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

[mrthrun]

Well, I tested the voltage today and the batteries were sitting pretty at about 13.5v, as long as my $20 CAD B&D battery maintainer holds out I should be laughing. Good thing I bought two, the Coleman 20W charging system has my truck battery at about 11.5v, not to great.

 

[dlichterman]

So here is a question related to what everyone has been talking about - how much will two batteries "self drain" overnight?

I'm adding a second panel to my solar setup to be 200W total, and I was thinking about jumping across the solenoid with a small jumper to join the two batteries. Would they self drain a lot? What if I added a diode so current could only flow from the aux to the main battery?

 

[AndrewP]

1 one night, not much. Forget the diode, you don't need it. Jump across and hook up either side to the solar and forget about it. I'd use a 10ga wire just because, but assuming both batteries are charged when you start, there will be very little current in this wire. If you want to play it safe, put a fuse in the middle of the wire.

Or, you could just install a real VSR and forget about it.

 

[dlichterman]

1 one night, not much. Forget the diode, you don't need it. Jump across and hook up either side to the solar and forget about it. I'd use a 10ga wire just because, but assuming both batteries are charged when you start, there will be very little current in this wire. If you want to play it safe, put a fuse in the middle of the wire.

Or, you could just install a real VSR and forget about it.

Yeah, I was just looking for a cheap way to keep things topped up. I can pick up some aligator clips and make my own little jumper. The solar is always hooked up to the aux battery, and hopefully will be 200W after this weekend.

Just gotta work around business closures and hope I can get all the parts I need in the morning Thursday.

 

[XJINTX]

OK I'm a novice. I want to charge my camper batteries while driving off alternator. I already can charge from shore power and solar. Just adding a degree of additional charging while off grid charging from alternator.

I have looked at many posts and see different setups. I am installing a solenoid between the vehicle battery and camper. I will add a fuse between battery and each side of solenoid at vehicle and camper.

The question is what amperage will I need? I see some as low as 20 amp and I see some as high as 100 amp? I won't be powering anything just charging as camper will be separated by solenoid when stopped.

THANKS!!!

 

[AndrewP]

OK I'm a novice. I want to charge my camper batteries while driving off alternator. I already can charge from shore power and solar. Just adding a degree of additional charging while off grid charging from alternator.

I have looked at many posts and see different setups. I am installing a solenoid between the vehicle battery and camper. I will add a fuse between battery and each side of solenoid at vehicle and camper.

The question is what amperage will I need? I see some as low as 20 amp and I see some as high as 100 amp? I won't be powering anything just charging as camper will be separated by solenoid when stopped.

THANKS!!!

Place the fuses right next to the batteries. I have been using either ANL fuses or recently MRBF (marine rated battery fuse) which put the fuse right on the battery. Choose the fuse size based on the cable size you run to the camper batteries. If 2 ga 150amp, if 1 ga 175 amp, if 1/0 ga 200 amp. That's off the top of my head, so look it up on an ampacity chart.

The MRBF you can buy from Blue Sea (made by Bussman) or you can buy the Bussman version (which is the same) from Del City and save a few $$.

 

[XJINTX]

AndrewP, I think I'm missing something ?
I will run any gauge you recommend from my Jeep battery to the solenoid... with a fuse. Then from the other side of the solenoid I have to run back to my 7 blade trailer plug. Currently I have 14 gauge ran. Then I have the male side of the 7 blade ran to trailer lights and such. Now I want the trickle charge from that 7 blade plug to my dual battery setup. The trailer plug has (I believe) 16 gauge. I planed on attaching another 14 gauge short run to another fuse and then the battery.

Do I need heavier gauge and then do I need to make a separate run to the trailer battery and not use the 7 blade?

Thanks and I apologize for my string of questions

 

[bunce1260]

Hello.

So, I've got my battery isolator hooked up, and cables run to my aux. battery. Total length of wire is about 50ft (+ive and -ive). I've used the wire from the home depot jumper cables suggested at the beginning of this post, I had to buy 2 sets and connect a bit of extra to reach the battery. It all works but I'm worried the 80 amp fuses suggested may be too large. According to this wiring chart http://www.engineeringtoolbox.com/amps-wire-gauge-d_730.html for an 80 amp fuse at my wiring length I'd need a much bigger wire.

I guess what I need to know, or need to know how to calculate, what does the aux. battery pull in terms of amperage from the main batt./alternator when charging?

Once I know that, I can make sure my wire is big enough and what size fuse to use. According to the chart, I'll only be safe up to 25 amps.

 

[dlichterman]

Has anyone here used one of these InterVolt devices? I would like to be able to charge up both batteries from solar when my truck is sitting on the driveway and this seems like it might do just that...triggers from either side raising. I just wish it was easier to find out who the heck stocks these things....looks like they are an Australian company. I currently have the system set up like in the first post with a solenoid.

http://www.intervolt.com/product/voltage-sensing-relays/

 

[MINO]

Has anyone here used one of these InterVolt devices? I would like to be able to charge up both batteries from solar when my truck is sitting on the driveway and this seems like it might do just that...triggers from either side raising. I just wish it was easier to find out who the heck stocks these things....looks like they are an Australian company. I currently have the system set up like in the first post with a solenoid.

http://www.intervolt.com/product/voltage-sensing-relays/

Are you looking to charge or simply keep the starter batter topped-off?

I upgraded my solar controller to a Bluesky 3000i. It has a 2Amp aux battery output that triggers when it
determines that the camper battery doesn't need all the solar. On occasion, I would have starting issues after
my rig would sit for 3 weeks. Not anymore.

Not sure how much solar or draw you have, but it might be easier to get than the Intervolt.

 

[dlichterman]

Are you looking to charge or simply keep the starter batter topped-off?

I upgraded my solar controller to a Bluesky 3000i. It has a 2Amp aux battery output that triggers when it
determines that the camper battery doesn't need all the solar. On occasion, I would have starting issues after
my rig would sit for 3 weeks. Not anymore.

Not sure how much solar or draw you have, but it might be easier to get than the Intervolt.

I have 200W of solar mounted on the shell of my truck - and I'm looking to keep it topped up without having to think about it or get one of those little panels you set on the dashbaord. That looks like a great charge controller but the aux battery and solar is in the back of the truck so it makes the wiring a bit more complicated. I shot them an email to see about a US vendor.

I should consider a better charge controller too - using some cheap $20 PWM one from amazon right now.

 

[DiploStrat]

No Need to Import

Has anyone here used one of these InterVolt devices? I would like to be able to charge up both batteries from solar when my truck is sitting on the driveway and this seems like it might do just that...triggers from either side raising. I just wish it was easier to find out who the heck stocks these things....looks like they are an Australian company. I currently have the system set up like in the first post with a solenoid.

There are many similar products readily available in the US. I like Bluesea's ACR line, like these: https://www.bluesea.com/products/ca...age=12&Control_Circuit_Connection=Tinned_Wire

My truck actually has a Magnum Smart Battery Combiner (http://www.magnum-dimensions.com/sites/default/files/MagDocs/64-0019-ME-SBC-web.pdf) controlling a Bluesea relay.

You can also find products from Cole-Hersee and others.

 

[kins18q]

This thread is killer. I already made your awning, now working on this. So I am looking to run a 40L 12v fridge (Indel B or Dometic), some small interior LEDs, and laptop/camera batteries/phones for my photographer ladyfriend. I am trying to make sure I am getting everything I need. Here is what I have come up with from this thread:

100ah deep cycle sealed battery
400w Pure Sine inverter
100w solar panel
200amp isolator (so I can jumpstart)
10amp Chargel Controller
200amp fuses
15amp fuses
Wires
Connectors

Will a deep cycle battery be able to jump the starter battery or should I get a dual purpose?

Am I missing anything?

Are any of these things worth upgrading? Like a 500amp isolator or a 30amp charge controller?

 

[fiddypal]

Attached is a picture of my soon to be setup when wire comes in today.

0 Gauge wire for battery connections

12 gauge wire for stinger isolator trigger terminals

4 gauge wire for power into the cab

200 AMP Isolator - http://www.amazon.com/gp/product/B001HBYXVS?psc=1&redirect=true&ref_=oh_aui_detailpage_o08_s01

15 amp auto-reset fuse for Dometic fridge power (great so you dont need to carry replacements on the road) - http://www.amazon.com/gp/product/B00FRHS2BK?psc=1&redirect=true&ref_=oh_aui_detailpage_o02_s00

Battery Terminals (0/4/8AWG inputs) - http://www.amazon.com/gp/product/B00JK9FTLC?psc=1&redirect=true&ref_=oh_aui_detailpage_o04_s00

Power Dist. blocks for inside cab (4 awg in, 4x 8 awg out) - http://www.amazon.com/gp/product/B0071GKSL2?psc=1&redirect=true&ref_=oh_aui_detailpage_o04_s00

10 gauge disconnects for hard-wiring items - http://www.amazon.com/gp/product/B00HCRJUQ4?psc=1&redirect=true&ref_=oh_aui_detailpage_o03_s00

I am using this to power a Dometic 50 fridge in the cab and then will add an inverter later when i have more cash. I already have a 120VAC plug in my truck from factory so an inverter is a luxury item at this point.

Will add more pics later after installed.

 

[DiploStrat]

Since no one has replied to this, my two thoughts.

Will a deep cycle battery be able to jump the starter battery or should I get a dual purpose?

A deep cycle battery is fine for a starter battery; it will just have fewer amps for the same size/weight. On the other hand, it WILL survive the possible deep discharges that would quickly destroy a starter battery. I would recommend against a "dual purpose" battery; get the biggest deep cycle battery that you can fit.

Are any of these things worth upgrading?

Make sure that your wires are large enough to carry the load with minimal voltage drop.