I don't drive my 4Runner often, unfortunately, so the batteries sit idle for weeks, sometimes months at a time. I have another "just for fun" car that also sits idle for a long time but that one only has 1 battery so I have it connected to a CTEK MUS 4.3 Battery Charger. I want to do the same for the 4Runner, but the 4Runner has a dual battery setup so I have a bunch of questions.

1. Does the dual battery system even matter for trickle charging?
2. Is it safe to do this?
3. Do I need a special type of charger or would a standard one work?
4. If it is safe, which battery should I hook to, primary or secondary?
5. If this isn't going to work, is there anything else I can do?

I have the IBS-DBS Dual Battery System with Microprocessor and IBS RBM Relay Booster Module. Anyone with experience with a dual battery setup and trickle charging, please let me know how you do it and what you use.

Thanks in advance for any and all help/advice/knowledge you share.

I had a NOCO Genius 2 bank on board charger permanently mounted in the back and a flush mount AC plug (male connector) on my back bumper. I just lifted the little flap on the bumper and plugged into an extension cord once/week to top off everything. Worked great.
It’s all somewhere in my build thread.

Just to be clear, you had this on a dual battery setup? If so, what management device were you using? IBS, National Luna, etc.? Did you have to make changes to that system during the charge? Also, which battery did you hook the charger to, primary or secondary? Thanks.

Not sure how the IBS-DBS Dual Battery System works but I use Blue Sea and only need to connect the charger to one battery and it will automatically do the rest to charge the other battery. Your system should do the same.

I use a battery tender on my diesel that has two big batteries. I put the charger on the battery that is downstream from the first battery, been doing this for many years with no issues, it just takes a little longer to get them full versus doing a single battery.

a 2-bank charger would monitor and charge each independently

The dual bank charger was used on both batteries. It worked great. It will work independently of anything you already have hooked up.

My battery setup was different than others- It was very simple and reliable while I had the 4Runner It's all in my build thread.

Something he stole off me...like most of his good mods.

I’m glad our love affair is still going strong.

I used this one, mounted behind my front bumper. It works very well and it’s made for dual batteries. It’s designed to charge the start battery first. The battery charger is going to work independently of anything else, so it won’t be an issue.

ProMariner Multi 43008 Battery Charger Prosport 8 Amp https://www.amazon.com/dp/B00F5EBQ36..._EVyNCbJAA2F07

Thank you all for your help and input. I think I now know enough to keep my 4Runner's batteries charged. I appreciate everyone chiming in and dropping some knowledge.

OP. Since its not a daily driver just Isolate the batteries and charge them separately. This way you will be aware of the health of each battery before one goes south on you. I have one Odyssey (main) and one Optima. I use a Ctek 7002 charger. Your Ctek Mus 4.3 should be fine.
What type of batteries do you have?