Bottle Battery Charger issue/cannot charge

[athletic91]

Hi all making my first post,
I have a 24v chinese lithium bottle battery that came with its stock charger.
The charger led is red when its charging and green when it has charge finished.
The problem now is when i plug the charger into empty battery, the led light is green and will not charge the battery.
Does the fault lies with tbe battery or charger?

 

[wineboyrider]

Sounds more like a loose wire connecting inside the battery or charger. You have to test the charger for voltage first with a volt meter (should read 24 + volts) if it does then you need to inspect the charging wire inside of your battery or from your battery charging plug housing to your battery + and -. The battery even if low should have a charge ie. read a voltage around 24 v.

 

[athletic91]

Thank but i currently do not have access to a voltmeter.

Could it be possible that the charger is falsely sensing that the battery is full and thus refuse to charge it?

 

[dnmun]

yep, loose wire or blown fuse most likely. but you have to go buy a voltmeter before doing anything else.

you need to measure the voltage on the output of your charger, and you need to open the bottle battery and pull out the battery and take a picture so we can tell you what to do next to test it.

you can 'upload attachment' under the dialog box, 'choose file' from your picture album, hit 'open' on your album picture and it will appear under the post when you hit 'add file' and then we can explain to you what the parts are.

 

[athletic91]

Here are some photos, the fuse looks fine

 

[dnmun]

go to harbor freight and buy a voltmeter. they are cheap there and sometimes you can get them on sale for under $3.

 

[dogman dan]

The symptoms indicate to me that someplace, there is a break in the connection between the charger and the battery. Green means finished, or disconnected.

Look for broken wires or something wrong at the plug, then with a voltmeter, keep tracing looking for the place where the charger no longer sends voltage to the battery. There will be your broken wire, or whatever.

Typically it's a plug problem.

 

[dnmun]

i think his charging plug is on the other end, looks like the C- wire goes back down along the battery inside. the green wire. but eventually he will get a voltmeter.

 

[izeman]

i once had an issue with this as well. in my case the plug/ socket was broken. charger output voltage fine, all connecting wires fine, but no charge at all. then i measured resistance of GND of the socket to the solder pads (buried under loads of heatglue) and it was broken. replaced the socket and it was ok again.
and once again: as dnum stated: get a multimeter. trying to find battery problems w/o one is like guessing mileage w/o a speedometer and a fuel gauge.

 

[dogman dan]

The problem can be anywhere, and even with a voltmeter you can be fooled. In one case I had, I just couldn't figure it out, one day the charger filled my battery, the next it did not.

Finally I found the problem inside the charger, one of the output wires was soldered poorly, and would intermittently connect and disconnect. Of course, every time I checked the charger with the voltmeter, it happened to be putting out voltage.

 

[athletic91]

Ok here is something weird.

I took my almost flat battery back in the bike and rode for about 100meters and then tried charging it.

The charger led turned red signalling charging but then a minute later turn green.

Could it be the BMS in the battery or charger sensing falsely that the battery is full

 

[dnmun]

what kind of voltmeter did you get and what is the voltage on the cells in the battery?

 

[dogman dan]

Or it could be that flaky connection I keep saying you have.

 

[marty]

Try the easiest thing first. Don't look at the colored lights and just leave battery connected to the charger for 12 hours or so.

Something else that has worked for me when I had the same problem is to try powering up charger then connecting battery. If that don't work? Try connecting battery then switching charger on. Does charger have a switch? Think correct way is to first turn charger on then connect battery. I might be wrong about this?

 

[athletic91]

It is my assumption that the soldered area leading to the green charging wire is "Burn". Thus there is a break in connection. will re soldering help?

 

[marty]

It is my assumption that the soldered area leading to the green charging wire is "Burn". Thus there is a break in connection. will re soldering help?

Looks to me like some flux from the solder job. Do you have a volt meter? Volt meters usually have a setting called Ohms. If you think that solder joint is bad? Look at it with a magnifier glass. Poke it a little to see if it is cracked. Can you disconnect that Green wire at the other end? With that Green wire disconnected, measure resistance between Green wire and solder joint with your Ohm meter.

Ohm meters are a fun tool to check fuses, light bulbs, wire, resistors. Here is some information on - How to Use an Ohmmeter
http://www.wikihow.com/Use-an-Ohmmeter

Tip - remove fuse, disconnect battery, before poking around with with Ohm meter test leads.

 

[athletic91]

UPDATES

1)Finally bought myself a multimeter. Before disassembling the case, the voltage output for this 24v lifepo4 pack was only 21.8v,2 of 4 led indicator lit. Consultation with my local electric bike shop told me that the voltage is too low(battery over discharged) hence the BMS cuts off the charging.

2)My next step was to open up the battery to measure individual cell voltage, however i had a difficulty getting the cells out due to the metal tabs that were stuck in the battery.

3)Since step 2 failed, i measured voltage from the bms wires. There were a total of 7 wires and, starting from the right,with the voltmeter prong on wires 1 and 2 were 4.17v, wire 3 and 4 were 4.17v, wires 5 and 6 were 4.17v and wires 6 and 7 were 0.6v

4)Since the BMS was preventing the battery from being charged , why not bypass it ! desoldered the - green charging wire from the bms and soldered it to the the - end of the cells. the yellow + charging wire was alr soldered to the + side of the battery cells and i did not touch it.

5) Plug the charger in and vola its charging it as i type!!!( charger led turn red, indicating charging)
Edit, it further discharged the battery instead of charging

 

[dnmun]

did not really follow what you meant by alr soldered. did you mean air soldered?

if the cells are all at 4.17V then it was fully charged already. assuming you measured it after removing from the charger.

if you measure while charging the high cell would pop out.

you don't have to unsolder the BMS to bypass it, you can use alligator clip jumper wire connecting the B- negative battery lead to the C- charger lead and leave the BMS as is.

but you have no protection from overcharging, in either case.

 

[athletic91]

did not really follow what you meant by alr soldered. did you mean air soldered?

if the cells are all at 4.17V then it was fully charged already. assuming you measured it after removing from the charger.

if you measure while charging the high cell would pop out.

you don't have to unsolder the BMS to bypass it, you can use alligator clip jumper wire connecting the B- negative battery lead to the C- charger lead and leave the BMS as is.

but you have no protection from overcharging, in either case.

do you mean like this??

 

[athletic91]

Crap my battery charger turn red to green indicating that the battery shld be full.

Took the voltmeter to test the output voltage and its only 20.7v for the whole pack 0 of 4 battery inditor led strength lit!!, before it was 21.8v and 2 of 4 battery led indicator lights lit...ie i showhow discharge it furthur instead of charging it!!

 

[dnmun]

yep, that woulda bypassed the BMS for charging. but your BMS is shutting off the charge for a reason, because one cell is past the HVC.

if you look on the backside of the BMS pcb you can see where the sense wire plug is soldered into the pcb. each of those solder spots is connected to the individual cells through the sense wires.

to measure cell voltages, measure between each adjacent pin to measure all 13 cell voltages while the battery is charging. put the black probe on the lower one and the red probe on the next one higher starting from where it says B- to the B1 spot on the sense wire plug. that is the first cell #1.

measure each one while it is charging and list the voltages.

 

[athletic91]

yep, that woulda bypassed the BMS for charging. but your BMS is shutting off the charge for a reason, because one cell is past the HVC.

if you look on the backside of the BMS pcb you can see where the sense wire plug is soldered into the pcb. each of those solder spots is connected to the individual cells through the sense wires.

to measure cell voltages, measure between each adjacent pin to measure all 13 cell voltages while the battery is charging. put the black probe on the lower one and the red probe on the next one higher starting from where it says B- to the B1 spot on the sense wire plug. that is the first cell #1.

measure each one while it is charging and list the voltages.

I have given up on the BMS and would like to bypass it. However your method of bypass does not work, although the voltage between the b- and c-wire is 29.2v, between b- and charging + wire also 29.2v, the charger led is green, which means its not charging..

 

[athletic91]

Finally manage to take it out and had a few interesting observations.
1) are thes A123 cells ? or 26650.
2) the config for this 24v pack is 7s3p
3)voltage for the first 6s3p is 21.5v which i guess is normal.
4)voltage for the last 1s3p is only 0.4v(cells highlighted in red), which i assume is dead, although im trying to revive them with 4x1,5vAA batteries overnight.
5)If all else fails, i plan to convert it to a 7s2p pack as i do not wish to buy new cells to mix.