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Repairing a lead acid battery charger

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)
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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.

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

Reply to
Steve Walker

Sounds like a simple regulator.

sounds like you have

no need, if it is just a Vreg.

NT

Reply to
meow2222

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.

Reply to
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.

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

320Ah cell.

NT

Reply to
meow2222

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

Reply to
Fred Bloggs

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

Reply to
Fred Bloggs

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

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Reply to
Dave Plowman (News)

According to the datasheet for that battery, 7 years at 25 degrees C is just about right for the life expectancy on float charge.

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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.

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.

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.

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

Reply to
ehsjr

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

Reply to
Colin Horsley

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

Best regards, Spehro Pefhany

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Reply to
Spehro Pefhany

a

guess

to

Of course it is a primary cell - (sealed lead acid in this case)... A 6V battery consists of 3 primary cells in series, a 12V battery has

6 cells etc...

Ever since central battery telephone exchanges have existed the 48V battery has consisted of 24 'primary cells' in series. These days a 2V

2000Ah cell is common in exchanges.

Typical 'primary cells' used today

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Reply to
Ross Herbert

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

NT

Reply to
meow2222

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

NT

Reply to
meow2222

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

Reply to
The Natural Philosopher 

--
Sorry, but rechargeable cells aren\'t "primary".

http://en.wikipedia.org/wiki/Primary_cell
Reply to
John Fields

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

Reply to
Arfa Daily

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

Reply to
Chris Jones

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

Reply to
Chris Jones

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?

Reply to
Pandora

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