N00b Off Grid Build 1.5 kWh/day project.

Mark_Bolton · December 2014

Hi Folks,

I am needing to build a modest Off - Grid accomodation. I have a mini bus and a large caravan. My home was destroyed in a wild fire and I am now using these for full time living. I am at 31deg Lat. I have been using the bus 24v batteries and a 200 Watt panel to get by but now it is time to retire the bus batteries ( since they are getting DOD hammered ) and build something a bit more comfortable / proffessional.

It seems to be much bigger that the typical RV setup and much smaller than the typical RE home i.e. caught between two stools.

The biggest draw is a luxury 42 inch TV / monitor which I can do with out if needs be . Essentials are two 40l Engels fridges and a 200w Lemair washing machine - also chargers for 18v Li-ion power tools / LED lighting / car radio etc. High draw low frequency is a Bread Machine.

I estimate using 1kW to 2.2kW per day.

The BOM:

2 x 200Ah AGM Ritar 12v Deep Cycle (already purchased)
1 x 200W 24v no brand PV (already purchased)
6 x 200W ?? v Solar Panels.
1 x Redarc 24V -> 2 x 12 V charge balancer (already purchased)
1 x 1.5kw 24v Inverter / Charger

or

1 x 1.5kW 24V Inverter / 1 x 1kW 240vac -> 24v dc switch mode charger / 1 x 60A MPPT charge controller.
1 x 1kW Honda Genset.

The constraints are roof area available - I pretty much plan on covering the whole roof with panels. Shade would be nice :-)

I an concious of not wanting to buy too many batteries - I think I am getting the gist of the correct ratio of battery to PV. One provisioner is specing a system like this to have 1000Ah batteries. From what I am understanding here 1.4 kW would be struggling to recharge such a big bank?

I am happy to run the genset when it is cloudly. I need one that is fairly quiet so as to run in the mornings when next doors are at work. They live a fair way off but sound carries across the valley at night.

I am thinking DOD of about 60 % would be a ball park goal?

I am planning on a 24volt system with the Engels freezer thermostat @ 4.5 fridge on one split and the Engels chiller thermostat @ 1.5 car radio lights etc on the other. If they get out of balance I can easily migrate components onto the other "phase" or swap the freezer / fridge roles.

Weight is also a consideration in that the caravan must be capable of traveling once in a while.

I know a little about EE from Trades School but dont presume to know anything about this specialized and surprisingly complex realm. I have been researching dilligently and am finding much that is contradictory or even flat out wrong on various BBs and commercial sites.

THX in advance for a reality check / tips / hints / references / Dos / Donts / Dont even thinks about it's ;-)

Kind Regards

Mark Bolton

Cariboocoot · December 2014

Re: N00b Off Grid Build 1.5 kWh/day project.

Welcome to the forum Mark. I've move this to the RV section so it draws the right kind of attention.

Your batteries at 200 Amp hours and 24 Volts will have about 2kW hours available from them at 50% DOD. You do not want to discharge below that level. This should accommodate your 1.5 kW hour estimated need, but estimates can be wrong.

If you can fit six 200 Watt panels on the roof that would be plenty for recharging that much battery. Inf act it could under ideal conditions accommodate over 300 Amp hours as it should supply about 38 Amps peak current @ 24 Volts.

I have doubts as to how well splitting 12 VDC loads between the batteries will work, even with a "charge balancer". It would probably be better to use a DC to DC converter to drop the 24 Volts to 12 for those items that need the lower Voltage.

Some of your loads may be demanding in momentary current rather than Watt hours. That bread machine, for example. I've never tested one but anything with a heating element in it is likely to need some serious Watts. If you have the devices you want to run, get a Kill-A-Watt meter and do a "dry run" with each; pretend you're living in the bus and use these things as you would normally do while letting the meter measure their demands. It can save a lot of unpleasant surprises later on.

Getting a Honda EU2000i will be the best choice; if the power fails for whatever reason you have back-up.

A couple of other forum members have done/are doing the bus conversion thing. Look in this section and you'll see some of their experiences related which may prove helpful to you.

Mark_Bolton · December 2014

Re: N00b Off Grid Build 1.5 kWh/day project.

Thank you for your prompt reply and confirming my thoughts so far. Moving the thread to RV is helpfull also. The Australian Camper forums tend to be too small to be relevent to my situation but this one seems to be in the Goldilocks zone.

I am load splitting the 12 volts ATM and it works very poorly. I have the 12v 800W inverter on one arm and everything else on the other. I'd call it a fail. I was thinking that the load would be much more evenly balanced as I described below. You are right however - it is a messy ugly approach.

The advice about "pretending" to live in the bus makes me smile because I actually am :-D. I am pretending that the sun is shining and I can actually use the apliances I have. I all seriousness the "trial and error" aproach seems sound. I haven't purchased most of the equipment just yet. I am leaning in the direction of under provisioning PV and over batterying and relying on genset to pick up the slack when in high draw or prolonged overcast. Something along the lines of running the genset for 5 hours every three days and doing all the washing and baking bread etc whilst the gen set is running. My gut feel is that most folks try to over provision on PV because of an aversion to running the genny, getting to an asymptote of diminishing returns. I can sympathise with this as when doing field geophysics the genset runs all night, everynight and they dont even shut tha damn thing off when having the evening meal.

Regards to BC also. I just spent early Fall '14 in Kimberly and Canada so impressed me - beautifull country and fine fine people. Blessings !!

Mark

Cariboocoot · December 2014

Re: N00b Off Grid Build 1.5 kWh/day project.

Caution about minimizing the PV: be sure there is enough for at least a 5% charge rate after load allowance and that the batteries don't spend their days below 75% SOC. Either of these conditions can have a really bad effect on battery life.

PV is cheap, and the usual RV advice of putting as much on the roof as will fit rarely works out wrong.

Yes, BC has it's good points (the tops of the mountains) but also its bad points (the tops of some people's heads).

Mark_Bolton · December 2014

Re: N00b Off Grid Build 1.5 kWh/day project.

That jibes with my thinking also. The panels aren't expensive and will provide shade to the caravan. The bus is problematic. It is a Toyota Coaster Motorhome conversion and I lived in it after the fires until I got the caravan. It is poky and at 6 foot tall my head hits the ceiling when you cook on the gas it fills with condensation, mildew and there are rust holes in the ceiling - result it rains constantly inside the bus even when it isn't raining outside. It is wretchedly cold at night in mid winter - dont be tempted to run the oven because as soon as you turn it off it will be wretchedly cold and raining as well. I fell out of love with the old gal. She is a 1981 3l diesel and rusty - looks a fright but mechanicaly, an absolute honey and perfect for towing the 21 foot van.

I was thinking about rehabilitating her by cutting the rust out of the roof and replacing the top 3 inches higher with either a standard solar panel/s (12' x 3'), or a DIY panel using discrete cells mounted in a curved plexiglass roof with a plywood ceiling having an exaust fan for cooling.

In summary ; cover every practical horizontal surface with PV and then match the rest of the system to the kWh/day depending on lifestyle, adaptation and insolation.

The next big mystery - I really hesitate to mention this because I know where it will lead - what are the considerations cost quality when choosing between Happy Carp brand Pay Pal powerstaion off Alibaba, and, Trusted Name equipment costing an order of magnitude more...? What I have done is buy cheap crap off ebay as a stop gap until I have the answer to that question.

BB. · December 2014

Re: N00b Off Grid Build 1.5 kWh/day project.

Yea--there is a difference. Until you have done enough fun and games with the cheap stuff--You will finally buy some over priced US equipment.

And, at times, even the expensive US stuff can have issues too.

You will never win.

-Bill

Cariboocoot · December 2014

Re: N00b Off Grid Build 1.5 kWh/day project.

Well I've tossed cheap stuff from some of the cabin systems around here who have asked for my help. Never tossed a name-brand product unless it was burnt up.

You can buy once or pay twice.

Mark_Bolton · December 2014

Re: N00b Off Grid Build 1.5 kWh/day project.

Off Topic Alert!

I tottally know where you guys are going with this. When I was involved with sport aviation everything from drill bits from Aircraft Spruce to a Kit Plane from Dick Van Grunsven. I would never consider a supplier, project or concept that wasn't old school conservative, made in the USA. Here on the other side of the planet Australia we have local middle men who can double the price and give lousy support. I have found that buying direct from the USA is best. I have bought specialty products from the USA where if I was unhappy they could just, go ahead and ignore me. Far from that, the ethos is to overwhelm the customer with awesome delivery. I get the feeling that they were even more supportive since I was a planet away. In one blindingly amazing instance I bought an aircraft canopy from Todd's Canopies. Once he knew I was at the dog end of the supply chain he organised everything and just made it all happen.

I just got back from a stress leave trip (got my whiskers singed in a bushfire) to Canada and Montana. You hear po mo whining about Americans and Consumerism ? Well I was no big "consumer" just me and my Mum buying me a Stetson for $40 bucks. In Montana clothing store that is a big deal. It was like we were all family.

Here is where I reproach you guys for having it so good for so long; I was at a Sizzlers where the waitress - 70 going on 50 - lost her footing and had a load of food and drinks heading into the laps of the customers. What I saw was a slo mo crockery tumble ninja who grabbed each falling article to herself just like Buffalo 66 - she wound up drenched and covered with crap but not a drop on the customer.

My response was "Let me take a moment to Worship you - talk about taking one for the team! We should quake were you ever to swap to the dark side and use your food handling powers in the service of evil." Maybe no one else saw what I saw. I heard mumblings of "clumsy bitch". She was a hero in my eyes and I made sure she knew it.

There is so much to love about the USA - as a foriegner it burns me to see those that take what's to love for granted.. nit pick it and dont see fit to contribute. Run down your fellows. Leaners not lifters. Mostly it is quid pro quo however and nothing to whine about - well not in Kalispell or Kimberly ... so that's OK.

I love the USA and Canada ...however don't mean I straightaway belive everything I hear.

Regards

M

CraziFuzzy · December 2014

Re: N00b Off Grid Build 1.5 kWh/day project.

What is keeping you running at 24 Volts on the battery bank? If you have an abundance of 12 Volt appliances, it is far more efficient to run them direct from the batteries as such, instead of splitting load on the bank (which is VERY bad for the batteries), or losing energy in a DC-DC converter.

Mark_Bolton · December 2014

Re: N00b Off Grid Build 1.5 kWh/day project.

CraziFuzzy wrote: »

What is keeping you running at 24 Volts on the battery bank? .....

You are absolutely right. The setup at present needs constant battery swapping to prevent the charge disrepancy becoming too great. The REDARC balaancer doesn't seem capable of doing thiis. I was under the misaprehension i HAD to have 24V since the panel was 24v.

The system is evolving from what I had when living in the bus and going through iterations as I acquire more equipment. I am planning on now having the bus and the caravan as seperate systems. All the 12 volt equipment is in the bus - fridges mainly. All the 240v equipment in the van - I will be mainly running a 24v inverter for the TV / WASHING MACHINE.

It's a learning curve thing.

N00b Off Grid Build 1.5 kWh/day project.

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