2x6=12 and 2x12=12 but which way to go?

[Cayuse]

So, for the past 4 years I've been running two flooded 12 volt batteries in parallel being charged by 2x100W solar panels on the roof running through a 30Amp PWM controller and all has been right with the world until recently when one of the batteries went bad so I figure I'm going to replace both since they are of the same age.

The question is am I better off putting two 6V in series instead of just replacing the 12V batteries? From talking to the local interstate battery it sounds like I really wouldn't gain that much Ah wise by installing the 6V as the height restriction in the FWC won't allow me to put something 13" tall under the couch so each battery would only be around 235Ah and I can get close to 300Ah with a couple of 12V batteries for less money and will fit in my current battery boxes.

What am I missing here?

BTW, I've never had an issue with running out of power and was at around 220Ah with the battery setup that had been in.

 

[Wandering Sagebrush]

The 6 volts typically are real deep cycle, versus the typical dual purpose 12 volt RV/marine flooded batteries that many boats and RVs use. If the parallel 12 volts work for you, why not stay with them, they’re inexpensive and easy to find. In the boat and trailer, I replace them about every 3 to 4 years. In the Bobcat, I stay with AGMs.

 

[ardvark]

Wow, this topic can be debated and is on the Internet. Historically using 6-volt golf cart batteries in series was proselytized a the gospel for RVs. The argument was the plates in a 6-volt are thicker and more tolerant of discharge/recharges cycles and plenty of folks still hold to that. More recently the debate has been restated as given equal amp hours, it makes no difference which deep cycle you choose. They will last equally as long. I think you will find this stated in a multitude of places on the Internet and the contrary also stated. Maybe there is a site that has already done a comparison.

My thought is, what you had was working fine for you. Changing to 6-volts sounds like it will cost you some amp hours. Whether is will increase longevity is perhaps open to debate. I prefer AGMs over flooded cells.

 

[Optimistic Paranoid]

I was just about to post the same info when Wandering Sagebrush's reply popped up. He is absolutely right.

But I will ask one additional question. How long do you plan to keep this rig?

As a general rule of thumb, 12 volt RV/Marine "Deep Cycle" batteries are good for approximately 400 to 500 cycles, a cycle being discharging a battery down to about 50% capacity and then recharging it back up to 100%.

TRUE Deep Cycle batteries will often go 1,000 to 1,200 cycles or more. It's not unknown for RV's with good 6 volt batteries in them to go 7 to 10 years.

Btw, I've been told - by someone I trust to know what he's talking about - that TROJAN builds the only TRUE deep cycle 12 volt batteries, Everyone else's 12 volt "deep cycle" batteries are RV/Marine. Their T1275 batteries actually weigh 85 lbs. each. TRUE Deep Cycle batteries have a LOT of lead in them.

 

[Cayuse]

How long will I keep the rig? Who knows... I'd like to say a long, long time. Certainly don't have any plans for getting rid of it anytime in the foreseeable future.

Not sure that cycling is as huge a deal with the solar on the roof, I'm still well over 12.2V in the mornings when I check the batteries and that would be after running the furnace and lights at night. just trying to figure out if there is a real strong case to be made for going to 2x6V knowing that I won't gain much in Ah but maybe in duty cycles?

Sounds like 3-4 years is expected life so maybe stick with what works.

AGM would be convenient but not sure it pencils out $$$ wise.

 

[ckent323]

Cayuse,

There are links to a lot of good battery information here:

http://www.wanderthewest.com/forum/topic/15574-ultimate-battery-thread/


You can find the differences between battery types and details about those battery types (including charts on discharge vs lifetime) as well as learn that there are manufacturers besides Trojan that make true deep cycle batteries (e.g. Rolls-Surrette, Concord/Lifeline, etc)

Regards,

Craig

 

[ardvark]

Yeah, there are several brands of good deep cycles. As always it may be a question of balancing cost with lifespan.

 

[Vic Harder]

How long will I keep the rig? Who knows... I'd like to say a long, long time. Certainly don't have any plans for getting rid of it anytime in the foreseeable future.

Not sure that cycling is as huge a deal with the solar on the roof, I'm still well over 12.2V in the mornings when I check the batteries and that would be after running the furnace and lights at night. just trying to figure out if there is a real strong case to be made for going to 2x6V knowing that I won't gain much in Ah but maybe in duty cycles?

Sounds like 3-4 years is expected life so maybe stick with what works.

AGM would be convenient but not sure it pencils out $$$ wise.

I've got 220AH of Rolls 6v AGM batteries in my rig. in 50 days of use, only 1 cycle so far. At this rate, the batteries will outlive me.

 

[rando]

Maybe a silly question - but do you really need 2 batteries? If you are > 12.2V in the mornings you are > ~60% SOC. With one battery you would still be > 30% SOC, which is still OK. Running your battery down to 30% will shorten battery life, but one battery costs half as much, so the battery only needs to last half as long, and more importantly weighs half as much.

 

[JaSAn]

IMO go with what has worked for you if you are happy with the life you got out of the current batteries. If you want to try something different you cannot get cheaper $$ per AH per year than East Penn/Deka 6V GC2s. I bought my pair 5 years ago for $86/ea. and they are still measuring 1.27+ specific gravity being used 100+ nights a year.

The big advantage of GC batteries is they are the cheapest true deep cycle batteries. The big disadvantage is if one goes bad you cannot just disconnect that one and limp along until replacement.

For way more information than you probably want, Mainesail did an exhaustive comparison of FLA batteries a couple of years ago:
http://www.pbase.com/mainecruising/deep_cycle_battery&page=1

As an aside, for those of us that learned a lot about solar from HandyBob, he has new information on what he has learned about charging voltages: https://handybobsolar.wordpress.com

jim

 

[Wandering Sagebrush]

Interesting discussion. I finally got the Bobcat back on my truck, and noticed that the solar wasn’t charging the battery, and it was discharging without a load. My guess is I let it stay in covered storage too long, and the battery was too low for the solar to see it. The battery is an East Penn Intimidator Group 24 AGM. I’ve got it on AC now, and will check it after it has come up to proper voltage, then sat long enough to drop back down to full charge.

 

[Optimistic Paranoid]

As an aside, for those of us that learned a lot about solar from HandyBob, he has new information on what he has learned about charging voltages: https://handybobsolar.wordpress.com

jim


Thanks for posting that. I hadn't been back to his site for a while since he hadn't posted anything new in a long time.

 

[pvstoy]

So, for the past 4 years I've been running two flooded 12 volt batteries in parallel being charged by 2x100W solar panels on the roof running through a 30Amp PWM controller and all has been right with the world until recently when one of the batteries went bad so I figure I'm going to replace both since they are of the same age.

The question is am I better off putting two 6V in series instead of just replacing the 12V batteries? From talking to the local interstate battery it sounds like I really wouldn't gain that much Ah wise by installing the 6V as the height restriction in the FWC won't allow me to put something 13" tall under the couch so each battery would only be around 235Ah and I can get close to 300Ah with a couple of 12V batteries for less money and will fit in my current battery boxes.

What am I missing here?

BTW, I've never had an issue with running out of power and was at around 220Ah with the battery setup that had been in.

Some key points you mentioned,
4 years been using 2 flooded 12 volt batteries without problems. Then replace the two batteries and continue having worry free more years.

You have a Height restrictions to 13 inches then why bother trying to fit 10 pounds of stuff in a 5 pound bag. Keep it simply like the way you have it now.

Never had a issue with running out of power then suggest maintaining that success.

Unless you want to spend more money and time modifications to change to something else...... seems like it works and has been for you. Cheers.

 

[Cayuse]

Some key points you mentioned,
4 years been using 2 flooded 12 volt batteries without problems. Then replace the two batteries and continue having worry free more years.

You have a Height restrictions to 13 inches then why bother trying to fit 10 pounds of stuff in a 5 pound bag. Keep it simply like the way you have it now.

Never had a issue with running out of power then suggest maintaining that success.

Unless you want to spend more money and time modifications to change to something else...... seems like it works and has been for you. Cheers.

Good points all. I guess it's just trying to figure out if there's a better option but other than going 12V AGM I think sticking with what I have probably makes the most sense.

Sent from my SM-G965U using Tapatalk

 

[Mighty Dodge Ram]

One caveat that I may have missed reading but deserves re-mentioning...if you go with the typical 6v golf cart battery (FLA) they must be sealed from the interior and vented to the outside; they are not sealed unless you get AGM (SLA). Additionally, they require some maintenance but to be honest, I never check the two Kirkland 6v I have in the motorhome and they just keep on giving me power. As usual, there is a significant price difference between the two types.

Great discussion and tips here...I’m a battery/solar newb so looking forward to your eventual solution.

 

[Wandering Sagebrush]

Interesting discussion. I finally got the Bobcat back on my truck, and noticed that the solar wasn’t charging the battery, and it was discharging without a load. My guess is I let it stay in covered storage too long, and the battery was too low for the solar to see it. The battery is an East Penn Intimidator Group 24 AGM. I’ve got it on AC now, and will check it after it has come up to proper voltage, then sat long enough to drop back down to full charge.

Quick update: I plugged in overnight, and brought the battery up close to full charge, the solar has kicked in and the battery is topping off.

Note to self, remember to charge the battery when it’s in storage.

 

[ckent323]

Mighty Dodge Ram,

It is my understanding that all lead acid vehicle batteries require at least some maintenance. Some more than others (FLA for example).

Also all lead acid batteries 12v and 6V should be vented that includes AGM and GEL batteries.

Even though AGM and GEL batteries batteries are normally sealed, they actually do have a venting system integrated into the case top.

In the event of an overcharge condition, it is possible for excess pressure to build up inside the battery.

These batteries are equipped with check valves that are engineered to open at between 2-3 PSI depending upon the specific brand. What will be expelled is hydrogen gas, and you do want to vent that to mitigate any risk of explosion.


Regards,


Craig

 

[Mighty Dodge Ram]

Agreed that all batteries vent in greater or lesser degrees. I could be wrong (I frequently am!) but my understanding is that sealed lead acid (SLA) batteries do not “require” outside venting whereas flooded lead acid (FLA) batteries...not sealed and requiring electrolyte monitoring/servicing...do require outside venting. I have several friends with truck campers and it does not “appear” that their SLA batteries are externally vented. But I’m no expert and don’t own a truck camper...yet.

The 6v FLA golf cart batteries in my motorhome, located outside the coach under the entry steps, give outstanding service while boondocking but I seldom if ever check them. Bad on me, but COSTCO loves the business. I think my point should have been the difference in service requirements, exclusive of storage/charging, for each type of battery.

Thanks for the clarification.

 

[ckent323]

I have two AGM 6V batteries in battery cases in my camper under the rollover couch and those cases are vented with t" diameter flexible tubing to holes in the turnbuckle "doors" under the rollover couch. (i.e. the battery box tubes connect the battery box directly to the exterior of the camper)

Most of the time the venting is not needed but if something happens and they do vent I want that highly flammable gas to be able to escape away from the interior of the camper or at least have air able to circulate in the boxes into which the Hydrogen can diffuse (Hydrogen diffuses into air pretty rapidly).

 

[JaSAn]

ABYC code does not require (it recommends) venting for LA batteries. What it does require is that there not be any ignition sources (like a charge controller) in the same compartment as the batteries. ALL lead acid batteries will discharge explosive and corrosive gasses when overcharged or heated, FLA at atmospheric pressure, AGM and GEL at a little over. Some people are very sensitive/allergic to the vented sulfuric acid.

jim