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?

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.

Thanks

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]

On Mon, 20 Jul 2009 14:32:37 +0100, alo wrote:

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?

Lead acid batteries are charged by setting the endpoint voltage (13.8V
for a 12V battery). NiCd/NiMH batteries are charged by setting the
charging current.

Sealed Lead Acid (SLA) are slightly different in that they are
charged by setting endpoint voltage but with an additional current
limiter and deliberate small overcharge. This is usually done
automatically by the charger.

It isn't usual for a SLA charger to be adjustable in the way you
describe - are you sure it is a SLA charger and not a NiCd/NiMH one?

alo wrote:
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?

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.

Thanks
10 hour rate is generally reckoned to be safe 'forever' so 280mAh.. or
go for a 1 hour charge at 2.8A.

On Mon, 20 Jul 2009 17:15:26 +0100, Peter Parry
wrote:
..

That appears to be a Skytronic 690.003. Albeit a rather expensive
one, they are mostly about GBP5. It is NOT a sealed lead acid battery
charger but a simple unregulated charger for vented batteries.

http://www.skytronic.co.uk/product/index.php?s=690.003

Have you got a part number or any other identification on the device
you have?


All I can see on it it is:

MW2168

Maybe I should buy something else.

Thanks

On Mon, 20 Jul 2009 19:54:42 +0100, alo wrote:


All I can see on it it is:

MW2168

Google is wonderful thing :-)

Is this it :-

http://cpc.farnell.com/jsp/search/pr...requestid=6356

if so you have a constant current NiCd/NiMH charger which won't do
your SLA battery much good at all.

http://cpc.farnell.com/_/bca12-350u/...0ma/dp/BT02565

is a simple version of the sort of thing you need.

On Mon, 20 Jul 2009 22:37:05 +0100, Peter Parry
wrote:


http://cpc.farnell.com/_/bca12-350u/...0ma/dp/BT02565

is a simple version of the sort of thing you need.

Well I ditched the dodgy charger bought off ebay, and bought the one
above.

The battery I was testing is defunct, but a new replacement one (for
my shed alarm) will now be kept charged by the above unit.


Thanks