AGM Battery under bonnet

Submitted: Wednesday, Feb 07, 2007 at 19:58

ThreadID: 42092 Views:11101 Replies:12 FollowUps:6

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Salties

Hi All,

Recently there was a post pertaining to AGM batteries under the bonnet that I also posted on and I to would like some feed back on anyone that has had any similar experience that I am currently facing.

I had previously had a 115 amp/hr Trojan battery that are regarded as one of the best deep cycle batteries manufactured in USA.

I had only a life of about 2 years tried to do all the right things but failed to get a lengthy life out of the battery.

I have a 25 amp C tek battery charger and also utilise 130 watts of solar on occasions.

I liked all the attributes of the AGM batteries but the cloud over putting them under the bonnet deterred my initial, however lots on this forum have had great success since.

The Trojan that I had, always made a mess on top of the battery with the acid and I had to always fill up with distilled water, much more then I would have imagined.

I have a 90series Prado 3Ltr T/D.

The AGM battery that I had purchased is a fullriver 120 amp/hr which took a little modifying to the tray to fit as the battery is a bit larger then the Trojan that I had and so heavy.

Had the battery in for a week travelled from Sydney to Tamworth and popped the bonnet the next day and the AGM is about three months pregnant.

Yep it has bowed on both short ends, one end being against the guard the engine side though is bowed greater.

The battery placement on the Prado is to the rear of the passenger head light on the opposite side of the turbo.

The manufacture, who I know well requested for me to check my charging system as they were more inclined to think this was a charging issue as the batteries they assume would handle about 100 degrees C.

He had also viewed the Trojan battery that I had previously and at the end looked very messy and not so healthy.

The top had melted slightly to the form of the top bracket, looked like the battery had cooked a bit.

The charging system is a Piranha 150 mk 2 and the Auto electrician felt that the charging is fine, I think it was reading about 13.6volts and the amp were under 5.

Spoke to some others and they seem to think it may be more of a heating problem under the bonnet. It does seem warm when you pop the bonnet and I had recently had some temperature issues with the Prado but not to a bad stage when the battery bowed. Has anyone else had this happen. I have heard that particular vehicles have more heat under the bonnet then others and thought that the prado was not one of these.

The supplier will re issue me with another battery as I have only had this for a few weeks and finding it hard to clearly pin point what actually is the problem or weather it was just faulty.

I am contemplating in making a heat shield prior to replacing the battery if this will eliminate this reoccuring. Any suggestion on the best method for the shield and feed back on similar experiences would also be appreciated.

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Reply By: Mainey (WA) - Wednesday, Feb 07, 2007 at 20:19

Wednesday, Feb 07, 2007 at 20:19

With the battery sitting behind the headlight it would/should be in the coolest part of the engine bay and this is the desired position (in engine bay) as batteries, as we know, don't like heat generated by the engine.

The other choice is out of the engine bay, this takes up some room but definitely prolongs the life and also the performance of all types of batteries.

It's my belief that if you get too much heat on your battery, so will ALL drivers of the same vehicle.

AnswerID: 220463

Reply By: Sand Man (SA) - Wednesday, Feb 07, 2007 at 20:22

Wednesday, Feb 07, 2007 at 20:22

Heat shield is an excellent idea.
Sounds like an overheating problem to me.

As the battery heats up the contents inside expand and in the case of your wet cell battery, it leaked. The AGM being sealed, can't leak so it becomes "pregnant".

A heat shield can be made out of a sheet of aluminium.
Basically it should form a barrier between the battery and whatever heat source is "cooking" it. Either the Turbo, or the exhaust manifold would be my guess.

Try placing a thermometer close to the battery and see how hot it is really getting under the bonnet. One of those Vacola preserving type thermometer with the metal backing would be ideal.

Bill

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AnswerID: 220464

Reply By: ingo57 - Wednesday, Feb 07, 2007 at 20:52

Wednesday, Feb 07, 2007 at 20:52

seen the same thing happen with a red top optima battery 2 years ago and is still running fine.

AnswerID: 220468

Reply By: RustyHelen - Wednesday, Feb 07, 2007 at 21:22

Wednesday, Feb 07, 2007 at 21:22

Hi
So can anyone tell me why my main battery (in petrol Paj NM) is OK but aux battery which sits slightly further from motor also overheats (apparently) and spits the fluid out the top?? Both are lead acid types and same manufacturer. Why doesn't the main do it?
Rusty

AnswerID: 220479

Follow Up By: brett - Wednesday, Feb 07, 2007 at 23:46

Wednesday, Feb 07, 2007 at 23:46

First thing to check is the fluid levels, if the aux is overfilled it will spit fluid out, apart from that if the batteries are the same there is no reason for them to behave differently. It is possible if the batteries are different, the Pajero comes standard with a calcium battery which has a higher gassing point than a standard lead acid. The Pajero runs a fairly high voltage on the regulator, it is temp compensated but will generally sit around 14.2v. What sort of batteries are you running and what isolator.

FollowupID: 481098

Follow Up By: junior - Friday, Feb 09, 2007 at 01:17

Friday, Feb 09, 2007 at 01:17

in addition to other suggestions...
eventhough aux batt is further away from engine than original, heat may be getting 'pumped' onto aux batt from radiator- this happens in my fourby- I have had to install heat shielding for this very reason.

FollowupID: 481360

Reply By: Salties - Wednesday, Feb 07, 2007 at 21:50

Wednesday, Feb 07, 2007 at 21:50

Yeh Sand Man I had a similar thought about placing a thermometer to actually see the temps. I have a thermometer permanently in the car on the centre console that runs a long lead which I normally place the probe in my fridge when camping, so I can monitor while travelling. I might just run it under the bonnet for a day or so to evaluate what sort of temperatures I am getting.

Also interesting comments from Rusty Helen I was aware that the acid batteries are vented and therefore release their pressure but must also admit I have never had any problems either from the main battery spilling any acid, may be the deep cycle batteries with thicker plates absorb more heat, don't know?

AnswerID: 220487

Follow Up By: Member - Gadgets (VIC) - Wednesday, Feb 07, 2007 at 22:09

Wednesday, Feb 07, 2007 at 22:09

Hi Salties

I have the same vehicle and have problems with auxillary battery leakage as well. did not think it was due to heat but could well be - I remember someone saying the Prados run very hot.

FollowupID: 481073

Follow Up By: Member - Roachie (SA) - Wednesday, Feb 07, 2007 at 22:53

Wednesday, Feb 07, 2007 at 22:53

G'day Salties,
Not sure what sort of thermometer you have, but most of the "INSIDE/OUTSIDE" ones only measure up to about 60oC, so I don't think the idea would work too well.....
Cheers
Roachie

FollowupID: 481088

Reply By: warthog - Wednesday, Feb 07, 2007 at 22:33

Wednesday, Feb 07, 2007 at 22:33

"the battery is a bit larger than the trojan I had and so heavy". I would also be worried about the battery tray eventually tearing the inner guard apart due to the extra weight.

AnswerID: 220494

Reply By: Gerhardp1 - Wednesday, Feb 07, 2007 at 23:11

Wednesday, Feb 07, 2007 at 23:11

I am currently using a 100AH AGM battery under the bonnet of the Jack. It's the only battery in there, not a second one.

I have been using it for 9 months now and it's still perfect, no signs of heat problems. Charging voltage must be OK, the voltmeter shows 14.0 volts while driving. We've had 40 degree days in Vic lately and there has been no effect on the battery driving in those temps.

When your autolec checked your charging voltage, was the battery already bulging - if yes, the reading would almost certainly be false on the low side caused by increased resistance from the stuffed internals of the battery.

It's quite possible that you are overcharging - when you get the replacement, test the charging volts straight away. You may have a faulty Pirhana thingy which is somehow allowing the alternator to feed overvoltage into your aux battery while the main one is OK.

AnswerID: 220500

Reply By: Muzzgit [WA] - Thursday, Feb 08, 2007 at 00:04

Thursday, Feb 08, 2007 at 00:04

Not the same battery, or the same car, but I have just had the misfortune of an aux battery leak acid all over the place.

So far has cost me $170.00 for a new Exide Extreme. $250.00 for panel shop to remove - paint - refit everything on the left side under the bonnet, including the chassis. $40.00 to have the battery tray blasted and powder coated and the last bit is the rubber shield between the chassis and guard that stops crap getting splashed into the engine bay from the front tyre, which Nissan wants 100 bucks for. I think a visit to Clark Rubber and to Bunnings for some tek screws is in order.

CAR...2000 GU patrol 3.0TDi
Battery...N70ZZ sealed "expanded calcium" with a Redarc isolator.

In this car the aux battery is on the same side as the turbo, and not too far away from it either.

I don't think it is an overcharging thing for me. The starting battery never seems to be fully charged, yet starts the car faultlessly, winter or summer.
Starting Battery...Amaron N70ZZ calcium battery.

The battery I had there before was an N70ZZ wet cell deep cycle. It lasted less than 3 years.

A good mate of mine had an N70ZZ sealed calcium battery fail after less than 18 months. It simply went dead overnight and would not take a charge at all after that. Yes all the questions about lights being left on were asked, and, after first getting all defensive, he thought about it and went over things and is certain no lights were left on.

I'm not sure sealed batteries are the way to go, nor am I convinced that calcium batteries are much chop either, which is why I went back to a good old wet cell lead acid type, and a brand I have heard very good reports about on this forum.

AnswerID: 220507

Reply By: 62woollybugger - Thursday, Feb 08, 2007 at 10:12

Thursday, Feb 08, 2007 at 10:12

I can't see how it could be an overcharging problem. The Piranah is only a switch that connects & disconnects the auxiliary battery to the charging system. If it was overcharging, then both the main & auxiliary battery would be overcharging.

AnswerID: 220544

Reply By: Member - Alastair D (NSW) - Thursday, Feb 08, 2007 at 12:29

Thursday, Feb 08, 2007 at 12:29

salties,
i have a 100AH AGM aux under the bonnet in a Pajero. It does get warm but so far is ok.

A heat shield is a good idea but you preferably need to make it from a material that has poor heat conduction but does not melt. A piece of aluminium will help a little, but once it gets hot it will reradiate the heat as if it was not there. Metal sheet is really only good if you are blocking a really hot heat blast from a turbo or exhaust. If that is the case then I think the battery needs to be elsewhere.

The main battery has a factory plastic heat shield and I managed to get a similar bit of material from a truck wrecker.

I hope Murphy is not reading this!

alastair

AnswerID: 220558

Reply By: Salties - Thursday, Feb 08, 2007 at 20:55

Thursday, Feb 08, 2007 at 20:55

Thanks all for the suggestions.

I get the feeling it is more of a heat problem then the charging, I will give it some strong thoughts pertaining to the material that I will use as a shield. See how we go. By the way any one with same model prado realy know what the black plastic shroud behind the head light is realy for as maybe removing this may help slightly.

AnswerID: 220638

Follow Up By: Member - Phil G (SA) - Thursday, Feb 08, 2007 at 22:43

Thursday, Feb 08, 2007 at 22:43

Salties,
#1 The black shroud directs fresh, cool air into the front LHS mudguard where the air intake is located. If you have fitted a snorkel, then its not needed.
#2 I owned two TD 90series Prados. I don't believe they get unusually hot under the bonnet. I have not seen or heard of this problem with wet cell batteries.
#3 I haven't mentioned this so far, because I'm not sure whether its true, but its possible that the AGM is warped from being overcharged. The output of your Prado's alternator is regulated at 14.2-14.4volts. AGMs have a very low internal resistance, so will accept high currents, and underbonnet temp may be say 80 degrees. If you put these together, I'd suggest that your battery will be being recharged at a lot mare than the 24amps max that is mentioned in your battery's data sheet. Not sure of the best solution, but a heat shield will help - don't make it out of metal though (short-circuit risk) - I've used a plastic battery box cut into a shield in the past, or even something as simple as cardboard or ply.

FollowupID: 481307

Follow Up By: Member - Phil G (SA) - Thursday, Feb 08, 2007 at 22:48

Thursday, Feb 08, 2007 at 22:48

One last thought: Is there any possibility that your AGM's positive terminal has been accidentally shorting on the bonnet - this can happen when the battery sits a bit high, the terminals are out wide and the pos is on the mudguard side. Do you have a guard over the pos terminal?
I had a fire caused by this once on a 60series. That battery sure did warp :-))

FollowupID: 481311

Reply By: RustyHelen - Thursday, Feb 08, 2007 at 21:08

Thursday, Feb 08, 2007 at 21:08

hi Brett and others
Main battery is no longer a Mitsu one-- changed first about 2 years ago and again late last year to a not Mitsu brand.... Both "Diamond" class batteries failed at 23-25 months.
Main and aux are both same brand from the local auto elec but can't remember which and not fussed about putting down the drink, opening garage, etc etc, Piranha make and installed controller.
Spitting out the fluid was not overfill issue as when I found the problem just recently (aux battery did not run the fridge as long as usual) it was dry as. Probably cactus now but have topped up and operating OK so far. I reckon it was overheating/physical issue after a few bouncy tracks and hard work for the vehicle late last year. But that is an uniformed guess.
Rusty

AnswerID: 220644