Please Help, Battery full, E-bike shows flat

[ooioo]

Hi Everyone, I am new here and a bit desperate

I have an 48V electric bicycle and a 48V lithium battery pack, I just fully charge my Battery and the Volt meter shows 53V, but when I connected it to my bike, the bicycle turns on and shows the battery counter as flat with a red LED light, I do not live near any bicycle repair shop so hopefully somehow here can be kind enough to guide me to diagnose and repair my bicycle myself.

Thanks a million in advance to any kind soul person who will come to my rescue!

 

[Gregory]

Hi and welcome to ES ooioo.

You haven’t given many details on which to work with (e.g. Does the bike even run? What battery type, age, BMS? Where did you measure voltages and what was plugged in at the time etc), so here’s some guesses in order that I’d check.
P.S. photos are always helpful.

1. Loose connection somewhere, check all plugs, pins are seated properly and wires not damaged.

2. It's often the battery. Assumption that battery is 16S LiFePO4 so would normally charge closer to 57V (but maybe less). If one or more strings of cells is weak or badly unbalanced in the battery then connecting a load causes the BMS to trip and hence low voltage warning light.
Check by measuring charger output plug voltage and then the individual cell voltages either on the BMS cell leads (if you have one) or at cell level. Try leaving charger attached for 1-2 days to balance cells and repeat.

3. Assuming you have a throttle with LED fuel gauge. They are generally pretty cheap and ordinary quality. I don’t have one but I think one wire carries full pack voltage for the gauge (the other 3 are for the throttle +, GND and signal, more wires if you have buttons), so check what the voltage is there. If at 53V then get a new throttle or ignore the red light.

Good luck

 

[d8veh]

How far can you ride the bike like that. Maybe the indicator lighta are faulty. If your bike doesn't run like that, you need to measure the battery voltage while it's switched on. Some batteries will show full voltage, but the BMS cuts off as soon as you try and draw any current.

 

[dogman dan]

Did the bike ever run?

53v is not generally fully charged for a 48v setup. What exactly do you have for a battery? What does the voltmeter say the charger output is?

One often overlooked problem is that the charger never really did charge the battery, due to a broken or loose connection at the plug.

It could just be a mismatch of the led indicators, which always suck, with the actual voltage of the battery you have.

 

[ooioo]

Hi and welcome to ES ooioo.

You haven’t given many details on which to work with (e.g. Does the bike even run? What battery type, age, BMS? Where did you measure voltages and what was plugged in at the time etc), so here’s some guesses in order that I’d check.
P.S. photos are always helpful.

1. Loose connection somewhere, check all plugs, pins are seated properly and wires not damaged.

2. It's often the battery. Assumption that battery is 16S LiFePO4 so would normally charge closer to 57V (but maybe less). If one or more strings of cells is weak or badly unbalanced in the battery then connecting a load causes the BMS to trip and hence low voltage warning light.
Check by measuring charger output plug voltage and then the individual cell voltages either on the BMS cell leads (if you have one) or at cell level. Try leaving charger attached for 1-2 days to balance cells and repeat.

3. Assuming you have a throttle with LED fuel gauge. They are generally pretty cheap and ordinary quality. I don’t have one but I think one wire carries full pack voltage for the gauge (the other 3 are for the throttle +, GND and signal, more wires if you have buttons), so check what the voltage is there. If at 53V then get a new throttle or ignore the red light.

Good luck

Hi Everybody thanks for the help, sorry for the slow response as my laptop also went bongkers for 2 days

My battery is from China 18650 battteries I think in 5s and 13packs, i think, I am not very technical,
but the battery is exactly like the link below

http://item.taobao.com/item.htm?id=16561567944

I Think Gregory is right that one of the cells is unbalance.

Hi Gregory thank you so much for the adivce, may I know how can I rebalance the battteries? Using any simple tools that I can get from a simple local hardware store down the road

Thank you so much!!!

 

[Gregory]

That Taobao link appears to be 14S 5P. It also appears to indicate 58V charger voltage. 14S x 4.2V = 58.8V.

Curious how many watts is your controller rated for? And has this bike ever run?


1. Check all connectors, plugs and wires are OK. Yank them, poke and inspect.
2. Take your Digital Multi Meter (DMM) and measure your charger output voltage (use the highest DC voltage setting first).
Around 58V it is good.

If charger is OK you can either


3. Measure individual cell voltages with the DMM set to a DC range above 5V. The multiple red wires on the BMS connect to all the positive terminals of the seriesed cells and the negative to the final most negative cell. That’s why there are 15 wires on a 14S battery. In series connection the positive of the second cell is the same as the negative of the first cell. This way the BMS (and you) can check and bleed each of the 14 series cells. Either unplug the multiple red wire plug, or at the pins below the socket on the BMS (under the cardboard). Be careful not to short them out. Measure adjacent wires. Between wires 1&2, then wires 2&3, then 3 &4 etc. Post the results up here. Then you might charge up low cells using a 4.2V power source; OR bleed down high cells using a light globe/resistor/discharger which gives the BMS a chance to bring the low cells up to voltage. I put this a #3 because if one cell is 0V you should not really charge it but discard it.

And/Or

4. Put battery on charge for 1-2 days so BMS may sloooowly top up low cells. It does this by bleeding the highest V cells. At 100mA (for ease of calculation) this would take 10 hours to bleed off 1Ah. And you have a 10Ah pack, and it’s probably more like 70mA, and it still keeps intermittently charging those high cells . Short version - it can take days to get cells in an unbalanced battery to 58V.

Photos are helpful.

 

[dogman dan]

Yes. Put it on the charger and leave it there for days. Let it charge overnight more often, if not every charge. The bms takes a lot of time.

If you have a voltmeter, (you need one), see if the charger is putting out 58v. If it's putting out a lot less, then that could be your primary problem. In your first post, it's clearly not 58v at the battery. It could be the charger voltage has faded, or it could just be that badly out of balance.

Flaky plugs between the charger and the battery have caused me problems in the past, so make sure plugged in is actually plugged in.

Did this pack sit on a shelf a long time in the off season? The bms might have ruined a cell if left uncharged long enough.

 

[ooioo]

That Taobao link appears to be 14S 5P. It also appears to indicate 58V charger voltage. 14S x 4.2V = 58.8V.

Curious how many watts is your controller rated for? And has this bike ever run?


1. Check all connectors, plugs and wires are OK. Yank them, poke and inspect.
2. Take your Digital Multi Meter (DMM) and measure your charger output voltage (use the highest DC voltage setting first).
Around 58V it is good.

If charger is OK you can either


3. Measure individual cell voltages with the DMM set to a DC range above 5V. The multiple red wires on the BMS connect to all the positive terminals of the seriesed cells and the negative to the final most negative cell. That’s why there are 15 wires on a 14S battery. In series connection the positive of the second cell is the same as the negative of the first cell. This way the BMS (and you) can check and bleed each of the 14 series cells. Either unplug the multiple red wire plug, or at the pins below the socket on the BMS (under the cardboard). Be careful not to short them out. Measure adjacent wires. Between wires 1&2, then wires 2&3, then 3 &4 etc. Post the results up here. Then you might charge up low cells using a 4.2V power source; OR bleed down high cells using a light globe/resistor/discharger which gives the BMS a chance to bring the low cells up to voltage. I put this a #3 because if one cell is 0V you should not really charge it but discard it.

And/Or

4. Put battery on charge for 1-2 days so BMS may sloooowly top up low cells. It does this by bleeding the highest V cells. At 100mA (for ease of calculation) this would take 10 hours to bleed off 1Ah. And you have a 10Ah pack, and it’s probably more like 70mA, and it still keeps intermittently charging those high cells . Short version - it can take days to get cells in an unbalanced battery to 58V.

Photos are helpful.

Hi Gregory First I would like to thank you so much for helping me!

1. all the wires look ok and secure
2. my charger measures 58.4 V out put
3. the battery output measures 54.9
the individual cells voltage are as follows
1. 3.46
2. 3.46
3. 3.46
4. 3.22
5. 3.46
6. 3.46
7. 3.46
8. 3.46
9. 3.46
10. 3.46
11. 3.22
12. 3.46
13. 3.22
14. 3.47
15. 3.46
16. 3.46

4. I tried connecting the whole battery pack to charger for 2 days, but it still won't work.

Sorry I do not know how to put up pictures.

 

[ooioo]

Is it possible to charge up each individual cell to balance it? I found a 3.7V charger, thank you so much again!

 

[johnjcbs]

It looks to me,that you have 16 DEAD cells.
Each cell should be ~4.1v fully charged.

 

[Gregory]

Best NOT charge cells with that 3.7V charger for now – it’s probably 4.2V output (you can check that).

Your battery is not exactly like the one in the Taobao link.
You’re saying you have 16S.

58.4V/16S = 3.65V per cell. This is a LiFePO4 battery.
LiFe charges up to about 3.65V but settles down to 3.4V or 3.3V pretty quickly. Single cell chargers for LiFe output 3.6 to 3.8V.


As well as balancing a BMS protects cells by checking for low voltage (2.7V?), high voltage (3.6V) and over current (e.g >30A).
So most of those cells look charged except 4,11,13. I would think controller & BMS should be OK with that though to run with the wheel off the ground.
Add a load though and weak cells may drop like a stone. Light bulbs make good test loads.
Has this bike ever run at 48V?


I’d put it back on charge and measure voltages again while charging several times over the next day. But don’t assume it is a battery problem. Controller might have HVC or LVC or something else may be the issue. When connected do you still see 54V where the power enters the controller? If so it’s probably not a BMS issue. For more help you’re going to need to provide details of the whole set up.

 

[999zip999]

Do you have a small red wire on the controller the start up wire. Is this connected ? Is this a kit and if yes what kind ?

 

[Gregory]

How to post pictures

When typing a reply it's the tab next to options called Upload Attachment.

 

[dnmun]

measure the cell voltages while charging. does it go when you stiil have the charger attached, but not on the battery alone?

 

[ooioo]

ThanksGregory! finally can upload some photos, yes don't think they sold me the same batteries as I ordered.
The batteries look huge, definitely not 18650, the size is about 36mm diameter by 120mm length

 

[ooioo]

This is battery is new, just charge it twice, the battery fail to turn green after I charge it for the second time, the first time it did about 20km, I previously had a 48 lipo battery but it expanded and died after 2 years. My bicycle is also from China and it suppose to run on 48V lead acid batteries.

 

[ooioo]

My China electric bike is about 4 years old and looks like this

 

[dogman dan]

Put it back on the charger, and keep charging. Hopefully it will balance eventually. It could take more than one or two days. The 3.22 cells are still undercharged. It's NOT DONE when the light first turns green. The red will turn on again periodically for a short time, then a long time green.

Don't be surprised if all the cells drop to 3.4v fairly fast. Cheap crappy lifepo4 tends to do that. But at some point while still on the charger, they should all get to 3.6v each or so.

Getting it to fully charged and balanced is the starting point. Let it sit and see if it can't hold 3.4v on all the cells after a few hours.

Then you can ride some, and see if any cells lose charge way early. See if the ones at 3.2 drop way lower than the others really soon in the ride.

 

[ooioo]

Put it back on the charger, and keep charging. Hopefully it will balance eventually. It could take more than one or two days. The 3.22 cells are still undercharged. It's NOT DONE when the light first turns green. The red will turn on again periodically for a short time, then a long time green.

Don't be surprised if all the cells drop to 3.4v fairly fast. Cheap crappy lifepo4 tends to do that. But at some point while still on the charger, they should all get to 3.6v each or so.

Getting it to fully charged and balanced is the starting point. Let it sit and see if it can't hold 3.4v on all the cells after a few hours.

Then you can ride some, and see if any cells lose charge way early. See if the ones at 3.2 drop way lower than the others really soon in the ride.

Hi Dogman, thanks for the great advice!

After putting on my charger for almost 1 week now, the voltage on my batter went up at a really slow pace from 53V to 55V. I tried to put the battery on the bike, but it still shows the battery is flat, and the voltage drop straight to 54.8V after I attached it to the bicycle.

Should i still continue leave the charger on my battery? or is there something wrong with the BMS or some cells? Anything else I can do other than putting battery to charger!

Thanks in advance!!!

 

[dnmun]

there is no way to know until you measure the cell voltages so we can eliminate the LVC turning off the battery. i asked earlier if you would just measure cell voltages while charging.

 

[ooioo]

there is no way to know until you measure the cell voltages so we can eliminate the LVC turning off the battery. i asked earlier if you would just measure cell voltages while charging.

Hi dumun, thanks for the help,

The charger is giving out 58.3V and I measured the battery while charging it also measures 58.3 V

But When i pull the charger off it is 55V, once I attached to bike the voltage is 54.8 and bike shows battery is flat

 

[dnmun]

batteries are not flat. they are usually cuboid. i can only assume you mean the battery is turned off and there is no voltage on the output? where did you measure? why can't you measure the cell voltages while the battery is charging?