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Silver PP9 capacity

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Silver PP9 capacity

Post by Refugee » Tue Nov 12, 2013 2:38 am

I bought a couple of these batteries at a branch of a reputable hardware store and have run one in a daily use Bush TR82 and it lasted between two and three weeks.
I have also tried eight 2000mah low self discharge NiMh cells giving 9.6 volts so that the set runs as if it is on a fresh PP9 and from the supplied charge it ran for over a week.
The only data on these batteries if from Farnell and they quote 4500mah.
I have read on the web that there are Hacker owners claiming that there batteries last months on end.
I am proposing to re-stuff one with the NiMh cells and make a charger.
First I will test the set on 7.2 and 8.4 volts and see how well the goes and how long it lasts.
If I choose 7.2 volts I may be tempted to install a small charger in the case with a detachable power cord.
I opened the flat one and found that The cells are spaced with offcuts of paper and card board to stop them rattling about.
These plastic cased batteries are much easier to open up that the older metal clad types.

DSCF9140.JPG


The early signs of the rot setting in can be seen. This would indicate that leaking would not be that far off.
Any thoughts on these batteries.
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DSCF9152.JPG

 
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Re: Silver PP9 capacity

Post by Terrykc » Tue Nov 12, 2013 11:05 am

Have you checked the current consumption of the TR82? Either those batteries are rubbish or the drain is excessive.

 
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Re: Silver PP9 capacity

Post by Michael Watterson » Tue Nov 12, 2013 11:07 am

They are about 4000mAH to 5500mAH depending on load. At 100mA the capacity might be only 1000mAH due to internal resistance.

Typical load is about 15mA (Depends on volume) in a Hacker. Certainly less than 25mA in your set unless it's got leaky caps.

You got rubbish batteries. The shelf life is low if stored too warm. Also ALWAYS check date code when buying layer cells or Zinc Carbon or Zinc Chloride. The Alkaline can last years beyond date code.

NiMH / NiCd are rubbish for this as the capacity will be compromised by the high self discharge. You'll get the equivalent of 500mAH to 1500mAH from 2500mAH NiMH depending how solidly you listen. The more intermittent the use, the WORSE it is! The AA size NiMH (or NiCd) are designed for HIGH current drain applications (100mA to 1A) using up the charge in 1 to 20hrs of use.

A better choice is cheap Alkaline AA cells: The shelf life is up to 10 years (depends on temperature) vs 2 weeks to 2 months for NiMH or 1 year for 1800mAH Eneloop type NiMH. The capacity at 15mA draw is close to 2800mAH. Cost is low if you avoid Duracell/Energiser.

The Layer cells are nearly twice capacity of cylindrical Zinc Carbon, but only at low current draw, nearly as good as Alkaline. At higher draw the Alkaline is much better. NiMH is as low as half usable capacity of Alkaline in low current draw applications ( < 1/50th C) but up to x4 Alkaline capacity at very high current draw (1C). At 1/100th C rate Zinc Carbon cylindrical cells are about 1/2 capacity of Alkaline, but this falls to 1/5th at about 1/10th C .

Layer cells are only good for "louder" radios in 2 x 9V = 18V PP9 otherwise the internal resistance is too high. They were introduced between 1938 to 1940 for "All Dry" radios for HT only as that is only 5mA to 12mA, allowing half the size and less than 1/2 the weight for same capacity of "B" type Cylindrical cells. Many of the "PP" type packs are the same layer cells as used in HT packs, just less of them. The 22.5V / 15V hearing aid/Instrument layer cells smaller than PP3 type (about 1/2 capacity per cell) and the PP9 was the largest size.

So for "loud" economical Transistor sets on 4.5V to 12V the cylindrical cells used as the PP9 was the "best" and really you needed two (to have 1/2 current) for economy on louder sets.

Conclusion
Probably best to use 6 x Alkaline AA per PP9. A 3 x 2 holder fits the case. NiMH will more often be flat when you go to use the set and 6 or 12 are awkward to charge. The running time after 30 cycles charging in a PP9 radio application could be 1/5th or less of PP9 and 1/2th or less of Alkaline AA cells. Shelf time is rubbish unless expensive "eneloop" type. The 500mA NiCd actually much better shelf life and intermittent run time than typical 2700mAH NiMH but hard & expensive to get due to toxic Cadmium / RoHS.

(C = Notional Capacity in Amps for 1 hour, only actually possible at 1C for NiCd and heavy dutly Wet Lead Acid, every thing else needs reduced rate of discharge to "use" full capacity due to internal Resistance).

 
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Re: Silver PP9 capacity

Post by Refugee » Tue Nov 12, 2013 12:26 pm

The NiMh cells I am using are the type that are supplied ready charged from the supermarket and they hold there charge for quite a while perhaps more than 6 months when left on the shelf.
The set is used all day so the batteries will not be left for long before being put into use again.
I have used two 4-packs of NiMh cells that were bought at the same time and they have just been charged up for the first time and should be pretty well close to there marked capacity in the first few cycles of charging so I have for the time being been using them as a crude currant drain test.
The set does have a couple of the red-black-tape capacitors in it that may need replacing if they do not reform over the next few weeks use.
I have a enough physically larger NiMh cells from 386 laptop batteries that used to suffer corruption of the internal memory rendering them useless for there original purpose. I have used 6 of these and most of the original case. This was an inverter for a Megger I have that would have had a mains power supply when new. It is fitted with a wall wart point for charging via an internal resistor from 12 volts.
Has anyone done of there own trials on these supplied charged NiMh cells?
The date code looks fine to me.
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DSCF9141.JPG

 
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Re: Silver PP9 capacity

Post by Michael Watterson » Tue Nov 12, 2013 1:00 pm

Unless it's week 16 2002!

2016 sounds unlikely for a layer cell. But check the current drain should be maybe < 10mA at zero volume. Any more than about 25mA at gentle volume suggests a problem!

NiMH need trickle charged and the long shelf life kind are damaged by leaving them on charge once they are charged fully. The "ordinary" NiMH need under 1/10th C once more than 3/4 charged. (i.e. about 15mA).

I've used NiCd and NiMH in many designs. I suppose about viable in a PP9 if using it 10 hrs a day. But I'd use 7 x NiMH vs 6 x Alkaline, though 6 should be fine. But longest life if you recharge when 1.1V (6.6V for 6) rather than "flat" or radio starting to work badly. Below 1.1V there is the risk that one of the 6 cells will get reverse charged.

 
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Re: Silver PP9 capacity

Post by Refugee » Tue Nov 12, 2013 1:10 pm

I will most likely be going for 7 cells and also the radio is used mostly for radio 4 as the FM in my area is very poor until I get an outside antenna up.
I will not even look at DAB here as we are in a valley with only a narrow east facing gorge that is below the level of the house.

 
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Re: Silver PP9 capacity

Post by malcscott » Tue Nov 12, 2013 1:21 pm

I have a couple of transistor radios which i have converted the PP9 to 8 x 1.2v ni-cad. When fully charged they last ages with regular use.

 
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Re: Silver PP9 capacity

Post by sideband » Tue Nov 12, 2013 1:31 pm

Refugee wrote:I bought a couple of these batteries at a branch of a reputable hardware store and have run one in a daily use Bush TR82 and it lasted between two and three weeks.
I have also tried eight 2000mah low self discharge NiMh cells giving 9.6 volts so that the set runs as if it is on a fresh PP9 and from the supplied charge it ran for over a week.
The only data on these batteries if from Farnell and they quote 4500mah.

I have read on the web that there are Hacker owners claiming that there batteries last months on end.


I have a couple of Silver Ever Ready PP9's. One has been in my TR82 for over a year and is still giving around 8.9V on load. The other was new and unused for over a year (bought at the same time as the TR82 battery as a spare, thinking that the one in the TR82 probably wouldn't last more than a month.....).

I then aquired a Hacker Herald VHF set that required two PP9's. Having restored the Herald and checked the quescent current, I then used the old PP9 from the TR82 and the new unused one. Both of these have been in the Hacker for around three months (and it gets used a lot more than the TR82 ever did) with no sign of any problems yet. My experience with PP9's is that they last a long time.


Rich


Just remembered, there is another PP9 in my Marconi LCR bridge. That's been in there since 2008 and the bridge is still working well (used it last night).

 
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Re: Silver PP9 capacity

Post by Refugee » Tue Nov 12, 2013 1:43 pm

The good thing about PP9s is that they can be re-stuffed leaving a little space for a charging circuit and wall wart socket.
I did the Megger inverter so that you just apply 12 volts to it for charging :thumb

 
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Re: Silver PP9 capacity

Post by Michael Watterson » Tue Nov 12, 2013 1:45 pm

I think it's down to storage temperature. Probably exponentially shorter shelf life with raised temp. I've had some that lasted a long time too.

Check the radio current consumption with a meter rather than how long batteries last :)

It's technically possible to fit a mains PSU and rechargeable cells in a PP9 case!

 
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Re: Silver PP9 capacity

Post by Refugee » Tue Nov 12, 2013 2:02 pm

I have several NOS 5V 200ma transformers however they are the shielded type that require an earth if they are not going to dish out static shocks all the time.
Had they been gaped bobbin types I would not hesitate to use them. I will have a look for a small footprint three terminal mains inlet that is still manufactured and see if I can squeeze it in.
I will have a look at the clover leaf type and see if that will fit.

 
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Re: Silver PP9 capacity

Post by Michael Watterson » Tue Nov 12, 2013 8:07 pm

Ultra miniature 9V transformer from a £6 Argos Clock Radio :) Or a 6V one with a voltage doubler.

You can use a resistor to set a trickle current of 10mA to 15mA and just 6 x NiMH. The Radio may have been designed to work to just under 5V (as much as possible out of the PP9), many "9V" transistor sets designed for 5V to 11V to ensure reliable operation.

 
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Re: Silver PP9 capacity

Post by Refugee » Tue Nov 12, 2013 8:33 pm

I have worked out that rectified 6 volts should be able to produce about 8 volts allowing for the diode drop so it should be all right for 7.2 volts with a lowish dropper resistor for something like 25ma or so.
Small transformers have to be de-rated quite a bit for charging service with smoothing. Mine is rated at 200ma.

 
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Re: Silver PP9 capacity

Post by Michael Watterson » Wed Nov 13, 2013 12:28 am

6V AC supply:

You can get about 14V using a doubler (16.8V peak no load) on load.

With 6 cells the trickle charge voltage rises to 8.1V pretty quick and then gradually to 9V. So a Doubler and 390 Ohms series resistor is better. Using a bridge is about 7V even on a slight load. With single diode you might get 7.6V, but that's not enough to charge 6 x NiMH.

The 390 Ohms needs to be 0.5W rated in case the cells are dead flat, current is 30mA for a very short while.

It's not going to work without a doubler. Also the higher the voltage the "better" a series resistor sets the current.

 
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Re: Silver PP9 capacity

Post by crackle » Wed Nov 13, 2013 12:32 am

Would it be a good idea to use a higher voltage source to charge Nicad/nimh batteries. I.E. 7.2 volt stack charged from a 20v source and use a larger value series dropper/current limiter. The charge current would then be more constant all the way up to fully charged. So long as the charge rate is kept reasonably low would the batteries not "float" at their optimum voltage.
Mike

edit
Michael, you posted as I was typing my reply, I think we are thinking along the same lines about using a higher voltage.

 
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Re: Silver PP9 capacity

Post by Refugee » Wed Nov 13, 2013 3:16 am

I think the 6 volts will make it take a very long time to get to full charge if at all but there are plenty more options.
Firstly I have two sets to service with these batteries and I would like to keep them all the same.
As the self discharge of the cells I am using is much better than early NiMh cells I will be making three batteries for this project in order to have a fresh one handy all the time.
The transformers I have are 6 volts so that is what I will be running with.
The cells and the transformer will fit in with space to spare even 8 cells could go in with a little bit of bracket trimming or by laying the transformer in a different position. The pins are tinned copper and can be safely bent. With a doubler I would be tempted by 9.6 volts with 14 volts for charging.
With an external charger I have some larger 2000mah cells left over from a 7.2 volt to 500 volt inverter that I built earlier that works well with an external wall wart that could be pressed into service for these too as they are tagged so no holders will be needed. There will be no space for a charger as they will not fit in with a transformer unless I only go for 7.2 volts with a tight squeeze to get the transformer in. These batteries had a short life due to excessively complicated and unreliable charge management arrangements in there previous life.
We have to remember that these nice old sets need to be running close to 9 volts here with the dismal radio reception in my area. FM is bad enough that we actually need long wave for radio 4 :cch
I have rigged an 8 cell battery with PP3 studs and an adapter for charge cycle estimates and will allow this test to to run to completion.
Attachments
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DSCF9160.JPG
DSCF9166.JPG
They over did the electronics.
DSCF9145.JPG
The trial battery pack.
DSCF8964.JPG
The 500V inverter ready for the covers to go on.

 
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Re: Silver PP9 capacity

Post by davegsm82 » Wed Jan 08, 2014 12:26 pm

I've just re-built a PP9 with 8x Ni-Mh cells which are the same physical dimensions as a Li-Ion 18650 Cell, not sure what designation they are in Ni-Mh form. No charger, that's what my bench supply gets used for, but since I have built other PP9's I'll soon be making a charger.

Those transformers you have, do you have any spare? I have an identical one which is 20 - 0 - 20 output but I need something in the region of 4.5v and I'm thinking I might be able to get away with 3v. :aaq

Fancy doing a swap?

Dave.

 
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Re: Silver PP9 capacity

Post by Michael Watterson » Wed Jan 08, 2014 1:11 pm

It might be "A" size as it's not B size and AA is a reduced size A
47.6 15.9 mm

 
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Re: Silver PP9 capacity

Post by Refugee » Wed Jan 08, 2014 1:46 pm

You need to be very careful with these little transformers.
There are de-rating tables for them when used in battery chargers.
I have estimated that it would take 48 hours to charge a set of 2000mah Ni-Mh cells.
The larger 2200mah cells in the vintage Megger pack are connected to a wall wart point on the side.
This may well be the way to go as a good quality wall wart will manage to charge batteries at much closer to its marked rating. These cells will just about fit in a PP9 case with little to spare. I have been running a TR82 on 9.6 volts as the commercial chargers only do even numbers of cells so I would have all sorts of odd ones in different states of charge laying about if I go any other way.
I have roasted laminated transformers to a cinder using therm in chargers before I found out about the de-rating tables.
The tables were on the Farnell website about 10 years ago.
You will need a resistive dropper and you will loose several volts.
For a 9.6 volt pack you will get no charge from a 6 volt transformer at all.
You would be better with a 9 volt transformer rated at 400ma minimum to get a 14 hour charge de-rating it at 50%.
The tiny transformer is not up to the job. It is best for standby use on a home made remote control appliance where it only has to run an equally tiny receiver.
I have used one in a pulsed HV generator that only pulses every few seconds and it has sat there for several years trouble free at a few ma DC.
Attachments
DSCF9497.JPG

 
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Re: Silver PP9 capacity

Post by davegsm82 » Wed Jan 08, 2014 2:39 pm

Don't worry, I don't want to use the 20v one for a charger, I actually want a lower voltage one for an LED clock that I'm re/building/modifying :bba

I've just checked the dimensions mike, they look to be the same as Refugee has posted in his picture, 18mm diameter, 65mm long, which stands to reason when you look at the Li-Ion equivalent 18650.

I can only assume they use the same designation for the Ni-Mh ones. I do have some 'A' size Ni-Mh cells somewhere, ex-medical equipment batteries if I remember right.

Dave.

 
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Re: Silver PP9 capacity

Post by Refugee » Wed Jan 08, 2014 3:00 pm

24.7 operation on constant load with smoothing always requires de-rating of the transformer.
LED clocks are the same and I have just done a check to reveal that it is 2.5W.
The little transformer in the photo is only 1.2VA so perhaps it is a little bit low even for an LED clock.
Attachments
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DSCF9508.JPG
DSCF9509.JPG

 
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Re: Silver PP9 capacity

Post by Michael Watterson » Wed Jan 08, 2014 5:54 pm

OK that size is likely a CL and is likely pre WWII called something else by Ever Ready UK.
66.7 x 23.8 mm

I have some older ERUK, I must look as my database doesn't list equivalents. I think Only the PP range isn't pre 1950. I think most NiMH non-prismatic packs (cylinders) are pre-existing Zinc Carbon sizes, but not common ones.

I've bought the very cheap Argos Clock radios just for the transformers. The other parts are useful too. Two of the MW RF coils make one valve IFT or two transistor ones.

If you measure the load power of the LED clock radio it's likely much less than 2.5W which is probably a peak input power plus a margin.

 
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Re: Silver PP9 capacity

Post by Refugee » Thu Jan 09, 2014 12:42 am

Micheal those segments are 30 years old and draw 10ma each.
11:11 is 10 segments :cch
That is 100ma for starters. Then we have a 30 year old clock chip to think about.
I would be worried about using a 1.2VA in an LED clock even though it does not in this case also have a radio.
Those recycled cells in my home made inverter came from old laptop batteries and ones with regular size cells are as rare as hens teeth as are most other laptop parts.
The cells are a bit larger than AA size.

 
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Re: Silver PP9 capacity

Post by Michael Watterson » Thu Jan 09, 2014 10:22 am

Presumably the LEDs are multiplexed. How did you measure the power?

Anyway irrelevant to using an Argos Clock Radio transformer.

 
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Re: Silver PP9 capacity

Post by Refugee » Thu Jan 09, 2014 10:30 am

I don't think so on the clock I have. It has no crystal and just counts the mains cycles.
There is simply nothing fast enough to multiplex the display.
The following generation of LED clocks did multiplex the display and often also had a backup battery.
I have not measured the power directly on mine.

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