Thread: Dual Batteries

Originally Posted by LandyAndy

Hi Drivesafe
Your point about the inverter drawing power whilst not in use is good news.
Ive fitted a jaycar inverter for Lindsays computer and charging camera batteries etc.
Ive noticed a drop overnite in battery storage on my new jaycar battery monitor,I was thinking the battery was starting to play up.I will now fit a switch to the inverter so its only on when its needed.
THANKING YOU!!!!!
Andrew

I have a 300w inverter. If it's running flat out it can draw 20/30 AMPS. Youch.

CraigE, Another alternative is what I call the "A & B battery" approach, where you install two identical batteries under the 110 passenger seat and connect them to the main cable using a Cole Hersemann switch mounted on the front of the battery box under the passengers legs. I also run a new 50mm2 earth cable across to the transfer case (std LR earth cable is pathetic).

I use two Supercharge Gold MF batteries that you can buy from most auto sparkies for $135 each. They are identical technology to AC Delco's with about 700CCA.

This way you can treat the batteries as simply A or B or A+B when required. You have a very useful fourth switch position called OFF. Very necessary for when the inevitable LR electrics fire starts one day.

I usually switch to the fresh battery before morning start up, run that one for an hour (watching the voltmeter) then switch back to the other one for the rest of the day to get it fully charged for the upcoming night. I have also checked the calibration of the dash voltmeter so I can see what's going on.

This approach means I don't bother with deep cycle batteries (which alternators can never fully charge anyway), I can get a replacement anytime, anywhere and it is ridiculously simple.

KhunMoo

the only part of the standard cars electrics that i think should be moved over to the auxillary battery would be the main power feed to the stereo......
the memory feed can stay on the main battery......


this way.....you can still listen to your tunes whilst camped without worrying.......
i have also fitted one of those elcheapo flouro lights from supercrap in the cabin.....this is connected direct to the second battery
so i can have some lights in the car......

the idea is to be able to use what you need while the key is out of the ignition.....
with the key out of the ignition.....the only thing that can flatten your main battery is the interior light........

Hi KhunMoo, two points about your post.

Although the idea of a 3 way switch may have some merit, the very reason for having a DB controller is that you are always left with a charged cranking battery.

If your cranking battery, for what ever reason, ends up flat, then yes it would be nice to turn a switch and start off the other battery BUT the operation you described of switching from one battery to the other should only be done with the motor OFF and the best way to connect or disconnect the second battery while the motor is running is with an on / off battery switch connecting the auxiliary battery to the cranking battery, so that the cranking battery itself is NEVER disconnected from the alternator while the motor is running. This is one sure fired way to stuff the alternator.

The other point is that it is a myth that a deep cycle battery can not be fully charged from a vehicle’s alternator.

With everything wired correctly and the vehicle’s electrics functioning properly, there is absolutely no reason why an automotive battery of all types can not be fully charge by any vehicle’s alternator.

Guys,
Especially drivesafe thanks for the feedback. Will have a look when I get out of here tommorow night. Have to get it sorted as it would be embarrasing to have to get Black Betty to jump me over Easter.
Andy suspected this may be the problem, invertor has a switch but it is under the seat.
May have to just remember to turn the invertor off after every drive or look at some way for it to only switch on through the ignition without running off the cranking battery.
Any suggestions.

I went out this morning to fit a switch,almost cut the power wire and thought WHY DONT I JUST UNCLIP THAT NICE ANDERSON CONNECTION I PUT IN SO WE COULD PUT IT IN THE OTHER CAR IF NEED BE.
DOH!!!!!
Andrew

Originally Posted by KhunMoo

CraigE, Another alternative is what I call the "A & B battery" approach, where you install two identical batteries under the 110 passenger seat and connect them to the main cable using a Cole Hersemann switch mounted on the front of the battery box under the passengers legs. I also run a new 50mm2 earth cable across to the transfer case (std LR earth cable is pathetic).

I use two Supercharge Gold MF batteries that you can buy from most auto sparkies for $135 each. They are identical technology to AC Delco's with about 700CCA.

This way you can treat the batteries as simply A or B or A+B when required. You have a very useful fourth switch position called OFF. Very necessary for when the inevitable LR electrics fire starts one day.

I usually switch to the fresh battery before morning start up, run that one for an hour (watching the voltmeter) then switch back to the other one for the rest of the day to get it fully charged for the upcoming night. I have also checked the calibration of the dash voltmeter so I can see what's going on.

This approach means I don't bother with deep cycle batteries (which alternators can never fully charge anyway), I can get a replacement anytime, anywhere and it is ridiculously simple.

KhunMoo

Exactly how my system is set up and I operate it in almost the same way, and dare I say have been using said system for nigh on twenty years with never a problem.

Drivesafe,
I NEVER EVER switch to OFF with engine running ... stuffs alternators. Cole Hersemann switch is a make before break switch that never disconnects a battery if you switch between A - A+B - B. It's bullet proof and been around fro decades.

The manual switch requires the driver to keep the battery status in his head at all times, with the help of a voltmeter. It does not work too well for people who need it to be automatic. A Piranha 180S is much better for them.

KhunMoo