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Old 23rd Aug 2008, 11:03 pm   #1
mark pirate
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Question PP9 rechargeable

Hi all, i have several sets that take pp9 batteries & as we all know these are getting expensive & harder to find, so i am in the process of making a rechargeable version using a stripped out ever ready battery, but should i hard wire 8 battery together to get 9.6v or 7 to get 8.4v? will .6 volt make a difference?
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Old 23rd Aug 2008, 11:12 pm   #2
Peter.N.
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Default Re: pp9 rechargeable

Hi Mark

Ideally the higher voltage would be better as a new PP9 would be well in excess of 9V, but from a practical point of view, unless you want to get maximum power out with as little distortion as possible, 8.4v should suffice.

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Old 24th Aug 2008, 1:01 am   #3
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Default Re: pp9 rechargeable

As Peter says, you won't notice much difference in practice. Maximum volume will be a bit higher with the higher voltage but this won't be apparent in normal use.

Paul
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Old 24th Aug 2008, 7:45 am   #4
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Default Re: pp9 rechargeable

Thanks chaps, From the construction point of view, it makes life easier to use
8 aa rechargeables, one of the reasons i came up with this idea is that i bought a job lot (63) of 1800mah nmh ex-equipment back up batteries for £8
at my local car boot sale, these are already soldered at both ends as they were hard wired before, i cleaned off the solder on 4, gave them a charge,
& they last as expected in my digital camera, so have plenty of life left
I have 2 pp9s to build up (now my hacker will see some use!) will post some pictures/method of construction when completed.

Mark
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Old 24th Aug 2008, 10:00 am   #5
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Default Re: pp9 rechargeable

As promised, here is how it went (see pics)
1) carefully prise the metal outer case lip away from the plastic bottom.
2) Bottom can now be removed intact.
3) Push down on the top of the battery to extract old contents.
4) Out it comes!
5) Ready to start build.
See following post for next stage.

Mark
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Old 24th Aug 2008, 10:14 am   #6
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Default Re: pp9 rechargeable

Part 2....
6) Contents well past their sell by date
7) Tape together 8 AA batteries....
8) connect together in series using tinned copper wire & solder on flying leads
9) solder flying leads to original battery terminals, re-stuff with 'new' ni-mh battery pack, fill the spare space in the battery case,(i used some polystyrene packing that was lying around) re-fit the plastic bottom & bend over & crimp the metal battery case with pliers.
10) The finished battery
A fiddly, but easy job & will save some money.
Not to the high standards of Batterymaker1, but it does the job!

Mark
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Old 24th Aug 2008, 1:16 pm   #7
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Default Re: pp9 rechargeable

looks good i did a simaler thing some time ago but using a more modern battery with a plastic case which i cut in half and fitted with 8 alkaline AA's in a holder might try it again but with rechargables what are you useing to charge it?

jay
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Old 24th Aug 2008, 1:23 pm   #8
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Default Re: pp9 rechargeable

Decent job, Mark - nowt wrong with it at all
If it saves money ....
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Old 24th Aug 2008, 2:47 pm   #9
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Default Re: pp9 rechargeable

Hi Jay,
Quote:
looks good i did a simaler thing some time ago but using a more modern battery with a plastic case which i cut in half and fitted with 8 alkaline AA's in a holder might try it again but with rechargables what are you useing to charge it?
I have made a lead using the top of a pp9 battery to a pp3 socket that then plugs in to my charger

Mark
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Old 24th Aug 2008, 9:28 pm   #10
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Default Re: pp9 rechargeable

Great save with the metal battery.

You all will laugh at this--

When I first ventured into British radios around 1999-2000, I wondered if it was possible to make a replica metal PP9--in paper.

After a few months teaching myself a perverse form of origami, I did this.

Ironically, I found out early PP9's were standard cardboard boxes. So, it didn't go any further than this developmental stage...

Bill
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Old 24th Aug 2008, 10:50 pm   #11
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Default Re: pp9 rechargeable

Hi Bill,
Quote:
Great save with the metal battery.
From you, great praise indeed I now wish i had saved some of the old batteries that were in some of the sets i have bought over the years,
it's been a long time since i saw a cardboard pp9

Mark
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Old 25th Aug 2008, 12:10 am   #12
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Default Re: pp9 rechargeable

As long as all the cells are at the same charge level initially this should work fine bear in mind though that the output voltage from these cells will be much more stable under load than that from the original PP9.

What type of charger are you using? Is it a Delta V type (one which automatically detects the fully charged state) - these are the best approach with single cells but I'm unsure about their performance with a battery - or a specific charge current/time regime?


Cheers
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Old 25th Aug 2008, 3:34 pm   #13
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Default Re: pp9 rechargeable

Mark Pirate

Nice job and sorry to put a damper on this but....you must not solder directly onto these cells. There is a plastic vent under the top of the +ve connection of these cells. This acts as the seal for the contents but allows gas to vent. Soldering destroys this device. That is why the tags are always spot welded onto them and why, when you buy them they are sold as tagged or non-tagged. If you intend to solder them together you must obtain the tagged type.

What you will probably find is that after a time you will get a white deposit around the positive terminal and some of the cells will swell.

I see from your original post that you mention hard wiring but I don't see any from the pictures. Normally the tags are like thin metal tape spotted to the cell terminals.

TimR
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Old 25th Aug 2008, 5:47 pm   #14
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Default Re: pp9 rechargeable

Quote:
Originally Posted by flyingtech55 View Post
Mark Pirate

Nice job and sorry to put a damper on this but....you must not solder directly onto these cells. There is a plastic vent under the top of the +ve connection of these cells. This acts as the seal for the contents but allows gas to vent. Soldering destroys this device. That is why the tags are always spot welded onto them and why, when you buy them they are sold as tagged or non-tagged. If you intend to solder them together you must obtain the tagged type.

TimR
Hello Tim.
I think you may be wrong here, I have loads of Ni-Mh batteries, the usual ones you can buy anywhere and none of them have a vent hole. I do have some quite old Ni-Cad batteries that do have the vent.
So I donned the rubbergloves and cut off the top of an old duff Ni-Mh and as far as I can see the small insulating plastic piece between positive and the body will act as a one way flap thus venting any pressure although this would be tiny anyway. I am not saying this is the same in all Ni-Mh batteries but the "Uniross 2500" would all appear to look the same.
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Old 25th Aug 2008, 8:09 pm   #15
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Default Re: pp9 rechargeable

Looks like a good job to me .

Up until a short while ago, I had one of these http://uk.rs-online.com/web/search/s...duct&R=0229059 in my Marconi LCR bridge. The replacement price is rather high so I may resort to building a rechargeable like yours!



Rich.
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Old 25th Aug 2008, 11:37 pm   #16
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Default Re: pp9 rechargeable

Hi all, firstly, the batterys i used had already been soldered & do not seem to
have a vent hole & had been in use prior to me getting them & do not seem to
have suffered ill effects, the batterys flyingtech refers to must be different types to these, after a look at some of my rechargeable AA size, i found that some of my older ni-cads had the vent hole plainly visible.
I have built another 2 today (to power my hacker herald) i have not fitted the bases in yet as i have run out of polystyrene to pack the space in the battery, so will run them like this for a couple of weeks so i can keep an eye on them.
Quote:
The replacement price is rather high so I may resort to building a rechargeable like yours!
Go for it richard, i have had my 70s itt running all day for 2 days now & the
Thought of not having to buy another pp9 again is very pleasing

Mark
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Old 29th Aug 2008, 9:34 pm   #17
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Default Re: PP9 rechargeable

Hello
I'm trying to reach Bill (BATTERYMAKER1)


Thanks

Jodie Wells

Lexington, KY-USA

Last edited by Brian R Pateman; 29th Aug 2008 at 9:42 pm. Reason: E-mail address removed - please check Forum Rules.
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Old 29th Aug 2008, 9:45 pm   #18
Brian R Pateman
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Default Re: PP9 rechargeable

Hello Jodie and welcome to the forum.

The best method of getting a message to Bill is to send him a PM. You can do this by locating his entry in "Members List" at the top of this page. Then use the link you'll see there.

Regards,
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Old 7th Oct 2008, 1:08 pm   #19
kalee20
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Default Re: PP9 rechargeable

RS still sell rechargeable PP9's, £30 each (their stock number 229-059). Capacity 1.3amp-hours; voltage 8.4V.

Somehow I thought they might have been discontinued, but they haven't!
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