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has driven a Ford lately.
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Was thinking it might be nice for camping/other activities to have a second battery in the truck as a reserve. The first battery would be a deep cycle battery (yellow top or whatever) and the second a cheaper item (costco/kirkland probably). I'd want a switch on the second battery (which would normally be closed), such that I could (potentially) fully drain the deep-cycle battery and not be stranded.

Good idea? Bad idea? The one thing I've never seen here is the switch, but I'm a total noob when it comes to this stuff.
 

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look at the painless dual battery solenoid. I'm installing one on my truck for this purpose (amps 2x inverters, 2x compressors etc...) It isolates each battery form each other and when You want to start it up it uses both the batteries amps to get it to turn over. It also has three modes depending on the swith location, Here is a description for each:

The selector switch has three positions, which operates the system.
Switch centered; the main battery is used only for vehicle operation. The solenoid is not activated
and the auxiliary battery will not be charged.
Switch activating green light position; the main and auxiliary batteries are connected for charging
and starting and the green light is illuminated when the key is in the on position.
Switch activating the red light position; the main and auxiliary batteries are connected together
and the red light is illuminated at all times regardless of ignition switch position.

Here is the product I'm talking about:http://www.painlessperformance.com/webcatalog/largeview.php?SearchField=40102
 

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Wanna B Jack o all Trades
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you can get just a 200 amp relay for $40-$70ish and then you just need terminals and wire
 

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I think I paid around $120 for the painless. It comes with good instructions and all the stuff you need to hook it up (minus big guage wire, which I suggest). I'm not sure I like the one you posted IMO. Either one accomplishes your task so I suppose its about look at this point.


Thanks, that looks quite trick, but is probably a bit too much for me. Think I'll probably do something cheaper, e.g.: http://www.pirate4x4.com/tech/billavista/dual_battery/my_dual_battery_setup.htm
 

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Wanna B Jack o all Trades
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just buy an isolater and wire its cheap, easy, and it works
but then you really need a higher output alt to overcome the .7v drop that they induce
 

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Pebble Pushers
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you can get just a 200 amp relay for $40-$70ish and then you just need terminals and wire
word or a circuit breaker & just flip the switch when you want to disconnect the 2 batteries
 

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Pimpin' ain't easy
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but then you really need a higher output alt to overcome the .7v drop that they induce
see what your sayin but it is just like a charge line setup for a tow pkg (i.e slide in truck camper is my best example), and I have yet to see a setup like that crap out an alternator i guess maybe if you actually kill the second battery
 

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Read Only
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Was thinking it might be nice for camping/other activities to have a second battery in the truck as a reserve. The first battery would be a deep cycle battery (yellow top or whatever) and the second a cheaper item (costco/kirkland probably). I'd want a switch on the second battery (which would normally be closed), such that I could (potentially) fully drain the deep-cycle battery and not be stranded.

Good idea? Bad idea? The one thing I've never seen here is the switch, but I'm a total noob when it comes to this stuff.
I'm on here for the same thing ... Wanted to get the dual battery set up in my 2015 2500hd 6.0 .. since it's got the plow prep package it's got the second tray but no wiring .... So I've been doing some of my own research and trying to find the best option and I think I've got what I want to do.
I've got the fuse block that goes ontop of the main to go on the second battery ( wanted them to look the same )
Went into gm parts direct and looked for the Duramax dual battery wiring and picked up the positive cable for the secondary and will be buying the negative as well ...
The positive will run from the secondary to an isolator and the main and the ground in the secondary will go to the frame ..
This way when the truck is off it will drain only the secondary but when the truck is on they will both charge
 

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Master of Light
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I'm currently running a dual-battery setup in my 09 using a battery isolator. The main battery is a standard (non deep cycle) and the standby is an optima yellow-top. I've also wired in a momentary switch over-ride from the secondary battery to trigger the isolator. If the main battery is insufficiant, I can manually trigger the standby from in the cab and have enough power to crank over.
 

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I dont have much to offer in the way of options, But My 02 3500 Sierra came with dual batteries. I keep replacing both but every time I get new batteries the 2nd battery located on the passenger side is totally dead. Does that battery not get charged by the alternator? What is it for?
 

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Master of Light
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I dont have much to offer in the way of options, But My 02 3500 Sierra came with dual batteries. I keep replacing both but every time I get new batteries the 2nd battery located on the passenger side is totally dead. Does that battery not get charged by the alternator? What is it for?
Assuming your 3500 is a diesel, they need more amperage to start than a gas engine. If one battery is newer than the other, the older one will go bad first and start sapping power from the good battery. If you are consistently replacing one battery, there is likely a wiring issue.
 

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Assuming your 3500 is a diesel, they need more amperage to start than a gas engine. If one battery is newer than the other, the older one will go bad first and start sapping power from the good battery. If you are consistently replacing one battery, there is likely a wiring issue.
Actually its a gas 8.1. I never even check the aux battery other then the 3 or 4 times now when its time to get a new battery we throw a meter on the aux batt and its stone cold dead. I was wondering if its supposed to be charged off the alt as well as WTH is it for? I ordered that truck to be built for me and remember checking the box Dual batteries.
 

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Master of Light
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For a gas motor, the aux battery should be a standby. Ideally it would have an isolator connecting it to the charging system only when the ignition is on. You can see if you have this by disconnecting the cables and measuring voltage across the cable with ignition off (should be zero volts) then ignition on (should be 12v)
 
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