AGM Battery Problem

Submitted: Monday, Feb 27, 2006 at 20:47
ThreadID: 31222 Views:2727 Replies:8 FollowUps:16
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Hi,

I installed a 100AH AGM in the tray of my Navara (inside Battery Box, in Canopy) about 18 months ago. A trip to Fraser around that time saw everything run smoothly. However, planning a trip to Fraser again and I just wanted to check out the system for peace of mind.

I regularly check the voltage just to make sure it's being charged (usually after having been at rest for some time) and always find the battery at 12.7/12.8 volts which I believe it should be. I have not had any need (unfortunately) to actually use it for some time.

I plugged my Waeco CF-50 into it this afternoon and went out to have a look 2 hours later, only to find the battery voltage is below 11 volts and the fridge isn't running. I am not sure what to make of this, is my battery dead?

My first thought is that I may be overcharging it and I've killed it. It's connected through a battery isolator kit that I bought from Jaycar and around 6 metres 8B&S cable. I know that charging voltage is making it to the battery when the isolator kicks in, I checked this on the weekend. Charging voltage seems to float around 14-14.4V. I do not have any smart chargers, solar or anything else, just alternator charging through the isolator.

My next step is to put an Ammeter in line with the fridge to see if it's pulling some stupid current for some reason, but I use it off AC at home occasionally and it seems to work fine.

I went down that AGM route because I thought it suited my situation really well (ie not used often enough).

If anyone has any ideas, suggested, (constructive) criticisms I would love to hear them, because I'm not sure what to think.

Thanks in advance for any help that you can provide.

Murph
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Reply By: roofscooter2 - Monday, Feb 27, 2006 at 21:34

Monday, Feb 27, 2006 at 21:34
Murph i think you need to have it fully charged (battery charger ) & need to keep it fully charged more often.Mine are in camper van & kept charged via solar panels all the time.hope it helps,Bob.
AnswerID: 157381

Reply By: Derek from Affordable Batteries & Radiators - Monday, Feb 27, 2006 at 21:40

Monday, Feb 27, 2006 at 21:40
It seems you have had the battery on stand by for a long time and may need a good charge. Your daily driving habits may not be enough to keep the battery at its peak. Best to get a good quality 3 stage charger and cycle the battery for at least 2 days before testing it again.

Regards Derek.
AnswerID: 157383

Follow Up By: murphnet - Monday, Feb 27, 2006 at 21:52

Monday, Feb 27, 2006 at 21:52
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
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FollowupID: 411653

Follow Up By: Derek from Affordable Batteries & Radiators - Monday, Feb 27, 2006 at 21:57

Monday, Feb 27, 2006 at 21:57
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.
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FollowupID: 411658

Follow Up By: murphnet - Saturday, Mar 04, 2006 at 08:04

Saturday, Mar 04, 2006 at 08:04
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.
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FollowupID: 412901

Follow Up By: Derek from Affordable Batteries & Radiators - Saturday, Mar 04, 2006 at 08:37

Saturday, Mar 04, 2006 at 08:37
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.
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FollowupID: 412910

Follow Up By: Mike DiD - Saturday, Mar 04, 2006 at 12:04

Saturday, Mar 04, 2006 at 12:04
"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

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FollowupID: 412975

Follow Up By: murphnet - Sunday, Mar 05, 2006 at 12:02

Sunday, Mar 05, 2006 at 12:02
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

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FollowupID: 413181

Follow Up By: Mike DiD - Sunday, Mar 05, 2006 at 12:16

Sunday, Mar 05, 2006 at 12:16
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
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FollowupID: 413182

Follow Up By: Derek from Affordable Batteries & Radiators - Sunday, Mar 05, 2006 at 13:22

Sunday, Mar 05, 2006 at 13:22
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.

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FollowupID: 413186

Follow Up By: murphnet - Sunday, Mar 05, 2006 at 14:39

Sunday, Mar 05, 2006 at 14:39
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
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FollowupID: 413198

Follow Up By: Mike DiD - Sunday, Mar 05, 2006 at 14:59

Sunday, Mar 05, 2006 at 14:59
"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.
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FollowupID: 413202

Reply By: brett - Monday, Feb 27, 2006 at 21:48

Monday, Feb 27, 2006 at 21:48
If you've been driving every day and not used it it's unlikely that it's not charged, but best to stick it on a proper charger for a few days and try your fridge again. If you do alot of driving every day there is a possibilty you overcharged it. An AGM battery really doesn't like floating above 13.8V for any length of time, a few hours here and there shouldn't hurt it but continually at 14.4V is definately no good.
AnswerID: 157385

Follow Up By: murphnet - Monday, Feb 27, 2006 at 21:55

Monday, Feb 27, 2006 at 21:55
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

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FollowupID: 411656

Follow Up By: brett - Monday, Feb 27, 2006 at 22:25

Monday, Feb 27, 2006 at 22:25
the 13.8V is a float voltage so that's 24H by 7days, 14.4V for 30 minutes shouldn't really be a problem
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FollowupID: 411667

Reply By: Harrow - Monday, Feb 27, 2006 at 22:17

Monday, Feb 27, 2006 at 22:17
Hi Murph

I am having a similar issue with a Lifeline 100 AH AGM GPL27, installed for 11 months. (purchased Feb 2005) ?

Mounted in a 100series as an Aux , veh driven 4 days a week 45 min AM and PM and 3 stage charged every 2 months

Have had a warranty claim for 3 weeks now with no resolution.

What brand was the AGM batt. Dud batch ?

begining to think AGM's not suitable for this application ?.

am investigating further will advise outcome

Harrow

AnswerID: 157395

Follow Up By: murphnet - Monday, Feb 27, 2006 at 22:52

Monday, Feb 27, 2006 at 22:52
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
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FollowupID: 411677

Reply By: Mike DiD - Tuesday, Feb 28, 2006 at 02:35

Tuesday, Feb 28, 2006 at 02:35
Another possible problem is over-discharging, although even if you discharged it 100%, you should still get 200 discharges out of an AGM (400 cycles for 50% discharge).

If you are using 40 amphours every day, you should charge it every day.

The Jaycar Isolator does have high internal resistance - good for Deep Cycle Wet cell, but unnecessarily slows down charging of an AGM.

Mike
AnswerID: 157440

Follow Up By: murphnet - Tuesday, Feb 28, 2006 at 06:48

Tuesday, Feb 28, 2006 at 06:48
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
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FollowupID: 411731

Reply By: murphnet - Tuesday, Feb 28, 2006 at 07:12

Tuesday, Feb 28, 2006 at 07:12
I've got another thing to add, this has me confused even more.

After my initial post last night I decided to go and check that charge was making it to the battery (again), so I drive the car around the block (about 1km) when I cam back I checked the voltage, around 14 volts with car still running. So I turned it off and I plugged in the fridge. I watched the voltage drop slowly from 13, 12.9, 12.8 etc until it dropped below 11 volts 5 minutes later, I guess this is what is to be expected.

This morning, I decided to go and quickly check the voltage, not sure what I was expecting, but I see that the voltage on the AGM is now reading 12.76 again, around 10 hours later. I am still going to do the recharge as suggested. I do find this very confusing though, obviously I have many things to learn but obviously just checking the voltage does not indicate all is well.

Murph
AnswerID: 157448

Reply By: Tellem Bugrem - Tuesday, Feb 28, 2006 at 16:32

Tuesday, Feb 28, 2006 at 16:32
G'day Murph,

My understanding of AGM Batteries is that they are not supposed to be charged directly from an alternator, which puts out about 17 volts. There has been a lot of discussion on the pros & cons of AGM and Gel Cel batteries on the
www.bushtrackerownersgroup.asn.au
site (Public Forum), and I'm sure if you posted your question there you would get the full picture.

Bushtracker now install batteries which are a combination of the Gel Cel technology and the AGM technology. (I have been referring to the combined technologies as GGM). Bushtracker are the exclusive Australian agents for them. These batteries are designed for charging by solar, through the Bushtracker specifically calibrated 240v charger that comes with the van, or via a 6mm hot wire from the tow vehicle's alternator where the distance from alternator to battery is such that there is sufficient voltage drop (to about 12.8v) for safe charging of the battery. Using the AGM or GGM batteries as starter batteries or auxilliary batteries in the tow vehicle is NOT recommended.

I hope this is of some help, and, I would recommend you post a question on the BOG site as there are people there who have had extensive experience with AGM's, Gel Cel's and GGM's, and I'm sure you will get the answers you need.

Cheers.......Rob

AnswerID: 157560

Follow Up By: Mainey (WA) - Tuesday, Feb 28, 2006 at 17:08

Tuesday, Feb 28, 2006 at 17:08
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.
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FollowupID: 411849

Follow Up By: Mike DiD - Saturday, Mar 04, 2006 at 11:56

Saturday, Mar 04, 2006 at 11:56
"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.
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FollowupID: 412973

Reply By: Steve M - Tuesday, Feb 28, 2006 at 22:29

Tuesday, Feb 28, 2006 at 22:29
I have heard (unconfirmed as yet) that there can be an overcharging (cooking) problem when charging certain batteries with a standard car alternator.

It is my understanding that AGM's (and possibly some std SLA's) are charged at a lower voltage than standard flooded lead acid batteries possible related to the reduced internal resistance. This seems to also be a safety factor to stop the sealed batteries from gassing (bubbling), building up pressure and rupturing the case.

An indication that there is some justification for this is that some solar regulators have a Normal/SLA selection option which I think changes the charge voltage.

As I am about to purchase some aux batteries any additional infor on this would be appreciated

Steve
AnswerID: 157681

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