On 9 mar, 17:48, Ron Hardin wrote:
I have 4 replaced 12v UPS batteries, that might be handy for other
things if I keep them charged. What sort of current should go into
them? I think they're 9AH wnen new, so not automotive class.

One of them says ``constant voltage charge 13.6-13.8v'' but I'm
not sure what that means, operationally.

Lead acid, sealed.
--
Ron Hardin


On the internet, nobody knows you're a jerk.

Hello Ron,

For SLA (Sealed Lead Acid) he is right, you should charge them with a
current limited constant voltage. The current limiting is necessary
to avoid damage to the battery when you charge a used battery. With
the 13.6 to 13.8V voltage setting, and current limiting to
0.2*capacity, there is no risk in overcharging them. You can leave
them on the charger for prolonged time. As soon as the battery
received a full charge, the current reduces to a low value.

As you are planning to charge them at elevated temperature, you should
reduce the voltage somewhat. Probably you can find a datasheet of the
batteries to find out the V/degree that you have to correct in case of
temperature extremes.

You should avoid discharging the batteries to below 10v en storing
them in that state. The best thing is to store them in a cool place
and monitor the voltage every month. Normaly spoken charging each half
year is OK. A fully charged battery can withstand temperatures below
0 degr C (32 degr F.)

You must use a regulated current limited DC supply or a good quality
charger specially designed for charging lead batteries. You cannot use
chargers for NiCd or NiMh batteries.

Best Regards,

Wim
PA3DJS