# UPS on Super-Caps

Discussion in 'General Electronics Discussion' started by shiekh, May 4, 2011.

1. ### shiekh

77
1
Oct 11, 2010
I am wondering about running a UPS on a super-cap array (I'm tired of replacing the battery)

http://www.goldmine-elec-products.com/prodinfo.asp?number=G18113

should be able to hold up 100W for about 3 mins (some of this will be powering the UPS itself)

I was wondering what algorithm a UPS uses in general to test its batteries, and if a super-cap array like this will trigger the battery alarm or not. Hopefully the charger will also be happy.

At first I was worried about the need to balance the array (with zener diodes), but since they sell it as an array, I suppose this is not a real concern.

These 2600F capacitors can now be got used for about \$10 each

http://www.goldmine-elec-products.com/prodinfo.asp?number=G18107

Last edited: May 9, 2011
2. ### Resqueline

2,848
2
Jul 31, 2009
Ok, so the bank is 433 Farads & 15 Volts = 48750 Joules.

100W is 7.25A at 13.8V and this gives a rate of change of 17mV/second (at that voltage). At 10V you might get a rate of change of 23mV/second.
The UPS might cut off at 10V so you have 3.8V to work with giving 3.8/0.02 = 190 seconds = 3 minutes & 10 seconds. All this is assuming a 100% UPS efficiency.

If you can modify the charging voltage up to 15V, and perhaps lower the cutoff voltage you'll get a longer run-time, potentially giving you at least 3 minutes in practice.

The capacitors needs to be charged to at least 11V before connecting the UPS. I don't know anything about the battery test method. I'd certainly balance the array!

3. ### shiekh

77
1
Oct 11, 2010
Progress report, for those that might be interested in trying the same:

* The UPS I picked actually runs between 13.6 and 10.6V (I had estimated 13.8 and 10.0V) which makes it equivalent to a 1AH 12V battery.

* The UPS had no problem filling the capacitors from 0V

* The array does not need any balancing (some 4.7V Zeners could be used to balance pair-wise if one really wanted such protection)

* Fortunately the UPS does not trickle charge, which might just slowly overfill the capacitors (balancing Zeners would help if there was a trickle charge)

* 'Bad battery' alarm has not appeared, so it seems to be recognizing the capacitor array as a good battery

* Have build a wooden carrier for the capacitor array after figuring out a design that is easy to make (see attachment)

Of course the run-time is short (a few minutes), but this is easily enough to carry one through a glitch, and in such a low duty application the capacitors should last indefinitely.

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Last edited: May 24, 2011
4. ### AprilSteel

111
9
Feb 2, 2017
This is 6 years old now but I would be interested to know more about using a supercap bank as a battery for a power grid. Anybody got one of these running or a UPS running the personal grid from solar panels?

5. ### shiekh

77
1
Oct 11, 2010
AprilSteel likes this.

111
9
Feb 2, 2017