12V vs 6V house batteries

Rriverdude · 05-19-2022, 01:45 PM

my house lights do not work unless I am plugged in or generator is running. I have two 12V brand new batteries, and lights still didnt work. Its in the shop right now, and they called me and said I should only have two 6V batteries wired for 12V. (they also said my 1 month old battieries are no good. I have a 1990 Winnebago Chieftain.

Does this make sense? Should I only have the two 6V batteries? Thank you all in advance!

cbeierl · 05-19-2022, 04:40 PM

The last page of the Chassis Wiring Installation diagram for your coach shows 2 12V coach/house batteries wired in parallel. (If they were 6V they would be wired in series to create 12V.)

That being said, you certainly could replace 2 12V batteries in parallel with 2 6V batteries in series, but they need to be wired differently.

BobC · 05-19-2022, 07:41 PM

Chris is correct but the real question is why did your brand new batteries fail? Unless they were defective, it's likely that any batteries you replace them with will fail as well.

I'm wondering if, before you installed your two new 12V batteries, your MH had two 6V batteries wired in series. If you installed two 12V batteries, using the same cable configuration, they'd provide 24V but the charge they'd receive from your converter/charger would only have been 12V. This would not only damage your batteries but, if they were supplying 24V to your lights and other 12V equipment, they could have damaged your lights and equipment as well.

That would explain the statement that you "should only have two 6V batteries wired for 12V". If this is the case, they were remiss in not explaining this to you in more detail.

Here's a link that may help you understand the difference between series and parallel connections:

https://thecampingnerd.com/how-to-wi...-batteries-rv/

Morich · 05-20-2022, 09:16 AM

Lots of room for missing the right info here!
First is the way batteries work and when they are wired series or parallel.
We might think of two batteries as a team of horses?

If they are wired series, it is like one horse is in front connected to a second horse behind. One horse head connected to the other's tail? You get two six volt batteries wired series and get 12 volts but not much lasting power.

Take two 12 volts batteries and wire them parallel, like two horses side by side and you still get 12 volts but lots more lasting power.
Two 12 volt in series and you add the volts together and get 24! NOT what you want.

In your case and having somewhat limited space to put batteries, I would not want to go to 6 volt batteries but get the two largest 12 volt that fit and run them parallel as the OEM drawings for your coach show here. A true deep cycle battery is best here, not a battery like for fishing as those are a combo start/ deep cycle. A pair of true deep cycle will last better.

But part of that can depend on how you use your RV. If you only use the RV at campsites where you are usually plugged in and having the longest lasting battery supply is not critical, the combo battery which gets little reall stressful use can be good econmics, as you only need them to do the small charge/discharge when not plugged in or running the RV engine which both work torechargetehm. This has always worked for us.
If you go to the woods without plugging much of the time, better setups at more cost may be best.

Click this drawing to get a better view.

But why the new batteries might be bad? If we don't watch carefuly, there are power drains on both the start and coach/RV batteries, even when we may think we had them disconnected at a cutoff switch. While stored, these drains can run a battery totally flat and that does often damage them, so review if that is your case? Letting them be charged but not checking the water to make sure we don't let them run dry is a real killer, too. Some of the older RV had converters which charged too high, too long for the best battery life.
Or maybe the charging was not getting to the batteries?

I'm not sure I would recommend the tech work as they need to explain the what and why a lot better!

Bearpawl · 05-20-2022, 05:01 PM

I think 2 6volt deep cycle batteries are better. My reasoning is the 6 v batteries are higher amp and they can be charged and discharged many more times. I run 2 in my sprinter for a 2000 w inverter runs my fridge 24/7 and never had a problem. But as stated above really need to make sure wiring is correct.

Morich · 05-20-2022, 06:29 PM

Quote:

Originally Posted by Bearpawl

I think 2 6volt deep cycle batteries are better. My reasoning is the 6 v batteries are higher amp and they can be charged and discharged many more times. I run 2 in my sprinter for a 2000 w inverter runs my fridge 24/7 and never had a problem. But as stated above really need to make sure wiring is correct.

Fully agree that six volt can be betterfor some but that's where the way we each use them comes in. If we don't ever use the batteries for long term without charge, the 12 volt is cheaper and work fine.
The only time we use the batteries much is when we stop along the road, like at a park, shopping, etc. and then we are on down the road to a site where we have power.

Wyatt · 05-21-2022, 12:15 PM

Quote:

Originally Posted by Morich

Fully agree that six volt can be betterfor some but that's where the way we each use them comes in. If we don't ever use the batteries for long term without charge, the 12 volt is cheaper and work fine.
The only time we use the batteries much is when we stop along the road, like at a park, shopping, etc. and then we are on down the road to a site where we have power.

Are you sure you drew the negative lead correctly?

Morich · 05-21-2022, 03:06 PM

I just cut and copied from the drawings but also both drawings above show the same thing.

Positive post to positive post and neg to neg for parallel? That leaves the voltage stay the same and doubles the amp available.

I don't like their drawings of where the cables end up as they get into too many dotted lines to follow very well, but I assume that most won't be changing the other ends?

And looking closer? Yes, I see that I did not look carefully at where the cables went after they left the battery rack.

This is the OEM drawing without my adding anything.

codgerbill · 05-28-2022, 06:49 AM

I have a 12V for the engine and 2 6V golf cart batteries (wired in series) for the house service. I somehow have a "phantom" load on the house service batteries. I could spend time trying to figure out where the phantom load is or.....install a battery disconect switch for when the coach is in storage.

Morich · 05-28-2022, 08:26 AM

Arer you familiar with the term "parasitic drain" on RV?
Those are the normal items left on when we turn the battery disconnect OFF!
Safety items like CO and propane detectors, etc are left on as a safety item. Just the way it is designed on most and we need to be aware ofthem when we store the RV for very long.

This is the drawing for a 38 foot Suncruiser and shows the normal setup we find typical on most Winnebago.

The green line shows flow from the start battery direct to the fuses on circuit KKG and the blue shows circuit GJ from the coach batteries and niether go through the battery disconnect.
The only power cutoff by the disconnect is the red trace which feeds most of the other power in the RV on circuit KKF!

So if we want to turn all power drains off, we have to do more than just flipping the switch!

BobC · 05-28-2022, 09:12 AM

Here's some more info on parasitic loads:

https://www.winnebago.com/Files/File...%20Systems.pdf

Your starting battery is also subject to parasitic loads just like your vehicles at home.

In most cases the level of parasitic drain is normal. The exact level is highly dependent on the equipment installed. I've seen estimates of somewhere between 100Ma - 250Ma for house batteries, less for starting batteries. The only way to determine if you have an abnormally high draw is to measure it with a multimeter:

The RV Doctor: How to find drain on RV batteries

Morich · 05-28-2022, 10:46 AM

As a small side effect of the pandemic and the change to working from home, the parasitic drains on cars has become more wide spread and known.
My daughter is one who suddenly had car problems that were ttraced back to not using her car!
All newer cars are prone to having more and more drains as we get more and more electronics gizmos. So when we were driving to work every day, the batteries were used and recharged every day, but when we stopped driving to work, those drains were likely to get the battery discharged and not recharged well enough. Eventually a car that is only driven to the store once a week or so, winds up with a dead battery!

I've now rigged a convenient way for her to plug her car in to charge while she works from home.

BobC · 05-28-2022, 11:46 AM

I should have added that one of the best tools for measuring amps is a multimeter with a clamp-on amp probe. With one of these, it's not necessary to disconnect anything, just "clamp" the probe around the wire (or wires) in question and take a reading. Here's a link to a some on Amazon. The title and basic descriptions can be misleading as to whether DC amps are read via the clamp-on probe, so be careful. For example, the Etekcity Digital Clamp Meter on the list only reads AC amps:

https://smile.amazon.com/s?k=clamp+m..._ts-doa-p_1_22

I bought this one:

https://smile.amazon.com/KAIWEETS-Mu...23&sr=8-3&th=1

Once you have a clamp-on meter you'll wonder how you ever got along without one.

The clamp-on probe is directional and usually has an arrow or some other indicator pointing to the + side. I don't see this as a big deal most of the time since I usually know if I'm measuring a current drain or charging current so if my probe is reversed and I see a + instead of a - or vice versa, it doesn't matter to me. It does make a difference in more complex trouble shooting. Here's an explanation from Fluke, a manufacturer of high end meters:

https://www.fluke.com/en-us/learn/bl...-current-clamp