Dual battery banks

[canesx5]

So I switched out my converter/charger this week with the pd4655 from Progressive Dynamics. I have 3 new agm 100ah 12v batteries coming. Since I have to put the new bank inside the trailer I was wondering if anyone has created dual battery banks. The original wet cell batteries are still functional but definitely not at optimal output. Should I just scrap the wet cells or can I set them up as an auxiliary unit. They only example I could find was someone had created a larger bank that the had a separate inverter connected to the the actually plug third 30amp cord to.

[AnnArborBob]

It's not a good idea to mix old and new batteries in the same array, and it's not a good idea to mix different kind of batteries (wet cell and AGM) in the same array. If you were to do this, you'd need to keep both battery banks separated electrically from each other. Not sure how you could do that and still retain practical use of both for charging and using the power?

[DaveP]

The old wet battery should not be hooked up in the circuit with the new batteries. The old battery will act as a drain on the new batteries. Either go with the three new batteries or get a fourth new one.

[canesx5]

I knew that mixing them was a bad idea but wasn't sure if I could set up as a completely different bank to use as an auxiliary when the other bank got low. That way I would always have a fully charged bank and could recharge the other one. It night be too much hassle then it's worth.
Maybe getting a fourth one is the best option and keeping two outside with 2 inside.

[AnnArborBob]

Originally Posted by canesx5

I knew that mixing them was a bad idea but wasn't sure if I could set up as a completely different bank to use as an auxiliary when the other bank got low. That way I would always have a fully charged bank and could recharge the other one. It night be too much hassle then it's worth.
Maybe getting a fourth one is the best option and keeping two outside with 2 inside.

I believe that in terms of day to day usage, you will appreciate a single larger battery bank (with four compatible batteries) rather than two smaller ones (with two batteries each) that you have to "switch over" somehow.

[drairstream]

So ... I bought a yeti 1000 last year. I want to tie it into my 12 volt system.

Do I tie it into the 12 volt bus bar and put in two battery shut offs? ie one between yeti and one at new wet cell for travel?

[waninae39]

you could use high AMP schotky diodes to isolate the two power sources

[Paprika]

The Yeti powerpacks aren't meant to be integrated into existing 12 V systems. Among other reasons, the Yeti's lithium battery has very different charging requirements from your lead-acid house batteries. Yeti's product description says, "DO NOT ATTEMPT TO CHARGE YOUR YETI LITHIUM FROM A 12V SOURCE. Doing so may cause damage to the unit."

As for tying the Yeti's output side to your 12 V system, that could waste its power trying to charge your house batteries.

These units are meant to be used as standalone devices, not tied into an existing electrical system. If you need more power in your rig, use the Yeti as it was intended to be used, or add more/better house batteries, but don't try to lash the two together.

[drairstream]

I don’t plan to charge it other than via a shore plug.
Was thinking of an a/ b shut off switch to isolate it but run through the 12 volt side. I understand the charging and need to isolate it. Thanks for inputting

[drairstream]

Probably should have bought a battleborn but wanted the other uses for tent campers.

[drairstream]

We are still only camping about 30 days a year so want to wait for other systems to mature and come down some before full solar and inverters. Follow Lester’s advice when I do it though!

[Snowy]

Late to the race.

You can create two separate banks which charge together but discharge separately using an automatic charge relay.

Dual Battery Setup with Automatic Charge Relays

http://www.airforums.com/forums/showthread.php?t=163107

However as others have said, one bigger bank is easier to create, especially if you are not familiar with electrical wiring.

[waninae39]

WARNING- do not install AGM inside a trailer

these must go outside.

They will out gas, this is not sake for breathing

place them OUTSIDE

note Lion DO not have this issue, they can be inside, but not AGM

[n2916s]

AGM's might, in extreme circumstances, out gas some hydrogen ( which is not hazardous, just flammable). The quantity would be minimal and the possibility that you would have a fire is almost non-existent. They can be mounted inside the trailer and usually are.

[rmkrum]

If an AGM battery is stressed enough to vent, something is seriously wrong. Even with an AGM not usually venting, the hazard is that hydrogen is explosive in some concentrations. The main thing is to be doubly darn sure the charging system is properly configured for AGM batteries.

Once an AGM battery vents, it’s not going to be in good condition any more. They cannot be refilled, unlike a standard flooded lead acid battery. Venting in an AGM battery looses water (as hydrogen) and occasionally produces acid vapor, which is a lot more hazardous. Not nice to abuse one...or spill acid inside an aluminum structure....

I’ve had to extract and evacuate overheated AGM battery banks from a computer room. It’s no fun, requires hazmat gear, and a lot of speed and courage on the part of the first to respond. Not my favorite day, I assure you.

[waninae39]

like tires, its NOT a good idea to mix old/new or different types of cells

as others have mentioned, they will fight each other--- you will lose the battle

[Paprika]

"do not install AGM inside a trailer"

Wrong. The main reason for using AGMs in an RV is because they don't outgas, and thus can be installed in unvented areas--unlike flooded-cell batteries, which must be well vented because they outgas routinely. As others here have pointed out, to get an AGM battery to outgas, you'd have to severely abuse it--to the point of permanent damage. In a properly designed charging system, that isn't going to happen. Quoting the Lifeline AGM Battery Technical Manual: "Hydrogen gas emissions (are) generally negligible unless severely overcharged."

As a practical matter, I've used 400-500 Ah AGM banks in RVs for nearly twenty years. I know many other RVers who do likewise. None of these batteries are in vented locations. That's why we chose AGMs: they don't need venting.

[rmkrum]

Yup. It’s a highly unusual situation that causes an AGM to vent. Our episode was probably a cell or two shorting out and at that point the battery charger lost control and went full-on trying to bring the SOC voltage up to snuff. Several of the individual AGM batteries in that assembly vented, ruptured, and started boiling off electrolyte rapidly. I’m sure, had we not detected the smell, and found the thermally hot chassis we would have had a serious incident. Luckily someone was paying attention and raised the alarm in time.

Bottom line is proper battery charger for AGM chemistry, fuses in the right place, and regular maintenance. Despite being front and center on this “almost meltdown” I would use AGM batteries with the proper install of good hardware.

[waninae39]

that is also why we get insurance . if and when are covered

that is why any battery that can gas, should not be enclosed