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kmacx5
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# Posted: 15 Jan 2017 21:50
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Hello, new to living off grid my wife and I are building a small off grid cabin. I would like to wire it just like my travel trailer, with a 12 volt deep cycle battery wired to a converter changer to power 4 watt LED lights and possibly a small water pump. Also I would have a 30 amp cable from the converter charger to a Honda generator which would power 6 or so ac outlets. Has anyone done anything like this before, eventually we will go solar but until then I see no reason why this would not work. Does anyone else think this would work?
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hamish
Member
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# Posted: 15 Jan 2017 22:52
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Is you are using a converter charger like the one you have in your travel trailer there is no need to incorporate the 30 amp line to your generator.
Take a look at your AC loads.
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kmacx5
Member
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# Posted: 15 Jan 2017 23:10
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Thank you for your response, the reason behind the 30amp cable is that's just what my travel trailer has I guess that's because of the roof air conditioning, when you say AC loads you mean what will I be powering really not much a coffee pot and other small appliances. I just want to use the generator a little as possible and use the battery for lighting
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MtnDon
Member
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# Posted: 16 Jan 2017 10:43
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The cable between the converter / charger does not need to be 30 amp rated if the generator output is less, such as 16 amps with an EU2000i. The length of the cable can be a factor too as long cables have losses. A generator should be as distant as possible, so with that in mind a 10-3 (30 amp) cable may be desirable.
Is there ever going to be a battery bank large enough to enable use of an inverter to supply AC?
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kmacx5
Member
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# Posted: 16 Jan 2017 11:20
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As far as the inverter that would be down the road some time when we can get solar. So right now I would be using 2-12 volt batteries wired parallel to the converter charger then to perhaps 10 or so 4 watt LED lights threw out the cabin with switches controlling the lights, the generator will only be powering small 110v appliances when they are needed with the thought that when the generator is running it will be also charging the batteries.
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MtnDon
Member
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# Posted: 16 Jan 2017 18:03
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If you do not already have them, you might want to rethink the batteries. Two 6 volt golf cart batteries in series for 12 volts is a better setup than batteries in parallel. Cost and amp-hour capacity will be about the same if you can find a Sams Club or a Costco near you that sells golf cart batteries. The golf cart battery has heavier plates, provides a longer lifespan if cared for..
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kmacx5
Member
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# Posted: 16 Jan 2017 21:33
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Thanks MtnDon never thought of that I think I will go that route. Do you see any other possible problems i may run into, I will be transporting the generator and batteries with me every trip so they will be fully charged each time.
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MtnDon
Member
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# Posted: 16 Jan 2017 22:11
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Just be careful handling the batteries. You don't want to spill acid or short circuit the terminals.
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razmichael
Member
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# Posted: 17 Jan 2017 09:20
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Some thoughts that might or might not apply to your situation. I started my adventure with a Pop-Up trailer for a couple of years before building and modified the trailer to make it more suited for off-grid use (without solar initially much as you are doing). The built in converter is primarily meant to allow the use of 12V lights when plugged into 120 at a RV site. Most also have very poor battery chargers. Your actual use case is a bit different as you plan to be on 12V most of the time and occasionally use 120 from the generator - exactly as I was doing with my pop-up. I rewired mine to bypass the converter (other than using the 120 circuit breakers). I added in an inverter with a built in smart charger and auto switch over. The two 6V batteries (Trojan 105s) where in a case and on a small dolly so I could take them home with me. On longer stays I would bring up my small Honda generator and simply connect to the trailer which would then feed the 120 sockets and recharge the batteries.
When I built the cabin this system simply (OK - not so simply) moved into the cabin and I added panels and charger controller. So now my lights, water pump and ceiling fan are 12v and I have some 120 sockets around. In general I keep the inverter off unless needed (it has a remote on-switch). The batteries are now 6 or so yrs old and still holding up great (they remain at the cabin through a cold Canadian winter). I can run a vacuum cleaner, blender etc (although need to be somewhat conservative), and for heavier loads, can run the generator (plugs onto a generator socket on the outside wall through to the inverter/switch/charger).
Some notes: The inverter is a modified sine wave - I have no need for a pure sine wave. If I did, I would likely purchase a small one for the actual need and add it in separetly. Having said this, the cost of pure sine wave inverters has dropped considerable since I purchased my Xantrex HF 1800, but at the time, a similar powered and with the same features pure sine wave would have been so much more expensive.
Would I do it differently today - possibly - I might just have wired the cabin for 120 with some 12V backup, on the other hand, the current setup works perfectly for our needs and would not really have changed the core setup any - we are not full time nor have a need for things like appliances. Certainly your use case will differ somewhat.
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MtnDon
Member
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# Posted: 17 Jan 2017 10:06
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Good point on the RV converter / charger. There are a number of junky ones that use cheap charger sections that can actually hurt batteries over the long term Progressive Dynamics makes a couple of very good ones. Their chargers are true multi-stage chargers. Beware there are counterfeit PD units being sold on ebay and amazon. The genuine article are pretty much the best RV units being made.
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razmichael
Member
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# Posted: 17 Jan 2017 10:24
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And many RVers only have a cheap battery as a backup (for 12v lights) while almost always plugging in at a site - hence the default cheap battery and converter. The battery is often charged directly from the tow vehicle so far from optimum for battery maintenance but not often the priority unless they plan on camping without hookups.
Mostly though, the use of a converter is really not well suited to the off grid requirement - it is flipped around. If the OP is planning to purchase something, a converter is not the best solution and provides limited value in this situation.
Budget allowing it, a smart charger, inverter and switch over (auto or manual) might be a better selection (some combination of the three depending on needs). In fact, the cheapest would be simply to get a good charger initially if $ are an issue. He can charge the batteries if needed, run his lights off the battery, and power the 120 sockets if needed from the generator (but not the batteries). Add an inverter and auto switch later?
I went the easy route (not the cheapest however) and got an all-in one Inverter. Anyway - lots of ways to skin the cat.
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razmichael
Member
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# Posted: 17 Jan 2017 10:51
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One more thing - If you are going to be taking the batteries home with you then be careful about the wiring choice. Not such a big deal if you are only running a few 12V lights but if you want to also power an Inverter, you need some heavy duty cables, both between the batteries (if using 2 6Vs) and between the battery box and inverter/system. Note the Anderson connectors.
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kmacx5
Member
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# Posted: 17 Jan 2017 11:14
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Thanks guys this is exactly why I joined this forum, Raz do you have a diagram of how you wired your setup. I understand that most controller/chargers are lacking on the charging side and i like the smart charger idea but did you wire the 12 volt side to a fuse panel and the 120 side to breakers?
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razmichael
Member
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# Posted: 17 Jan 2017 12:07 - Edited by: razmichael
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Hi kmacx5,
Just heading out so I'll dump this link to my build photos onto you
Build
I make it very clear in my build thread that I made this much more complex than needed but I had a lot of spare winter time on my hands to have some fun.
In summary, the 12v side is fused near the source for a number of main (heavier wire to reduce voltage drop) leads that are then individually fused when broken out prior to going to light switches etc. This can easily be simplified depending on what you need/want. If you only have a few light switches that can be co-located, look at marine panels that include the fuse and switch. I went with a more standard look and layout, in part because I could switch most of it over to 120 in the future if I wanted. I actually run 2 12v circuits, the main one that is switched on upon arrival and a second one the comes from the 'load' off the charge controller. This is always on and handles motion sensor lights etc.
Regarding the 120, since I only use this lightly, I currently just run two circuits directly from the inverter as this contains the GFI circuit and basic 15 amp fuse. Easy to add a small panel in the future as the inverter is designed to be hard wired if needed.
Again - don't be freaked out by the main wiring area - way more complex looking than it really is and way more complex than it really needed to be.
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