Faulty battery and pie

[jumpup]

My Magic Pie and accessories eventually cleared customs, but slight disappointment, as I had to go down to the bike shop to have the rim assembled and aligned, some spokes were lying loose in the box, luckily all the parts were there...

Bought the 36v 16ah GM battery - what a major disappointment!  The battery charged for about 3 minutes and initially I thought "Great job", they charged it before dispatching it, however it only lasted about 2 minutes and everything went dead.

Turning they battery key off and on, brings it all back to life, but only for a few seconds.

Trouble shooting revealed the following:
The charger yields a steady 41.8V and the battery when charged (charged for about 3 minutes again), shows 39.1V.  I connected three 12V car headlights (in series) and connected them to the battery.  After about 4 minutes the lights went dead. Voltage just before it died was 38.7V and this dropped to zero over a period of about 2 seconds.  Voltage at the charging jack, measured 16.7V

When I disconnected the load from the battery, voltage at the battery terminal and charging jack went to 36.9V and after I turned the key off voltage at the charging jack went to 38.7V (at terminal it was zero - key switched off).

After turning the key on again, the lights went on for a few seconds and the voltages were exactly as recorded above.

The battery looks fine on inside, but I'm annoyed that it is made from 40 small cylindrical cells - I got the impression from the website that it would be larger rectangular cells.  The date stamped on the battery is 2010/12/6.   

I didn't check any of the individual cell voltages, as I suspect that I have a PCM problem.

The USB cable when connected to the pie just beeps at a constant interval, as per other posts (http://www.youtube.com/watch?v=UMv57gzxWbE).  The last post on that topic would suggest that a solution has not yet been found.   

Overall I'm out of pocket in excess of USD 1,000 and I have nothing that is working.  I did e-mail GM, but have not yet received any reply.   

Any advice would be much appreciated.

[Bikemad]

Hi andto the forum.

It sounds as if you have been extremely unlucky with your purchase, and if you purchased this kit direct from GM China, I suggest that you send another email to tom@goldenmotor.com stating your purchase details and explain the problems that you have already mentioned here, but try and keep the email as simple and easy to understand as possible, as his English is not particularly good.

It might be a good idea to leave the battery on charge for at least 10-12 hours (if you haven't already done so) to see if there is any noticeable improvement.

It would be nice to find out what Tom's response will be, regarding diagnosing and rectifying your problem, so please keep us informed of your progress.

Alan
 

[jumpup]

Hi Alan

Thank you for the warm welcome and advice.

I did e-mail Tom as you suggested - hopefully this will be resolved soon.

I shall also leave battery on charge overnight, however the green light on charger would suggest to me that no more energy is being added to the pack - maybe there is a problem with the charger LED, so I'll give it a go anyway...

Thanks again for your help - I shall post as and when I get a response from China.

[fearlessfostick]

Check the battery charger to see which voltage it is on  240 or 115.  You may have already checked this but I am posting just in case.  My charger was initially set at 240 and would stay green when charging and I was having power problems until I adjusted it.  Just a thought!

[jumpup]

I'm in Ireland (240V) and charger has no switch - it switches automatically (I presume).  I did check charger, it yields a steady 41.8V.  Thanks anyway...

Heard from China today - they confirmed that 36V16Ah battery has been eliminated from their inventory (probably too many defects, I guess), but they offered to send me out a 36V12Ah.  According to them, this is a well tested pack with great performance.

Cheers, lads!

[GM Canada]

It is not because they are unreliable. There have been many sold with very few issues. The 36v16Ah and the 48v12Ah battery is no longer available as we are moving to LiFePO4 instead of Lithium Manganese and you can't get enough LiFePO4 cells in the case to get a battery with those numbers. The 36v12Ah LiFePO4 replaces the 36v16Ah Lithium and the 48v10Ah LifePO4 replaces the 48v12Ah Lithium. I have done many tests with both batteries now and find it very interesting that you can get over 9.5 amps of power from a 48v10ah lifepo4 battery and just over 10 amp hours from a 48v12 lithium battery. I imagine it is because the LiFePO4 battery self balances the cells and it can run down further before any individual cell would cause the BMS to kick it out for protection. Plus they are faster charging and have a longer life cycle of charges. LifePO4 is an all win situation!

Gary

[Who42]

The new Large format LiFePO4 are much better and really do deliver C3 rated output
Golden Motor now use Larger cells in their 24v, 36v & 48v LiFePO4 Battery Packs for Electric Bikes, this means reliability and it makes possible for BMS to manage and protect each cell individually.The new LiFePO4 Battery Packs are rated at C3 Continuous Discharge Current: 30A = 48v  36A = 36v   36A= 24v  I have found that the new Larger cell Battery Packs are much better than the older type with blue and orange 4amp round cells  
In the old battery packs, the BMS controlled groups of 3 or 4  4amp cells in parallel not individually    
The BMS  controlling each cell individually is by far the best method  
NEW INTERNAL BATTERY SIZE  PLUS BMS = 18mm x 65mm x 133mm

24v=25.6v 12Ah: 8 x 18mm x 65mm x 133mm = 8 cells  
=144mm x 65mm x 133mm

36v=38.4v12Ah: 12 x 18mm x 65mm x 133mm = 12 cells
=216mm x 65mm x 133mm

48v=51.2v10Ah: 16 x 16mm x 65mm x 133mm = 16 cells
=256mm x 65mm x 133mm

[jumpup]

Yip, that sure is what they are advertising on their website - safe and large cell LiFePO4 and that sure is what I paid for.

However I got the older LiPo cells (orange) and either they and/or PCM is defective....

I have a picture of them, but can't seem to upload it.

[jumpup]

Happy Days!!!

Thank you Gary for all you help!  I do agree - you are "Super G" 

GM eventually sent out a replacement battery and this one does have the newer LiFePO4 cells inside.

I am surprised though that they sent me out an identical charger.  The back of this charger also states "Li-ion Battery Charger" and it has an output rated at 42.0V, same as the other one that came with the dead pack containing the bunch of orange cells.   

Hopefully the BMS will prevent the cells from overcharging (38.4V vs. 42.0V).  No documentation came with any of the kit and there isn't much in the forum on this either.

It was in another forum that I read that once charged, the pack should be left on the charger for at least another hour, as some BMS only balances the cells after charging has finished.

Anyway, I did a quick 8km around the neighborhood averaging around 28km/h without breaking a sweat, as I didn't do any peddling.   

The fuel gauge was still showing green, so I guess all is working fine.

Should I charge a pack after every use, even if I only used 30%, or is it better to use it until it is flat - like the good old days with nicad batteries?  I know this will not have a memory effect, but the pack is limited to a number of cycles and I presume a charge from 70% to full will still count as one cycle.

Thanks for all your help and advice!

[Pwd]

Not sure about the charger.

From what I've learned, its better to charge your battery as often as possible. Someone correct me if I'm wrong; but keeping the battery above 80% capacity will give you optimal battery/cell life.

 - Paul

[Andrew]

Not sure about the charger.

From what I've learned, its better to charge your battery as often as possible. Someone correct me if I'm wrong; but keeping the battery above 80% capacity will give you optimal battery/cell life.

 - Paul

Yep!

[GM Canada]

When I first asked if the chargers were the same GM China said yes. Then when I had a problem with a charger they told me "Thats because they are different".

Please use only the new charger on the new battery.

Gary