Battery Options

I have a radio control project that uses the Mega, a TFT touch pad, and a radio running on a 9V. I know 9V batteries do not have much capacity, but it was convenient. I added a battery monitor to the TFT and was quite surprised how bad the 9V is. A new 9V dropped 2 volts instantly. They don't last long before I notice the TFT fading when I press buttons on the screen.

Since I got my Arduino, I have been a regular at Radio Shack buying batteries. They keep giving away free stuff that take batteries when you buy batteries. The last freebee was an emergency USB charger. It takes two AA batteries and charges cell phones and they sell it for less than $20. Since AA's have about twice the mAH of a 9V, and the voltage is being boosted with what should be more efficient means than using a voltage regulator, I put in two new batteries and plugged in my Arduino. It ran for at least 2 hours with less than a 1/10V drop. It may have been 3 hrs, I didn't see it shut off. I had no fading when pressing buttons.

I noticed some rechargeable USB portable power units at the hardware store for under $20. I picked up one of these ( http://www.conceptgreen.com/our-products/portable-chargers/3/333/all-products/P-cg2000-battery-portable-charger ) it has 2000 mAH. I cut an old printer cable down to about a 6 inch cable to plug it into the Arduino and I have been using this for portable power. It's a little bit bigger than my 9V case, but it's half as thick so it's a good portable size.

Has anyone tried something like this, and if so how did it work? At 20 bucks for a hand full of 9 volts, it seems like a no brainer??

Thanks,
Dave

My wife picked me up a little blue wallwart with USB out at RadioShack, says enercell on it, plug in a USB-A to USB-B or USB-B mini and you're good to go with powering the board via USB connector.

Anything that provides a boosted voltage will appear to give a more even output. As the battery voltage drops more the voltage gets boosted more. It will remain at a good stable 5V level until the battery gets too low when it will shut off abruptly.

I have a solar charged LiPo that I use for portable power. It has a USB A output for running things like an Arduino (or charging your phone) and a mini USB B socket for charging it from your computer or USB wall wart.

Cost me something like £15 on eBay. Labelled as 4400wMh (yes, wMh - [willie mot hours], not mWh, which at 3.6V would be 1222mAh I guess?)

Thanks for the replies. I have a larger solar unit like you posted, but it's much larger in size and cost quite a bit more than this new one I bought. As the price drops on these things, it makes it even a better battery replacement to power the Arduino.

Does anyone see any problems powering the 5V pin directly with a unit like this? It would be nice to bypass the Arduino USB port and eliminate the bulky USB jumper cable.

Dave

I think 3.6 volts will run an arduino on its 5 volt pin, but if you try to drive something else with an output pin, it may not accept that low of a signal as the HIGH state.

GunnerCAF:
Thanks for the replies. I have a larger solar unit like you posted, but it's much larger in size and cost quite a bit more than this new one I bought. As the price drops on these things, it makes it even a better battery replacement to power the Arduino.

Does anyone see any problems powering the 5V pin directly with a unit like this? It would be nice to bypass the Arduino USB port and eliminate the bulky USB jumper cable.

Dave

The battery is 3.6V, but again it has the 5V boost circuit in it. It gives 5V out right up until the circuitry shuts it off to save the battery from discharging too much. It's designed for giving your USB charged mobile phone a boost to allow you to call the emergency services when you're stranded up a mountain :wink:

You can skip the "bulky USB jumper cable" and use whatever other bulky cable you want connected to +5 and Gnd on the power header instead - add a 1N4001 type diode from 5V (anode) to Vin (cathode) to avoid reverse driving the onboard regulator.

@majenko,
what does this mean>?
"Where is your SSCCE?!?!"
Too many letters to guess what SSCCE means.

CrossRoads:
@majenko,
what does this mean>?
"Where is your SSCCE?!?!"
Too many letters to guess what SSCCE means.

I have been monitoring the voltage while connected to my Arduino. It seems to maintain a steady 4.8 to 4.9 voltage.

Dave

CrossRoads:
You can skip the "bulky USB jumper cable" and use whatever other bulky cable you want connected to +5 and Gnd on the power header instead - add a 1N4001 type diode from 5V (anode) to Vin (cathode) to avoid reverse driving the onboard regulator.

Good idea to use the diode, thanks!

Dave

Glad to help.