-Works as advertised, never missed switching between power sources
-Voltage input requirement makes product totally usuitable for automotive use
-Unbelievably long charging time, even at recommended voltage is not suited for car use
The PicoUPS is an rather odd device. It's basic function is to operate as a uninterruptable power supply for a car PC. Connect a second sealed lead acid battery to it and when you shut your car off, it switches power from the car battery to the second battery and continues to power the PC. When the car is restarted, the second battery is recharged by the car's power and it is ready for another cycle. Thus, all 'car-off' functions are taken up by a secondary battery, not your vehicle battery. Slick!
The rather odd part about the PicoUPS is that it is completely unsuitable for in-car PC use because the circuitry requires a much higher voltage than the standard car alternator can put out in order to charge the secondary battery! Not only that, but the rate at which it recharges the alternate battery is quite low, meaning you have to drive your car around quite a bit (hours) to charge the battery enough to run the computer for minutes!
An odd device, indeed. More on that i just a moment. First, here's an explanation of how the PicoPSU works:
1. On one end of the PicoPSU are two inputs. One attaches to your secondary sealed lead acid battery. the other goes to the switched part of your car's electrical system. This can't be the accessory line, though, because it has to carry all the juice to run your PC. An appropriately sized relay is required. You would think that this would be included on the PicoUPS, but it isn't, so include it in the cost calculation if you purchase one.
2. At the other side of the PicoPSU is the output. This feed your PC's +12v and ground for the power supply.
Operation of the PicoPSU is transparent. A multi-colored LED signals when the system is charging or discharging and if it is receiving power at all. When the car is on and supply power from the alternator, the PicoPSU uses the car as the source of power to feed the PC and also charge the secondary battery. When the car is turned off, the PicoPSU seamlessly switches to the secondary battery to supply the PC for operation.
In practice, the PicoPSU works perfectly. I connected it to my benchtop power supply (a 10 amp 13.8volt AC-DC converter) and also to a 12 volt 9 amp-hour sealed lead acid battery I bought from Interstate batteries (item SLA1088). I ran the outputs to my Mini-ITX system's (Intel D201GLYA) power supply and hit the start button for the PC. It started as normal and ran perfectly. I then cut the power from the benchtop power supply and the system switched over without interruption to the SLA1088 battery.
Switching the power supply back on and off several times, I found that the PicoPSU did a fine job of keeping the computer from crashing when switching between supplies, with no issues whatsoever.
The description of the PicoPSU on Mini-box's site says that it is designed to switch between a DC input source of 15-18 volts. Uh-oh. Car alternators usually only put out 14.5 volts at best. I decided to run a series of tests on the usability of the PicoPSU and here's where the oddness of this product's suitability for the car PC market begins to creep in.
Using a digital multimeter, I connected it to the alternate battery and recorded the voltage every 5 minutes for several cycles. From the left side of the graph to the right:
1. First, I just turned the car (my benchtop power supply) on to charge the battery. It took about 3 hours to raise the voltage from 11.82 to 12.06, about .24 volts.
2. Next, I started the computer and then shut the 'car' off. The PicoPSU switched to the alternate battery smoothly and ran for 12 minutes before the voltage was too low to keep operating the computer.
3. I then turned the 'car' power on and left the computer off to give the secondary battery a quicker charge. About an hour after charging, I started the computer and ran it for about 30 minutes with the car power still on. This caused the voltage on the secondary battery to drop slightly and then level out.
4. I then shut off the car power and ran the PC on the secondary battery. It lasted for about 9 minutes before shutting down.
5. I then restarted the car power and also the computer and operated it like that for 30 minutes.
6. I shut the car power off and left the computer on. It lasted for just under 2 minutes before shutting off.
This product is not suited for car PC applications. A larger secondary battery would have extended the run times but also extended the already excruciatingly long charge time. No wonder, since the specs call for 15 volts or more to adequately charge a battery. My results reflect that. Unless you drive your car for hours in between stops, you won't get a very long run time from your battery and short runs of 30 minutes or so barely charge the battery. The manual for the PicoUPS calls for a 6-12 hour charge time between uses for a 7ah battery at 12 volts - the same rating as the battery I tested with.
I have to wonder what this product is for at all. It cannot take a 24 volt input (too high), which means it is not intended for the marine market. It would only be suitable in applications where a specially designed power supply is used. That leaves the automotive market out.
Minibox's description says that it is for uninterruptable power supplies for mission critical applications like servers and so forth. Which is fine, but they better not draw much power. The max the PicoUPS can deliver is 6 amps. At 12 volts X 6 amps, the PicoUPS can power a 72 watt system and no more.