Saber repack 6 or 7 NiMh cells

[bradlington]

Good day
I am wanting to repack my dead Saber battery pack .

6 cells would give nominal 7,2 V

7 cells would give nominal 8,4 V

7 cells can fit into the pack , has anyone else run 7 cells for the slightly higher voltage.

These units can run on vehicle chargers etc so they should be able to handle the small increase in nominal voltage .

Look forward to hearing from anyone who has done this .

Thanks in advance.
Brad

[Tom in D.C.]

Brad,

Some random thoughts on the questions you've asked:
The actual voltage of a fully-charged Saber battery already is usually about 8.4 volts. Increasing the battery's voltage isn't going to get you anything except possibly shortened radio component life. The vehicle chargers you mention have voltage regulating devices in them, so the applied voltage is far below 13.8 volts DC. If your need is for longer battery life then you could consider lowering the high power setting in the radio since it's adjustable over a very wide range. The key to longer battery life while NOT cutting the radio's power is by increasing the current capacity of the battery rather than by increasing the battery's voltage.

Regards,

[bradlington]

Hi Tom

Thanks for the confirmation on the 8,4 Volt being nominal .

Will look at the additional cell in order to get the pack to the correct voltage .

Thanks

Brad

[Tom in D.C.]

Brad,

Actually the nominal voltage total of six NiCd cells would be 7.98, with each cell being added in at 1.33 volts. The 8.4 is what you'll usually read at full charge, even though the design center is 1.33 (some people use 1.2 but that's actually too low). The radio will run all day at anything between 7.2 and 8.5 volts, but at some point it will drop dead, depending on the condition of the cells. Point I was making is that for longer life you need more current capacity, not more voltage. Stick with what Motorola designed because they usually know what they're doing. BTW, what's your method for taking the Saber battery pack apart without destroying it?

Regards,

[Batwings21]

If you are looking to increase capacity, I think the saber batteries used sub-c cells. Those cells are popular for electric rc car racing (the serious crap, not the toys) and when I stopped racing several years ago we were up to like 4200mah batteries. The matched sets of cells were available in 6 or 7 cell sets too. The 4200's were nimh, but there were at least 3300 mah nicad's.

[bradlington]

Hi

Tom I have done two batteries with 6 cells so far and one with 7 , the latter I placed a diode incorrectly so I will have to take that one apart again.

Regarding taking them apart I did the following two methods ,

First method:Drill a 6mm bit throgh the base of the pack at either edge , then with a bent style long node I managed to get the base cap off and bending it too much to reuse.

Second method: Tap a small flat screw driver around the seal of the bottom battery cap and once it starts to split it gets easier.
If all goes well then one can reuse the base cap without any overall damage.
I will be cutting out some bakerlite to replace the method one battery .

I also want to try quick heating the base of the battery to soften the case slightly - this is not advised to a mechanically unsain person holding a blow torch.

I wander if anyone else has some good ideas to speed up the process.

Regarding the wiring , I have been using normal silver coated multistrand wire and good solder with flux.The purist may say this is not ideal , bur\t the original spot fasterning used has a minute contact point so go figure.

The last thing to mention is that from the IS type of battery that has the orange safety switch, it has a whole PC board in the top of the battery .So there are some differnt wiring of the batteries , included are in some bi-metal strips , and temp sensors etc.

[N9LLO]

Try putting the old battery in the deep freeze for a while. Then give it several sharp hits on the seal line. I used a small hammer that came with some kids toy set, never tried it on a saber battery but worked pretty on some others I have done.

[bradlington]

Here is my final result.

Added an old Icom battery pack charging module/circuit board and it allows me to use any 12V cigarette lighter or Icom wall charger .

Also has no impact on charging in the normal saber charger.

http://zs5bg.repeater-builder.com/index.html

[Tom in D.C.]

Brad,

I am green with envy about your having an entire building for a ham shack, which is not really a shack at all.

Regards,

[bradlington]

Hi Tom

I have a very busy ham life with having many uhf and club vhf repeaters and all my "radios" collected over the years.

I did put a lot of time and effort into the earthing etc but there is still a lot to do .Before I got married and had children I had a whole double story house and huge garage with radio stuff in .

Each room was a differnt project area.

Had to give up multiple 9 ton trucks that I dumped in order to make way for the family .(WELL worth it .)

I am one of those radio horders and can literally make anything by looking in my bits and pieces.

Thanks

de
Brad