Repairing a lead acid battery charger

[Pandora]

I have an old sealed lead acid battery (Yuasa EN320-2RS) which has a
2V output and 320Ah capacity. Although it was never used much, I guess
it is about seven years old so is probably long gone and I intend to
buy an identical replacement.

I also have a lead acid battery charger which I tried on the
aforementioned battery without success. The charger is a
2/4/6/8/10/12V multi-range 1A float battery charger, which I bought a
few years ago from RS Components (part 129-684) http://tinyurl.com/2gfm5z
I was hoping to use the charger on the replacement battery some time
in the future.

Without a battery, I'm not sure how to test whether or not the charger
is working properly. The green "charged" LED lights up when the 2V or
4V range is selected, even though there is nothing across the output
terminals. Measuring the o/c d.c. voltage and s/c current across the
output terminals gives readings of a few hundred millivolts and
microamps.

I looked inside the charger and there is no sign of overheating
anywhere.

At the a.c. power supply input, there is a step-down mains transformer
and some large electrolytics and several rectifier diodes. On the
p.c.b., there is one LM339N quad comparator (which has a voltage of
7.6V between its supply pins 3 and 11). A TIP3055 power transistor on
a large heatsink is also present and a few small signal transistors.
Other than that I can only see resistors and a few small signal diodes
and zeners.

Please can anyone suggest a few simple tests that I can carry out to
verify whether or not the charger is working properly? What can I put
across the charger's output terminals to simulate a battery?

Thanks folks.

 

[Steve Walker]

I also have a lead acid battery charger which I tried on the
aforementioned battery without success. The charger is a
2/4/6/8/10/12V multi-range 1A float battery charger,

Please can anyone suggest a few simple tests that I can carry out to
verify whether or not the charger is working properly? What can I put
across the charger's output terminals to simulate a battery?

auto light bulb is easiest - you can calculate the loads and see whether
it's working

 

[[email protected]]

I also have a lead acid battery charger which I tried on the
aforementioned battery without success. The charger is a
2/4/6/8/10/12V multi-range 1A float battery charger, which I bought a
few years ago from RS Components (part 129-684) http://tinyurl.com/2gfm5z
I was hoping to use the charger on the replacement battery some time
in the future.

terminals. Measuring the o/c d.c. voltage and s/c current across the
output terminals gives readings of a few hundred millivolts and
microamps.

At the a.c. power supply input, there is a step-down mains transformer
and some large electrolytics and several rectifier diodes. On the
p.c.b., there is one LM339N quad comparator (which has a voltage of
7.6V between its supply pins 3 and 11). A TIP3055 power transistor on
a large heatsink is also present and a few small signal transistors.
Other than that I can only see resistors and a few small signal diodes
and zeners.

Sounds like a simple regulator.

Please can anyone suggest a few simple tests that I can carry out to
verify whether or not the charger is working properly?

sounds like you have

What can I put
across the charger's output terminals to simulate a battery?

no need, if it is just a Vreg.


NT

 

[Fred Bloggs]

I have an old sealed lead acid battery (Yuasa EN320-2RS) which has a
2V output and 320Ah capacity. Although it was never used much, I guess
it is about seven years old so is probably long gone and I intend to
buy an identical replacement.

I also have a lead acid battery charger which I tried on the
aforementioned battery without success. The charger is a
2/4/6/8/10/12V multi-range 1A float battery charger, which I bought a
few years ago from RS Components (part 129-684) http://tinyurl.com/2gfm5z
I was hoping to use the charger on the replacement battery some time
in the future.

Without a battery, I'm not sure how to test whether or not the charger
is working properly. The green "charged" LED lights up when the 2V or
4V range is selected, even though there is nothing across the output
terminals. Measuring the o/c d.c. voltage and s/c current across the
output terminals gives readings of a few hundred millivolts and
microamps.

I looked inside the charger and there is no sign of overheating
anywhere.

At the a.c. power supply input, there is a step-down mains transformer
and some large electrolytics and several rectifier diodes. On the
p.c.b., there is one LM339N quad comparator (which has a voltage of
7.6V between its supply pins 3 and 11). A TIP3055 power transistor on
a large heatsink is also present and a few small signal transistors.
Other than that I can only see resistors and a few small signal diodes
and zeners.

Please can anyone suggest a few simple tests that I can carry out to
verify whether or not the charger is working properly? What can I put
across the charger's output terminals to simulate a battery?

Thanks folks.

If it says it is a 1A charger then a 1 Ohm 5W resistor should cause it
to click. The charger may turn off on undervoltage thinking you have a
shorted cell. In that case put 2x 1 ohms in parallel and then put that
combo in series with the 1 Ohm for 1.5 Ohm total, it should start
charging that. Clip your VOM across the total load, plug the charger in,
and be ready to unplug if the voltage is much greater than 1.5V.

 

[[email protected]]

I also have a lead acid battery charger which I tried on the
aforementioned battery without success. The charger is a
2/4/6/8/10/12V multi-range 1A float battery charger, which I bought a
few years ago from RS Components (part 129-684) http://tinyurl.com/2gfm5z
I was hoping to use the charger on the replacement battery some time
in the future.

A batt charger is a good thing for regular use, but as a one off its
not needed. A psu and light bulb will do for a one off.

C/20 ie 16A, your 1A charger would take around 400 hours to chanrge a
320Ah cell.


NT

 

[Fred Bloggs]

I have an old sealed lead acid battery (Yuasa EN320-2RS) which has a
2V output and 320Ah capacity. Although it was never used much, I guess
it is about seven years old so is probably long gone and I intend to
buy an identical replacement.

Yikes- that's a $500 battery...

 

[Fred Bloggs]

A batt charger is a good thing for regular use, but as a one off its
not needed. A psu and light bulb will do for a one off.

Nice...nice way to convert a 65W job into 8KW that is.

 

[Dave Plowman (News)]

Please can anyone suggest a few simple tests that I can carry out to
verify whether or not the charger is working properly? What can I put
across the charger's output terminals to simulate a battery?

A car bulb? 12 volt 5 watt should be fine.

 

[ehsjr]

I have an old sealed lead acid battery (Yuasa EN320-2RS) which has a
2V output and 320Ah capacity. Although it was never used much, I guess
it is about seven years old so is probably long gone and I intend to
buy an identical replacement.

According to the datasheet for that battery, 7 years
at 25 degrees C is just about right for the life
expectancy on float charge.
http://www.yuasa-battery.co.uk/industrial/downloads.html

I get the idea that your battery was not on float charge -
is that correct? If the battery has not been charged for
the 7 year period, it's dead, and not retrievable.

I also have a lead acid battery charger which I tried on the
aforementioned battery without success. The charger is a
2/4/6/8/10/12V multi-range 1A float battery charger, which I bought a
few years ago from RS Components (part 129-684) http://tinyurl.com/2gfm5z
I was hoping to use the charger on the replacement battery some time
in the future.

That's a pretty expensive battery, and the charger you have
is really undersized for it, at one amp. Do you really need
that much battery? For a battery that expensive it would be
a good idea to use a charger that suits the intended use.
Your 1 amp charger would give you a charge rate of 1/320 which
is too low, even for a reasonable float charge.

Without a battery, I'm not sure how to test whether or not the charger
is working properly. The green "charged" LED lights up when the 2V or
4V range is selected, even though there is nothing across the output
terminals. Measuring the o/c d.c. voltage and s/c current across the
output terminals gives readings of a few hundred millivolts and
microamps.

Try putting a 10 ohm power resistor across the output
with the charger set to 2 volts, and measure the voltage
across the resistor. Output should be about 2.2 volts.

I looked inside the charger and there is no sign of overheating
anywhere.

At the a.c. power supply input, there is a step-down mains transformer
and some large electrolytics and several rectifier diodes. On the
p.c.b., there is one LM339N quad comparator (which has a voltage of
7.6V between its supply pins 3 and 11). A TIP3055 power transistor on
a large heatsink is also present and a few small signal transistors.
Other than that I can only see resistors and a few small signal diodes
and zeners.

Please can anyone suggest a few simple tests that I can carry out to
verify whether or not the charger is working properly? What can I put
across the charger's output terminals to simulate a battery?

You can use NiCds. Your charger will not charge them *properly*,
but it will charge them. For example, if you put two NiCd
cells in series and discharge them to 1 volt per cell, then put
them on your charger, it should charge them to 1.1 volts each.

Ed

 

[Colin Horsley]

I have an old sealed lead acid battery (Yuasa EN320-2RS) which has a
2V output and 320Ah capacity. Although it was never used much, I guess
it is about seven years old so is probably long gone and I intend to
buy an identical replacement.

I also have a lead acid battery charger which I tried on the
aforementioned battery without success. The charger is a
2/4/6/8/10/12V multi-range 1A float battery charger, which I bought a
few years ago from RS Components (part 129-684) http://tinyurl.com/2gfm5z
I was hoping to use the charger on the replacement battery some time
in the future.

Your link does not work.
Some smart battery chargers will NOT work unless there is a minimum voltage on
the battery available.
eg 12V battery must have at least 10V on it.
You can not test the charger like it is a normal Power Supply.

Colin

 

[Spehro Pefhany]

Yikes- that's a $500 battery...

I was just looking at some $500 batteries, and they are primary
cells.. amazing what the military will buy.



Best regards,
Spehro Pefhany

 

[[email protected]]

Nice...nice way to convert a 65W job into 8KW that is.

makes it around 100w in my rough calc, how do you get 8kW?


NT

 

[[email protected]]

Your link does not work.
Some smart battery chargers will NOT work unless there is a minimum voltage on
the battery available.
eg 12V battery must have at least 10V on it.
You can not test the charger like it is a normal Power Supply.

Colin

Do you reckon a smart charger can be made from those components?


NT

 

[The Natural Philosopher]

I was just looking at some $500 batteries, and they are primary
cells.. amazing what the military will buy.

Now look at the cost of a single armor piercing shell..

 

[Arfa Daily]

Do you reckon a smart charger can be made from those components?


NT

Given that he said in his original post that there was a '339 quad
comparator in it, then yes, certainly one that's 'smart' enough to know
whether it has a discharged battery on the end of it. This is along the
lines that I have been thinking all through this thread. I used to see a lot
of camcorder battery chargers claiming to be dead, when it was actually the
battery that they were trying to charge that had been left in the camera
since last year's vacation, and had got so flat that the charger would not
'start up' on it. A quick non current limited 'blast charge' from a 12v
supply would normally get the terminal voltage up to 6v or so, which would
be enough for the charger to 'see' the battery, and get on with charging it
as normal. So, in order to test this particular charger, it may be necessary
to put a rechargeable battery of some description - that's not totally
flat - across its output, and then measure the charge current to see if it
is developing some ...

Arfa

 

[Chris Jones]

Nice...nice way to convert a 65W job into 8KW that is.

If you start with a 3.3V ATX power supply (or half a dozen of them - out of
a dumpster, if cost is a problem), then you don't have to drop much
voltage. A light bulb would present too much resistance so some other kind
of resistor would be needed - perhaps some iron fencing wire on a suitable
heat-proof support- or a linear voltage regulator if this is to be used
repeatedly.

Chris

 

[Chris Jones]

I have an old sealed lead acid battery (Yuasa EN320-2RS) which has a
2V output and 320Ah capacity. Although it was never used much, I guess
it is about seven years old so is probably long gone and I intend to
buy an identical replacement.

I also have a lead acid battery charger which I tried on the
aforementioned battery without success. The charger is a
2/4/6/8/10/12V multi-range 1A float battery charger, which I bought a
few years ago from RS Components (part 129-684) http://tinyurl.com/2gfm5z
I was hoping to use the charger on the replacement battery some time
in the future.

Without a battery, I'm not sure how to test whether or not the charger
is working properly. The green "charged" LED lights up when the 2V or
4V range is selected, even though there is nothing across the output
terminals. Measuring the o/c d.c. voltage and s/c current across the
output terminals gives readings of a few hundred millivolts and
microamps.

I looked inside the charger and there is no sign of overheating
anywhere.

At the a.c. power supply input, there is a step-down mains transformer
and some large electrolytics and several rectifier diodes. On the
p.c.b., there is one LM339N quad comparator (which has a voltage of
7.6V between its supply pins 3 and 11). A TIP3055 power transistor on
a large heatsink is also present and a few small signal transistors.
Other than that I can only see resistors and a few small signal diodes
and zeners.

Please can anyone suggest a few simple tests that I can carry out to
verify whether or not the charger is working properly? What can I put
across the charger's output terminals to simulate a battery?

Thanks folks.

With a battery of such value, it may be worth investigating whether it can
be resuscitated. Depending on how it was stored, it may still be usable,
at least for some applications. If you can access "homepower" magazine
(used to be freely available on the net, not sure now), there were some
articles in there about reviving severely abused batteries, using chemicals
and various other techniques.

Chris

 

[Pandora]

I get the idea that yourbatterywas not on float charge -
is that correct? If thebatteryhas not been charged for
the 7 year period, it's dead, and not retrievable.

No, you're right, it hasn't been on float charge. During its life, the
battery was used on 15-20 occasions for periods of about 10mins only.

I tried to charge it with the 1A charger but, as someone has pointed
out, the charger had to be left on for long periods to make an
impression on the battery voltage.

The open voltage of the old battery is now at 1.1V. It's a sealed lead
acid type so I can't do anything chemically to it.

Do I have to buy a high capacity float charger if I want to keep the
replacement battery alive?

 

[[email protected]]

Fred Bloggs wrote:

If you start with a 3.3V ATX power supply (or half a dozen of them - out of
a dumpster, if cost is a problem), then you don't have to drop much
voltage. A light bulb would present too much resistance so some other kind
of resistor would be needed - perhaps some iron fencing wire on a suitable
heat-proof support- or a linear voltage regulator if this is to be used
repeatedly.

Chris

Start with a 6v bulb, filament bulbs have an 8:1 resistance ratio
between hot & cold, it runs far below rated power


NT

 

[[email protected]]

No, you're right, it hasn't been on float charge. During its life, the
battery was used on 15-20 occasions for periods of about 10mins only.

I tried to charge it with the 1A charger but, as someone has pointed
out, the charger had to be left on for long periods to make an
impression on the battery voltage.

The open voltage of the old battery is now at 1.1V. It's a sealed lead
acid type so I can't do anything chemically to it.

Do I have to buy a high capacity float charger if I want to keep the
replacement battery alive?

Since its been in use it may well be serviceable or repairable.

There are 3 ways to desulphate it:
1. Charge it from the mains - via a load of course! and rectifier
2. Charge it with high i inductive pulses
3. unseal it & add chemical tablet

Given the cost of the thing I'd try to charge it and desulphate it
before condemning it.

The final option is to rebuild it, which might even be worth it for
£500.


NT