Thread: Flat AGM batteries

Slow, low current charger.
If you have one with a recon function that's better.

Hi Don and as Tombie posted, but it is highly likely that they are either damaged or even totally stuffed.

Carry out Tombie's advice, but not just once.

Once the batteries are fully charged, let them stay in the FLOAT mode for at least 8 hours, then disconnect the charger and let the batteries settle for around 12 hours and then repeat the charge cycle.

BTW, best to charge each battery separately, just in case one battery is recoverable and the other may not be.

Thanks guys, that's along the lines I was thinking, too.
I'll loan him my ctek 5.0 it has a reconditioning feature on ot.

G'day Don,

The ctek may not be the best charger if the AGM is really flat. I don't know the 5.0 personally but my smart charger will come up with a failed warning if the battery doesn't get up to a certain voltage in a certain time.

I refreshed my Optima that was down to 1.5V by connecting another battery in parallel with the charger to get the Optima up to the minimum voltage the charger would accept.

Worked a treat and that was 2 years ago and battery still good in my 74 Jag.

You may have to set the charger to a fixed charge rate for a few hours to get some charge into it to get a reading and then do what Drivesafe said with the C-Tek.
I've had a flat AGM on and off a Projector multi-stage charger and a solar 15 watt trickle charger for about a month now and its only now seeming to recover.

Sent from my SM-G900I using AULRO mobile app

Originally Posted by drivesafe

Hi Don and as Tombie posted, but it is highly likely that they are either damaged or even totally stuffed.

Carry out Tombie's advice, but not just once.

Once the batteries are fully charged, let them stay in the FLOAT mode for at least 8 hours, then disconnect the charger and let the batteries settle for around 12 hours and then repeat the charge cycle.

BTW, best to charge each battery separately, just in case one battery is recoverable and the other may not be.

Tim, does the same general principle apply to Optimas? I saw my D2 yesterday for the first time since Christmas and the Yellow top is dead flat. I have a CTEK 5 also.

I had a few very flat agm batteries. My Ctek charger is a 20 amp jobbie. I also have a little Ctek. Both would not charge them as they need a min battery voltage for the charger to detect the battery. I have used both a cheap charger or another good battery to trick the Ctek into starting the charge.

Originally Posted by johntins

Tim, does the same general principle apply to Optimas? I saw my D2 yesterday for the first time since Christmas and the Yellow top is dead flat. I have a CTEK 5 also.

Hi John, and you can only try recharging the Optima and see if it is recoverable.

My Range Rover has not turned a wheel in just under 3 years now, but I forgot to take the batteries out and after 14 months, I did so.

The cranking battery, which was just a couple of months old when the RR broke down for the final time, was at 0.7v and I managed to get it back up to a 55Ah capacity. It's a throw-away.

The Optima was also low, can't remember how low and after quite a few recharge-discharge cycles, I have it back to about 60% but it is useable for odd jobs around the workshop.

So give your Optima a few charges and see how it goes.