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Old 06-13-2018, 12:27 PM   #11
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I got a pair of these batteries............
https://www.interstatebatteries.com/...ts/gc2-ecl-utl
Those are lead-acid correct? What is the maintenance like?
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Old 06-13-2018, 03:04 PM   #12
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Yup. Lead acid. I guess check the water level every now and then is all that is needed.
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Old 06-13-2018, 03:49 PM   #13
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You mentioned possibly getting three panels. Odd numbers of panels can be problematic. The only way they can be connected is in series, then their combined voltage is much too high for a PWM charge controller (you'll end up wasting more power than you use), and unnecessarily high even for a MPPT controller (the greater the voltage stepdown, the more heat it makes and the lower its overall efficiency). If you have an even number of panels you can wire them in parallel, and this will avoid the problems I mentioned, plus it makes the array less affected by shade on just panel - if one panel is shaded, a series array produces very little power, but a parallel array produces all the power except that from the shaded panel. Parallel makes more sense on a bus or boat where the panels are probably not ideally orientated to the sun most of the time. The advantages of series panels are irrelevant with a bus or boat.

As others have said, first calculate your loads, then determine how much battery capacity is needed to support them, then how much solar power is needed to correctly charge the batteries.

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Old 06-13-2018, 04:02 PM   #14
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Originally Posted by Iceni John View Post
You mentioned possibly getting three panels. Odd numbers of panels can be problematic. The only way they can be connected is in series, then their combined voltage is much too high for a PWM charge controller (you'll end up wasting more power than you use), and unnecessarily high even for a MPPT controller (the greater the voltage stepdown, the more heat it makes and the lower its overall efficiency). If you have an even number of panels you can wire them in parallel, and this will avoid the problems I mentioned, plus it makes the array less affected by shade on just panel - if one panel is shaded, a series array produces very little power, but a parallel array produces all the power except that from the shaded panel. Parallel makes more sense on a bus or boat where the panels are probably not ideally orientated to the sun most of the time. The advantages of series panels are irrelevant with a bus or boat.

As others have said, first calculate your loads, then determine how much battery capacity is needed to support them, then how much solar power is needed to correctly charge the batteries.

John

Good info.

Also, many of the popular MPPT controllers have a Max input of 150 volts or less.

When you factor in a margin for cold weather (1.25 x Voc) you can run out of headroom with three series panels as Voc approaches 40 volts.

I am running 300 watt panels and cannot, safely, run three in series as the Voc of the panels is 44.8 volts.

If you added a fourth panel you could run 2S2P.
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Old 06-13-2018, 04:14 PM   #15
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I bought the Renogy 200 watt kit on Amazon and using two 6v golf cart batteries wired in series for a 12v system. My entire bus is wired for 12v except the fridge which is run off a 1500 watt pure sine inverter. I have no complaints after 5 months of use.
So if your whole bus is wired for 12v, what do you do for outlets for other things like TVs, or laptop chargers or computers, etc, do you run an inverter in each 12v socket you need to hook up 120v appliance or do you have a few 120v outlets coming from inverter?
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Old 06-13-2018, 04:30 PM   #16
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So if your whole bus is wired for 12v, what do you do for outlets for other things like TVs, or laptop chargers or computers, etc, do you run an inverter in each 12v socket you need to hook up 120v appliance or do you have a few 120v outlets coming from inverter?
I detailed the things I run in my post: http://www.skoolie.net/forums/f49/so...tml#post275116

Short story is, run DC powered things whenever possible, treat your inverter as a last resort. Inverters waste lots of power on inverting, and every watt you don't waste is a watt you don't have to generate and store. Laptop and phone chargers are absurd things to run from an inverter because you're converting DC to AC and right back to DC, you'll use twice as much energy as powering it directly.
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Old 06-13-2018, 04:47 PM   #17
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I detailed the things I run in my post: http://www.skoolie.net/forums/f49/so...tml#post275116

Short story is, run DC powered things whenever possible, treat your inverter as a last resort. Inverters waste lots of power on inverting, and every watt you don't waste is a watt you don't have to generate and store. Laptop and phone chargers are absurd things to run from an inverter because you're converting DC to AC and right back to DC, you'll use twice as much energy as powering it directly.
That I definitely understand but will I have to spend much more on getting 12 volt TVs and how would I go about using 12v for my laptop charger? Would I have to run a converter on a specific circuit to plug into laptop? I guess some newer laptops now are charged by USB 3.0 or C type type so I could try to go that route. Any advice would help yes if I could reduce e the amount of 120v and keep that only to a couple things that would be ideal.
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Old 06-13-2018, 05:08 PM   #18
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In my post there's a link for my laptop's charger. It is compatible with most laptops that use 18-20v and includes a bunch of plugs. You can look at your current laptop charger to see what it's voltage is, and you can write the manufacturer of the adapter to ask if it's compatible for sure.

Many TVs are actually DC appliances too. If your TV has a power adapter like a laptop, you can do the same type of thing to run it directly from DC power. Some TVs are actually AC appliances and there are no shortcuts for them.


We also have a USB C laptop charger that plugs into a 12v outlet, https://amzn.to/2l9e0Zq which the GF uses for her Samsung Chromebook Plus.

With just a little effort you can run any low amperage DC device from your 12v source, at any voltage. Step-up and step-down converters can be very efficient, way more than using an inverter.
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Old 06-13-2018, 05:26 PM   #19
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In my post there's a link for my laptop's charger. It is compatible with most laptops that use 18-20v and includes a bunch of plugs. You can look at your current laptop charger to see what it's voltage is, and you can write the manufacturer of the adapter to ask if it's compatible for sure.

Many TVs are actually DC appliances too. If your TV has a power adapter like a laptop, you can do the same type of thing to run it directly from DC power. Some TVs are actually AC appliances and there are no shortcuts for them.


We also have a USB C laptop charger that plugs into a 12v outlet, https://amzn.to/2l9e0Zq which the GF uses for her Samsung Chromebook Plus.

With just a little effort you can run any low amperage DC device from your 12v source, at any voltage. Step-up and step-down converters can be very efficient, way more than using an inverter.
I'm guessing if I run a separate 12 volt system that is separate from the bus batteries would I still bond negative to the bus chasis Even if the negative on the bus batteries are already bonded there or would that create an issue?
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Old 06-13-2018, 06:01 PM   #20
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I use a common ground on mine, my house batteries have their negative side attached to the chair rail. You can get some electrical noise that way, but outside of audio amplifiers you'd be hard pressed to notice it. I only run a single wire to my outlets and use chassis ground for everything.
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