Lower priced RV system

System · June 2010

Hello folks.

Because of job loss I was forced to live off grid in my RV for now, and may be relocating with it at some point. I have been using a Honda eu1000i generator and a Schumacher WM-2500A 25 amp charger to charge two type 29 125ah deep cycle batteries, that run a 13” TV, my laptop, and a few watts of LED lights. Because of my low quality charger, the cost of gas, and the hours I am putting on the generator, I thought it would be cost effective to install a lower priced solar system, and only use the generator as backup.

My choice so far for equipment is 4 Kaneka P-LE055 55 watt pv modules, ground mounted, and a Rogue charge controller.

I need about 100' of wire to run to the closest sunny spot for the modules, so MPPT seems to be cost effective for me. At 24V with 10 gauge wire the voltage drop should be in the 2% range for the normal operating amps, if I run a separate cable to each pair of panels, which would be wired in series, then parallel the two at the controller. I would properly fuse everything also. That would keep my wire costs in the $100 to $130 range.

Total system price would be between $700 and $850, depending on the source of the pv modules. I'm wondering how legit the lower priced source is, though I did confirm the shipped price with a phone call, but they are sold out now and are being shipped to their warehouse in a week (they say). $282 for 4 55w modules shipped does seem to good to be true though. I know those modules are not the best, but price is a huge factor for me right now.

I do plan to upgrade my batteries as funds allow.

I would appreciate any thoughts or recommendations you folks may have, especially any cost savings ones. I also would like to thank everyone here for all the great information posted here. This is the best source for good, knowledgeable information on solar that I have found on the web.

BB. · June 2010

Re: Lower priced RV system

It sounds like you have the basics down. The Rogue is a fine controller for your current needs.

The thin film panels, as you know, are about 2x the size (area) for the same power output as crystalline (mono/poly) panels are--but they are 2x the costs too... It looks like the P-Type solar panels have a 10 year warranty--but that should be enough to keep you in power for the foreseeable future.

Eventually, you will probably need to grow your system--And other battery, inverter, charge controller, etc. choices will have to be made--but, hopefully at that point, the economy will have recovered and you will have more funds and know where you will be living at that point.

Obviously, solar is expensive, and it sounds like you have the conservation down.

Regarding the Honda--For a 12 volt battery bank, you would want a 20 amp charger to load the Honda beyond 200 watts for best fuel efficiency--If you run the Honda below ~200 watts, the fuel efficiency starts to fall dramatically (you are able to run "ECO Throttle" on?

To that end, if you run your battery bank down, then run the Honda to bulk charge the battery bank back up to 80-90% state of charge, and let the solar panels take it the rest of the way--will be your best use of fuel (assuming that your loads, on occasion, exceed the capability of your solar power).

Other solar charge controllers have higher working voltages (you can run panels with upwards of Vmp-array of 100 VDC) and get more power on less copper wire--But they are certainly going to cost more money--and will not be that efficient with smaller arrays (400 watts or larger is usually a good starting point).

Also, if your loads grow--about 1,200-1,500 watts is the maximum inverter/load on a 12 volt battery bank--At that point, you are looking at wiring/batteries that need to support upwards of 150 amps DC with very low voltage drop--lots of expensive copper there too...

-Bill

System2 · June 2010

Re: Lower priced RV system

Thanks for the reply Bill,

I'm hoping to get by with minimal inverter power for as long as possible while RVing. Propane powers most of my systems. Currently I only use a 100w inverter for my laptop. So far I have been running the generator at night for about four hours with the charger on the 12 amp charge setting with eco-throttle on, to fully charge my batteries, and run my TV, laptop and lights, and sometimes charge my cordless tools and AA batteries, until bed time. Then I may watch TV in bed for a few hours (it's a 12V TV). The following day I watch a couple hours TV in the morning, and sometimes use the laptop for a few hours. The batteries almost never go below 50% SOC. I'm hoping to cut the generator run time to a minimum, as the hours are already high on it, and it would cost as much to replace it as the solar system would.

I see that you have a eu2000i. Let me run this by you. I have one also that I have had for quite a few years. I was using it on my RV, until one day when it was running fine it just died. I changed the oil and plug first thing to no avail. I then found it was getting no spark at all. I first thought that the low oil shut off was the problem because Honda's are famous for that on some of their engines, but I couldn't even find it on the eu2000i (I have repaired it on GX engines). The local Honda tech I talked to said he has never seen that problem before. I got a great deal on the eu1000i from a friend, that was almost new, because he needed money, so I bought that instead of trying to get the eu2000i repaired.

I hope the economy improves before too long.......but that is for another forum I suppose.

Bob.

BB. · June 2010

Re: Lower priced RV system

I really think the eu2000i is the right size for an emergency home backup genset (if you don't have A/C, electric heat, etc.)... Very fuel efficient at lower loads (like 400 watts or so).

For you, see if you can keep the loads on the eu1000i above 200 watts or so--I.e., charging your battery at a higher current, perhaps running some of your other AC loads at the same time (TV, lighting, laptop).

Basically, the battery will cost you ~20% losses for charge/discharge cycle, and another ~15-20% loss for the inverter...

It is a balancing act--but if you can stay around 200 watts or higher on your eu1000i, your fuel efficiency should be better than if you let the charger drop down to 100 watts or less at the tail end of the charging cycle.

A Kill-a-Watt or some other method of measuring your loads (and kWH's would be nice) against your fuel usage will help you keep your costs a bit lower. From what I remember, if you are in the area 5kWHr per gallon or better of kWH/gallon of fuel you are doing well... If you are 1/2 that or less--probably you can probably look into changing your operation around for better fuel economy.

Regarding fixing the Honda eu2000i--From what I have heard, they are reliable right up until they die (hopefully with many 1,000's of hours)--then they are hardly worth fixing.

Perhaps somebody else here with more experience can help you will fixing it (or you guys could even do a parts sale--your inverter to somebody with a good engine, etc.).

Otherwise, there is the Yahoo eu2000i group (yea--sounds as bad as us here with the solar forum :roll:):

http://autos.groups.yahoo.com/group/Honda_EU2000_Generators/

For smaller power usage (like RV's and small homes)--I am not sure there is any better solution for low(er) costs and fuel efficient operation.

-Bill

RCinFLA · June 2010

Re: Lower priced RV system

I think the Schumacher WM-2500A charger is 10 amps that does short periods of 25 amp output.

You should also rig a feed from RV alternator so you can charge the batteries when you are driving the RV around. Check the RV manual, it may already provide a connection for this capability.

BB. · June 2010

Re: Lower priced RV system

One thing I did not really make clear--if you assume 80% charger efficiency, 80% battery efficiency, 85% inverter efficiency--you get:

0.80 * 0.80 * 0.85 = 0.54 end to end efficiency

So--If you have loads that can share the battery charging and run directly from the Honda (say you run the genset in the evening)--you may end up using less fuel because you avoid the triple conversion to used stored power.

-Bill

stephendv · June 2010

Re: Lower priced RV system

You could also consider getting a propane conversion kit for the Honda to save some $ in the long run and not have to mess about with nasty petrol (gas).

dwh · June 2010

Re: Lower priced RV system

Bob_D wrote: »

I need about 100' of wire to run to the closest sunny spot for the modules, so MPPT seems to be cost effective for me. At 24V with 10 gauge wire the voltage drop should be in the 2% range for the normal operating amps, if I run a separate cable to each pair of panels, which would be wired in series, then parallel the two at the controller. I would properly fuse everything also. That would keep my wire costs in the $100 to $130 range.

If you are doing that run outdoors, then what sort of wire were you planning to run? $130 seems a little on the low side to me. THHN is one of the cheaper wire types, and even that would run you *at least* 150 for a 500' spool. Any other wire type (such as outdoor rated), and/or buying by the foot will cost even more.

You might be able to shave some off of that by finding a couple of used 100' 10/2 contractor extension cords. The go for about 80-120 bucks new, and I've often seen them used as low as 30 bucks. But even at 50 each they are still a cheap source of decent wire.

And they also come with a handy little doohickey called a "ground wire".

For a 220w portable rig like you describe...I'm not sure MPPT is really worth it. What is the difference in watts harvested by spending 300 on an MPPT charge controller rather than spending 100 on a PWM?

I mean; Sure, if you absolutely need to squeeze out every possible watt, then MPPT is the way to go - especially for smaller systems. But the difference in cost vs. the difference in harvest may not be worth it for a small portable RV system. You might see a greater boost in harvest by simply going out and re-aligning the panels to the sun every couple of hours (my uncle would have called that the "Armstrong" (or was it Strongarm?) tracking system

).

For a *fixed* RV solar system - i.e., permanently flat mounted - MPPT is almost certainly worth it, but for what you've described I'm not so sure.

Lower priced RV system

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