Hi James and Arby,
Thanks for this, though it makes me feel a bit silly!
I tend to credit myself with reasonable intelligence, but somehow my
left-handed mind could only visualise the full rectangle of the battery,
not the rectangles of each individual cell. Also, the starting battery
space in the boat is currently 'fore and aft' mounting, and there is a
tendency to follow that existing setup. At 64 yrs old, and never have
sailed yet, believe me, the angle of heel is not likely to be
intentionally severe!
I will look into those recombiners too. Makes good sense even if I use
humble grade batteries.
Appreciated,
John
2b. Re: Lead Acid Batteries, and boat heeling.
Posted by: "James Massey" jcmassey@netspace.net.au technikjames
Date: Fri Jun 10, 2011 5:33 am ((PDT))
At 09:03 PM 10/06/2011, John wrote:
>Hi All,
>
>Just wondered whether there are limits to the angle that a lead acid
>battery can be tipped to?
>If so, would extension tubes to the filler holes be possible?
G'day John
The limitation in reference to wet cell lead-acid is in keeping the
active material if the cells immersed in acid, and not letting the
acid out of the vents. It's not a problem with gel and AGM, since the
electrolyte is (relatively) immobilised, so on the subject of wet lead:
Problem: As the state of charge of the cells rises and falls, the
acid strength rises and falls with it. This has the effect of making
the electrolyte level rise and fall also. A fully discharged wet cell
has an acid level that is only just above the cell plate tops. As the
cell charges, there is more and more sulphur taken from the lead
sulphate into the acid, so the acid grows, ending up about 2/3 to 3/4
of the way up the cell 'top space' (varies, depending on the
particular battery design).
So to tip the cell over, you need to make sure that the discharged
level does not expose the plate active material, and the
almost-charged level does not reach the cell vent (otherwise it'll
push the electrolyte out of the vent as it completes charging).
So what is to be done?
In most batteries the cells are arranged to be across the width of
the battery case, so if the batteries are installed so that the long
direction of the cell is fore-and aft (usually means the long
direction of the battery will be across the hull), then the acid tilt
line is only across the cell in its' shortest dimension. This will
allow for angles of up to around 40 degrees each way without a
problem - but you'll have to confirm with your particular cells.
If you're going to need more tilt than that, best to use sealed
batteries.
Hope this helps
Regards
[Technik] James
2c. Re: Lead Acid Batteries, and boat heeling.
Posted by: "Arby bernt" arbybernt@yahoo.com arbybernt
Date: Fri Jun 10, 2011 7:34 am ((PDT))
You can also replace the vent caps with recombiners, which both extend
the distance to the "top" of the battery, and will vastly reduce
watering of the wet cells.
Arby
AMeP
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