Auxiliary Battery Discharge Question

[steelhead]

Have a few battery related questions for the collective experience on the forum. Apologies if this has been covered in other posts but I did search before posting this but did not hit on any relevant threads.

Background: for a variety of reasons that are not important here, we took our Fleet that was delivered in May off the truck for the past month. It was stored outside. Temperatures were generally in the 50-60’s during the day and the 40’s at night. The Fleet has the standard FWC auxiliary battery system – 2 Exide AGM batteries. A Trimetric 2025RV battery monitor has been installed for measuring electrical usage and remaining capacity.

After getting the camper back on the truck, the remaining battery capacity was displayed on the monitor at 62%. While I think the monitor uses a very small amount of electricity, I can’t figure out what is causing the batteries to drain. From some of the other threads, it seems that perhaps AGM batteries are continually discharging whether they are actually in use or not. Is that true? And if so, how does everyone store their batteries when your campers are not on the trucks? I guess the real question is: do I need to figure out a way to charge the batteries while the camper is removed?

Thanks in advance for any opinions and guidance.

 

[NorCalSteve]

Did you hit the master switch in the camper while it was not being used? In my hawk, my gas/ carbon monoxide detector uses power unless I hit the master power switch. I can't answer the question about AGM batteries draining some even when not being used.

Steve

 

[steelhead]

Thanks Steve. Good question which I should have covered in my post. We did make absolutely sure that the master power was turned off while the camper was off the truck.

 

[dsrtrat]

Is the monitor wired so that the master switch turns it off? If not this is most likely where your drain is. Even small loads will drain the batteries when on 24/7. Do some math with the load and you will see how it adds up over time.

If you are going to store the camper off for any length of time you will need to top off the batteries from time to time, they should be maintained at around 12 volts minimum for best life.

Batteries do self discharge over time for many reasons too complicated to get into on this forum.

Dsrtrat

 

[steelhead]

Thanks for the reply Dsrtrat. Yes, the monitor is wired so that it is on even when the master switch is off. I did do some math on the consumption and the discharge seems larger than the monitor usage which is what prompted my post. You did answer the big question though so I need to figure out a way to charge the batteries when the camper is off the truck for awhile. Thanks again.

 

[ntsqd]

I would look at solar for charging while on or off the camper. Build a robust system and you won't have to remember to do anything. This is the direction that I am going. Have the panels and the controller, still noodling on how I want to mount the 100W panel(s) to the roof.

 

[photohc]

I too remove my camper after a trip and have the same electrical setup except I have a solar panel also. Because the camper is stored in the garage, I plug into shore power during the non use. The IOTA 12v Power Converter/Battery Charge should maintain your battery. The FWC version of the IOTA did not have the smart controller module which you can order here.

 

[Hittheroad]

My experience with AGM in a fwc is that you need to top up the batteries every month or two if the camper is in storage. I have no idea why - it is easier just to do it. I use the AC hook up or drag the camper out into the sun where the solar cells can work.

 

[steelhead]

Thanks for the replies everyone. I have been thinking about solar all summer and that looks like the answer as there is no shore power available where we store it and I really do not want to invest in a generator. Thanks also photohc for the link to the IOTA control module. After reading about that component earlier today it sure looks like a worthwhile addition to the system.

 

[Casa Escarlata Robles Too]

Since my truck/camper is outside all the time my solar keeps both the truck and camper battery up to charge.During the winter/rainy season here on the coast I keep the truck and camper tarped.I have a hole cut into the camper tarp to keep the solar panel open to the sun.


"Thanks for the replies everyone. I have been thinking about solar all summer and that looks like the answer as there is no shore power available where we store it and I really do not want to invest in a generator. Thanks also photohc for the link to the IOTA control module. After reading about that component earlier today it sure looks like a worthwhile addition to the system"


Works great for me.
Frank

 

[trailrider]

I have a small amount of battery drain in my ATC camper. I think it may be my compressor refrig. Even when the thermostat is in the off position, it may still be powered. I only have interior-exterior lights which are off and a smoke detector which is self powered. I have a main fuse for my camper battery. With everything off, I still get a little spark when I insert it (meaning there is some draw somewhere). I am currently using the fuse as a main disconnect.

 

[Casa Escarlata Robles Too]

I have a small amount of battery drain in my ATC camper. I think it may be my compressor refrig. Even when the thermostat is in the off position, it may still be powered. I only have interior-exterior lights which are off and a smoke detector which is self powered. I have a main fuse for my camper battery. With everything off, I still get a little spark when I insert it (meaning there is some draw somewhere). I am currently using the fuse as a main disconnect.

Do you have a main shut off switch?It should be with the fuse block.
My Bobcat does and when it is pushed off nothing is powered in the camper.
Frank

 

[Accrete]

Greetings Steelhead,
I have a similar setup in our rig in that we have 2 Optima AGM batteries and i have calculated/observed about a 10% drain on my system per month. This is a bit more than the Optima site states but i must also account for the ~.06ah draw from the built in Xantrex monitor. I'm fine with that taking place as i leave the rig plugged in to AC and have the Optima 1200 digital charger to maintain the batteries. I also know from utilizing AGM batteries of various brands over the last ~15 years in my HAM Radio setup that they must be maintained to be happy : )

I think the solar would be a viable option if you cannot keep the AGMs maintained with the AC charger. As stated above, it is important to keep the batteries maintained above 50% capacity. If the bank drops below this level it is possible to create a situation whereby inappropriately charging the battery can cause overheating and even a dangerous situation. I know of at least two AGM users that "winterized" their rig only to nearly blow up the batteries upon beginning the charge for the first time several months later in spring.

Happy & Safe travels.
Thom

 

[Kodachrome]

I really do not want to invest in a generator.

Yeah, and we really need less people using things like generators for anything but essential needs at this point in time so thanks for not going that route.

I run a pretty robust and somewhat complex solar system in my ATC. Even though I have all LED lighting I do run a 12/110V fridge freezer and sometimes need to stay parked in one spot for a couple weeks without needing to turn over the engine. I also use my setup for work purposes mostly so it all has to be good to go 100% of the time. I do not run the camper off my truck battery at all, it charges the camper batteries only when in motion.

I run a Group 31M Die Hard as my main and a Optima Bluetop AGM as my backup. The two are separate and have their own charging system plus can share a spare 100 watt slide out / removable panel that lives under the cabover, the latter makes a huge efficiency difference when used on the 12 foot extension cord angled at the low sun in the Winter. The main battery is fed by either the truck, a 135 watt panel on the roof and 235W total with the slide out. The aux battery is fed by the truck if I select it and a 40 watt flex panel on the air dam in front of the camper. I can swap the 40 and the 100 if I need to favor a quicker charge on either battery. This system is pretty complex but gives me a ton of options and some backup if a charge controller goes out or something else and always keeps juice flowing to the batteries. It is also better for the environment as I should *never* have to turn over the engine to get power and it saves on gas, like I said this rig can and does stay parked as a base camp for weeks at a time.

Anyway, solar is now pretty flexible and cheap, there is no reason to be barfing exhaust in the air just for the recreation purposes of powering campers, it's 2013, it's high time we are done being that blatantly irresponsible….but you all know this, its common sense..

Go solar, end of story…

 

[trailrider]

Do you have a main shut off switch?It should be with the fuse block.
My Bobcat does and when it is pushed off nothing is powered in the camper.
Frank

My ATC is a shell version. I have no fuse block. I only have an inline fuse in the main power supply wire connected to the battery which I supplied.

 

[Casa Escarlata Robles Too]

My ATC is a shell version. I have no fuse block. I only have an inline fuse in the main power supply wire connected to the battery which I supplied.

Sounds like you need to install a shut off switch between the battery and the inline fuse of the main power supply.
Frank