Batt discharge rate

[tarnold]

I have two 12v deep cycles, will be 3 years old next month(warranty)
Batt 1 was charged to 13.4v, next day 13.05 then 12.71 then 12.61 then 12.53
Batt 2 was charged to 13.64v, next day 13.21 then 13.12 then 13.06
These are currently just siting on the basement floor, not connected to anything. What should if anything be a "normal" discharge rate just sitting?

[pianotuna]

Equalize the weak battery. Wire in a balanced manner when returning the jars to the RV.

[jkwilson]

tarnold wrote:
Op again. My question was what should you expect as "normal" or acceptable discharge of a 12 volt wet cell that is connected to nothing, just sitting on the floor. .10v per week, month?

Too many variables. Battery age and condition, plus temperature determine what you lose, but temperature variation causes swings in voltage too.

Generally, charging monthly should keep them very close to full charge, but whatever your batteries take is what they take.

[2oldman]

tarnold wrote:
AGMs will discharge 1 to 3% per month.

If even that. I've been pleasantly surprised with my Lifeline 12v AGMs holding a full charge for months.

[SidecarFlip]

YC 1 wrote:
3 yrs old.. Batt 1 is ready for replacement and I would never buy one. Replace them both.

We do NOT buy batteries. We only rent them. In the RV world most batteries are murdered and not allowed to live a normal life. they work very hard and are tortured to death.

You can mess about with all kinds of tests and maybe revive it but I personally do not like sick batteries when I am boondocking. Dead or sick batteries lead to all kinds of other things not working properly.

Always in pairs or in whatever quantity you run. Same with my truck. I replace both at the same time, always.

[tarnold]

Op, 2oldman, that was a good read, thank you. So the answer to my question per that read was lead acid will discharge " 1 to 15%" per month with a whole lot of "depends". AGMs will discharge 1 to 3% per month.
After that read, Wish I could get some GC batts in my confined space, just not enough head room.

[time2roll]

tarnold wrote:
Op again. My question was what should you expect as "normal" or acceptable discharge of a 12 volt wet cell that is connected to nothing, just sitting on the floor. .10v per week, month?

1/10th volt per month would be in the normal zone.
Exact chemistry and temperature would also affect discharge.

The real issue is that one is holding well and the other is not.

[BFL13]

tarnold wrote:
Op again. My question was what should you expect as "normal" or acceptable discharge of a 12 volt wet cell that is connected to nothing, just sitting on the floor. .10v per week, month?

Batt 2 is normal. It will get down to 12.75 after a few days then very slow decline after that. Batt 1 dropped too far too soon.

Your problem is to return that Batt 1 under warranty and then not have a new one to go with the older Batt 2 .

One solution is to get two new ones and keep that still good Batt 2 for some other job. Maybe give it its own 300w inverter and use that to watch TV so the other two don't get down so soon while camping. Whatever--lots of possibilities.

[2oldman]

tarnold wrote:
what should you expect as "normal" or acceptable discharge of a 12 volt wet cell that is connected to nothing, just sitting on the floor.

Google is amazing.

Battery voltages

[tarnold]

Op again. My question was what should you expect as "normal" or acceptable discharge of a 12 volt wet cell that is connected to nothing, just sitting on the floor. .10v per week, month?

[jkwilson]

Everstart batteries are made by Johnson Controls. Their full charge voltage is 12.65V. The higher voltages you are seeing are what is called surface charge, which is a remnant of the last charging voltage being applied by the charger. Surface charge dissipates at a much faster rate than actual battery discharge.

The battery above 13V is in good shape, though it says nothing about the actual capacity of the battery. The other one is probably toast, but it could be salvagable.

What does the electrolyte level look like in the cells of the suspect battery?

If electrolyte is okay, you may need to equalize. It would be good to check cell specific gravity with a hydrometer or a refractometer before and during equalization. Cells can become unbalanced and equalizing can help with that easily.

[time2roll]

Charge #1 24 hours and check again.

[wolfe10]

Can't tell if you actually equalized the battery. What was maximum VOLTAGE.

Old "stupid chargers" are great for equalizing, as voltage can easily go to over 15 VDC. Yes, at very low amp rates.

Assuming these are wet cell batteries, I would charge until 15-15.5 volts is reached, and then see how long they hold a charge.

Yes, there are some "desulfating" chargers, but let us know what an old stupid one does.

[MEXICOWANDERER]

tarnold wrote:
OP again, don't know which one was down stream, got shuffled.
Using a Schumacher shipnshore. Set to charge @15 amp, deep cycle. Each one charged for over 12 hrs. Charger shows charged to 100 %.
These are MAXX everstarts, 29DC.

I wish I had an Einstein SMART BANK ACCOUNT
Governor MOONBEAM specials in operation.

Here we go again with,

"I can't Charge The Batteries, the charger won't let me"

Grumble Grumble...

[YC_1]

3 yrs old.. Batt 1 is ready for replacement and I would never buy one. Replace them both.

We do NOT buy batteries. We only rent them. In the RV world most batteries are murdered and not allowed to live a normal life. they work very hard and are tortured to death.

You can mess about with all kinds of tests and maybe revive it but I personally do not like sick batteries when I am boondocking. Dead or sick batteries lead to all kinds of other things not working properly.