Batboard

Anyone have any experince with using solar power to provide backup power to a motorola turbo repeater

I was looking at using

2 -180 watt panels tied to a charge controller tied into 4 220ahr batteries,


Main question is what would be the simplest way to have the repeater run off the solar/batteries unless the battery voltage was 2 low then have it switch to poco power

My two bits worth:
I would recommend that you use a solar charge controller (such as the Trakstar MPPT by Mornigstar) with MPPT, a low voltage disconnect is absolutely necessary if you wish to preserve your batteries. The low voltage disconnect function could be used for the transfer to some other power source.
Most lead acid batteries must never be discharged below 50% capacity.
Lead acid batteries must never be left in a discharged state. If you have very many sunless days do not expect your solar charger to preserve your batteries, you will have to charge them, or have sulfated batteries.
Even high clouds can cut your charge rate by half or more.
Your battery seems rather large for your solar panels. I think it would take about 4 days to charge the battery if it was discharged to 50% (440 AH), not counting the repeater drain.

Seems like a metric assload of money to try to eliminate some usage charges from the power company. A TRBO repeater shouldn't cost that much to run from utility power - your main utility expense would be the monthly charge and drop itself. If that's already in place, why go through the expense and effort of running solar?

My two bits worth:
I completely agree, except perhaps there are other reasons:
Perhaps the solar panels, as well as other items are at hand.
I think it is a worth while experiment to see if it is practical.
Perhaps planning for a site that is truly off the grid.
Then it could be political: Government funds available for alternative energy.
I am presently experimenting with 400W of panels that I scrounged 17 years ago.
Recently designed a 3KW off grid PV system for a local utility's microwave links.

Then I did not buy my Prius for financial reasons, although 50 MPG is nice.

Power from the Grid is in place and this setup would not be used for everyday power to the trbo repeater it would be used for emergency back and prolonged outages. we recently had outages at that site of 14 days due to the massive ice sotrm that hit western ky, they don't want to put in a generator and then have fuel issues so they were looking into solar for emergency backup power

My two bits worth:
Now I see.
Actually, you are proposing a PV system backed up by utilities, not the other way around.

I think this is what you want:
Use a power supply with a "Smart" battery charger, (An Outback inverter which also could drive a LV disconnect) not just a constant voltage type, set up for float charging your battery of 4 strings of 220 AH batteries.
The charger will have to deliver about 45 amps, so one of those desk top power supplies will not do. Those batteries are going to be very thirsty after a long power outage.

You should have about half of the total AH capacity to run the radio when power is lost.
"Peukert" calculations determine how much capacity you actually have at your discharge rate.
The battery Ampere Hour capacity is usually specified at the "20 Hour rate", which is accurate for that current, the radio will likely draw much less, therefore you have more AH than expected.

Connect your solar panel charge controller to the battery bank in parallel with the charger.
This way, the battery will always be at a full state of charge, the solar can probably tide you over almost indefinitely, or at least until you restore utilities. Be extremely careful in setting your charge voltages: a few tenths to high and you cook a battery.