[OT] Charging UPS batteries outside the UPS

[Jim Kuzdrall]

On Monday 06 August 2007 22:10, Ben Scott wrote:
> Hi all,
>
>   Off-topic but still techie question: Does anyone know anything
> about charging the batteries from a UPS using external equipment
> (i.e., not the charger built-in to the UPS)?
>
>   The battery consists of eight smaller units, wired together.  The
> wiring is easily disconnected.  Each unit is labeled "12 V, 7.2
> Ah/20HR".  Anyone if I can just hook each unit up to a regular
> automotive battery charger (one at a time) and charge them that way?

    It is safe to recharge them with a conventional automotive battery 
charger as you suggest.  Recharge them at a low rate.  If anything goes 
wrong, they will just get hot or not take a charge.

    At a low charge rate, the battery cannot get hot enough to burn up 
or damage its surrounding.  My auxiliary charger has a 6 amp and 2 amp 
setting. (You are welcome to use it - I will email it to you.)  2 amps 
at 13V is only 26W, which is not going to raise the temperature of a 
large surface area by much.
 
> V DC is. [4] Severe discharge typically also means the battery will
> not hold a load to spec, so it's an indication the battery is no
> good; no point in a UPS without a battery; loose battery connector
> indication;

    Actually, when lead-acid batteries lose capacity after many partial 
discharges, the recommendation is to have a "deep discharge" and 
complete recharge.  That brings back some of the capacity.

> what if the customer is stupid and didn't connect the battery.

    Most batteries, particularly lead-acid batteries, self discharge 
whether connected or not.  Keeping them in the refrigerator helps - if 
you can get the cooperation of the rest of the household.

Jim Kuzdrall