with the burned balance resistors has been drained down too far, you should replace those cells before continuing.
Otherwise this pack could be as much of a fire risk as the new one possibly is.
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