Winter battery storage on Axis

[happy]

On an Axis/Vegas, do I understand correctly?

Battery Switch in Off/Store position this disconnects the coach batteries from the house. And it disconnects the house batteries from the chassis battery.??

[DavidEM]

Originally Posted by happy

On an Axis/Vegas, do I understand correctly?

Battery Switch in Off/Store position this disconnects the coach batteries from the house. And it disconnects the house batteries from the chassis battery.??

It may be different on a newer Axis like my 2021, but on it, the only circuit that is disabled with the battery switch is the circuit to the converter. The circuit to the generator start, solar panels and to the BIM which can connect to the chassis battery are all still enabled.

So during winter storage, any solar power that may be hooked up will charge the coach batteries, and then if the chassis battery voltage drops below the trigger voltage of the BIM and the coach battery voltage is high enough, it will connect and keep the coach battery charged.

You might want to read up on how the BIM works, a copy of their data sheet is attached. Here is the pertinent text:

The BIM monitors the battery voltage of both the chassis and coach batteries over long
periods of time. If it senses a charging voltage, it connects the two batteries together. If the
charging system is drastically overburdened, the batteries will be isolated, however, if the
BIM sees a long term charging of both batteries it will allow the batteries to remain connected
and allow the charging system to do its job. Once the batteries have charged for one hour, the
BIM will isolate the batteries to prevent overcharging, and will only reconnect the batteries
for charging if one of the batteries drops to approximately 80% charge, and the other is being
charged. This long term monitoring of the batteries prevents the annoying relay clicking that
exists in simpler isolation modules today. The BIM does not guarantee 100% battery charge,
but prevents harmful battery charge levels.

Now the foregoing is all theory on my part. I haven't confirmed it in practice but I will this winter.

Hopefully others will chime in and confirm or correct my understanding.

David

[bevedfelker]

With USE/STORE switch in Store there is still some parasitic drain on the house batteries. Battery power still goes to the CO detector and also the radio station selects and clock in the radio. You'll find you have to charge the batteries periodically by running the generator or connecting to shore power about every two months. I don't know if you have solar or not -- but you will not be able to go all winter in storage and expect the house batteries won't drain down.

I just had knife switches put on my house battery bank and also on the chassis battery. When I put my 2015 Vegas 24.1 in storage I'll open both knife switches. This guarantees that there will be no parasitic drain on any of the batteries. I'll still check their status throughout the winter but doubt I'll have to run the generator every two months to keep the batteries charged.

[DavidEM]

On my new Axis those parasitic loads are 0.05 to 0.1 amps with the switch off. So at worst 2,4 Ahs a day. Yes after a few months my 200 Ah AGM battery bank would be down quite a bit if it weren't for the 100 watt solar panel. That keeps it nicely charged up.

And further to the OP's original question, if you don't have solar the coach batteries will slowly discharge and never trigger the BIM to connect it to the chassis batteries and they will discharge due to their parasitic loads.

Solar is your savior here, even 50 watts does the job. I use a portable 50 watt panel that it put on the south facing rear bumper to keep the batteries charged when we get a layer of snow on the roof top solar panel.

David

David

David

[happy]

Thanks for this great information.
I am reading and did down load Col. Felker's PDF.

Much or most of these systems are new to me and I appreciate the helpfulness found on the forum.

About the time I take possession of my Axis it will be beginning of winter.

[Chateau_Nomad]

I would suggest either of two scenarios:
1) Remove the battery(s) and connect them to a "smart" trickle charger, or
2) Start your solar installation with a 100 -150 watt panel on the roof. Then add to that as your budget allows.

Leaving lead acid batteries to sit idle without cycling/conditioning charging to discharge below 12volts is their death knell. Keep a charge going into them and they will serve you well.

[mcr1010]

Originally Posted by happy

Thanks for this great information.
I am reading and did down load Col. Felker's PDF.

Much or most of these systems are new to me and I appreciate the helpfulness found on the forum.

About the time I take possession of my Axis it will be beginning of winter.

Fall and winter are some of my favorite seasons to go camping. No crowds etc. Don't let a little cold weather stop you from using your new rig this fall and winter.

[happy]

Good idea Chateau Nomad.

Still learning so....

Will one trickle charger connected to the house batteries also charge the chassis battery? But if I do as bevedfelker and have a knife-disconnector switch and isolate each battery, then I would need two trickle charges.

Is this right?

mcr1010, I agree. We will go several somewheres after Christmas. Kids visits etc

[JamieGeek]

Originally Posted by Chateau_Nomad

I would suggest either of two scenarios:
1) Remove the battery(s) and connect them to a "smart" trickle charger, or
2) Start your solar installation with a 100 -150 watt panel on the roof. Then add to that as your budget allows.

Leaving lead acid batteries to sit idle without cycling/conditioning charging to discharge below 12volts is their death knell. Keep a charge going into them and they will serve you well.

Removing the chassis battery on an Axis/Vegas unit is a bear.

I've had my Axis for 7 years now and it has lived through that many winters: I put disconnects on both batteries and disconnect them whenever the coach is in storage. During the winter I start both the engine and the generator on a regular basis to keep the batteries charged (with them connected of course).

This will likely jinx me but: I still have the original chassis battery in the coach and it starts the V-10 right up every time.

[happy]

I understand about the chassis battery location......seems less than smart.
You have gotten good use from your battery.

Starting and a driving would be a good idea for batteries and engine.

I read that in gasoline engines internal rust begins after just a few days.Maybe newer engines take a little longer.

[Chateau_Nomad]

When I had a Grand Design trailer, I simply ran an exterior grade extension cord to the battery box and used a trickle charger. I did the same for the first winter (2019) with the MH. The spring of 2020 I installed the rooftop solar, replaced the house batteries and didn't look back. It's a non-issue now.

[happy]

Thank you all for the replies!

[10scDust]

When I get ours ready for winter storage, in its own carport area, I have shore power disconnected too.
I ran lengthened battery tender leads from chassis batteries to the under hood compartment near the engine's battery.
With leads from both sets of batteries, I run an extension with a multiplier on the end, hook up a battery tender to each lead, tuck it all under the hood, tuck the extension cord out of the hood's way and shut the hood.
No worries, I also have the stow switch turned off.

[bevedfelker]

When I look at the schematic with the batteries, BIRD, Trombetta and Isolation relays, I don't think putting a trickle charger on the house batteries will "bleed over" to also charge the chassis battery. I do not see how the isolation relays would function to allow charging current to go to either the house batteries or chassis battery. The isolation relays would be set to isolate the chassis battery from the house batteries while the house batteries are charging. When the house batteries are fully charged the isolation relays would have to function to then isolate the house batteries from the chassis battery in order for the chassis battery would then charge. I just do not see how that solution process would occur. The charging current is going to go to one set of batteries or the other -- it is not going to be simultaneously applied to both the house and chassis battery at the same time.

It strikes me that if using a trickle charger you'd need one for the house batteries and another for the chassis battery.

I could be wrong and I know there are many on this forum far more knowledgeable of Thor electric than I am. If I'm wrong about this, I hope they speak up and provide you the best information.

As Ive said on this forum probably a thousand times, "Owning a Thor RV is an adventure in self discovery."

[happy]

I love plumbing because it leaks or it doesn't.
Electric sits and waits to pounce on you when you turn your back.

This journey self discovery is fun.....but glad you all are willing tolled a hand.
I think I will try to isolate batteries and use 2 trickle chargers. Preferring to not run current through systems that may not be looked at for a few weeks on end.

[Chateau_Nomad]

Before going to solar, I used 2 maintainers... one for chassis battery; one for house battery. I'll have to do some investigating, but I believe the solar (on mine) keeps the chassis battery topped off/conditioned also. Anyone know for sure?

[DavidEM]

The Precision Circuits BIM says it connects the batteries to charge the low one, whether it is the chassis or coach. But lots of criteria such as the high one being "charged". That could be any voltage above 12.7. See attachment below for more details.

David

[sip]

After several extremely unpleasant chasis battery deaths on the 2016 Vegas, I finally put a physical disconnect switch at the battery. Now, everytime we are done with a trip, I completely disconnect the chasis battery from everything.

My RV is always plugged in for trickle charging the house batteries but if I were to ever leave it for an extended period, I'd pull the cables off the batteries under the stairs as there are several wires going to it and I don't think they are all behind the use/store switch.

Unlike the chasis battery, at least there is fairly easy access to the terminals on the house batteries. As already mentioned, the chasis battery is a PAIN in the rear to get to (have to go through the passenger dash area).

[DavidEM]

Originally Posted by DavidEM

The Precision Circuits BIM says it connects the batteries to charge the low one, whether it is the chassis or coach. But lots of criteria such as the high one being "charged". That could be any voltage above 12.7. See attachment below for more details.

David

I was down at my new Axis the other day and did this experiment:

With the chassis batteries showing 12.6 volts, I started the generator. A few minutes later I checked and the converter was charging at a few amps and the coach batteries were at 13.5 V and so was the chassis battery.

Obviously the BIM had connected the two since the coach was charging, ie its voltage was above 13 V.

So this winter my solar panel should keep both house and chassis batteries charged up even though it is only connected to the coach batteries.

David

[Pete'sMH]

Originally Posted by DavidEM

I was down at my new Axis the other day and did this experiment:



With the chassis batteries showing 12.6 volts, I started the generator. A few minutes later I checked and the converter was charging at a few amps and the coach batteries were at 13.5 V and so was the chassis battery.



Obviously the BIM had connected the two since the coach was charging, ie its voltage was above 13 V.



So this winter my solar panel should keep both house and chassis batteries charged up even though it is only connected to the coach batteries.



David

I suggest a small solar system. I have one small (80W) panel that keeps my chassis and house batteries fully charged during storage. My Renogy system with a high efficiency charge/controller was barely $150 and was a fun and simple DIY project. It is entirely automatic in its operation and maintenance free. One of the best mods I’ve done. I bought two panels because I thought I’d need them but one is entirely sufficient and the other is just taking up space in my garage.