Simple dual battery question.

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MikePL

MikePL

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Bonsall, CA
I am planning to install another battery. It is supposed to supply current to such things as lamps, a laptop and other stuff while camping. My setup seems simple and straightforward but it's better to ask if it's OK.

I would like to connect the additional battery in parallel with the main one. Between those batteries I would like to put a switch to open the circuit.

My idea is to start the truck only with the main battery and when the engine is running, connect the additional one for charging. After a trip I plan to disconnect the battery from the main one and use it. If it drains out then no problems because I can start the truck with the intact main battery and flip a switch to charge the additional one.

I plan to buy a small capacity battery as I don't think I will need such a cow as the stock one.

Will it work? Will the stock alternator cope with charging two batteries? Is my design electrically OK?

And the last question... Are there any cons when it comes to mounting the battery under the truck? Specifically by the frame rail under the driver's seat. I plan to weld a kind of a shelf to the frame and place the battery there...

And comments are welcome as I am planning to do this tomorrow...
 
There is no problem doing that - it is fairly common. George has a good writeup on this - except he used a relay that automatically connects the second battery when the alternator produces power.

auxiliary battery and winch

As per putting the battery under the truck - no problem although I would get a sealed AGM battery for the job. Also remember that the longer the cables are - the higher the electrical losses.
 
1 minute of searching yielded...

MikePL said:
I am planning to install another battery. It is supposed to supply current to such things as lamps, a laptop and other stuff while camping. My setup seems simple and straightforward but it's better to ask if it's OK.

I would like to connect the additional battery in parallel with the main one. Between those batteries I would like to put a switch to open the circuit.

My idea is to start the truck only with the main battery and when the engine is running, connect the additional one for charging. After a trip I plan to disconnect the battery from the main one and use it. If it drains out then no problems because I can start the truck with the intact main battery and flip a switch to charge the additional one.

I plan to buy a small capacity battery as I don't think I will need such a cow as the stock one.

Will it work? Will the stock alternator cope with charging two batteries? Is my design electrically OK?

And the last question... Are there any cons when it comes to mounting the battery under the truck? Specifically by the frame rail under the driver's seat. I plan to weld a kind of a shelf to the frame and place the battery there...

And comments are welcome as I am planning to do this tomorrow...
Click to expand...

This information is linked in the FAQ:
https://forum.ih8mud.com/80-series-tech/84888-faq-80-lx450-may-2009-added-rotf.html

The link you are after is:
https://forum.ih8mud.com/80-series-tech/104630-faq-addition-dual-battery-set-ups.html

Something that might be MUCH easier than welding a special box in the under side is to move the washer bottle back into the dead space behind the air cleaner:
http://www.sleeoffroad.com/products/products_battery.htm

Then there is room for another factory battery tray from a '92 or similar vintage truck when the batteries were on the other side. The bonus is this is a direct bolt-up solution. Here is a very good picture of what it looks like when done.
IH8MUD Forums - View Single Post - FAQ addition: Dual Battery Set-Ups

Lots of great information in the FAQ and a little search finds it pretty easily.

Now, as for parts you can get in Poland... That is going to be the trick.
 
Many thanks for those links. I've been reading them all evening.

But there is still one doubt I have. Namely the battery isolator/separator. All people use it. Should I?

I plan to do a manual battery charge and disconnect the aux battery from the main one when I need it. Do I need a battery isolator?
 
I don't think that you must have an isolator. It is just convenience, and makes the system automatic. No manual switching.
 
The isolator is to keep both batteries from being discharged when you forget to open the manual switch you plan to install and think you are only draining down one battery, but are really draining both. If you have a memory that never fails and always manually isolate the batteries when you power up your camping lamps and laptop you should be fine. But all it takes is for you to forget once and you've defeated the purpose of having a backup battery.
 
You could accomplish what you are after with a battery disconnect solenoid. It will do exactly what you have described and you will never have to manually switch anything (but you could install a switch inside the rig to parallel the batteries). My personal favorite is the Sure-Power 1315-200, but there are other models that would work.http://surepower.com/pdf/separatorinterconnect.pdf
 
IPOR sells a seperator that automatically connects the two batteries when the main battery reaches a voltage above 13.8. and disconnects below 13.8 volts. it also has a manual operation in which a momentary switch is wired. if the main battery dies and the vehicle won't even act alive, then push and hold the switch, and turn the key. i have installed this setup many many times and is always works well.

i don't remember the exact amperage rating on the seperator, but it is enough.

EDIT: the Sure Power seperator is the one we use. i don't remember the exact #
 
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MikePL said:
Many thanks for those links. I've been reading them all evening.

But there is still one doubt I have. Namely the battery isolator/separator. All people use it. Should I?

I plan to do a manual battery charge and disconnect the aux battery from the main one when I need it. Do I need a battery isolator?
Click to expand...

I do not use a battery isolator. I use big marine switches. If you do not have a winch, you would only need one. Or, you could run a 2nd switch and have it dedicated to turning off your appliances. The disadvantage to these is that you will likely have to lift the hood to change their position.

IH8MUD Forums - View Single Post - FAQ addition: Dual Battery Set-Ups

The switches are the two red boxes to the left of the hood latch where the horn used to be. They are radium faced dials and glow in the dark and will for the next 6400 years or so. Yes, my truck is radioactive.

The one on the right controls the 'house load'. I.e. everything related to operation of the truck. It can be set to battery 1 (on the right), battery 2 (on the left), both (parallel) for charging or Off (handy for shutting it all down).

The one on the left controls the 'winch load'. It is dedicated to the winch and allows it to be isolated from the house load or run off of both batteries at the same time.

I usually leave the winch switch 'off' and the house switch to 'both' so the batteries stay charged.

You will also notice that I put real big fuses directly on both batteries. With the big cables running live from big batteries, I was starting to get nervous about the idea of having a welded short. Circuit protection is something missing from most battery combiners. If the fat wire/cable going from the battery to the switch/combiner shorts, you could be in a world of hurt.

Edit: One more note... I used factory matched Optima Yellow top D31A batteries. If your batteries are not factory matched, there is a good shot of a parallel system eating them in short order. A battery isolation system (Hellroaring, etc) alleviates this issue and prevents cross charging.

IMHO YMMV
 
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I have my backup battery mounted in the location you mentioned with the Metaltech slider battery tray. It has been about six months now and lots of wheeling including practicaly submerging the battery underwater and no problems so far...

100_4487.jpg



https://forum.ih8mud.com/80-series-tech/266420-metaltech-slider-battery-install.html

:beer:
 
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