Keep your +12 Battery topped off while you can't drive it for weeks!

Hello again, Boys & Girls. Well here at the RR Electronics Labs, we are getting ready for a major personal body modification. So we need to modify the car a bit first!

In the upcoming weeks I will be having this mod done to me...

Anterior cervical discectomy and fusion ... Google it...ouch!

In preperation for this surgery, and because I will not be able to drive my Prius for several months after, I needed a way to keep the +12 battery in my Prius at ready levels. When I bought the Prius 3 years ago, I decided to park my 4Runner and just keep its battery topped off. I tried a standard battery charger, NOT, it just helped cook the battery, I tried Solar Charging, what a pipe dream that was. After a period of 6 months, the battery finally died. I then bought a large Optima battery for the 4Runner and this handy little device..
Amazon.com: Ctek Battery Charger #56-158: Automotive
Four-step Automatic Battery Charging Cycle
There is no need for any specific knowledge of batteries or their charging methods; the Multi US 3300 will take care of it. The Multi US 3300 utilizes a four-step automatic charging cycle. First, patented desulphation functionality allows for possible reconditioning of batteries that have lost significant power due nonuse. This is followed by Bulk Charging, when 80% of charging takes place; then Absorption Charging which completes charging up to virtually 100%; and finally Pulse/Maintenance Charging, in which the battery receives a pulse of electricity when the voltage drops below 95%, keeping the battery in perfect condition indefinitely when it is not used. If the battery is loaded and the battery’s terminal voltage drops to 12.9V the charger automatically switches back to the beginning of the four-step cycle. Also, the Multi US 3300 can be connected for months and it is specifically developed for seasonal vehicles.

After installing this charger 2.5 years ago, NO MORE BATTERY PROBLEMS!!!

So, lets put a temporary one in the Prius... Here's the little beauty now..


When I purchased mine, I paid $56.00, since prices vary, you may pay more or less, what ever... it's well worth it!

I wired it directly to the battery terminals. It has a quick disconnect plug, so removing it is a snap!


I found that by wiring it this way I was avoiding the IR loss of the negative lead and chassis. It measured .9 ohms. While this seems quite small, and it is, this will mess with the charger, so to avoid any problems, it's wired directly to + and - terminals. Make sure to mind your polarity. Plus to Plus, Minus to Minus...
Hooking it up backwards is BAD Egon!


After you button up the tire well, plug the charger in. Hit the mode button until the LED by the car icon lights.
That's it.
Sit back and have a beer, you do not have to worry about parking your car for extended periods of time.
Needless to say, you WILL have to have a source of AC power within an extension cords reach, for this to work ! But when I need it here at home, we're good to go!


OK it's working fine, and after a couple of hours the Orange LED on the top row will go out, the Green one next to it will lite. SWEET, a fully charged Optima Battery!!! This will work on whatever brand of battery you have in your car!
Since the charger will get warm to the touch, and I believe electronics should run as cool as possible, I mounted the charger to a flat plate of aluminum I had laying around. It's more than adequate as a heat sink. I clamped a vise grip to it so it will stand up. On the 4Runner, I have its charger tie wrapped to the front grill, that charger stays cool always!


Just be carefull when you drive away, UNPLUG THE CORD!!!, I have mine set to unplug itself if I forget!
I do not have to worry now, a full charge is just a cords length away!

Life should be so simple!