Help with small off grid system

[gellison]

I have the following equipment: Four one hundred watt 12 Volt panels, Vmp 17.8 V, Imp 5.62 A. Two 160 watt 12 Volt panels, Vmp 18.2 V, Imp 8.8 A. A CM5024Z 50 Amp 12/24 Volt Charge Controller. Four 105 Ah Deep Cycle marine batteries. And a Whistler 2500/5000 Watt Power Inverter. What would be the best way to hook up all this equipment for a small off grid system? If I have the panels all in parallel, it seems as if the Vmp might be close enough to work. I am assuming a parallel connection with the batteries as well, which would basically be a 12 Volt Battery with about 400 Ah. What is the best way to hook up four batteries in parallel in order to keep the bank balanced?

[sensij]

I moved this post to its own thread.

[sensij]

That is a PWM charge controller, so at some level, you have to stick with panels in parallel. If you replaced the inverter with a 24 V, you could wire this all up as a 24 V system and probably be better off, if you don't have any direct 12 V loads to worry about.

What are you planning to run with this?

[jflorey2]

I have the following equipment: Four one hundred watt 12 Volt panels, Vmp 17.8 V, Imp 5.62 A. Two 160 watt 12 Volt panels, Vmp 18.2 V, Imp 8.8 A. A CM5024Z 50 Amp 12/24 Volt Charge Controller. Four 105 Ah Deep Cycle marine batteries. And a Whistler 2500/5000 Watt Power Inverter. What would be the best way to hook up all this equipment for a small off grid system? If I have the panels all in parallel, it seems as if the Vmp might be close enough to work. I am assuming a parallel connection with the batteries as well, which would basically be a 12 Volt Battery with about 400 Ah. What is the best way to hook up four batteries in parallel in order to keep the bank balanced?

So far it looks like a 24V system would be your best bet. What do you want to power and how often will it be used?

[gellison]

I am currently using the four 100 watt panels in parallel with two deep cycle batteries also in parallel to run my primary refrigerator during daylight hours and then revert to grid power at night. When the batteries have recharged the next morning, I return to battery/inverter. I am thinking of adding the two additional batteries and two additional solar panels to increase my run time on batteries while maintaining approximately the same time to recharge. Any thoughts? If I add the two additional batteries in parallel, what is the best way to wire them together to maintain a balanced battery usage?

[SunEagle]

I am currently using the four 100 watt panels in parallel with two deep cycle batteries also in parallel to run my primary refrigerator during daylight hours and then revert to grid power at night. When the batteries have recharged the next morning, I return to battery/inverter. I am thinking of adding the two additional batteries and two additional solar panels to increase my run time on batteries while maintaining approximately the same time to recharge. Any thoughts? If I add the two additional batteries in parallel, what is the best way to wire them together to maintain a balanced battery usage?

Uh. You do understand that running that fridge from a solar/battery system is costing you at least $1.00/kWh while at night using the grid the cost is probably 1/5 that at $0.20/kWh.

So basic math states you are not saving any money using those batteries. Why are you doing that?

[Wy_White_Wolf]

What is the input voltage requirement of the inverter? That will determine how the rest has to be wired.

WWW

[SunEagle]

o

What is the input voltage requirement of the inverter? That will determine how the rest has to be wired.

WWW

It looks like that CM5024Z is a PWM CC with input voltage limited to <=50VDC.

[Wy_White_Wolf]

o

It looks like that CM5024Z is a PWM CC with input voltage limited to <=50VDC.

Yes it can handle 12 or 24volt. So the inverter would determine which of those voltages to wire the battery bank which will determine if he needs to wire the array for 12 or 24 volt.

WWW

[NEOH]

I have the following equipment: Four one hundred watt 12 Volt panels, Vmp 17.8 V, Imp 5.62 A. Two 160 watt 12 Volt panels, Vmp 18.2 V, Imp 8.8 A. A CM5024Z 50 Amp 12/24 Volt Charge Controller. Four 105 Ah Deep Cycle marine batteries. And a Whistler 2500/5000 Watt Power Inverter. What would be the best way to hook up all this equipment for a small off grid system? If I have the panels all in parallel, it seems as if the Vmp might be close enough to work. I am assuming a parallel connection with the batteries as well, which would basically be a 12 Volt Battery with about 400 Ah. What is the best way to hook up four batteries in parallel in order to keep the bank balanced?

If the DC input to the Whistler 2500/5000 Power inverter is 12 Volts then use
Method #2 - Opposite Diagonal connection or
Method #3 - Equal Length Star connection ...

http://www.smartgauge.co.uk/batt_con.html

[SunEagle]

Yes it can handle 12 or 24volt. So the inverter would determine which of those voltages to wire the battery bank which will determine if he needs to wire the array for 12 or 24 volt.

WWW

Based on that 50VDC input max and those panel Vmp ratings of 18v the OP could wire them in pairs for a 24v battery system.

But since it is a PWM type CC that would reduce the charging amps if he was staying with a 12v battery system so the panels would need to be wired all in parallel to obtain about 40amps.

[sensij]

Yes it can handle 12 or 24volt. So the inverter would determine which of those voltages to wire the battery bank which will determine if he needs to wire the array for 12 or 24 volt.

WWW

The inverter is 12 V, 15 V max input voltage. I reached down a datasheet, but can't link it now.

[gellison]

In answer to SunEagle's question, I set this system up to insure that I can keep my refrigerator running in the event of a grid down situation. It has already proven itself several times during power outages. Unless you are amortizing original purchase prices, I am at a loss as to how you figure running the solar is costing me $1 per kWH. I did not set this system up to save money or to go green necessarily, although those are valid reasons.

The input voltage on my inverter is 12 volts, so connecting panels and batteries in parallel is my only choice at present unless I get a 24 volt inverter.

Thanks to Neoh for the battery connection patterns. That was exactly what I was looking for in order to balance the flow to and from the batteries.

Thanks everyone for your input.

[SunEagle]

In answer to SunEagle's question, I set this system up to insure that I can keep my refrigerator running in the event of a grid down situation. It has already proven itself several times during power outages. Unless you are amortizing original purchase prices, I am at a loss as to how you figure running the solar is costing me $1 per kWH. I did not set this system up to save money or to go green necessarily, although those are valid reasons.

The input voltage on my inverter is 12 volts, so connecting panels and batteries in parallel is my only choice at present unless I get a 24 volt inverter.

Thanks to Neoh for the battery connection patterns. That was exactly what I was looking for in order to balance the flow to and from the batteries.

Thanks everyone for your input.

My estimate of $1/kWh is mostly based on the cost of the FLA type batteries and the number of watt hours they produce over their life along with the costs of the solar panels, charger and inverter.

You take the estimated number of cycles and the respected watt hour generation over the life of a the battery and then divide by the cost of the battery system.

So for a 12v 400Ah battery system you should safely get 1200 watt hours a day or cycle. (12v x 400Ah x 25% = 1200wh).

Now the battery might have 1825 life time cycles (365 days x 5 years = 1825) or 1825 x 1200wh = 2190kWh. Then divide the cost of the battery system by the total kWh.

Now you can probably go deeper than 25% DOD each cycle but that may shorten the number from 1825. A lower DOD% should increase the number of cycles.

If you provide an estimated cost for your solar/battery system I could get closer to the $/kWh they get you.

As for having an emergency power source, based on a lot of good data using an emergency generator to provide power the few times when the grid is down has pretty much shown it will cost you less to if you use a solar / battery system to provide that power.

A solar grid tie system will result in a lower electrical costs and actually pay for itself but as an emergency power source with batteries the cost saving & reliability disappear.

[gellison]

Again thanks SunEagle for your input and clarity.