Charge controller question.

Stevireno

Hi all, first post...   Hoping for a little advice...  

We have an off the grid cabin, previous owners have 4 40 watt 12 volt panels that came in a group, all wired together to a 12 volt charge controller that is built into the wiring.  Its one of these package deals, I'd have to cut the wires to remove the charge controller.  I have 4 100 watt panels (non 12 volt) that I want to connect using a MPPT to the same 12 volt battery bank that the 4 40 watt system is connected to.

Is is ok to simply connect the 400 watt panels hooked up to the MPPT controller to the battery bank?  Better to abandon the 160 watt 12 volt system and purely use the 400 watt system?  Thanks in advanced, sorry if I missed anything...


Steve

BB.

Welcome to the forum Stevireno.

Much of this depends on the Vmp and Imp of the solar panels--"12 volt" panels tend towards Vmp~18 volts--And you can parallel your 160 Watt "array" with your 100 Watt panels without issue as long as all are Vmp~18 volts. As you parallel solar panels (typically three or more parallel strings), each string should have its own fuse/circuit breaker to reduce the chances of a short circuit in your array causing a fire. The 40 Watt panels would need a different size series fuse (typically) than the larger 100 Watt panels.

Why do you want and MPPT type charge controller? Generally, they are more expensive and best used when you have longer distances from the array to charge controller+battery bank (save money on copper wiring).

Or--In the case where you have larger solar panels (typically >175 Watt panels) that have Vmp~30-36 volts charging a 12 volt battery bank (MPPT controllers can take "high voltage/low current" from the solar array and efficiently down convert to "low voltage/high current" needed by the battery banks

In any case--It is a good idea not to buy anything just yet until you tell us more about the loads you want to support, the size/type of battery bank (volts, amp*hours, flooded cell/agm/etc.)--Basically we would like to help you review your present system and what is the best way to go forward.

Many times, it is easy to get ahead of yourself and by components that really do not meet your needs (waste of money).

-Bill

Stevireno

Hi Bill, thanks for your time and help.

My battery bank consists of 2 100ah sealed lead acid batteries.  I have this wired into the 12 volt fuse-box and I have an inverter that is plugged into the 115 fuse-box.  Everything is powered bye the batteries, I occasionally disconnect the inverter from the 12 volt and connect the plug to a generator and run the 115 volt off the generator and use the generator to charge the batteries through a standard 12 volt battery charger.


 I have gotten ahead of myself and I bought a charge controller, so I am now the proud owner of a  MPPT 10 amp CC

http://www.amazon.com/Tracer-Tracer1210RN-Charge-Controller-Regulator/dp/B008KWPGS6?ie=UTF8&psc=1&redirect=true&ref_=oh_aui_search_detailpage

I believe the panels put out 60 volts, which is why I assumed I needed the CC to alter the voltage to 12 volts.  We use the cabin for about 3 days, running very low amps, battery voltages drop to about 12.1 at the lowest, then when we are not there for the remaining 4 days, the solar panels charge the 2 100ah batteries so we can start again the following weekend.

Thanks again for your help, let me know if you need more / different info!

-Steve

WaterWheel

While I'm not the most knowledgeable guy here I can tell you that your 10 amp charge controller is only capable of handling about 120 watts worth of solar panels (by the book) but considering the .77 derail rate you may be able to get away with up to about 150 watts worth of panels using that controller with a 12v battery.

Assuming you only use the 400 watts worth of panels going to a 12v battery bank you'd need at least a 30 amp charge controller.

As Bill suggested it's best to consider your loads before designing the system.      It sounds like your loads are very small and you may not need 400 additional watts worth of panels.

vtmaps

Stevireno said:

Is is ok to simply connect the 400 watt panels hooked up to the MPPT controller to the battery bank? 

Yes.  with certain caveats... you didn't tell us what type of sealed batteries you have.   It is possible that 560 watts of panels could push excessively high charging current into a 200 ah battery bank... depends on the batteries, some sealed batteries can handle it.

Stevireno said:

Better to abandon the 160 watt 12 volt system and purely use the 400 watt system?

not necessarily.  Generally you can have as many controllers as you wish hooked up to a single battery bank.  Each controller must have its own array. 

I think BB Bill's reply was based on an assumption that you were trying to put your old and new panels together on a single controller.  If I understand your question, you are asking if you can use two arrays each with their own controller.

--vtMaps

Stevireno

OK, to clarify, I do have 2 separate controllers, one is the built in controller to the 160 watt system, and one is the MPPT unit that I want to hook up with another set of panels that put out more voltage.  I'm assuming that after the charge controller, the voltage will be 12 from both controllers to the battery and there is not risk, but I wanted to throw it out here.

Here is one of the batteries...

https://www.amazon.com/gp/product/B00S1RT58C/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

the other one is a basic marine deep cycle battery that was there when we bought the place.  

-Steve