Solar/Battery Help

Jdavenport

New member
Hello, I'm reaching out to help me understand what its going to take to give me the power off the grid that I'm looking for. I intend on doing a solar/battery bank set-up but with absolutely no experience, and being awful with electronics I'd like some professional help. I've looked around at some other threads but I just can't seem to comprehend what they say. That being said I'm converting the bed of my pickup into a mini RV type/Van setup and looking to be able to run small appliances such as a toaster oven, charge my phone and laptop, and potentially an ARB fridge without having to worry about running out of battery for 2-5 days typically. I plan on keeping it separate from the starter battery and unsure if I should hook it up the alternator or not. Is it possible to make a campground plug in as well for the few times I find myself with a hookup option. How many batteries do I need, is more better or pointless? Recommendations for solar panels, inverters? How much should I expect to pay for this? I'm truly lost at this subject and I can't continue my build until I know how much space I need for my electrical setup. I appreciate any help.
 
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calicamper

Expedition Leader
Only big complication is the toaster oven. Drop that from your list, use a camp stove. A good quality deep cycle marine battery in the larger range 85-90+ amp hours and 80watts of solar would easily meet your needs. Skip the big inverter, just add a 12volt socket to use a small cheap inverter for the laptop charging, that can be moved to the cab to charge or power stuff when on the move.

Plus a 12v usb puck can be used either place also to charge phones etc.

The basics you have solar power that goes to a solar charge controller which is wired to the battery. The controller monitors the battery and manages the charging. Then you have a small fuse box powerd by the battery which then is tied to your power needs, fridge, power socket, lighting etc.

Think of amps like you think of gallons of fuel. But consider only about 40% of a batterys amp rating usable.

So for basics say you have a 95 amp hour battery. And you can lets say burn 40amps without taking the battery too far you damage it etc.

Most typical fridges burn 2-3amps an hour thats a conservative number but a fair one to use. Say you have worst case 13hrs where solar generation is more or less zero. 13x3amps =39amps burned. So with no other power needs the fridge can run on that battery for 13hrs.

A 80 watt panel will generate a conservative 5amps per hour. Most likely more in ideal conditions. Lets say your fridge is only burning 2.5amps then your putting 2.5 amps for sure back into the battery plus powering the fridge during solar hours.

Ok so your charging 2.5amps per hour back into the battery. Lets say you get a solid 10hrs of solar charging per day your putting 25amp hours back into the battery.

Thats the very high level thought process you need to use to map out your power needs. Then you size the battery and solar to cover your power needs. Use Amp hours as your fuel guage if you burn more than you store or generate your use is too high for the storage and generation etc.

The last 4 yrs I have been using two 10watt panels that charge a small deep cycle 18amp hour battery. We use this to power LED strip lights at night, charge phones, ipads, cameras etc. worst case use I see 6amps burned a day. Typically less. My whole kit not counting panels is housed in a single 50caliber ammo can, battery, charge controller, fuse box all in the ammo can. My two 10watt solar panels typically generate 1-1.5amps per hour sometimes a little more. This has been enough on the CA coast where 4-5hrs of fog free sun covers my typical power burn.

A fridge power requirement would need at minimum 80watts of solar, and a big deep cycle battery with lots of amp hour capacity etc.
 
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Bikersmurf

Expedition Leader
Rather than a marine battery, I'd recommend two 6v golf cart batteries. They're better built for your intended use. Costco has them for about $110 usd. In the US they're Interstate batteries.
 

Jdavenport

New member
Thanks for the heads up, the plan is to do 2 deep cycle batteries. Very informative and I feel like I know a lot more now. One question for you though, if I wanted to be able to plug in to a campground wouldn't the inverter still be necessary? And does the inverter add to the draw of power that I need to take into account? Thanks again!
 

calicamper

Expedition Leader
No you would need whats basically a fancy battery charger, RV guys call them a confusing name "converter" the marine guys call them battery chargers. LOL You plug shore power into the charger, then this charger powers / charges your 12v system. Dont confuse this with house power plugs or powered stuff like AC units which run off of a dedicated shore power power system.

In your case with simple needs keep it all 12v based and if you want shore power charge capability get a marine battery charger.
 

calicamper

Expedition Leader
My 28ft sailboat I have two group 31 marine batteries and a 15amp max output shore power charger. The boat also has a dedicated house power/shore power circuit that powers standard 110 house hold wall plugs. But this is pulled off the shore power and tied to a breaker panel and is a stand alone power system. I might use these once a yr to run a shopvac. All the rest is 12v stuff.
 

Flagster

Expedition Leader
I would recommend a good marine wiring/solar book. We used many resources when switching our sprinter from a goal zero powered solar setup to a proper house battery setup...both have their advantages...but the marine guys especially sailors have their **** together...and give much better answers on forums
 

jblaze5779

Observer
Try to keep as much of your stuff DC 12v as possible. No sense in losing energy in the conversion process from DC to AC only to just go back to DC at the device..
 

rkj__

Adventurer
Only big complication is the toaster oven. Drop that from your list, use a camp stove. A good quality deep cycle marine battery in the larger range 85-90+ amp hours and 80watts of solar would easily meet your needs. Skip the big inverter, just add a 12volt socket to use a small cheap inverter for the laptop charging, that can be moved to the cab to charge or power stuff when on the move.

Plus a 12v usb puck can be used either place also to charge phones etc.

The basics you have solar power that goes to a solar charge controller which is wired to the battery. The controller monitors the battery and manages the charging. Then you have a small fuse box powerd by the battery which then is tied to your power needs, fridge, power socket, lighting etc.

Think of amps like you think of gallons of fuel. But consider only about 40% of a batterys amp rating usable.

So for basics say you have a 95 amp hour battery. And you can lets say burn 40amps without taking the battery too far you damage it etc.

Most typical fridges burn 2-3amps an hour thats a conservative number but a fair one to use. Say you have worst case 13hrs where solar generation is more or less zero. 13x3amps =39amps burned. So with no other power needs the fridge can run on that battery for 13hrs.

A 80 watt panel will generate a conservative 5amps per hour. Most likely more in ideal conditions. Lets say your fridge is only burning 2.5amps then your putting 2.5 amps for sure back into the battery plus powering the fridge during solar hours.

Ok so your charging 2.5amps per hour back into the battery. Lets say you get a solid 10hrs of solar charging per day your putting 25amp hours back into the battery.

Thats the very high level thought process you need to use to map out your power needs. Then you size the battery and solar to cover your power needs. Use Amp hours as your fuel guage if you burn more than you store or generate your use is too high for the storage and generation etc.

The last 4 yrs I have been using two 10watt panels that charge a small deep cycle 18amp hour battery. We use this to power LED strip lights at night, charge phones, ipads, cameras etc. worst case use I see 6amps burned a day. Typically less. My whole kit not counting panels is housed in a single 50caliber ammo can, battery, charge controller, fuse box all in the ammo can. My two 10watt solar panels typically generate 1-1.5amps per hour sometimes a little more. This has been enough on the CA coast where 4-5hrs of fog free sun covers my typical power burn.

A fridge power requirement would need at minimum 80watts of solar, and a big deep cycle battery with lots of amp hour capacity etc.

This is a nice reply, that gives a pretty good basic overview.

The only thing I will add, is that you need to take into consideration your access to the sun. Much of my camping is out of a teardrop trailer, in the woods, for the weekend. Some of the sites I camp in are near full shade, which severely limits solar charging capabilities. This can be a concern, if you are trying to run a fridge, with a small battery / battery bank. To try and make the most of partially shaded areas, a long extension cord can be helpful to ensure you can follow the sun with your panel.

36298296311_4794021926_c.jpg
 

rruff

Explorer
That being said I'm converting the bed of my pickup into a mini RV type/Van setup and looking to be able to run small appliances such as a toaster oven, charge my phone and laptop, and potentially an ARB fridge without having to worry about running out of battery for 2-5 days typically.

First thing you need to do is tally up your typical use, typical sun exposure, and typical number of days. Size your system, play with the numbers and see what you can live with. You need the panels, batteries, wiring, charge controller, and battery monitor (could be as simple as a voltage meter).

Like calicamper said, the oven is probably a bad idea. You don't want to use your limited and precious solar electric to produce heat; not when there are other options. The fridge is another large consumer of energy. If you are only camping occasionally it would make more sense to use a good cooler and ice.

None of the things you mentioned should require an AC inverter. For your laptops and phones get an adapter that converts 12 V to whatever DC voltage you need. For laptops 19v is typical (volts and amps will be on your power brick) and I think phones are 5v.

Flooded deep cycle batteries are cheaper and work well. If the batteries are in your living space then consider AGMs. In either case do not drain them more than half their capacity (else they will die early). Batteries are your "tank", the bigger their capacity the more cloudy days you can endure.

I'm planning to just get rid of my starting battery and use a couple big AGMs for everything. Simpler; don't have to screw around with isolation. They can easily start the truck, and I won't be draining them more than half way. Wire them up to the alternator just like the starting battery was.
 
It's a LONG write up, but I also started at knowing nothing and built my own solar system for my homemade camper. I had problems so I want to help

I would definitely hook up the alternator to charge your battery bank. There is a good write up on this forum of how to do this with a solenoid for relatively cheap. If a dual or high output alternator is an option for your truck I would consider that as well. Solar is great when there is sun but its output is dramatically affected by cloud or shade cover. You don't want your food going bad because its cloudy and you have no alternative power source.

After living in my camper full time for the past year my experience has been:

-Only expect 80% of rated output from solar panels on what you think is a good sun day
-If you look outside and think it is OK/not great solar collection weather, expect 40% of rated output from panels.
-If conditions look worse than that expect 5% or less

This is how I went wrong in designing my system. I expected at least 90% on good days and OK conditions to drop to 80% and gradual, incremental loss from there. As a result I expected to fully recharge my battery each day and therefor only have a battery bank sized to run my system for 16 hours. This is a problem if I camp where there is lots of shade or if I have cloudy days. I have to run the truck to charge the system with the alternator.

I am currently set up with 300W of residential solar and an MPPT charge controller from Renogy. And 2 x 75amp hour AGM Optima batteries. I use this to run a 65L (big) fridge freezer, large fan, LED lights, charge phones/camera batteries. The break down is as follows:

Fridge= 3 amps an hour 24 hours a day
Fan. = 1.5 amps an hour. 10 hours a day
lights = .5 amps an hour. 2 hours a day
phone/camera= .5 amps an hour. 2 hours a day

So I consume 89 amp hours a day. If you multiply that by the voltage, you get watts, which is what solar panels are usually measured in.
89 x 12.5= 1112.5 watts.
My solar panels collect 240W an hour (300x 80%) on a good sun day.
So, I need 4.6 hours of good sun a day to keep my system charged.

This is easily accomplished in good weather.
The problem is that a partially cloudy day drops my solar collection to (300x40%) 120 watts an hour. I would need 9.2 hours of partially cloudy sun to charge the system. That's a stretch.

My point being if you are depending on solar you need a pretty big system to have "enough".
Doing 2-5 day trips I would focus on a large battery bank and hooking up the alternator to charge the bank and carrying a battery charger appropriate for whatever kind of batteries you get.
 

nixid

Observer
"Fridge= 3 amps an hour 24 hours a day" 72 of your 89 amps est. per day
Does Fridge use 3 amps when running? How many hours a day does it run?
24 7 on fridge seems high.
 
"Fridge= 3 amps an hour 24 hours a day" 72 of your 89 amps est. per day
Does Fridge use 3 amps when running? How many hours a day does it run?
24 7 on fridge seems high.

Yeah. I thought I would be averaging 2 amp hours per an hour, so this threw my calculations off as well when designing my system. It consumes a normal amount for a large fridge(2.5-3.5 ah per an hour while running), but has longer run times that I blame on the way I use it.
It doesn't run 24 hours a day, but I have found that I average 3 amp hour per an hour consumption over the course of several days. This is higher than most people I have talked to, but it is larger than most people's fridge and it is a split unit with a freezer and I am operating it in the tropics with minimum recommended ventilation and full time living conditions. All of which adds to its run times and as a result its average consumption.
 

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