Need some advice...I just build a small camper out of a 6 by 12 cargo trailer for dispersed camping. I am putting in 3 12v 206ah lithium batteries in parallel. So 12v 618 ah. 800 watts of solar. 100amp mppt solar controller. A aims 3000 watt to 9000 watt surge inverter/charger. My question is....with this set up which draws the less amount of power from battery bank. Running Ac equipment ...apicool fridge/freezer , a TV/Dvd player. A couple led lights. Or should I use Dc equipment. So I guess the main question is Does Ac draw less power from the batteries over a day or does Dc ???
AC vs DC appliances
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timselectric
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Dc is better, if it high efficiency dc equipment. Because you don't have the efficiency losses from inverting from DC to ac.
DerpsyDoodler
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Just have to keep in mind you may still want to have an inverter around (at least a small one) for the occasional AC need. One that's easily switched off when not used or needed.
You definitely want as much of your stuff to run off of DC as possible. Not only is there a conversion loss when inverting your DC battery power to AC, just having the inverter on at all will draw power even if you are not using any AC loads. So the less you can make use of an inverter the longer your batteries will last.
Are you planning on more solar panels in the future? I ask because you mention you are getting a 100A SCC but 800W at 12V only needs 65A. You can probably get by with 55A or 60A since your panels will be flat mounted and you will rarely get the full 800W. The lower the charge current of the SCC the lower the price.
Also avoid a 12V 3000W inverter if you can. 2000W (or lower) could be a better choice depending on your needs. 3000W at 12V means 300A which requires 4/0 wire. And the larger inverters tend to have higher idle power usage compared to lower wattage ones.
Are you planning on more solar panels in the future? I ask because you mention you are getting a 100A SCC but 800W at 12V only needs 65A. You can probably get by with 55A or 60A since your panels will be flat mounted and you will rarely get the full 800W. The lower the charge current of the SCC the lower the price.
Also avoid a 12V 3000W inverter if you can. 2000W (or lower) could be a better choice depending on your needs. 3000W at 12V means 300A which requires 4/0 wire. And the larger inverters tend to have higher idle power usage compared to lower wattage ones.
timselectric
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Possibly two small inverters. #1 serving loads that you use occasionally. And #2 serving loads that you rarely use.
I only have 200 amp hours of FLA batteries in my camper but since I cook with propane and the fridge is absorption, I rarely run low. My heaviest draws are a normal Lenovo business class laptop and an efficient 22 inch monitor which are both powered by DC-DC adapters. Together, they draw around 40 watts, measured. A diesel heater takes about 10 watts to run on low. Lights, cell booster, fan and cell charging adds another 50 or 60 watts if running, all of which I power with DC.
I guess my point is that you can get by on a lot less power if you don't use AC appliances. I rarely turn on the inverter and would have little use for a 3000 watt inverter. If I needed to run power tools I'd bring a generator.
I guess my point is that you can get by on a lot less power if you don't use AC appliances. I rarely turn on the inverter and would have little use for a 3000 watt inverter. If I needed to run power tools I'd bring a generator.
shadowsteve
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DC appliances will be more efficient in total Whr usage vs AC appliances but they usually cost more. In the case of TV's they are usually lower quality and small. With 600Ah and 800w you don't really need to worry about efficiency as you have lots of power. You'll run out of room to install appliances before you run out of power. When we have good sun we use an induction cooktop rather than the propane to take advantage of the free power.
Use 12v-USB ports for device charging so you don't need the inverter for that stuff.
Use 12v-USB ports for device charging so you don't need the inverter for that stuff.
timselectric
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A lot of the 20" TV's I install now, are 12vdc using a wall wart. I usually power them from the DC power supply that feeds the other equipment that I am installing.
I would suggest as much as you can as DC. Often 12V DC appliances are built to be more energy efficient, but the AC counterparts are not. AC should only be used for larger loads, like cooking, and the few things that might be difficult to find in 12, like a TV and DVD player.
For comparison. I have 300Ah of Lithium. ~700W of solar. I have 2 12V Dometic coolers, one for a fridge and one for a freezer. 12V LED lighting. A 12V adapter for my laptop. The only things I use AC for are the induction cookplate, and a 32 inch flatscreen TV. Neither are used daily, as I also have propane to cook with. I have a 3000W inverter, but I have a 100A fuse on it, so it is limited to closer to 1200W.
My usage is about 170Ah per day. On sunny days I hit 100% SOC by about 1pm, or I can go several cloudy days without any issues. If I go 3 cloudy days, it might take 2 or 3 days to get back to 100%.
For comparison. I have 300Ah of Lithium. ~700W of solar. I have 2 12V Dometic coolers, one for a fridge and one for a freezer. 12V LED lighting. A 12V adapter for my laptop. The only things I use AC for are the induction cookplate, and a 32 inch flatscreen TV. Neither are used daily, as I also have propane to cook with. I have a 3000W inverter, but I have a 100A fuse on it, so it is limited to closer to 1200W.
My usage is about 170Ah per day. On sunny days I hit 100% SOC by about 1pm, or I can go several cloudy days without any issues. If I go 3 cloudy days, it might take 2 or 3 days to get back to 100%.
OffGridInTheCity
Solar Wizard
I run a 4.5 cu ft 120v refrigerator in my 7 x 14 trailer 24/7. The power consumption is very low. If you don't have 120v then maybe DC but if you already have 120v inverter - then I'd say 120v is viable.
I've watched a few youtubes on DC vs AC and it seems like the DC 'cooler' types are low power because they're sooooo small. If you actually compare cu ft to cu ft / power, I believe it's pretty close
I've watched a few youtubes on DC vs AC and it seems like the DC 'cooler' types are low power because they're sooooo small. If you actually compare cu ft to cu ft / power, I believe it's pretty close
Until there is a week of no sun due to clouds or camping in the shade. Sure, on a nice sunny day in the summer camped out in the open you can turn on everything and not worry about it. Camp for a week under the trees and the battery will be dead. It will then take several days out in the full sun to slowly replace all of the power, and that's with no loads during those days.
I point this out as something to keep in mind depending on the OP's situation.
I have 2/3 of the OP's battery power and 990W on my trailer. Normally I have no worries about power. But last Fall I was camped in the shade for nearly two weeks in the southeast. I had to park my trailer in a parking lot all day halfway through and even that wasn't enough to fully charge up. And I'm 100% DC other than in the summer when I use my inverter to run a window A/C unit while the sun is out.
shadowsteve
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Where you camp is a choice. My point was about using DC equipment to save the small loss from inverting. Not worth it. The difference between AC & DC appliances won't allow you to live without solar input for much longer, maybe a day more if that
How long 600Ah and 800W of solar will last with cloudy weather is entirely dependent on personal usage. I have half that much battery, and just a bit less solar. But on a boat, half of my solar is often in the shade. So, my 700W of solar is probably more like 400W-500W if you have a camper and no shade.
I can go 3 days of clouds. So its reasonable that I could go 6 days with a 600Ah battery. But, I know plenty of people who will burn through 600Ah of battery in a day and fire up the generator. It's a choice about how you decide to live. Are you going to power a 50' TV for 6 hours a day? Big loud stereo? 2 burner induction cooker and electric oven all going at the same time?
Or, do you live more modestly? I went 2 years with a 230Ah FLA bank (~115 ish usable) and managed even with that.
I can go 3 days of clouds. So its reasonable that I could go 6 days with a 600Ah battery. But, I know plenty of people who will burn through 600Ah of battery in a day and fire up the generator. It's a choice about how you decide to live. Are you going to power a 50' TV for 6 hours a day? Big loud stereo? 2 burner induction cooker and electric oven all going at the same time?
Or, do you live more modestly? I went 2 years with a 230Ah FLA bank (~115 ish usable) and managed even with that.
I run a 4.5 cu ft 120v refrigerator in my 7 x 14 trailer 24/7. The power consumption is very low. If you don't have 120v then maybe DC but if you already have 120v inverter - then I'd say 120v is viable.
I've watched a few youtubes on DC vs AC and it seems like the DC 'cooler' types are low power because they're sooooo small. If you actually compare cu ft to cu ft / power, I believe it's pretty close
It's highly brand dependent, and is actually a result of the quality of insulation more than anything electrical. A well insulated cooler will use an order of magnitude less power than one that is poorly insulated. The top of the line DC models are very well insulated, because the engineers that designed them know power will be limited. A dorm style AC model will not be. But, and expensive home freezer could be. The best I have seen are custom built, built-in type freezers with many inches of high quality insulation, holding plates that will stay cold for nearly a full day after power has been removed, etc.
timselectric
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Top loading refrigerator/ freezer is also more efficient. Because the cold doesn't spill out, every time you open it.
I would say use DC appliances when its convenient and cheap to do so. DC led lighting makes sense, powering small electronics and charging devices with cheap DC-DC converters is good. Not having your whole system reliant on the inverter is good too. But for anything where a DC version is much more expensive or difficult to find or performs poorly vs the AC version, I just wouldn't bother. I'd rather buy the cheaper AC versions that you can find anywhere, and put the money towards a good quality efficient inverter. It doesn't make sense to spend lots of $$$ to maybe gain a few percent in efficiency. I'm concerned about the efficiency of my $$$ as much as I'm concerned about the efficiency of my off grid system.
For refrigeration I have mixed feelings. I have a small Engel fridge permanently set up in my car. Second battery and 120w of solar to keep it going. Running an AC fridge would make no sense in this situation. But if I had an RV/Camper type setup, and I wanted a bigger refrigerator, I think I would buy an efficient ac household fridge and run it from an inverter.
For refrigeration I have mixed feelings. I have a small Engel fridge permanently set up in my car. Second battery and 120w of solar to keep it going. Running an AC fridge would make no sense in this situation. But if I had an RV/Camper type setup, and I wanted a bigger refrigerator, I think I would buy an efficient ac household fridge and run it from an inverter.
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