AA's Running EVO

Selfdestruct · Jun 13, 2010

In other news (i.e., enough screen separation talk)

How long can 4 Eneloop Rechargeable AA's run an EVO?

Amazon.com: Sanyo Eneloop: Electronics

First I have one of these for when I travel as a backup -- since AAs are readily available anywhere its easy to find and replace

USB Emergency Charger / USB Battery Pack - Battery Adapter PRO

Next I drained my Evo down to 62% when i decided to do this test

Plugged into boxwave and charged to 100%

Once at 100% i let it drain overnight, when i woke up the battery was 45%(yikes i only had wifi on)

I plugged it back into boxwave (same AAs in it)

It then charged to 68% and batteries were done

First Test Total charge: 61% of EVO battery

I should do a full charge and not have a break in between but i will do that eventually if anyone wants a unbroken test

axisofoil · Jun 13, 2010

well, the question is a bit complex.
Those batteries will store anywhere between 1500mAh and 1700mAh each on a typical charge. But they're only 1.2-1.5v depending on how charged they are.

Short of ripping the device apart and looking at it's electronics, I would assume it uses them in series (from looking at the picture. wiring batteries in series adds their voltages, but not their total capacities) and uses them to charge the phone's battery via usb's 5v pin, so you will get around 1500-1700mAh total power available to use at 4.8-6volts, maybe less depending on how well those particular batteries charge.

Then you have to transmit and charge the phone's battery. Li-ion batteries have realistic charging efficiencies of up to 80% or so, but depending on how fast you charge it, it can go a lot lower. Because the EVO's battery is 1500mAh, it means you're pushing it to want a single, full charge.

So, if you charge your phone while it's off, you SHOULD get ONE full or nearly full charge from fully charged NiMH AA's. If you charge while your phone is on and/or that charger is a high current charger, you will get less, probably close to around 60% or so, as the battery will heat up, and the phone is still using power.

cabbie · Jun 13, 2010

Once at 100% i let it drain overnight, when i woke up the battery was 45%(yikes i only had wifi on)

I went from about 35% to 18% letting it drain overnight. Interesting. Glad I was too drunk to plug it in or else I wouldn't have noticed.

Selfdestruct · Jun 13, 2010

Yup i guess it is much more complex haha

Well i ran another test... ran battery down to 5% then powered EVO off

Plugged into boxwave with 4 freshly charged batteries

18:00 to 20:51 it was off -- LED light became Green so i turned it on thinking it was all set

battery @ 90%

plugged it back into Boxwave and charging again with airplane mode on

21:07 Update: charged to 94% and AA's dead

soooo 89% battery from 4 AAs not bad when camping or traveling when in a pinch for juice

Biggest Fro · Jun 13, 2010

Or you could just carry a few replacement Chinese battery's in your pocket and just switch them out.

mattcnz · Jun 21, 2010

Would this charger have any negative effects on the EVO if I used regular disposable alkaline Energizer AA's?

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AA's Running EVO

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