800 watt 48v solar w/225ah 48v bank question

[zman7458]

Hello forum, My name is Phil. I've been an electrician for 36 years, and an IBEW member for 15. I'm not an expert on all things electrical, but I know my way around most of the math. I will be wiring the money for my 2014 37MD outlaw next Wednesday and picking it up on Thursday if all goes well. Then my wife, my eldest son and I will be hitting the road around December 15th or so. So that means I will have 4 months to get the RV ready for us to go. My first project with the RV is to convert the storage bay between the generator and the wet bay into my solar system. I have drawn up a rough schematic of how I would like to put it together, but since solar is a relatively new thing to me I would like to have you take a look at my design and see if you spot any design flaws that I may have overlooked. Plus I have a couple gray areas I would like to discuss if I may. I've done my due diligence on the net to research these items I have misgivings about, but I haven't found any definitive answers as yet. Okay first off if you notice my solar charger is of necessity also feeding into the input of my inverter and I was wondering if this setup would constantly keep the charger in a bulk charge state and if so how can I prevent that?
also I have added as an afterthought mainly a 48vdc to 12vdc converter to feed my 12vdc house feed. My question is, is that the proper way to go about that or should I just leave the existing 12vdc system in tact to take care of that system, and if I do that will it be enough to boondock for extended periods of time (my main concern), Thank you in advance for your time and consideration , Phil.

[nothermark]

FWIW - 50 years or so of pushing electrons in other fields - I see what you are doing and see the point of 48 down from the roof. I would be looking for a controller that took 48 VDC in and controlled a 12 VDC battery bank. Alternately I would put 1 decent size battery on the 12 VDC side. The reason is that you will need to keep the 12 VDC size intact on your RV to satisfy the lighting, controller boards, and motors in the system. I expect you will have more than sufficient current capacity for the first two loads off the 48 to 12 VDC converter. I don't expect you will have surge capacity for the motors. A battery is probably cheaper and easier than a super capacitor to handle that.

The other issue will be when not on solar you will need to do a 12 - 48 VDC to charge the big battery bank while a small 12 V battery will float off the alternator or shore cord of the normal setup as both a useful load and surge source.

In short I can see how to make it work and why you might want to go that way but I would probably stay with the existing 12 VDC main battery setup unless it was a clean sheet install. If that was the case I would consider 48 VDC for the main battery with the added 12 VDC battery. I might revise that if I had a stack of controllers in the garage. ;-) Good luck and let us know how it works out.

FWIW you also might want to do yourself a favor and scatter some of those $10 or less small digital meters around your system. Nothing beats data for watching how well things are working.

[drdarrin]

Is the diagram for your solar array right? That looks to me like you've got it wired for 2 12v banks @ 24A each. After the combiner, that would give you 24V @ 24A wouldn't it?

But I'm certainly no expert.

[pasdad1]

I think you should get a Solar controller that takes the high voltage from the solar and charges a 12 volt battery bank. I don't see the benefit of a 48 volt system, as the inverter, and converter/charger are all much more expensive, plus your choices are few because this is very uncommon. Any efficiency gained is eaten up by having to convert it back to 12 volts to run all the systems in the coach which need 12 volts.

I would look at the Morningstar TS-MPPT-60 controller. It can take in your 48 volts from the solar panels and step it down to charge a 12 volt battery bank. You want your engine alternator to be able to charge your 12 volt battery bank like it was designed to do.

http://www.morningstarcorp.com/wp-co...SMPPTdsEng.pdf

[zman7458]

So you would leave everything alone except, get rid of the converter and change the bank to series parallel and lower my voltage to 12vdc up my capacity to 900ah in doing so. I won't have to change my TrakMax 30L LCD MPPT 30A Solar Charge Controller Regulator + Temperature Sensors + Remote Meter, 12 24 48 Volt will step down to 12vdc automatically, but I will have to go with the AIMS Power PICOGLf0W12V120VR 3000 Watt 12V Pure Sine Inverter Charger which will also keep my bank charged when on shore power. so then everything will be square (I think). what about the solar charger staying in bulk charge with the inverter pulling on it?

[zman7458]

Originally Posted by drdarrin

Is the diagram for your solar array right? That looks to me like you've got it wired for 2 12v banks @ 24A each. After the combiner, that would give you 24V @ 24A wouldn't it?

But I'm certainly no expert.

hmmm no, my solar panels are 12vdc each wired 4 in series with two banks paralleled, and my batteries are 6vdc wired with 8 in series both of which should equal 48vdc.

[zman7458]

I'm trying to keep the system open ended so I can expand without having to swap components out if it seems like a bit of overkill on a couple things. And I just want to thank you all for giving me another set of eyes, your suggestions are brilliant. I suspected I was coming to the right place for this discussion.

[zman7458]

Originally Posted by pasdad1

I think you should get a Solar controller that takes the high voltage from the solar and charges a 12 volt battery bank. I don't see the benefit of a 48 volt system, as the inverter, and converter/charger are all much more expensive, plus your choices are few because this is very uncommon. Any efficiency gained is eaten up by having to convert it back to 12 volts to run all the systems in the coach which need 12 volts.

I would look at the Morningstar TS-MPPT-60 controller. It can take in your 48 volts from the solar panels and step it down to charge a 12 volt battery bank. You want your engine alternator to be able to charge your 12 volt battery bank like it was designed to do.

http://www.morningstarcorp.com/wp-co...SMPPTdsEng.pdf

The one I am going to use is very versatile it will take up to 150vdc pv and output 12,24 or 48 vdc automatically. unless I misunderstand you.

[zman7458]

Does anyone know where I can get an electrical service manual for this rig? I've been looking around the net and I can't find anything.

[pasdad1]

Originally Posted by zman7458

The one I am going to use is very versatile it will take up to 150vdc pv and output 12,24 or 48 vdc automatically. unless I misunderstand you.

I have not heard many people using the windy nation controllers....the most popular are the Morningstar, Outback and Midnite Solar brands. Your model seems cheap to me at $199. You should take another look at the link for the Morningstar I sent previously. It is also wise to get a controller with much more capacity than you need, so you can upgrade panels in the future if you desire. Instead of a 30 amp, consider the 45 or 60 amp instead.....it lets the controller disappear heat better, and will let you add wattage in the future.

[Timon]

Running a 48V battery system and inverter can be very efficient compared to 12V. You don't need to run those very heavy wire gauges cables that 12V systems need.

As far as inverter cost they aren't much different than 12V if the wattage is about the same however most 48V inverters are high wattage usually 3K or more.

However there are down sides. You need a 48V alternator if you want to charge while driving and you can't jump start your self from the 48V pack. You need a 48V to 12V converter for the 12 systems.

So if you know what your doing then go for it.

[zman7458]

Originally Posted by pasdad1

I have not heard many people using the windy nation controllers....the most popular are the Morningstar, Outback and Midnite Solar brands. Your model seems cheap to me at $199. You should take another look at the link for the Morningstar I sent previously. It is also wise to get a controller with much more capacity than you need, so you can upgrade panels in the future if you desire. Instead of a 30 amp, consider the 45 or 60 amp instead.....it lets the controller disappear heat better, and will let you add wattage in the future.

Point taken, I've just done some checking and I don't like what I see about windynation. I looked into the Morningstar and it seems to be a superior product and company. Once again I find myself thankful for having posted my question here. Thank you very much!

[zman7458]

Originally Posted by pasdad1

I have not heard many people using the windy nation controllers....the most popular are the Morningstar, Outback and Midnite Solar brands. Your model seems cheap to me at $199. You should take another look at the link for the Morningstar I sent previously. It is also wise to get a controller with much more capacity than you need, so you can upgrade panels in the future if you desire. Instead of a 30 amp, consider the 45 or 60 amp instead.....it lets the controller disappear heat better, and will let you add wattage in the future.

The Morningstar TS-MPPT-60 Tristar Mppt 60 Amp is very definitely superior in every point plus it has some very nice data tracking features. Thanks again.

[pasdad1]

Another thing to think about is your placement of solar panels, and parallel vs series wiring. Even a TINY shadow cast upon a panel wired in series with other panels, drops the output of the entire string to near zero. Even a shadow from a roof air conditioner, or antenna. Wiring for 48 volts requires 4 panels to have PERFECT sun (not even a tiny shadow) or you get very little from that entire string of 4. Having four groups of 24 volts wired in parallel, would be something to try, instead of two groups of 48 volts, you will only know once you see the placement, and what obstructions on the roof can cast shadows as the sun moves.


Good video on the impact of shading and parallel vs. serial connections at

https://www.youtube.com/watch?v=1qD3mN8VotQ