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JadeKnight
01-20-2009, 10:49 AM
Found this while looking for means to power the Pico-ITX on my project.

Looks like it could be used for easily switching between DC and an AC power-brick/supply. It'll even charge a 12v SLA battery that is connected.

http://www.mini-box.com/picoUPS-100-12V-DC-micro-UPS-system-battery-backup-system

Reading the manual it says it can run on as low as 6v input, but will only charge the SLA if you use greater than 15v input.

Could it potentially be used to switch between a 12v AC brick and a Non-SLA power source (like NiMH or LiPo) connected to a Pico 60-WI power supply?

It seems possible, since the SLA charger will not engage if the input is less than 15v...

Adrenalynn
01-20-2009, 11:31 AM
Welcome to the forum!

Nice find - but connect it to a LiPo only in large open areas where exploding batteries maybe safely observed from a distance. :)

JadeKnight
01-20-2009, 11:36 AM
Welcome to the forum!

Nice find - but connect it to a LiPo only in large open areas where exploding batteries maybe safely observed from a distance. :)

Thanks.

I've been flying RC Heli's for over a year now, so I'm used to LiPo's and have all the necessary equipment ;).

Adrenalynn
01-20-2009, 12:43 PM
Ok - but my point is that a LiPo charger is a LiPo charger. The charger for that UPS is not gonna place nice in LiPo-Land.

That said - if you're running SLA or wet cells, that looks like a pretty inexpensive way to get cut-over.

JadeKnight
01-20-2009, 12:52 PM
Ok - but my point is that a LiPo charger is a LiPo charger. The charger for that UPS is not gonna place nice in LiPo-Land.

That said - if you're running SLA or wet cells, that looks like a pretty inexpensive way to get cut-over.

The thing is, I DON'T want it to try to charge the LiPo's (which would, o/c, be very dangerous).

I just want it to act as a safe 'switch' between AC and batteries. According to the docs, it shouldn't even try to charge the battery if the input is below 15v, which would be the case with a 12v AC brick. My LiPo charging would be handled with separate circuitry.

Would using diodes between the battery and the UPS help prevent any current from going back into the battery (in case the charger actually does try something at under 15v)?

Adrenalynn
01-20-2009, 01:03 PM
Remember that diodes have a pretty fair voltage drop. I would measure the terminals and see for sure what it's trying to do. But yes, a diode of adequate size (ie. figure out what your current requirements are!) should keep the voltage from flowing the "wrong way" in the same way that you'd put one in a power supply to protect the circuit from a storage cap discharging back through the regulator.

JadeKnight
01-20-2009, 01:14 PM
Thanks for the info, Adrenalynn.

ituner
01-23-2009, 06:22 PM
Remember that diodes have a pretty fair voltage drop. I would measure the terminals and see for sure what it's trying to do. But yes, a diode of adequate size (ie. figure out what your current requirements are!) should keep the voltage from flowing the "wrong way" in the same way that you'd put one in a power supply to protect the circuit from a storage cap discharging back through the regulator.

picoUPS is not using diodes, it is using power MOSFETS drived by an intelligent gate driver.
Read the manual here: http://www.mini-box.com/picoUPS-100-12V-DC-micro-UPS-system-battery-backup-system

The IC is an 'ideal diode or" solution from Texas intruments, called TPS2412. The board has two ICs and two power mosfets.

-Andrei

Adrenalynn
01-23-2009, 06:36 PM
Sorry - I wasn't suggesting that picoUPS _was_ using diodes. I was answering a specific question:

"Would using diodes between the battery and the UPS help prevent any current from going back into the battery "

The answer to that question, of course, is yes. Regardless of what the picoUPS is doing...

Welcome to the forum, btw! :)

ituner
01-24-2009, 01:15 AM
Sorry - I wasn't suggesting that picoUPS _was_ using diodes. I was answering a specific question:

"Would using diodes between the battery and the UPS help prevent any current from going back into the battery "

The answer to that question, of course, is yes. Regardless of what the picoUPS is doing...

Welcome to the forum, btw! :)

I see....There is a blocking diode (mosfet body diode) in between the battery and AC system and battery and charger circuit, so when the AC/DC system goes down (or below Vbatt) current will not flow the wrong way. The reason > 15V V(in) is required is simple: Battery charge. If V(In) is below 15V, it will still work, but battery will not charge...

-A