Charging source for bed mounted battery

Captm

Adventurer
I picked up a SDH marine group 31 agm battery to mount in the bed of the 2005 taco w/ tow pkg. for fridge,lights and schnozs machine. While I plan on going with the Blue Sea 7622 for battery management is there a reason why I couldn't just use the power from my trailer connection?
 
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tstege

Observer
Captm, let me know how this turns out. I am completely insure of how to set up a second battery and would love to see what you end up with. I was just gonna start a thread for this purpose till I saw yours. I wanted to add a battery in my 01 Tacoma for lights, roof vent, radio, and charging my electronics when camping.
 

4RunAmok

Explorer
One good reason I was actually discussing with my boss today (we do this stuff for a living!)

If that battery needs a good charging, and you start up your vehicle, it's going to try to pull something like 60 amps through that little tiny light harness, and you're going to fry it.

The size of the wire you run from the battery to the second battery will depend on your uses. You could easily get away with 8 or 6 gauge wire for the small items you mentioned. It just has to be able to handle that draw if it needs to, and if you're running a fridge off of it, it WILL need to..

Now, the Blue Sea 7622, excellent choice... that unit is rated for 500 AMPS! You wouldn't want to draw THAT through that little light harness! :D
 

4RunAmok

Explorer
Captm, let me know how this turns out. I am completely insure of how to set up a second battery and would love to see what you end up with. I was just gonna start a thread for this purpose till I saw yours. I wanted to add a battery in my 01 Tacoma for lights, roof vent, radio, and charging my electronics when camping.

This can actually be a very pain free process. A lot of people spend a LOT of money when they don't have to...

Basically you need to protect your starting battery, not with an isolator, as those will actually hinder charging unless you spend big bucks on one.

So, one way is with the Blue Sea 7622 like Captm is going to use. What this does is simple: It disconnects the batteries when the car is off. You don't want them connected when you're running your accessories in the back and drain BOTH batteries when the car is off, or you won't get it to start again! But you DO want them connected when the engine is running so that the alternator can charge both batteries. The 7622 can do this by tapping a 12 volt source that is only on when the engine is running, this way it disconnects the two batteries when the cars is off.

The 7622 also has a manual switch on it so that you can override. You might want to do this if your starting battery died, and you need to use the second battery to boost the starting battery so you can start the car. No problem, flip on the manual connection and there's your boost pack!

You can pick up a 7622 on ebay for $150.

The other thing is breakers. You want a breaker at each end of the wire between the batteries, 70 amps. Each breaker should be within 18" of the battery its protecting, the closer the better. If something gets the wire in the middle of the run, both breakers will pop, protecting each battery from short.
 

goodtimes

Expedition Poseur
The other thing is breakers. You want a breaker at each end of the wire between the batteries, 70 amps. Each breaker should be within 18" of the battery its protecting, the closer the better. If something gets the wire in the middle of the run, both breakers will pop, protecting each battery from short.


Doing that will limit what you can move to 70 amps. If one of your goals is to be able to start your engine from the aux battery, or have the aux battery tied in when you are winching, 70 amps isn't going to cut it.
 

Captm

Adventurer
Schnoz machine = CPAP... while my snoring keeps the bears away my wife doesn't appreciate it. :ylsmoke:
Wire size, that was too easy also might explain why I blow a fuse when trying to charge the 200 amp battery on my trailer.
So I'll just forget the factory system and go with the Blue Sea 7622 and Anchor wire. Make that 2 of the 7622 so I can charge 3 batteries - 2 truck , 1 trailer.
 

Fastlane

New member
This can actually be a very pain free process. A lot of people spend a LOT of money when they don't have to...

Basically you need to protect your starting battery, not with an isolator, as those will actually hinder charging unless you spend big bucks on one.

So, one way is with the Blue Sea 7622 like Captm is going to use. What this does is simple: It disconnects the batteries when the car is off. You don't want them connected when you're running your accessories in the back and drain BOTH batteries when the car is off, or you won't get it to start again! But you DO want them connected when the engine is running so that the alternator can charge both batteries. The 7622 can do this by tapping a 12 volt source that is only on when the engine is running, this way it disconnects the two batteries when the cars is off.

The 7622 also has a manual switch on it so that you can override. You might want to do this if your starting battery died, and you need to use the second battery to boost the starting battery so you can start the car. No problem, flip on the manual connection and there's your boost pack!

You can pick up a 7622 on ebay for $150.

The other thing is breakers. You want a breaker at each end of the wire between the batteries, 70 amps. Each breaker should be within 18" of the battery its protecting, the closer the better. If something gets the wire in the middle of the run, both breakers will pop, protecting each battery from short.

A lot of good info here, except that last part (addressed below) :sombrero:

Doing that will limit what you can move to 70 amps. If one of your goals is to be able to start your engine from the aux battery, or have the aux battery tied in when you are winching, 70 amps isn't going to cut it.

70 amps is a bit low, imo. Of course, you can always run fuses instead of breakers (old school, right?) and you will want them to be pretty large - the good news is that large fuses (unlike large breakers) are pretty cheap... you will just need to carry spares.

No way I would charge the group 31 off of a trailer harness. CCA charging wire is so cheap that there really isn't a good reason not to run a strand back to the bed, and run another 2ft to the frame for a solid ground. 2ga should be plenty, use the money you saved not buying 0ga and enjoy some beer. :)
 

4RunAmok

Explorer
Ok, so the reason I suggested a 70amp breaker is because the rear battery isn't likely to draw more than 60 amps from the alternator should it be seriously drained.

And in a proper setup, you should rarely need to start from the rear battery, since the whole purpose to this exercise is to protect the starting battery from discharge :D

So what is the recommended breaker/fuse size if by chance you need to start from the rear battery? Something is telling me 150 is plenty, and hoping so, because I have four 150amp blue sea breakers :) and I'm getting ready to put a second Odyssey PC1700 in the back of my 4runner.
 

Fastlane

New member
What amperage the alternator is charging the battery is not as much of a concern as what you would be drawing from the battery if necessary. Things like winches and inverters draw huge amperage, this is mitigated if the alternator is working. I would think you would be ok with your 150amp breakers, depending on what is running off of that battery.
 

4RunAmok

Explorer
I don't have a winch, and if I did, I probably would keep both batteries in the front of the truck so as to allow the cables to be short and larger gauge.

For me it will be that ARB fridge when I win it, some LED lighting, my amplifiers for my stereo, that's pretty much it. Running a thermoelectric cooler now, but I want to get rid of that.
 

Captm

Adventurer
Parts ordered

So I ordered my parts - Blue Sea (2) ML-Series Automatic Charging Relays (Magnetic Latch)- #7622 and (1) SafetyHub 250 Fuse Block with Remote Battery Switch -#7727. The 7727 has three switched 30A−200A MIDI®/AMI® fuses which will be used for winch, off road lights, trailer battery charge. It also has four 24-hour 1AFour 24-hour 1A−20A ATO®/ATC® fuses−20A ATO®/ATC® fuses that will service the reefer, interior lighting, CB, and 2m. I'll post up photos and schematic when I get to the install next weekend. I need to wrap up replacing (16) 8D, (2) 4D batteries along with a new 4000w inverter. Naturally the cables between the battery bank and new inverter (different model from the old) are 1" short .
Cheers.
 

off-roader

Expedition Leader
Not sure that you need such a high current line...I charge my golf cart 12v AGM deep cycle that i keep in back for my arb fridge via the OE 10A (maybe 15A at the most) cigarette adapter back there.
 

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