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vidaliaman
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# Posted: 30 May 2017 02:47pm
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i own 2 55 watt systems, both with 7 amp controllers, 2 identical 12v RV batteries, can i simply hook both 12volt batteries (pos to pos, neg to neg), keep both controllers on each of their own batteries? would the controllers mess each other up?
thanks dave
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ForceFed70
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# Posted: 30 May 2017 03:22pm
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Yes you can merge. The controllers will likely be OK but I could see them messing each other up.
I'd be tempted to buy a single 10A charge controller. They're cheap.
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Steve_S
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# Posted: 30 May 2017 03:29pm
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batteries can be linked YES, 2 controllers will conflict & cause problems. One controller that can handle the panels (12v / 55w ea). Cheapest controllers are PWM but they really are not that good, a low cost MPPT controller will gain you more usable power input and potentially allow you to expand more if you plan for that. Note though that most MPPT controllers are designed for 24/36v panels (the bigger 200+W panels) but some do handle 12v <100w panels.
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ForceFed70
Member
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# Posted: 30 May 2017 04:40pm
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For 110W worth of panel a MPPT controller is a waste of money. Cheaper and more effective to buy additional panels and use a basic PWM controller vs buying an expensive MPPT controller.
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vidaliaman
Member
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# Posted: 30 May 2017 08:03pm
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so instead of two 7 amp controllers get ahold of one 10amp charge controller? is there a such thing as a controller giving the voltage in the batteries? or is that found in the inverter, sorry maybe dumb question but learning
dave
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ForceFed70
Member
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# Posted: 30 May 2017 08:26pm
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Yes, use 1 10amp controller.
What do you mean by "Controller giving the voltage in the batteries"?
Do you mean a controller than tells you what the battery voltage is? If so - the answer is Yes, some controllers will tell you that info along with other info like charging amps.
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creeky
Member
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# Posted: 30 May 2017 08:46pm
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There is no difference to the batteries where the power comes from. DC is power source agnostic.
Two controllers into two parallel connected batteries is not a problem.
Now 2 inverters you can't do. AC has a sine wave that has to match.
There are very cheap mppt controllers now. Victron springs to mind. But for your system. You're unlikely to get any benefit.
For those who would like a few more watts. Amazon has the Victron BlueSky 75/15 for $100. There's a 75/10. Probably cheaper.
Some controllers will tell you the battery state of charge. The Victron has bluetooth so see the battery voltage on your phone. But thats another 60 bucks I think. Others have a display built in.
Man. Amazing how cheap solar stuff is getting. And how good.
Remember too. MPPT lets you run higher voltage panel sets. So you save money on the solar panel. (a 200w panel at 24v for 130 vs 2 100w panels at 12v for 130 ea. and you paid for the mppt controller right there).
Take your time on this. Source your options carefully.
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ICC
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# Posted: 30 May 2017 09:50pm - Edited by: ICC
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Quoting: vidaliaman can i simply hook both 12volt batteries (pos to pos, neg to neg), keep both controllers on each of their own batteries?
Two or more charge controllers into the same battery bank is frequently done. No problem. We have three arrays with one facing east, the second facing south and, yes, the third facing west. Each has its own Outback charge controller. They feed the same battery bank. You might try facing one panel set a little west of south and the other a little east. You may get more total watt-hours input to the batteries. Even if the panel sets all face the same direction it is not a problem. Due to internal variables one controller may switch from bulk to absorb or absorb to float a little later than the other, but that is okay. Nothing will get damaged.
Technically you can also pair inverters, BUT the inverters MUST be designed for that purpose, just like compatible inverter generators may be paired (EG two Honda EU2000i in parallel). Pairing most inverters will result in at least one being toasted.
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creeky
Member
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# Posted: 31 May 2017 09:22am
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Technically you can find inverters that have phase matching. Victron, Schneider were among the first to do this. You must match both the inverter and the size for their models.
The Schneider SW looks really good. You can "only" put two in parallel. But that's 8kw. The Victron's go 4 units. You can go to 60kw. Which is crazy.
Some of the chinese inverters are coming with phase matching.
See this article for more detail. From the university of Ohio.
I am becoming something of a fan boy for the new DSP inverters coming out. Helios from CNBOU are pretty cool. Too bad only the 24v is shipping.
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Nate R
Member
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# Posted: 31 May 2017 10:38am
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Check your panels. a 55W "12 V" panel rated at 17.5V might be only 3.14A. x2 and you might be able to put both panels on 1 7A controller.
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