battery pack

[mygrumpy]

hi all newbie here.i want to make a 36v nimh pack,can i use 4 packs of 8 batteries wired in series and parallel,will be useing C cells, will it work it`s for a E-bike. john

 

[safe]

NiMh "C" cells are usually 1.2 Volts.

So I think you mean:

10 * 1.2 = 12 Volts.

Then you need to decide 36 Volts or 48 Volts.

For 36 Volts you get 10 (from above) times 3 = 30 batteries.

For 48 Volts you get 10 (from above) times 4 = 40 batteries.

Each "pack" of 10 batteries are in "series". (in other words they are end to end with each other)

To increase the voltage from the 12 Volts per "pack" to the larger voltages you wire them in series so that they increase the voltage.

That's all there is to it... :wink:

Another way to look at it is that you want to have 36 Volts. Each battery holds 1.2 Volts.

So it will take 1.2 * 30 = 36 Volts.

Just take 30 batteries and string them in a loooooong line end to end and you have what you want. (wow that would be one loooooong battery )

 

[fechter]

You might need to separate any parallel strings during charging. Nimh don't really play nice when charging in parallel, but I've heard of someone who used a special charger that allowed it.

Like Nicd, when the first string gets close to fully charged, the voltage drops, which will cause it to hog all the charging current, resulting in overheating and possible destruction. If you charge strings separately, you can combine them in parallel for discharge.

 

[safe]

Chargers are usually 12 Volts anyway.

So it's a good idea to limit each "pack" to 10 batteries (12 Volts) and when you charge them you address each "pack" separately.

 

[safe]

Like Nicd, when the first string gets close to fully charged, the voltage drops, which will cause it to hog all the charging current, resulting in overheating and possible destruction.

Wouldn't this trigger the "battery full" signal to the charger?

Unless you were using a timer based system the way most of the chargers for NiMh work is they look for a certain battery "effect" (a voltage drop) and then switch off when they see it.

So you might end up with one fully charged pack and others that are only partially charged. With every cycle the "heavily used" pack gets overworked and gets worse and worse...

 

[Leeps]

Well you could use 4 packs of 8 cells if they were wired all in series. 8*1.2=9.6 volts per pack 4 packs would make 38.4 volts. Its close enough to 36 volts.
Joe

 

[safe]

You would need to buy a charger that could deal with it...