Battery Vehicle Society

Greg's right, but if by 'red top' you mean a genuine Hawker AGM then I can say from experience that they are very good. I have an old (maybe 8 or 10 years old now) Hawker Red Top from an old race car that I keep as a standby battery for jump starting the car. It's less than 20Ah (about the size of a motorcycle battery), rarely gets a regular maintenance charge (it gets charged whenever I think about it, which isn't often) yet always manages to give a very healthy wack of current when asked. Recently I used it to start a friends 3 litre diesel in sub-zero temperatures. Even though it's probably the best part of a year since I last charged this little battery it turned that big, cold engine over as if it was a small motorcycle engine.

Jeremy

Jeremy wrote:Those batteries seem to be sitting at about the right voltage for a fully charged LA, so what's the problem?

You can't tell whether or not they will deliver the rated capacity without doing a load test, as the off-load terminal voltage doesn't tell you anything worthwhile.

Why not give them a run and see if the voltage sags under load, then, perhaps, do a full discharge test to see if they have the rated capacity? Only then would anyone be able to say for sure whether or not these batteries are duds - on the basis of your measurements so far I think they're probably fine.

Jeremy

I'd vouch for that too...........whats wrong with them BNW

Nothing so far has given me any cause for concern, 12v SLA's will sit at around 12.7 off charge, if they havent been charged for a LONG time then I might expect to see the at 12.4v or even 12.2 if fairly flat (all off load 24hr resting voltages)

Load test them, see if they hold up under their "rated" discharge rates, looking at the data sheet they should be able to supply 12.6 amps for 1hr, there are other discharge rates but Yuasa quote a C1 rate so give it a go.

ChrisB

Well, I gave it a good go at a range test today but results were inconclusive as the two strings got seperated. Will try again tomorrow...

TBH the best way is to set up a static 12amp discharge and see if they will hold up, I suspect you'll be discharging them well outside their rated output on the bike so wont really give you a good idea of there "rated" output

ChrisB

That's not going to happen, I'm just going to test them by using them in my bike (where they will stay if they work) and see if performance improves over the old and knacked batteries they're replacing.

This sucks. they're not holding charge, and soon drop to 13.3 volts. Not happy.

How long off charge no loading does that voltage represent ??

Thats a figure I would expect to see............. in fact its very good
12.6 V to 12.8 V (2.10-2.13V per cell) fully charged, no load, off charge, is quite normal, so your 13.3 volts must be taken just off charge and thus as the on charge voltage will be around 14.2 V to 14.5 V but then once they come off charge they will drop down to 12.8 fairly quickly.
I still say you need to do a propper discharge rate at their rated current before you will know if they have a problem or not .......sadly its the only way to know for sure, I suspect they will hold up fine.

ChrisB