# Supercapacitor Emergency Power Supply UPS

I'm considering hiring an electrical engineer to design an emergency power supply for use in embedded devices. This power supply only needs to hold ~15 seconds of charge (enough time to safely shut down the devices). I would like to support 12V and up to 2A. Juice4Hault produces a Supercapacitor UPS, but thier prices are very high. Batteries aren't reliable since they degrade and corrode over time.

I found some cheap parts that I hope will keep production costs low:

2.7V 100F Supercapacitors ($1.50 each) LM2623 ($0.50 each)

Basically I would like to use low voltage supercaps and a voltage booster to convert extra amps into higher voltage output. Where I'm lost is interpreting the LM2623 datasheet. Could it reliably boost these Supercaps into 12V 2A 15-second output?

UPDATE: I'm considering using two capacitors in series. Then I'd have 5.4V 50F at my disposal. The Samwha Green-Caps that I am considering can pull 5A continuous current. So 5A ∙ 3V(Min) ∙ 80% efficiency = 12V ∙ 1A, sustainable for 10 seconds, which I could live with. I would have to use a more expensive booster:

TPS55332-Q1 (\$2.50 each)

Is there an IC that can safely support this?

• Supercap backups are easy to make and they have ICs dedicated to the purpose. However, if you're going to hire an electrical engineer to design it, give them a price target and allow them to choose the components. If you want to design it yourself, look a bit more into those dedicated ICs and make a first pass at a schematic then ask some more specific questions. The dedicated supercap chargers will balance the charge on the caps and also be able to trigger alarms/interrupts when power is down. – scld Feb 22 '16 at 23:02
• 12V⋅2A⋅15s=360J – Ignacio Vazquez-Abrams Feb 22 '16 at 23:21
• 360J in a capacitor with Vmax of 2.5V is 115F, so capacitance wise it is do-able. But assuming 80% converter efficiency you would need the caps to be rated for pulling 12A minimum continuously, and have a boost converter capable of that. But the capacitance would also have to be higher as step-up at that kind of load would be unlikely to run at less than 1V input so couldn't fully discharge the capacitors. – Tom Carpenter Feb 23 '16 at 0:10
• Make sure you know the ESR (internal resistance) of your supercap before you part with money. Some are in the tens of ohms which make great low-current long term backup supplies but would kill this app... – Brian Drummond Feb 23 '16 at 1:12
• @skibulk 12V@2A=24W out. @80% efficiency, that means 24/08=30W in. 30W@2.5V=12A. – Tom Carpenter Feb 23 '16 at 14:37