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 > "A-B" Battery Switch

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K3WE

Missouri

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Posted: 10/19/19 08:34am Link  |  Quote  |  Print  |  Notify Moderator

A very specific objective here: A little discussion from folks who have asked themselves the same question.

First, the context, we have had two batteries for ~20 years and dry camp from time to time. I wired in an marine battery selector switch. The bottom line is that we almost never used it, and I'm trying to decide if it's really worthwhile to replace it on our new camper.

I know someone will suggest we forget about switching and get two 6V batteries.

We may do that someday- but given that- through a turn of events, wound up with two new 12V batteries.

I'm thinking it might be worth it to simply hook them both up "full time".

Any other thoughts or great stories from folks on this subject?

Lynnmor

Red Lion

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Posted: 10/19/19 08:40am Link  |  Quote  |  Print  |  Notify Moderator

K3WE wrote:



I'm thinking it might be worth it to simply hook them both up "full time".

Any other thoughts or great stories from folks on this subject?


Since there are parasitic loads on the batteries, how do you intend to disconnect?





Lwiddis

Near Annett’s Mono Village, Bridgeport, CA

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Posted: 10/19/19 08:50am Link  |  Quote  |  Print  |  Notify Moderator

Yes, put them up together and keep them charged with a solar system. I did that for a couple of years before the twelves aged out.


Winnebago 2101DS TT & 2020 Chevy Silverado 1500 LTZ Z71, 300 watts solar-parallel & MPPT, Trojan T-125s. TALL pole for flags. Prefer USFS, COE, BLM, NPS, TVA, USF&WS, state & county camps. Bicyclist! 14 year Army vet - 11B40 then 11A - (MOS 1542 & 1560)


Sandia Man

Rio Rancho, NM

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Posted: 10/19/19 09:08am Link  |  Quote  |  Print  |  Notify Moderator

Theoretically, at least, it is more advantageous to wire them in parallel according to Peukert’s law. In the RVing world having batteries or battery banks wired independently can mitigate the hassle of waking up to no 12 volts due to dead battery, we have not experienced this issue an always paired up our batteries whether 12 volt or 6 volt. No need to go to a pair of 6 volt golf cart batteries if you are seldom off the power grid, wired in parallel your 12 volt jars should give you a couple of days camping with moderate use.

Grit dog

Black Diamond, WA

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Posted: 10/19/19 09:58am Link  |  Quote  |  Print  |  Notify Moderator

I could see using a battery switch if you could reasonably run down your battery(s) with no means to recharge when needed and wanted to preserve "emergency" power for those situations.
Otherwise it's commonplace to just plug em in in parallel and fuggetabouit. You said it yourself, you almost never isolated the batteries in 20 years, so unless the situation has changed, I don't see the need.
Example, I have our boat's house battery that runs the amps for the stereo isolated from the starting battery with an automatic relay to preserve that emergency power if needed to start the boat. Camper, if the batteries are run down, fire up the generator and charge em up. Or they get charged (somewhat) while driving as long as the burner in the fridge doesn't blow out.


"Yes Sir, Oct 10 1888, Those poor school children froze to death in their tracks. They did not even find them until Spring. Especially hard hit were the ones who had to trek uphill to school both ways, with no shoes." -Bert A.

ajriding

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Posted: 10/19/19 12:25pm Link  |  Quote  |  Print  |  Notify Moderator

with two batteries you are half as likely to have dead batteries. lol. Assuming that they are healthy batteries of course.

Two is more power, more amps, and less chance the lights will flicker when the water pump comes on.

The downfall is that with two 12's they need to be matched and about the same age. If one is a little more gone than the other then it will always be pulling voltage off the slightly better one and the better one will always be drained down to the lesser charge. Thus the 6-volt in series solution.
If you use solar then this mitigates the problems greatly.

Personally I have two 12 volt systems that can be connected together, but I keep em apart. One is dedicated for the electric cooler fridge/freezer, the other for the coach. I can be without coach power, but that fridge has to stay running. Im sure there are other good reasons to keep batteries separated too.

* This post was edited 10/20/19 09:15am by ajriding *

pianotuna

Regina, SK, Canada

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Posted: 10/19/19 12:52pm Link  |  Quote  |  Print  |  Notify Moderator

I do have switches that allow either/or/both. Mostly I use both.


Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp hours of AGM in two battery banks 12 volt batteries, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

JimBollman

Lost State of Franklin

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Posted: 10/19/19 07:34pm Link  |  Quote  |  Print  |  Notify Moderator

I like the A or B - A and B - off switch. Batteries don't need to be matched in A or B mode and I know when I have roughly half my power left and need to find power soon. I used mine all the time. Latest camper only has one battery till I get that modification done.

time2roll

Southern California

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Posted: 10/19/19 08:01pm Link  |  Quote  |  Print  |  Notify Moderator

I agree with just connecting both full time. I don't see any need for A-B switch unless you have a specific issue. Worst case you can lift a cable if needed. Although if you store the RV with no float charge you may want an on-off switch to disconnect them.


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K3WE

Missouri

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Posted: 10/20/19 04:40am Link  |  Quote  |  Print  |  Notify Moderator

Lynnmor wrote:

K3WE wrote:



I'm thinking it might be worth it to simply hook them both up "full time".

Any other thoughts or great stories from folks on this subject?


Since there are parasitic loads on the batteries, how do you intend to disconnect?


Using the nifty isolate/off switch on the new camper or the nifty wing nuts on a terminal.

Please note the quote marks on "full time"

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