AGM Battery Problem

Hi Derek,

Thanks for the response.

I drive for 30mins+ twice a day, 5 days a week, so I was thinking that this would be enough but then that was only an assumption based on no facts!

Could you please expand on what you mean by "cycle the battery for at least 2 days before testing it again"? Not sure if you mean 2 days charging or discharging or both?

I'm hoping you're right that a good charge is all it needs though. It would be an expensive lesson if I've managed to kill it.

Murph

You have already done one cycle by letting the fridge run till low voltage cut out.

Charge it up for 24 Hours on a 15 amp 3 stage charger and then cycle it again. Make a note of the fridge run time.

Do this 2 times and it should be right.

If not contact me again and we will do voltage tests.

Regards Derek.

Hi Derek (if you're still in contact with this thread),

Obivously I could go out and buy a 3-stage charger as you've suggested, but since it costs the same amount as a replacement battery I figured I'd see if I could get any improvement out of what I could get my hands on. I got a 6A 2-stage.

6 Amps seems to bring it up to charge in a couple of hours, but it's a 100AH battery? Discharging doesn't seem to be taking any longer, not noticeably anyway.

I charge it up, and put the fridge on it and watch the volts, seems to sit on 12.7/12.6 for some time. Obviously I can't watch it for too long. All I know is that every time I've checked it the voltage has been a 12.4 or above. The voltage seems to drop VERY suddenly down to below 10 at some point after that. When the load is taken off and the battery left still the voltage will climb back up to 12.7 after a couple of hours.

I feel like it's got more in it. I can put a small fluoro on it and the voltage will gradually climb, but put any real load on it and the voltage crashes.

If you've got any other ideas for me to try then that would be great. I realise I'll have to buy a charger, but for the moment buying a new battery seems like a better solution. In future I will disconnect the battery from the vehicle when not in use and charge it on a proper charger periodically.

Once it drops down to low voltage it will take at least a full day before it is back in usable condition.

A couple of hours won't do it.

Regards Derek.

"The voltage seems to drop VERY suddenly down to below 10 at some point after that. When the load is taken off and the battery left still the voltage will climb back up to 12.7 after a couple of hours.

I feel like it's got more in it. I can put a small fluoro on it and the voltage will gradually climb, but put any real load on it and the voltage crashes. "

These are the symptoms of high resistance in the wiring or fuses.

While powering a load drawing at least 5 amps, start measuring the voltage at the ACTUAL BATTERY TERMINALS, not the clamps around them. Now start moving the voltmeter probes closer to load along the positive lead, then the negative lead.

If you have corrosion inside one of the joints, you may find that the voltage drop across a joint will suddenly increase, maybe 5 minutes after connecting the laod for no apparent reason.

Mike

OK Guys,

Well I've let this thing charge for a long time now, maybe not fully charged, who knows, but surely got something into it.

I just ran the fridge with turbo on so it was drawing around 8 amps, and I figured this would cycle it well. It ran for about an hour. Voltages measured at the terminals around 12.6 straight up, gradually dropping to 12.4 across the hour (I checked it regularly). At about 58 minutes (8 Ah) that voltage went from 12.4 to below 10 and the fridge cut out, flashing red error light, once the fridge goes to erro the volts come back up 12.7 at terminals. Disconnect/Reconnect fridge, voltage drops immediately, unusable. Voltage comes back up to 12.7. Just put the fluoro on, draws around 0.6A, it has dropped it straight down to 10 volts.

Even if it was discharging faster than expect you would still expect the voltage drop more steadily wouldn't you? Not just lower gradually then drop through the floor?

I guess it's probably busted, I will stop messing with it now and leave it on the charger for the next week but I'm certainly not holding my breath. Today was just my best chance at keeping an eye on it.

Murph

It does sound like the fridge is causing an overload - do you have another way of discharging at 8 amps - say two 50 watt headlight bulbs so you can be sure it isn't the battery.

Mike

It is possible that the AGM has a dead cell. Hard to test as they are sealed. Have you tested the fridge on another battery to see if it is the fridge or the battery at fault ?

Also is there any excessive heat on the cable or connections.

It is beginning to look like the battery is at fault.

Regards Derek.

Guys,

I purposely set the fridge on turbo and to freeze because I wanted to put a pretty constant (and high) load on the battery. It also gave me an opportunity to keep an eye on it. I ran my 300W inverter driving a fan 50W fan (because I didn't have anything better to run) off it the other day and it did the same thing, it ran for about 4 hours, I guess it wouldn't have taken the whole 50W but my thought was it was a constant draw of at least a couple of amps.

I often drive the fridge off the WAECO AC power supply, and have not experienced any problems from it. I did a quick check on it through the ammeter yesterday to see what currents it pulled, just under 8A in turbo, around 4.5 in normal mode.

After an hour on 8A the cable did have some warmth in it, but was by no means hot, I realise that there is losses in this, but I'm missing 90AH!

I have got a brand new AGM, that I bought before I checked this other one out (new CT on it's way) so I will check how it goes runnning the fridge.

I've pretty much given up on this battery, but I am dissapointed with it and I'm left wondering how this new one will go. My biggest concern at this point is that I may have inadvertantly killed the battery by over/under/incorrectly charging it. Or maybe I just lucked out and got a dodgy one. Out of warranty now too of course.

My intention is to nurse the new one by only having it in the car during camping trips where it's actually being cycled and needing charging, and I will buy a 3-stage charger for charging it periodically while not in use.

All up it's been a pretty expensive way of getting out of having to buy ice! I guess I may still get away with using it to run lighting if I can get 8-10 AH out of it.

Thanks for the help and ideas.

Murph

"I often drive the fridge off the Waeco AC power supply, and have not experienced any problems from it. "

In that case it sure sounds like it's the battery. But it sure is unusual to have a battery where one cell shorts out or fails so consistently after an hour, while the other cells seem to be holding up well. It could be a manufacturing defect that has nothing to do with what you've done.

Hi Brett,

Thanks for the input.

I would say 14.4V for 30 minutes twice a day, 5 days a week for 18 months. Sounds like, in your opinion, it's not looking good.

Tony

the 13.8V is a float voltage so that's 24H by 7days, 14.4V for 30 minutes shouldn't really be a problem

Hi Harrow,

Mine is an "Absorbed Power", got it from Bias Boating, I think they were sourced from "powerdive" who appear to have moved from QLD to WA, maybe they're trying to get away from me! 12 month warranty is up now anyway.

I've only ever charged mine via alternator, so I'm going to run on charger over the next couple of days. I can borrow a 2-stage so I'll try that to see if it does anything before I invest in a 3-stage, I hope that's OK??

I'll do some cycles as suggested by Derek above and we'll see what happens.

Murph

Hi Mike,

The battery hasn't been used for basically 18 months since I first installed it, so discharging shouldn't be a problem I don't think.

Thanks for the note on the Jaycar Isolator, I might have a rethink about this component too.

Murph

Rob,
you say "Bushtracker now install batteries which are a combination of the Gel Cel technology and the AGM technology"

Fullriver and others make AGM batteries using 'gel cel technology' nothing new or exclusive there.

My advice would be to check for a loose or dirty cable connection.

"not supposed to be charged directly from an alternator, which puts out about 17 volts."

Any Alternator that puts out 17 volts at any time is seriously faulty - 14.4 volts for normal batteries or 14.8 volts for Calcium-Calcium Batteries.