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Old 08-10-2018, 12:40 AM   #1
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Solar...

... as it has been discussed already in this forum...

I do have a few questions that I havent found answers to yet so my hope is that one of you can help me out.

We are converting a 2005 Blue Bird right now. I already have a few quotes for a solar system.
I want to have at least 800W solar panel and a big enough battery bank, I was thinking 400Ah with four 12V AGM batteries. After receiving a few quotes the forth person told me that the solar array will not be big enough to charge that size battery bank sufficiently. Nobody else did even mention it.
Is that really true?

Another quote I got had two 400W kits with two 30A charge controllers combined into one 400Ah battery bank (that quote was the cheapest). Does that make sense? They say they have no 60A charge controller...

Can anyone suggest a system with the following parameters:
- at least 800 W solar power panels
- 400Ah battery bank AGM batteries
- 3000W inverter/charger pure sine
- shore power hookup 30 and 50amp
- all wiring, mounts and combiner boxes fuses, fuse boxes and misc. items needed

Thank you everyone for helping out.
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Old 08-10-2018, 07:02 AM   #2
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Howdy and Welcome thebusfor.us!

Without details, it is really hard to say whether that statement is true or false. A lot depends on where you are located (solar insolation), how much power you are consuming during the day (produced by the panels but being used instead of put into the battery bank), panel efficiency (how they are mounted), etc.

In rule of thumb terms, you should have a solar array that produces 13% of the total battery bank capacity. A 400 Ah bank would be matched to an array that is producing 52 Ah (of charging current so up around 14 volts). That would be something around 800 watts but have to take losses into account. All that said, you need to fully charge your battery bank. Insufficient charging (less than 100%) will, given enough time, damage the battery bank. All those numbers work fine for a 'fixed' installation (off grid home, for example) but for an RV/bus, they don't work so well. Sometimes due to insufficient space on the roof for panels, moving from high insolation area to low, shading (mountain/trees), and varied electrical consumption. Many folks use a generator to fill in the void. I'm not a fan of generators but I get that they are sometimes necessary. Run it for a bit in the morning to bulk charge the battery and then let the solar complete the charge over the course of the remainder of the day.

Depending on how you mount your panels (flat or tilt) and where you are located, you'll likely see something between 50-80% of rated output. So, an 800 watt array may only produce 400 watts which is probably not going to fully charge your battery bank (if it is down near the bottom (50% SOC).

"Networking" charge controllers is common to support a large array. One way you can "cheat" is by going with a higher voltage battery bank. Most charge controllers are rated by output amperage regardless of voltage. So, a 60 amp controller will output a maximum of 60 amps to a 12V battery, 60 amps to a 24V battery (twice as much power) or 60 amps to a 48V battery (four times as much power). There are cons to the approach, of course...
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Old 08-11-2018, 08:55 AM   #3
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Thank you JDOntheGo.
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