Modification of the Radioditty charger with "TP5100" card at $ 2.

Juan Francisco
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Re: Modification of the Radioditty charger with "TP5100" card at $ 2.

Post by Juan Francisco » Sun Jun 07, 2020 2:45 pm

curiously if it works and charges faster than with the original PCB but same power source, so I intuit that the original PCB limits amps

AB6RF
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Re: Modification of the Radioditty charger with "TP5100" card at $ 2.

Post by AB6RF » Wed Oct 07, 2020 6:16 am

Resurrecting an older thread...

I’ve noticed the GD-77 seems to be very sensitive to switching noise coming from the charger.
With the stock charger, using the stock rubber ducky antenna, when the radio is on the charger the OpenGD77 S-meter reads about 50% when the radio is tuned to an empty analog FM frequency.
When I replaced the stock charger board with one of these “eBay li-ion charger boards” the S-meter reading went to almost 100%.

Could someone else check if they see the same?
Stock charger, stock rubber ducky antenna, OpenGD77 FW, and the radio on the charger, what’s your S-meter reading on a empty analog FM frequency?

Mikko, AB6RF

VK3KYY
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Re: Modification of the Radioditty charger with "TP5100" card at $ 2.

Post by VK3KYY » Wed Oct 07, 2020 6:29 am

I've noticed on my HF radio which is close to my GD77, that one of the mains PSU's is very noisy.

I initially thought the problem was the battery charge controller board inside the docking / charger, so I replaced the original board with a TP5100, but it didn't make any difference, and I realized the problem was the 12V SM PSU.

Which bands are you seeing the noise on. 2m or 70cm.

AB6RF
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Re: Modification of the Radioditty charger with "TP5100" card at $ 2.

Post by AB6RF » Wed Oct 07, 2020 6:57 am

Good question, I just realized I forgot to include that info.
I’m looking at it on 2m band.
All stock, except for using the OpenGD, the s-meter reads about 50% when the radio is the charging dock.
Out of the dock, on the same (empty) frequency, the s-meter reads about 20% to 25%.

With and eBay charger board, the meter reads about 75%, even after I tried pretty hard to filter the input and output sides of the charger board. Basically no amount of bypass caps, common mode chokes, or ferrite beads made much of a difference.

Also, while looking into this, I also realized the stock charger board is nothing more than a ~8.4V buck regulator. It’s not really a constant-current / constant-voltage charger.

VK3KYY
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Re: Modification of the Radioditty charger with "TP5100" card at $ 2.

Post by VK3KYY » Wed Oct 07, 2020 7:04 am

Well any noise from the PSU could also possibly come in via the charge controller onto the supply.
The battery won't act as a capacitor for signals at 144Mhz

AB6RF
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Re: Modification of the Radioditty charger with "TP5100" card at $ 2.

Post by AB6RF » Wed Oct 07, 2020 7:19 am

By now I’m using a linear 12V supply for the charger dock.
I’m just surprised that even the stock charger generates enough switching noise that at least the analog FM sensitivity gets degraded when the radio sits in the charger dock.

The switching noise doesn’t open the squelch, but it does push the s-meter reading up (while no actual signal is present), and if I tune to a weak FM signal (barely readable), the signal gets buried in the noise when I put the radio in the charger. All this on 2m.

With the eBay charge controller it got even worse, no matter what filtering I tried to add to it.
BTW, my “eBay charge controller board” is using MAX745 charge controller IC.

ZL2FL
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Re: Modification of the Radioditty charger with "TP5100" card at $ 2.

Post by ZL2FL » Wed Oct 07, 2020 6:41 pm

I bought a couple of these 5100 boards locally, dropped them in with no other components and they are quiet as a mouse :) I also picked up a new plug pack

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Zl1XE
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Re: Modification of the Radioditty charger with "TP5100" card at $ 2.

Post by Zl1XE » Thu Oct 08, 2020 10:41 am

Hey Colin,
Where do you find them locally ?
and I'm still keen to collaborate on an NZ codeplug (but forum PM capability is gone now).
DM-1801

KI5GZK
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Re: Modification of the Radioditty charger with "TP5100" card at $ 2.

Post by KI5GZK » Sat Oct 24, 2020 5:42 am

Have any of you that have replace the original board with one of these TP5100 charge modules had a problem with your battery stopping short of charging to %100? Mine seems to stop charging when the voltage reaches 8.1 to 8.2 volts. I though these modules where supposed to charge to around 8.4 volts.

VK3KYY
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Re: Modification of the Radioditty charger with "TP5100" card at $ 2.

Post by VK3KYY » Sat Oct 24, 2020 7:02 am

It seems a bit variable

I noticed sometimes it doesn't charge back to 100%, but sometimes it does.

It's probably too intelligent ;-)

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