AGM battery plus old car battery trickle charger?

FlightRisk · Spanner Monkey Joined: 08 Jul 2014 Karma :

My battery has gotten a bit run down and I want to give it a boost before it strands me somewhere but the only thing I have around to charge it is this old car battery charger.

The battery is a 12V 8Ah sealed AGM type.

The charger is a very old trickle charger. It has no controls, just a 6V/12V switch and an ammeter needle on the front which goes from 1 to 6A. I'm told it starts at the high end and drops lower as your battery charges.

Are these likely to play nice together or will it fVc< up my battery / explode in a shower of acid in my living room?
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Honda CB500S

Robby · Dirty Old Man Joined: 16 May 2002 Karma :

Bike batteries are typically charged at about 1A. Charging at too high a rate may damage the battery.

You have three options.
1. Just put it on the charger, it'll probably be fine.
2. Charge the car battery, hook it up to the bike battery with jump leads, which will charge the bike battery.
3. Get a proper bike charger.

wr6133 · World Chat Champion Joined: 31 Dec 2013 Karma :

I've charged motobatt AGM things with one of those £3 chargers that is little more than a plug with a couple of wires and some crocodile clips.

Zero explosions occurred, so I would imagine your charger is ok

FlightRisk · Spanner Monkey Joined: 08 Jul 2014 Karma :

Hmm...

So I hooked it up, the ammeter didn't go anywhere near the 6A end. Started at 1.1A and then very quickly dropped to about 0.8A, which seems ok-ish.
But, it started to make a faint bubbling sound and then after about 5 minutes a very very faint 'tss...... tss...' sound like tiny bits of gas escaping.

I'm not sure if that's ok?

My multimeter is somewhere inaccessible with some other tools I could use. Sad

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Honda CB500S

The Artist · Super Spammer Joined: 06 Jan 2008 Karma :

Bubbling is normal but keep an eye on it. Ideally get a smart charger but a standard charger will work fine.

AGM's work on the same principle as lead acid and the hissing is just gas escaping to prevent them exploding. AGM's and Gel batteries are just VRLA's essentially.

WD Forte · World Chat Champion Joined: 17 Jun 2010 Karma :

I'd suggest you play safe and dont leave it connected for too long
until you've tested the output voltage on float charge.
Personally I'd just charge it enough to get the bike started then let the bikes system take over until i knew I could trust the old charger.
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bikers smell of wee