AGM oddities

[UNDEROVER]

Hi all.

I currently have an 800 CCA AGM battery in my Defender as the primary starting battery as I have a second in place for accessories, and about a month ago, I jumped in it in the morning and it barely had enough power to get it started.
Since that time it has operated like it was brand new up until yesterday when it didn't have enough power to even turn the engine over, again, it was first thing in the morning and required a jump start.:( I jumped in this morning and it started like nothing was wrong.

Can anyone shed some light on the possible cause of this? Is it on the way out? Does it need a top up from a decent charger once in a while? I haven't checked the alternator output as yet, but would it matter? I would of thought if it was on the way out, that a gradual lack of performance would be the case?

Cheers, Matt.

[PhilipA]

I would first look for dirty battery terminals and earths, then look to see If I had left any lights on.
If the battery recovers and is fine again, I cannot see how it is anything to do with the battery itself.
Check the resting voltage and voltage while cranking, but the fact it is AGM should not cause any difference in performance to any other lead acid battery.
In a defender an AGM should last forever, or at least its design spec which is usually 6-8 years, as it is nice and cool under the seat. That is as long as it is kept fully charged.
Regards Philip A

[drivesafe]

Hi Underover, just out of curiosity, as yesterday was Monday, had you drive your Def over the weekend or as it sounds like it’s your work vehicle, was it sitting unused since Friday.

If so, your battery may be on it’s way out and is only holding enough charge over night to start and leaving it any longer is allowing the battery to discharge.

Just a suggestion.

[UNDEROVER]

I would first look for dirty battery terminals and earths, then look to see If I had left any lights on.
If the battery recovers and is fine again, I cannot see how it is anything to do with the battery itself.
Check the resting voltage and voltage while cranking, but the fact it is AGM should not cause any difference in performance to any other lead acid battery.
In a defender an AGM should last forever, or at least its design spec which is usually 6-8 years, as it is nice and cool under the seat. That is as long as it is kept fully charged.
Regards Philip A
I checked the terminals and connections (on the battery) as well, and they are spotless and given the battery has never been used for any other application apart from starting, it has me stumped! I'll check voltage on the weekend.
I would reasonably expect 6-8 years out of it as well.

[UNDEROVER]

Hi Undercover, just out of curiosity, as yesterday was Monday, had you drive your Def over the weekend or as it sounds like it’s your work vehicle, was it sitting unused since Friday.

If so, your battery may be on it’s way out and is only holding enough charge over night to start and leaving it any longer is allowing the battery to discharge.

Just a suggestion.
I did give that some thought Drivesafe, but how do you explain the measly 2 year lifespan of a so called top line battery? If it was 5 or 6 years old I would say fair enough. Are there any inherent probs associated with AGM's? I don't know of any.

[drivesafe]

I did give that some thought Drivesafe, but how do you explain the measly 2 year lifespan of a so called top line battery? If it was 5 or 6 years old I would say fair enough. Are there any inherent probs associated with AGM's? I don't know of any.

Age has nothing to do with how long a battery may last.

I’ve come across plenty of cases where batteries have premature end, and there can be many causes including a faulty batch of batteries, something that occurred with a batch of Optima batteries a few years ago.

The other problem that regularly shortens battery life is improper use.

What brand of battery do you have?

[UNDEROVER]

The battery in question is a Deka Intimidator, 785 CCA 55AH with part number 9A34.
I must admit to having thoughts of ending up with a dud.

[drivesafe]

I must admit to having thoughts of ending up with a dud.

Hi again underover, my suggestion that it might be your battery, is just that, a suggestion, but it would pay you to get the battery load tested or if your going to leave the vehicle for a couple of days between drives, try taking the negative lead off the cranking battery when you stop and leave it off until your ready to start again.

If your battery still goes flat then, unless your alternator is dicky and not charging the battery in the first place and it doesn’t sound like that's the problem, it’s a safe bet your battery is on it’s last legs.

PS sorry about spelling your name wrong in an earlier reply

[PhilipA]

Funny, price seems to have a limited bearing on quality.

I had an Optima Yellow Top ( which cost almost $500 for a 55AH ) and it started to leak acid out of the negative terminal at 4 years of age.

I replaced it with a Chinese Absorbed Power 90AH for AFAIK $285 six years ago on the basis that if it lasted 3 years I was ahead. It is still going ( relatively) strong after 6 years in my RRC engine bay.

I do not let it get under 11.5 Volts and I have it on a smart trickle charger between trips.
But I think it is a great performance and value.
I will replace it with a Fullriver 105AH for at present $299, as they have a good reputation AFAIK.
I also had a Supercharge Allrounder die at 13 months ( one month out of warranty)with a collapsed cell. Went back to the dealer but he was gorn.
Regards Philip A

[clubagreenie]

I ended up with a dud optima, it went back to Batt World and was "reconditioned" etc twice, then replaced, a total of 4 times before they tested the rest of their stock and ended up being a dud batch.

[UNDEROVER]

Unfortunately for me, I now reside in Coffs and originally purchased the battery from Battery World in Brisbane. How are Battery Worlds back up service? I'd have to look, but I'm pretty sure it's just out of warranty.

I must admit to having reservations about paying so much for a battery in the first place, not expecting to get twice the life/performance given the purchase cost but this particular battery is quite compact and it freed up a bit of space in the already cramped location under the seat, so that swayed my decision.

Time for some legwork to get to the bottom of this.

[UNDEROVER]

After removing the battery from the vehicle and giving it a recondition charge from the ctek charger, it tested at about 750 of it's 785CCA rating which is allegedly "normal". It will be 2 years old this christmas.
Time to start looking at wiring me thinks.:mad:

[Blknight.aus]

check your alternators output for ripple.

[UNDEROVER]

check your alternators output for ripple.

Checked it this afternoon and AC current reading is 0.011 at the battery. Didn't have time to check it at the alternator. Charge rate is 14-14.1, so I guess trying to find a constant current draw somewhere in the vehicle will be the next port of call.:(