What battery type to purchase

[babock]

Originally Posted by DavidBo

I guess I'm thinking about the lithium-ion batteries that have had this issue. That's the type of battery I was considering, not sure if that's the type that would be used as a house battery.

The batteries that replace the lead acid batteries are the LiFePO4 type. VERY safe.

[newRVer]

After some internet searches I think I have found a 12V AGM battery that is not too heavy or expensive. Problem is it is a little too wide to fit inside the battery box located in the steps. I am not sure why they made the box as wide as they did and then made the opening so much narrower but it is what it is. The battery I'm looking at is 8 inches wide but the opening on the battery box is 7+ inches.

Has anyone ever widened the opening to the step battery well or read about someone who did?

[newRVer]

I am also looking at the option of using a pair of slightly smaller group 24 85Ah 12V AGM batteries in lieu of a pair of 100Ah of FLA batteries. Anyone have any thoughts about the trade offs between a lower Ah rating relative to the benefits of AGM? I'm looking at this as an option since a pair of group 31 100hr AGM batteries would add 30-40 lbs to my rig whereas the group 24's would weigh about the same as my current 100hr FLA batteries. This is important as we already are at capacity on most trips. Also, we are connected to power most of the time so the batteries/solar only need to carry the load when the RV is parked and while we are in a hotel or sightseeing.

I'm thinking that I may not miss the AH's much since the AGM will charge faster, handle 50+% DOD better and I now have 200W of solar.

[camaraderie]

Originally Posted by newRVer

I am also looking at the option of using a pair of slightly smaller group 24 85Ah 12V AGM batteries in lieu of a pair of 100Ah of FLA batteries. Anyone have any thoughts about the trade offs between a lower Ah rating relative to the benefits of AGM? I'm looking at this as an option since a pair of group 31 100hr AGM batteries would add 30-40 lbs to my rig whereas the group 24's would weigh about the same as my current 100hr FLA batteries. This is important as we already are at capacity on most trips. Also, we are connected to power most of the time so the batteries/solar only need to carry the load when the RV is parked and while we are in a hotel or sightseeing.

I'm thinking that I may not miss the AH's much since the AGM will charge faster, handle 50+% DOD better and I now have 200W of solar.

Well that is a perfectly reasonable choice if you don't boondock. MOST AGM's in that group size are dual purpose batteries which is also fine in your situation. AGM's sometimes charge a bit faster if you have a charger that can push them ...in this case something over 40 amps in a 3 stage charger...they CAN be discharged deeper than 50% but there is a loss of cycles there AND they don't have as much cycle life in the lab as wet cells to begin with IF the wet cells are well taken care of (most are not!). Anyway...I support your choice given the circumstances. Another alternative would be wet cell group 24's AND a profill watering system which would be cheaper than AGM's and still be easy to care for.

[babock]

There are AGMs in that size that are true deep discharge. VMAX is one of them and Lifeline is the other.

You still don't want to discharge more than 50% with AGM. You reduce their life just like you do with FLA.

[camaraderie]

Originally Posted by babock

There are AGMs in that size that are true deep discharge. VMAX is one of them and Lifeline is the other.

You still don't want to discharge more than 50% with AGM. You reduce their life just like you do with FLA.

Vmax does not have the plate thickness of a TRUE deep cycle. Their amp hour rating is also suspect. Lifeline does. The Reliant line of Trojan is perhaps the truest deep cycle G24 agm today. Priced accordingly...and NO NEED for them for the uses of this OP. Agree on the 50%.

[babock]

Originally Posted by camaraderie

Vmax does not have the plate thickness of a TRUE deep cycle.

That's kind of interesting since I called them for my brother and they claimed otherwise. He bought one for his camper where he could only fit one battery. He bought the size 31.

[newRVer]

Finally made a decision on what to do to replace the batteries. Lithium is really becoming more appealing but I discovered something that will prevent me from going in the direction right now. I found a good thread that walked through some people's experience with Battle Born batteries
(Battle Born LiFePO4 batteries - Page 3 - Airstream Forums) and while the PD 4600 series CC in my RV is compatible with these batteries, it is not optimal. I.e. Since the voltages for each charging stage are fixed and not programmable then I would not be able to maximize the capabilities of a lithium battery. Long story short, before I install Lithium batteries, it would also be in my best interest to upgrade my CC which is not something I want to do at this time.

That being said, I am going to go with a pair affordable Group 27 6V AGM batteries for now just to get me by the next 2-3 years. At that point if I am going to keep the unit, then I'd probably replace the CC and go with Lithium batteries assuming that the cost of them has come down to the point where it makes sense.

[babock]

I read that whole airstream thread. Confirms my decision to go with the lithium Battle Burns.

[Iwannacamp]

Originally Posted by camaraderie

Vmax does not have the plate thickness of a TRUE deep cycle. Their amp hour rating is also suspect. Lifeline does. The Reliant line of Trojan is perhaps the truest deep cycle G24 agm today. Priced accordingly...and NO NEED for them for the uses of this OP. Agree on the 50%.

Thank you for your knowledge. I sold batteries(mostly auto) and thought I knew a little about batteries/construction/types/manufacture/service/price and brands. People like you prove I have much to learn. Keep up the good work Sirs.

[babock]

Originally Posted by Iwannacamp

Thank you for your knowledge. I sold batteries(mostly auto) and thought I knew a little about batteries/construction/types/manufacture/service/price and brands. People like you prove I have much to learn. Keep up the good work Sirs.

Vmax is a true deep cycle battery and is currently being sourced by multiple RV solar installers.

[newRVer]

Here's a few pics of the finished project. With the lousy weather this spring I could not get to it sooner but now that's it's done there is a laundry list of other things that need to be finished before vacation season starts. Here are some of the changes and modifications I made.

1. Moved solar controller into battery box - Now that I have AGM batteries I won't have to worry about corrosion affecting electronics or wiring. Also, since this unit does not use a probe for temperature compensation but has its built into the controller, having it close to the batteries will provide a better regulated charge and should minimize voltage drop out of the controller as well.
   
2. Rewired panel termination box - Added some 12V connections to power various odds and ends. One direct to battery (switched) and the other off the load output of the controller.
   
3. Added external 4-point positive connection post - since the 6V batteries are in series and the terminals on the battery are small, this allowed me to create multiple connections to the positive terminal without having to wire directly to the battery.
   
4. Added Victron BVM-712 Battery Monitor - Installed this into cabinet facing step well and placed shunt into battery well.

All in all it turned out pretty well and I can't wait to get on the road and appreciate the new handiwork!

[Gidyupgo]

Hi newrver. So, checking in to see how this has worked for you. Did you make any changes based on use / observations?

[newRVer]

Originally Posted by Gidyupgo

Hi newrver. So, checking in to see how this has worked for you. Did you make any changes based on use / observations?

It's been working quite well, no issues to report.

[Gidyupgo]

Glad to hear it. Very nice setup.

[tomaryan]

Can I replace 2 6v flood batteries with one 12 v AGM?

[camaraderie]

Originally Posted by tomaryan

Can I replace 2 6v flood batteries with one 12 v AGM?

Yes... BUT....you'll only have about 1/2 the amp hours of charge. A pair of 6V makes ONE 12V of 210 amp hours.
A single large 12V (Group 27 or 31) holds half that. You would need to wire a PAIR of 12V in PARALLEL...connecting red terminals to red terminals and black to black,,, to have the same battery capacity.
AGM's of ANY type have NO MORE capacity than flooded cells and cost twice as much for their other qualities.
On a budget...wet cells give you the most bang for the buck. BUT more get murdered early due to lack of maintenance and proper charging. Your choice!
For those who don't have easily accessible batteries the other option to AGM's is to buy an EZ watering system like the Flow Rite which makes watering a 10 second affair. Kits are available on Amazon for both 6 & 12V banks.
https://www.amazon.com/Flow-Rite-MP2...HB38P24WYTEXVC

[Duckogram]

Originally Posted by tomaryan

Can I replace 2 6v flood batteries with one 12 v AGM?

WOW! 1st post since joining over 6 years ago. Might be a record.

Besides what Cam said, why would you want to? Also, you have 2 6v batts now so since that is not a Forester or Sunseeker configuration I am wondering what type of Motorhome you have? That info might answer the question of whether or not your converter/charger will work on an AGM.