AGM Battery in Engine Compartment?

[Ayrton]

Family member's C Class sounds very sluggish starting, so I ordered an AGM battery for it. It had a good coupon on Amazon, to be shipped to the door. Saved about $50 over non-AGM at auto parts stores and $100 over the AGM offerings. Many Mercedes forums and whatnot promote AGM batteries and many assume Mercedes all have AGM batteries.

However, I have studied the battery, and it clearly is flooded, not AGM. Mercedes have when the battery is installed in the cabin or trunk an AGM, not when the battery is under the hood as in a C Class.

Do you think I should refuse the battery upon delivery, or go ahead and install it?

I have read the heat under the hood of a car is not a desirable location for an AGM battery. On the other hand, Bosch claims AGM can always replace flooded batteries in any car (just a sales line to up-sell). Plus, Mercedes have a little air box above the batteries, and the external air seems to be sucked in, over the top of the battery, not sure if that might keep it a bit cooler too.

Thanks for any advice.

 

[Phishin]

I have AGM batteries sitting next to twin 454's in my boat. Never a problem. It gets HOT down in the engine compartment.

I have an AGM battery (Trojan/Deka) in my truck (SBC) and never an issue either.

When this POS OEM Honda battery finally dies in my Accord, I'll be getting a deep cycle AGM glass mat Deka battery for it too.

 

[Rand]

did you check to see if parasitic draw was merely discharging the motorhome battery? sometimes those sit for long periods.

 

[DBMaster]

I found AGM batteries lasted twice as long in the hot underhood environment of my Honda. (Optima Red Top)

Clarification: Lasted twice as long as any of the 4-5 flooded batteries I had in the car prior to the Optima.

 

[Wolf359]

How much did you pay for the battery? Normally the best price has been at Advanced Auto using one of their coupon codes. It's a little tricky now, but I'd go with an AGM so if you can refuse and get a real AGM battery, I'd do that as AGM batteries are supposed to last longer than flooded.

 

[Phishin]

AGM or Flooded.....I love Deka (East Penn) Batteries

 

[Chris142]

many jeepers including me have a agm battery under the hood.got 2 under the hood of my ford.

 

[Ayrton]

Originally Posted By: Wolf359
How much did you pay for the battery? Normally the best price has been at Advanced Auto using one of their coupon codes. It's a little tricky now, but I'd go with an AGM so if you can refuse and get a real AGM battery, I'd do that as AGM batteries are supposed to last longer than flooded.


It was AGM I ordered. I was concerned because the original in the car is not AGM, and I read heat is bad for AGM. AGM tends to come in automobiles where the battery is installed in the cabin or trunk.

I paid $106.00 for it, AGM, 94R battery.

I sure appreciate all the responses. It seems many use AGM in flooded applications. I may go ahead and keep it then, though I'm still tempted to stay with what worked for 7 years, conventional flooded battery.

Chris142 - Yes, that is one of the advantages, off roading is a great application for AGM reportedly. Smart choice there.

 

[rslifkin]

We've had AGMs and gel cells on the boat (in the engine compartment) for years. Some of those batteries have made it 5 - 7 years before getting weak enough to think about replacement. The AGM in my Jeep is now a bit over 3 years old and still going good and strong.

 

[gathermewool]

The only effective difference that I know of to cause the kind of concern you may be reading about, is that the electrolyte absorbed into the glass mat (absorbed glass mat or AGM) cannot be replaced, because the AGM battery is also maintenance free. Should the battery overheat, causing an excessive internal pressure rise, the gasses will be vented off through a regulating valve, which acts like a a relief valve (the VR, in VRLA,) depleting the volume of electrolyte in the mat, which will lower its saturation percentage - AFAIK, the mats are not fully saturated, so that a crack in the case will not cause nearly as significant of a leak as a wet battery.

So far as I know, the only real cause for excessive venting of the battery would be the result of over-charging, not normal engine compartment temperatures. With that said, there are deep-cycle AGM batteries, so I wonder what the actual charge rate would have to be to cause the VRLA battery to vent off and cause electrolyte loss.

To make a long story short, I wouldn't worry about the above. I know some AGM's have had some duds. Some say Optima isn't what it used to be, though I had an abused yellow-top that seemed to work just fine for the couple of years I had my car before giving it to my sister, even after draining it to the point where it wouldn't even turn over on a few occasions due to electrical drains. I also had a Sears AGM that gave me no issues for the couple of years I had it in another, newer Subie before I traded it due to an accident.

I'm still torn about whether to go with a relatively cheap battery (e.g., AAP Gold) or a more-expensive AGM (e.g., Diehard Platinum.)

 

[Chris142]

agm all the way! they dont gas like a wet battery does so your cables dont get eaten up. thats reason enough right there.

 

[SteveSRT8]

Originally Posted By: Chris142
agm all the way! they dont gas like a wet battery does so your cables dont get eaten up. thats reason enough right there.


ABSOLUTELY not true. They can and do vent hydrogen and if sealed up in a compartment the result could hurt someone.

Please read up on this before someone hurts themselves...

 

[Wolf359]

I have the AGM battery in the trunk of my car, it's OEM and has a 2007 date on it, still going strong, car only has 50k on it. I hope it lasts another year or two. People do report that they can last 7-10 years. Best price I've found on the H8 is around $140 or so for AGM and about $120 or less for flooded so for the price difference, I'm just going to go with AGM when the time comes.

 

[crw]

I put an AGM in my 1975 BMW 2002. This car sits a lot, and gets started every week or two. Whenever I crank it, it is loaded with power and cranks fast!

 

[Chris142]

Originally Posted By: SteveSRT8
Originally Posted By: Chris142
agm all the way! they dont gas like a wet battery does so your cables dont get eaten up. thats reason enough right there.


ABSOLUTELY not true. They can and do vent hydrogen and if sealed up in a compartment the result could hurt someone.

Please read up on this before someone hurts themselves...
according to optima they do not gas under normal circumstances.

 

[SHOZ]

They gas but the container is pressurized. Usually around a 10lb vent limit for a VRLA. Besides it's not the gases that eat up the cables, it's the acid carried out by the gases. You don't need a sealed battery to not have acid on top. That is a poor post seal on the battery doing that.

I have an 6 year old OEM battery in my Hyundai and nary a drop of acid and the cables with no corrosion.

 

[Chris142]

i live on a very rough dirt road and my cables get corroded with wet batteries.dont know if its from splashing out or bad seals. optima batteries put a 100% stop to that.

 

[TiredTrucker]

Originally Posted By: Phishin
AGM or Flooded.....I love Deka (East Penn) Batteries


Yep. Deka/East Penn makes darn good batteries. And they go under a lot of labels. Caterpillar gets their batteries from Deka. I know, I sure have hauled a lot of them from Deka plants to Caterpillar dealers over the years. Many auto parts store brands are Deka batteries. I have seen a lot of Deka batteries going to autp parts stores, under the store label.

Recently, I have grown fond of Alliance brand batteries in my commercial semi that are made by Interstate Battery.

 

[Y_K]

Here is some decent read on batteries. May be just a tad outdated, but a good starting point, well structured research by a plain fellow.

 

[SubLGT]

Originally Posted By: Ayrton
……….It was AGM I ordered. I was concerned because the original in the car is not AGM, and I read heat is bad for AGM. ……...It seems many use AGM in flooded applications. I may go ahead and keep it then, though I'm still tempted to stay with what worked for 7 years, conventional flooded battery. ……….


You should make sure the voltage regulator in the motor home has temperature compensation, and that it regulates to the voltage limits recommended by the AGM battery manufacturer. AGM is less tolerant of over charging than a flooded battery, and can go into thermal runaway.