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Keyair · 01-18-2011, 03:08 PM

I have 2 Interstate Megatron Marine Deepcycles as the Coach Batteries in my M/H. From the paperwork I got with the rig, looks like they are 3 years old.
Stupidly I left something on last month and deep discharged them down to dead.
I have no 120V at my storage, so pulled them off and recharged them at home using my new BatteryMINDER charger/desulfator.

One of them came back ok, and I just checked it after a week of resting here and it is reading 12.6V.
The other is not good, shows 10.5V and a check of the SG in all the cells tells me one is dead, and reads very low SG.

If I leave it on a Desulfating charge of 2A(Charger has 2A,4A, and 8A), is there any chance it will come back?

noreen&sal · 01-18-2011, 03:30 PM

NO. Sal.

Keyair · 01-18-2011, 03:43 PM

Ok, so let me get this straight...
If I just buy a replacement I am not "Matched" battery wise, so the new one will get pulled down to the older battery's level?

dznf0g · 01-18-2011, 03:44 PM

More or less, that's correct

dznf0g · 01-18-2011, 03:46 PM

Always replace in pairs:
1)if they are wired in parallel
2) are of significantly different age. That is maybemore than a year apart in birthdate. Also check the date codes when you buy 2 new. Try to get them within a couple of months production of each other.

Keyair · 01-18-2011, 04:30 PM

Ok, Thanks.

I have been doing some research, but am a little confused...
My reading indicate 1 cell that is not taking charge.
Now, I read that if the cell is "shorted", it will bubble more than the others and get hot?
This is not the case with my battery... the cell in question only bubbles a little, and far less than the others when i apply a heavier charge.

If I need to replace it, i will, but money is tight.
As i have some issues with my battery tray, and will need to repair it, I need to plan this new battery gig well.
The battery tray is 40"x15"x9".
Here is a photo:

I plan to remove the rearward tool storage bin to give me more space, then move the engine starter battery to the front.
As I need to cut out the whole floor, I am thinking drop the whole floor of the tray inboard of the body curve to give me space for more/ bigger batteries.

How deep are 6V's?

masseyfarm · 01-18-2011, 05:21 PM

Isn't ownership of a RV FUN.

Dave

Mexray · 01-18-2011, 05:35 PM

First, your battery with 10 volts is a goner...It's 'shorted' internally, from either 'curd' piling up from the bottom of the case (unlikely), or a spot in a separator has worn through, allowing two adjoining plates to touch...in any event, there's nothing you can do to fix it at this stage...

If you wish to replace with the golf car style, 6 volt deep cycles, you'll need a bit more clearance on top, as they are about 2 inches taller than you 12 volt batteries - their 'footprint' is 10 x 7 inches - about the same length, but about 1/2 inch wider than the 12 volt's you now have..

The 6 volt batteries are a good choice if you need to run your 12 volt stuff for a longer period when off 'shore' power.

samb · 01-18-2011, 05:46 PM

Give the desulfation a chance to work. The cost is right. I had one battery that my charger and a battery minder both said was bad and needed replacement. I let a desulfate mode on a different charger run for about six days and the battery finally took a good charge. Voltage reading after removed from the charger for 10 days was 12.67.
I don't know how long it will last in use, but I plan to give it a good test.
You don't have anything to lose by giving it a try.
As for running different age batteries together ......... I have no idea.
Sam

345bill · 01-18-2011, 05:50 PM

Quote:

Originally Posted by Keyair

the cell in question only bubbles a little, and far less than the others when i apply a heavier charge.

Any battery with a bad cell that I ever had acted exactly as yours or that particular cell would not bubble at all.

masseyfarm · 01-18-2011, 06:01 PM

I would say, even if you got it back to fair SG with extended charging, and tried to use it with the other battery, your charge system would just work overtime from the heavy demand. That cell will never again charge as quickly as the other cells will.
Question is -- new batteries or new alternator?

The same thing can happen to 4 X 6V. Just ask me.

Out of the 4 X 6V I had, I picked the best pair, and used them on my home alarm system, charged with solar. I figure the alarm will run for about a week, before the Trojan T105's run down.
Dave

Jammer · 01-18-2011, 07:48 PM

Mexray is right.

If money is tight just scrap the bad battery and run with only one battery until you can afford replacements.

TG Twinkie · 01-19-2011, 07:11 AM

I agree with Jammer. Use 1 battery; and unless you do a lot of dry camping and need the extra capacity, stick with one battery.

garry · 01-19-2011, 07:32 AM

Since I do very little dry camping I went from 3 group 24's to 1 group 27 from Cosco and it works for me.

Ahab · 01-19-2011, 08:22 AM

I learned to change out batteries after 3 years. Anything after that time is a crap shoot. Yes, I know of people who claim longer life but I don't like getting caught in the middle of no-where with a dead battery.

Keyair · 01-19-2011, 10:55 AM

Thanks Peeps!
I will be just running with the 1 battery for a bit as you said Jammer.
Will leave the dead one on the 2A desulfating charge for a bit and see if it would work a miricle!
I might even try the old drain, flush and Epsom salt cleanse for a laugh!
As Samb says... the price is right!

I am not driving the M/H for a couple more months, so I can just use the one battery.
Anyone care to comment on how Aluminum Diamond plate would do as a tray bottom?
I think I will drop the drawer bottom by about 2", to give me enough height for 6V Golf Cart Batteries(11" tall) if I decide thats the best option later.

bryanl · 01-19-2011, 11:48 AM

If you ran down your batteries to zilch, they are suspect and should be replaced unless you like to take risks of low battery at unexpected times. Often times you can get away with a few accidental deep discharges but if you have a battery showing indications of a bad cell, replace it.

The only recovery for a bad cell is to rebuild the battery and that is not practical for any battery you'd find in a typical RV. In the whole scheme of things, batteries are really not that expensive these days.

re: "the new one will get pulled down to the older battery's level?" -- If there is a bad battery with a cell failure, this is true as the voltages of all batteries in parallel are held to the same level. But in most cases (80%) or so, batteries fail by sulfation and paralleling a new battery with an old one of the same type and chemistry won't harm the new one. The only caveat is that it will be doing most of the work and that might age it a bit faster.

Keyair · 01-22-2011, 07:42 PM

Ok, absorbing all this info slightly better than my bad battery absorbs charge!

So, here is a question...

I have about $300 in Costco credits.
Marine Deep Cycles cost $68 each.
Golf Cart 6V are $78 each.
I cant find the specs on either online and didnt write them down...

What is the best way to go?

Airslide · 01-22-2011, 08:17 PM

I personally would stick with the "marine deep cycle" batteries and the $68.00 dollar price sounds really good.

Vinnie

ROBERTSUNRUS · 01-22-2011, 09:32 PM

Hi, my batteries lasted about three years, each time. I have replaced my batteries twice with Costco group 24 deep cycles. So from my experiences, you have one bad battery, and the other one will soon follow. One time, I knew I wasn't going anywhere for several months, so I waited before buying new ones. No use burning up warranty time while just sitting in storage.