I don't agree with pulling batteries unless for long term storage ( more than a year) and even that would only apply to the RV.

Modern vehicles, especially Mercedes, BMW, Audi have long term settings that are kept in memory. Further many have the battery 'registered' to the car - meaning the vehicle's electronic memory keeps track of how long the battery has been installed and adjusts amp / voltage over time according the remaining useful life.

I have seen way more harm than good by a well intended battery removal. If you did not know, prior to removing a battery - the system modules need time to 'go to sleep'. Meaning that with the trunk open, you have to manually close the trunk latch ( there's a micro switch ), turn everything off, lock the car and then give it at least 20 minutes.

Even with this procedure you still can create a monster of a problem. 1 of which when you reinstall the battery and the modules 'wake-up' some may not communicate with each other or other issues arise that only can be corrected with OE or OE compatible programming software.

RV's are on the other end of the spectrum where the various add-on accessories create a fairly large draw ( excess of 70 Ma) on the batteries at rest. Most RV's I've seen have multiple stages of wiring and accessories installed many of which are after the initial build where it is just plain sloppy. As in: the default is to tap into the 'Bat' circuit when all else fails to find the appropriate 'Key-On' supply feed.

Believe it or not, short battery life is with the loss of electrons is through the case. Better batteries have thicker cases. 2nd largest is a dirty battery top.

I really like and use Interstate batteries so you have at least two of those I see. Keep the cases and top clean, keep your posts / terminals clean; that's it.

In your cars I would not recommend any 'protectant' as they live inside the trunk or rear floor. Unless your RV has a 'sealed' battery compartment I would recommend an oil based protectant lightly sprayed onto the terminals to avoid corrosion. One product that I use is NCP2 Battery Corrosion Preventative.

The cars and RV are not stored at my house so I have no way of getting there to monitor the battery tenders. The cars are an 84' and 85' diesel, so pulling the batteries does no harm to anything electric. Hell they will run without a battery in them! I would much rather pull them for the 5 months they are sitting, makes it much harder to steal the cars or RV if you can't start it up.

I don’t think the drain down is necessary with a good maintainer. But, a good maintainer has some pretty sophisticated circuitry, putting 18 cells in parallel may confuse it if it’s only expecting six. I’m no expert and I’d probably try what you are trying, understanding that one bad cell ca eff up the whole system and result in over or under charging.

Charging batteries with different Ah profiles will not work properly.

I don't think this is the best idea.

If one battery is low, the charger may boost the voltage to bring it back up - but it will also be pumping the electrons into the full battery. You really need one for each.

+1 AMHIK :o

Anyone who has seen a storage garagefull of cars and toys burning to the ground with only a battery tender running gets new found respect for how wrong things can go.

There are multi bank charger/maintainers made. I'd suggest looking into those. Either that or put a maintainer on just one battery, mark you calendar, and go from battery to battery every couple of weeks or so.

https://www.batterystuff.com/battery-chargers/12-volt/multi-bank/

I know 2 that have burned their house down due to battery tender fires. A 3rd ( Deputy Fire Chief) with an extension cord to a light bulb.

With my many bikes and snowmobiles, each get charged for 8 hrs one a month. My batteries last longer than anyone I know.

I replaced the original battery in my 2004 GMC 2500hd last winter.
Sometimes you get a good one!

Thanks, Paul - I never knew they made these.

Here's what I need...lol.......

https://res.cloudinary.com/dyuctplmh...op-Charger.jpg

Don't be this GUY:

http://forums.pelicanparts.com/uploa...1574019429.jpg

I have that one Baz, seems to work just fine.

Recomend a trickle charger
 

Looking for a charger that will automatically reset itself when there is a power outage.
Looking for a inexpensive unit as I have 3 CTEK units but only one will reset itself automatically.

What do you mean "reset itself automatically"? If the power goes out and then turns back on, the tenders you have don't just come back online? I've had a Yuasa, Schumachers, and now Noco (Genius 1) chargers that just go on whenever they're plugged in.

Yep, mine would just start up again as if I had unplugged it and then plugged it back in(?)

By Reset, I am saying the charger will resume its charging process without human intervention. If the power goes out, as it always does in the winter, the charger will go to Mode when power is returned and will standby waiting for human intervention to push the buttons to Car icon and then the charger will resume charging the battery. I am gone 6 mos in the winter and the battery will be dead because no one is there to press the Mode button to Car icon.
My other CTEK charger model 3300 will reset by itself without anyone going into the garage and have to push the buttons on the unit so it can resume charging. I cannot exchange this unit it for the other unit is because its dedicated to the other vehicle.

I guess I'm lucky I've never encountered that "feature" in any of the battery chargers I've had. I used to like the Schumachers, because they worked great and were cheap ($25-30). But Schumacher doesn't make those models any longer. So I switched to a pair of Noco Genius 1 chargers which I purchased off Amazon for about $25 each. They work great. Plug in and forget.

In regards to the Noco - how about during a power outage, will it resume charging on its own without you touching it?
That's what I am looking for as I am gone for 6 mos. in the winter with no one home.

When I plug it back in, I don't have to push any buttons. It detects the type of battery, state of charge, and just does its thing. So no experience with power outages, but I would think that wouldn't be a problem.