Solar power and isolators

[onelif2live85]

Heys long time reader, first post.

So its a little different than a trailer bit same concept. Ive built out the rear of my truck with a topper. I've got 360ah 6v battery bank a 100 watt solar panel. I currently run some led interipr lights a dometic cfx35 have a small tv, hardly ever used unless the lods are around :/ a maxxair vent fan and a small 10" camp fan. Plan on adding a water pump and a possibly a small inverter. The invertor will probably never be used as I've been able to plan and everything thus far is all 12v dc.

So the issue, i live in sunny Florida and on yhe sunniest of days im good come 3 o'clock. But that seems to be rare. Last night i woke up to my fan on but my fridge had shut down. I cant seem to get ahead. So i want to add another panel, but am worried it may still not be enough. Should i also do an isloator? I dont drove much so not sure how much that will do for me. Though about also adding an actual battery charger for bad weeks i could plug in at work, but the fridge says not to operate of plugged into a charger.

Thanks for taking the time to read my post, hope someone can settle this for me before i ruin my batteries!

Thanks In Advance



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[flboy]

Rule of thumb on solar to aH on the batteries is 1 to 1. Approximately 1w of solar for each 1ah of battery capacity. I think another panel would help alot, then if you are driving each day, why not put the isolater in and have your truck alternator assist. It is good to have the options in any case.

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[onelif2live85]

Rule of thumb on solar to aH on the batteries is 1 to 1. Approximately 1w of solar for each 1ah of battery capacity. I think another panel would help alot, then if you are driving each day, why not put the isolater in and have your truck alternator assist. It is good to have the options in any case.

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Ok, I will also upgrade to a mppt charge controller. My question to that is wiring. There seems to be a million different scenarios on how to wire it up.

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[flboy]

If you are refering to adding another panel, they sell 2 into 1 "Y " adapters for those MC4 connectors.

An isolation switch should come with instructions. I'd recommend you follow them. If they dont make sense to you , maybe we can help clarify.

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[flboy]

Btw.. I think they mean don't use a charger to run your fridge without a battery. If the fridge is plugged into the battery and the charger is on charging the battery , there should be no problem. That is a very typical scenario. A charger would solve your problem if you can plug in at work.

What exactly does the fridge manual say about the charger?

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[defjr333]

Totally agree with Flboy. Every RV I have ever seen that has a DC operated Fridge works just fine when batteries are on charge. Sounds like the manufacturer just doesnt want to be run directly off a charger. IMHO
Doug

[flboy]

oneliftolive85.. on that rule of thumb of 1 to 1 i mentioned and before others get worked up.. know that there are so many variables such as amount of daily sunlight, draw down on batteries, and etc.. when it comes to customizing a solar power system and matching the solar panels to the battery capacity to meet your needs so the batteries never get below 50%... One to one gets you somewhere to start and build on.

When it comes to solar... more is usually better... but to explain in a way most folks without the background will understand.... the batteries are your gas tank and the solar panels are the gas pump. The more panels the faster you can fill the tank up. The less, the slower. All your appliances running determine the miles per gallon you get from your tank and the more appliances you run, the more gas you use. The trick is to find the balance where you never use more than 50% of your gas tank and that the fuel pump can run fast enough to fill the tank while the engine is running, knowing that the pump does not run all day and you need to end with a relatively full tank before the pump is turned off for at least 12 hours. Sounds confusing... try working out all the math knowing that some variables are in fact variable. Alright.. now I am confusing myself.

In any case... best of luck! Are you living in your truck fulltime?

[bc toys]

flboy if I get a frig said 5amp and I have 350ah x 2 6v batteries will 520watts of solar run it ok

[flboy]

Your fridge running 24 hours, which is unlikely because it cycles, would be 120ah. Your solar panels assumimg full sun and efficiency over a 12 hour period should produce 520ah so just taking 50% of that (260aH) you are more than covered. Your batteries in series gives you 12v at 350ah so given you can use 175aH without killing your battery bank and assuming your fridge only is on 1/2 the time or 12 hours or 60ah, you should be able to run it for 3 days on a full charge before you need to recharge.

Short answer: yes. :-)

Btw.. I have 500W with 345aH of batteries and a similar spec'd fridge running via an inverter. It will run indefinitely with a few good hours of sun each day. It only cycles on maybe 15 minutes out of each hour at most.

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[bc toys]

thanks Don Flboy

[RixPlace1]

I have 4-100W panels and 4 105AH AGM batts planned. Trailer to have 5-7 LED interior lites,mini fridge,water heater, water pump for shower supply,m'wave,5000BTU A/C,induction cooktop,all these are 110,15 amp .Very conservative with electric useage.Now the ?.Talked with knowledgeable(?) person at batt store said I have nowhere near enuf panels to produce what I require..YES,NO or Maybe??? Don't need a definitive answer, shade tree will work.Almost redy to call Goodwill store to donate trailer and take the deduction, interior about 70% finished

[flboy]

I have 4-100W panels and 4 105AH AGM batts planned. Trailer to have 5-7 LED interior lites,mini fridge,water heater, water pump for shower supply,m'wave,5000BTU A/C,induction cooktop,all these are 110,15 amp .Very conservative with electric useage.Now the ?.Talked with knowledgeable(?) person at batt store said I have nowhere near enuf panels to produce what I require..YES,NO or Maybe??? Don't need a definitive answer, shade tree will work.Almost redy to call Goodwill store to donate trailer and take the deduction, interior about 70% finished

I am confused... what are you planning to run off the batteries and solar panels..

[Mark959]

Is the refrigerator based on a peltier system(no compressor)? These are POWER HOGS if so.

I am using a cheap 120vac fridge with the inverter , together uses about 700w a day - might get something more efficient. There are danfoss 12vdc compressors, but the cheapest fridge built with one is like 800$. And i can't find the compressor alone for under 250, or I would evac&solder it up myself.


MPPT controllers can usually take different voltages, its better to up the voltage than the amperage when it comes to transferring over the wiring. Amps = heat. In my case I am running the panels in series (24v although they really put out more than that), and the controller turns that down to 12v for the bank.

I have 200W of panels, and enough battery capacity for 1.5 days without power. I am building a mount that I can angle towards the sun so hopefully I can get a good solid 4 hours of light. If not I will add another panel or two as needed. Otherwise yes, the more you run on 12vdc instead of 120vac the better.

[dancam]

I have 4-100W panels and 4 105AH AGM batts planned. Trailer to have 5-7 LED interior lites,mini fridge,water heater, water pump for shower supply,m'wave,5000BTU A/C,induction cooktop,all these are 110,15 amp .Very conservative with electric useage.Now the ?.Talked with knowledgeable(?) person at batt store said I have nowhere near enuf panels to produce what I require..YES,NO or Maybe??? Don't need a definitive answer, shade tree will work.Almost redy to call Goodwill store to donate trailer and take the deduction, interior about 70% finished

Tell us the power usage of each item that is printed on it and how many minutes or hours per day you think each would be used. Also what type of fridge is it?
Then we can help you figure out if it will work. If your conservative like you say with power usage it should be ok.

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[John61CT]

Don't even think about running the A/C off your batteries.

Actually run your proposed devices over a few hours measuring average amp hours consumed and report back.