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Old 11-02-2021, 08:55 PM   #1
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Help sizing a battery to go off grid.

Helping Cutebutnot here with her off grid needs. Use this post to respond on battery sizing, and going off grid how to help set this up.

Quote:
Originally Posted by Cutebutnot View Post
JohnB, Thanks for taking the time to help out, you are truly appreciated. I did deduce the battery issue needed last night after reading one of the posts here so the forum is a great resource.
My next question regarding the 1st battery to purchase will be needing to know how much power Iíll need to power everything off grid while traveling west long distance. Iíll be running the frig, furnace, dehumidifier, air purifier, and powering/charging laptop, phone, and other electronicals. My mind has tried to figure out amps watts and necessary power but its a struggle, my brain isnít functioning mechanically that way with so much going on currently. Lol. I just dont want to purchase ďaĒ battery later to find out that getting a bigger one or two would be a better option. I can build a batter box to house them if I need to, that IS within my scope.


Before I purchase a battery and begin there, Iíll wait to hear back from you.

Big hug and gratitude ✌️
HeatherAnn
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Old 11-02-2021, 09:20 PM   #2
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Hi HeatherAnn,

The good news, we have several of us here on the forum who camp off grid and have worked through the hurdles of batteries and how to recharge them.

We will try and help you, but you may soon see, all the devices you listed may take an amount of power that is hard to create. While the battery size is part of this, the bigger question is, how do you re-charge the batteries?

There are two popular ways on doing off grid, or a combo of both. And the battery technology affects this too. I'm going to talk to a lead acid battery bank setup which if it is used within it's means, can provide a very good system at a more economical cost.

Option 1. A generator is used to power up a "good" power converter which is capable of charging your batteries back to 90% of the full capacity in a reasonable amount of time. Part of this is upgrading to a modern 3 stage battery charger and ideally one with de-sulfate mode to help the batteries last longer. Your original Sunline battery charger in 1994 may only be one stage, standard charge. The new 3 stage power converters offer float mode to maintain the battery, standard charge mode, and boost charge mode. With a lead acid battery in boost charge mode, it can handle a faster charge and then taper into standard charge as it approaches 90% of full charge. If you ever want to get to 100% of full charge, it takes many hours, 12 plus hours, to jam the last 10% in. And ideally, you only drain the battery down to 50% and then charge back up.

Option 2, a solar bank to recharge the battery. Pending where you will camp, the solar can be on the roof of the camper, or portable ground unit or a combo of both. The only issue with solar is, the sun has to shine with good intensity and you have to have a large enough solar bank for your battery bank.

A combo of solar and generator also helps overcome cloudy days, camping under tree cover, and times when some camps only allow certain limited generator run hours.

That is the basics on the recharge. Where it starts getting more involved is, how big a battery bank do I need, and how big does the recharge system need to be to recharge the battery bank?

To pass along how we boondock, we like to camp on the east coast under lots trees. Many times on the shores of a lake, or stream. This kind of camping makes it harder to go solar with so much tree cover. In our case, we currently use a Honda EU-2000I generator to power a Progressive Dynamics 60 amp 3 stage charging with de-sulfate mode power converter. We have two group 27 lead acid batteries and we have converted all lighting to low power LED lights.

Most of the camps we camp at only allow 5 to 6 hours a day to run a generator, and they split that time up in 2 stages across the day. A morning and later afternoon is common. This means, we need to recharge the battery bank in this time frame. Pending how much power we use, it can recharge in one day to 90%, other times it takes two days. And some times, we can skip a day of charging.

One needs to turn into a power miser to not waste power. Since we have 2 times a day we can run a generator, we can use the hair dryer for my wife in the morning and the microwave before nightly dinners. We do not use the air conditioner, it is too much of a power draw. The fridge and the water heater run on gas. And we only turn on the water heater when we need hot water. We have a large Maxx Fan in a camper roof vent with multiple speeds and a thermostat. We crack open the windows we want air to come in, and exhaust out the roof on hot nights. Where we boondock, we normally do not need AC much and being too hot has never been a problem.

Occasionally the camper furnace might run, but this is limited. It is not a great use of DC power as it is a power hog, but it works on limited use. If you are needing more heat, then there are other options beyond the camper furnace. We do not boondock in the very cold months.

We recharge the cell phones and lap top when the generator is running. The cell phone/Ipad can recharge from the battery bank too if needed.

We can go for a long as wanted on this setup. Days to weeks.

There are other options for dehumification other then running a AC compressor dehumidifier. We can talk on that too, but need more info on your needs of this.

This may help get you started on asking some more on this. We have others with the solar setup who can help too.

Hope this helps

John
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Old 11-03-2021, 07:33 AM   #3
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Hi HeatherAnn,

These 3 things of yours need to be thought through on how to handle them.

Quote:
furnace, dehumidifier, air purifier,
Need to know some more about the furnace needs. If this is an occasional warm up the camper first in the morning for 15 minutes, as it got down to 45 to 50F then night before, but during the day it gets up to 70F, then using the camper furnace is tolerable for those short and infrequent situations. But, using the camper furnace to keep warm part of the day, and all night camping in cold weather, it just uses way too much power. The camper is not insulated enough for sustained cold weather and not loose a lot of heat. Tell us what your needs of camping are. There are other options that do not use battery power to do this.

Tell us about the dehumidifier use too. If this is a standard 120 VAC compressor driven dehumidifier, that is a problem just like the furnace. They draw a lot of power to run all day/night off a battery. Knowing some more where you are camping and what % relative humidity you are trying to get to, there are some options that can help, but may or may not cover your needs.

The air purifier, if this runs off a 120vac, look for a tag on it, and post. And how long it will run during a 24 hr period. This may be an issue running all the time. But, again knowing your needs, we might be able to help.

While you can size a battery bank big enough to handle all that heavy power, it becomes a problem being able to recharge the battery bank daily to keep up with it. The cost of the components to create that much power, and recharge that much power, become very high, in both cost and weight. It can become impractical to do it on such a small camper scale. But, let us know more about what you need, and we can maybe help suggest some work arounds. Going off grid, we have to shift into, think being a power miser, how to do things very efficient and only doing what we need. It makes creating the energy easier and more practical.

Hope this helps,

John
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Current Sunlines: 2004 T310SR, 2004 T1950, 2004 T2475, 2007 T2499, 2004 T317SR
Prior Sunlines: 2004 T2499 - Fern Blue
2005 Ford F350 Lariat, 6.8L V10 W/ 4.10 rear axle, CC, Short Bed, SRW. Reese HP trunnion bar hitch W/ HP DC

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Old 11-04-2021, 08:10 AM   #4
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Twin batteries and solar here standard lead acid group 24's. Winter no matter what in my area (Maine) is kind of out of the question. The biggest hog is heat, no matter what it sucks up propane and battery power. Campers are not exactly well insulated so they run a lot. In the warmer months my 100 watt solar is sufficient spring and fall for all of my DC needs. It however is a bit of a hybrid It is in an aluminum frame that sits on the ground I can turn and elevate it for max sun. The controller is fixed to the panel and I have a battery plug in arrangement, it folds up dead flat maybe 4" high and travels on the bed. No matter what kind plug in gadget you use fan, toaster etc is a factor of 10 so if have some thing that is rated say 5 amps AC it will draw 50 amps from the battery. An ease way out would be a small inverter generator say like 2500 watt and just plug the camper into that.
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Old 01-06-2022, 02:00 PM   #5
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I gave up on the internal wiring a year ago. I now use this:
https://www.amazon.com/BIUBLE-Batter.../dp/B08GYFP5JK
its a portable battery jumpstart unit. I ran new LED lights and hid the wires in the cabinets and in the seams of the walls/ceilings. As its 12v, I used some old 4 wire phone wire I had laying around. If I have 110v, then I use that, but the battery pack lasts for days, no problem and I can re-charge it while driving.
As a result I got rid of the big battery (and propane tank) on the front of the hitch and reclaimed that space for storage.
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