Auxiliary Battery Replacement - RV-Dreams Community Forum

Kiers10 · RV-Dreams Community Member

Auxiliary Battery Replacement

Neil and Connie · RV-Dreams Family Member

Kiersten,

You'll need to provide more information in order to get any useful recommendations. What's the capacity of your current batteries? What's the size of your house battery bay location…i.e., are physically larger batteries an option? What size of inverter do you have and how many AC loads are on it? Do you have a generator and/or solar to recharge or is your boondocking limited to when your batteries are depleted and then you go into a park to recharge? What kind of batteries do you have now…12v or 2x6v in series…standard lead/acid or AGM? What's the budget? Any plans to add generator/solar if you don't have one or both already?

You'll probably be driven by physical space mostly…if you replace the house batteries with the same model then fit will be no issue. Might be able to put in slightly larger physical size which would have more amp hours capacity…upgrading to AGM means less maintenance but they do cost more and you'll have to adjust the settings on your charger to account for the differing charge characteristics.

Take a look at Howard's electrical system upgrade pages over on the main website…that way you'll know the lingo and understand the various options a bit better.

bjoyce · RV-Dreams Family Member

Here is Howard's electric system link that Neil and Connie refereed to: http://www.rv-dreams.com/rv-electrical.html

Kiers10 · RV-Dreams Community Member

Thank you for the link.

Kiers10 · RV-Dreams Community Member

Thank you for the response Neil and Connie. The Motorhome is 30 Amp and the current battery is a Deep Cycle 1000 marine cranking amps and 180 reserve capacity. It sits under the inside stairs and there is room for an additional battery the same size or a little larger. I do have a generator but no solar power currently. I may add solar in the future but it will probably be several months. I'm still learning about what I've got. Inverter and AC loads...I'm not sure what that means? It's a 12V but I'm also not sure how to tell whether it's standard lead/acid or AGM? I haven't really set a budget but would love to be efficient. I just had to replace the small board in the generator and do roof repairs. I think that answers all of the questions. I've learned a lot in the past few months but there is so much more to learn. I had a dream and jumped in head first.

It's a 24 ft motorhome and normally just my dog and I traveling. I don't tow yet or stay one place long so normally boondocking makes the most sense. I'd love to learn how to use the tools at my disposal most effectively.

I'm very grateful for your time and help.
Thanks again,
Kiersten

Terry and Jo · RV-Dreams Family Member

Kiersten,

If your battery has caps that can be removed to add water, then they are not AGM batteries. AGM batteries are maintenance free batteries and are more expensive than lead/acid batteries.

Terry

Neil and Connie · RV-Dreams Family Member

Kiers10 wrote:
Thank you for the response Neil and Connie. The Motorhome is 30 Amp and the current battery is a Deep Cycle 1000 marine cranking amps and 180 reserve capacity. It sits under the inside stairs and there is room for an additional battery the same size or a little larger. I do have a generator but no solar power currently. I may add solar in the future but it will probably be several months. I'm still learning about what I've got. Inverter and AC loads...I'm not sure what that means? It's a 12V but I'm also not sure how to tell whether it's standard lead/acid or AGM? I haven't really set a budget but would love to be efficient. I just had to replace the small board in the generator and do roof repairs. I think that answers all of the questions. I've learned a lot in the past few months but there is so much more to learn. I had a dream and jumped in head first.

It's a 24 ft motorhome and normally just my dog and I traveling. I don't tow yet or stay one place long so normally boondocking makes the most sense. I'd love to learn how to use the tools at my disposal most effectively.

I'm very grateful for your time and help.
Thanks again,
Kiersten

Ok, first off you realize there are two batteries in a class A, right? One is the starting battery for the rig engine and the other is the house battery. Are you sure that the one you read the numbers off of is the house battery? If not…then you might have to look in the manual or online to make sure.

The shore power amps doesn't really have anything to do with the battery capacity.

Have you done any boondocking yet? If so…how long did the battery last with no shore power? You'll have to see what AC and DC loads you have…usually there's an inverter that takes the 12v DC from the battery and makes 120v AC to run things like computers, outlets, TV, etc. You may again have to check the manual to see how large your inverter capacity is…but you can figure out what loads are powered by the inverter and what loads are only powered by shore power by disconnecting shore power and then seeing what AC loads work and what doesn't. If you don't actually have an inverter…then none of the AC loads will work but if things like TV and outlet work with no shore power then there's an inverter somewhere.

In order to know if you have enough capacity in the battery…you'll need to figure out what AC loads run off of the inverter if you have one and figure out how many hours per day you'll run each of them…then convert that to AC total load and then into DC amp hours (AH) needed…don't worry about doing the math as we can help you with that.

If you don't actually have an inverter…then pretty much the only stuff that runs off the battery is the DC lights in the rig, the control circuitry for the RV fridge if you have it running on propane, and the starter for the generator. If that's the case then 180 AH which is what I believe the 180 refers to is probably enough for overnight. You can only actually use 50% of your total battery capacity repeatedly or else it lowers the life of your batteries…although deep cycle marine type batteries are a little more forgiving on that point than AGM or regular lead/acid batteries are.

As you can see…it's a lot harder than just a simple "how much battery do I need" sort of question. I'm generalizing here…but likely you have an RV fridge and at best a relatively small capacity inverter so that things like a couple of outlets and the TV can run off of the battery…you won't have the large pure sine wave type inverter that those of us with residential fridges require. Other things you need to know are what your total AH usage per day is, how often you want to boondock, how long you want to go without the generator needing to be run. Since you're a pretty new RVer…you'll need to figure out a few of these answers so that we can help you with the math, battery sizing, and some of the technical details.

LarryW21 · RV-Dreams Family Member

" I may add solar in the future but it will probably be several months."

Several more months of generator time when your planned future is getting solar? Get solar now and skip the noisy generator most of the time. For me...60 days of camping without need of the generator...except weekly "exercise" sessions of ten minutes.

Kiers10 · RV-Dreams Community Member

Thank you again for your response and assistance. I don't have an inverter and it is apparently an AGM battery because there isn't anything that can be removed to refill the cells. The TV, microwave, air conditioning and electrical outlets don't work without running the generator or of course plugging in. The fridge runs off the propane when boondocking. I have boondocked on a few trips. I boondocked on a three week New England trip in October. I discovered two days into the trip my control board went out in the generator and didn't have the resources to get it repaired on the trip. I also learned on that trip that my current battery would only last overnight (7-9 hours) using very low amps. I have led battery operated lights so I didn't use many lights when boondocking. I occasionally used a converter from the cab to plug in the TV and charge devices but was careful not to run down the rig battery. It worked out okay the last trip because I drove enough every day to recharge the house battery but I'd like to have enough charge to not have those concerns and be able to boondock a few days without running the battery down. Would you recommend AGM or regular/lead batteries? I found an affordable Duracell AGM 800-MCA, 650-CCA, MINS @23 Amps 225 I considered buying two of. I'm just very concerned about making a mistake and learning later I should have purchased something different or more powerful.

Neil and Connie · RV-Dreams Family Member

Generally speaking I would recommend AGM if it was feasible cost wise. Not knowing much about the ones you’ve found, analysis in detail of your loads, or any experience in mostly 12v low battery capacity no inverter rigs I hesitate to make a recommendation. Our rig has a residential fridge and 800 AH of batteries so that’s all we have experience with. I should let those here with experience in similar rigs/setups to yours make those.

bjoyce · RV-Dreams Family Member

"I also learned on that trip that my current battery would only last overnight (7-9 hours) using very low amps."

There are more loads on that battery than you know. The fridge does use some battery power to run its controls and internal lights. The furnace can really use battery power to run its fans and a bit to run the thermostat. You might have an LP detector using a small amount. It all adds up. To really know what is happening you need to put in a battery monitor, $165 or more, an expense that might not be worth it for you. Your current battery might be OK, just being asked to supply too much overnight. I suspect it is not OK, but I would get it load tested. Many auto parts stores can load test it for free, but they are expecting to sell you a replacement battery to cover their expenses.

Kiers10 · RV-Dreams Community Member

Thank you both again! ; ) I'm going to go to BatteriesPlus today or tomorrow to get it tested. I also found an AGM 1000 MCR 105AH (20 hour capacity) there for $215. I can fit two or maybe even three of them in the space I have. I think two should be enough for what I'm doing now and they should also work with Solar once I upgrade. The cost of setting up Solar is a little out of reach currently.

Happy trails!
Kiersten

LarryW21 · RV-Dreams Family Member

" I occasionally used a converter from the cab to plug in the TV and charge devices but was careful not to run down the rig battery."

Engine starting batteries are not made to slowly discharge running a TV etc. Quick bursts only. I recommend you discontinue using for TV etc.

Kiers10 · RV-Dreams Community Member

Oh bummer! Thanks Larry, I guess I need to rethink my entertainment options when traveling alone. I've learned more since the last trip and can download movies to my laptop now which has a very good battery. I don't need air conditioning this time of year and have a charging device for electronics. That only leaves the microwave which I can easily live without. I hate running the generator, it's noisy and annoying. I look forward to eventually converting to solar. Do you love it?