6 volt vs 12 volt batteries

Snakebite · 09-23-2018, 05:51 PM

The argument has been around for a very long time. Some folks just swear that two 6 volt Golf cart batteries hooked in series are better than two 12 volt batteries hooked in parallel. Power is power. It doesn't matter if it comes from a pair of 6 volt batteries or a 12 volt batteries. If the amp hr rating of the 6 volt arraignment and the 12 volt arraignment are the same, then there is no difference at that point. If all batteries are truly deep cycle batteries, then that part is virtually the same. I have always preferred to use two 12 volt batteries with a A-B switch for a few reasons. First off, 12 volt batteries are much easier to find than 6 volt batteries. If you need one out on the road it is easier to find a 12 volt. Also, if your tow/ed vehicle needed a battery for some reason, you could steal one from the coach, or vise/versa in a pinch. Then the really big reason... if a cell shorts out in one of the batteries (not uncommon), if you have two 12 volt batteries rather than two 6 volt batteries, you can just remove the bad one from the circuit and everything (lights, refrigerator etc, etc, will continue to work as they should. THAT won't happen if one of the 6 volt batteries goes bad. Remember, Power=Current X Voltage. When connecting batteries in series, the voltage adds up but the current (amps) stays the same. When connecting batteries in parallel, the voltage stays the same, but the current (amps) adds up. Always refer to Amp hr rating and not peak amps, and choose your batteries carefully.

BobC · 10-11-2018, 08:50 AM

Interesting points. I've always preferred the dual 6v route but your post has me thinking. I'm glad you included the qualification about the batteries being true deep cycle. I suspect that most of the 12v batteries found in RVs are not but are "marine" batteries that combine starting and deep cycle attributes. These are not as robust as true deep cycle batteries.

Snakebite · 10-12-2018, 06:53 AM

Hi Bob C. Looks like you are just up the road from us. We are in Clovis, Ca. Yes indeed you are correct. Most folks using 12 volt batteries end up buying Marine type batteries because they are cheap and easy to find. In order for my advice to be valid it is imperative to use Deep Cycle batteries. There is another thing that can happen if a cell shorts out in your 6 volt arraignment while you are hooked up to shore power. The Converter in the coach will kick into High gear trying to charge that battery pack back up to normal. If you have two 6 volt batteries in series, it will boil the water out of the "Good" battery trying to bring the arrangement up to the proper voltage. If using two 12 volt batteries in parallel and a cell shorts out in one of them, the converter will again kick into High gear trying to bring the one back up to normal... and it will indeed over charge the "good" battery... however, due to the fact that they are in parallel, the charging current in the good battery will be much lower, and less likely to be destroyed.

Snakebite

powercat_ras · 10-12-2018, 08:13 AM

One of the few in-disputable advantages of 6 cell (12 V) batteries vs 3 cell ( 6 V ) batteries is that they don't have to be deployed in pairs. Odd #s are fine.

For even #s, you can store more power in the same space at the lowest cost point with 6 volt golf cart batteries, given your RV has a battery space that can handle the fact that golf cart batteries are taller in height vs. conventional RV/Marine batteries.

Costco by Interstate 6V golf cart batteries cost under $ 80 and hold 200 Amp-hours each. Best cost vs. life and capacity available in the USA.

Mike Owens · 10-12-2018, 09:52 AM

I may go back to 12 vdc from my 6 vdc based on some of this input. However the Trojan are proven quality and longevity based on my marine experience.

Snakebite · 10-12-2018, 10:09 AM

Power Cat... you are sure correct that the best cost vs capacity is indeed with that COSTCO 6 volt battery. Buying two of them from COSTCO would cost you about half of what it would cost you to buy two Interstate 12 volt batteries that would deliver the same AH rating and Reserve capacity. There is however one thing that I believe should be considered. Golf Cart batteries are designed to power a MUCH larger load than RVs need. Using them is overkill for such a small load as most RVs represent. Purchasing a mid range deep cycle 12 volt battery will cost about the same as that COSTCO battery. In most every case the user would never realize any difference. If a very extended period of "Dry Camping" without ANY source of recharging the batteries were required, the larger capacity would come into play. However... even a small solar panel setup would completely compensate for that. I have NEVER.... in 50 yrs, had my RV batteries go dead except for a Shorted cell. Bottom line... the user needs to do what they think is best. For me, using two 6 volt batteries is overkill, and runs the risk of being without power if one fails.

powercat_ras · 10-12-2018, 12:42 PM

Snakebite ... Guess we will just have to agree to dis-agree. Personally I have never had even the cheap RV/Marine batteries fail due to a shorted cell. What I HAVE seen is all the cheap RV/Marine batteries I have owned in my RVs lose a large % of their storage capacity due to lead sulfate depositing on the battery plates.

I currently use a BatteryMINDer® Model OBD-12: 12V On-Board Desulfator to prevent that problem. So far it has been protecting my Costco Deep Cycle Golf Cart Batteries well.

BobC · 10-12-2018, 01:16 PM

I enjoy and appreciate discussions like this that provide discussions backed up with something more than opinion, in contrast to the all to common "what tires should I buy" and similar postings.

Snakebite · 10-12-2018, 04:08 PM

Powercat… The Battery minder is a very good unit. I have two of them. The single biggest reasons that RV batteries fail is because of Over charging, which will also increase sulfate deposits. As the lead from the plates collects at the bottom of the battery case, it will eventually short out. Here is a bit of information regarding how frequently battery cells short out.

"According to the 2010 BCI (Battery Council International) Failure Mode Study, shorted batteries accounted for 18 percent of battery failures, a drop from 31 percent 5 years earlier. Improved manufacturing methods may account for this reduction."

After reading this, I contacted Interstate battery company and ask about it. Being a Electrical Engineer, I just wanted to know what they had to say about it. They said that they have made great progress in decreasing one of the main reasons for lead acid battery failure.... that problem being sudden battery failure due to a shorted cell. Lowering the specific gravity down to 1.2 vs 1.265 has decreased the sulfating a good amount. Chargers are also much better now days. Even so most RV converters do not have the sophistication that your Battery Minder does, and if left plugged in will eventually destroy the battery. Since cell shorting has been diminished, this is good news for those of us that use batteries. Whether you use 6 or 12 volt batteries, adding a good cutoff switch and using a quality charger will pay off in battery life.

Snakebite

BobC · 10-12-2018, 09:46 PM

Snakebite- Which model Battery Minder do you recommend?

akeagle · 10-13-2018, 01:37 AM

This is a bit off topic, but since we seem to have several battery experts here, does anyone know who makes DieHard batteries for Sears? I've used DieHards for years for my four-wheelers, but its looking like Sears is going belly-up pretty soon, I'm wondering who else sells the same batteries under a different name.

Snakebite · 10-13-2018, 06:49 AM

Chargers

Hi Bob C…. my apologies, I hit the trigger too fast on that post.... I use a Battery Tender, not a Battery Minder. My Bad.. however, most of the new computer controlled chargers are very good at keeping a battery in top condition. I have two Battery Tenders. One is a small 1.25 amp Battery Tender Plus, it does a great job of maintaining the truck battery or the motorcycle. The other is their Two Bank model that I use on the RV while at home. At home I keep the Coach Batteries disconnected via the disconnect switch and use the Two output Battery Tender to keep them in top shape. If you keep them isolated from each other, then the Tender can deal with each battery as need be. (A-B switch) While dry camping I let the Solar panels keep the batteries charged. I have always used a A-B switch and try to switch between batteries every day always keeping a fully charged battery in reserve. This is one advantage of using two 12 volt batteries. I have not as yet got around to installing the A-B switch on this new MH, but it is coming very soon.

powercat_ras · 10-13-2018, 03:47 PM

Here's one for $ 30 that I use that has the BatteryMinder patented desulfating output that reverses desulfation without causing plate flaking that can cause debris buildup in the bottom of battery cells eventually leading to cell shorting.

I have used it to rejuvenate vehicle batteries.

Battery Minder Charger/Maintainer/Desulfator

Shedboy · 10-24-2018, 09:26 AM

Very good analysis of the battery configuration, has me thinking of the total energy supply design, In the event that house battery power is critical, does pushing the "Battery Boost" switch allow the coach batteries to be temporarily connected to the house batteries?

Also, if battery jumper cables are carried, can the coach batteries be temporarily be connected to the house batteries?

If the RV has a generator then one or the other batteries could be charged and temporarily be connected to the other, a good reason to carry jumper cables.

Also a reason to have an LPG generator on diesel RV's so that the electrical power supply is independent of the engine fuel supply.

BobC · 10-24-2018, 05:05 PM

Quote:

Originally Posted by Shedboy

Very good analysis of the battery configuration, has me thinking of the total energy supply design, In the event that house battery power is critical, does pushing the "Battery Boost" switch allow the coach batteries to be temporarily connected to the house batteries?

Also, if battery jumper cables are carried, can the coach batteries be temporarily be connected to the house batteries?

If the RV has a generator then one or the other batteries could be charged and temporarily be connected to the other, a good reason to carry jumper cables.

Also a reason to have an LPG generator on diesel RV's so that the electrical power supply is independent of the engine fuel supply.

1. Yes, that's what the battery boost switch doe.
2. Yes, you can jumper them temporarily.

747Driver · 10-30-2018, 05:50 PM

I would only do this for emergency. One reason to keep the "systems" separate is you will always be able to use the other. If you can start your RV engine, it will, in time, charge your coach battery. If you jump them, you could end up with three low batteries and unable to start your RV engine. Your RV engine takes more "umph" to start than you generator. The booster switch is there because we can almost always start the generator and charge the coach batteries, but if your chassis battery runs down, the coach batteries may be your only source, other than the normal jumping from someone else.