BATTERY PROBLEMS

[MARK???]

Greetings one & all. I'm new to this so be kind please. I have a A2b Metro with an almost dead main tube battery. 8-10 Km max with pedaling. I bought a second hand Lithium battery from Ebay that is supposed to be for a Golden Motor 36V 12Ah thats done 300 cycles. When I hooked it in to the rear battery circuit the bike took off then cut out. I assumed that 12Ah won't work with the A2B metro controller. But strangely it seemed to work going down hill without cutting out. I remembered that I have a 36V 12Ah lead acid battery so I hooked that in to the circuit & the bike goes fine up hill & down dale. Does anyone know what the problem is ???. Have I been sold a lemon battery ??? I checked the charge at 39.7 V but I dont know the Amps. Also if this question is going to a single person how do I post it for general inquiry. Thanks MARK???


(moderator edit: Mark, I merged all your posts and other people's responses from the different threads into your troubleshooting thread so all info about this can be in one place for people to see and help you better. )

 

[deepfraught]

Hi Mark, this is to a thread for all to see so you're fine there.

It sounds like all things being equal you've isolated the new/used battery being the problem.

Reading 39V charged, I'm used to seeing 41V+ from charged 36V bike batteries, so you may have a bad cell or more that are killing the packs ability to deliver load, and it's sagging to low voltage cut-out.

Used batteries in packs that can't have bad cells easily replaced are something to watch out for.

 

[MARK???]

Thanks for the response deepfraught. Can you tell me if I discharge the battery then recharge it could that do anything positive or should I get out the screwdrivers ???. MARK???.

 

[deepfraught]

Mark try posting the info you have here in the general forum with topic something like "Help troubleshooting Goldenmotor 36V battery".
http://endless-sphere.com/forums/viewforum.php?f=3

Someone who tinkers with batteries may be able to help.

When I've looked into the packs I have, the cells have been spot welded and usually the effort of repairing a used pack doesn't seem likely to pay off for success by my hand, or if successful much better life/performance confidently into the future versus new packs.

 

[MARK???]

GOLDEN MOTOR 36V BATTERY PROBLEMS. I bought a second hand 36V 12Ah Golden Motor battery to use on a A2B Metro as the back up or B Battery. However when I accelerate the battery cuts out. I have been advised that there might be an un-ballanced cell in the battery. The person I bought it from told me that it had been through 300 cycles. I no-longer have any reason to trust this as he doesn't return my calls. The Voltage reeds as 39.7 V fully charged. I intend to discharge the battery & re-charge it again. P.S the battery works just fine going down hill ???. MARK???

 

[d8veh]

39.7v fully charged sounds like much too low. You'll need to open the case to find the problem so that you can get to the BMS to measure the individual cell voltages. You won't be able to do anything from the outside.There's normally a multi-pin connector there.You can check the cell voltages with one probe on the negative (0v) main battery output and each of the pins on the multi-pin connector. Post them here, and then someone will be able to advise you how to proceed.

 

[wesnewell]

The reason it works fine going downhill is because there's not much load on it. Uphill there' a high load which causes one or more cells to drop below LVC. Assuming it's a 12s lifepo4 pack, fully charged should be 42V minimum. Could just be out of balance bad, Leave it on the charger for a day or more and see if the voltage goes up.

 

[dnmun]

39V is not only not charged but there is a reason for it to not charge.

put the battery on the charger and measure the cell voltage while charging for each cell and post them up here.

 

[dogman dan]

Too bad you didn't know the market value of a battery pack with 300 cycles is zero dollars.

I Would bet that inside, you have at least one cell with half normal capacity or less. It sags like mad under load, then that trips the bms shutting off the whole battery.

You could take it apart and mess with stuff, but I'd do it for the educational purpose, rather than expect to fix it.

If your charger is only putting out 39v, that could be part of the problem. Should be about 42 at least I think.

 

[MARK???]

Thank's for the responses I expect i'll get better at doing this & get to know all of you better over time. I hope. Anyway I de-boxed the cells & put them on a multimeter. They range in charge from 3 X 39.3V 2 X 39.6V 3 X 39.7V @ 1 X 4.10V so there is a range of charging differential of around 0.9 Volts. The cells are putt together in a 3 x 3 x 3 x 1 cell configuration and going by left to right / top to bottom by each mini cell pack the Voltages are. 39.8V - 39.2V - 40.1V in cell pack 1 39.7V - 39.6V - 39.7V in cell pack 2 39.7V - 39.3V - 39.6V in cell pack 3 & on it's own a 39.3V cell. I hope that this helps in show you the cell sequence OK. How do you draw a picture in an email anyway ???. I'll have to work out posting photos soon then. Any further advice would be great. Still no word from the B#####D that sold me this lemon. I was wondering if the charger may be the problem & how do I test that ???, also does that mean that each cell is 12 Ah ???. MARK???.

 

[MARK???]

I still don't know how this all works because I'm re typing this because my first attempt went to another place. I hope that this one does better. Anyway I De-boxed the cell packs which are in a 3 X 3 X 3 X 1 cell configuration. Going top to bottom per cell pack the left to right the voltage measured 3.98V - 3.92V - 4.10V X 3.97V - 3.96V - 3.97V X 3.97V - 3.93V - 3.96V X 3.93V cells. If you did find the other posting I put the decimal point in the wrong place. Does this mean that each cell is 12Ah & how do I check if it's the charger that's the problem ???. THANK'S MARK???.

 

[d8veh]

Those results mean that the battery should be fairly healthy, but your one high cell is preventing the others from getting fully charged. You need to discharge it down to the same voltage as the others. I have a special charger to do mine, but you could use anything that uses 3.5v to 6v like a torch bulb or toy car motor. You need to keep checking it to get to the exact voltage of 3.97v. It should go down fairly uniformly after an initial faster dip, so you should be able to estimate when it'll get there after a couple of checks.

The above procedure will get a bit more capacity in your battery, but I don't think it will solve the cutting out. The BMS probably has a limit of 20 or 25 amps. Do you know the max current that your controller will try and take from it? I suspect more than what the BMS can give.

 

[MARK???]

Do I have to disconnect the 4.1 V cell from the others in the pack first & what about the 39.2 - 39.3 voltage cells ???. MARK???.

 

[dogman dan]

No.

Some pics would help. If the battery has a bms, it might be that all you need to do is plug into the charger, and allow a few days for the bms to balance the pack.

Or, you could rig a turn signal light bulb to two wires, and use that to drain a bit of energy from the high cell, then plug back into the charger to fill all of them to the desired full charge voltage.

Not sure what chemistry you have, so not sure whether you should be charging each cell to 4.1, or 3.65v.

10 cell configuration implies not lifepo4, so my guess is that fully charged would be around 4.1v.

What's your charger output? Should be 41v right?

Even if you get them fully charged and balanced, they can still be junk. If they sag like crazy from fully charged and balanced, it means some cells are way too high in internal resistance, as happens when they are worn out and have no capacity. I think you will find that you are still screwed, but taking it apart and confirming why is great educational activity. Next time, you will know how to test a used battery before you plunk down cash.

 

[fechter]

If the pack sat around for a long time without being used, it could get out of balance. Each time you charge it, the BMS should restore a bit of the balance (wimpy BMS). Repeated charging and very shallow discharge may bring it back closer to balance. If you have the pack out, it would be possible to manually balance by charging each cell group individually with a 4.2v charger or with a current limited power supply.

End of charge voltage should be right around 42v for the pack.

 

[dnmun]

post up pictures of the BMS so we can tell you where to measure to determine if the BMS is actually blocking the charging because the one cell is full already. and post up pictures of the battery too. use 'upload attachement' under the dialog box, and then 'choose file' from your disk where the picture is located.

when you have the picture, then 'add file' to your post before submitting the post.

 

[eva-michael]

If it's a 12S LiFePO4 36V battery pack. It should be about 3.31-3.34/cell. So the pack should be about 39.7V-40V. It seems a cell is low power or dying.
A pack with good using and maintaing will be still very good for a LiFePO4 pack after 300 cycles 80%DOD(Of course, with "ok" quality and matching well cells inside and not some..B grade...to save manufaturing cost....).
For normal pouch LiFePO4 cell(A123 20Ah exclusive), we don't testing any which can make 2C continuous discharge. Most of them are 1C max continuous discharge. These packs may get killed by 500W motor.

 

[wesnewell]

Looks to me like you have a 10s1p lipo pack that is out of balance, Could be lco, nmc, or lmo chemistry. My guess would be nmc from the voltages posted with one cell at max 4.10V charge and the others lagging behind. I'd hook up the charger and check cell voltage periodically over a 24hr period. The lower cells should be rising in voltage until all cells balance around 4.10V. That may take longer than 24hrs. Or it could be lco, in which case none of the cells are fully charged to 4.2V yet.

 

[MARK???]

As they say a picture is worth more than this battery. As you all can see this is what it is. 10 lithium cells with no obvious damage and not holding a charge more than 39.7 Volts. Individual cells charged between one at Max 4.1V to Min 3.92 Volts. I've obviously had the battery on charge before but not for a 24 to 48 hour period. I can de-charge the 4.1 Volt cell to 3.97 Volts but what about those pesky low charge 3.92 / 3.93 Volt cells. Now I've posted some pictures ( HOPEFULLY ) it will clarify my options as what to do next. Until I get a better suggestion I'm going to put it back on the charger unless you tell me to stop. MARK???

 

[MARK???]

It was sold to me as a LiPo4 36V 12Ah battery that worked fine that had gone through 300 cycles. Also how do I test the charger that came with it to ensure that it isn't the problem. If so is there a charger that I should get that will work an a range of batteries ?. MARK???.

 

[MARK???]

The charger supplied is a Sans Li-ion 42.V --- 1.8Ah. Does this make any difference ???. MARK???.

 

[Clobber]

The charger supplied is a Sans Li-ion 42.V --- 1.8Ah. Does this make any difference ???. MARK???.

That is the charger that came with my Golden Motor lifepo4. - it should read 1.8A (not Ah BTW :wink: )

 

[wesnewell]

First, your photos suck. Too blurry to make anything out. If you've verified there are 10 cells, the pack has to be lipo, not lifepo4 as all 36V lifepo4 batteries are 12s, not 10s. If this is an old battery, I'd wager it's a LCO pack, with a nominal voltage of 37V, and a full charge voltage of 42V. Which btw, is right in line with your charger voltage.Put your charger on it and monitor cell volatge and verify cell voltages rise. If they don't, suspect a bad charger or bad bms and check charger voltage output to bms. It should be ~42V. If it is and cell voltages don't rise, I'd suspect a bad bms. If you have an rc charger or a 4.2V charger, you could try and charge each cell separately to make sure they will take a full charge. These procedures should isolate the problem between the batteries, bms, and charger.

 

[MARK???]

Yes sorry about the photos your right they do suck. About that RC 4.2V charger they seem to go from between $30 > $200 is there a brand or model of charger that will serve multiple uses if so what should I be looking for. MARK???.

 

[d8veh]

!0 cells is not LiFePO4, so forget about that.

The charging voltage will be about 42v, so each cell should be charged to 4.2v

Your balance problem is not the nine low ones. It's the one high one. When you charge the pack, all the cells increase until one hits 4.2v, then the BMS shuts off charging, so the lower ones don't get fully charged. Some BMS's can still do something after the shut-off time to rebalance the cells, but as you've already got it apart, it'll be much quicker to discharge the high one yourself. You can leave it connected while you discharge it.

Fixing this balance problem won't solve your cutting out because all cells are high enough to give maximum current. As Dogman points out, they may be old and tired, but the fact that they're all a similar voltage (apart from the high one) is a good sign of healthiness. Once you've got them balanced, a discharge cycle will show if any are weak.

You didn't answer the question: What current are you trying to draw from this battery? it's written on the controller. I know that the A2B motor is quite powerful, so I''d guess about 20 or 25 amps,which is too much for that battery, which is why the BMS is cutting off the battery when you're riding the bike.