I have had no issues with my mixed bank of flooded 6v and 12s. I have a pair of Interstate GC2-XHDs, a pair of Exide 135s, and two Trojan T-1275s all banked. They are wired as two big 12s (4-6s + 2-12s)for loads and charging.So I am looking at if any of those battery sets gets too weak (all from 2011) I might swap in an AGM or two. I have one 12v 100AH AGM I use elsewhere for now but could get another same kind to make a 200AH set. Looking at the specs, I see the charging voltage for the Trojans is 14.8v and the AGM wants 14.5-14.9 The 6s are happy with 14.8 too.Floating specs are also similar.time2roll says you can float dissimilar batts because the float voltage covers all sins, unlike when they are all connected but not on a float, when all sorts of things go wrong amongst them. Seems to be true for my existing mixed bag of a bank. Working great for a few years now :)I wonder about the higher resting voltage of the AGM(s) though. When camping and noting the AHs down on the Trimetric vs the "morning voltage" of the bank, would they no longer "match?" With the lower R of the AGM I am also wondering if they will take more than their share of the amps in, even if the wiring is "balanced" But then the others might catch up before the charge is stopped?What could possibly go wrong?----Thanks.

When not actively charging, flooded and AGM will charge at slightly different rates. Depending on the controller in use, one or the other will probably come up a few percent short.When discharging or just sitting, the voltage will tend to equalize if they are in parallel, as the higher voltage one(s) send a little current to the lower one(s).While not recommended, I think I've heard of a couple of people who have done it more or less successfully.My opinion is: one should not scrimp on things like this unless their budget makes it REALLY necessary. It often ends up being more expensive in the end anyway.

A lot can go wrong. First, Quality AGM's like the Lifeline brand limit charging voltage at 14.4 volts. 14.8 is too high. Gel batteries, before AGM replaced them, could only handle 13.9. Best way to introduce different types of batteries, is too bank them with a Marine Battery selector switch. A single battery charger would only charge each bank selected. Your charger should have settings for AGM and Flooded. You need 2 chargers, unless you switch the charger every time to the other bank. I sell high quality chargers and batteries, and sell 20-30 batteries a week. We cannot, per manufactures, warranty any battery charged above 14.4. The melted plates will tell the story.

I have two banks, a flooded and an AGM bank. They have been used, charged together, and floated as one bank for a couple of years. I do have selector switches to separate them but don't see the need. My solar controller is set at 14.8V for bulk charge and 13.6V for floating. It is temp compensated so voltages vary between seasons.

Thanks westend, it seems to be as I suspected. One thing is I would rather have the AGMs inside the rig where it is warm and they keep their AHs but the floodeds have to stay out in the cold, so I would have to invent some wiring access to keep them close together. Hmmmm.drmopar, you should read the Trojan charging specs.

If you're going to spend the money why not just get a complete set of matching batteries?

Mixing AGM and Flooded in a Bank ? | Good Sam Community

wa8yxm
Explorer III
Jan 29, 2017
You should be good for a few more years on those batteries.. My Interstates made it 9 years.

The AGM's I had however did not last 5

For this reason I recommend AGAINST AGM batteries.

That said. the charge profiles are very slightly different, Most of the experts I trust say they are close enough to mix.. But all of us caution agains mixing battery types.

I really do not like AGM's though, low value for your money, Flooded wet cells are far more economoical.
The_real_wild1
Explorer
Jan 29, 2017
If you're going to spend the money why not just get a complete set of matching batteries?
BFL13
Explorer II
Jan 29, 2017
Thanks westend, it seems to be as I suspected. One thing is I would rather have the AGMs inside the rig where it is warm and they keep their AHs but the floodeds have to stay out in the cold, so I would have to invent some wiring access to keep them close together. Hmmmm.

drmopar, you should read the Trojan charging specs.
westend
Explorer
Jan 29, 2017
I have two banks, a flooded and an AGM bank. They have been used, charged together, and floated as one bank for a couple of years. I do have selector switches to separate them but don't see the need. My solar controller is set at 14.8V for bulk charge and 13.6V for floating. It is temp compensated so voltages vary between seasons.
drmopar
Explorer
Jan 29, 2017
A lot can go wrong. First, Quality AGM's like the Lifeline brand limit charging voltage at 14.4 volts. 14.8 is too high. Gel batteries, before AGM replaced them, could only handle 13.9. Best way to introduce different types of batteries, is too bank them with a Marine Battery selector switch. A single battery charger would only charge each bank selected. Your charger should have settings for AGM and Flooded. You need 2 chargers, unless you switch the charger every time to the other bank. I sell high quality chargers and batteries, and sell 20-30 batteries a week. We cannot, per manufactures, warranty any battery charged above 14.4. The melted plates will tell the story.
Sam_Spade
Explorer
Jan 29, 2017
When not actively charging, flooded and AGM will charge at slightly different rates. Depending on the controller in use, one or the other will probably come up a few percent short.

When discharging or just sitting, the voltage will tend to equalize if they are in parallel, as the higher voltage one(s) send a little current to the lower one(s).

While not recommended, I think I've heard of a couple of people who have done it more or less successfully.

My opinion is: one should not scrimp on things like this unless their budget makes it REALLY necessary. It often ends up being more expensive in the end anyway.

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