Throttle showing half power, is it 48 volt Battery, Charger or Bike?

[fearlessfostick]

I took my first ever ride yesterday and throttle led showed full charge.  Rode the bike until half charge then plugged it in to recharge. According to charger the battery was fully charged.  Rode it again but it still showed half power and ran down quickly to empty. Lots of controller beeps before it completely quit.  Recharged it until I got a green.l hooked it up this morning and throttle led lights still show that there is only a half charge.   Plugged it in again and got a solid green.  Voltmeter  shows  fully charged battery at 47.9 volts.
I am not getting a full charge to the bike. Any ideas from the ebike doctors would be appreciated.
Thanks

[Sangesf]

I took my first ever ride yesterday and throttle led showed full charge.  Rode the bike until half charge then plugged it in to recharge. According to charger the battery was fully charged.  Rode it again but it still showed half power and ran down quickly to empty. Lots of controller beeps before it completely quit.  Recharged it until I got a green.l hooked it up this morning and throttle led lights still show that there is only a half charge.   Plugged it in again and got a solid green.  Voltmeter  shows  fully charged battery at 47.9 volts.
I am not getting a full charge to the bike. Any ideas from the ebike doctors would be appreciated.
Thanks

1.) "Half charge" on throttle indicator is actually "empty".
2.) 47.9v is NOT fully charged, it's 90% empty. (48v should read MUCH higher, like 59-60v when fully charged)
3.) If I had to take a guess, I would say the BMS is not letting you charge the battery..
4.) Another possibility is that the charger is not putting out enough charge..

With Voltmeter check voltage output on the charger itself.. If it reads in the high 50's then charger is good.
If that's the case, then it's probably the BMS.

[Andrew]

I never saw my GM 48v/21ah battery get above 54v on a full charge. 

[Sangesf]

I never saw my GM 48v/21ah battery get above 54v on a full charge. 

That's probably after pulling off the charger cord...

54v is 3.375v per cell or normal operating voltage of a 48v battery.
3.65-3.75v per cell is what they should be charged to, which is 58.4-60v, which if you check when the charger is finished AND still connected, should be the voltage at "full".

[Hardcore]

54.6 v is the voltage of the gm charger, so the battery should be 54v fully charged. Around 47.9 it isn't 90% empty, it should have used about 75% of its capabilities and the bms will shut down at about 80-85 % to protect the cells.

[Sangesf]

54.6 v is the voltage of the gm charger, so the battery should be 54v fully charged. Around 47.9 it isn't 90% empty, it should have used about 75% of its capabilities and the bms will shut down at about 80-85 % to protect the cells.

For a 48v LiFePO4 battery, 54.6 is NOMINAL. 3.3xv per cell.
Look up ANY lifepo4 battery and they will all tell you it's fully charged at a MINIMUM of 3.65v per cell or (16 x 3.65 = 58.4v).
At 47.9v (we'll say 48v to make the numbers easier is 48 / 16 = 3v per cell). That's near the end of it's discharge curve..

UNLESS, GM is selling you 15s batteries and calling that "48v"..
At 15s, then YES, you are correct..  But then you wouldnt be using a "48v" battery, youl'd have a "45v battery" and are being ripped off by GM.

I don't see them selling a 21AH battery..  Did you mean 12ah? 

[Bikemad]

UNLESS, GM is selling you 15s batteries and calling that "48v"..
At 15s, then YES, you are correct..  But then you wouldnt be using a "48v" battery, youl'd have a "45v battery" and are being ripped off by GM.

I don't see them selling a 21AH battery..  Did you mean 12ah?  

Frank, the GM battery Andrew was referring to is actually a 48V 12Ah pack comprised of 39 x 4Ah Lithium Manganese cells (13Series x 3Parallel).
These cells are stated by GM to be 3.8V nominal and 4.2V fully charged (49.4V nominal and 54.6V fully charged), but I suspect the more common stated nominal voltage of 3.7V per cell (48.1V for the pack) is probably more realistic.

Voltmeter  shows  fully charged battery at 47.9 volts.
I am not getting a full charge to the bike. Any ideas from the ebike doctors would be appreciated.

If it's a 48V pack, it is definitely not receiving a full charge, I suggest you check that your charger is set to the correct mains supply voltage (110V or 220V etc), as I suspect this may well be the cause of your problem.

Alan
 

[fearlessfostick]

Hi Alan
Thank you for your advice.  Several posts (including yours) mentioned a voltage input switch.  Initially I didn't see it but on a second look I did find a small toggle at the back of the charger which has 230 and 115.  It was set at 230.  I reset it to 115 volt and now it is charging and I am optimistic that things will work out.
I would not have been able to finish this build without the forum.  Thanks to all for your help.
Regards Peter