Dodgy BMS on 48v 16Ah battery?

[peasjam]

Hi,

First, thanks in advance for your patience. This is all very new to me so I will ask some very daft questions...
Also I've searched and a few previous questions seem to skirt around my issue but not really answer it directly, so here goes:

I have a brand new 48v 16Ah LiFePo4 battery from BMSBattery. I also have one of their 12'fet 500w controllers hooked up to a 500w BPM hub.

I have an issue that is preventing my kit working, I suspect it's the BMS in the battery but I'm not sure.

At both input and output battery terminals (unconnected) I have 48.3v.
Connected to the controller this drops to 5.1v Clearly this isn't enough to power the system, hence it not working.

Charger is outputting 58.5v. Green 'charged' LED is on and no amps being pulled from charger when connected to input terminals on battery. So, I assume then charger thinks battery is charged. I have left on for a 24 hour charge. When I first received the kit and put it on charge the LED changed between red/green for a few mins before settling on green.

I have confirmed that the motor works and the controller is wired up correctly by linking the charger to the battery and then connecting power to the controller, thereby keeping the voltage high via the charger. Charger providing a just over 2 amps during this test. Motor works, throttle is o.k. I have completed the controller learning process this way.

I'm not sure what voltage reading I should get from a fully charged 48v battery. It has been suggested that it might be flat, in which case would I be right in pointing the finger at the BMS mis-reporting to the charger?

Any help would be massively appreciated, I'm a bit stuck!

Thank you,
Matt.

(edit)

I should be looking at around 58v-59v reading from the terminals immediately after charge by the sounds of things. Charger seems able to provide juice as I've powered the system from it... convinced it's the BMS not allowing it to charge.

 

[dnmun]

the battery should charge up to 58V. you need to measure the cell voltage for each cell. record the voltages and keep track of them until you finally repair the pack. post up the voltages so we can offer some advice, and pictures.

 

[sangesf]

The quick answer is that the BMS is faulty..
It's not allowing the charger to charge the battery..
I've had that same problem with numerous BMSs..
It's a "safety" feature on the BMS...
The problem is, that this "safety feature" causes more problems then it's supposed to help with...
You need to have them send you a new TESTED BMS..
Just about every BMS I've had that failed had that exact problem..
If I knew how to fix it, I would...
ANYONE know how to "fix" this?
If so, I could get 2 "bad" BMSs working again.

Issues are..
1.) BMS (input) stops you from charging battery...
(would LOVE to know, how to fix that "issue")
2.) When you plug battery into controller, it's not charged up and you're hitting LVC, so the BMS "cuts power" to save the battery.

 

[peasjam]

Awesome, thank you for the replies. Confirmed what, after a good few hours of testing and learning a few basics about the kit that I'd begun to think myself.

I'm going to speak to BMSBattery first. Given that the battery is brand new and never used I'm a bit reluctant to start dismantling $400 (plus shipping) worth of kit just yet...
If they agree it's the BMS and send me a new one then I'll strip it and replace the unit.

Thank you.

Matt.

 

[neptronix]

This is typical of BMSbattery.

Read some threads that we have going on here:

http://endless-sphere.com/forums/se...t&sd=d&sr=posts&st=0&ch=300&t=0&submit=Search

I've seen so many complaints about their BMSes that i wonder if they have ever shipped one that works.

 

[peasjam]

Yes I'd been reading the bits about BMS, I knew delivery was very slow and that my expectations shouldn't be based on a western shopping experience so I was fairly relaxed about that. Also seems like the 'fake' BMS site has maybe caused some issues for them.

On the subject of the duff BMS, I got a quick response from them:

Thank you for your business! Are you charging with 900W changer? It will damage the BMS in the battery pack. You need to update the BMS to 30-60A version.

Does this sound reasonable? I'm now wondering if the 900W charger was a poor choice on my part if it would be a good idea to pick up something like the 400W version as well as replacing the BMS? I guess it's handy to have a spare charger anyway and if I'm getting stuff shipped...

I'm sort of irritated that they would supply one that wasn't suitable as I ordered everything together. I've not stripped the battery pack yet so I have no idea which BMS is in it.

 

[neptronix]

I like how they don't mention ANY details about the BMS in this pack.
Or anything about amp output of the pack.

Cheap... but what the hell are you getting

 

[peasjam]

I like how they don't mention ANY details about the BMS in this pack.
Or anything about amp output of the pack.

Cheap... but what the hell are you getting

Yep. Thing is it's only now, having had problems and therefore by necessity learning about it all, that I understand the significance of this.

Still. At least I know what the problem is, and I can fix it. Not looking forward to all the soldering though.

 

[neptronix]

Yep. Thing is it's only now, having had problems and therefore by necessity learning about it all, that I understand the significance of this.

Still. At least I know what the problem is, and I can fix it. Not looking forward to all the soldering though.

That's good to know. You automatically have a leg up on 90% of the people who own packs like this, so right on.

Welcome to the forums BTW.

 

[peasjam]

Welcome to the forums BTW.

Cheers!

It's good to learn new things. I only hope I can do it without accidentally costing myself too much...

 

[dogman dan]

Your battery is not charged. It could be the bms, and you could have multiple problems. But if the charger lights up, shows green, but won't charge the battery, that is a big fat red flag saying your don't have the charger connected to the battery.

So look for the broken wire, in the plug, or where the charger wires connect to the bms. You may be having the bms shut down because you just have a discharged battery.

 

[peasjam]

It could be the bms, and you could have multiple problems. But if the charger lights up, shows green, but won't charge the battery, that is a big fat red flag saying your don't have the charger connected to the battery.

Connection from charger to battery seems o.k as I can spin the motor by having the charger, battery and controller connected in sequence. All signs point to BMS issues not allowing the battery to charge either because it's simply faulty or I've killed it by plugging it into a charger that its not rated for. I'll have to strip the pack down and replace it.

 

[dnmun]

before you tear the pack apart, you need to identify what is wrong. all the opinions people may have do not actually tell you what is wrong.

you need to measure the voltage of each cell in the pack and record the voltages so we can give advice. until then it is all guessing. there is not likely anything wrong with the BMS or even the pack, yet.

 

[peasjam]

before you tear the pack apart, you need to identify what is wrong. all the opinions people may have do not actually tell you what is wrong.

you need to measure the voltage of each cell in the pack and record the voltages so we can give advice. until then it is all guessing. there is not likely anything wrong with the BMS or even the pack, yet.

Hey,

I have to take the coverings off to get at the cells and the BMS so I can check the individual cell voltages at the same time.

The controller and motor I have confirmed to be working as they should when they are supplied with sufficient power. The charger seems to be providing power as this is what I ran the motor/controller off.
This leaves me with the battery, either something with one or more of the cells or the BMS. It seems like the BMS is the more probable of the two, but I will check both.

 

[dnmun]

you can measure the voltages on the BMS where the sense wires connect.

 

[sangesf]

I would charge the battery for about an hour through the discharge leads, to get them cells up to 3.2v or so each, just to see if you can THEN charge through the input wires...
If not, then the BMS is screwed and you need to get a new one..
In the meantime, you can charge through the discharge wires, while watching cells voltages.. Once one of the cell groups reaches 3.6v, then you can ride for a little while..
I've done that many times...
You know the LVC works, since the BMS won't let you discharge at a certain point.

 

[peasjam]

So... turns out I have a dead cell.

15 of them read 3.2v, one of them 0.04v so way past attempting to bring back with a phone charger I think.

BMS might well be o.k after all.

Don't know how good BMSbattery are with replacing faulty stuff... guess I'm about to find out.

Matt.

 

[randomlight]

Hi Matt I was curious, did you contact bmsbattery about your bad cell? what was their response?
I am thinking about getting a battery from them myself. thanks

 

[bjosta]

I have a 36V 16Ah pack on it's way, it's the "rear rack" type aluminium housing. I'll let everyone know how that worked out.

 

[peasjam]

Hi Matt I was curious, did you contact bmsbattery about your bad cell? what was their response?
I am thinking about getting a battery from them myself. thanks

They happily accepted that I had a duff cell and had no issues with supplying a new one, the guy I spoke to had good English and was really pleasant and helpful.
I did, however, have to insist that they covered the cost of shipping. Initially they asked if they could send the cell with another customer's UK order and I organise the domestic leg myself which I politely declined. They then asked if I was going to cover shipping costs myself which I declined and pointed out that I had spent a substantial sum of money with them, supplied faulty goods etc. etc. After this there were no more issues, they gave me a tracking number a few days later (which didn't work) but as I was about to contact them for a new number it arrived at my office.

New cell fitted that night, repackaged the battery and everything seems to be working great.