A homebrew ft-897 Battery



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tarix14.04.2016
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A homebrew FT-897 Battery

Here some pictures of my first attempt to build an battery for my FT897.

This one has 20 NiMh cells of 3500 mA/h , size 4/3A 1.2V, (total 7 A/h) in 2 chains of 10 cells in series.

Commercial ones have 11 cells in series , but there was no place to build 2 x 11 cells in this box.

The diodes avoid discharging the other chain when one chain is broken.

Use shottkey diodes of 15 Amp or more.


The loss is about 0.4 Volt / diode.

Diagram of batterypack

Connector for loader / PS
Do not use a pulse-loader !

With a small Power Sluppy (say 5A current limit) and 14-14.4 V out (for 2 x 10 cells) , the FT987 get his supply (via the battery ) and the battery can be loaded.

The current limit with a empty battery should be approx. 700mA (C/10 amps).

By using the battery-connector in the FT897 it switch automatically to 20 W.

For the box I did use Alu U-profile (25 mm) and plastic plate (0,5 mm thick) , cut for the top , bottom and isolation.



Battery-connector in the FT897 (NC = not connected)


So far:
1- With 10 cells in series the voltage is to low, 11 is better.

2- I did not measure the time you could use it but , I think it is about 6 hour.

3- Watch for short circuit !

For isolation small pieces of plastic you can use.

4- I advice you to add a fuse for short circuit protection.


I know that this is not a perfect design but it gives you maybe an idee how to do it.

'73 de Peter



pe1dcd@amsat.org


Page of PE1DCD 14-04-16

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