In article ,
alo writes:
Hello...

I have a 12V 2.8Ah sealed lead acid battery... and a battery charger
that can be set from 50 mA to 300mA.

What should I set the charger at?

A guide is to divide the capacity by 7, and use that as the max current.
That would be 400mA max in your case. Lower is OK.

However, SLA chargers don't normally have current settings.
Are you sure the charger is intended for SLA batteries?

Not too sure if the battery is any good, but I thought I might try and
recharge it to see if I could get some use out of it. It had been a
backup battery in an alarm system.

They can be quite useful. I have a 7Ah one that was changed out
12 years ago, and still has its full capacity. Depends heavily
on how it has been treated. Running them flat is not good, and
neither is overcharging them.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]