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

AndrewP

Explorer
You can easily do all of this yourself.

Just to keep terminology straight-what you are calling an isolator is really a relay. Isolator implies the diode based isolators that are basically junk and should not be used due to the voltage drop they cause.

Voltage sensing relays are easier to install than the PAC unit you show. I really don't know Samplex as they are a new name in the USA, but BLUE Sea makes several great voltage sensing relays (they call them Automatic Charging relays) and they work great and have a lifetime warranty. I like the 120 amp size because it's enough for most applications and seriously take 3 wires to hook it up-2 power leads and a small ground.

Bussman makes good circuit breakers-you need to decide what size wire cable you want to run, and then protect the cable with an appropriate fuse. Blue Sea also sells a waterproof version of the Bussman breakers. I might suggest 2ga wire protected with a 150 amp breaker or fuse. If you are planning for your battery box to be in the back, you need to be very careful about wiring where it crosses the firewall since that's a common chafe point. Assuming your relay is under the hood, you're going to need to put fuses or breakers right at each battery

Your big ARB fridge is going to use a lot of power-I'm estimating 40-50 amp hours per day depending on temperature. So for that kind of load you're looking at a 100 amp hour battery, since cycling a deep cycle battery should not go below 50% capacity if you want it to live a long time. Nothing wrong with flooded lead acid batteries. They are significantly cheaper, just get one big enough to meet your proposed needs.

Regarding solar, if you are not doing that now, just do it later as a separate project and worry about the connections then.

The larger ARB fridges don't always play well with cigarette type plugs. Strongly consider either directly wiring, or using a better connector like Anderson Power Poles. Actually, I hate cigarette type plugs as they are unreliable and there are much better options.

Without knowing what tools you have, it's hard to know what to recommend. Good wire cutters, a wire stripper a crimper, a heat gun for heat shrink. How are you going to mount your battery box? You don't want a 75 pound missile inside the truck in the event of an accident.
 

dlichterman

Explorer
What gauge wire should I use and where should I get it? I have no idea how to connect the first red wire to the battery. Can someone send links to eBay or Amazon for the correct parts?
Whatever gauge of wire you pick(I did 4awg) you then want to search for copper lugs like this: http://amzn.com/B000NI1FNK. You'll need to figure out what size the hole needs to be based on your battery terminals.


Can someone suggest automotive circuit breakers? I figure it's probably easier in the long run rather than carrying spare fuses that get lost.
Blue sea makes some circuit breakers: http://amzn.com/B0051P01BW but I just went with 200A fuses. Lets me self jump, but if something goes seriously wrong and shorts out, it should blow.


I want to connect the RV battery to an RV battery box with four 12 volt plugs and a quick connect for future solar. Should I drill holes and add the 12 volt plug or buy a box with all the outlets? I am looking at QuickBox sold on Amazon.
I did not like any of the plastic boxes, so I started looking for a metal one and ended up going with one from JEGS: http://www.jegs.com/i/JEGS+Performance+Products/555/10282/10002/-1?CAWELAID=1710768453&CAGPSPN=pla&catargetid=230006180000848229&cadevice=c&gclid=CjwKEAjwtMqrBRDwtoehx72vm34SJACl_Un1N0pfZGMGsRRI0UNT0abN2BFdA3PSsr8G3tAcH1_p6BoCHNXw_wcB. As for power distribution I quite like the blu sea fuse blocks.

If I can do this all myself, I may as well add solar. Anyone suggest a budget friendly 80-100W solar panel and charge controller that can plug right into the battery box via quick connect?
The quick connects are really whatever quick connects you pick - with 100W you could use the 30A anderson power poles. I have this renogy 100W panel and this solar charge controller. All you need to do is run wires from the panel to the charge controller and then from the controller to the battery. I'm sure you can figure something out for making it quick disconnect with powerpoles.


Oh, one final note-I have an old electrical wire repair kit from 1985. What tools should I buy? I want to do everything solderless.
Every time this is asked I always point to the harbor freight hydraulic crimper - it really makes doing the large gauge stuff better.
http://www.harborfreight.com/hydraulic-wire-crimping-tool-66150.html
 

coolfeet

Mark Keeler

dwh

Tail-End Charlie
It cost 2x the price of a flooded lead acid battery. I am hopeful that it will last longer.

Hope is good. Keep hoping. Don't hold your breath.


What gauge wire should I use and where should I get it?

4 gauge jumper cables. Buy a set that is long enough, cut the ends off and put on crimp terminals with the right size holes to fit the bolts on the ACR and the battery.


DWH here on the Expedition Portal suggested the Samplex ACR. The local stereo shop installs PAC isolator for $90/hour. I found it for PAC for $38 on Amazon. Stereo shop charges $85. They want $400 for the install.

The PAC is just a dumb solenoid - no voltage sensing brain. The Samlex (no "p" in there) has a brain and operates automatically. The smaller 120a Blue Sea ACR operates automatically, but does not have the option to rig a manual override switch - the Samlex does have that option, and is also rated higher. The Samlex is also fully potted and waterproof.


DWH says I can easily do it myself.

Did I say that, or just think it?


fear-and-loathing.jpg







Can someone suggest automotive circuit breakers? I figure it's probably easier in the long run rather than carrying spare fuses that get lost.

Big ones or little ones? I use Bussman ShortStop for stuff up to 50 amps. You can find them at an auto parts store for like 5 bucks each.

https://www.google.com/search?q=bussman+shortstop+breakers&ie=utf-8&oe=utf-8


I want to connect the RV battery to an RV battery box with four 12 volt plugs and a quick connect for future solar. Should I drill holes and add the 12 volt plug or buy a box with all the outlets? I am looking at QuickBox sold on Amazon.

Whatever floats yer boat.


If I can do this all myself, I may as well add solar. Anyone suggest a budget friendly 80-100W solar panel and charge controller that can plug right into the battery box via quick connect?

Quite a few folks around here seem to like the Renogy kits. Won't have a quick connect, you'll have to rig that yourself.


Oh, one final note-I have an old electrical wire repair kit from 1985. What tools should I buy? I want to do everything solderless.

For smaller stuff (normal, not battery cables), I use a Klein 1010 (you can probably find it at Home Depot) and just buy packets of whatever crimps terminals I need.:

http://www.amazon.com/Klein-Tools-1010-Long-Nose-Multi-Purpose/dp/B0000302WX

Klein is the brand real electricians use. Lifetime guarantee (any electrical supply house will swap them out for you if you break it and need a replacement).


I want to thank everyone in advance especially DWH.

No worries.
 

coolfeet

Mark Keeler
Hope is good. Keep hoping. Don't hold your breath.


4 gauge jumper cables. Buy a set that is long enough, cut the ends off and put on crimp terminals with the right size holes to fit the bolts on the ACR and the battery.

The PAC is just a dumb solenoid - no voltage sensing brain. The Samlex (no "p" in there) has a brain and operates automatically. The smaller 120a Blue Sea ACR operates automatically, but does not have the option to rig a manual override switch - the Samlex does have that option, and is also rated higher. The Samlex is also fully potted and waterproof.




Did I say that, or just think it?


fear-and-loathing.jpg






Big ones or little ones? I use Bussman ShortStop for stuff up to 50 amps. You can find them at an auto parts store for like 5 bucks each.

https://www.google.com/search?q=bussman+shortstop+breakers&ie=utf-8&oe=utf-8


Quite a few folks around here seem to like the Renogy kits. Won't have a quick connect, you'll have to rig that yourself.


For smaller stuff (normal, not battery cables), I use a Klein 1010 (you can probably find it at Home Depot) and just buy packets of whatever crimps terminals I need.:

http://www.amazon.com/Klein-Tools-1010-Long-Nose-Multi-Purpose/dp/B0000302WX

Klein is the brand real electricians use. Lifetime guarantee (any electrical supply house will swap them out for you if you break it and need a replacement).




No worries.
Great advice!

I ordered a cheap battery box from Napa for $10.95. It has a divider that will allow me to drop in 12 volt cigarette outlets and maybe an invertor.

308102-001-2.jpg


LIfe Line Battery $260 delivered. I wanted a sealed battery. I found some decent Chinese batteries for less money. The shipping cost was the deciding factor. For an extra $50, I bought an American made battery (probably Chinese parts).

68755-lifeline-lfl-GPL-24T-it1

I found a True dual battery isolator kit for $129 with American made 100% copper welding cables. It has 20' of 8 awg red cable. I need a long cable to go under the Ford E150 van.

What amp fuses do I need between each battery and the isolator?

The Samlex looks great too. I want a kit to make everything easy. You mentioned cutting 4 awg battery cables. That's an option if I can find high quality copper cables. Most of the jumper cables that I see on Amazon or O'reilly's look like junk. Lowes and Home Depot sell bulk copper coduit wire. Can I use the Lowes/HomeDepot wire?

TrueLargeDualBatteryKit.jpg


I found this linesman pliers at Harbor Freight. Looks like it will be burly enough cut and crimp wires.



The Klein wire 1010 tool is going into the tool box.

31YPC7H3FJL.jpg


I cannot beat the $5 price tag for Bussman circuit breakers.
Hope I can find free shipping as this unit is about $4.
105.jpeg


Amazon has nice 100 w Renology solar panels for under $200. I heard Renology charge controllers are not efficient.

Things are coming together. I am installing everything this weekend.


Thanks again for all the help. It beats paying $90 an hour.
 
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coolfeet

Mark Keeler
As for using "Home Depot/Lowes wire" previously shown,,(Type THHN)
I will work ok, but its not really optimal for vehicular uses.
Without going on to great detail of how & why wire is constructed for its various purposes.
Vehicular wire will be stranded finer & may have a higher temperature rating.
But with good care taken with its mechanical installation, dont be crazy running it near max ampacity or placing near hot components, it will work out fine.

I found welding cable on eBay. It says it's made for welders and battery cables. My friend is vp of engineering at an industrial power supply in Fremont, Ca. Temco sells 4 awg copper welding cable for a fair price. I asked to buy 20 feet from him. I think ebays sells Temco 6 awg welding wire for about $1.15 a foot. This is not an advert for his company. I am trying to score a deal and buy direct or ask for a scrap. Last week he made some custom bed legs for our folding bed in the van. He used 1 1/2 conduit pipe and TIG welded the conduit connectors to some scrap metal. Nothing beats free and cheap!
 

dwh

Tail-End Charlie
The True Dual kit is just okay. The red wire is long, the black isn't, so you'll have to ground the second battery to the frame near the second battery. That'll work, but isn't really optimal. It can lead to noise in radios. If that is not an issue then it will work. The dual sensing solenoid is good, so it works automatically, which is simple, but has no option for a manual override switch.

It also does not appear to include a fuse for the hot wire. If everything is under the hood, I don't worry about a fuse in the battery cable. For a long run though, I would absolutely have a fuse. If that wire is actually #8, then a 40a Bussman Shortstop would cover it. Put one at each end (both batteries can potentially supply power to the wire if there is a short somewhere, so you have to protect the wire with a fuse at each power source).

The only gotcha is that the terminals on the big wire won't be the right size to fit the screws on the ShortStop. But that kit comes with some extra terminals, because you have to cut the red wire to fit, so it has one terminal on it already, and you have to put the others on (two at the isolator, one at the secondary battery). So you just use different terminals that fit the ShortStop. You would need one short wire engine battery to breaker, then one wire breaker to solenoid, then solenoid to aux battery breaker, and a short one from aux battery breaker to aux battery.




The Renogy kits I think usually come with a PWM charge controller. PWM works fine. MPPT is better, but usually not worth the extra cost if you have less than 200w of solar.
 

coolfeet

Mark Keeler
The True Dual kit is just okay. The red wire is long, the black isn't, so you'll have to ground the second battery to the frame near the second battery. That'll work, but isn't really optimal. It can lead to noise in radios. If that is not an issue then it will work. The dual sensing solenoid is good, so it works automatically, which is simple, but has no option for a manual override switch..
I don't want noise coming back to my sound system. Where should I ground the second battery? I drive an E150 Ford van and the second battery is going all the way to the rear.

Any better dual battery isolator kits? Whether the kit is $85 or $150, I would rather have an isolator kit that works great. I have the battery and the box ready to go. I need cable, circuit breakers, and the isolator.

When I wire the 12 volt cigarette outlets to the battery, what gauge wire should I use and what amp circuit breaker. ARB said to go with 15 amp for the 63 quart fridge/freezer.

I am enjoying the learning process. Last weekend I installed the new stereo system and I think this will be easier. Less connections!
 

dlichterman

Explorer
I don't want noise coming back to my sound system. Where should I ground the second battery? I drive an E150 Ford van and the second battery is going all the way to the rear.

Any better dual battery isolator kits? Whether the kit is $85 or $150, I would rather have an isolator kit that works great. I have the battery and the box ready to go. I need cable, circuit breakers, and the isolator.

When I wire the 12 volt cigarette outlets to the battery, what gauge wire should I use and what amp circuit breaker. ARB said to go with 15 amp for the 63 quart fridge/freezer.

I am enjoying the learning process. Last weekend I installed the new stereo system and I think this will be easier. Less connections!

Are you looking for a fully automated isolator, or do you just want a basic system like in the first post? I added a time delay relay so the batteries join after 10 minutes, giving the alternator a chance to charge up the starting battery first. If you don't want ground loops, you'll need to run both positive and negative lines to the new battery.
 

dwh

Tail-End Charlie
I don't want noise coming back to my sound system. Where should I ground the second battery?

At the first battery. That's why I suggested just butchering up a set of jumper cables - they are a matched set of positive and negative, are very flexible and usually have a fairly tough insulation.

To prevent induction, which can contribute to radio noise, it's best to run conductors as matched sets and run them together right next to each other. The more space between the positive and the negative, the greater the chance of induction.

You could still use that kit and just buy a 20' piece of black #8 (if #8 is actually what is included in the kit) to run the ground all the way back to the first battery.


Any better dual battery isolator kits? Whether the kit is $85 or $150, I would rather have an isolator kit that works great. I have the battery and the box ready to go. I need cable, circuit breakers, and the isolator.

No idea about better kits. I'm not the sort who'd buy one, so I've never looked.


When I wire the 12 volt cigarette outlets to the battery, what gauge wire should I use and what amp circuit breaker. ARB said to go with 15 amp for the 63 quart fridge/freezer.

For short runs you can use #14 wire. Most lighter plugs are rated 10a so except for the fridge, I'd use 10a breakers for the lighter sockets.
 

coolfeet

Mark Keeler
I settled on the ctek d250s as its a dc to dc charger, isolator, and solar charge controller.


Sent from my iPhone using Tapatalk
 

Bintang

New member
Ok, so I wired up a house battery as per instructions.

Before I connected the positive cable from the solenoid to the truck battery I checked the continuity (ignition off) across the solenoid and it was open (as it should be). When I connect to the truck battery I get continuity across the solenoid (ignition off). Doesn't seem right or is it?
 

dwh

Tail-End Charlie
Ok, so I wired up a house battery as per instructions.

Before I connected the positive cable from the solenoid to the truck battery I checked the continuity (ignition off) across the solenoid and it was open (as it should be). When I connect to the truck battery I get continuity across the solenoid (ignition off). Doesn't seem right or is it?

That's correct. Continuity runs through the wire from solenoid to Battery A, through Battery A to ground, through ground to Battery B, through Battery B and back to the other side of the solenoid.

"Backdoor Continuity."
 

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