How to make a cheap isolated dual-battery setup for $50

[Vicreo A Legarreta]

Thanks...that is what I thought.

but I will recommend to use deep cycle or gel batteries, will not mix wet ( or flooded battery )with other type of battery

 

[ETAV8R]

So if I'm using a CTEK controller instead of a solenoid do I still need an 80A fuse between the batteries and the controller?

 

[teotwaki]

Where is everyone getting trays to mount a second battery under the hood?
I have a 2009 Tacoma and there is definitely a place for a tray.

http://www.ballisticfabrication.com/search.asp?keyword=battery&search=GO

http://www.trail-gear.com/tg-battery-box

http://www.ruffstuffspecialties.com/catalog/BatteryBoxes.html


Anyhow, I thought you said that you wanted to have dual batteries on the same side as the OEM set up. You need to let folks know what your specs might be.

And...............


wait for it.....................

Search the forum? :elkgrin:

 

[teotwaki]

So if I'm using a CTEK controller instead of a solenoid do I still need an 80A fuse between the batteries and the controller?

Fuses and breakers are your friends

 

[nat]

I am currently using a switch actuated solenoid to send power to the battery I have in the bed of my truck. Sometimes I forget to turn it on or off. Would this survive being mounted in a truck?

 

[LandCruiserPhil]

I am currently using a switch actuated solenoid to send power to the battery I have in the bed of my truck. Sometimes I forget to turn it on or off. Would this survive being mounted in a truck?

I have my aux battery mounted in the back of my Land Cruiser with no problems. The problem I do see is running down the battery supplying the voltage to the coil on your solenoid.

 

[nat]

I screwed up my post..............doh!

http://www.batterystuff.com/battery-products/switches/Bi303303.html

I want to replace my solenoid with this. Any issues with the unit?

 

[4RunAmok]

I screwed up my post..............doh!

http://www.batterystuff.com/battery-products/switches/Bi303303.html

I want to replace my solenoid with this. Any issues with the unit?

These units use Diodes to "isolate" the batteries.

Diodes are an inefficient method for the task because they reduce the amount of voltage to BOTH batteries. So both batteries will never fully charge through this unit.

You are better off keeping your current solution, but adding a regular 30-40amp relay connected to the ACCESSORY wire at your steering wheel to engage your solenoid. It is important that you use the Accessory wire instead of your Ignition wire, as this will keep the batteries separated during starting. You can then use your manual switch hooked to ignition to send 12 volts to the solenoid directly as an override, in case you need to use your aux battery as a jumper. But if you do this, make sure you're using large enough wires to hook up the aux battery into the main battery system. Never smaller than 6 gauge, 4 gauge should be plenty for most purposes, 2 gauge if there is a distance longer than 12 feet between the two batteries.

 

[dlichterman]

More dumb questions! I finally got my solar mounted, and I am ready to start getting the isolation circuit put together. How many amps do starters really draw? I see the updates 200A fuses, does this mean the 200A solenoid would be ok for a self-jump? Found this one for 30 bucks cheaper...

http://amzn.com/B000CEBXRS


So, pair that with some nice large wire, some 200A ANL fuses and I'm good to go? Or do I go for the 500A version....gonna probably do a 3-way switch with on(auto + timer), off(disconnected), and on(self jump).

 

[Livelarg]

So my set-up is working great. Is there a way to show battery charge on one or both batteries? Is there a good mo it or system?

Thanks

 

[4RunAmok]

More dumb questions! I finally got my solar mounted, and I am ready to start getting the isolation circuit put together. How many amps do starters really draw? I see the updates 200A fuses, does this mean the 200A solenoid would be ok for a self-jump? Found this one for 30 bucks cheaper...

http://amzn.com/B000CEBXRS
View attachment 174462

So, pair that with some nice large wire, some 200A ANL fuses and I'm good to go? Or do I go for the 500A version....gonna probably do a 3-way switch with on(auto + timer), off(disconnected), and on(self jump).

200 should be plenty.

 

[4RunAmok]

So my set-up is working great. Is there a way to show battery charge on one or both batteries? Is there a good mo it or system?

Thanks

Check Ebay for Voltage Meter. It's a good idea to have it switched off when the batteries are not charging, so either build a switching circuit, or simply use a momentary switch to check voltage when you want to.

 

[Livelarg]

Won't a volt meter just check how much juice it's producing? Is there a way to show te level of charge per battery? A volt meter is a great idea to make sure 2nd battery is
Being charged. Thanks

 

[dlichterman]

Check the table in this PDF for rough estimates.

http://www.mmbalmainauto.com.au/PDF/State_of_charge_12_volt_batteries.pdf

 

[lysol]

Won't a volt meter just check how much juice it's producing? Is there a way to show te level of charge per battery? A volt meter is a great idea to make sure 2nd battery is
Being charged. Thanks

The volt meter will actually tell you the state of charge. It's best to let the battery sit for about 5 - 10 minutes after the charging device is stopped or removed before taking a voltage reading for more accuracy.

Think about it like this.

Volts is the pressure. Amps is the current. Watts is the power. That's how I've always understood it. The PDF file that dlichterman posted is a nice state of charge chart to reference. Any battery meter that give's you a percentage of charge is simply volt meter that has programming like the PDF chart and then displays to you a % instead of a voltage reading. I would get a simple volt meter like this one:

http://www.amazon.com/4-5-30V-digit...UTF8&colid=FBSD1JSLBAXO&coliid=I38JVTHSA5452T

It's a simple positive and negative wired volt meter. Hook up a momentary on switch on the positive wire and BAM!!! you're done.