Georgia on my mind

[russ]

I just had a 1518W peak day today and I think that is pretty good for only having panels rated at 1422 and it rained most of the day.

Cloud edge effect - momentary and meaningless.

[HOASUNBuster]

Interesting hybrid system you have there. I am not sure why you want to add the complexity of switching so you can use your grid tie solar panels to charge your batteries. Also running any loads off batteries is much more expensive than using the power from the Utility and charging batteries from solar is more expensive than using a standard battery charger.

The batteries may be your idea of an emergency backup power but with a battery system you still need a generator of some kind. That generator can support you during a power outage and charge your batteries when the power goes out.

IMO adding the wiring, switching and charge controllers seems to be an added expense that probably will never pay for itself.

SunEagle, My first effort was to have some battery backup that was not dependent on a natural resource that cost me money to actually run beyond the cost of implementation hence the solar battery, inverter setup. That grew along with my interest in the technology into a full emergency system that can run small things by battery along with a tri fuel ( gas, propane, natural gas) 7kw generator and a transfer switch to run anything else for emergencies. The next logical step was implementing something that could help pay for the initial expense of all that with a few more panels and a grid tie. I just had a 1518W peak day today and I think that is pretty good for only having panels rated at 1422 and it rained most of the day. Still trying to figure that one out but not going to spend too much time on it The sun must have been really strong and clear for a few minutes at some point. It has been something that has grown bit by bit and not a total system from the start but it all works together and meets my needs.

[SunEagle]

Inetdog, you are absolutely correct but since one is grid tie and the other is off grid, you have to consider them as 2 separate systems. When I installed them, I pulled wire for 2 strings. One is now the tap for off grid and the other is the entire string for grid tie. Both are switched so I can enable and disable one, the other or both. If I have need to use the off grid system, in order to adequately fund the off grid charge controller, I have to disable the grid tie until the battery bank is recharged. In the event of a power failure, the grid tie is useless so I can devote all the off grid system can handle without worry. They make systems like this but mine cost far less than those and I get the same function. Optimal is one or the other and not both. I am actually thinking of adding a second standby charge controller to put in parallel with my tracer and with a slight reconfiguration of wiring, I can feed both to actively power my home devices and not drain the batteries in the process, at least during a sunny day.

Interesting hybrid system you have there. I am not sure why you want to add the complexity of switching so you can use your grid tie solar panels to charge your batteries. Also running any loads off batteries is much more expensive than using the power from the Utility and charging batteries from solar is more expensive than using a standard battery charger.

The batteries may be your idea of an emergency backup power but with a battery system you still need a generator of some kind. That generator can support you during a power outage and charge your batteries when the power goes out.

IMO adding the wiring, switching and charge controllers seems to be an added expense that probably will never pay for itself.

[HOASUNBuster]

Tap on string

Inetdog, you are absolutely correct but since one is grid tie and the other is off grid, you have to consider them as 2 separate systems. When I installed them, I pulled wire for 2 strings. One is now the tap for off grid and the other is the entire string for grid tie. Both are switched so I can enable and disable one, the other or both. If I have need to use the off grid system, in order to adequately fund the off grid charge controller, I have to disable the grid tie until the battery bank is recharged. In the event of a power failure, the grid tie is useless so I can devote all the off grid system can handle without worry. They make systems like this but mine cost far less than those and I get the same function. Optimal is one or the other and not both. I am actually thinking of adding a second standby charge controller to put in parallel with my tracer and with a slight reconfiguration of wiring, I can feed both to actively power my home devices and not drain the batteries in the process, at least during a sunny day.

[inetdog]

Hello all, just getting myself started in the solar arena. This looks like a good active forum to earn a few merit badges along the way. My current system is a 1386 watt ( and growing) string powering a Power One Aurora 2KW grid tie along with a EPSolar 40A MPPT controller hosting a bank of 4 - 230Ah GC batteries and a Xantrex 1000W sine inverter. The Battery charge controller is running off a tap on the entire string as it can't handle the full voltage or watts.

Hello HOASUNBuster and welcome to Solar Panel Talk!

I think that if you do the math, you will find that having two different MPPT devices (in your case GTI and CC) connected to the same array of panels (even with a tap) is not going to work out well.
Without the tap, with both connected at the same point, they will fight each other trying to get the lion's share of the panel output with the result that either the operating power point will be unstable or it will stabilize at less than the panel MPP.
With the tap, the GTI is going to get shortchanged since some of the current from the lower part of the panel string is being diverted, confusing its attempt to get MPP from the point where it is connected.

You may be lucky enough to have something close to optimal, but it is very unlikely and I would not recommend that configuration to anyone.
Have you actually observed and done the calculations on the input power to the two units?

It is true, however, that splitting the array into two fixed size sub-arrays is not going to give you optimum performance either.

[HOASUNBuster]

Hello all, just getting myself started in the solar arena. This looks like a good active forum to earn a few merit badges along the way. My current system is a 1386 watt ( and growing) string powering a Power One Aurora 2KW grid tie along with a EPSolar 40A MPPT controller hosting a bank of 4 - 230Ah GC batteries and a Xantrex 1000W sine inverter. The Battery charge controller is running off a tap on the entire string as it can't handle the full voltage or watts.