Off Grid Solar charger connected to an APC UPS

[pramodsankar]

I am looking to install about 750Watts - 900Watts solar panel with a 30A / 40A PWM charge controlar. The Grid Power situation here in my location is very bad we have Grid AC power for only 2-3 hrs in the day (6am-6pm) but during night power Grid power is availabe for 6hrs (6pm -6am). I have a APC 2.2KVA UPS with 4nos of 70AH C10 acid battries.

My question is what will happen when Grid power is available? since the UPS will also charge the battery and the solar charger will also charge the battery. While this affect the charging/discharging? Do i need to add any extra safety circute to this?

[billvon]

My question is what will happen when Grid power is available? since the UPS will also charge the battery and the solar charger will also charge the battery. While this affect the charging/discharging? Do i need to add any extra safety circute to this?

If you do not exceed the max charge rate of the battery when both sources are available you should be OK. In general the chargers will 'disagree' over things like bulk and absorption state timings, and this may lead to less efficient charging overall - but the batteries shouldn't be damaged.

However, it should be noted that any UPS battery system won't last long in that kind of service to begin with - especially with UPS batteries.

[Sunking]

I am looking to install about 750Watts - 900Watts solar panel with a 30A / 40A PWM charge controlar.

That would not be a good use of money. I can only assume this is a 12 volt battery? If correct you get the same charge current (40 amps) out of a 500 watt panel with a 40 amp MPPT controller as you will with a 720 watt panel with PWM controller.

I hope the battery you have is an AGM able to withstand a 1C charge rate. If these are flooded or gel batteries you will burn them up with a 1C charge rate.

[pramodsankar]

what is the recomended panel capacity to avoid the excess charge?

The battries are normal 12v 70AH Tubular C10

I am under the understanding that the APC UPS only 7Ah per hr

[Sunking]

You are putting the cart in front of the horse. First thing you need to do is determine how many watt hours you want solar to provide each day.

[pramodsankar]

My requirment is about 4500 watt hr per day

[Sunking]

My requirment is about 4500 watt hr per day

You are no wher close to where you need to be. This is not even a 12 volt application, more like 24 or 48 volt requiring a 1000 to 2000 watt solar panel, 80 amp MPPT controller and a 700 Kg battery. LOL.

Good luck , you will need it. Hope you have a very large bank account.

[pragathe2]

I am looking to install about 750Watts - 900Watts solar panel with a 30A / 40A PWM charge controlar. The Grid Power situation here in my location is very bad we have Grid AC power for only 2-3 hrs in the day (6am-6pm) but during night power Grid power is availabe for 6hrs (6pm -6am). I have a APC 2.2KVA UPS with 4nos of 70AH C10 acid battries.

My question is what will happen when Grid power is available? since the UPS will also charge the battery and the solar charger will also charge the battery. While this affect the charging/discharging? Do i need to add any extra safety circute to this?

Yes Pramod. I also have the same doubt. What will happen to batteries when both the solar MPPT charger and the Grid charger, charge the battery. The current may be twice then.

[pragathe2]

I am looking to install about 750Watts - 900Watts solar panel with a 30A / 40A PWM charge controlar. The Grid Power situation here in my location is very bad we have Grid AC power for only 2-3 hrs in the day (6am-6pm) but during night power Grid power is availabe for 6hrs (6pm -6am). I have a APC 2.2KVA UPS with 4nos of 70AH C10 acid battries.

My question is what will happen when Grid power is available? since the UPS will also charge the battery and the solar charger will also charge the battery. While this affect the charging/discharging? Do i need to add any extra safety circute to this?

Dear Pramod,
Forget about PWM charger. By using the latest MPPT charge controller, you can go for 30% lesser panel.

[pramodsankar]

You are no wher close to where you need to be. This is not even a 12 volt application, more like 24 or 48 volt requiring a 1000 to 2000 watt solar panel, 80 amp MPPT controller and a 700 Kg battery. LOL.

Good luck , you will need it. Hope you have a very large bank account.

Sorry with about 10hr of grid power my power requirment will be about half so 2250 watt hr.