Battery disconnect

Hi Jim,

Read up on the Peukert law. It may be that even with mismatched batteries more energy can be extracted from using both at once. Charging to 85% of full could be done together until one battery reaches that number--then separate them for a full charge.

JimBollman wrote:
I added a shut off switch to mine and decided to add one that supported two batteries and added a second battery in a battery box in the wheel well. Since I don't have matched batteries I use one battery till it starts to get low and then switch to the other. I never run them in parallel but could if I ever replace both batteries at the same time. I would still probably use them one at a time since I know how much reserve I have left when I switch batteries.

I added a shut off switch to mine and decided to add one that supported two batteries and added a second battery in a battery box in the wheel well. Since I don't have matched batteries I use one battery till it starts to get low and then switch to the other. I never run them in parallel but could if I ever replace both batteries at the same time. I would still probably use them one at a time since I know how much reserve I have left when I switch batteries.

HMS Beagle wrote:
The battery disconnect in my Bigfoot will turn off everything, including the smoke detector and CO detector. The object of this device is to prevent idle time battery drain when the camper is not being used. Having those parasitic draws bypass the disconnect makes it useless. In m opinion the disconnect should be between the battery and everything else.

This is system I had installed in our Outfitter 4 years after we bought the camper. When I snap off the battery disconnect, all parasitic draws are halted...but I also can run the AC system separately not feeding the built-in camper converter/charger (I have two AC systems; see below)

Also, I can "plug" my marine battery charger (AGM charge profile) into an isolated AC source, completely bypassing our camper's built-in converter/charger (yes, I have 2 charge systems in the camper) and completely bypassing the camper's AC system (my second charge source is GFCI in the camper parking area at home). Concluding, I have 2 isolated systems: an isolated camper AC system fed via the camper's AC input (this can supply 12V to our camper 12V DC appliances), and a completely separate 12V battery system that can be isolated from the camper's built-in converter/charger (for various reasons). I now also have redundant CO and propane detectors that are not parasitic to the separate 12V DC battery chain (these are lithium battery powered).

HMS Beagle wrote:
The battery disconnect in my Bigfoot will turn off everything, including the smoke detector and CO detector. The object of this device is to prevent idle time battery drain when the camper is not being used. Having those parasitic draws bypass the disconnect makes it useless. In m opinion the disconnect should be between the battery and everything else.

I've got the "Store/Use" switch just inside the door of the Bigfoot. My smoke detector has it's own 9volt battery. I occasionally think I will put a disconnect switch on the batteries themselves.

Ours has one near the door as you enter. Makes it nice to shut down the small discharges if we aren't going to use the camper. Now with solar it's not a big deal but typically if it's going to be more than a day or two I will shut down solar panel production and turn off the battery bank. No need to have active circuits when they aren't being used.

In our new camper I am installing one of these at the battery box



It's handy to be able to shut down the battery at the source and de-energize everything past the switch to work on either the batteries or the camper.

hedgehopper wrote:
Our camper does not have a battery disconnect. And I have never had occasion to want one. When do you use yours? (And don't say "When you want to disconnect the battery.")

I don't mean to be cute, but the only time I use my battery disconnect is when I want to disconnect my battery. My Charger/converter works with or without my battery. With no battery but still plugged into shore power, I can still use my RV. If I want to remove my battery I can and the positive cable is disconnected and not just laying loose while hot. I have used my battery to jump start some of my other equipment, and on a couple of occasions used it in my tractor. I have also used it for the brake battery on my flatbed trailer.

EDIT: I think not having a Battery Disconnect Switch in a RV is like not having Main Circuit Breaker in your house. It is true that you can just remove the battery cable, but it is also true you can just pull the house circuit breaker.

Hmm, my battery disconnect really turns EVERYTHING OFF. Nothing runs.

The battery disconnect in my Bigfoot will turn off everything, including the smoke detector and CO detector. The object of this device is to prevent idle time battery drain when the camper is not being used. Having those parasitic draws bypass the disconnect makes it useless. In m opinion the disconnect should be between the battery and everything else.

Start with checking what voltage your charger supplies.
Lot of converters have the voltage >14V and you don't want that for long time.
Same applies to solar chargers.
I always disconnect my batteries when in storage after giving them good charge at the end of the season.

It's a confusing switch for some. It's labeled "BATTERY DISCONNECT". On or off. Maybe I've had too many English classes but battery disconnect ON could mean the battery is disconnected, and vice versa for OFF.
But no, ON means the battery is connected. Usually the switch needs to be on to charge the battery from a 110volt connection or when connected to a tow vehicle. And, OFF isn't really completely OFF. The smoke detector, CO detector, radio lights, etc. will still be on.