Best Battery Life Question

JanFMiller · 10-31-2020, 10:04 AM

1st 'real' RV for me.

Battery is charged by on-board converter.

It's my understanding, perhaps incorrect?, that deep-discharge batteries last longer if they have a discharge/charge cycle.

I almost never use the RV on battery alone, it lives connected to 'shore power'.

So:

1. should that be done.

2. If so, what would be the best way to do that? I assume just disconnecting the battery with it's cut-off switch would not be, no load.

thanks in advance...

NavyLCDR · 10-31-2020, 10:12 AM

Lead acid battery life is based on the number of charge/discharge cycles and the depth of the discharge of the battery. Basically, the more you discharge the battery, the shorter it's life. So, a battery kept fully charged and never discharged, should last many, many, many times longer than a battery that is discharged and charged over and over.

Also, a battery that is discharged to only 75% then charged will last longer than a battery that is discharged to 50% then charged. Discharge the battery less than 50% and you are greatly shortening it's life.

Now this should not be confused with discharge capacity. A deep cycle lead acid battery takes multiple discharge/charge cycles to reach it's full amp-hour discharge capacity. Then it will hang out near it's full amp-hour capacity for the bulk of it's lifetime before it's amp-hour capacity starts dropping due to number of cycles.

This PDF might help. Look at the expected life v. Depth of Discharge (DOD) graph:
https://www.usbattery.com/wp-content...heet_319-1.pdf

Finally, you need a charge controller that has a trickle charge mode. Once the battery is fully charged, you don't want to keep overcharging it because this will cause excessive gassing, boiling the electrolyte, and other damage to the battery. You want to go into trickle charge once the battery is fully charged which is just enough to make up for internal charge losses in the battery. A controlled pulse in the trickle charging of the battery will help keep the electrolyte mixed, though. My Progressive Dynamics charger does this pulse for 15 minutes every 20 hours just to keep the internals of the battery "fresh".

JanFMiller · 10-31-2020, 10:28 AM

Good info, thanks, I'll read the pdf.

I've used Battery Tenders for years on my motorcycles with great results.
I'm not sure what the capabilities of the converter in my trailer are; I expect 'not much'... I'll sleuth that out...

But that brings up another question: What's the best way to bypass the converter charging the battery is you want to use a different charge scheme??

NavyLCDR · 10-31-2020, 10:37 AM

Quote:

Originally Posted by JanFMiller

Good info, thanks, I'll read the pdf.

I've used Battery Tenders for years on my motorcycles with great results.
I'm not sure what the capabilities of the converter in my trailer are; I expect 'not much'... I'll sleuth that out...

But that brings up another question: What's the best way to bypass the converter charging the battery is you want to use a different charge scheme??

A battery disconnect switch. Turn the battery disconnect switch off and connect the external battery charger to the battery.

TitanMike · 10-31-2020, 10:41 AM

Quote:

Originally Posted by JanFMiller

Good info, thanks, I'll read the pdf.

I've used Battery Tenders for years on my motorcycles with great results.
I'm not sure what the capabilities of the converter in my trailer are; I expect 'not much'... I'll sleuth that out...

But that brings up another question: What's the best way to bypass the converter charging the battery is you want to use a different charge scheme??

If you purchased your trailer the last 10 years or so there is a high likelihood your converter is a multi-stage unit. Will charge at Bulk rate (usually over 14 volts) until the battery voltage reaches approximately 13.8 volts. It will then continue at the Absorption rate (13.6-13.8) until the battery is fully charged and the voltage drops to approximately 13.5 volts where it will remain at this Float voltage until you turn the converter off.

Float voltage is just enough to keep current flowing into the battery to offset any internal discharge or any items like Stereo memory and LPG/CO sensor draw (which is very little) without causing the battery to "gas".

Newer converters are far better than those of old that had merely one output voltage. I had a trailer built in the 90's that had a Magnatek. It had only two voltages. 13.25 volts all the time which could be "goosed" to 13.6 if you added a jumper for when using a generator so it would charge batteries quicker.

Since you didn't lost the year, make, and model. but you are on the Forest River Forum I'm going to guess that you have a Converter made WFCO which is a 3-Stage Converter. Perhaps not the best but more than adequate for most.

If your trailer lives connected to shore power I wouldn't worry about the converter, just regularly check water levels in the battery regularly.

geoff270ssf · 10-31-2020, 01:29 PM

Quote:

Originally Posted by NavyLCDR

Lead acid battery life is based on the number of charge/discharge cycles and the depth of the discharge of the battery. Basically, the more you discharge the battery, the shorter it's life. So, a battery kept fully charged and never discharged, should last many, many, many times longer than a battery that is discharged and charged over and over.

Also, a battery that is discharged to only 75% then charged will last longer than a battery that is discharged to 50% then charged. Discharge the battery less than 50% and you are greatly shortening it's life.

Now this should not be confused with discharge capacity. A deep cycle lead acid battery takes multiple discharge/charge cycles to reach it's full amp-hour discharge capacity. Then it will hang out near it's full amp-hour capacity for the bulk of it's lifetime before it's amp-hour capacity starts dropping due to number of cycles.

This PDF might help. Look at the expected life v. Depth of Discharge (DOD) graph:
https://www.usbattery.com/wp-content...heet_319-1.pdf

Finally, you need a charge controller that has a trickle charge mode. Once the battery is fully charged, you don't want to keep overcharging it because this will cause excessive gassing, boiling the electrolyte, and other damage to the battery. You want to go into trickle charge once the battery is fully charged which is just enough to make up for internal charge losses in the battery. A controlled pulse in the trickle charging of the battery will help keep the electrolyte mixed, though. My Progressive Dynamics charger does this pulse for 15 minutes every 20 hours just to keep the internals of the battery "fresh".

Right! Our Georgetown 270SSF has a Progressive Dynamics controller/charger with a function they call "Equalization" that (as you describe) raises the charge voltage to 14.4V for 15 minutes every 21 hours during Storage mode.

There is no shore power at our storage location. So I plan to remove the batteries and store them at home on some kind of battery tender. Progressive Dynamics does not make a charger only: their rep told me "that market is too crowded for us to stand out." But reading their tech info the argument for periodic "Equalization" is compelling, and I have not found a battery tender that clearly claims to do this. Some of them seem to do something similar once during initialization, but none claim to perform it periodically during Storage mode. Please correct me by suggesting one that I missed!

Thanks all!

camaraderie · 10-31-2020, 01:54 PM

Quote:

Originally Posted by geoff270ssf

For this I want a charger with the periodic "Equalization" function.

FWIW...I see NO need to remove the batts OR put them on a charger in your case. You should simply fully charge them before you put your GTown away for the winter. You then disconnect the negative battery wire and let them sit.
The COLDER the weather the better for LOW self discharge...you will only discharge a few amps a MONTH if your weather regularly gets below freezing and up to 10% a month if winter stored in Florida.
The solution IF your batteries ever get to 60% charged...12.3Volts... then you can run your genny to bring them back up while putting on a FULL 14.4V bulk charge to really mix up your H2SO4 acid. Chances are you'll never see 60% in colder climates.
Since you also are NEVER not plugged in when you are using your RV...you are served perfectly well by the cheapest 12V dual purpose batts around. There is no need to invest in quality deep cycles as there is for boondockers. No cycles = Little Battery Wear & long life on a 4 stage charger like the Progressive. (Bulk/Absorbtion/Float/EQ)

TxRockwood · 10-31-2020, 04:08 PM

This is a great topic! I was considering adding a second battery to my Rockwood 2511S. If I always plan to use my camper on shore power, is there any reason to add a second battery?

Mine has the Interstate HD24-DP, which I think is a fairly cheap battery.

JanFMiller · 10-31-2020, 05:40 PM

Thanks for all the great info.
Found the manual on-line for my converter, and it is indeed 3-stage.
On to the next big thing...
Thanks again!

camaraderie · 10-31-2020, 06:55 PM

Quote:

Originally Posted by TxRockwood

This is a great topic! I was considering adding a second battery to my Rockwood 2511S. If I always plan to use my camper on shore power, is there any reason to add a second battery?

Mine has the Interstate HD24-DP, which I think is a fairly cheap battery.

You have a group 24 dual purpose battery. It's all you need if you always plug in. It has 75 amp hours...half usable. I always like 2 batteries for redundancy...but not really needed.

**bikendan** · 10-31-2020, 07:37 PM

Quote:

Originally Posted by TxRockwood

This is a great topic! I was considering adding a second battery to my Rockwood 2511S. If I always plan to use my camper on shore power, is there any reason to add a second battery?

Mine has the Interstate HD24-DP, which I think is a fairly cheap battery.

If you never dry camp or boondock, a cheap Group 24 dual purpose marine battery is fine.

ACE110 · 10-31-2020, 07:40 PM

Quote:

Originally Posted by camaraderie

You have a group 24 dual purpose battery. It's all you need if you always plug in. It has 75 amp hours...half usable. I always like 2 batteries for redundancy...but not really needed.

X2

BDenn · 10-31-2020, 08:46 PM

This is my 3rd winter for my class C. The first year I disconnected all my terminals to my batteries. The next year disconnected my house battery terminals, on my chassis battery only disconnected only my negative. When returned in the spring my chassis battery positive terminal was all corroded white down the side and green on terminal. Cleaned it up and used it all summer no corrosion this year. Had trouble with charging system this summer so changed to 2 new batteries for the house. My chassis battery is still good I hope. Might be a bad battery. Will always take off both terminals now.

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