Need some battery advice!

[Powerstroke2000]

I'm currently having had an issue with my Interstate 12V (dual) batteries in my Arctic Fox camper, in that after 3 days of boon docking, my fridge stopped working, thus realizing I must be below 6 volts of power (was told the fridge needs 6V to run while on propane). After the 3 days we where back on the road, so the truck charged the batteries to the point where the fridge would run fine, and after that we stopped where we would have shore power for the few nights prior to heading home.

I did pull my batteries and put them in my garage on a piece of carpet and my 4 stage charger started out showing 25% power in the battery, and within a half hour it was up to 100%. I'm unsure if this is a true 100%, or if the charger has been fooled in some way, as it didn't take long to get to where it should have been. I say this, as I put this same charger on my wife's car, where she was having no battery issue, but when I put it on it showed her battery at 50% and it took overnight and into the late morning before 100% showed. My charger breaks down the sulfation process, but whether the battery is at a true 100% I don't know on this camper battery. I have another 12V interstate (currently in the camper which I'll change out with the charged one) and see how long that one takes as well. I think these batteries are about 5+ years old, but we're thinking of perhaps going to a motorhome, so I don't know if it's worth spending the $$ to change them out, or if a full charge and maintenance through the winter (if it didn't sell) is worth it?

[jkwilson]

KX5002 wrote:
I think it's an old wives tale...
All batteries are internally wired in series. A lead acid cell produces 2 volts (roughly), in order to get a higher voltage you need to array cells together in a "battery" so a 6v battery is just 3 2v cells wired in series, two 6v batteries wired in series is 6 2v cells wired in series, just the same as a 12v battery is 6 cells in series. 2 12v batteries paralleled in my mind is the same as one very large battery of 6 cells.
Am I nuts?

Not being a psychologist or psychiatrist, I'll pass on evaluating your sanity, but I am an electrical engineer who spent considerable time testing and evaluating batteries that perform one of the most critical missions on earth so I'll try your battery question.

You are correct about the cells. The term battery has the same meaning here as it does in military use. It's a grouping of guns to increase firepower or a grouping of cells to increase voltage. It was very common in the past to have the cells individually wired to make whatever voltage you needed. So two 6V batteries in series is only different from a single 12V battery because one of the wires connecting the cells is external on the 6V pair. We used to separate batteries with bandsaw to do individual cell testing.

As far as connection two 12V or 6V batteries in parallel, there are a few "gotchas" but no general reason not to:

You don't want to connect batteries of different capacity or condition in parallel.

A parallel connection can fool the charger into overcharging the batteries a little bit because the charger keeps charging until the total charging current for the two batteries is 1A rather than the charging current for the string being 1A. This can be mostly remedied by keeping an eye on the electrolyte level which you should be doing anyway.

If you have a single cell fail in a parallel collection of batteries, you may discharge the other battery, leaving you without power, or you may cause the charger to keep trying to charge both, boiling the electrolyte away ruining all the batteries.

But if you match up your batteries and monitor them properly, the advantages outweigh the minor rare issues.

[KX5002]

I think it's an old wives tale...
All batteries are internally wired in series. A lead acid cell produces 2 volts (roughly), in order to get a higher voltage you need to array cells together in a "battery" so a 6v battery is just 3 2v cells wired in series, two 6v batteries wired in series is 6 2v cells wired in series, just the same as a 12v battery is 6 cells in series. 2 12v batteries paralleled in my mind is the same as one very large battery of 6 cells.
Am I nuts?

[jplante4]

KX5002 wrote:
Why wouldn't you parallel 12 volt batteries?

I found this curious as well. If you don't parallel the batteries, how do you wire them? Is one just a cold standby?

[OldSmokey]

Powerstroke2000 wrote:


I don't believe the battery area will allow 6V batteries, as they are a fair bit higher than my current 12volts, or I would! There is a battery sliding tray the batteries sit on, and a total of 8" maximum unfortunately.

batteries do come in all shapes and sizes..

[KX5002]

Why wouldn't you parallel 12 volt batteries?

[jkwilson]

Powerstroke2000 wrote:


I did pull my batteries and put them in my garage on a piece of carpet and my 4 stage charger started out showing 25% power in the battery, and within a half hour it was up to 100%. I'm unsure if this is a true 100%, or if the charger has been fooled in some way, as it didn't take long to get to where it should have been.

The charger judges the battery state of charge by how much current it takes to raise the voltage to whatever voltage the charger uses. Typically in newer chargers that's about 14.7V during the main charging process. Most chargers decide a battery is fully charged when the charger can raise it to 14.7V with 1 Amp or less. A heavily used or sulfated battery can charge very quickly because it has a very low usable capacity.

[MrWizard]

your batteries are 'toast' , burnt toast

get one new 12v battery for TT, so every thing works, in the TT for sales demo

get a $5 battery disonnect swtich a the auto parts store when you buy the new battery

put it on the battery, connect battery for demo, disconnect after the demo

all TT systems are 12v, and the battery is considered 100% Discharged at 10.5v
anything below 12.0 aka 50% is bad even for 6v batteries

things stop working in the TT below 11v, except for some lights

[MEXICOWANDERER]

You may want to consider a pair of group 29-30-31 AGM batteries which are 13" in length. Seldom mentioned on this forum is the fact that absorbed glass mat batteries in car jar sizes can tolerate FAR More (like 50 times more) complete discharges without suffering catastrophic damage. Yes the cost of AGM is high, yet in many cases any alternative to AGM would be a very poor 2nd choice.

[time2roll]

Batteries are shot. Just get new ones already. Trade or not get your trailer working properly as this is a minor issue.

[pianotuna]

Fully charge the batteries.

Then desulphate them using a 12 volt manual charger.

Do this with the jars disconnected from the RV.

When you return them to the RV wire them in a balanced manner.

[Powerstroke2000]

OldSmokey wrote:

Powerstroke2000 wrote:
I'm currently having had an issue with my Interstate 12V (dual) batteries in my Arctic Fox camper, in that after 3 days of boon docking, my fridge stopped working, thus realizing I must be below 6 volts of power (was told the fridge needs 6V to run while on propane). After the 3 days we where back on the road, so the truck charged the batteries to the point where the fridge would run fine, and after that we stopped where we would have shore power for the few nights prior to heading home.

I did pull my batteries and put them in my garage on a piece of carpet and my 4 stage charger started out showing 25% power in the battery, and within a half hour it was up to 100%. I'm unsure if this is a true 100%, or if the charger has been fooled in some way, as it didn't take long to get to where it should have been. I say this, as I put this same charger on my wife's car, where she was having no battery issue, but when I put it on it showed her battery at 50% and it took overnight and into the late morning before 100% showed. My charger breaks down the sulfation process, but whether the battery is at a true 100% I don't know on this camper battery. I have another 12V interstate (currently in the camper which I'll change out with the charged one) and see how long that one takes as well. I think these batteries are about 5+ years old, but we're thinking of perhaps going to a motorhome, so I don't know if it's worth spending the $$ to change them out, or if a full charge and maintenance through the winter (if it didn't sell) is worth it?

the clue here is "within a half hour it was up to 100%"
your batteries are sulphated and now boat anchors.
buy two 6 volt batteries of the desired capacity.
don't parallel FLA's

I don't believe the battery area will allow 6V batteries, as they are a fair bit higher than my current 12volts, or I would! There is a battery sliding tray the batteries sit on, and a total of 8" maximum unfortunately.

[BFL13]

You are just terrible with batteries :), but no matter--just buy new ones as required next year if the camper does not sell.

Don't buy any new ones now, wait till next year, since any new ones will not do well over the winter most likely in your care 🙂 Just keep the existing batts going as best you can--desulphate them like crazy--for being able to run demos during your sales pitches.

If they are so bad that won't work, you still need one batt so you can do your demos. IMO get a new starting battery for the truck even if the one there now is only a couple years old. Use the old truck starting battery as the camper battery for demos. The buyer can get proper new batts himself, instead of your old starting battery.

Then next year for yourself, play it as it lies. (A golf saying)

BTW ignore those who say don't parallel 12s. I have a pair of Trojan 1275s in parallel, doing just fine thanks. What else could you do with them anyway? Bizarre. Oh, and also a pair of 12v deep cycle AGMs 100ah each. Of course they are in parallel.

[OldSmokey]

Powerstroke2000 wrote:
I'm currently having had an issue with my Interstate 12V (dual) batteries in my Arctic Fox camper, in that after 3 days of boon docking, my fridge stopped working, thus realizing I must be below 6 volts of power (was told the fridge needs 6V to run while on propane). After the 3 days we where back on the road, so the truck charged the batteries to the point where the fridge would run fine, and after that we stopped where we would have shore power for the few nights prior to heading home.

I did pull my batteries and put them in my garage on a piece of carpet and my 4 stage charger started out showing 25% power in the battery, and within a half hour it was up to 100%. I'm unsure if this is a true 100%, or if the charger has been fooled in some way, as it didn't take long to get to where it should have been. I say this, as I put this same charger on my wife's car, where she was having no battery issue, but when I put it on it showed her battery at 50% and it took overnight and into the late morning before 100% showed. My charger breaks down the sulfation process, but whether the battery is at a true 100% I don't know on this camper battery. I have another 12V interstate (currently in the camper which I'll change out with the charged one) and see how long that one takes as well. I think these batteries are about 5+ years old, but we're thinking of perhaps going to a motorhome, so I don't know if it's worth spending the $$ to change them out, or if a full charge and maintenance through the winter (if it didn't sell) is worth it?

the clue here is "within a half hour it was up to 100%"
your batteries are sulphated and now boat anchors.
buy two 6 volt batteries of the desired capacity.
don't parallel FLA's

[grizzzman]

2oldman wrote:

Powerstroke2000 wrote:
thus realizing I must be below 6 volts of power (was told the fridge needs 6V to run while on propane).

I did pull my batteries and put them in my garage on a piece of carpet

You were told wrong, and you should be carrying a voltmeter.

Why did you mention a piece of carpet?

My best guess that he believes the cement floor will drain his battery. Although it was true "long ago" That ship has sailed.

[mbopp]

That's the problem with 12V batteries in parallel - a bad cell in one battery will drag the good battery down. I'd have them both load tested.