TKR-750/850 Repeaters

[cbrrider06]

Question for the group. Our local ham radio repeater(s) are the 750 and 850 respectively. I have noticed there is a battery back connection on the back and would like to utilize that power failures. I have spoken with the owner, and they have said that there is a mod that needs to be done to properly use the battery back up, is this true? Also, from what I am reading is this connection also provides a trickle/float charge when not used. The question with this, is there a particular battery that needs to be used (Lithium, lead acid, AGM, ect.). Also, does the size of the battery need to be a certain size (certain amp/milliamp hour)?

 

[ramal121]

All the mod does is to connect a current limiting resistor to the battery side for a trickle charge. It only supplies a few hundred milliamps and I really don't care for this. I prefer to leave the trickle charge undone and keep the batteries maintained by a better smart charger that can supply several amps to make sure the battery is fully charged after a deep discharge cycle.

Use any battery you'd like but you'll get the longest life from one that is standby rated and deep cycle. And match that with an appropriate charger for the chemistry. As far as size, that's up to you. Calculate the duty cycle used during battery operation and match that with the time you want the repeaters to operate. Usually 50 to 100 Ah per repeater will give you many hours of use until you need to scrounge up a generator.

 

[tlemke940]

in my area we use those radios too and what we do is we have a unit like a samlex sec-100 and use it to power the whole site and use battery's (normaly AGM) off of that unit and have another charger to boost charge after an outage. i don't know what all you have running for your site but this tends to work best for us due to it also powers the amp and controller and what ever else is needed like a light due to it is normally dark and/or storming when the power goes out. we went away from thae port on the back due to it only backs up that one device and is minimal trickle charge.

this is what i pulled from the manual about that port hope this helps

This unit has two external power supply connectors :
Main DC and Backup.
If an external DC power supply is connected to the main
DC connector and a backup battery is connected to the
Backup connector at the same time, the DC power supply
switches to the battery automatically if power failure occurs.
Therefore, the operation of the repeater can be continued.
If the battery is used, but both the battery and power supply
need not be connected (if an external switch is used or if
only a solar battery is used), connect it to the Backup connector,
not the Main DC connector. Current consumption
can be reduced by approx. 120mA because the relay is not
used.

3. Trickle Charge for Backup Battery
If the external DC power supply is connected to the Main
DC connector and a backup battery (12V rechargeable type)
is connected to the Backup connector at the same time, the
battery can be trickle-charged from the external DC power
supply with a maximum current of 0.5A.
Short the CHARGE land near R61.
Notes :
1. Make this modification after removing the DC power supply
and battery for safety.
2. When the DC power supply is connected after the modification,
DC voltage is output to the Backup connector.
Be careful during setup.
3. When the backup battery is used for a long time, remove
the battery from the repeater and recharge it because the
trickle charge is not sufficient for recharging a completely
discharged battery.

 

[NewJerseyOldListener]

My suggestion for a backup battery.

https://amzn.to/3NYSqUR