Help! Berlingo battery replacements

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Flying John
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Postby Flying John » Tue Nov 03, 2009 10:00 pm

Why should it be made fresh. I expected a sealed container of distilled water to remain pure enough for use in the batterys. But if not please tell us why.
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John

NickJ
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Postby NickJ » Tue Nov 03, 2009 11:12 pm

Hi John

There is a scientific and a prosaic answer here! Also you hit the nail on the head with the sealed container bit.

The science revolves around the tendancy of water to absorb carbon dioxide (and other gases) from the air which affect the pH of the water and add ions, also most containers will tend to leach something into the water, even some plastics. So an opened container, such as we have after watering the berlingo, has a lot of air around it and will gradually become more acidic with time, until an equilibium is reached. This effect is small but may cause some potassium carbonate production in the cells with time. once carbonate ions are in the cells they cant be removed.

Also it is amazing what will grow in water, even de-ionised water, and if stored in a warm light place algae is not uncomon as these feed off the dissolved CO2, NOx and other traces, so again for the cleanest water fresh is best.

More prosaically fresh water reduces the risk of bits getting in your container!

The above effects are theoretical as I dont know how sensitive NiCads are to trace carbonate or other ion contamination, or from other contaminents.

But I would generally be wary of half used containers of water as they may be problematic. If sealed as you say and in an appropriate container (which is not gas permeable) stored cool and dark I doubt there would be any problems.

Bit long winded but hopefully gives a bit of background.

N

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Flying John
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Postby Flying John » Wed Nov 04, 2009 9:05 am

Fantastic reply Nick. Its good to understand the reasons for using fresh. I make mine in batches of 22litres and the plastic drum was from the first time I had to actually buy some. It is a sealed plastic drum, but I hope the suppliers who charge for it have taken the neccesary steps to make sure the container is suitable. I think the only improvement I could make is to keep it inside a black bag or sack to exclude light.

John

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ChrisB
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Postby ChrisB » Wed Nov 04, 2009 9:38 pm

NickJ wrote:The science revolves around the tendancy of water to absorb carbon dioxide (and other gases) from the air which affect the pH of the water and add ions, also most containers will tend to leach something into the water, even some plastics. So an opened container, such as we have after watering the berlingo, has a lot of air around it and will gradually become more acidic with time, until an equilibium is reached. This effect is small but may cause some potassium carbonate production in the cells with time. once carbonate ions are in the cells they cant be removed....................


Great reply there NickJ, and I presume this is another reason for leaving the fills lines full of water compared to fresh air if you where to run the lines dry hence the one way valves, and thus less chance of air getting into the the cells or at least sitting on top of the cells for long periods as only the vent is open to the atmosphere.

ChrisB
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NickJ
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Postby NickJ » Wed Nov 04, 2009 10:53 pm

Thanks guys

I agree Chris, It is likley that the cells are designed to limit the access of air but allow venting. The effect of unlimited air on strong sodium/potassium hydroxide solutions is seen on bottles of the solution in labs which develop a "crust" of carbonate on theit necks over time as they absorb CO2 from the air.

As I said before I dont know how much the absorbtion of CO2 affects the lifespan of these batteries overall but it is probably good to minimise any access of CO2 (and any other source of unwanted ions)



:)

tim.strutt
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Postby tim.strutt » Fri Nov 27, 2009 9:20 pm

Hi all, first time back on here for some time - thnx Tim for sorting out my profile, look what I've been misisng - Excellent topic and very useful posts - thank you.

re the need to keep air out of the system.

When watering I've noticed that if I'm not careful when adding water to the head tank on my watering kit, the act of pouring water in can cause air bubbles to be drawn down the tube to the packs !

I also tend to continue to water packs until I see a steady stream of water from the overflow, even if it means letting it run until no spurts are evident.

One thing I've noticed a couple of times on one of our vans is a "slow" fill/drain for "INTM D"? When I say slow, it can appear to stop taking water for several minutes, and then appear to restart, and the flow from the vent is always spluttering. I've read elsewhere of two people experiencing blown cells caused by incorrect watering of a pack at the rear of Berlingos that they put down to a trapped pipe inside the Tray.... I wonder.

TimS

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Postby ChrisB » Fri Nov 27, 2009 9:53 pm

Good point Tim, watch out for those bubbles :wink:

Must admit I've never experienced any stop start re-filling, although the middle and rears do take a while to come through but then they are pretty long runs and theres a lot of pipe work in the middle crate.

ChrisB
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