batteries

esuark

Pedelecer
can anyone enlighten me about 48v batteries that I see advertised as 5-parallels 13-series cell quantity 65 with different AH`s with Samsung 35E cells? and in general how the AH rating is calculated. just confused. sjpt

Esteemed Pedelecer
AH should be the Ah rating of each cell, times the number of parallels (5). Those cells claim 3500mAh, so you should get Ah 3.5*5 =17.4Ah.

voltage is cell voltage * #series, eg 3.6v*13=46.8v
current rating is cell current rating & #parallel. max is 8amp*5=40amp, I can't see the continuous rating for that cell.

Last edited:

vfr400

Esteemed Pedelecer
All cells have the same voltage and run from 3.1v to 4.2v (average 3.6v), so to get a 48v battery, you put 13 in series, 10 for a 36v one. Each cell type has different other characteristics -mainly the amount of charge in them, expressed in Ah or Wh, and the rate at which they can give it, expressed as the continuous current.

When you buy a battery, it needs to be able to deliver the current that your controller allows continuously, with a bit of headroom, so if you have a 15A controller, you need a 20A continuous battery.

You need enough charge in the battery to do your rides. For a legal ebike, an average figure would be about 12 to 15wh/mile, so if you always want to ride 30 miles, you'd need over 450wh.

Watt-hours (wh)is a more accurate way of expressing battery capacity than amp-hours (Ah). A 10ah 48v battery is 10 x 48 = 480wh.

The cells normally have a designation that relates to capacity, like 18650 22P, where 22 means 2.2Ah. The P is the variant relating to other characteristics, like life and discharge rate. SAMSUNG 35E means 3.5ah (actually 3.45) and is capable of delivering 8A continuously, so 13S5p would be 13 x 3.6 = 48v (approx), 5 x 3.45 = 17Ah and 5 x 8 = 40A.

That's what the cell-pack can deliver, but the management board (BMS) has its own current limit. Only the battery supplier knows what that is. They normally write it in the listing. I'd fit a 30A or 35A BMS to a cell-pack like that.

Batteries degrade with use, so whatever characteristics you need, always try for 20% extra from the cell-pack to avoid problems in the future. The BMS won't degrade, so it will always allow the same current, but if you had a 20A cell-pack, a 20A BMS and a 20A controller, you'd start getting your first cut-outs pretty soon.

Last edited:

Nealh

Esteemed Pedelecer
Parallel are the batteries connected to each other to form a string or group of cells, the amount of cells in parallel can be as many as you like.
Series is the amount of Parallel strings/groups also connected to gain the required voltage.
Each parallel string/group has a nominal voltage of 3.6/3.7v & max voltage which is 4.2v no matter how many cells in parallel. The voltage is always the same the capacity/mah & current isn't.
The mah & current are multiplied by however many cells there are.

For voltage one cobbles as many strings/groups together in + - + - + - + - +, ratio etc,etc as one likes.
So for 12v one has 3 groups in series.
24v = 6 groups in series.
36v = 10 groups .
44v = 12 groups.
48v = 13 groups.
52v = 14 groups.
60v = 16 groups.
and one can keep connecting more for more voltage.

esuark

Pedelecer
Parallel are the batteries connected to each other to form a string or group of cells, the amount of cells in parallel can be as many as you like.
Series is the amount of Parallel strings/groups also connected to gain the required voltage.
Each parallel string/group has a nominal voltage of 3.6/3.7v & max voltage which is 4.2v no matter how many cells in parallel. The voltage is always the same the capacity/mah & current isn't.
The mah & current are multiplied by however many cells there are.

For voltage one cobbles as many strings/groups together in + - + - + - + - +, ratio etc,etc as one likes.
So for 12v one has 3 groups in series.
24v = 6 groups in series.
36v = 10 groups .
44v = 12 groups.
48v = 13 groups.
52v = 14 groups.
60v = 16 groups.
and one can keep connecting more for more voltage.

vfr400

Esteemed Pedelecer
For voltage one cobbles as many strings/groups together in + - + - + - + - +, ratio etc,etc as one likes.
So for 12v one has 3 groups in series.
24v = 6 groups in series.
Slight correction: 24v is 7 cells. Probably just a typo, otherwise you should have had another cup of coffeee to clear your head before starting your work.

• Nealh

Nealh

Esteemed Pedelecer
Yes quite right 24v is 7s.

• esuark

esuark

Pedelecer
OK thanks for the information much appreciated..........