Author Topic: Revo Pico Battery Replacement  (Read 1393 times)

charysm

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Revo Pico Battery Replacement
« on: 13:47:59 | 02 November, 2020 »
Hello,

I have the later version of the Revo Pico, with eight front buttons around the dial. Despite the mediocre sound quality of the internal speaker, I like the device quite a bit. I have never really used the portable feature, but just now as I am starting to carry the brick around a bit, the batteries died pretty much completely. It houses a battery pack labeled GSP085085 3500mAh 7.4V, with had a visibly inflated plastic wrapping in my case. While a replacement may be available through some chinese websites, this doesn't seem to be a viable option these days unless you really need a particular item. Similar RC battery packs were also not quite straight forward to find, and quite honestly I wasn't really prepared to invest 30+ euro into the device for just having it battery powered.

What I did happen to have though was a laptop battery pack, which for some reason refused to charge in the laptop despite not being very old. As it was labeled 14.8V I thought I'd have a good chance to get at least two healthy cells out of the pack. It did contain four ncr18650 cells, which are specified at 2900 mAh. At first I was a bit unsure whether the charging circuit would support Li-ion vs Li-Polymer, being permanently connected, and given that I was already removing a pack under pressure. But after a little research I didn't think it was an issue, and after all it seems that the charging circuit is as little sophisticated as a LM317 voltage regulator and a diode anyways...

When I connected the somewhat pre-charged cells (two in series) to the device, I could measure a 400mA current into the batteries when connected to the power supply, and 450mA out of the batteries when they powered the device. Later I could measure a 900mA current when starting to charge from depleted batteries, which I could observe decreasing. It does seem that it is a constant voltage charging setup, where the battery is simply added as a buffer, but the charging currents are reasonable.

Taped together the two cells fitted nicely at the same place of the original pack, with the circuit board stuck in the gap between them, holding everything safely in place even without any glue. The radio does over 6 hours on a charge now.

All in all a fairly simple and effective repair. I thought I'd post here in case anyone finds the information useful.

Question: There is a distinct noise coupled into the audio (both internal speaker as well as audio out to external amp), a bit similar to cellphone noise. It is constant in volume, i.e. it doesn't scale with the volume setting. At higher volumes it is hardly noticeable and no issue, but it can be in quieter environments with lower volume. Has anyone observed the same? or even a suggestion as to how to improve shielding, decoupling or whatever in the device?

Thank you.
« Last Edit: 13:52:31 | 02 November, 2020 by charysm »

 

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