Dead battery dilemma

[Bobbie54]

Yes, 6 cells each. Oh, yeah, and I knew that. Just forgot! (I
used to teach it in general chemistry, lol.)

[Bobbie54]

Originally Posted by Brian B-P

If you have two of them (wired in parallel, without a switch), you can get about two-thirds of the total capacity with one larger 12-volt battery (Group 31, or maybe Group 29).

That would probably work. The battery box would need replacing but both of them are looking more brittle than a new one would be so that wouldn't hurt. I'll see what I can get locally and talk to them at LS about capacities and weights.

[Brian B-P]

Originally Posted by Bobbie54

IWhat on this tells you 12V vs. 6V? (Seems like a dumb question but I don't see voltage listed.)

Not a dumb question, given the label. The information on the website (including the table showing the whole series) provides the voltage.

Also, I've never heard of a Group 24 (or 27, or 31) battery which is not 12-volt. Typically, all batteries of a given Battery Council International (BCI) size code are all the same nominal voltage.

And of course there's the cell count, but that does require popping caps off, and on some 'no maintenance' automotive batteries they are not removable.

[John in Santa Cruz]

anyways, the only common 6V batteries in RV use are golf cart batteries like GC-2/T105. There are also some 6V tractor batteries and vintage car batteries but I've never heard of those being used in RV's.

[alanmalk]

Originally Posted by Bobbie54

Yes, 6 cells each. Oh, yeah, and I knew that. Just forgot! (I
used to teach it in general chemistry, lol.)

Counting the cells normally works just fine, but...

I knew a chemistry professor who gave a test and at the front of the class room had a 3 cell automotive battery hooked up to a small illuminated light bulb and next to it - a multi-meter and a sign that said "For 5 extra credit points, what is the voltage of this battery". Inside the hollow battery was a 12 volt battery powering everything. Not many students got the 5 extra credit points - because they didn't bother actually measuring the voltage.

[rbryan4]

Originally Posted by alanmalk

I knew a chemistry professor who gave a test and at the front of the class room had a 3 cell automotive battery hooked up to a small illuminated light bulb and next to it - a multi-meter and a sign that said "For 5 extra credit points, what is the voltage of this battery". Inside the hollow battery was a 12 volt battery powering everything. Not many students got the 5 extra credit points - because they didn't bother actually measuring the voltage.

You'd think they would have got a hint from the fact he left a multimeter on the table, eh?

[Bobbie54]

So when I look at 12V batteries- what numbers do I need to know how long the battery charge would last (compared to another battery, not in actual usage which obviously depends.)

[Bobbie54]

And questions 2 and 3- why are 2 6V batteries better, and pros and cons of maintenance free batteries. (one pro I know- I'm not the greatest about scheduled maintenance, and one con, expense.)

[tdf-texas]

Originally Posted by Bobbie54

And questions 2 and 3- why are 2 6V batteries better, and pros and cons of maintenance free batteries. (one pro I know- I'm not the greatest about scheduled maintenance, and one con, expense.)

Question 2:

https://www.youtube.com/watch?v=NjPquFVxtxs

Question 3:
"Maintenance Free" means that the manufacturer didn't provide any means of maintaining the water/acid level in the battery, which means that if a battery boils dry you can only replace it instead of refilling it yourself. They have a definite end of life - when the water inside gets too low, it's dead.

Other than that, they are pretty much the same.

ps. can you guess I don't care for maintenance free batteries? I have a filler system on my 2 6v batteries that let me check/fill the levels without taking the battery cover off and expect them to last a lot longer than any maintenance free battery would.

[John in Santa Cruz]

batteries designed for deep cycle are rated in AH (Amp*Hours). The key factor is watt*hours, which is amp*hours (AH) times volts. a group 27 marine/rv battery is typically 100AH or so, so gives 1200 watt*hours. thats 1200 watts for 1 hour, or 120 watts for 10 hours.

if you have two batteries, its better to have them in series, so all the current is going through both batteries, this way they stay better balanaced.

when you put batteries in series, you add their voltages, when you put them in parallel you add their current (or AH rating). so 2 GC-2 golf cart batteries in series, gives you 6+6 = 12V, and 210-230AH rating, for a total of about 2500-2800 watt*hours.

maintenance free batteries, aka "SLA" (Sealed Lead Acid) or "VRLA" (Valve Regulated Lead Acid) have the advantage of being sealed, so they don't leak if tipped over, and not needing periodic checking for fluid levels and topping off with distilled h2o. but they are over twice the price of 'wet cell' conventional batteries. they also require a charger with slightly different voltage levels... the one on our escapes can, I believe, be reconfigured for them, the one that came on my casita couldn't. solar charge controllers typically have a 'vrla' setting.

[Bobbie54]

Well, Les Schwab was not very helpful. They only have group 24 and 27 in 12 volt batteries, rated at 100 and 120 reserve ? which the guy claimed meant how many minutes it would run. (Which does not make sense to me.) They could order a maintenance free one that is listed at 180. He knows no weights and couldn't find them. Could give me sizes. He told me what the 6V was but I forget that. (Still no weights.)

[gbaglo]

Why not Google Interstate or Trojan and look for a "Where to Buy" tab, or contact them directly? I'm sure they can provide you with a retailer who has what you need and competent sales people.

[John in Santa Cruz]

I show a couple Napa auto parts stores on Whidbey Island. they sell good batteries.


btw, 'reserve capacity' is measured at 25 amps, and is basically how many minutes til the battery is totally dead (10.5V) at 25A load. AH is normally rated at a 20 hour discharge rate (so a 100AH battery would be rated to last 20 hours at 5 amps). you can't directly convert between these units, but in both cases, higher is better. batteries like group 27 marine/rv are typically rated in 'starting' capacity (CCA, etc) as well as "RC", while true deep cycle batteries are rated in AH.

anyways, I see Napa has house brand (look like interstate) GC2 and Group 27 Marine, and many others.

[Bobbie54]

Thanks, Napa it is, I forgot about them! Also their website has all the info I need. (I hope.) I think I found 6V to compare. (Had to google, their search function didn't find them.)

[Bobbie54]

OK, I know this has been posted before but I can't find it with the google search function. Where do I find the approximate electrical draw in amps for the fridge on propane, fan, and heater? Just trying to figure out the max I might need. I keep thinking I rarely boondock- but then remember the rally in California with the power outage that would have left me without a fan.

And also: I have a small solar panel with a male 12V plug. Would this kit let me hook it up to the battery (whatever I end up with?)
https://www.harborfreight.com/solar-...kit-68684.html

[John in Santa Cruz]

Originally Posted by Bobbie54

OK, I know this has been posted before but I can't find it with the google search function. Where do I find the approximate electrical draw in amps for the fridge on propane, fan, and heater? Just trying to figure out the max I might need. I keep thinking I rarely boondock- but then remember the rally in California with the power outage that would have left me without a fan.

which fridge, fan, and heater model do you have? look up their specs on the appliance maker's website.

a Maxxfan draws like 0.2 to 5 amps depending on speed.

a RV fridge on propane uses very little electric.

the Atwood furnaces use like 3.4 amps when the fan is running... most of the time I find the furnace only runs a few minutes an hour to keep things warm inside but our Escape is double insulated.

[Bobbie54]

OK, that sounds do-able with the amps and a single battery. I can add another if I need to at some point.

[John in Santa Cruz]

oh, that solar panel.... if its just a 5-10 watt 'battery keeper', I'm not sure I'd even bother, its not big enough to generate enough power to matter. i have a 100W folding panel I take when I need additional power... I used it with the Casita, where i made my own pigtail for the casita battery, using 12 gauge wire and a 'powerpole' connector. my escape has 160W rooftop solar.

[Bobbie54]

Thanks. 5.5 watts so I will save it for power outages and phone charging at home.

[Brian B-P]

Originally Posted by John in Santa Cruz

... maintenance free batteries, aka "SLA" (Sealed Lead Acid) or "VRLA" (Valve Regulated Lead Acid) have the advantage of being sealed, so they don't leak if tipped over, and not needing periodic checking for fluid levels and topping off with distilled h2o. but they are over twice the price of 'wet cell' conventional batteries. they also require a charger with slightly different voltage levels... the one on our escapes can, I believe, be reconfigured for them, the one that came on my casita couldn't. solar charge controllers typically have a 'vrla' setting.

There are flooded lead-acid batteries called "maintenance free": that's what I was referring to, that's what tdf-texas described, and they are worthless for deep-cycle operation such as in an RV. Please don't buy one for the Escape.

VRLA batteries are very different. They do not vent under normal conditions and are constructed differently internally. While they are free of electrolyte maintenance, they are not what is usually labeled as "maintenance free". The current type of VLRA battery is the AGM design.