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Old 12-09-2016, 03:44 AM   #11
Mini-Skoolie
 
Join Date: Dec 2016
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Thanks everyone. Appreciate the feedback and will include in my plans
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Old 12-09-2016, 07:05 AM   #12
Skoolie
 
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Hmm I do not think all of this makes sense.

micro inverters are used in grid tie systems unless you get really fancy stuff. So on a bus that is already useless.

Power opimizers are system that short shaded panels out of a series loop so that they do not affect the whole string, mostly used in high voltage direct grid tie systems.
Not very usefull for busses either.

you first have to specify how many watt of solar you are planning to install, then you can decide if it is worth your while to go to higher voltage inverters. 48 volt inverters can be about 10% more efficient.

Lead acid batteries are very inefficient in charging the last 10% of charge because of the gassing. They need to gass to avoid sulfate buildup. So you will loose a lot of solar power to just charge the batteries to the fill 14 to 15 volt.

It is more efficient to go with lithium . That is way better / efficient for partial charging and also will have longer lifetime with being partial charged.

If you go with multiple small solar panels you can get real cheap mppt charger for 12 volt at 5 to 8 amp about $$8.
So it might be possible to use 75 watt panels and give each a cheap mppt.
Larger panels are often cheaper. ebay is full of new $.55/watt panels
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Old 12-09-2016, 07:28 AM   #13
Mini-Skoolie
 
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I'm shooting for 2400 - 3000 watts of solar charging a 48v system with 200amp hour LiFeMnPO4 storage array. System will provide ample power as we build an off-grid home. It will run/charge power tools, air compressor, mini-split a/c unit, etc. Since using a mini-split, there will be ample space on the roof. Additional requirements for multiple telecomms options as I must always be connected to the internet. 3.5kw gennerator will provide back up power if needed due to heavy work load during the day or series of days with limited sun.
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Old 12-09-2016, 08:34 AM   #14
Skoolie
 
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Engine: 7.3 powerstroke
Sound like a good plan . we have 7200 watt on our barn with battery back up. 2 outback 3648 grid tie inverters and our 48 volt forklift doubles as battery bank.
Where are you located?
On our bus I am installing as we speak 3*300 watt panels at 24 volt. All small users .lights. Fridge and diesel heater are 12 volt as to avoid conversion losses. Then we have an older style sine inverter for short term load as induction cooking and microwave.

In our off grid cabin I wired for 48 vdc and 120 ac. There I use thin film panels. They are low efficiency but high voltage 100 volt range and take partial shading very well. They are also cheap. If you have enough space and do not need high efficiency then that could be an option.
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Old 12-09-2016, 09:12 AM   #15
Mini-Skoolie
 
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Right now I'm in VA, but we will be going mobile in a few years (teaching online classes and picking up short term contracts). Plan is to build a home base and travel as we please.
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Old 12-09-2016, 09:47 AM   #16
Skoolie
 
Join Date: Jun 2016
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PappySki, why do you want a 48V system in a bus?

John
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Old 12-09-2016, 10:34 AM   #17
Mini-Skoolie
 
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48v system lets me run a 48v mini-split a/c system and it will match the system installed in our residence. Mini-split will allow me to have no large components on the roof which means I can maximize my solar collection. 48v a/c means I have no conversion loss and they are significantly more efficient and effective than any other DC A/C option. This will be an expensive system, but it will meet our short and long term requirements.
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Old 12-09-2016, 11:00 AM   #18
Skoolie
 
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Engine: 7.3 powerstroke
Great plan, do you want all your solar on your bus or are you planning to put some on your house. How much PV on the bus?

We are using lithium scavenged from Nissan Leaf and chevy volt. These have the longest life if you do not exceed 4.05 to 4.1 volt. Of coarse that gives you reduced capacity.
Our 48 volt house outback inverters are better of with a slightly higher voltage so 13 or better 14 cells in series.
I used to be a big fan of lead but now there is no way beside the use as starter battery.
Another good possibility especially with lithium is parallel stabilization that is charge to the 4.05 or what ever you decided and if there is more sun divert that load to whatever. If you have engine heater plug then that is good. No use in throttling back solar panels better use the energy in something even if that is not the most efficient use.

What online teaching are your doing?

Later j
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Old 12-09-2016, 11:17 AM   #19
Almost There
 
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hrmm... Micro inverters are pretty much always grid tie, which only make sense on a house grid connected system, EXCEPT that some power inverters such as Victron and *shudders* power jack inverters will recharge the batteries if connected to grid tie micro inverters. But, I wouldnt trust anything but a Victron or similar high dollar inverter/charger to actually apply proper charge curves to the batteries and not cook them. And, if your inverter goes out, you lose solar altogether.

Have you considered running each panel to a separate MPPT charge controller? Then if a panel gets shaded, all panels are still running at their max power point, including the shaded one.

You can parallel panels for sure, a shaded panel will slightly drop it's max power potential voltage below that of the other panels though, causing a greater power reduction on that panel than if it had a MPPT controller on it... but maybe that is a small enough loss that it's not worth the expense?
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Old 12-09-2016, 11:34 AM   #20
Mini-Skoolie
 
Join Date: Dec 2016
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How much on the roof really depends on the bus we find that we like. I should be able to put between 2400 and 3000watts...though I was looking at 12v panels when I did my measurements. I haven't had a chance to look at the dimensions of higher voltage panels.

What I'm teaching on line is tied into my three year plan. I'm currently working on my PhD in Cybersecurity.
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