12V or 6V Batteries - Which charge Better?

[ron_dittmer]

I plan to switch to two 6V batteries in series, but before I do, I need to ask this question.

When the batteries are drained and in need of charging, which will charge back up to full FASTER? Two 12V in parallel or two 6V in series? Most of my charging is done using the generator so faster charging times is highly desirable.

[ron_dittmer]

pnichols wrote:
Thanks Ron for getting back to me on this. I was just curious about what changes you may have had to make in order to switch over to 6V batteries. I notice that you chose AGM when you went to series sixes.

We've always had good luck with 12V batteries, but it's always been AGM deep cycle that we have used.

So far, no one has been able to explain what reliability or performacne differences there might be between 6V AGM and 12V AGM.

Sure thing!

You ask a good question...Is there is a difference in performance between two 6V AGMs in series and two 12V AGMs in parallel? I don't know.

[pnichols]

Thanks, Ron, for getting back to me on this.

I was just curious about what changes you may have had to make in order to switch over to 6V batteries. I notice that you chose AGM when you went to series sixes.

We've always had good luck with 12V batteries, but it's always been AGM deep cycle that we have used.

So far, no one has been able to explain what reliability or performance differences there might be between 6V AGM deep cycle batteries and 12V AGM deep cycle batteries.

[ron_dittmer]

realokie wrote:
Really appreciate what I have learned on this topic on this forum. I have a pair of 6 volt batteries that were installed on my TT in April of 2012. I feel they are not performing as well as they did a year ago. At their age should I go ahead and replace or get them tested first.

So your wet acid 6 volt batteries went into service over 5 years ago? I think you did pretty good with them, and maybe you are not yet done with them. With both sets of past 12 volt wet acid batteries we had, each pair degraded after the second year. The way I see it, you got 2.5x what you would have gotten if they were 12 volts which sounds about right from the estimates I was given. If they were AGM batteries, I understand they go longer yet. How Much? I don't know.

If weak batteries will ruin your next trip, then consider replacing them. If you plan to have shore power often at your destinations, I would surely let them ride.

[ron_dittmer]

pnichols wrote:
Ron,

Did your PC come stock with that being the battery compartment as shown in your photo, or was the stock battery compartment located under the step - like it is in our Itasca?

Why did you go with 6V golf cart size AGM batteries instead of 12V AGM deep cycle batteries?

I have to use 12V AGM batteries because 6V golf cart size batteries will not fit in our stock battery storage area under the step and I did not want to give up a regular storage compartment just to use golf cart size batteries. Our 12V AGM batteries are deep cycle ones - just like 6V golf cart batteries are deep cycle batteries. Some folks think you have to switch to golf cart batteries to get deep cycle construction ... but that's not true when you enter the AGM world. The capacity of our two 12V AGM deep cycle batteries in paralllel with each other is 230 amp hours.

P.S. I'm really curious as to why your 2014 discussion suddenly appeared as a 2017 topic even though all posts were back in 2014 (except for my recent post above questioning the dates, which seems to have resurrected it)? What On Earth is up with this forum software?

(Your discussions are always good ones, anyway!!)

Hi pnichols,

How this 3 year old topic came back to life, seemingly by itself? The only thing I could think of is that someone found this old topic and replied to it, then deleted his reply.

Regarding my battery compartment. It is the original compartment. I only modified the interior of it to accommodate taller 6 volt batteries. I went with AGM instead of wet acid technology primarily because of the difficulty it would be to check fluid levels. I eliminated the roll-out battery tray to gain the required height. With that tray eliminated, I would have to disconnect and then man-handle the 6 volt batteries to check cell levels.

I decided to go with two 6 volt batteries in series instead of two 12 volt in parallel because of input from people with knowledge in battery technology, both on RV forums and also electrical power management engineers where I worked at the time. Their input coincided with my past troubles with pairs of 12 volt batteries. Batteries in parallel, one will always drain much faster than the other which brings down the performance of the twin battery pack. With two 6 volt batteries hooked up in series, the two are kind-of forced to drain at the same rate which increases battery reserves and also balances their charging rate. They work much better as a team than 12 volts do.

It also made sense to me when looking at everything else that is battery-powered. From flashlights to electronic devises, they all stack batteries in series, almost never in parallel. When in series, the batteries in hand-held devises last much longer and die close together.

Does all this make sense?

I am no authority on this stuff. It's only what I understand the facts to be.

Ron Dittmer

[realokie]

Really appreciate what I have learned on this topic on this forum. I have a pair of 6 volt batteries that were installed on my TT in April of 2012. I feel they are not performing as well as they did a year ago. At their age should I go ahead and replace or get them tested first.

[pnichols]

Ron,

Did your PC come stock with that being the battery compartment as shown in your photo, or was the stock battery compartment located under the step - like it is in our Itasca?

Why did you go with 6V golf cart size AGM batteries instead of 12V AGM deep cycle batteries?

I have to use 12V AGM batteries because 6V golf cart size batteries will not fit in our stock battery storage area under the step and I did not want to give up a regular storage compartment just to use golf cart size batteries. Our 12V AGM batteries are deep cycle ones - just like 6V golf cart batteries are deep cycle batteries. Some folks think you have to switch to golf cart batteries to get deep cycle construction ... but that's not true when you enter the AGM world. The capacity of our two 12V AGM deep cycle batteries in paralllel with each other is 230 amp hours.

P.S. I'm really curious as to why your 2014 discussionn suddenly appeared as a 2017 topic even though all posts were back in 2014 (except for my recent post above questioning the dates, which seems to have resurrected it)? What On Earth is up with this forum software?

(Your discussions are always good ones, anyway!!)

[ron_dittmer]

Hi pnichols,

The only thing I can say for certain is that I started this discussing November 4th, 2014.

Since the subject has been brought back to life, I might as well report on my decision and how it's been going.

I did buy the two 6 volt AGM batteries from Sams Club. I got them to fit with some light modification to my motor home battery compartment. The 6 volt batteries are taller and so their extra height was compensated by removing my roll-out battery tray which stood taller than a simple flat plate bottom.

As instructed in my Tripp-Lite whole house inverter owner's manual, I needed to change the setting inside it to work with AGM batteries. This was done by moving a jumper on it's control panel. I believe the change increases the charging voltage by a small amount but I am not certain of it.

I've had the same 6 volt AGM batteries now for 2.5 years. We took two long trips with them and I had immediately noticed the improvement in battery longevity as compared to two new 12 volt batteries. Going through 2 sets of 12 volt batteries prior, at this point with two seasons behind, the 12 volts would have degraded at this point, but my two 6 volt AGM batteries still act like I bought them just last week.

I am very happy with my decision to change from two 12 volt batteries to two 6 volt AGM batteries. My decision to go with AGMs instead of wet acid was primarily because I gave up the battery tray to make them fit. Without the tray, the only way to check fluid levels would have been to disconnect and remove each battery. Now it's a hand's free experience with clean battery terminals too. I should have done this when changing out the original batteries back in 2011/2012.

No fuss, no mess, clean terminals, more power, and longer life, our 6 volt AGM batteries have been a great improvement to our Phoenix Cruiser motor home. I believe every Phoenix Cruiser made in recent years comes with wet acid 6 volt batteries. If I were ordering a new P-Cruiser, I would pay the extra money to have the factory install 6 volt AGMs, just so I never have to mess with those dang things.

Here is our Phoenix Cruiser battery compartment with the two 6 volt AGM batteries. They just fit with barely enough room to attach the battery cables afterward.


If wondering, this is with the battery compartment closed-up.

[pnichols]

What's going on with the forum's software????

Clicking on this discussion thread with supposedly it's latest post (not counting this one from me) from ron.dittmer being dated as "07/26/17 05:26pm" ... when I go to the end to read Ron's latest post ... it's dated as being posted by Ron on "11/07/14 12:01pm".

Just before I posted, was this a 2014 time-frame discussion thread or a 2017 time-frame discussion thread?

[ron_dittmer]

I found Sam's Club sells 6V Duracell GC2AGM AGM batteries HERE for only $179.73. Comparing that to their Duracell 6V EGC2 standard lead acid batteries Here at $112.68, the $67 per battery cost increase is worth going with the AGMs. The dimensions are identical and the Ah ratings are real close.

With so much AGM support, I think I'll buy them.

[Dakzuki]

mda wrote:
I went with Trojan Group 27 AGM in my motor home for similar reasons. I have PD 4645 multistage converter. I have found that the battery charges fairly quickly using the genny. Not sure, I am no battery expert, but I believe AGM's are more efficient. I can tell you, though it was expensive, the battery is a brute when it comes service.

AGMs are more efficient. They have less internal resistance so less energy is used to create heat when charging and (more importantly) discharging. I prefer to use the energy of the batteries to run my RV lights etc rather than heat the underside. That internal resistance is also what factors into charging times.

[Dakzuki]

Snowman9000 wrote:
This is our 4th RV. I keep saying "when these batteries go, I'm getting AGMs". But each time we replaced the RV before the batteries went.

When these batteries go, I'm getting AGMs.
🙂

Mine went. I got AGMs.

[Dakzuki]

pnichols wrote:
The above comments raise an interesting question: Is there any performance difference between using two 6V wet cell batteries versus using two 6V AGM batteries in an RV?

AGMs charge faster assuming you don't hit the limit on the charger.

[Snowman9000]

This is our 4th RV. I keep saying "when these batteries go, I'm getting AGMs". But each time we replaced the RV before the batteries went.

When these batteries go, I'm getting AGMs.
🙂

[Matt_Colie]

pnichols wrote:
The above comments raise an interesting question: Is there any performance difference between using two 6V wet cell batteries versus using two 6V AGM batteries in an RV?

I am actually answer that with specific experience.

The answer is YES. Can You afford it is another question.

Before the depression, I did a massive re-fit on a performance cruiser and the owner wanted to keep his existing house bank, but charge it more effectively. We did that (and some other things) and it all worked as expected. It worked well for a month and then a cell shorted. He (the owner) had a friend that did UPS stuff. Said friend got him a deal on a pair of AGMs with similar package and rating. The owner immediately reported shorter charge times at higher current (we had installed a very well instrumented charging system) and also longer run times before the low voltage threshold. This was interesting as we had not yet corrected the alarm for the AGM.

Matt