GM Battery

[Leslie]

With the old SLA it was easy, every amp you draw 1 amp hour is needed.  So if you draw 20 amps cont max a 20 amp hour pack would hold up.  This worked well for me with SLA's and when I buy a lithium battery I will try to keep to the same.

The lithium's are better obviously.  Just like the lithium can last over 3 to 3.5 times longer you can get way with 1 amp hour per 3 to 3.5 amp draw. SO a 16amp hour battery I would estimate 48amps to 56 amps cont max, and 12ah could do 35 and 28 amps cont max at 800/100 cycles it will lose 20%.


GM specs are close enough to my best guess.

Max Discharge Current: 35A(12AH)

Max Discharge Current:  60A(16AH)


The way I work it out is nothing official, Its a lose fool proof guide, I want to make sure my pack would survive carting 150 kgs of shopping and little passengers and what not for the long haul.

Here yar.

The 16 ah will do between 58 amps max new and at 800-1000 full cycles will do 46 amps cont max.  It will lose 20%


The 12ah being a smaller capacity pack this spec is GM being careful and calculates to 3 amps times per amp hour.

The 12 ah battery will do 36+ amps new and 28 amps after 8000~1000 cycles.  The GM specs I feel are a good enough guide for most uses.

The GM specs are well within what GM motors require so expect the battery to live longer than 800 cycles as 800 cycles is worst case scenario.

Edit:

Max Continuous Discharge Current: 20A(12AH)

Max Continuous Discharge Current:30A(16AH)


Max continuous seems to work on a 1.66 amps x ah.

So a 12ah will output 20 amps max cont and 15 amps and at 800~100 cycles will lucky to do 15 amps cont max (dead battery).  You can see why the larger packs live longer hey!

And the 16 ah will do 30 amps cont and 20 amps at 800~1000 cycles.  (Close to dead.)

I'm sure the GM battery can handle more than is put on the web site.  We haven't considered BMS rating and whether the GM specs are based on the BMS and not on the cell.  The BMS usually limits the battery from being damaged based on what the cell is capable of.
Im still work on this thing.

[Leslie]

LFP-4820 48V/20AH



I'm particular interested in this battery.

Some questions of my own arise.


What is the cell configuration of this pack.  I notice it has the LIFEPO4 voltage specification on it.

Is this a Lifepo4 battery?

It is almost 3kg heavier than the ping packs of the same ah. This cant be put down to the nice plastic housing. It would weigh a little more than ping Duct tape, but not that much.

Is it the type of cell one being pouch cell and the other being cylidrical that adds more weight?

Ive also read the cylindrical cells have slightly better capacity than the pouches.

Can anyone give me some more info on the pack LFP-4820
48V/20AH    

[Wheels]

I'd also be interested in  more info on this 48 V 20 ah battery.  I'm looking at buying a Ping battery or something from GM.  The package on the GM is nice, but I also need to have the ability to draw amps.  I'm thinking the max cont of 20 amps on the 12 ah pack is a typo since I they posted 20 amps as max cont for their 10 ah pack in their pdf catalogue.  maybe it wasn't updated correctly when they listed their 12 ah pack online.  If the packs are max cont 2C, then they must be limited by the BMS since the cells themselves indicate max cont C of 2.5.
And do I understand that if you use a battery at 1C all the time as apposed to 2c even though it maybe rated for that, the pack will last longer even if you used the same amount of watthours per charge?

Also Anyone know how the working voltage of their 48V 12 ah batt compares to the working voltage of a ping 48 volt (supposed to be 53 Volts).compares to the GM 48V pack. or any for or against between the battery packs.  looks like the Ping is different chem and should give more charges, but anything else? or how many more charges?

[MasterCATZ]

also interested in that answer
I ened up skipping past them becasue I was unsure

[Leslie]

And do I understand that if you use a battery at 1C all the time as apposed to 2c even though it maybe rated for that, the pack will last longer even if you used the same amount of watthours per charge?

You lose capacity and gain resistance as they get older and the voltage slump increases into LVC faster.   Just as a smaller cell has less max C rating than a larger cell older cells do the same, loose C rating.

But a larger older cell has a larger max C rating and exhibit less voltage slump than a smaller older cell. More C rating means you're on the road for longer.

In the cell degradation world it comes down to max cycle life and how many full cycles.  At 2c that's a fast discharge,  Things like forgetting your credit card and having to ride back home, and getting places and back home faster makes the bike able over the years to complete more and deeper cycles.  

Not in everyone's situation this would happen as some use their bikes for 10 k rides bikes on weekends and stuff. The cell will die a grand father, pure old age, in this case.

I believe Packs that are rated at 800~1000 cycles are rated at full discharge at 1C not at the max C rating recommendation of 2C but this is the confusion you maybe pointing out.  The advertisement may need to indicate the cell life at C1 or C2

Given that you use the pack at 2C until it LVC and move down to one C, the pack may live its full life.

[Pavelstorek]

Golden Motor Lithium Ion battery packs are LiFePO4.

It uses these LiMn cells: 

Lithium ion rechargeable battery, 26650 size, LiPF6 electrolyte, Manganese Spinel structure cathode.
High energy density lithium ion battery cell.
Cell capacity: 3.8V 4AH
Cell diameter: 26.24 ± 0.16 mm (top end), 26.16 ± 0.10 mm (bottom end)
Cell height: 65.05 + 0.10/-0.15 mm
Cell weight: 92g

Hello,

is there a source, where I could purchase 3 cells for replacement in my battery pack (48V12Ah) as one of the 13 groups shows noticeably lower voltage and it seems to degrade the performance of the whole pack.

Not sure about the repair itself, as the cells are "welded" to the connecting strips, but first I am looking at the possibility to source the cells.

Many thanks,
Pavel