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Mar 31, 2019, 01:31 PM
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Futaba 12z, 14mz battery pack rebuild - with pictures

Hi everyone,
my old but trusty Futaba 12z still performs nicely but the battery life is disappointing. If I remember correctly the radio draws about 500mA when transmitting. The genuine battery pack is expensive even for Futaba's standards. The quality alternative - NP-F570 from Sony is also difficult to get. There are only aftermarket batteries with unknown cells from China. What is even worse is that the battery capacity is not more than 2200mAh for the genuine one and surely less for Chinese knock-offs.

I decided for finding the highest capacity 18650 cells from a reliable source and rebuilding the battery pack. I settled on NCR18650B from Panasonic.
Detailed tests here: Panasonic NCR 18650B.. Alternatively, NCR18650GA would work too. Some side-by-side comparison is here.

#1: Get genuine Li-Ion cells. Ideally, use a local electronic components distributor. I bought mine from for about 9 USD each. I tested battery voltage in the store to make sure it is not old stock. Both batteries had 3.93V. Use only cells with the identical voltage not lower than ~3.2 V.

#2: Open the old battery. I used the blade from a hobby knife. Put it in the crack and start hitting it with a small hammer from the top. This will cut most of the tabs but the ultimate result looks good.

#3: Remove cells from the compartment and clean the old silicon-like glue. Trim tabs or their remains, if needed. You need to de-solder contacts from the PCB.

#4: Put new cells in and mark when the soldering joint will be.

#5: Add solder to the battery terminals. Use some protective tape to avoid shrinking the battery insulation.

#6: Solder batteries to the terminal. Do not use any corrosive flux. You need a properly sized tip. I used my Weller WSD81 set to 320C, WSP80 with the D soldering tip, FL22 flux and leaded solder. Note that I added some paper inserts under terminals. This prevents hot flux from leaking under the battery plastics.

#7: Use the same approach for the other side of the battery. I used the metal bar from the old pack. I don't mind the protection circuitry and I do not want it in my radio. (no rant please, I removed electronics from my previous 8FG right after bringing it home).

#8: Clean soldering joints with a cotton swab and isopropyl alkohol.

#9: Check the polarity one more time.

#10: You can glue (e.g. 5min epoxy) or tape the plastic back together. If you were precise the pack will look like new.

Good luck, have fun.

Note: It seems that the genuine battery charger has a safety timer which causes the charger stops charging the battery even when not completely charged. Since this battery pack now has a significantly higher capacity, try to put the battery pack back to the charger. If the "Charging" LED turns off after a minute or so, the battery is charged. Otherwise, it continues charging. Alternatively, you can check for the final voltage (8.4V).

Note2: I've just found another thread with the exact same procedure. However, the thread is locked.
Last edited by; Apr 01, 2019 at 03:23 AM. Reason: Tried to improve my grammar...
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Mar 31, 2019, 02:42 PM
Registered User
Originally Posted by
Hi everyone, my old but trusty Futaba 12z still performs nicely but the battery life is disappointing.
Futaba is still kicking over there and it's still more popular than the local brand.

btw it's rather hungry 500 mA consumption ?
Mar 31, 2019, 03:45 PM
Registered User
Thread OP
Originally Posted by reverse
Futaba is still kicking over there and it's still more popular than the local brand.

btw it's rather hungry 500 mA consumption ?
Yeah, In my opinion 500 mA is a lot. On the other hand the 12z is built like a tank and I love it as much as I love my thinkpads collection. Golden era of engineering, I would say.
Apr 01, 2019, 02:02 AM
Julian T
Nice work warhawk. I bought a cheap after market pack and regretted it after it went open circuit with no warning - that cost me a very nice sp400 pylon racer. I then bought a Duracell replacement pack and it has been fine - it is now 3 years old. I agree about the 12Z - great ergonomics, great reliability, and great robust construction as well as absolutely reliable link - a bit heavy compared to my 18SZ though.
Apr 02, 2019, 03:18 AM
Registered User
Sorry, double post.
Last edited by jescardin; Apr 03, 2019 at 08:01 AM.
Apr 02, 2019, 03:19 AM
Registered User
Hats -off to the luxury step by step guide by!.

Thanks, sir for your effort.
Apr 03, 2019, 02:44 AM
Registered User
Thread OP
Thank you guys for your compliments. It is motivating. :-)

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