AGM batteries

Juggenaut · Veteran Member

AGM batteries

Craig1 · Guru

TJM fitted a Full River AGM in my Landcruiser, this is an "original Toyota " spot behind headlight, left vacant from when they went back to a single battery. The local battery agent has apparently sold plenty for this application, been ther around 10 months ok.

Dave1952 · Senior Member

I've got an AGM as the second battery in my 100 Series Cruiser.

iana · Guru

I believe the original AGM batteries were developed for the military, these were the ones that have cylindrical shaped cells. AGM absorbed glass mat. so each cell is wrapped or filled with fiberglass mat. The cells are not sealed, but have a relief valve fitted that vents to atmosphere. The military spec ones have a high relief valve setting, are designed to absorb punishment, including rude charging methods, because the cells are pressurized, the gas returns to its liquid state, and they are basicly no maintenance. However AGM batteries also come as the std square shape, and their relief valve setting is much lower, 10psi I think. So if the internal pressure rises, the valves vent, and electrolyte is lost. I feel that this is where those who advised you are coming from, the high temperatures under the bonnet may cause the internal pressure of the battery to rise and hence loose some of the electrolyte. ----- only guessing though.

darjak · Senior Member

Most battery manufacturers bring out AGM's that are suitable
for under bonnett use, just read their specs to see if they are.
I've run a 100ah Fusion there for years without any problems.

HandyWalter · Senior Member

I tend to disagree with above comments.....although I have a Yellow top as 2nd battery under the bonnet. RV daily and a few other online 4wd mags have had write ups about batteries and all say that AGM should not be placed where they have to sustain hot conditions. When driving there maybe air over the battery but when you stop the air does not flow. All have said that it is not ideal to have an AGM where heat is but then what do you use that is as good as a AGM if you have space?

rvdaily.com.au/rvd/issue028/ and www.loaded4x4.com.au/issue-002/ and www.loaded4x4.com.au/issue-003/

Mike Harding · Guru

Other than Optima I am not aware of any manufacturer of AGM batteries who specify them for underbonnet use - and Optima use a very different construction technique.

My two choices of manufacturer, Powersonic and Fullriver, both specify charging temperatures of 50C. If temperature compensated charging is applied Fullriver specify an absolute maximum of 71C but that will kill the battery in a few months or less.

Underbonnet temperatures in Australia can easily reach 100C.

In their technical manual Powersonic state it is estimated battery life is halved for every 10C above ambient.

Your money....

BAZZA44 · Senior Member

You can get dual purpose batteries such as Supercharge All Rounder, suitable for under the bonnet.

Barry

Juggenaut · Veteran Member

thanks very much all for your comments.

Warren-Pat_01 · Guru

Hello Juggenaut,
Friends of ours have a MUX - TJM fitted their aux battery which I believe is an AGM (brand, etc unknown as they are out of coverage area at the moment). It is behind the start battery almost into the firewall. It has to be removed before the fuel filter can be rpcd.

I have an 80AH AGM in the Nissan - mounted in the best place possible to COOK a battery - above the turbo charger/exhaust manifold. Batteries in the past did not last very long The one I have there now is a SSB 80AH Deep cycle AGM. It was fitted in Jan 2017 & was sold by Forbes in Toowoomba (or FNQ Battery Wholesalers in Townsville). I was told it was made for under the bonnet conditions up to 80 degrees (most batteries love temps around 25!
I added a 1/2 battery box to it - a two sided box, with 10mm insulation & silver reflection. I added a 3" rubber skirt on to of the fan housing & removed the two 8" driving lights & replaced them with a LED bar to improve air flow into the area but living in the tropics, the area still gets very HOT!

Toyota actually got something right - their batteries are mounted up the front of the vehicle, away from any heat sources!

All the best.

HandyWalter · Senior Member

Warren-Pat_01 wrote:
Hello Juggenaut,
Friends of ours have a MUX - TJM fitted their aux battery which I believe is an AGM (brand, etc unknown as they are out of coverage area at the moment). It is behind the start battery almost into the firewall. It has to be removed before the fuel filter can be rpcd.

I have an 80AH AGM in the Nissan - mounted in the best place possible to COOK a battery - above the turbo charger/exhaust manifold. Batteries in the past did not last very long The one I have there now is a SSB 80AH Deep cycle AGM. It was fitted in Jan 2017 & was sold by Forbes in Toowoomba (or FNQ Battery Wholesalers in Townsville). I was told it was made for under the bonnet conditions up to 80 degrees (most batteries love temps around 25!
I added a 1/2 battery box to it - a two sided box, with 10mm insulation & silver reflection. I added a 3" rubber skirt on to of the fan housing & removed the two 8" driving lights & replaced them with a LED bar to improve air flow into the area but living in the tropics, the area still gets very HOT!

Toyota actually got something right - their batteries are mounted up the front of the vehicle, away from any heat sources!

All the best.

Is that 25C? or 25f? same with the 80? Either that battery likes being frozen or severely cooked!!

Warren-Pat_01 · Guru

Walter, 25 degrees C is the perfect temperature for batteries. After that generally, they are on the way to dying an earlier death.

One battery I had before adding the insulated casing & increasing the air flow lasted 10 months & the sides had started to bulge - it was a good thing it died (10.5v) before blowing up!
Still my SSB battery is still hanging in so perhaps some batteries are engine temperature tolerant.

I choose to use the 80Ah batteries as they are lighter than their larger cousins. I had body cracks in my GQ due to the heavier batteries & the type of battery mount.

Juggenaut · Veteran Member

thanks for that W.P. yes Autobarn in Cairns fitted an OPTIMA battery in exactly the same place as your friends, but it is only 55a/h. so I had an auto electrician to re cable it and make it the cranking battery and have turned the original battery in to the auxillery battery which is still only a 65a/h battery, but leaves me room to put a larger size battery for my requirements. hope that makes sense.

HandyWalter · Senior Member

Warren-Pat_01 wrote:
Walter, 25 degrees C is the perfect temperature for batteries. After that generally, they are on the way to dying an earlier death.

One battery I had before adding the insulated casing & increasing the air flow lasted 10 months & the sides had started to bulge - it was a good thing it died (10.5v) before blowing up!
Still my SSB battery is still hanging in so perhaps some batteries are engine temperature tolerant.

I choose to use the 80Ah batteries as they are lighter than their larger cousins. I had body cracks in my GQ due to the heavier batteries & the type of battery mount.

Warren, 25C is fine, but then later a quote of 80 under the bonnet is mentioned. So is that 80C or have we now changed to 80F? If 80C I think you will find batteries do not like things that hot. Hence my comments which which temp are we using. Heat is the biggest killer of batteries as the electrolites start to vapour and the plates become exposed. If you have a read of the articles I have posted, they all say the same thing. But as I said, I have a AGM yellow top under the bonnet but it is right at the front of the car and hopefully does not get too "cooked".

Aus-Kiwi · Guru

Be aware some heat sink may rise when engine is turned off for short time . If this effects battery ? I have fitted an alloy shield. Directs cold air from front as well as shielding when engine is turned off . I fitted a timer to thermo fans to run a short time after turning engine off . Blows off heat build up .