charging batteries

[Goose]

What would the max. voltage you could charge a 48 volt battery bank with.  Somebody posted on these boards that the batteries will draw the voltage down to their voltage until they are fully charged.  But, is there a limit to where you could damage the batteries with too much voltage?  

[Nando]

Lead Batteries have a nominal voltage of 2 volts per cell.

When the cell is fully charged the voltage is 2.37 Volts per cell at 27 degrees Celsius.

There is another voltage and it is the equalizing voltage that varies form 2.4 to 2.45 volts per cell.

In your case, 48 volts the number of cells is 24 cells, for a fully charged battery the voltage will be 24 * 2.37 = 56.88 Volts.

Foe equalization the voltage would be 24 * 2.4 = 57.6 to 58.8 volts.

Remember that the battery temperature should be 27 degrees C.

There is a temperature correction that is different for the different Lead Acid chemistries.

I hope that this helps

Nando

[Goose]

Thanks Nando,

I guess I worded my question wrong,  but that is good to know also.  What I meant was, if the wind is blowing 40MPH and my generater is pumping out 130V, is my bank of batteries going to get damaged charging at that rate?   If so, what would the max rate be?

Thanks

[Nando]

Where are you located ??

The question at hand is not voltage but current and once the battery charged, voltage limits to protect the battery life.

130 Volts does not say the power, current and voltage will say what power the battery is absorbing.

Assuming the 48 volts and charging without a controller, the wind mill will have its voltage limited by the battery voltage plus the losses due to the cabling from the gen to the bat.

Indeed if you have 130 volts with the proper current, it is best to have a controller to charge the battery and a ballast load controller to protect the wind mill once the battery is charged.

Regards

Nando

[Nando]

Heck !! I forgot to respond to your basic question.

Battery charging rate depends on the battery amp/hour and its chemistry.

Normally, one should charge the bank at about 20 % amp/hour rate, so a 100 amp/hour should be charged at around 20 amps -- best info is to get it, from the battery manufacturer.

One may remember that the charging current while at the same time supplying power to an external load, the current into the battery should be as above and any additional current to go to the load.

Regards

Nando

[Goose]

Nando,

I'm from South Dakota, where it is almost time to start blasting pheasants!!  

Thanks for the explanation on batteries.   I have been a toolmaker for over 15 years now, so electronics are not my specialty.  I have many more dumb questions, and I hope the board doesn't get sick of me.

[wooferhound]

This will keep you busy for a while . . .

http://uuhome.de/william.darden/carfaq.htm