In article <tj36jq$16iiv$1@dont-email.me>, David Woolley
<david@ex.djwhome.demon.invalid> wrote:
> On 22/10/2022 15:20, Jim Lesurf wrote:
> > Even better would be one that charges sets in series via a lead. That
> > way I could keep them in their battery holders. But I guess no-one
> > caters for that. Too DIY!

> You would be limited to C/10 charge rates, and probably to NiCd
> chemistry, as higher rates require monitoring individual cells, and I
> have a feeling that NiMH is not so tolerant of overcharging at C/10, and
> really needs positive end of charge detection.

> I'm not sure how PP3 chargers handle end of charge, although they may
> rely on close matching of the cells or on good thermal contact between
> the (dV/dt is based on the effect of temperature rises).

How does the system in electric cars deal with it, I wonder? presumably
they have *lots* of cells in series as well as parallel.

Similarly, rechargable 'radios' etc must have to deal with this.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics https://www.st-andrews.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
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Audio Misc http://www.audiomisc.co.uk/index.html

On 23/10/2022 15:15, Jim Lesurf wrote:
> How does the system in electric cars deal with it, I wonder? presumably
> they have*lots* of cells in series as well as parallel.

They don't use NiMH chemistry, so don't use dV/dt endpoint detection,
although I think they have to monitor every cell.

E.g. see
<https://circuitdigest.com/electronic-circuits/designing-12v-li-ion-battery-pack-with-protection-circuit>
or section 5 in <https://sound-au.com/articles/lithium-charging.htm>.

On Thu, 20 Oct 2022 11:58:51 +0100
nothanks@aolbin.com wrote:

> The recent discussion about emergency transmissions got me thinking
> about being a little more prepared than now ... what recommendations do
> people have for reasonably-priced non-DAB battery/mains receivers?

https://www.amazon.co.uk/long-wave-radio/s?k=long+wave+radio

--
Mint 20.3, kernel 5.4.0-124-generic, Cinnamon 5.2.7
running on an AMD Phenom II X4 Black edition processor with 16GB of DRAM.

On Mon 24/10/2022 15:43, pinnerite wrote:
> On Thu, 20 Oct 2022 11:58:51 +0100
> nothanks@aolbin.com wrote:
>
>> The recent discussion about emergency transmissions got me thinking
>> about being a little more prepared than now ... what recommendations do
>> people have for reasonably-priced non-DAB battery/mains receivers?
>
>
> https://www.amazon.co.uk/long-wave-radio/s?k=long+wave+radio
>
>

If any reader is worried about a mushroom cloud, the answer is to
find/get a valve radio as the EMP produce by the big bang doesn't affect
them, only semiconductors.

I've got an old Bush AC11 in the loft that I remember as our general
wireless when I was about 4 or 5 (and I'm now well over the old pension
age!) Live chassis and may need some new smoothing caps but I bet it
will work!

On 23/10/2022 11:55, David Woolley wrote:
> On 22/10/2022 15:20, Jim Lesurf wrote:
>> Even better would be one that charges sets in series via a lead. That
>> way I
>> could keep them in their battery holders. But I guess no-one caters for
>> that. Too DIY!
>
> You would be limited to C/10 charge rates, and probably to NiCd
> chemistry, as higher rates require monitoring individual cells, and I
> have a feeling that NiMH is not so tolerant of overcharging at C/10, and
> really needs positive end of charge detection.

NiMH cell data sheets typically recommend maximum continuous trickle
charge should be C/20, C/40 or even lower for some smaller types.

> I'm not sure how PP3 chargers handle end of charge, although they  may
> rely on close matching of the cells or on good thermal contact between
> the (dV/dt is based on the effect of temperature rises).

I've found that in practise NIMH PP3 often die after only a few charge
cycles unless you charge them at very low rates. I use around C/100.

--
Brian Gregory (in England).

On Mon, 24 Oct 2022 16:19:25 +0100, Woody <harrogate3@ntlworld.com>
wrote:

>On Mon 24/10/2022 15:43, pinnerite wrote:
>> On Thu, 20 Oct 2022 11:58:51 +0100
>> nothanks@aolbin.com wrote:
>>
>>> The recent discussion about emergency transmissions got me thinking
>>> about being a little more prepared than now ... what recommendations do
>>> people have for reasonably-priced non-DAB battery/mains receivers?
>>
>>
>> https://www.amazon.co.uk/long-wave-radio/s?k=long+wave+radio
>>
>>
>
>If any reader is worried about a mushroom cloud, the answer is to
>find/get a valve radio as the EMP produce by the big bang doesn't affect
>them, only semiconductors.
>
>I've got an old Bush AC11 in the loft that I remember as our general
>wireless when I was about 4 or 5 (and I'm now well over the old pension
>age!) Live chassis and may need some new smoothing caps but I bet it
>will work!

Probably not for very long from batteries though.

Rod.

On 25/10/2022 06:56, Roderick Stewart wrote:
> On Mon, 24 Oct 2022 16:19:25 +0100, Woody <harrogate3@ntlworld.com>
> wrote:

>> If any reader is worried about a mushroom cloud, the answer is to
>> find/get a valve radio as the EMP produce by the big bang doesn't affect
>> them, only semiconductors.
>>
>> I've got an old Bush AC11 in the loft that I remember as our general
>> wireless when I was about 4 or 5 (and I'm now well over the old pension
>> age!) Live chassis and may need some new smoothing caps but I bet it
>> will work!
>
> Probably not for very long from batteries though.

You need a valve portable using D series valves. And loads of AA
batteries to make up the 90V HT.

--
Max Demian

In article <jrnt7qFu7ppU1@mid.individual.net>, Brian Gregory
<void-invalid-dead-dontuse@email.invalid> wrote:
> On 23/10/2022 11:55, David Woolley wrote:
> > On 22/10/2022 15:20, Jim Lesurf wrote:
> >> Even better would be one that charges sets in series via a lead. That
> >> way I could keep them in their battery holders. But I guess no-one
> >> caters for that. Too DIY!
> >
> > You would be limited to C/10 charge rates, and probably to NiCd
> > chemistry, as higher rates require monitoring individual cells, and I
> > have a feeling that NiMH is not so tolerant of overcharging at C/10,
> > and really needs positive end of charge detection.

> NiMH cell data sheets typically recommend maximum continuous trickle
> charge should be C/20, C/40 or even lower for some smaller types.

So it is 'safe' to constant current recharge NiMH provided the current is
very low?

Some years ago my practice with recharging NiCads was to use a pulsed
charge as experience with electroforming showed that prevents crystal
'spikes' forming and gives a uniform structure to the deposit. However
since then I've just used low constant current as it seems fine.

The NiMH cells I have are mostly AA. I'll see if I can find some
plots/tables of how the voltage changes with charge level and where it
should be stopped. Then experiment with some old examples.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics https://www.st-andrews.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
biog http://jcgl.orpheusweb.co.uk/history/ups_and_downs.html
Audio Misc http://www.audiomisc.co.uk/index.html

On 25/10/2022 10:05, Jim Lesurf wrote:
> In article <jrnt7qFu7ppU1@mid.individual.net>, Brian Gregory
> <void-invalid-dead-dontuse@email.invalid> wrote:
>> On 23/10/2022 11:55, David Woolley wrote:
>>> On 22/10/2022 15:20, Jim Lesurf wrote:
>>>> Even better would be one that charges sets in series via a lead. That
>>>> way I could keep them in their battery holders. But I guess no-one
>>>> caters for that. Too DIY!
>>>
>>> You would be limited to C/10 charge rates, and probably to NiCd
>>> chemistry, as higher rates require monitoring individual cells, and I
>>> have a feeling that NiMH is not so tolerant of overcharging at C/10,
>>> and really needs positive end of charge detection.
>
>> NiMH cell data sheets typically recommend maximum continuous trickle
>> charge should be C/20, C/40 or even lower for some smaller types.
>
> So it is 'safe' to constant current recharge NiMH provided the current is
> very low?
>
> Some years ago my practice with recharging NiCads was to use a pulsed
> charge as experience with electroforming showed that prevents crystal
> 'spikes' forming and gives a uniform structure to the deposit. However
> since then I've just used low constant current as it seems fine.
>
> The NiMH cells I have are mostly AA. I'll see if I can find some
> plots/tables of how the voltage changes with charge level and where it
> should be stopped. Then experiment with some old examples.

I've been using trickle chargers for AA and AAA NiMH cells for many
years without any problem. The batteries sometimes get a bit warm, but
they appear to be lasting a long time. I don't know what currents they
supply, but 2100 mAH AAs are said to take 16 hours and 1000 mAH AAAs 28
hours. The chargers don't tell you when the cells are charged though.
Cells are charged in pairs and, I think, you can charge different pairs
at a time. They also charge PP3s but I don't have any.

--
Max Demian

On 26/10/2022 14:00, Max Demian wrote:
> I've been using trickle chargers for AA and AAA NiMH cells for many
> years without any problem. The batteries sometimes get a bit warm, but
> they appear to be lasting a long time. I don't know what currents they
> supply, but 2100 mAH AAs are said to take 16 hours and 1000 mAH AAAs 28
> hours. The chargers don't tell you when the cells are charged though.
> Cells are charged in pairs and, I think, you can charge different pairs
> at a time. They also charge PP3s but I don't have any.

I try avoid continuously charging so things like my cordless phones get
taken off charge overnight or when I go out. It is as much about fire
risk as battery life.