Storage between trips--do you leave on shore power?

[JonMN]

Originally Posted by ks@yvr

I see you have a Ford Transit based van. The Ford transit van has a bit of parasitic draw on the automotive battery and if not run every 4-6 weeks, disconnected or put on a trickle charger it will run down the automotive battery over an extended period of time. The cellular link with Ford for remote start, location etc. is one draw, there is some solenoids that seem to cycle is another draw, plus who knows what else. I found my Transit has a draw, although it has not run the battery flat has lost charge in the winter to where the truck starts but you can tell the battery is not fully charged.

On the Transit forums there are several threads on dead automotive starter batteries from vehicles sitting over 4-6 weeks. I hard wired a small trickle charger to my automotive battery and keep that plugged in if I am leaving the van for an extended period of time. This has worked for me. At least this way my automotive battery is always ready to go when I am.

My lithium house batteries I just turn off the main disconnect but my battery bank is big enough that it just doesn’t seem to have any noticeable battery loss between van runs whether on or off. My lithium batteries have a temperature sensitive BMS and will not accept charge if the batteries are too cold.

Thanks! Funny, one of the first things I did was add a chassis battery maintainer.
This was before I figured out that shore power also kept the chassis charged. Given the unconventional location of the chassis battery (under the drivers seat) I want to put off problems as long as possible.

Interesting question--I wonder if I the battery maintainer on just the chassis would screw up anything with the coach battery? Our van uses the BIM-160 to maintain the batteries.

Still thinking of changing the 330AH AGM for a 300AH lithium with exactly the same physical dimensions. Changing the BIM-160 to a DC-DC charger too.

[ks@yvr]

Don’t think it should screw anything up. Once the battery is charged by either charger they both should shut down. I think that your trickle charge rate might be a little higher with 2 chargers charging at the same time but once the battery is charged both would shut down. If your house charger looks after the vehicle battery anyway I’d probably remove the battery maintainer since it is most likely redundant.

[@Michael]

Originally Posted by JonMN

Interesting question--I wonder if I the battery maintainer on just the chassis would screw up anything with the coach battery? Our van uses the BIM-160 to maintain the batteries.

It won't hurt.

From my BIM-160 manual:

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.

Originally Posted by JonMN

Still thinking of changing the 330AH AGM for a 300AH lithium with exactly the same physical dimensions.

Keeping it warm in winter and keeping it from getting beat up by road debris in summer will be challenging. Lead-acid batteries seem to be made of much tougher materials than lithium batteries.

Originally Posted by JonMN

Changing the BIM-160 to a DC-DC charger too.

I did this with my 2019 Crossfit/Beyond. To charge the coach battery from the alternator I now have a 40A Redarc and 18A Victron in parallel. I ran a new 4ga. wire from the drivers seat pedestal back to the chargers and upgraded to a 60A breaker. The OEM breaker and wire were 8ga./40A.

[JonMN]

^^^ Thanks Michael--I really appreciate the comments. Just looking at the under-chassis tray it looks like it would be really easy to add isolation to keep it clean of spray. I realize it might be warmer than desired, but not in the range of damage.

For our REALLY cold weather, I could just take the risk, keep it plugged in (heated lithium) or wrap it in something like this (LINK) for storage. I'm liking this linked heater at the moment.

The actually battery I am looking at is the Ionic Model IC-12V300-EP4S. Size is perfect, the battery has internal heating, bluetooth BMS, and has one of the best enclosure ratings I have seen, at IP56--resists heavy water spray. I have even thought of a rubber wrap if I want more isolation. 300AH

Right now I am just thinking of how to replace the BIM-160 with a DC-DC charger. Lots of unlabeled wires in the compartment. On the chassis side, there is just the thick cable to the chassis supply and a light gauge which I assume is monitoring voltage. But on the coach battery side, there is one heavy gauge going to the relay and three thin gauge wires--two might be solar input and the third voltage monitor? I will check next time I am out of the garage and see if there is current flow from the solar thru one of the lighter wires.

What I was thinking of doing is moving wires from the chassis side of the BIM to one busbar, moving the wires from the coach side another another busbar, and then running a single wire from each busbar to the appropriate terminals of the DC-DC converter.

PS: for the DC-DC I am thinking the 30A Victron Orion Smart non-isolated, running a single ground to a nearby busbar.

[@Michael]

Originally Posted by JonMN

For our REALLY cold weather, I could just take the risk, keep it plugged in (heated lithium) or wrap it in something like this

Or an RV tank heating pad? Preferably one with a thermostat. Don't want a melted battery case.

Originally Posted by JonMN

Right now I am just thinking of how to replace the BIM-160 with a DC-DC charger. Lots of unlabeled wires in the compartment. On the chassis side, there is just the thick cable to the chassis supply and a light gauge which I assume is monitoring voltage. But on the coach battery side, there is one heavy gauge going to the relay and three thin gauge wires--two might be solar input and the third voltage monitor? I will check next time I am out of the garage and see if there is current flow from the solar thru one of the lighter wires.

On mine, the solar is on an 8ga. red wire. Mine also had the Truma control panel wired directly to the coach side of one of the relays, bypassing the master disconnect. It has a 5 amp inline fuse. There may be a wire coming from the ignition to the BIM also.

See below for an 'as-built' wiring diagram from my 2019 22C. Yours may be different.

Originally Posted by JonMN

What I was thinking of doing is moving wires from the chassis side of the BIM to one busbar, moving the wires from the coach side another another busbar, and then running a single wire from each busbar to the appropriate terminals of the DC-DC converter.

I did something like that, but using terminal posts, not bus bars. My model has very little space in the electrical compartment.

Originally Posted by JonMN

PS: for the DC-DC I am thinking the 30A Victron Orion Smart non-isolated, running a single ground to a nearby busbar

Yep. That should work.

Wiring diagram:

[N147JK]

Depends on where it is. If it's outdoors and parked away from structures, then leaving it plugged in unattended would be marginally OK. If it's inside, particularly if it's inside sharing space with other vehicles, then no. Can you imagine what would happen if the charger and/or battery system malfunctioned and started a structure fire?!

[Winston]

Originally Posted by Davydd

If you have a second alternator I can guarantee you will not keep lithium batteries at 60% SOC like the experts have espoused. You will arrive every night at 100% SOC in a campground . . .

Why not install a simple on/off switch on your second alternator? No downside we can see and adds SOC maintenance flexibility.

Originally Posted by Davydd

That 60% not 100% may be an ideal but a cycle as ARV says is 100% down to 20% where they have set a cutoff.

One early lithium supporter/author referred to RV/Boat use of lithium as "fractional". We understood that to mean that rarely would such a system completely discharge the batteries and, possibly, rarely would they be fully charged. The cycling between highs and lows would depend on the loads applied and the charging available on any given day. No opinion was offered whether this 'fractional' use was good or bad or how to 'count discharge cycles' - - e.g. does 2 'fractional discharges' equal 1 complete discarge?

Your comments suggest that ARV has elected to configure their systems to force essentially full discharge cycles. We have, by contrast, chosen to set-up our chargers as Constant Voltage sources - - the voltage generally corresponding to 80% SOC. Of course we cannot maintain 80% SOC in the absence of the sun, shore power, or running the engine. But when shore power is available, our charger (power supply) maintains the battery at 80% SOC with the application of loads drawing upon the charger for its energy rather than the batteries. The batteries are largely 'inert'.

This raises the question: Does repeatedly cycling batteries through full discharge cycles cause more, or less, 'stress' to the batteries in contrast to maintaining the batteries at a fixed SOC level (and using the charger/power supply as the source of energy.)

Intuitively we assumed that the latter approach to be the less 'stressful' . . . but having respect for ARV, we'd love to know what they know that might be contradictory.

[Mpruet]

No - I don’t have any hookups that I use while in storage.

[g1g]

Originally Posted by JonMN

Greetings from Minnesota! I am lucky enough to be able to store my Class B in a spot with power available.

Would you disconnect the coach battery or leave it on shore power where it will be maintained. This is our first RV, so on a bit of a learning curve.

It's a 2022 Coachmen Beyond with AGM battery. Xantrex I/C.

I keep a BatteryMinder on both the house and start batteries 24/7 whenever it is not in use

[Philip53]

I don't have the problem of freezing temps during storage here in Louisisana, but I do have an insulated shop to house my van. So, pretty much my house and chassis battery charging is fairly easy - I keep a smart trickle charger on the AGM chassis battery continually, and while I do have the van plugged in to a 120v plug, I do not turn on the inverter/charger very often. It seems that I am in the van doing something at least every week, so I often turn on the lights & such, and I continually monitor the SOC meter. I have a contiuous 3-4 watt drain on my Victron system, which has 2 - 200ah Victron lithium batteries. Realizing it is not recommended to keep lithiums at 100%, I only recharge when the SOC gets around 40-50%, which occasionally goes beyond a month. Recently, while researching adding another solar array and a lithium battery pack to my house solar system, I came across a Victron statement that lithium batteries should be charged to full SOC at a minimun of once per month. They need that one month minimum to maintain balance of the battery cells. I turned on my charger a few weeks ago, and after charging, the inverter went into float mode (finished charging), but only showed 91% SOC on my Victron monitors. I repeated the charge cycle, and only got to 92% (indicated). I used the BMV712 monitor to reset to 100%. What I took from this is that long times in storage without charging can cause the indicated SOC to wander. I don't know if this was 'caused' by this longer than one month lapse between charges, but I think it probably was.

Here is a pic of my chassis battery selector switch. The Victron inverter has a 4a trickle charger built in to keep a 2nd battery charged. Since I don't leave the inverter on during storage, I select the smart trickle charger (Chg. Pigtail), to keep the chassis battery topped off, as I don't disconnect it from the chassis. While off grid camping for more than a couple days, I will select the Victron charger to keep the chassis battery charged.

[GeorgeKG]

There is a lot of good discussion in this thread, but I think it's important to point out that battery storage recommendations for state of charge vary between battery manufacturers and may depend on the length of the storage period. It is also temperature dependent. Our van has Lithionics batteries and the factory provides some pretty specific storage advice. Attached below as an example.

Bottom line - read the manual for your batteries.

[@Michael]

Originally Posted by GeorgeKG

I think it's important to point out that battery storage recommendations for state of charge vary between battery manufacturers and may depend on the length of the storage period

Yep - another example:

Battle Born Batteries says:

...Our batteries don’t require trickle charging. We recommend bringing the Battle Born Batteries to a 100% charge and then disconnecting them completely for storage. After six months in storage your batteries will remain 75 – 80% charged, if stored at -10°F to 140°F (-23°C to 60°C).