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I know we have some RVers on the forum, so I wanted to see if I could possibly glean some knowledge from y'all.

I just traded in our 2011 23' TT for an 18' Off-Road TT, and I'm setting it up for boondock camping. I was able to keep my battery from the old RV, and it's a 8 month old Type 27 1000 CCA Marine Battery from Duralast. The new RV came with some brand I haven't heard of, but it is a Type 27 as well. Big difference is it's only 575 CCA.

I'm wanting to run the batteries in parallel for additional capacity when we're off grid in the mountains. I know that you have to use similar battery types (AGM with AGM, Gel with Gel, etc.), and as mentioned both are Type 27, but does the difference in CCA cause an issue? Am I going to deal with parasitic draw if I chain them?

Put a dual battery selector that is usually installed on boats with dual batteries. You can select each battery independently or both or turn off. I think that would be the easiest thing to do.

Due to different charging and dischargeing I would get batteries of similar age and CCA's.

WTR wrote:Due to different charging and dischargeing I would get batteries of similar age and CCA's.

Tex1961 wrote:

WTR wrote:Due to different charging and dischargeing I would get batteries of similar age and CCA's.

If you want to spend $200 now, that's the optimum scenario. Do you have an auto charger/maintainer in the RV? A procharger or similar like we use in boats work wonderful. I average 5-6 years per battery set. I remove the jumper wire(s) for charging; especially if they are not the same, otherwise the charger will turn off when the lesser batt is full and will kick on/off constantly from the bigger batt.

However, if you already own both batteries- use them until they die or you save up spare change to replace them. The difference is that they won't last as long (regular service or life) but you may still get a couple years depending on other factors like care and use. Then you can buy a matched set and live happily ever after. At that point buy group 29 batts if your compartment will fit them. Amazing how much more capacity and power they hold than 27's.

My experience is 30 years of fishing (rec and tourney) so tending batteries is kind of in my blood.

Best of luck with the new rig!

Consider getting a solar panel for charging.

pbwalker wrote:I know we have some RVers on the forum, so I wanted to see if I could possibly glean some knowledge from y'all.

I just traded in our 2011 23' TT for an 18' Off-Road TT, and I'm setting it up for boondock camping. I was able to keep my battery from the old RV, and it's a 8 month old Type 27 1000 CCA Marine Battery from Duralast. The new RV came with some brand I haven't heard of, but it is a Type 27 as well. Big difference is it's only 575 CCA.

I'm wanting to run the batteries in parallel for additional capacity when we're off grid in the mountains. I know that you have to use similar battery types (AGM with AGM, Gel with Gel, etc.), and as mentioned both are Type 27, but does the difference in CCA cause an issue? Am I going to deal with parasitic draw if I chain them?

no, the CCA difference won't create an issue. CCA is simply the output capability. Time to charge will differ given one battery is 'bigger' than the other but it's still not an issue.

Thanks to everyone for the info!

I'm pretty much in that spot where I have two batteries, one new and one 6 months old, that I would hate to just get rid of. My goal would be to get as much life out of the two I have before they die, and then replace them with Odyssey batteries.

Just thinking out loud here, but could I use the the battery selector switch jason812 mentioned above and run one battery at a time (1 or 2 on the switch) and then when I replace the batteries, run them in parallel (1 and 2 on the switch)? I pull the battery when we store the RV, and keep it on a Noco Genie tender. I could just do the same with both batteries so I'm not charging both at the same time in parallel. Thoughts?

I do have a solar panel, but it's a weak 13W briefcase panel I picked up at Harbor Freight, just as a small supplemental charger. I don't expect too much out of it.

wil wrote:

pbwalker wrote:I know we have some RVers on the forum, so I wanted to see if I could possibly glean some knowledge from y'all.

I just traded in our 2011 23' TT for an 18' Off-Road TT, and I'm setting it up for boondock camping. I was able to keep my battery from the old RV, and it's a 8 month old Type 27 1000 CCA Marine Battery from Duralast. The new RV came with some brand I haven't heard of, but it is a Type 27 as well. Big difference is it's only 575 CCA.

I'm wanting to run the batteries in parallel for additional capacity when we're off grid in the mountains. I know that you have to use similar battery types (AGM with AGM, Gel with Gel, etc.), and as mentioned both are Type 27, but does the difference in CCA cause an issue? Am I going to deal with parasitic draw if I chain them?

no, the CCA difference won't create an issue. CCA is simply the output capability. Time to charge will differ given one battery is 'bigger' than the other but it's still not an issue.

The charge time difference will cause the converter on the rv to overcharge the smaller battery if they are in parallel.

pbwalker wrote:Thanks to everyone for the info!

I'm pretty much in that spot where I have two batteries, one new and one 6 months old, that I would hate to just get rid of. My goal would be to get as much life out of the two I have before they die, and then replace them with Odyssey batteries.

Just thinking out loud here, but could I use the the battery selector switch jason812 mentioned above and run one battery at a time (1 or 2 on the switch) and then when I replace the batteries, run them in parallel (1 and 2 on the switch)? I pull the battery when we store the RV, and keep it on a Noco Genie tender. I could just do the same with both batteries so I'm not charging both at the same time in parallel. Thoughts?

I do have a solar panel, but it's a weak 13W briefcase panel I picked up at Harbor Freight, just as a small supplemental charger. I don't expect too much out of it.

Using the selector would work fine as you describe, also if you have power where you store it you should be able to turn off all the breakers except the converter and plug it into 120v and it will jeep the battery you have selected charged for you. Just have to make sure to leave the 12v disconnect turned on so the converter power can get through to it.

Medley86 wrote:

wil wrote:

pbwalker wrote:I know we have some RVers on the forum, so I wanted to see if I could possibly glean some knowledge from y'all.

I just traded in our 2011 23' TT for an 18' Off-Road TT, and I'm setting it up for boondock camping. I was able to keep my battery from the old RV, and it's a 8 month old Type 27 1000 CCA Marine Battery from Duralast. The new RV came with some brand I haven't heard of, but it is a Type 27 as well. Big difference is it's only 575 CCA.

I'm wanting to run the batteries in parallel for additional capacity when we're off grid in the mountains. I know that you have to use similar battery types (AGM with AGM, Gel with Gel, etc.), and as mentioned both are Type 27, but does the difference in CCA cause an issue? Am I going to deal with parasitic draw if I chain them?

no, the CCA difference won't create an issue. CCA is simply the output capability. Time to charge will differ given one battery is 'bigger' than the other but it's still not an issue.

The charge time difference will cause the converter on the rv to overcharge the smaller battery if they are in parallel.

This has me thinking...

I only plan on running in parallel during discharge. When the RV is not in use, batteries get pulled and will go on tenders individually. Is the mismatch still an issue on discharge? We don't have power at my storage location, and I'm not leaving the batteries out there.

ETA: Disregard...I reread WTR's note above about the difference in charging AND discharging. I think I'll go the switch route.

Medley86 wrote:

wil wrote:

pbwalker wrote:I know we have some RVers on the forum, so I wanted to see if I could possibly glean some knowledge from y'all.

I just traded in our 2011 23' TT for an 18' Off-Road TT, and I'm setting it up for boondock camping. I was able to keep my battery from the old RV, and it's a 8 month old Type 27 1000 CCA Marine Battery from Duralast. The new RV came with some brand I haven't heard of, but it is a Type 27 as well. Big difference is it's only 575 CCA.

I'm wanting to run the batteries in parallel for additional capacity when we're off grid in the mountains. I know that you have to use similar battery types (AGM with AGM, Gel with Gel, etc.), and as mentioned both are Type 27, but does the difference in CCA cause an issue? Am I going to deal with parasitic draw if I chain them?

no, the CCA difference won't create an issue. CCA is simply the output capability. Time to charge will differ given one battery is 'bigger' than the other but it's still not an issue.

The charge time difference will cause the converter on the rv to overcharge the smaller battery if they are in parallel.

nope. Smaller battery will achieve full charge, then the larger battery becomes the path of least resistance due to it's lower level of charge. Hence current will flow to the larger battery.

Think of two drums, one 10 gallon, one 5 gallon, both at same height with a tube connecting both of them. Fill source is connected to the smaller drum. Small drum fills up and flows into the larger drum via the connecting tube.
electric does the same in this instance.

When you do decide to replace your current batteries, you might want to consider getting true deep cycle batteries. A lot of people assume that marine batteries are deep cycle, but they aren't. They are a compromise between a deep cycle and a cranking battery. Batteries made for golf carts and similar vehicles are true deep cycle batteries that will last much longer in boondocking use.

wil wrote: Nope. Smaller battery will achieve full charge, then the larger battery becomes the path of least resistance due to it's lower level of charge. Hence current will flow to the larger battery.

Think of two drums, one 10 gallon, one 5 gallon, both at same height with a tube connecting both of them. Fill source is connected to the smaller drum. Small drum fills up and flows into the larger drum via the connecting tube.
electric does the same in this instance.

^^^ This

The larger battery will hold down the voltage seen by the smaller battery preventing it from overcharging. They'll both reach full charge at the same time.