On Fri, 2 Feb 2018 05:42:39 -0800 (PST), wrote:

On Thursday, 1 February 2018 22:58:47 UTC, Archibald Tarquin Blenkinsopp wrote:
On Thu, 1 Feb 2018 14:21:39 -0800 (PST), tabbypurr wrote:
On Thursday, 1 February 2018 21:52:28 UTC, Archibald Tarquin Blenkinsopp wrote:
On Thu, 1 Feb 2018 13:28:38 -0800 (PST), tabbypurr wrote:
On Thursday, 1 February 2018 21:05:05 UTC, Archibald Tarquin Blenkinsopp wrote:
On Thu, 1 Feb 2018 12:45:45 -0800 (PST), tabbypurr wrote:
On Thursday, 1 February 2018 20:12:30 UTC, Archibald Tarquin Blenkinsopp wrote:
On Thu, 01 Feb 2018 08:33:20 GMT, Harry Bloomfield
wrote:
ss used his keyboard to write :

Charger for a mobility scooter. One charger not working, I opened it up and
as per image below it looks like some kind of fuse has blown.
Text on the board looks like 3A/2500AR.

Can anyone confirm and identify what I would need to replace.
I have limitations on electronic stuff but could probably manage to solder
this part if I can find a replacement.

https://imgur.com/a/QTZ0e

From what I can see in the image, it looks like a wire ended fuse which
has exploded. That suggests a serious fault.

Also from what I can see, it looks like a fairly crude charger.
transformer, bridge, then possibly a relay switching the charge current
on and off, driven by a basic voltage across the battery sensing
circuit.

Cobblers!

One does not need an NTC thermistor in a "crude" charger.

I would have serious doubts that terminal Voltage plays a big part in
the control feedback. The control is via current monitoring so a more
stable source of reference would be needed.

There would be no piddly little rectifiers in a "crude" charger
either, they would be after the tranny and would need to handle a few
Amps, assuming the charge process was to take less than 24 hours.

Incidentally an exploded fuse is a fairly minor fault from a
diagnostics perspective. Generally a few seconds with a DMM will find
the problem.

As to what happens when the little plastic thing with legs = 3 is
found to be S/C, is a completely different story.

AB

I'm puzzled by your comments. What sort of lead acid charger is not voltage regulated?


NT

The statement was "terminal Voltage".

Direct Voltage regulation isn't really an option. Have you tried
charging a 12Volt lead acid battery from 12Volts?

Have you tried charging from 14Volts?


Can you suggest a few drawbacks to using a supply regulated to give
either Voltage, or even one in between those values?

The internal resistance of a battery is dependent on a number of
things, age, temperature and the amount of charge stored, therefore
the terminal Voltage of the battery isn't the best starting point for
control.

AB

I can only conclude you don't understand lead acid charging.


NT
What aspect?

I must admit the chemistry is not something that I have dealt with for
some considerable number of years.

I am however keen to learn, just how would an expert such as your good
self approach charger design?

AB

Lead acids are charged with voltage regulated chargers. There are 1 stage or better chargers have more stages. The charger must of course have overcurrent limit too, but it is the battery itself that limits i much of the time.

As opposed to NiCd & NiMH which require current controlled chargers.


NT
That's deep!

So you have Voltage regulation?

Why do you need an overcurrent limit? You already have Voltage
regulation, so how can the current become excessive?


When you say the battery limits the current "much of the time", just
how much of the time?

At what point does the battery stop limiting the current and why
doesn't your Voltage regulation just reduce the Voltage to the point
where you are not reliant on the environmental variables of the
surroundings to influence current consumption?

AB

the keywords you're looking for a lead acid battery charging


NT

If it makes it easier for you.......

When you say the lead acid battery battery limits the current "much of
the time", just
how much of the time?


At what point does the lead acid battery stop limiting the current
and why doesn't your Voltage regulation just reduce the Voltage to the
point where you are not reliant on the environmental variables of the
surroundings to influence current consumption?

I trust this helps?

AB