Mix AGM & wet-cell batteries?

[two2go]

I'm toying with the idea of replacing my wet-cell chassis starting battery with a Sears AGM battery for long life and no maintenance in a relocated place of limited access. I would use the space under the step where the chassis battery was to add a third 12v deep-cycle wet cell battery for 50% more house battery capacity.

What I wonder is if the charging systems (engine alternator and Xantrex Freedom 458 inverter/charger and Morningstar PWM solar controller) will work OK with both types of batteries? Basically, can an AGM battery be substituted for a wet-cell battery? I'm clueless about how both sets of batteries get charged, yet work independently, but they seem to.

[adehaan86]

Never mix batteries. Same brand same model same everything. Anything different you will burn up batteries like it's your job.

[GaryKD]

Hi two2go,
I think your questions are about the various charging sources. The alternator is no problem. The charger/inverter should be no problem. It is a 3 stage smart charger. It may have settings you'll need to check the manual. If there are no settings it will work fine with the AGM battery. The solar charger is another animal. I see no reason why it would not work quite well with an AGM technology battery. However, solar is not my skill so another member might have additional information.

From a charging point of view the differences between wet cell and AGM are their charge acceptance rates and their maximum top off charge. The AGM will accept a very fast charge rate. The AGM top off charge is 13.8 VDC at 70 degrees F. The wet cell top off charge is 13.6 VDC at 70 degrees F.

[wa8yxm]

Though AGM's are "Maintenance Free" they are not all that long life when compared to other batteries.. The best you can hope for is a match for quality flooded wet cells at 1/3 to 1/2 the price of AGM's.

I'd re-think

[Shadowcatche]

Deep Cycle Battery FAQ one of the best sources of information

[Rick Long]

I have the Sears AGM for my starting battery and 2 Trojan T105's for my house batteries. The Sears has a 100 month warranty, with 60 month (5 yr) direct replacement. I've had this set up for 3 years now and no problems at all... That AGM cranks my V10 with ease.

[UFO Pilot]

I have a wet cell for the chassis and AGM's for the house, no problems with either of them.

[Gary RVRoamer]

It's true the general rule is "don't mix different types or ages of batteries". Liek most general rules, it is intended as advice for an average person in unspecified/unknown conditions. However, if you do understand the condition of your batteries, their capacity and charge rates and they are reasonably the same, yes you can successfully mix tyes and ages of batteries.

I've used a 12v Lifeline deep cycle AGM with a pair of 12 month old 6V GC batteries with no problem at all. They were connected to an Iota DLS 90 charger with the Charge Wizard, so it was a smart, 3 stage charger. Ran them 4 years that way and then traded the coach with the pair of 6V's still going strong. I took the Lifeline 12v out when I traded the coach and installed it in my bass boat, where it was used another 3 years. I still have it in my shop, were it serves as a 12v source for testing 12v devices. Doesn't ho;d a reliable charge any more, though.

[TQ60]

Ok, creative is a stretch, but here we go.

Telco AGM batteries are manufactured in such a manner as to be approved for use inside switch rooms, in fact you could carry one in your lap on an airplane trip...you get the idea, they are SAFE AND DESIGNED for indoor use.

They also are designed for a 10 year installed life as FLOAT service, so if used fro standby 10 years, if used for deep cycle then not so much, but there are different designs currently where you still could find a suitable indoor rated deep cycle AGM/VRLA battery.

Once this is done, we get creative.

You need a spot where the environment is better such as inside the MH, also one that is never used.

So the drawers under the dining area are not as long as the bench because they hit the other side, what is behind the drawer? A lot of room.

We have enough room to place a few on each side, the 8 batteries I have waiting in the shop will be going there when time comes.

So it will add about 500 or so amp hours to the existing batteries without consuming any existing usable space.

I will add a specific charger for these batteries only, a simple battery maintainer/trickle charger will be fine as the charge can take days in our case.

Have not yet decided how to use them yet, possibly secondary backup for primary coach batteries, will do the design down the road.

[Crabby Mike]

Quote:

Originally Posted by adehaan86 Never mix batteries. Same brand same model same everything. Anything different you will burn up batteries like it's your job.

I'd agree, don't mix batteries that are part of the same "team" (like your house batteries). However, your house vs. chassis batteries are a different matter entirely, since they serve different purposes.

The main requirement for your chassis battery(ies) is cold cranking amps, to start your engine. Other than that, its job is very low-stress.

Your house batteries, on the other hand, are deep cycle batteries, providing power to everything in your coach while boondocking.

The only problem I see in mixing between house and chassis is the charge settings, which I understand are different for AGM's.

[Bob/Becky D - VA]

Quote:

Originally Posted by wa8yxm Though AGM's are "Maintenance Free" they are not all that long life when compared to other batteries.. The best you can hope for is a match for quality flooded wet cells at 1/3 to 1/2 the price of AGM's. I'd re-think

Could you direct me to were you got this fact. All of my research indicates the oposite.

Thanks

Bob

[Techie]

Just like the rule is to not mix old & new batteries together, I woudl only use them if they are isolated into different banks that can't normally interact with each other.

We have 4x8D AGM's for the house and 2xGrp 31 maint. free wet cells for the chassis.

Our charger (Magnum secondary bank) can be set to charge the chassis batteries after the house batteries are full and can have different under/over voltage parameters set for the chassis batteries.

[bluepill]

My thoughts:

You mention placing the battery in an area of limited access. As long as it is open to outside air (not inside your "house") the following applies. If it vents to the inside of your "house", AGM would be called for.

A standard flooded "maintenance free" battery should work well in your application, and be cheaper to buy.

It will have no problems with compatibility with your house batteries as far a charging goes.

It will not require any electrolyte level checking during its 4 to 6 year service life.

[two2go]

I appreciate all the comments. I am coming to the conclusion to go ahead with my idea of an AGM chassis battery. I have a 6 yr old maint.-free starting battery still working fine, so I hopefully have time to map out the best new location for it. It seems to be a fact that the engine charging system sends charge to the starting battery first, and then to the house batteries. I still don't understand the inverter/charger setup. The article on batteries referenced above was very informative. Thanks to all.