using solar panels to charge a UPS?

[Anonymous]

A 4 kVA UPS was left behind by a tennant who moved out of
an office we rented. It still works, but the batteries are
3 years old, perhaps one foot in the grave.
Now I wonder if I can use this to make a stand-alone solar power
system (not tied to grid) for a holiday house.
This would only have modest power requirements < 2500 W a few hours
per day. It is in a sunny locale 32 degrees from equator.
The UPS has batteries wired in series for 48 V DC, so I could use
two truck batteries, instead of sealed gel batteries.
I can get some Bosch panels for a good price. These have Vmpp 27 V
which would be okay to charge battery, but Voc is 33 V.
Would this be a problem?

 

[Bruce Gordon]

A 4 kVA UPS was left behind by a tennant who moved out of
an office we rented. It still works, but the batteries are
3 years old, perhaps one foot in the grave.
Now I wonder if I can use this to make a stand-alone solar power
system (not tied to grid) for a holiday house.
This would only have modest power requirements < 2500 W a few hours
per day. It is in a sunny locale 32 degrees from equator.
The UPS has batteries wired in series for 48 V DC, so I could use
two truck batteries, instead of sealed gel batteries.
I can get some Bosch panels for a good price. These have Vmpp 27 V
which would be okay to charge battery, but Voc is 33 V.
Would this be a problem?

Yep, but understand that UPSs are NOT designed for conversion
efficiency like a GridTied inverter system. Their Inverter design is
grossly inefficient because they are designed to provide instant Power,
for a short duration, and then take a long time to recharge the
batteries. You will need a "GOOD" MMTP Charge Controller, (Outbacks MX
Series) to do the Solar to Battery voltage conversion to get 48 Vdc into
the batteries.....

 

[Josepi]

PV panels are constant current sources. You would have to find out the
current output and see if the batteries can stand that current every day for
about 4-5 hours.

A Smart MMPT is the best charger, usually.


A 4 kVA UPS was left behind by a tennant who moved out of
an office we rented. It still works, but the batteries are
3 years old, perhaps one foot in the grave.
Now I wonder if I can use this to make a stand-alone solar power
system (not tied to grid) for a holiday house.
This would only have modest power requirements < 2500 W a few hours
per day. It is in a sunny locale 32 degrees from equator.
The UPS has batteries wired in series for 48 V DC, so I could use
two truck batteries, instead of sealed gel batteries.
I can get some Bosch panels for a good price. These have Vmpp 27 V
which would be okay to charge battery, but Voc is 33 V.
Would this be a problem?