CHANGING THE "Memory Battery BA1" IN THE Kenwood 850s RADIOS

Having heard the stories about the Kenwood 850S memory battery leaking onto the circuit board and cable connectors I made the decision to change mine immediately. Immediately became several months as I procrastinated and instead focused on finishing up the rebuild of my two Dentron GLA-1000 amplifiers. Finally got into the radio and was very relieved to see my battery had not leaked. I had read all the posts on the Kenwood repair page, (http://www.jzap.com/n6tr/850repair.html), about the replacement procedure but was intimidated by the very thought of opening up something a lot more sophisticated than anything I had ever worked on. I decided it was worth a try instead of taking a chance on the radio being damaged in transit to a repair shop just to change a battery. The factory installed battery is a CR-2430 rated at 3 volts dc at 285 mAh. Two of the pins are negative (bottom) and the positive one is at the top. Coin type batteries can also be purchased that do not have attachment pins. These are made for use in coin type battery holders. The holders have the attachment pins.

1. Decide whether or not you want to permanently remove the battery from the circuit board and relocate it for easier access. I chose to move mine and mounted mine along side the fan in a rubber boot. The rubber boot was glued onto the adjacent vertical panel with RED RTV. The coin type battery holder I used fit in the boot it just right. The bottom of the boot is plugged with more red rtv to prevent any battery leakage from leaking out. I soldered wires into the holes on the circuit board where the original battery had been mounted and then ran them to the new location. They are small wires so use stranded wire and tin it before trying to push them in the holes on the circuit board.

2. If you choose to leave the battery on the circuit board I highly recommend you purchase a battery holder made for the CR-2430 coin type battery and solder it onto the board. This will permit you to replace batteries in the future without having to desolder and resolder the old battery. Just pull the old battery out of the holder and slide the new one in. Radio Shack does not carry battery holders for the CR-2430 so shop around. I know Newark Electronics has them Newark Part#46F857 (Type 105). These are made for all 24 mm diameter coin type batteries.

3. Decide whether or not to go to a different battery and battery holder that is easier to lay hands on. I chose to go with the CR-2032 coin type battery (Radio Shack Part# 23-162) with the appropriate battery holder (Radio Shack Part# 270-430). I wanted something locally available and didn't want to have to buy large minimum quantities in order to get one!! The CR-2032 battery is a little smaller than the CR-2430 battery Kenwood installed in the 850S and is rated at 3 volts Dc at 200 mAh. Same voltage as the CR-2430 (3 vdc) but has 85 fewer mAh than the CR-2430. Just means it won't last quite as long. I decided this was not a critical issue and besides I was going the change the battery more often now that it was only going to be a 10 minute job!!

4. "Danger" If you do not have really good eyesight and a steady hand let someone else do the job for you. The circuit board has many surface mount components on it that are very easily damaged. In addition the circuit board traces are very, very small and burn apart easily. A little too much heat applied to this board and off the Kenwood you must go for a new one!! In any event use a soldering iron with a very sharp point at about 15 watts.

5. Ok you have decided you are up to the task. Do you remove the circuit board completely or just tilt it back for access to the back of it. I chose to just tilt mine back so I wouldn't have to unplug all the little ribbon cables. I only unplugged what was necessary to access the back of the board. I had plenty of room this way. I will grant you that removing the board from the radio would be better but I was concerned that I would not be able to get all the cables back where they belonged. I did mark them but found that some connectors are labeled with the same description. I still had to unplug many cables anyway!!

3. Take out the two screws on both sides of the front panel. Once out the front panel will tilt down so you can access the circuit board cables and the screws holding it onto the back plane.

5. Either unplug all the cables and remove the board or unplug enough so you can tilt the circuit board back enough to work.

6. Desolder the old battery and remove. "Take Your Time and Watch the Heat" It is better if you can cut the pins on the old battery then just remove the pins. Cut the top pin first so you can bend the battery down for access to the bottom pins. I found it easier to leave the bottom pins attached to the battery and heat the solder on the back of the board enough to pull them out one at a time by gently rocking them. In addition this let's the old battery become a heat sink and may protect the adjacent components and circuit traces.

7. Solder in the wires, a new battery or the appropriate battery holder. "Watch the heat"

8. If you chose to stay with the original battery design plug in the cables you have removed and reattach the circuit board to the back place with it's screws. If you chose to install a battery holder for the original battery slide in a new coin type CR-2430 battery then reattach all the cables. Now if you choose to move it to a more accessible location like I did you need to use heat shrink, tape or an insulated boot to isolate it from the inside of the radio.

TIP: Put all the screws in a secure location so you don't loose them. I marked them as to where they came from and put them in camera film boxes.

Model Number	Capacity (mAh)	Dimensions (mm)					Weight (g)
Model Number	Capacity (mAh)	A	B	C	D	E	Weight (g)
CR 2016 RH	75	20.0	20.2	15.2	3.95	7.95	2.0
CR 2025 RH	148	20.0	20.2	15.2	4.85	8.85	2.8
CR 2032 RH	200	20.0	20.2	15.2	5.45	9.45	3.3
CR 2032 RH1	200	20.0	20.2	17.8	5.45	9.45	3.3
CR 2325 RH	190	23.0	23.2	17.8	4.85	8.85	3.3
CR 2430 RH	285	24.5	24.7	17.8	5.45	9.45	4.4
CR 2430 RH1	285	24.5	24.7	20.4	5.45	9.45	4.4
CR 2450 NRH	540	24.5	24.7	17.8	7.35	11.35	5.9
CR 2450 NRH1	540	24.5	24.7	20.4	7.35	11.35	5.9
CR 2477 NRH	950	24.5	24.7	17.8	10.05	14.08	8.4