9v rechargeable batteries

[TEAMYAKIMA]

Hello

 

My layout uses handheld walk around 'radio' throttles - four of them.

 

They are powered by 9v (or ideally slightly more) rechargeable PP3 style batteries

 

Once the batteries give out less than about 8.5 v the throttles are prone to die

 

I have a collection of 8/9 rechargeable batteries of a couple of different brands and I must admit that I have never done any analysis of exactly which brand dies quickest - when the y die at an exhibition its just been a panic to replace them ASAP!

 

 

 

 

I have heard that there is a limited number of times that you can recharge rechargeable batteries - is this true?

 

We are off to Warley in 2 weeks and I don't want the stress of failing batteries - any advice?

 

Edited November 10, 2019 by TEAMYAKIMA

[wasdavetheroad]

On your visit to Warley replace the rechargeable batteries with good quality normal ones. I have just bought an Energiser max plus that I tested at 9.6V Alkaline batteries should have more capacity than rechargeables but you only get to use them once.

 

Have a look here https://rightbattery.com/525-9v-energizer-alkaline-battery-tests/

 

It appears that the batteries are only 8.5V for a short time!

 

I use 9V batteries in my radio control 'throttles' but they run on 3.1V via a built in step down voltage regulator.

Edited November 10, 2019 by wasdavetheroad

[WIMorrison]

3 bits of advice;

 

1) yes there is a limit which is as low as 500 times for the cheaper end to 1200 times for better quality 

 

2) batteries have a memory effect and gradually lose the about to hold and deliver a charge when recharged before completely flat.

3) you only get what you pay for and  £1.99 rechargeable is not as good at a more expensive.

 

You should buy LI batteries to get the lowest self discharge, largest recharge cycle count, lowest memory effect 
 

 

 

 

 

[melmerby]

PP3 rechargeables used to be 8.4v.

I've had few over the years but now don't have any kit that uses that size.

[Crosland]

Memory effect was discovered on satellites that had VERY regular charge/discharge cycles as they moved in and out of sunlight. For domestic applications with largely random charge/discharge it doesn't really exist but is used as a catch all for other problems such as overcharging (especially leaving cells to cook on tricklecharge) and overdischarging.

 

Always use a good quality charger that cuts off the charge as soon as the cell is fully charged and do not be tempted to squeeze the last drop out of the battery.

 

Always carry a spare:)

[TEAMYAKIMA]

4 minutes ago, melmerby said:

PP3 rechargeables used to be 8.4v.

I've had few over the years but now don't have any kit that uses that size.

 

Yes, very good point. I discovered this morning (after my original post) that my Maplin batteries were 8.4v and they have now been binned - they were in my original photo in post 1 but now removed.

[cliff park]

Surely one of the points about all rechargeables is that they are lower voltage than the equivalent batteries. Or at least they only come close for a very short time immediately after being charged. Anything that relies on the supply being close to nominal voltage is going to struggle. I used to use them in radio mics and finished up with loads of spares on charge and changing them out on a strict rota after every number. They weren't flat, just slightly low voltage.

[RobjUK]

A normal single-use PP3 has six "1.5V" cells, so starts out at around 9V but will steadily drop in voltage over its life and is at about 6V when genuinely flat, just before the voltage drops away rapidly.

 

Rechargeable PP3s typically use seven or eight NiCD / NiMH cells. That gives a nominal voltage of 8.4V or 9.6V, but with a real voltage range (just taken off charge when full, to empty) of almost 10.5V or 12V respectively, and again down to 1V per cell so 7V / 8V.

 

Eight cell ones are high enough voltage to be out of spec on things designed for normal PP3s.

 

Some things that use 7805 type voltage regulators will fail at around 7V, but either type should maintain that if in good condition.

 

 

"Memory effect" can cause nickel based cells to appear flat before they genuinely are, as the internal resistance increases if an attempt is made to discharge them below their normally-used range.

 

That can be eliminated by discharging them completely via a resistive load, which is completely safe when individual cells can be accessed but risky with an assembled battery, as any weak cells can end up reverse polarised..

 

If you want to try it with any batteries that are otherwise unusable, just connect a filament lamp across the battery and leave it for a few days.

Then recharge, allowing at least 40% over the theoretical minimum time to reach full on whatever charger you use, unless they get hot.

 

[ejstubbs]

2 hours ago, RobjUK said:

Rechargeable PP3s typically use seven or eight NiCD / NiMH cells.

 

Which is a problem in itself, because there is a strong likelihood of the individual cells within a battery charging and discharging at unequal rates.  This is particularly problematic when charging the battery because you can have one or more cells fully charged while others still need more charge, with the attendant risk of the fully charged cells ending up being over-charged (which is bad for them) while other cells are still not fully charged.  One duff cell and the whole battery is junk.

 

My experience with rechargeable PP3s has been universally poor.  Typically they don't last nearly as long from fully charged as an alkaline battery does, and their performance deteriorates over far fewer charge cycles than single cell rechargeables.  If you're intent on using rechargeable batteries for a device that needs 9V I'd be inclined to use rechargeable AAs or AAAs in an eight-cell box with a PP3 connector, such as this one (others are available) - but bearing in mind as well RobjUK's warnings about potential variability in the actual voltage supplied.

[dhjgreen]

If this is putting you off rechargeables, look at JCB primary batteries, typically £6 for 4, and last a whole lot longer than rechargeables between their charges.

 

I have totally given up on rechargeables and now stick with JCB primaries (they do rechargeables too but I have not tried them).  I get 4 AAs for £0.99 locally.

[WIMorrison]

7 hours ago, Crosland said:

Memory effect was discovered on satellites that had VERY regular charge/discharge cycles as they moved in and out of sunlight. For domestic applications with largely random charge/discharge it doesn't really exist but is used as a catch all for other problems such as overcharging (especially leaving cells to cook on tricklecharge) and overdischarging.

 

Always use a good quality charger that cuts off the charge as soon as the cell is fully charged and do not be tempted to squeeze the last drop out of the battery.

 

Always carry a spare:)

My laptops and phones must have been used in satellites then as they have all (and the old ones still do) suffered from the memory effect.
 

HP, Dell and IBM used to include instructions on how to minimise the memory effect on Ni-MH batteries when using them 

[Free At Last]

1 hour ago, ejstubbs said:

 

Which is a problem in itself, because there is a strong likelihood of the individual cells within a battery charging and discharging at unequal rates.  This is particularly problematic when charging the battery because you can have one or more cells fully charged while others still need more charge, with the attendant risk of the fully charged cells ending up being over-charged (which is bad for them) while other cells are still not fully charged.  One duff cell and the whole battery is junk.

In some cases I have found middle cells to become be reverse charged.

Edited November 10, 2019 by Free At Last

[Crosland]

44 minutes ago, WIMorrison said:

My laptops and phones must have been used in satellites then as they have all (and the old ones still do) suffered from the memory effect.

 

How do you know it was "memory effect"?

[WIMorrison]

Because that is how IBM, Dell and HP described it and applying the charging techniques they described on new batteries significantly reduced the effect

 

It may have first been described on satellites but it is an effect that has been well known in the mobile device market for many years. 

[ejstubbs]

 

5 hours ago, WIMorrison said:

5 hours ago, Crosland said:

6 hours ago, WIMorrison said:

HP, Dell and IBM used to include instructions on how to minimise the memory effect on Ni-MH batteries when using them

How do you know it was "memory effect"?

Because that is how IBM, Dell and HP described it and applying the charging techniques they described on new batteries significantly reduced the effect

 

True memory-effect is specific to sintered-plate nickel-cadmium cells, and is exceedingly difficult to reproduce, especially in lower ampere-hour cells. In one particular test program designed to induce the effect, none was found after more than 700 precisely-controlled charge/discharge cycles. In the program, spirally-wound one-ampere-hour cells were used. In a follow-up program, 20-ampere-hour aerospace-type cells were used on a similar test régime; memory effects were observed after a few hundred cycles.

 

https://en.wikipedia.org/wiki/Memory_effect#True_memory_effect

 

If you read the description of true memory effect linked above, it's pretty clear that nothing can be done to a battery before putting it in to normal service can prevent it.  I suspect that IBM, Dell and HP simply used a term that by then was in general use, albeit mistakenly.  (Note also that most/all laptops and phones these days use Li-Ion batteries or a variant thereof.)

 

Phenomena which are not true memory effects may also occur in battery types other than sintered-plate nickel-cadmium cells.

 

https://en.wikipedia.org/wiki/Memory_effect#Other_problems_perceived_as_memory_effect

 

Note particularly the description of "voltage depression due to long-term over-charging" and how it can cause modern electronic equipment which monitors the battery voltage to report, erroneously, that the battery is running low on charge.  Also note the "repair" section which refers to the deep discharge/recharge cycle remedy which was very commonly touted back in the 1990s when the not-the-true-memory-effect problem started to be noticed by consumers.

 

(Note also the caveat about remedy only being advisable for individual cells, for the reason that RobjUK gave above.  Bear in mind that most laptops would have used multiple-cell batteries, so the deep discharge/recharge cycle was almost as likely to kill the battery as fix it - which certainly matches my recollections of the dubious joys of NiCd and NiMh-powered laptops back in the day.)

Edited November 11, 2019 by ejstubbs

[WIMorrison]

It is interesting that articles promoting the description of memory effect proliferate across Wikipedia (that well known source of self promoting ‘truth’) all of which provide definitive origins for the term memory effect, yet all attribute the term to different battery types

 

What is consistent is that it exists and there are many peer reviewed and published papers that describe the term and its effects are, IMHO, a better source of truth than any Wikipedia article.

 

a google search will show several and I refer here to one which I recent and describes the effect as seen in L-Ion batteries also.

 

https://www.psi.ch/en/media/our-research/memory-effect-now-also-found-in-lithium-ion-batteries

Meantime I am personally comfortable using the term memory effect irrespective of it derivation and I am also comfortable using it with reference to all types of batteries as they all suffer effects to a greater or lesser extent.

 

[kevinlms]

15 hours ago, ejstubbs said:

 

Which is a problem in itself, because there is a strong likelihood of the individual cells within a battery charging and discharging at unequal rates.  This is particularly problematic when charging the battery because you can have one or more cells fully charged while others still need more charge, with the attendant risk of the fully charged cells ending up being over-charged (which is bad for them) while other cells are still not fully charged.  One duff cell and the whole battery is junk.

 

My experience with rechargeable PP3s has been universally poor.  Typically they don't last nearly as long from fully charged as an alkaline battery does, and their performance deteriorates over far fewer charge cycles than single cell rechargeables.  If you're intent on using rechargeable batteries for a device that needs 9V I'd be inclined to use rechargeable AAs or AAAs in an eight-cell box with a PP3 connector, such as this one (others are available) - but bearing in mind as well RobjUK's warnings about potential variability in the actual voltage supplied.

Agree about it all being about the weakest cell. AKA 'you are the weakest link'!

[sharris]

Has the self-discharge rate in NiMH batteries improved in recent years? 

 

They used to discharge themselves quite quickly, and when I was doing a bit of work with off-camera flashes 10-15 years ago I'd work on the principle that they (and the spares) would need recharging between each session, whether I'd actually used the flash or not. 

 

[RobjUK]

34 minutes ago, sharris said:

Has the self-discharge rate in NiMH batteries improved in recent years? 

Yes, drastically so.

 

The Eneloop and later Duracell "pre-charged" NiMH cells have incredibly low self discharge and the overall functional life for intermittent use without capacity loss is vastly greater than older types.

 

Whether you can get PP3 style with that type of cell construction is a different matter, but for AA and suchlike they are fantastic things.

 

[wasdavetheroad]

20 hours ago, RobjUK said:

Yes, drastically so.

 

The Eneloop and later Duracell "pre-charged" NiMH cells have incredibly low self discharge and the overall functional life for intermittent use without capacity loss is vastly greater than older types.

 

Whether you can get PP3 style with that type of cell construction is a different matter, but for AA and suchlike they are fantastic things.

 

I have used the latest low discharge NiMH cells to power some radio control locos. I found 4 x AAA cells gave about 4.8V before boosting the voltage and the capacity was about equivalent to a 700mAh lipo battery. With multiple locos the problem was the charger could only charge 4 batteries at a time but with lipos I can charge up to 10 single cells.

 

For the OP, what make radio throttles are you using? I am surprised that they should demand at least 8.5 V, plus is their power requirement in milliamps? A 9v rechargeable probably has less than 200 mAh capacity.

 

Thinks - can you fit a little 12V voltage booster in the casing? with some attention to the on/off switch because the regulator itself will draw a small amount of power. I have 2 radio control throttles which I converted to use 2 x AAA rechargeable cells with a voltage regulator to give the 3.3V the device needed.

[RobjUK]

9 minutes ago, wasdavetheroad said:

For the OP, what make radio throttles are you using? I am surprised that they should demand at least 8.5 V, plus is their power requirement in milliamps? A 9v rechargeable probably has less than 200 mAh capacity.

 

Agreed, it's bad design practice to not allow for the full charge-discharge voltage range of whatever battery it is supposed to use!

 

As the thing can apparently handle 12V or more from a fully charged 8 cell NiMH PP3, I was thinking that three lithium cells would be a better power source.

 

They would give a voltage range of 12.6 fully charged to still over 9V end-of-life.

 

You can get tiny ones for small drones, and multi-cell chargers - make a harness to connect three in series in the controller, but charge them all separately to avoid balance problems, and you should get a good life out of them.

 

eg. Three of these will fit in the space of a PP3, giving 240mAH capacity at ~10V:

https://www.ebay.co.uk/itm/3-7V-240mAh-481540-Li-Polymer-Rechargeable-Cell-Li-ion-LiPo-Battery-for-GPS-MP3/192607481393?hash=item2cd84cee31:g:ncQAAOSwrVRbVv~g

 

And a charger such as this will charge six cells at once:

https://www.ebay.co.uk/itm/A100-Multi-Port-Lipo-Battery-Charger-1S-3-7V-LOSI-Charge-Port-for-RC-Boat-Car/273844696735?hash=item3fc26a769f:g:r0cAAOSwE21c2cHA

 

You just need to make up the plug & socket connections.

 

[wasdavetheroad]

That 240mAh battery appears to have circuitry attached, maybe to prevent discharge below 3V. If it does and you can fit 3 in the throttle that should work.

 

I use UM single cell lipos for my radio controlled locos and one of my chargers works just like you suggest. My charger can handle two x 2S batteries independently and I made up two harnesses so I can charge 4 batteries. Your 3S harness should work too.

 

I guess the charger you are looking at has the 6 1S batteries connected in parallel so they behave as one larger battery for charging.

 

lipo batteries connected in parallel will auto balance but be careful the batteries voltages are not too different as current flow can be high.

[WIMorrison]

What is the name of the layout being shown at Warley? Will be nice to see it ‘in the flesh’  after reading so much about it

[WIMorrison]

What is the name of the layout being shown at Warley? Will be nice to see it ‘in the flesh’  after reading so much about it

[steve W]

On 12/11/2019 at 09:30, wasdavetheroad said:

....For the OP, what make radio throttles are you using? .......

 

I note he hasn't replied to this one, probably busy getting Beijiao (Chinese H0) ready. The layout uses Digitrax for the DCC so assume it is their hand controllers.

Steve W.