6 Volt System Question

[Bob Windom]

I have in my motorhome a 6 volt house system consisting of two Interstate batteries connected in series. I have one battery that died on me and I want to replace it with a new one. I was told that I would have to replace both batteries even though one of them had excellent reads both in voltage and specific gravity. Is this just a ploy to get me to spend more money or is there basis for fact in the statement of replacing both?
Many thanks,
Bob

[RV Mech Tech]

Bob: if both of your batteries are around the same age, then replace both of them. The reason for this is if both of these batts were installed at the same time, then the other one is not that far behind. I have done cell, S gravity and load tests on batteries, and left them at the owner's request only to have them come back later and replace the second one as well. Batteries have a service life of around four years on average (I will get arguments on this one)! I have seen some older batteries last 10 or more years but these are the exception. If lead/acid batteries are maintained, then you will get longer service life and the batt manufacturers always tell you to replace all the batteries in the set. As a battery ages, it begins to sulfate and if a new one is installed with an old one, then the charging system (in whatever the batts are installed in) will be working harder to overcome the sulfation of the older battery. If both are new, then the charger will work less, and a sulfated battery will characteristically have a tendency to restrict the flow of electricity through it and may cause problems in the electrical system. You can do a visual check of the cells and if the electrolyte solution inside any of the cells is cloudy, then that cell(s) is not performing 100%. Also look at the outside of the batt case. If it is bulging on the sides, then that is a definite sign of sulfation. I have seen several pass a load test, then fail in a short time when put under a constant load. You can get more info on the Trojan batteries website www.trojanbattery.com. This site has excellent technical info.

[bandit1538]

Bob, I think you have a 12 volt house system. If you have 2 six volt batteries in series, then you'll have 12 volts of juice.
Pat
_________________
Pat & Helen
30' 04 Coachman RoadMaster
For NW HOVER-IN updates and info goto
http://bandits-stuff.com

If it ain't broke don't fix it.

[Bob Windom]

Hello to RV Mech Tech and thank you for your reply. You confirmed what I really had expected but wanted a pro to advise me rather than someone who wanted to sell me something. Thanks so much.

Bob Windom

[RV Mech Tech]

You're welcome, Bob. That's what this forum is all about: to help fellow RVers not only solve their problems but to save them money and provide information no matter what topic you want to know about. There are many members who contribute on the different topics and with RVs, you need forums like this not only for information on problem solving but also to make available topics about the RV lifestyle. Glad to help out!

[retired and happy]

I have a similar problem. I replaced all three batteries in my MH this summer. As a part of that change, I replaced my two twelve volt parallel coach batteries with two six volts in series. After my July trip I didn't use the rig for a few months, although it was constantly connected to shore power at home. As I was getting ready for some fall travel, I discovered several 12 volt devices did not work. On checking the batteries my charger said it could not charge, but something was wrong with the battery. I don't know if there is something wrong with one or both 6 volts. The problem is that Sam's Club offers no warranty on the golfcart batteries like there is on the chassis battery. Both show low voltage. I sure hate to replace two batteries used only one time. Any suggestions?
_________________
Ken
Judy and our Special Angels
1996 37' Itasca Suncruiser
6x12 cargo trailer
2003 EZGO golf Cart

[RV Mech Tech]

Ken- you mentioned that your 6 volt bats are golf cart type- are they lead/ acid -same as the regular coach/chassis bats? or nickel cadnium sealed type? - I have heard of a lot of RVer's using golf cart type batteries with some RV's but I have also heard that many have had trouble with them as well- if any battery sits for a long time without being charged then it will sulfate to the point that it will no langer hold a charge- also as you have said your bats are 'golf cart bats' and not really intended to sit out in the cold use and this is one of the reasons RV manufactures do not use these type of bats in RV's- also a larger lead/acid bat will have a much greater reserve capacity especially a 'deep cycle' battery - a deep cycle bat is intended for marine, RV, and heavy duty service work - it can be discharged several times and bounce back after charging and still be usable- your chassis battery is not a deep cycle and the golf cart bats are not either- also the converter charging rate may be too high in your specific application and may have damaged the GC bats- with a regular 6 volt coach lead/acid bat you can load test it (if you know the cold cranking amp capacity CCA or use a comparible chassis bat group size for reference) but how do you test a gc bat? - for someone that stays in their RV full time and is constantly monitering the condition of the bats the gc bats would be a less expensive alternative- but from what I have seen and heard they may be more trouble than its worth- many owners do not realize that if you leave your RV sit for any amount of time you still have to monitor everything (if possible) including and especially the batteries- if this cannot be done then the bats should be removed and you can charge them up once a month and re-install them to operate the RV and systems to keep everything operating- some people do not do this and they have no problem at all- some do - it also depends on what the climate is and where the RV is stored- if your bats do not hold a charge and are showing low voltage that indicates they will no longer accept a charge and require replacement- I would install regular 6 volt deep cycle bats and/or if you wanted to increase the amp per hour capacity and have the room on the bat tray you can install more than one 12 volt in parallel- this will increase your reserve capacity for the coach - this is usefull for dry camping or 'boondocking' - check out the Trojan website in the above post for more info.