Why would one battery of 3 be very low on water?

[TimLoon]

Have had the MH 5 years (2004 model) and the current set of batteries is 3 years old. I run 3- 6 volt(not looking for opinions on this unless relative) and have never had an issue. Today while getting ready to cover I decided to check battery fluid levels. Two were fine and the third was very low. The low battery was the independent battery wired in series. Rarely do I need to add water and MH is always plugged in when not on the road. Any ideas what could cause this?

[enblethen]

You could go up to Interstate 2400 which are about 250.
Dollar value GC-2 from Costco.
Really depends on how much dry camping is done.

[Boon_Docker]

TimLoon wrote:
Well, at least it was an interesting discussion. Last question: With 3 battery spaces, am I better off with the 2-6V or 3 - 12 volt? If 3-12V, what batteries would be best knowing I have the space to accommodate the 6V size batteries? Will probably be adding another solar panel in the spring.

For a comparison:

Two GC2 (6v) will give you 225ah
Two Trojan T-1275 (12v) will give you 300ah
So three T-1275 (12v) will give you 450ah

The T1275 is the same width as the GC2, but almost 3 inches longer.

[Bobbo]

12v group 24 batteries run about 80 amp hours each, so 3 of them would give you about 240 amp hours.

12v group 27 batteries run about 90 amp hours each, so 3 of them would give you about 270 amp hours.

12v group 31 batteries run about 125 amp hours each, so 3 of them would give you about 375 amp hours.

6v golf cart batteries give you about 220 amp hours, so 2 of them give you about 220 amp hours.

This web site has useful general information:

http://www.batterystuff.com/kb/tools/bci-battery-group-sizes.html

[wolfe10]

OK, for future, tell us exactly the dimension of your battery compartment. THEN we can recommend "best fit" for your needs.

Also, tell us how much you dry camp.

Also, tell us what converter, charger or inverter/charger you have.

ALL are important issues if you are looking at your 12 VDC system.

BTW, there ARE some deep cycle 12 VDC batteries-- but many fall into the "expensive" category-- AGM's.

[DrewE]

I would try the two (good, currently parallel) 6V batteries you have and nothing more. If that's sufficient capacity for your needs, then you're all set to go and you don't need anything more. That should be basically the same capacity you had with the three 6V batteries initially, by my thinking, and quite possibly more than you currently have with the one cooked battery included.

If you want to spend lots of $$$, landyacht's advice is probably about the best you'll be able to do.

If you want to spend lots and lots and lots of $$$$$$$, you could probably find some way to cobble together a Li-ion battery bank (and put in the requisite chargers and control circuitry) that would have a much higher capacity.

[landyacht318]

NO 12 volt flooded battery is actually of deep cycle construction, except the Trojan t-1275/j150 or J185, and a few offerings from Rolls Surrette. They are all hybrid closer to a starting battery in construction than they are to a golf cart battery.

At best a 12v group31 battery is a marine battery with plate thicknesses half that of a T-105.

If you can fit three T-1275's in the space, they will likely be the most AH you can get of true deep cycle battery.

http://www.trojanbattery.com/pdf/datasheets/T1275_Trojan_Data_Sheets.pdf

Trojan's T-1275 is rated for twice the cycle life compared to their own group31 12v battery. 1200 'Lab cycles" to 50% as opposed to 600 lab cycles.

http://www.pbase.com/mainecruising/deep_cycle_battery

[TimLoon]

Well, at least it was an interesting discussion. Last question: With 3 battery spaces, am I better off with the 2-6V or 3 - 12 volt? If 3-12V, what batteries would be best knowing I have the space to accommodate the 6V size batteries? Will probably be adding another solar panel in the spring.

[NinerBikes]

TimLoon wrote:
I would take a picture however batteries were pulled this morning and put in the basement on maintenance chargers. I have a spare 12V that I put in their place for the winter to be able to start generator monthly. Not sure why I am being accused of being a troll, I am active on a several RV forums. For the record, 2 in parallel to one in series. Don't know any other way to reach 12V with 3 6V batteries. Will try 2 6V in series in the spring to see if I have a different experience with accommodating the load we normally put on our system. No salesman involved in my original purchase. These were from a commercial distributor not open to retail customers.

Good on ya... who's idea was it to use three 6V batteries in a 12 V system? They deserve an award of sorts... we just haven't figured out for what, besides fully filling existing space for batteries.

[tenbear]

No one mentioned the physics behind your problem so I will try.

The single battery would be providing 2x the current than the others, therefore it gets discharged faster and deeper than the other 2. It also gets charged 2x as fast. The result is that it fails sooner than the other two.

You could run this way if you switched the batteries every few weeks so that all the batteries were in the single position for the same length of time. You should also monitor the single battery so it does not get discharged below about 6.05v, equivalent to a 12v battery discharged to 12.1v.

Probably easier to use 2 6v batteries.

[Boon_Docker]

:B

[TimLoon]

Thanks BoonDocker. This all makes sense as my wife said I need to trim my ear hair.

[enblethen]

From OP's post:
"These were from a commercial distributor not open to retail customers"
That is even worse. They should have known better.

[TimLoon]

I would take a picture however batteries were pulled this morning and put in the basement on maintenance chargers. I have a spare 12V that I put in their place for the winter to be able to start generator monthly. Not sure why I am being accused of being a troll, I am active on a several RV forums. For the record, 2 in parallel to one in series. Don't know any other way to reach 12V with 3 6V batteries. Will try 2 6V in series in the spring to see if I have a different experience with accommodating the load we normally put on our system. No salesman involved in my original purchase. These were from a commercial distributor not open to retail customers.

[2oldman]

I'll be darned if I can come up with any other way to make 12v from 3-6v batteries.

[Almot]

2oldman wrote:
Is there something unclear about the OP's description?

Initially, yes. On the 2nd page he made it more-less clear. Either configuration is not how it should be done, and loss of water is the proof.