FYI. The GD77 battery will go flat even if the radio is turned off

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VK3KYY
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FYI. The GD77 battery will go flat even if the radio is turned off

Post by VK3KYY » Thu Jan 14, 2021 6:50 am

Guys,

This is nothing to do with the firmware, but recently bought a "battery eliminator" and have modified it, so that I can supply power directly to the radio from an external PSU.

What I found suddenly quite interesting, is that the radio takes 0.7mA even when turned off.

I have checked why this is happening, and its because the power latching circuit, uses a high current FET, which has a 10k resistor as a pullup on its gate.

But when the radio is turned off, the gate is connected to ground, via the volume / on-off control on the radio.
This means that the battery is constantly discharged by a 10k resistor.

0.7mA may not sound like much, but the battery capacity is around 2200mAH when the radio is completely new.
So even if the radio is brand new, the battery would go flat in 130 days, which is around 4 months.

After just 1 month, the battery will only be 75% full. 20 months 50% etc.

So if you have more than 1 GD-77 (or DM-1801 or RD5R) and don't use the other radio that much, or if the GD77 is not your main radio, I recommend you remove the battery when not using it.

Because eventually the 10k resistor may flatten the battery so much that it damages the chemistry of the battery .

This will also apply to the Baofeng DM-1801, but not the Baofeng RD-5R

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m1dyp
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Re: FYI. The GD77 battery will go flat even if the radio is turned off

Post by m1dyp » Thu Jan 14, 2021 8:35 am

interesting info, thank you
73 de Ken :D

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Ik0nwg
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Re: FYI. The GD77 battery will go flat even if the radio is turned off

Post by Ik0nwg » Thu Jan 14, 2021 8:38 am

usually it is the devices with the non-mechanical power button that have these battery consumption problems even if they are off ....... there are so many strange things ... on the rt3 retevis you have to pay attention to the contacts of the batteries that are used for recharging because they are powered and therefore if they touch something metallic there is trouble ..... the yaesu vx1 ... vx2 .... vx3 ..... they all have problems on the power button and on the selector rotary encoder ........ ft817 problems selector rotary encoder .......... and I'll stop here because otherwise the list would be very long
ciao Roger
Sal jn61vg Italy

VK3KYY
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Re: FYI. The GD77 battery will go flat even if the radio is turned off

Post by VK3KYY » Thu Jan 14, 2021 8:51 pm

Thanks Sal

I agree. The exposed terminals on the battery can be dangerous.


BTW.

I noticed the battery on my DM1801 was only 50% full when I turned it on, and I thought initially that perhaps the battery had a fault.

But the new measurements I make of the GD77 current consumption, show that this will be a problem with many radios.

I just check my GD-73 (which I never use), and the battery indicator was showing that the battery was completely flat.
So I am now charging the battery, and I will remove the battery after its finished charging


FYI
Something I do on other devices like some old mobile phones which I'm not using, is when the battery is about 95% full, I remove the battery (as this is possible on some older phones), and place a piece of paper over the battery connections and I then refit the battery

Unfortunately with my newest phone, (Android) its not possible to open the phone to disconnect the battery, and its the same in all my Android tablets :-(

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F1RMB
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Re: FYI. The GD77 battery will go flat even if the radio is turned off

Post by F1RMB » Thu Jan 14, 2021 9:12 pm

grinder.jpeg
grinder.jpeg (6.38 KiB) Viewed 222 times
73 de Daniel.

VK3KYY
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Re: FYI. The GD77 battery will go flat even if the radio is turned off

Post by VK3KYY » Thu Jan 14, 2021 9:18 pm

F1RMB wrote:
Thu Jan 14, 2021 9:12 pm
grinder.jpeg
LOL.

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F1RMB
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Re: FYI. The GD77 battery will go flat even if the radio is turned off

Post by F1RMB » Thu Jan 14, 2021 9:22 pm

;-)

About the exposed energized tabs on the battery pack, the MD-380 has also this problem. The MD-390 not, as it's designed to be waterproof.


Cheers.
---
Daniel
73 de Daniel.

MikeyMDR21
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Re: FYI. The GD77 battery will go flat even if the radio is turned off

Post by MikeyMDR21 » Fri Jan 15, 2021 10:51 am

The batteries on the GD-77 aren’t great IMO.

I’ve got two of these radios. Purchased at roughly the same time.
Both batteries discharged without use. One has died completely and wont charge at all now. The other shows 100% when charged but drains fairly quickly when scanning.

The annoying thing is, I can’t find replacements anywhere.
Tried Radioddity directly but they’re out of stock and have been for a while. No joy on eBay or Amazon either.

I’m loathed to accept that perfectly good radios are at the end of their life due to lack of battery replacement options.

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