Battery Disconnect?

[ronmc]

On reading info. on battery disconnect, it says to disconnect battery if it will be on converter power for extended time.Anyone do this? Mine stays on shore power/ converter power for months. Am I ruining my batteries?

[ronmc]

I found this on a battery info. site:

Image result for 12v battery float voltage
Some lead acid batteries are used in a standby condition in which they are rarely cycled, but kept constantly on charge. These batteries can be very long lived if they are charged at a float voltage of 2.25 to 2.3 volts/cell (at 25 degrees C) (13.5V to 13.8V for a 12V battery).

[Reflex439]

Byrogie wrote:
If you use the disconnect, then you would unplug from shore power.....

...except if you have a modern converter, in which case it usually doesn't matter.

Yea, it would be nice of the coach or converter manuals to mention that. There are many valid reasons one might want to use the 120V/12V power without a battery hooked up.

[Byrogie]

If you use the disconnect, then you would unplug from shore power.....

[Reflex439]

I have read many times in various forums (here and elsewhere) of advice to use the battery disconnect to take the battery offline so it will not be overcharged when plugged into shore power for any long period of time. In the case of the Magnetek I have, thats bad advice. On newer converters with modern 3 or 4 stage chargers, its unnecessary.

The manual for my Roadtrek talks about how the converter and battery disconnect switch inter-operate, as well as the isolator and charging. It also states to use the Battery Disconnect switch when not using the RV to prevent discharge of the house battery by drain from CO, LP, smoke detectors, etc. It doesn’t state any length of time which could lead some users to disconnect anytime they are leave the RV for the day since they are ‘not using it’ during that time 😉 I can see how this could be confusing for RVers that don’t understand how the electrical system works. It also doesn’t mention you should NOT do this if you are plugged into shore power!!

What I noticed on my RV with a Magnetek 6300 series completely by accident, is that if you use the battery disconnect switch while on shore power two things bad happen.

1. The light showing the battery is connected, stays illuminated. I assume thats because it simply checks for power, regardless of where it comes from. So you receive an indication that the battery is connected when its not, assuming everything is fine.
2. At the same time, the converter voltage jumps to 16.5V causing appliances to start behaving erratically. I.e, my TV and stereo go into a constant power cycling loop. Others just exhibit odd behavior.

[dougrainer]

I would like to know WHERE he found that info. Also, what does a manual/instructions for a Battery disconnect have anything to do with the Converter/Battery system operation system??????? What if you do NOT have a Battery disconnect????? Millions of RV's have NO battery disconnect, what happens to them?????? The plain fact is, having a LOAD (battery) will make a Power Converter operate more efficiently. Remember, Inverter/Chargers CANNOT be disconnected from the Batteries. They are hardwired directly to the Battery system. Of course Inverter/Chargers are smarter chargers. Without the OP posting Year/Brand/Model of RV and the Brand Model of his power converter, we cannot help him. He may have a defective Power Converter, if it stays at 13.6 volts and never goes to float. Also, is his voltage AT the battery and with a stand alone Digital multimeter. Or is he using some type of built in voltage read out system. Doug

[time2roll]

ronmc wrote:
The converter supplies 13.6 volts continuously
I used to add water each month,I added mineral oil. Now much less.

13.6 volts will not kill them. Maybe disconnect when it get to roasting 90+ for weeks on end. Winter leave it connected.

[Almot]

brulaz wrote:
Just read recently here that the converter works best with batteries connected.
The batteries sort of provide a voltage buffer, or something like that.

Yes...

Now we need to figure out what was meant in the post #1:
"...to disconnect battery if it will be on converter power for extended time":
1) Disconnect battery from loads if battery will be on converter,
2) Disconnect battery from everything, i.e. converter and loads,

or?

[brulaz]

Just read recently here that the converter works best with batteries connected.
The batteries sort of provide a voltage buffer, or something like that.

But if the converter over charges the batteries that's not good for the reasons discussed above.

So I guess only leave the batteries connected if you have a "good" converter that goes into float mode, like 13.2V or similar.

[Almot]

ronmc wrote:
On reading info. on battery disconnect, it says to disconnect battery if it will be on converter power for extended time.

Without loads even the poorest converter will eventually charge it fully, and then it could evaporate excessively. So it's better to disconnect then.

Converter has to be temperature compensated. Not all of them are. Float voltage should be lowered by 0.03V per every 1F above 77F, and increased by the same amount if below 77F.

If you disconnect for more than 3 months at 77F, it will self-discharge below 50%, you don't want this either. In hot weather they will self-discharge much faster. If some loads are still On - LP/CO sensors etc, it will discharge faster yet.

[ronmc]

Thanks for all replies. I will try disconnect.

[korbe]

My Trojan batteries do not float a charge very well with my 3-stage converter. And since my converter doesn't seem to have any problems powering all my 12-volt items, I will disconnect my batteries when plugged in for a week or so longer.

[pianotuna]

Hi Roy,

Mineral oil has been used in large batteries for many year. However it only slows the evaporation process--not the losses from gassing. If you do not check the levels and the oil coats the plates--then that part of the plate will be compromised more or less permanently.

[gbopp]

RoyB wrote:

Never heard of putting mineral oil in a battery... Must be an old timers trick... MEX probably will have a good response to that haha...

Roy Ken

The idea has been discussed before:

Open Roads Forum

Mineral oil in batteries

Thermoil


I've never tried it.

[RJsfishin]

A film of oil on top of boiling water, will always cut down on water consumption.