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Power and Battery Backup


#1

Battery questions, I have. Several actually, but all power related on a FEZ Domino.

First is the RTC backup battery. The specs for the LPC2388 NXP chip allow a maximum of 4.6 volts on the V-batt pin. Am I safe in assuming that the USBizi derivative is the same and will be OK with a 3.6 volt Lithium-ion half AA as the battery backup? I need the backup to last decades so that’s why I’m using a higher capacity battery than a coin cell. Also is V-batt accessed at pin 8 on J1?

Second question. I’m evaluating the Domino to replace an older 8 bit 80C52 based single board computer that runs outdoors year round off of a 12 volt battery recharged with a small solar panel. The LM1117 5 volt regulator used on the Domino specs at 15 volts max input voltage. with a diode in series I don’t expect the input voltage from the panel battery combination to exceed 14.4 volts so I’m willing to risk hooking the Domino up to this power source. Anyone had any similar experience or advice?

I have a couple of other questions on other topics so I’ll put them in a separate thread. Thanks in advance for any help.


#2

Whatever you see in the LPC2388 datasheet applies to USBizi

[quote]Second question. I’m evaluating the Domino to replace an older 8 bit 80C52 based single board computer that runs outdoors year round off of a 12 volt battery recharged with a small solar panel. The LM1117 5 volt regulator used on the Domino specs at 15 volts max input voltage. with a diode in series I don’t expect the input voltage from the panel battery combination to exceed 14.4 volts so I’m willing to risk hooking the Domino up to this power source. Anyone had any similar experience or advice?
[/quote]
14.4V may work but you are pushing the limits


#3

@ idafez

Like the avatar! ;D


#4

[quote]@ idafez

Like the avatar!
[/quote]
Naaaa…he needs a FEZ :smiley:


#5

It may start making funny sounds at 14+.
I also noticed other day SparkFun has a rechargeable lipo coin cell.
http://www.sparkfun.com/products/10319
I was thinking one should be able to mount a lipo charger breakout that would keep the coin cell topped-off/fresh during normal operation. If you can get any battery to last for decades, please play the Loto soon, as the stars are smiling on you. Need to split with me :slight_smile:


#6

OK, I exaggerated - decades maybe not, but in the old system I’m replacing I’ve had Taridan Lithium batteries in service since 2000 and they are still at 3.6 volts (DigiKey P/N 439-1003-ND). They are oversized for the RTC they’re backing up, but they seem to be pretty reliable.

I’ve not had much experience with the shelf life on Lipo batteries. For my use it might be a concern if a user leaves the system unpowered and in storage for extended periods. I’ll look into what you sent, William.

Also thanks to both of you for the feedback on the 14 volt supply. I may decide to go with a another regulator before the Domino.