GM 48V12Ah battery pack: cell number, capacity

[sirprize]

Hi everybody,

For a little project with my MagicPie kit I need to know the operating voltage range of a MagicPie 48V setup.
To know that, I was wondering how the "LFP-4812S" battery pack from GM is built internally without having to open it. Can someone perhaps confirm my observations?

When fully loaded, I get a voltage of 54.7V. My first assumption was that it is a 16s pack. But that would mean 3.4V per cell when fully loaded. Seems to be too little.
After searching around in the forum, I think a 13s pack would be plausible. At 48V, it's about 3.7V per cell. Fully loaded it's 4.2V. Both voltages sound good, although a bit high if you want to use the pack for many cycles.

My questions are:
- Does the 48V battery pack from GM have 13 cells in series (13s)?
- Assuming a 13s pack, the absolute minimum voltage is 26V and the absolute maximum is 54.7V, correct?
- If stop the motor upon reaching 33V (2.5V per cell at 13s), would I waste much of the capacity?

If my questions seem too stupid, I'd really appreciate a few pointers on where to get the information I need.

Thanks for reading!
Kind regards,
Michael

[Dummy Dave]

Hi everybody,

For a little project with my MagicPie kit I need to know the operating voltage range of a MagicPie 48V setup.
To know that, I was wondering how the "LFP-4812S" battery pack from GM is built internally without having to open it. Can someone perhaps confirm my observations?

When fully loaded, I get a voltage of 54.7V. My first assumption was that it is a 16s pack. But that would mean 3.4V per cell when fully loaded. Seems to be too little.
After searching around in the forum, I think a 13s pack would be plausible. At 48V, it's about 3.7V per cell. Fully loaded it's 4.2V. Both voltages sound good, although a bit high if you want to use the pack for many cycles.

My questions are:
- Does the 48V battery pack from GM have 13 cells in series (13s)?
- Assuming a 13s pack, the absolute minimum voltage is 26V and the absolute maximum is 54.7V, correct?
- If stop the motor upon reaching 33V (2.5V per cell at 13s), would I waste much of the capacity?

If my questions seem too stupid, I'd really appreciate a few pointers on where to get the information I need.

Thanks for reading!
Kind regards,
Michael

Did you search this forum for this?
I seem to remember BikeMad and others talking about this in depth, not too long ago.

[MonkeyMagic]

its 13s I have mine open now
you can put another 3 cells in there too

yeh man do some searches first geez!! lol


if anyone has a GM battery and has some electronics knowledge, have a look in there because there is so much room if you want to add anything

peace out

[Bikemad]

My questions are:
- Does the 48V battery pack from GM have 13 cells in series (13s)?
- Assuming a 13s pack, the absolute minimum voltage is 26V and the absolute maximum is 54.7V, correct?
- If stop the motor upon reaching 33V (2.5V per cell at 13s), would I waste much of the capacity?

Michael,

The GM 48V 12Ah battery has 39 cells in total, and is made up of 13 groups of 3 x 4Ah paralleled cells connected in series (13S3P) which charge to 54.6V maximum and discharge to somewhere around 39V (3V per cell) minimum, giving close to full capacity, as shown in this typical discharge curve:



The cell's quoted 4Ah capacity is actually measured by discharging the cell all the way down to 2.5V, but the pack's Battery Management System (BMS) will actually cut out slightly before the cells are allowed to get that low. This is done deliberately to help improve the battery's life expectancy, as discharging the cells too low is detrimental to the lifespan of the pack.

Alan
 

[Leslie]

I bought a 15ah pack and a 20ah pack based upon my experience with the SLA's.  In would lucky to use 30% of a 15ah LI pack compared to 50% of a 24ah SLA pack for the same range use.

Hay Monkey,

Do you recon you could fit another P line in with the 13s3p pack inside that GM case?,  making it 13s4p?

Would def make it worth getting a 24v 12ah pack and add it to your 48v12ah pack so you gets a 48v 16ah and the max discharge rate would be higher too.

Any remaining cells are great to play with. I bought some old puffy cells really cheap to mess about wif.  Learn lots. 

[MonkeyMagic]

Yes you can fit another 3 cells in there but that's it.
I'm sure its the same cell holder as the rest of the range.

What do you mean "add it" ?

As in, connect the 2 batteries together using 2 x BMS - I guess that would work.

What I'm doing, is just starting off with 2 x long LiPo packs from hobbyking Alan put me onto. I wont bother with 24v I'll just stick with 48v+ all the way.

And add another 2 later on if I want. Reason being, is with the mid mounted pack on the frame, you can put a heap of long Lipo's underneath the tray easy as...