Is it Okay to Install a Regular Battery Inside the Coach?

Johnny Dearborn,

You mentioned a few things and did not mention a few other things that leave me to believe your setup is the cause of your problem.

1) With two 12 volt batteries in parallel, for them to work right, or better stated "as right as possible", they must be butted up against each other with short fat ~8" cables tying them together. Thick buss bars would be better yet, but very few people would do that. Long cables in between 12 volt batteries is ripe for failure.

2) The batteries MUST be of the same technology. You cannot mix a wet cell with an AGM and get acceptable performance...even if butted up together with thick buss bars. This is because the AGM requires a different charging voltage and charging behavior. That is why chargers have different settings for the various technologies.

3) Even batteries of the same technology, mismatched batteries in brand, capacity, and even age, the weaker battery will bring down the performance of the better battery. Two brand new identical batteries with the same production date vary enough to develop performance issues starting in the 2nd or 3rd year.

In your particular situation with the two batteries separated with a length of cable as you have described, you would be so much happier with two 6 volts batteries because the cable length will not adversely affect them nearly as much (or not at all) as with 12 volt batteries.

If you decide to go with 6 volt batteries, wet acid or otherwise, I personally like to buy mine at Sam's Club. Go on their website and see for yourself.

Your 3 year old on-board charger must be configured to the technology of your choice. Read through the owner's manual before selecting your technology. That charger might not support certain technologies.

BTW, I like the idea of the battery box venting to the outside.

Good luck!
Ron Dittmer

My deep cycle battery is under a booth seat in a battery box. The battery box cover has a 3" flexible hose coming off the top that goes to a nice sidewall
fitting which has a round vent on the outside of the rig. This is what you need for a wet cell battery. Works good, looks good.
Brian

I would suspect that the converter charger is overcharging the SLA battery. Is the SLA battery a good match to the main house battery in capacity, etc ?. It would be best to use two of the same brand/type/capacity batteries connected in parallel with as short interconnect cables as practical given that the converter/charger is not defective and is a modern type with charging characteristic, compatible with the batteries needs. It may be that the chassis alternator is charging at too high a rate for SLA battery while you are driving.

Call Progressive Dynamics and ask for advice from a technician. Have the brand, model number and amp rating of your converter charger and the brand, model number, recommended charge rate and capacity of your failed SLA batteries on hand. Ask about possible chassis alternator overcharging problems. There will be battery supply places in Milwaukee and other larger cities.

I have been using 2-12 volt batteries in parallel for many years, maybe 25, and everything has worked well.

Dusty

I'm an Ordinary RV Guy, not a Battery Guy, Solar Guy or Generator Guy. But based on my very limited experience with Twin House Batteries, PLUS years of reading this Forum:

1. Two 12V Batteries in Parallel don't play well together. It seems like one injures the other.

2. Even if two 12's are brand new, same make and model, this can persist. So an AGM and a Flooded Cell battery can't possibly be "matched."

(So, 3. Two 6's in series is probably the better idea.)

4. To add to the mention of Start Battery (to be used for your Chassis) vs. House Battery (power you Coach lights, appliances etc.), you said this Northstar battery was rated in CCA. That's usually for Start/Chassis batteries. Coach/House batteries should be Deep Cycle and they are rated in Amp Hours. Start Batteries don't last long in Deep Cycle use.

5. What's the actual distance (the wire run length) between your two House Batteries? You will need very good connecting wire between them. I'm concerned that your Charger might be seeing that the (electrically) closer battery as fully charged and laying down before the more remote battery is.

(So 6. I think the wiring has to be heavy, with good connectors, and all kept very clean and tight.)

Have you tried contacting Northstar and asking them? I had an Optima AGM go bad in the first two years and they replaced it for free even though it was a week out of warranty - no questions asked.

Question: are you using AGM for both batteries? Or only for the inside? You can't run an AGM and a regular battery together - if you're doing so, that very well could be your problem. If this is the case, by 2 AGMs and install them both.

If not (had to ask), then how are you charging now? Are you staying at hookup sites? If so, then just run with one battery. Get a cheap regular battery as a back up in case your last AGM dies before you get home.

If you are not staying at hookup sites, how are you charging the batteries? Are you using a generator? Are you using solar? Are you only charging when you run the vehicle?

How long a battery will last will depend on several factors: how much you're using the laptop (all day every day, movie every night, or just 10-15 minutes twice a day), how often you run your water pump, and how much battery power your fridge needs to run its computer components. I would say that with a group 27 or higher battery, you should be able to go at least a day without having to charge if your laptop usage is not extreme.

Sounds like you need to go to two, 6 volt batteries, preferably the Trojan T-105.

The best advice is to get a vented box if you are going to do that.

The battery in my TCer was located under a bench seat and unvented when I bought it and was still there when I sold it with no problems but venting is highly recommended.

My concern would be if you have gone through that many batteries will another one make it through the trip or will you fry it, if you fry it under the seat with no venting then you will have issues. I would stay with the one battery till you get home.

I had a new converter and the extra battery installed three years ago. Since then, I've had three Northstar AGM batteries go south. When I get back home, I'll be bringing my RV back to the shop to check on the charging system. This can't be right. In the meantime I'm stuck trying to figure how to make this work.

AGM does come in both cranking and deep cycle. Make sure you are getting the right stuff.