TYT MD390 charger

Modifications to this charger so it does not overcharge the battery.

I have a Tyt (Tytera) MD390 DMR radio.
The charger does not work well.
1) It overcharges the battery up to 8,6 V where the maximum for a 2 cell Lithium battery is 8,4 V !!!
2) The green/red charge indication changes to green long before the battery is fully charged.
The charger can supply 500 mA of charge.
The green indication comes on already when the current is < 160 mA.
Normally a full indication comes when the current is dropped down to C/10 = 50 mA.

So NEVER LEAVE THE BATTERY IN THE CHARGER, remove it immediately when the charger goes to green!!!

Or make this change to the charger and be safe.

The modification changes the Voltage from 9,25 V to 9,1 V and the green threshold to 50 mA.
It seems the battery has two diodes between the charging terminal and the battery itself.
This is why the charger output is higher than the battery voltage.
This is probably made so the charging terminals have no voltage under normal use.

Here you can se the circuit and what to change, or see the MD390_charger in pdf:

Here the mod on a “V2” board made by another ham, thank you for sharing

Min nye hjemmeside