Recharging 12V AGM battery from mains

[antobag]

Hi all,

I've received a new 100Ah 12V AGM deep-cycle battery. It's this one here: http://www.alpha-batteries.co.uk/100...isure-battery/

I know that batteries sometimes arrive slightly discharged, even when new. I was wondering if I could charge it up from the mains using a cheap car battery charger. The charger plugs into the mains (AC), connects to the battery with crocodile clips and has two LED lights (one to show "Power", one that says "Full"). It's very simple but it does the job for standard car batteries. I just want to make sure that it'd be fine for my AGM battery before hooking it up - I don't want to cause any damage to the battery before I've even used it!

Any help would be much appreciated.

[Sunking]

No problem make sure to disconnect it when the charger says it is full. Just don't make a habit of it.

[antobag]

Many thanks Sunking. That's a load off my mind.

[antobag]

Hmm, I've had a quick look at the instructions for my battery charger and they state "The largest capacity lead acid battery that should be charged is 70Ah". Why is this? Is this being overly cautious, or could it actually cause damage to a battery of 100Ah?

I've found the make of charger online, it's the following: http://www.fastcardirect.co.uk/home/...roducts_id=501

[Sunking]

Hmm, I've had a quick look at the instructions for my battery charger and they state "The largest capacity lead acid battery that should be charged is 70Ah". Why is this?

Actually 70 AH is an exaggeration, 20 to 30 AH is more like it. You charger is 2.6 amps, very small. That means if you had a 70 AH battery fully discharged would take [70 AH / 2.6 A] x 1.3 = 35 hours to recharge. It just means it will take a long time if you have a battery larger than 70 AH that is discharged deeply. If your battery is new should not take to awful long. No problem, just be patient.

Ideally you want a charger to provide a C/8 charge current where C = the battery Amp Hour Capacity and 8 = Hours. So if you have say a 200 AH battery you want a 200 AH / 8 H = 25 amp charger.

[antobag]

Actually 70 AH is an exaggeration, 20 to 30 AH is more like it. You charger is 2.6 amps, very small. That means if you had a 70 AH battery fully discharged would take [70 AH / 2.6 A] x 1.3 = 35 hours to recharge. It just means it will take a long time if you have a battery larger than 70 AH that is discharged deeply. If your battery is new should not take to awful long. No problem, just be patient.

Ideally you want a charger to provide a C/8 charge current where C = the battery Amp Hour Capacity and 8 = Hours. So if you have say a 200 AH battery you want a 200 AH / 8 H = 25 amp charger.

Thanks once again Sunking - a fast and informative response. Much appreciated.

[Sunking]

Thanks once again Sunking - a fast and informative response. Much appreciated.

You are welcome. Don't tell anyone I helped you, it would ruin my reputation.

[Amy@altE]

You are welcome. Don't tell anyone I helped you, it would ruin my reputation.

Hahahaha. See, now did that hurt so bad? ; )

[antobag]

Haha, it appears your reputation precedes you. I feel privileged to have been treated so kindly!

[PNjunction]

Don't cheap out on your charger. Penny wise and pound foolish.

What I consider one of the absolute best chargers which should be easy to find in the UK is the Tecmate Optimate series. I'd personally recommend the Optimate 6 for your leisure battery, and of course any other battery you have:

http://www.optimate.co.uk/cg020001.htm

Then again, there is also CTEK, which is a fine charger. I'd look into the CTEK Multi MXS 7.0. But for set-n-forget with enough good stuff to keep ultra-battery geeks satisfied, the Optimate is king in my book.

I cringe when I see the charger offerings from the place you got your battery from.

[mschulz]

Don't cheap out on your charger. Penny wise and pound foolish.

What I consider one of the absolute best chargers which should be easy to find in the UK is the Tecmate Optimate series. I'd personally recommend the Optimate 6 for your leisure battery, and of course any other battery you have:

http://www.optimate.co.uk/cg020001.htm

Then again, there is also CTEK, which is a fine charger. I'd look into the CTEK Multi MXS 7.0. But for set-n-forget with enough good stuff to keep ultra-battery geeks satisfied, the Optimate is king in my book.

I cringe when I see the charger offerings from the place you got your battery from.

I am no expert, but using that 5 amp charger you are recommending is going to take some serious generator time to charge a 100 amp battery back up if it were at 50% DOD - like 10 hours.

[PNjunction]

Ah yes it will take a long time but the op mentioned charging from the mains not a generator. Possibly a one-off charge now and then in the leisure caravan type setup...

We don't know the extent of his operations. The good thing is that it will not only charge his 100ah battery, but any others like vehicular batteries too so I had multi-purpose in mind.

For hardcore solar / genny, by all means get a bigger charger!

[antobag]

Many thanks to everyone for the great suggestions and knowledge. It's much appreciated.