Good and Reliable Bms

Does anyone here knows where to get a reliable 72v bms I'm done with the Signalabs I've been through four of them in the last two months the Signalabs wouldn't even let me go on full throttle without just completely just shutting off and one red light stays on indefinitely afterwards if possible a link would help keep in mind i only run a 40amp controller anyway so that bms just sucks big time!

When I look in the mirror I see the only BMS I trust not to be a Battery Murdering System.

i think we asked already what was wrong with your old BMS but never heard a reply from you. i think the claim of 4 bad 72V v2.5 signalabs is new. i would still like to know what the voltage is on the cell with the led that stays lit. i doubt if your current had anything to do with the shutoff. more likely it was unbalanced, imo.

darkshirikens said:

Does anyone here knows where to get a reliable 72v bms I'm done with the Signalabs I've been through four of them in the last two months the Signalabs wouldn't even let me go on full throttle without just completely just shutting off and one red light stays on indefinitely afterwards if possible a link would help keep in mind i only run a 40amp controller anyway so that bms just sucks big time!

Click to expand...

I've lost faith in Signalabs as well, stupid charging FETs melting whilst charging.

@Dnmun, yes ive mentioned my bms before in a recent thread but it wasn't mine but the voltage is 3.28 for that cell so its at nominal voltage for headway cells which can be 3.2v-3.65v ,I've been through quite a few of them and they olny act up when i go an try to do full throttle and shut off on me and then i get the red light of death lol.

@John in CR ,LOL i believe what you said cause the bms just not working out for me but i think, i'll try out some others before i rule it out completely though.

@Spacey , After this point in time i don't want anymore signalabs I'm done.

I understand that this thread is not about the cells, but rather the BMS, but I would like to ask some questions about the cells. If you prefer to start a separate thread about them for this, I can split out any posts about them to a separate thread, and leave the first post open for you to place the problem and any existing troubleshooting data into.


Is that low cell 3.28V while under load, or just resting? If it's not been measured while under load, you shoudl check that, because if you get the same cell faulting on each of four BMSs, it's highly unlikely to be a BMS failure.

What are all the other cell voltages? If they are all significantly higher than that one, it is likely that that cell is causing your problems, or at least contributing to them.

Did you ever try bringing up the low cell with a single-cell charger or current-limited adjustable voltage supply?

I have been building up the Peter Perkins BMS system. it's by no means plug and play (you have to order the boards from peter, then find the various lists of parts, and order and solder them together) but it looks like it will work well when it's done. i haven't finished mine yet. i just ordered the microcontrollers and programmer i need for it.

if you could diagnose the pack to determine at what voltage that channel with the led is turning on then we could send you a shunt transistor, the little SOT27 part, from a scrap board to replace yours and maybe the led will turn off then the channel will balance then, so you don't have the BMS shutting it down when you draw a large current.

i suspect the charge FETs burn up because they don't like the high voltage and current so maybe go to the 4110, but the output FETs are 3205 anyway so maybe replace them with 4110s if needed, but if you want we can send you the shunt transistor for that channel from a scrap board.

signalab has a 5&10 fet 48v bms and might have a 10 fet 72v ? Or is this the one your are having all the trouble with, The white sense wire plug is the same. I read alot of headway low cell balance problems, must lower the power.

darkshirikens,

My pile of broken BMS’s is five deep.

Do your self a favor and charge and balance your headway pack with a Hyperion 1420I charger.

Break your 72v pack down into two 36v packs for charging and series them together for discharge.

Don’t discharge your pack more than 80% and you will be trouble free without the headache of a BMS.



Barry

Thank you to everyone who replied to this thread !!!

@ Amberwolf, The cells basically all rest at 3.28/29 i wish i could test them under load but at this time i dont even have the means to do so i dont even have a cycle analyst yet lol . Also the thing is i haven't even did 3 miles on the pack when the bms decides to act up and when i return home the pack is almost the same except a few hundredths of the points shaved off and i can understand that they batteries can sag under high loads but if i go just barely under half throttle it should have that kind of affect on the cell that lights up or them bms to cause it to crash on a 40a controller,I have a single cell charger that i use when i have other cells that just laying around till i build the other battery pack I'm making i has one cell that needed a charge and that's about all i needed to use it for

@ Isaac_Alaska, If i have the money and knowledge i would go a similar route you have but money to break stuff till i get it working is not of yet in the budget

@999zip999, Not even my original ping pack didn't have this problem wish i still had the bms but the bms i have is a 30/60a and my controller is only 40a !

@ Dnmun, how do i check that channel for the knowledge of doing it but as far as soldering i dont know how much heat that board can take and i a bit of a novice when it comes to soldering on a bms but wires and connectors i can do without problems if i can remember how to check the mosfets i will do so later today.


@ Barry, i wil try some more bms options before i run without one cause everything isn't built the same .

you can analyze the pack by charging it up to 3.65V on each channel and then discharging it into a load on a bench test. keep track of the voltages as you charge it up and when the charge stops because of one cell rising to 3.9V then drain some charge off that cell with a power resistor to get the pack to continue charging, and do that until all the cells reach 3.65v and then discharge the pack into a load like a heater or light bank until one cell reaches 2.1V. this is the capacity of your pack.

if you have cell with the led on all the time, then that implies that the shunt transistor is shunting current around the cell before the cell has charged up so that cell has no charge left and causes the BMS to shut down when it detects LVC on that channel when you throttle up to high current and the voltage drop on that cell added to the low voltage from inadequate charge causes it to see LVC.

this what everyone has to do first to start figuring out why their pack is shutting off. it is not just a matter of opinion or guessing, you just gotta go evaluate it to figure out what to fix. or you can buy a new one and throw this one away.

@ DNMUN, before each ride i checked all the voltages at each individual cell and it ranged from 3.31 -3.32 that's where the main confusion was i constantly check the voltage before each ride even when i had lead acid batteries just in case i had to top them off before i left my house to go to work , The cell that is lit is 3.31 that's its resting voltage.

i'm not familiar with the BMS you're using, but it's very possible that the voltage of the cell drops a lot under load, but floats back to 3.31 when you remove the load. maybe the BMS is remembering that that cell went low and staying lit? if this is true it would do the same thing on charging i think, reaching a high cutoff voltage before the rest of the pack did

Thanks to everyone who wrote in this thread. Since this was written i went with a different bms and i haven't had one single problem those Signalabs bms i'm done with them they have some real problems with quality control or just using bad components or cheap components and other issues that need to be rectified!

So which BMS did you go with??

I went with the XJI 72v 50/100a bms from Headway Headquarters and not one single problem!
The Signalabs i had some used to break as soon as i added the B- wire to finish the circuit or when i went to ride full throttle it completely shutdown before i got anywhere near 30 amps and it was a Signalab 72v 30/60a bms they used to be a good bms but now they are totally used it seems to me now i hope Signalab get their stuff together !!!

have got the peter perkins BMS almost completely set up. was a bit of a learning curve but it's actually coming together very nicely now, it is capable of monitoring voltage, current, temperature, speed, time, energy used, power being consumed, and total distance/ trip distance. very very nice system and extremely affordable, probably the most expensive part was buying picBasic Pro in order to be able to customize the software to our exact system.

highly recommended for anyone that isn't afraid of doing a little software work

the bms slave boards are maybe a little bigger than most people would fit on an e-bike, but new smaller boards are being developed right now