Dual battery in-cabin and Solar setup

[rayra]

ok, some basic electrical. Electrical current generates heat in the wire. The more resistance - a defect in the wire, a bad or corroded connection, a wire sized too small - you get more heat. Too much heat, too much current flow for a given wire size, the wire gets very hot, your wire insulation melts and/or ignites, you have a fire or the now exposed wire shorts to something that shouldn't be energized and then things get exciting and expensive.
So first you determine the power draw / load of what you are trying / intending to energize. Then you look up the current rating for the wire size you hope or need to load. Always more up to the next greater wire size (smaller number, perversely) if you come anywhere close or even slightly exceed the rating of the smaller wire.
This is also a place where it doesn't hurt to add some 'buffer' in your power load estimate, akin to a tradesman buying 10% more of some material 'just in case of need'.
As an aside when sizing wire, especially for main runs to an added fuse panel etc, combine ALL the possible simultaneous loads to determine the gauge of your main supply wire to the added panel. Don't cheap out and say 'each of my 6 new circuits in the new panel are fused at 15A, so my main supply only needs to be that. Imagine ALL the things running at once, out of accident or ignorance, or inquisitive 5yr-old. So the main supply wire to that panel should be able to handle ALL the loads. That gives you a maximal safety margin.

Lastly, when it comes to fusing, once you've determined the max allowable power flow thru a given wire size, you fuse at a value LESS than that. That way you'll always melt the fuse (killing the power flow) before you can melt the wire (see above about things getting exciting and expensive).
The maxim / rubric about fusing as close to the power source as possible is about protecting the maximal length of that wire run against inadvertant physical damage to the run.

And on that, always consider the environment you are running wire in and protect the wire against crimping, shearing, crushing and abrasion. And the dreaded chaffing. Never trail a wire over a sharp edge. never leave a wire loose and moving around near an edge or surface that will abrade the insulation. Gaffer tape, 3m double stick, real / quality duct tape, mechanical hold downs. Use SOMETHING to constrain the wire and prevent it wearing thru against something else. And use the proper rubber grommets when putting a hole / wire thru some sheet metal or the like.

And always, if you have a question, ask it, you'll get lots of answers, some of them will even be educational and useful. And at least one of verkstad, dwh or (?) will (also) tell you it's all going to burn up.

 

[rustypayne]

Well for myself, I often run some handheld power tools off the 1000W inverter in the back, off the Aux battery. I also have plans to connect a towed camper trailer to this power setup. And I have future plans converting a toy hauler camper trailer into a mobile woodworking / carpentry shop, so this setup is a proof of concept for me. As well as the 12k winch setup I've long hand in mind. So I figured 'go big' and be able to power anything I care to try. Except those $1000 ARB fridges, I doubt I'll ever go for that extravagance.

You're talking theory and I'm talking how it performs in the real world. I don't have a driveway machine to entertain kiddos or power my workshop, I'm using it in a Jeep JKUR that's setup for overlanding. Longest trip was 42 days traveling across the country on the TransAmerica trail and not one time plugging into shore power. Wanted to do Alaska this summer but that's not happening. I'm overlanding with my wife, we kept 2 iPads, 4 iPhones, a laptop, dashcam, GPSr all charged while going down the road, with the CTEK isolating my house battery from the start battery 100% as much as a solenoid. In addition I have solar coming in anytime there is daylight whether I'm running the engine or not. If you're trying to power a tiny-home/workshop on wheels you'd be better off with a generator but I think that is an entirely different topic, you're comparing apples to a fruit cocktail. My Jeep sits for days at a time with the fridge running and has never even groaned at starting and the fridge is still cold.

Our Dometic CFX50 fridge is hands down the single best off grid purchase I've ever made to extend our time away from people when coupled with a capable off grid power system. Luxury is watching a DVD while using your power saw, I'd rather sit in the desert and pull out a cold beer.

 

[rayra]

You're talking theory and I'm talking how it performs in the real world. I don't have a driveway machine to entertain kiddos or power my workshop, I'm using it in a Jeep JKUR that's setup for overlanding. Longest trip was 42 days traveling across the country on the TransAmerica trail and not one time plugging into shore power. Wanted to do Alaska this summer but that's not happening. I'm overlanding with my wife, we kept 2 iPads, 4 iPhones, a laptop, dashcam, GPSr all charged while going down the road, with the CTEK isolating my house battery from the start battery 100% as much as a solenoid. In addition I have solar coming in anytime there is daylight whether I'm running the engine or not. If you're trying to power a tiny-home/workshop on wheels you'd be better off with a generator but I think that is an entirely different topic, you're comparing apples to a fruit cocktail. My Jeep sits for days at a time with the fridge running and has never even groaned at starting and the fridge is still cold.

Our Dometic CFX50 fridge is hands down the single best off grid purchase I've ever made to extend our time away from people when coupled with a capable off grid power system. Luxury is watching a DVD while using your power saw, I'd rather sit in the desert and pull out a cold beer.

ok, we're done, you can kiss my 'theory'.

 

[moose545]

You're talking theory and I'm talking how it performs in the real world. I don't have a driveway machine to entertain kiddos or power my workshop, I'm using it in a Jeep JKUR that's setup for overlanding. Longest trip was 42 days traveling across the country on the TransAmerica trail and not one time plugging into shore power. Wanted to do Alaska this summer but that's not happening. I'm overlanding with my wife, we kept 2 iPads, 4 iPhones, a laptop, dashcam, GPSr all charged while going down the road, with the CTEK isolating my house battery from the start battery 100% as much as a solenoid. In addition I have solar coming in anytime there is daylight whether I'm running the engine or not. If you're trying to power a tiny-home/workshop on wheels you'd be better off with a generator but I think that is an entirely different topic, you're comparing apples to a fruit cocktail. My Jeep sits for days at a time with the fridge running and has never even groaned at starting and the fridge is still cold.

Our Dometic CFX50 fridge is hands down the single best off grid purchase I've ever made to extend our time away from people when coupled with a capable off grid power system. Luxury is watching a DVD while using your power saw, I'd rather sit in the desert and pull out a cold beer.

Whats CTEK? How big and what type of panel are you using?

 

[moose545]

ok, some basic electrical. Electrical current generates heat in the wire. The more resistance - a defect in the wire, a bad or corroded connection, a wire sized too small - you get more heat. Too much heat, too much current flow for a given wire size, the wire gets very hot, your wire insulation melts and/or ignites, you have a fire or the now exposed wire shorts to something that shouldn't be energized and then things get exciting and expensive.
So first you determine the power draw / load of what you are trying / intending to energize. Then you look up the current rating for the wire size you hope or need to load. Always more up to the next greater wire size (smaller number, perversely) if you come anywhere close or even slightly exceed the rating of the smaller wire.
This is also a place where it doesn't hurt to add some 'buffer' in your power load estimate, akin to a tradesman buying 10% more of some material 'just in case of need'.
As an aside when sizing wire, especially for main runs to an added fuse panel etc, combine ALL the possible simultaneous loads to determine the gauge of your main supply wire to the added panel. Don't cheap out and say 'each of my 6 new circuits in the new panel are fused at 15A, so my main supply only needs to be that. Imagine ALL the things running at once, out of accident or ignorance, or inquisitive 5yr-old. So the main supply wire to that panel should be able to handle ALL the loads. That gives you a maximal safety margin.

Lastly, when it comes to fusing, once you've determined the max allowable power flow thru a given wire size, you fuse at a value LESS than that. That way you'll always melt the fuse (killing the power flow) before you can melt the wire (see above about things getting exciting and expensive).
The maxim / rubric about fusing as close to the power source as possible is about protecting the maximal length of that wire run against inadvertant physical damage to the run.

And on that, always consider the environment you are running wire in and protect the wire against crimping, shearing, crushing and abrasion. And the dreaded chaffing. Never trail a wire over a sharp edge. never leave a wire loose and moving around near an edge or surface that will abrade the insulation. Gaffer tape, 3m double stick, real / quality duct tape, mechanical hold downs. Use SOMETHING to constrain the wire and prevent it wearing thru against something else. And use the proper rubber grommets when putting a hole / wire thru some sheet metal or the like.

And always, if you have a question, ask it, you'll get lots of answers, some of them will even be educational and useful. And at least one of verkstad, dwh or (?) will (also) tell you it's all going to burn up.

Good info much appreciated, only part I have a question with is determining my draw, just take my draw in Ah or watts? So fridge and lights say, and add the draw up and then multiply by hours I plan to run, then just be sure not to exceed the max current available by the AUX battery? I will have a lot of room to grow into hopefully with this setup. Figuring out how fast a panel can recharge that battery is an entirely different thing, I know count on 50% of a panels rated wattage, and you’ll hardly ever get direct sun constantly to deliver a steady stream of power. I plan to go with a folding panel of some type, that way I can have it mobile and versatile, drape it off the side of the truck, or on a stand and move it around as needed

 

[rayra]

time only really comes in when sizing a battery or calculating run time to the rule of thumb of 50% depletion as a limit to prevent incurring permanent damage to a storage battery. How long your given devices can suck on a battery until you have to switch off or recharge the battery.

Amphours, Ah, is rate of power use over time. You want that when trying to figure out how long you put a load on a battery, or how long it takes to charge it back up off something like a solar panel etc.

One other thing re fridges and the like is cycle time, as in proper conditions the cooler device is off more often than it is on. That's a fuzzy number depending on all sorts of things, but generally it gets swept under the rug, any Ah number given being the average load over an hour. It can vary quite a bit in real use. So it isn't even accurate to say that the Ah use times 24hrs is your daily consumption. It ought to be less than that, 2/3 to 4/5 of that 24hr number. Ballpark.

Straight amp number, or if all you have is watts, divide the watts by the volt rating to get the amps. Look up Ohm's Law, it's a tiny bit of algebra for converting / deciphering amps / volts / watts. If say your vehicle's electric fridge runs on a notional 12VDC and consumes 200 watts in operation, you divide watts by volts and and get 16.66 Amps. call it 17A and also call it 17Ah. same-same Amps to Amphours, if that load is running for an hour.
So upsize your wire to accommodate a good bit over that, and fuse at 20A. Fuse at 15A and your fuse blows every time the fridge cooling mechanism triggers on.
So look up the manf data on your devices to find an A, Ah or watt rating and get your Amp numbers and start adding them up for either your individual circuit or the batch of circuits connected to an auxiliary fuse panel, when figuring out the branch line you are running from your battery to that added fuse panel.

Wire Size Chart

Wire Size Chart and current limits for wire gauges

wiresizecalculator.net

In the above example you'd run a 12ga wire and fuse at 20A. You could think you could 'get by' with a 14ga wire and still fuse at 20A. But there's things like ambient heat, accumulated heat, an unplanned surge, wire damage etc and you find out that your 14ga wire might slag before that 20A fuse pops.
So always err upwards in wire gauge, never shave that margin, and you shouldn't have any issues with the circuit wiring itself.

One more tidbit for folks to argue about, 'voltage drop'. It's insignificant in vehicle-length runs. Lot of people here go on and on about it. If you have a measurable drop of more than a couple % points when comparing voltage at your battery posts to voltage at the other end of your wiring run, something is wrong with your wiring job, its connections.
None of this stuff is exact, don't let somebody else's obsessive-compulsive disorder be inflicted upon you.

 

[rustypayne]

Whats CTEK? How big and what type of panel are you using?

CTEK is the mfg, it's a CTEK D250sa that I bought new on eBay for half the retail a couple years ago. It's a 20 amp DC-DC charger that has built in MMPT solar controller. I run a single 100 watt Renogy solar panel and a 100ah AGM house battery.

 

[john61ct]

They make great quality gear.

Not user-custom adjustable voltages though

 

[moose545]

time only really comes in when sizing a battery or calculating run time to the rule of thumb of 50% depletion as a limit to prevent incurring permanent damage to a storage battery. How long your given devices can suck on a battery until you have to switch off or recharge the battery.

Amphours, Ah, is rate of power use over time. You want that when trying to figure out how long you put a load on a battery, or how long it takes to charge it back up off something like a solar panel etc.

One other thing re fridges and the like is cycle time, as in proper conditions the cooler device is off more often than it is on. That's a fuzzy number depending on all sorts of things, but generally it gets swept under the rug, any Ah number given being the average load over an hour. It can vary quite a bit in real use. So it isn't even accurate to say that the Ah use times 24hrs is your daily consumption. It ought to be less than that, 2/3 to 4/5 of that 24hr number. Ballpark.

Straight amp number, or if all you have is watts, divide the watts by the volt rating to get the amps. Look up Ohm's Law, it's a tiny bit of algebra for converting / deciphering amps / volts / watts. If say your vehicle's electric fridge runs on a notional 12VDC and consumes 200 watts in operation, you divide watts by volts and and get 16.66 Amps. call it 17A and also call it 17Ah. same-same Amps to Amphours, if that load is running for an hour.
So upsize your wire to accommodate a good bit over that, and fuse at 20A. Fuse at 15A and your fuse blows every time the fridge cooling mechanism triggers on.
So look up the manf data on your devices to find an A, Ah or watt rating and get your Amp numbers and start adding them up for either your individual circuit or the batch of circuits connected to an auxiliary fuse panel, when figuring out the branch line you are running from your battery to that added fuse panel.

Wire Size Chart

Wire Size Chart and current limits for wire gauges

wiresizecalculator.net

In the above example you'd run a 12ga wire and fuse at 20A. You could think you could 'get by' with a 14ga wire and still fuse at 20A. But there's things like ambient heat, accumulated heat, an unplanned surge, wire damage etc and you find out that your 14ga wire might slag before that 20A fuse pops.
So always err upwards in wire gauge, never shave that margin, and you shouldn't have any issues with the circuit wiring itself.

One more tidbit for folks to argue about, 'voltage drop'. It's insignificant in vehicle-length runs. Lot of people here go on and on about it. If you have a measurable drop of more than a couple % points when comparing voltage at your battery posts to voltage at the other end of your wiring run, something is wrong with your wiring job, its connections.
None of this stuff is exact, don't let somebody else's obsessive-compulsive disorder be inflicted upon you.

Awesome thanks, this is my fridge, all that I've got planned for now not counting lights which I haven't decided on yet:

• Voltage Supply: 12/ 24 // 100-240V
• Average Power Consumption: 40 Watt
• Current Draw on 12V: approx. 0.7 Ah/h
• Battery Protection: 3 stage low voltage protection (Low 10.2V, Med 10.7V, High 11.7V)

IceCube Fridge/Freezer 50L (52 Quarts)

Ironman 4x4 America offers off-road parts, accessories, and equipment for the off-roading enthusiast. Check out our website for more information.

ironman4x4america.com

I should have plenty left over to add some things with the battery I plan to use and the solar, the quality of the panel I get matters too understandably.

 

[rayra]

• Average Power Consumption: 40 Watt
• Current Draw on 12V: approx. 0.7 Ah/h

hmm, those numbers don't match up very well. 12v at .7A is 8.4watts. But they state an average consumption of 40watts, which is 5x higher. I'd go with the higher stated consumption value, the 40W, which is ~3.5A at 12v. Even then that's still far below the rated capacity of any 12-18ga wire. Just be sure to fuse both below the slag point of your wire AND whatever protection level your device might require.

Consider too the idea of 'future proofing', if you are making a long wiring run from front to back of a vehicle consider using a fatter lead for what is in essence a branch circuit, so you might in the future switch the line to a aux fuse panel and power other devices too. If you have to do a bunch of crawling around and interior trim and carpet disruption to route the wiring, you might as well go larger on the wire while you are at it, with possible future expansion in mind, so you don't have to do the work twice.

That's where I wound up with my ludicrous wiring projects. I wanted heavy winching at the back bumper, so my run was a pair of huge 1/0 cables from my under-hood Aux to my back cargo area. That became basically a 200A electrical trunk / backbone for a lot of other power options in the back and it was ~2yrs before I actually completed the final 1/0 power extensions to both my rear bumper and front grill. Just completed that work in the last few weeks. in the intervening years I added all sorts of power ports and charging ports, a 1000W inverter, rooftop solar and PWM controller (which basically backfeeds the Aux thru that ~20' of heavy cable). Then I went even further, reached even further, modifying a new 20' set of true copper fine-strand 4ga jumper cables with a set of anderson plugs near one end, such that I could plug the 18.5' portion in at either bumper, into that 200A bus. Took no time at all to pass enough juice to crank over that dead pickup.

In recent months I've got all my winch accessories, the hitch mounted winch carrier, front hitch, hawse plate, some fancier allen socket truss head bolts for the carrier assembly, 100' of dyneema / synth rope, the saddle clamps to convert the steel winch cable into a 65' cable extension, I've long had all the hooks, shackles, 30k# tow strap, tree strap. I've even got the Anderson plug, lugs and boot sitting around to convert the winch cabling to plug in.
The only thing I DON'T have after all these project years is the actual damned winch. And now the missus and I are both covid-unemployed. So no winch buying right now.

 

[moose545]

• Average Power Consumption: 40 Watt
• Current Draw on 12V: approx. 0.7 Ah/h

hmm, those numbers don't match up very well. 12v at .7A is 8.4watts. But they state an average consumption of 40watts, which is 5x higher. I'd go with the higher stated consumption value, the 40W, which is ~3.5A at 12v. Even then that's still far below the rated capacity of any 12-18ga wire. Just be sure to fuse both below the slag point of your wire AND whatever protection level your device might require.

Consider too the idea of 'future proofing', if you are making a long wiring run from front to back of a vehicle consider using a fatter lead for what is in essence a branch circuit, so you might in the future switch the line to a aux fuse panel and power other devices too. If you have to do a bunch of crawling around and interior trim and carpet disruption to route the wiring, you might as well go larger on the wire while you are at it, with possible future expansion in mind, so you don't have to do the work twice.

That's where I wound up with my ludicrous wiring projects. I wanted heavy winching at the back bumper, so my run was a pair of huge 1/0 cables from my under-hood Aux to my back cargo area. That became basically a 200A electrical trunk / backbone for a lot of other power options in the back and it was ~2yrs before I actually completed the final 1/0 power extensions to both my rear bumper and front grill. Just completed that work in the last few weeks. in the intervening years I added all sorts of power ports and charging ports, a 1000W inverter, rooftop solar and PWM controller (which basically backfeeds the Aux thru that ~20' of heavy cable). Then I went even further, reached even further, modifying a new 20' set of true copper fine-strand 4ga jumper cables with a set of anderson plugs near one end, such that I could plug the 18.5' portion in at either bumper, into that 200A bus. Took no time at all to pass enough juice to crank over that dead pickup.

In recent months I've got all my winch accessories, the hitch mounted winch carrier, front hitch, hawse plate, some fancier allen socket truss head bolts for the carrier assembly, 100' of dyneema / synth rope, the saddle clamps to convert the steel winch cable into a 65' cable extension, I've long had all the hooks, shackles, 30k# tow strap, tree strap. I've even got the Anderson plug, lugs and boot sitting around to convert the winch cabling to plug in.
The only thing I DON'T have after all these project years is the actual damned winch. And now the missus and I are both covid-unemployed. So no winch buying right now.

That's a nice setup and sorry to hear about the joblosses, that's a challenge and frustrating in itself, I've been down that road too many times. The winch will come your way soon don't worry, I put a Superwinch TigerShark 11.5 on my GX, the price was great and unbeatable compared to anything else. As for my solar/battery setup, I think 2AWG might be overkill from the main battery back to the AUX, so I'm thinking 4AWG will be sufficient. I haven't looked at lights but all are LED which don't consume very much in the grand scheme. An inverter would be nice possibly, or maybe some sort of heater for a water tank at some point, but I haven't searched around much on that, and if it's summer and the tank is on the roof in July, in a black container, in the SouthWest I think the water would stay fairly warm as it is! But, I also know that once I start hooking things up stuff will add up too. Maybe I should pick a few lights and see what the average consumption looks like, and just build in a number to see where I sit with the things I plan to have alone, and see what room to grow I'll be working with.

 

[moose545]

Those numbers seem low.
If running at 12V, 40W is 3.3A.
That seems low compared to most guys report their various ’fridges operate at.
So just for fun we make believe it runs 3.3A . To get a .7Ah/h value, that fridge would only run about 5min each hour.
It seems unrealistic, only possible if the fridge is tested in a cold environment.

Yeah it seems low, I'll definitely assume a higher consumption.

 

[john61ct]

An **average** of 3.3Ah per hour, that's more believable, very much at the high end for portable units in fact implies a high temperature delta.

In moderate conditions many such fridges have a duty cycle well under 30%, but yes 8% implies an unusually low delta

 

[67cj5]

Yeah it seems low, I'll definitely assume a higher consumption.

In temps around 60*f you should find that your fridge will only use around 0.25Ah to 0.35Ah per hour when set to about 35-37*f.

 

[moose545]

In temps around 60*f you should find that your fridge will only use around 0.25Ah to 0.35Ah per hour when set to about 35-37*f.

Yeah the settings aren't the most easiest in the world to believe honestly. I ordered the remote thermostat with it, only to find out it can't be changed from Celcius, so that was a waste but lesson learned. I'll try a different fridge next time, hopefully I get many years from this guy though.