utherjorge
Observer
I've looked at the diagram on the first page (and then the updated one) and I still don't understand how the new-ish tech from page 98 (or so) works or is an improvement. Did I miss a diagram?
How to make a cheap isolated dual-battery setup for $50
- Thread starter evldave
- Start date
dwh
Tail-End Charlie
What newish tech?
The original diagram shows how to hook up a "split-charge relay". Dumb, no brain, ignition controlled.
There are also smart split-charge relays on the market, which use a small computer brain to automatically engage/disengage. Those are called "ACRs" (automatic connection relay, or automatic charge relay, depending on who you ask).
The original diagram shows how to hook up a "split-charge relay". Dumb, no brain, ignition controlled.
There are also smart split-charge relays on the market, which use a small computer brain to automatically engage/disengage. Those are called "ACRs" (automatic connection relay, or automatic charge relay, depending on who you ask).
utherjorge
Observer
Specifically, the blue sea controller that (I'm paraphrasing) didn't exist when the first post was started. I'd love to see something (from any course) that shows how that should be wired, because I'm looking at different sites, and I can't wrap my head around it like I could with that first post.
DiploStrat
Expedition Leader
Look here: https://diplostrat.org/documents/
An intelligent/voltage sensing/automatic relay costs more than a regular relay, but it is even easier to install, unless you add an override, in which case the wiring is about the same.
There are lots of good units on the market, I am most familiar with those by REDARC and Blue Sea
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I am really interested in this discussion, as I am considering a cap/ toppper on my 2015 F150 set up for sleeping. This would include a house battery (AGM for venting concerns?) in the bed to run some led lights, power ports for accessories and occasional electronics charging, and a CPAP (pressure only, not humidification, so the draw is much reduced). As far as I can tell, the simple ways to separate a house battery from the truck starting battery in a configuration like this would be:
Battery switch: Pros- simplicity of install, cheap way to have the truck alternator charge the house battery. Cons- have to remember to switch it back and forth each day, run the risk of either not charging the house battery or running down the starting battery if I don't remember.
Solenoid: Pros- cheap, automatic, install and forget (if I do it right!). Cons- a bit more complicated install, have to tap into the fuse box.
BtB charger: simple to wire like the battery switch option, automatic like the solenoid option. Cons- Cost (est. $200+ extra for CTEK charger?)
Intelligent Relay: simple to wire like the battery switch option, automatic like the solenoid option. Cons- Cost (est. $200+ extra for a Blue Sea Intelligent Relay?)
I am pretty new to 12v wiring, so correct me if I have any of this wrong. Any thoughts or advice? I have avoided solar as I want to keep the roof clear for racks. I did wire up a solar charging system for my travel trailer that worked great last summer.
Battery switch: Pros- simplicity of install, cheap way to have the truck alternator charge the house battery. Cons- have to remember to switch it back and forth each day, run the risk of either not charging the house battery or running down the starting battery if I don't remember.
Solenoid: Pros- cheap, automatic, install and forget (if I do it right!). Cons- a bit more complicated install, have to tap into the fuse box.
BtB charger: simple to wire like the battery switch option, automatic like the solenoid option. Cons- Cost (est. $200+ extra for CTEK charger?)
Intelligent Relay: simple to wire like the battery switch option, automatic like the solenoid option. Cons- Cost (est. $200+ extra for a Blue Sea Intelligent Relay?)
I am pretty new to 12v wiring, so correct me if I have any of this wrong. Any thoughts or advice? I have avoided solar as I want to keep the roof clear for racks. I did wire up a solar charging system for my travel trailer that worked great last summer.
DiploStrat
Expedition Leader
Not far off, but you missed the real question - voltage. It is the voltage of your vehicle's charging system, and the voltage requirements of your camper battery, that determines which system is best for you. That is, after you determine that you actually need an isolating system.
Good point, thanks.
My understanding is that an AGM battery will want an alternator that can output in the mid 14's, and that I need an AGM if I want to mount the battery in the sleeping compartment. I'm not sure what a '15 F150 alternator charges at, but it does have computer charging management (as mentioned much earlier in this thread) which will read the truck battery needs. Wouldn't this mean that the charging current will not necessarily stay in the range the AGM house battery needs? If that is the case, then maybe the BtB charger would be the most AGM-friendly way to charge- customized for the particular battery type?
As far as your second question, I guess I am just concerned that not having an isolating system would expose me to the possibility of a dead starting battery if I used too much at night. My needs aren't too heavy, but peace of mind would be preferred, no? I do have a jump pack, but I wouldn't want to rely on this too often.
My understanding is that an AGM battery will want an alternator that can output in the mid 14's, and that I need an AGM if I want to mount the battery in the sleeping compartment. I'm not sure what a '15 F150 alternator charges at, but it does have computer charging management (as mentioned much earlier in this thread) which will read the truck battery needs. Wouldn't this mean that the charging current will not necessarily stay in the range the AGM house battery needs? If that is the case, then maybe the BtB charger would be the most AGM-friendly way to charge- customized for the particular battery type?
As far as your second question, I guess I am just concerned that not having an isolating system would expose me to the possibility of a dead starting battery if I used too much at night. My needs aren't too heavy, but peace of mind would be preferred, no? I do have a jump pack, but I wouldn't want to rely on this too often.
DiploStrat
Expedition Leader
At the risk of being a bit pedantic ...
Measure the voltages and look at your starter battery - it may well be an AGM. Assuming properly sized cables, the charging system will read all of the batteries attached to it.
A dead starting battery is only a problem if your battery bank is too small. And if it is too small, you are going to be making paper weights. This may be completely reasonable if you assume a new battery every year or two.
The best reason to use an isolating system is so that you can mix a starting battery (skinny plates) with a deep cycle battery(s) (thick plates). In a small, jeep type vehicle, you may be better off using a pair of deep cycle batteries for starting and camping. Carry a small jump pack if you are worried.
Measure the voltages and look at your starter battery - it may well be an AGM. Assuming properly sized cables, the charging system will read all of the batteries attached to it.
A dead starting battery is only a problem if your battery bank is too small. And if it is too small, you are going to be making paper weights. This may be completely reasonable if you assume a new battery every year or two.
The best reason to use an isolating system is so that you can mix a starting battery (skinny plates) with a deep cycle battery(s) (thick plates). In a small, jeep type vehicle, you may be better off using a pair of deep cycle batteries for starting and camping. Carry a small jump pack if you are worried.
andrew61987
Observer
Anybody who's used any of the methods in this thread, did you run your 4 AWG wire from the vehicles alternator directly the solenoid? As the diagrams are drawn there is additional load (charging two batteries instead of one) on the factory wiring from alternator to the batts. Not sure if this wire needs to be beefed or if maybe the house battery needs it's own wire from the solenoid to the alternator instead of the starting battery.
dwh
Tail-End Charlie
Some people do replace the factory alternator wire (often #8 or even #10) with a bigger wire. That can help some if you've got big enough batteries to make it worth doing. It usually isn't necessary.
Even if you did, it wouldn't matter if you ran it to the starting battery or the solenoid - the load on the alternator/wiring would be the same either way.
dwh
Tail-End Charlie
Oh, and this assumption is somewhat incorrect:
The starter battery is never really much of a load on the so-called "charging system" unless something goes wrong. Starting the engine generally uses like 0.2 amp*hours (or less). Recharging that tiny amount doesn't load the alternator enough to notice.
Lots of heavy winching is of course a different story.
The starter battery is never really much of a load on the so-called "charging system" unless something goes wrong. Starting the engine generally uses like 0.2 amp*hours (or less). Recharging that tiny amount doesn't load the alternator enough to notice.
Lots of heavy winching is of course a different story.
I've got a dual battery set up with solar panels utilizing a BlueSea Ml-ACR 7622, thanks to this thread. I am adding a portable suitcase type panel to use when parked in the shade.
My plan is to add a second charge controller under the hood for the portable panel, connected to the vehicle battery. The ML-ACR 7622 should then connect to the house battery bank and charge both batteries when then portable is deployed.
Is my plan flawed? will there be any conflict with the other charge controller? Something else I've overlooked?( highly probable)
Gratitude to the OP and other knowledgeable contributors!
My plan is to add a second charge controller under the hood for the portable panel, connected to the vehicle battery. The ML-ACR 7622 should then connect to the house battery bank and charge both batteries when then portable is deployed.
Is my plan flawed? will there be any conflict with the other charge controller? Something else I've overlooked?( highly probable)
Gratitude to the OP and other knowledgeable contributors!
continuecrushing
Member
if I used the blue sea ml acr, could I get away with using 10awg if I was only using the 2nd battery to power a fridge? I don't care (currently, funds limited) about using the second battery to jump start the truck or anything large-it would only be for small items (fridge, small power inverter).
Obviously draw won't be an issue (since everything I'd be powering would be hooked directly to the 2nd battery), but charging could be?
The only reason I would be using small wire is I am still trying to work out where a larger battery could fit under the hood (as a 2nd battery) and I don't want to commit to running a 4awg wire to the back of the truck if I'll be switching the setup later down the road. If funds weren't an issue, I'd just run 4awg wire and drill a hole in the truck bed, but I can't do that right now.
So I guess my question is can I use 10awg to charge the 2nd battery if hooked up to a solenoid/blue sea ml acr?
Obviously draw won't be an issue (since everything I'd be powering would be hooked directly to the 2nd battery), but charging could be?
The only reason I would be using small wire is I am still trying to work out where a larger battery could fit under the hood (as a 2nd battery) and I don't want to commit to running a 4awg wire to the back of the truck if I'll be switching the setup later down the road. If funds weren't an issue, I'd just run 4awg wire and drill a hole in the truck bed, but I can't do that right now.
So I guess my question is can I use 10awg to charge the 2nd battery if hooked up to a solenoid/blue sea ml acr?