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Old 03-29-2020, 12:51 PM   #1
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Solar Questions as Usual

Hey All, new to the forms, happy to be apart of the community! Short summary, My girlfriend and I purchased a 1970 GMC Buffalo that was previously converted and we are gutting and renovating it. We need to be living in it full-time within the next couple weeks. I read through as many forums and threads as possible and still can't seem to figure it out. I have a Panel that was left over from a residential Install. It's a 360W Panel(attached is the spec sticker). And I recently acquired 6 6V golf cart batteries. My plan was to wire them paired in series to get 36V. I have not purchased a charge controler or inverter yet. I do plan to run about 1500 watts in the future with a mini split for summer months. The bus came with a 2500w inverter that I will only use when needed, but I plan to have a smaller inverter for smaller stuff like Led lights and laptop chargers, stove igniter, etc. Anyways I'm looking for my best most efficient option. If 36V is more than enough I'll drop it down to 24V or.would.i be better off running 48V. I do plan to get another panel or two identical to my current one in the future but for now I need some power.


What's my best option here? This is the link to my batteries https://www.trojanbatterysales.com/product/11073/


All input is appreciated, thanks!
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Old 04-01-2020, 11:43 AM   #2
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I can't tell you what you should do... but I can tell you my thought process.


If you want to maximize efficiency, then the bank voltage should be as close as possible to the panel voltage. You panels are 48V, so for max efficiency your bank should be 48V too. But there's more to consider than just efficiency--compatibility, ease of use, safety, money... those are all important to consider.


For instance, most RV/auto appliances/gadgets/devices are going to be 12V. There's plenty at 24V, and the 48V range would be more geared toward off-grid residential. Which would totally work too, especially if you're planning on treating your bus as an off-grid home. Or, if you want to treat it more like an RV for trips, then I think a 24V bank would work better.


I don't think a 36V battery bank would work here, because that's kind of an unusual voltage to find the right appliances/gadgets/etc... So if you wired your six 6v batteries in series to get 36V, I can't imagine you'd have a whole lot of amp hours capacity. You'll have to end up getting some batteries at some point. And more solar panels.



But, in my opinion, a 24V bank would be ideal, followed by a 48V bank, but I don't know what your financial situation is, or what your desired end state is. Keep in mind that this is not advice, I'm not an electrician, I don't even have my panels installed yet, this is just me repeating what I've gathered from this forum and from other life experiences.
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Old 04-01-2020, 05:19 PM   #3
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Right - 36 volt bank will just create challenges.

Arguably, the voltage of the panel/array does not really matter. A good MPPT charge controller will deal with the difference. Yes, there is some efficiency to be lost... read on. The benefit of a higher voltage array is smaller gauge cables to the controller.

You have far more items pulling power out of the battery bank (than putting power in). Many of those components will be 12 volt (that's the only choice for some things). You may be able to find a good many in 24 volt (water pump, lights, etc.), very few will be 48 volt. So, you are likely to have at least one step down converter if you go with 24v or 48v. The biggest advantage, IMO, to a higher voltage bank is smaller gauge wire or the ability to run longer distance with less voltage drop (for a particular wire size).

If you plan to run very high current draw items the higher voltage bank is a positive. However; all lead-acid chemistry batteries have their limit.

It's always an exercise of balancing the pros and cons...
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Old 04-01-2020, 07:08 PM   #4
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Thank you for your input. I can pick up 2 more batteries and make it 48v. What's your opinion on these batteries?

I will be mostly running a small fridge, water pump and during summer months a small ac pulling about 500w. Other than that a TV LED lights, Laptop chargers etc. For now. I would like to design a system that could handle a small AC for longer periods of time.

The electric will be setup in the middle of the bus, and ill be running 12 awg PV wire to the charge controller. Between the batteries I haven't figured out the size just yet.
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Old 04-01-2020, 10:19 PM   #5
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Hold on.....

That one panel will not charge a 48volt battery.

Most popular charge controllers that I have seen support 24v and 48v but not 36v. 36v will limit your choices.

You also want to make sure that you are able to charge your batteries at C\12 minimum to avoid sulphating your batteries.
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Old 04-01-2020, 10:53 PM   #6
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Even though your hands are full and time is limited, it would be well worth learning all you can from the solar gurus on the Northern Arizona Wind & Sun forum. The experts there definitely know all there is to know about solar - if they say do something (or don't do something), you'd better heed their advice! I think your plan at this point is fraught with problems, to put it mildly. FYI, I have just over 2kW of tiltable solar for a 12V system (actually two 12V systems running in parallel), so yes, 12V can work for larger systems, but there are many considerations to make it work well. Forget about 36V!

And welcome to the world of 2-stroke Detroits. They are very different than 4-stroke engines so you must drive them the right way, and their care and feeding is also quite different. Don't lug them, use straight 40-weight CF-2 oil and nothing else, and don't lug them.

Good luck.

PS - don't lug them.

PPS - don't lug them.
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Old 04-02-2020, 08:21 AM   #7
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10-4 I'll check out their forums. Running 12v in parallel wouldn't be a bad idea. 36v is out the door!



I'm using straight 50 weight oil, and thanks for the tip. I will not lug it.
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