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Naitch Offline OP
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Many moons ago, I passed comment about corrosion I was getting on the battery terminals of Smiths Medical (Graseby) Syringe Drivers of the 3000 family. Replies suggest that the ambient humidity of the UK does this to batteries (!) Since then, I've STILL been getting corrosion, but I've since noticed that the corrosion is ALWAYS on the +ve terminal of a battery (Enersys Cyclon 2 Volt, 2.5AH D-cell). Has anybody else had similar problems? As well as drivers of the 3000 series family, I've just had one on an Omnifuse PCA pump.
I am of the opinion that the Enersys batteries have a quality problem.


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Originally Posted By: Naitch
Has anybody else had similar problems?

Yes. I've seen quite a lot of it. But usually on old Graseby's, which had often been out of regular use (ex-auction, and so forth).

Obviously some sort of chemical reaction is taking place, driven by the DC current being passed.

Electrolysis? Or even ... verdigris?

Where exactly is the corrosion being formed, and what does it look like (colour etc.)?

And ... how tight (and/or clean) are those connections? I have tried using a smidgen of Vaseline on the positive connections in the past.

Meanwhile, do you have any further clues? Are all 3000 series syringe pumps affected ... or just those from units renowned for "forgetting" to keep them nicely charged up? think

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We've not really seen this problem but you could try a bit of grease over the +ve conductor to keep the moisture out. Where are they stored? Check the RH & Temperature.

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Naitch Offline OP
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Responding in order...
1) The corrosion is IN and OVER all metalwork on the +ve terminal of the battery AND on the metalwork of the connector to it. On the connector, it's a pale beige colour, but I reckon that the brass colour of the socket has a lot to do with that. On the cell terminal, it's white with a hint of green. The corrosion is usually so bad, it breaks the circuit, so the unit doesn't get charged in this condition, despite being plugged into the mains.
2) It's difficult to tell how tight the connections are, as they're buried under the corrosion! The connections are usually difficult to seperate, but, again, that may be down to the corrosion.
3) To date, it's mostly been 3000 series pumps that's been affected - we have 3100, 3150, 3200, 3300, 3400 & 3500 devices. However, this morning, I had my first Omnifuse with this problem.
4) The affected pumps come from all parts of the hospital (Royal Infirmary of Edinburgh), but I have had a few from our Sick Kids hospital, so it's not confined to one particular area. If it was RH or temp, them there would be more occurences of this problem, I think. Our pumps are stored UNPLUGGED in adjoining storerooms to the wards, OR they are next to beds in the wards/theatres, plugged in to the mains.

As its always the +ve terminal, I subscribe to the ideas that it may be a quality issue with the batteries, i.e. a tiny acid leak, but that is merely a guess.


Remember I was asking (asking? Pleading, more like!) for an M400 Mellotron? Well.....

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Thanks for your full (and frank) reply!

I have also seen 3000 series pumps in condition 1). I have always assumed the root cause to be the use of dissimilar metals used at the battery lug and the "female spade" connector, with an anode being formed there at which corrosion builds up. But there again, I'm no Rocket Scientist! Ha, ha.

Another question (or two) if I may:-

1) How often do these pumps get opened up and looked at?
2) What made you open these pumps up ("not charging")?
3) How old are these pumps?
4) Is opening them up part of your regular PM procedure?

If not (at question 4) ... may I suggest that you include it in future. And, as has already been mentioned, add a little Vaseline to the connections. think

Frankly, I doubt there is any problem with the batteries themselves. They have always been a Quality Product (in my opinion).

* Perhaps it's time to either change all the batteries at the next PM (like every other component, they have a "life") - or start looking for some newer pumps!


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I have seen this happen on many types of equipment, even when the batteries are used in the upright position,but I have only seen it on batteries that are several years old. My guess is that after several years of charging/discharging, some hydrogen has built up in the cell. Eventually it reaches a pressure where it leaks out at the weakest point (round the positive terminal seal). As the gas escapes it carries small droplets of acid, that coat the terminal and connector.
Just a theory, no way of proving it!

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It's a nice theory, Tony. smile

To which I would add the possibility of excessive (over-) charging from a poorly designed charging circuit!

These are SLA batteries of special (that is, "thin plate") cells ... that are essentially non-vented. For more, see here.

As I say, I believe that "the answer" is extra vigilance during PM. smile

As an aside, surely we have all seen swollen, corroded primary cells - and "sulphation" at the positive terminal of car batteries? think

For what it's worth, here is my own Best Guess as to what is going on here:-

1) Graseby's get driven into the ground (on battery power)
2) Graseby's get get left in an un-charged state at the back of a cupboard somewhere
3) Someone remembers (or needs) the Graseby's and takes them out and plugs them in
4) Batteries - already in a stressed condition - get a hefty charge (and gets a bit hot)!
5) This cycle happens over and over (over some years)!
6) During repair, the biomed opens the Graseby's and notices the sorry state of the batteries!

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Originally Posted By: Geoff Hannis
To which I would add the possibility of excessive (over-) charging from a poorly designed charging circuit!

I've just taken a glance at some 3000 series circuits (yes, sad I know) ... and it seems that the battery charging arrangements differ across various models (3100 ... 3500).

I would say that a constant voltage approach is used (which is what the Cyclons like best).

I have also noticed RV1, which is adjusted to set the nominal 7.0 VDC level according to ambient temperatures. Does anyone ever touch this pot, I wonder? To be honest, looking at the data in the manual(s) it hardly makes a lot of difference (7.015 to 7.166 VDC).

But at those sort of voltage levels, I would suggest that the circuitry is intended to act as a Float (rather than Fast) Charger ... which means essentially that the pumps should be left on charge more or less continuously. smile

Does this stuff get mentioned on the training course(s) at Graseby? think

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@Naitch: a couple of final questions, if I may:-

1) Do all three cells tend to be affected in each case, or just one in each pump (the one furthest to the right - most positive, for example)?*

2) And ... have you found many pumps of similar age where the cells are all OK? think

And it would be of academic interest (at least) to know about the nominal 7.0 VDC level in each case (measured across a 68 ohm 1 Watt load, apparently). It would be nice to note the voltage with the problem battery sets in circuit as well. smile

* I'm wondering if "one bad cell" leads to over-charging of the good ones. These cells should always be changed as a set (rather than individually).


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Naitch Offline OP
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Originally Posted By: Geoff Hannis

Thanks for your full (and frank) reply!

I have also seen 3000 series pumps in condition 1). I have always assumed the root cause to be the use of dissimilar metals used at the battery lug and the "female spade" connector, with an anode being formed there at which corrosion builds up. But there again, I'm no Rocket Scientist! Ha, ha.

Another question (or two) if I may:-

1) How often do these pumps get opened up and looked at?

Probably every 2 years - we usually open them up ONLY when we're fault-finding.
Originally Posted By: Geoff Hannis
2) What made you open these pumps up ("not charging")?

Usually "Not working on Battery"

Originally Posted By: Geoff Hannis
3) How old are these pumps?

Varying ages - some 3100's date from before 1994, but the Omnifuse that had corrosion was about 18 months old.
Originally Posted By: Geoff Hannis
4) Is opening them up part of your regular PM procedure?
No. The only time we open up a unit is to fault-find. 3000 series pumps are on the way out here, so increased maintenance will be considered a waste of time by my superiors!


Remember I was asking (asking? Pleading, more like!) for an M400 Mellotron? Well.....

I'VE NOW GOT ONE!
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