Battery maintenance ( 50% boaty!!)

[pcatterall]

Just checking the batteries on my ( new to me) 3 year old van. The hand book assures me that the batteries will be checked as part of the annual service. On the transit there are two batteries, one seems to be for ancillary equipment and one mainly for starting, they are both under the drivers seat. There are individual caps for each cell and some are under a big metal security frame, 3 difficult bolts to undo and difficult then to remove the frame. There is then only access to the rear battery caps, to get at the front battery one would really have to remove both batteries.......... what a pain and I bet they have never been checked!!

So we come to the real reason for my post and I have had this question with my boat batteries.
Looking into the cells on my vehicle batteries I can see a sort of flat plate and there is a very small amount of liquid ( about 1 or 2 mm) above this plate, is this ok or do I need to top up a bit?
On the boat there seems to be a wafer visible and I guess I should be ensuring that this is also just covered? This is a mirror and torch job to see the plates and I guess I should invest in a bottle with a tube to aid top up?
It seems to be a bit hit and miss and I suppose that if I add too much water I will have the wrong SG of liquid?
Do we rely on guess work/eyeball or should we test the SG each time we top up?

 

[VicS]

Just checking the batteries on my ( new to me) 3 year old van. The hand book assures me that the batteries will be checked as part of the annual service. On the transit there are two batteries, one seems to be for ancillary equipment and one mainly for starting, they are both under the drivers seat. There are individual caps for each cell and some are under a big metal security frame, 3 difficult bolts to undo and difficult then to remove the frame. There is then only access to the rear battery caps, to get at the front battery one would really have to remove both batteries.......... what a pain and I bet they have never been checked!!

So we come to the real reason for my post and I have had this question with my boat batteries.
Looking into the cells on my vehicle batteries I can see a sort of flat plate and there is a very small amount of liquid ( about 1 or 2 mm) above this plate, is this ok or do I need to top up a bit?
On the boat there seems to be a wafer visible and I guess I should be ensuring that this is also just covered? This is a mirror and torch job to see the plates and I guess I should invest in a bottle with a tube to aid top up?
It seems to be a bit hit and miss and I suppose that if I add too much water I will have the wrong SG of liquid?
Do we rely on guess work/eyeball or should we test the SG each time we top up?

The electrolyte should cover the actual positive and negative plates.

Some batteries have a level marked on the outside.

If you check them with a hydrometer it makes sense to ensure that there is adequate electrolyte above the plates to be able to suck up a hydrometer full.

Remember added water is less dense and it takes a while to become mixed with the electrolyte and that until this occurs hydrometer readings are useless.

 

[nigelmercier]

Don't do what I did many years ago. I bought a bottle with an automatic spout, it had a protrusion that you rested on the plate, and the water glugged out until there was a water lock. I managed to punch through not one, but two cell plates.

 

[Hadenough]

Don't do what I did many years ago. I bought a bottle with an automatic spout, it had a protrusion that you rested on the plate, and the water glugged out until there was a water lock. I managed to punch through not one, but two cell plates.

Bin there done that! Those dispenser thingys looked like a good idea at the time eh!

 

[Pleiades]

Talking about eye balls, just be very careful there Skipper - battery acid in the eyeball would certainly smart a fair bit. The combination of electric current, explosive battery electrolyte gas and acid make for a potent cocktail so approach with caution. Approximately right is ok for electrolyte levels but approximately safe is not ok.

Robin
Pleiades of Birdham
MXWQ5

 

[William_H]

OP may have seen posts here about determining battery charge state by SG of electrolyte. Thus he assumes that electrolyte SG is critical. Actually SG is not really critical so it is Ok to add water to batteries. Fluid loss is mainly water in vapour so acid quantity stays the same. You will find that if you add too much water it may tend to splash out of vent holes so corroding structure nearby. I would however suggest that water in the batteries could go half way from the top of the cell dividers to the top of the cavity. Thus leaving a little more water than normal in case of wqater use.
It would be a good idea to check battery fluid level in all cels intiailly then fairly frequently until you can see if batteries are going to need water. Experience may show not so critical as little water used. Check the hard to see cells becuase someone may have just not checked them in it's previous life but once you have checked, you can use the accessible cells as an indication of the need to check the inaccessible ones. My 3 year old car has never had water added to the battery. good luck olewill
Heat can exaccerbate water usage. Not a problem in UK right now. Long runs where battery will be well charged may also cause water loss.