AGM Batt under the bonnet,good or bad
Submitted: Saturday, Feb 04, 2012 at 16:26
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GREENDOG !
As some of you now i was in the hunt for a Aux Batt and ended up getting a AGM Powersonic which i needed in a hurry as we were leaving the next day to spend a couple of days in
Mildura,now whole there the BIL had to get a starting Batt for he's Cruiser so we went out to the TJM store and whole there i told the guys i had just fitted this Batt under the bonnet and he went on to say that it won't last 12 mths because of the heat factor,so have i done my self in here and brought the wrong Batt or not,Batt Experts need to reply to put my mind a rest.cheer's GREENDOG
Reply By: Member - Captain (WA) - Saturday, Feb 04, 2012 at 17:02
Saturday, Feb 04, 2012 at 17:02
While an AGM is a good battery, it is sensitive to heat. While some have managed to get a decent life from an underbonnet AGM, it can have as much to do with location. A 3.0TD GU has its aux battery next to the turbo, a poor choice. An 80/100/200 landcruiser has it behind the headlight and more in the airflow to help keep temps down and more chance to get a better life.
Typically its the loss of electrolyte that causes the issues. An AGM (VRLA) battery cannot have any electrolyte added if it is released, unlike a wetcell battery that can easily be topped up with distilled water. But if the wetcell battery is not topped up when required, then it too will have a short life.
I run AGM's in my camper, where temps are not an issue, as I believe they are a much better design of battery. But under the bonnet I run wetcells as I can easily replace the eletrolyte by simply topping up with distilled water whenever required.
It is possible to achieve an acceptable battery life from an AGM under the bonnet, but unfortunately there are many who have not been able to do so.
Cheers
Captain
AnswerID:
476866
Reply By: olcoolone - Saturday, Feb 04, 2012 at 18:07
Saturday, Feb 04, 2012 at 18:07
In theory not a good idea.... in real life yes you can.
Under bonnet temps are not as high as you may thing, try 45 to 60 degC.
Most batteries under bonnet will be around the 50 degC.... to overcome some issues you can insulate the battery and duct cool air to it.
We have had all types of batteries fail within 18 months and we have had all types of batteries last for years.
The biggest thing is correct charge rates for the battery type and conditions.
Is you can run aux batteries outside the engine bay...... in our 200 series we have 3 x 120 amp agm mounted in the back.
AnswerID:
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Follow Up By: olcoolone - Saturday, Feb 04, 2012 at 18:09
Saturday, Feb 04, 2012 at 18:09
And about Powersonic..... they are good quality and what we use and sell.
FollowupID:
752016
Reply By: Member - Phil G (SA) - Sunday, Feb 05, 2012 at 00:17
Sunday, Feb 05, 2012 at 00:17
Greendog,
Have a look at the spec sheet for your battery:
Powersonic Spec sheet
Under the charging section, you will notice that the initial current on the 92Ah battery cannot be more than 25 amps. And the charging voltages are at 20 degrees C. If charging at higher temps, it will want lower voltages.
So, you need a way of limiting current to an AGM battery if you want a normal life. In many installations the suboptimal wiring does this nicely!
AnswerID:
476913
Reply By: The Bantam - Sunday, Feb 05, 2012 at 01:42
Sunday, Feb 05, 2012 at 01:42
Any battery will last longer and perform better in a cooler place.
The previouys poster has rasied an issue that many fail to grasp or simply ignore......many deep cycle AGM batteries have a very limited maximum initial charge current...in the order of 20 ish amps....this alone will account for premature death of many batteries, add an elivated operating temperature and the tolerance to overcharge will be much worse.
In addition lots of people install deep cycle batteries and then expect to charge them at a high charge rate.........almost every deep cycle battery will neither tolerate high dischage rates nor high charge rates.
There are also some specific heat related issues that effect som AGM batteries, such as thermal runaway....
Personally I would be running a flooded battery in vehicles, because I am not convinced of the benifits of either AGM or GELL in these situations.
Personaly I use a marine battery in both cranking and aux positions...and that would be half the price of AGM.
I like the Supercharge, Seamaster gold..it is a sealed maintenence free battery that has a a pretty solid following......what A lot of people don't know is that once out of waranty, the top sticker can be removed and the vent valves can be unscrewed and the battery can be topped up like a normal screw top battery...ya just have to be carefull not to over fill.
the going rate for a Seamaster Gold in N70 size is arround $200.
no commercial connection.
AnswerID:
476916
Follow Up By: The Bantam - Sunday, Feb 05, 2012 at 01:49
Sunday, Feb 05, 2012 at 01:49
Oh BTW.... 50C is quite hot for a battery....look at the spec sheets for a few sealed batteries and 50C will be outside the recomended operating or storage temperature range.
If you look at where most vehicles have the original battery fitted, it will be at the front of the engine bay. mostly behind the headlight opening.
Unfortunately, many second batteries are fitted furrther back in the engine bay where it is far less cool.
cheers
FollowupID:
752060
Reply By: Member - Rob D (NSW) - Sunday, Feb 05, 2012 at 10:12
Sunday, Feb 05, 2012 at 10:12
Lifeline Batteries have a Mil Spec 95 AH battery with an operating temperature range from -45C to +65.5C ($446 at Batteries Direct).
Most of the Lifeline batteries have a +50C maximum operating temperature. These come with a 5 year warranty.
Lifeline are one of the most expensive batteries, but if you look at the specifications of plate thickness, construction etc, you are getting what you pay for.
I have no connection with any supplier.
AnswerID:
476954