Marine Electronics Forum - Is it okay to mix battery types???

I need to replace my house battery and would like to get a Sears AGM as a replacement. My engine batteries would remain maintenance free lead acid and are switched separate from the house battery. I don't know if having different styles of batteries will cause any conflict within the systems. All the batteries negative terminals are linked together and the positives go to the respective switch terminals. When both switches are on there is a link that provides power to the house bat for charging and that is the part I am worried about. I'm not sure if the AGM makes any difference besides better performance and durability. I do understand there is a different charging requirement between the to types and would get a higher amp charger to accommodate the AGM. Any insight is appreciated. Thanks

You'll get all sorts of opinions here ....personally, if all the batteries test out healthy, I wouldn't have any problem with it at all.

An AGM battery is a lead acid type. A valve regulated type whos cells are not flooded.

All that I have read leads me to believe that AGM charge rate requirements are more or less equivalent to flooded lead acid type batteries.

Your engines generator does not know or care what type of battery is connected. All it knows to do is to try and maintain XYZ output voltage at the regulator/rectifier within the limits of its current output capability.

Others will have different opinions/positions.

I may be in the minority on this, but AGM's are a waste. I bought (2) group 29's and (2) 31's last season. They seem to be very finicky on how they take a charge. While the 29's did not lose a significant charge over the winter, the 31's where down to 6 volts and don't seem to be coming back up regardless of a trickle charge, blasting with the big charger, running it with another "good" battery for a bit or whatever. I would go with it was a bad battery, but to have two crap says something else. I am also getting a voltage drop when I start my motors, which shuts my electronics down. I never had these issues with my Deka's, and they are a hell of a lot cheaper!

No idea what your problem is, but they work well for a lot of people. I've had eight over the past seven years (replace at 4 yrs) and never had one go bad. so look inside to see what's up with yours.

Ridiculous to make blanket statements about any single product based on one single experience. Also the idea than AGM is finicky just doesn't hold either.... for the people I know that use just the standard guest or Marinco or Charles charger in a standard lead acid position and again have no problems.

No idea what your problem is, but they work well for a lot of people. I've had eight over the past seven years (replace at 4 yrs) and never had one go bad. so look inside to see what's up with yours.

Ridiculous to make blanket statements about any single product based on one single experience. Also the idea than AGM is finicky just doesn't hold either.... for the people I know that use just the standard guest or Marinco or Charles charger in a standard lead acid position and again have no problems.

I have no idea what my problem is either...thus why I said I am in the minority on this. I have heard great things, just not seeing it. It seems like for the price difference, I shouldn't have to figure it out. At least when a regular wet cell craps out, it does not hurt as much to replace. Again just my .02.

It sounds like I should be okay to make the upgrade and your opinions are inline with what I was thinking. We have been really hard on the house battery and depleted it a few times and that is what wounded it. I'm just looking to replace it with something that may last a bit longer and survive better when abused. The Deka batts in the boat now have done their job well and the house batt failing is not it's fault. I just hope to increase the time it takes to draw the house battery down.

Now if the AGM dies prematurely like mentioned aren't the warranties much longer to help offset the initial cost of buying?

I had two 31 series AGM batteries that lasted two years and craped out, returned them to the place I bought them, so here is their story, I have a Xntrex 3000 watt inverter/ charger that charge at 40amps with two 15amp echo charge output, my house batteries (4six volt batteries, two banks) are hooked to the 40amp charge and my starting batteries(agm's) are hooked to the echo charge, they claim the agm's must charge at 40amps or better, if not their life span will be shortened.

I had two 31 series AGM batteries that lasted two years and craped out, returned them to the place I bought them, so here is their story, I have a Xntrex 3000 watt inverter/ charger that charge at 40amps with two 15amp echo charge output, my house batteries (4six volt batteries, two banks) are hooked to the 40amp charge and my starting batteries(agm's) are hooked to the echo charge, they claim the agm's must charge at 40amps or better, if not their life span will be shortened.

I had heard about the 40 amp requirement and am going to get a charger that would have the correct amps. Did they warranty them for you or was the difference in amps a way out of the warranty for them?

I had heard about the 40 amp requirement and am going to get a charger that would have the correct amps. Did they warranty them for you or was the difference in amps a way out of the warranty for them?


I did not want to change my inverter/charger set up, so they sold me two 31series regular flooded cell batteries at a substantial discount.

You should never mix battery types or ages in the same bank. Different impedances will cause problems.

You can have AGM's on the house bank and flooded on starting banks.

You can have AGM's on the house bank and flooded on starting banks.

That is what I did. I replaced the house battery but left the 2 engine batteries. Later when they require replacing I will change them at the same time. Thanks everyone for all the input.