Community Forums

Sandy Swede · 03-17-2017, 08:15 AM

I have a chart which one or more kind posters on iRV2 made available which show that a voltage reading on your battery of 12 indicates that your battery is 45 - 50% charged. If it reads 11.75 volts, you are only 30% charged, an so on. Assuming my coach is not plugged in to shore power and I check the battery bank reading, at what level should I be concerned that the batteries have been permanently degraded to the point that I need to pull them to do load and/or specific gravity tests? Although I normally leave the coach plugged in to shore power, I do unplug from time to time to "rest" the batteries.

All of the above relates to a winter storage mode.

Dr4Film · 03-17-2017, 08:26 AM

By discharging deep cycle batteries to more then 50% it does not ruin the battery. It simply reduces the number of use/charge cycles significantly.

How you decide to use your batteries is up to you. Discharge them more the 50% often and you will end up purchasing batteries more often then charging them back to Float when they reach 50% SOC or approximately 12.1 VDC

Dr4Film ----- Richard

Sandy Swede · 03-17-2017, 10:03 AM

Thanks Richard.

I am going to unplug from shore power for a few days, placing the system in "Store" mode. I then plan to check the voltage daily to get an idea of the pace at which the voltage drops off. I had thought that the solar strip, small that it is, would keep the bank float charging up to the 13.6v level that shore power maintains. I know that temps and cloud cover will enter in as variables, but past voltage checks indicated a drop off (if I recall correctly).

Gary RVRoamer · 03-17-2017, 01:05 PM

As Richard says, there is nothing magic about the 50% level - it's just a convenient point to remind us that the more a battery is discharged, the less it is able to repeat discharge/recharge cycles. Discharging only to 60% does less damage than does 50%, and discharge to 40% does more. Also, these values apply to lead acid batteries, primarily flooded cells. Further, the voltages cited apply to a battery at rest, with zero amp load. If there is even a tiny load on the batteries, the voltage will be lower at any given percentage level.

twinboat · 03-17-2017, 01:42 PM

You can get about 1000 cycles out of a well maintained deep cycle battery, if you discharge it to 50% and recharge it.

You get 500 cycles from a well maintained deep cycle battery, if you discharge it to 30% and recharge it.

30% more capacity each cycle, at the cost of 50% less cycles.

If, what you want to do by " resting it ", is let it slowly drain and leave it in a partially discharged state, you will shorten it's life considerably.

If you want to store a battery, charge it to 100% and disconnect all loads from it. It will be OK for a few months, otherwise let it float.

Sandy Swede · 03-17-2017, 02:58 PM

Quote:

Originally Posted by twinboat

You can get about 1000 cycles out of a well maintained deep cycle battery, if you discharge it to 50% and recharge it.

You get 500 cycles from a well maintained deep cycle battery, if you discharge it to 30% and recharge it.

30% more capacity each cycle, at the cost of 50% less cycles.

If, what you want to do by " resting it ", is let it slowly drain and leave it in a partially discharged state, you will shorten it's life considerably.

If you want to store a battery, charge it to 100% and disconnect all loads from it. It will be OK for a few months, otherwise let it float.

What loads would still be drawing after I switch to "Store" mode? Are you saying that one must physically disconnect from the battery terminals as there will still be draws, parasitic or otherwise, after you switch to "Store" mode?

twinboat · 03-17-2017, 03:16 PM

In many cases, the builders, leave some things connected before the disconnect. CO detectors, smoke detectors and possabily other devices.

I can't speak for your rig, it may make a clean break. A voltage reading between the neg. post and the neg. terminal, with it off the battery, will tell you. Any voltage reading means something is on.

parkerbill · 03-17-2017, 04:37 PM

On our last two TTs I installed a battery disconnect switch to prevent all those parasitic loads from draining our two batteries, but you have to make sure the batteries are turned on before towing so the emergency trailer disconnect switch will work. Our trailer has an electric tongue jack so I have to turn the added disconnect switch on to power it, thus reminding me to leave it on. LOL

Sandy Swede · 03-18-2017, 05:59 PM

Quote:

Originally Posted by twinboat

In many cases, the builders, leave some things connected before the disconnect. CO detectors, smoke detectors and possabily other devices.

I can't speak for your rig, it may make a clean break. A voltage reading between the neg. post and the neg. terminal, with it off the battery, will tell you. Any voltage reading means something is on.

Thanks twinboat. I will try that - should tell the tale.

And thanks to all others who responded.