pessimist
Well-Known Member
Just bought a sealed lead acid as a temporary house battery - don't ask. It doesn't appear to have any removable plugs nor did it come with any instructions to remove any. Is this normal now or am I missing something ?
Sealed lead acid battery question
- Thread starter pessimist
- Start date
Sailingsaves
Well-Known Member
That's normal.
It will have some venting apertures somewhere (can be tiny) and some 'sealed' batteries are pretty well sealed for life and some can be opened for inspection if really necessary, but if one treats the battery carefully, it should never need to be opened.
sailorman
Well-Known Member
normally a small red bung at the top @ one end
D
Deleted member 36384
Guest
Don't know if the sealing is normally permanent or not. On my sealed motor bike battery the plastic lids can be prised open with a small, thin bladed screw driver.
prv
Well-Known Member
Errm, isn't that the whole point?
(There will be some sort of opening through which they filled the thing, and which will burst open to relieve the pressure if you seriously over-charge it, but you don't need to do anything about those. They're probably hidden under a label.)
Pete
NormanS
Well-Known Member
The whole idea of Sealed batteries is that you don't have to open them to top them up. Very useful if your batteries are fairly inaccessible like mine.
RichardS
N/A
What I find interesting is that lead acid batteries gas as they self discharge. I used to use my motorbike battery as a starter battery for the electric starter motor on my glowplug powered R/C powerboat and when I took it in the car down to the lake I used to stick a bung in the plastic vent on the side of the battery just in case it fell over.
I once came home and rather than put it back in the bike I stuck it in a cupboard but forgot to remove the bung. When I came to fit it back on the bike a few weeks later because the sun was out, the battery sides had swelled outwards like a baloon! I carefully removed the bung but the sides were stretched and it would not fit in the bike battery carrier so I stuck it in the vice and squashed it flat again.
I continued to use it as it seemed to work just as well after this treatment!
Richard
I once came home and rather than put it back in the bike I stuck it in a cupboard but forgot to remove the bung. When I came to fit it back on the bike a few weeks later because the sun was out, the battery sides had swelled outwards like a baloon! I carefully removed the bung but the sides were stretched and it would not fit in the bike battery carrier so I stuck it in the vice and squashed it flat again.
I continued to use it as it seemed to work just as well after this treatment!
Richard
NormanS
Well-Known Member
I suspect that there may be a difference between a "sealed battery", and an ordinary battery with its vent temporarily plugged.
theoldsalt
Well-Known Member
Perhaps a difference between "sealed" and "maintenance free" ?
RichardS
N/A
There certainly is but my point was that they presumably all gas as they self-discharge. Sealed batteries re-absorb the gas but wet batteries clearly don't.
Richard
prv
Well-Known Member
There certainly is but my point was that they presumably all gas as they self-discharge. Sealed batteries re-absorb the gas but wet batteries clearly don't.
Ordinary "sealed" batteries are also wet, of course.
There are catalytic caps that recombine hydrogen and oxygen into water (though not 100% of it), found on expensive traction batteries. You'd expect to still add water to these, but at a much reduced rate than without the catalyst. But bog-standard "maintenance free" leisure batteries don't have such technology. They rely on a combination of less-aggressive charging, less frequent use (caravan used a couple of times a year vs golf carts thrashed daily), possibly a bit of extra depth above the plates when new if you're very lucky, and ultimately, lower expectations. Dead after five years? Shrug shoulders and go back to Halfords for a new one.
Pete
ianj99
Well-Known Member
This is why its not recommended to use SLAs for demanding use - ie deep discharge with rapid charging.
VicS
Well-Known Member
Plevier
Well-Known Member
All depends whether you mean "sealed lead acid" or do you mean "sealed maintenance free".
Sealed lead acid (SLA) or valve regulated lead acid (VRLA) or absorbent glass mat (AGM) batteries - all the same thing, VRLA is the official ISO/BS term now - have no free liquid acid in them and no removable plugs. When being charged the electrolysis gases recombine internally with almost 100% efficiency. This is not catalytic. They vent via a pressure relief valve if overcharged. The positive pressure helps the recombination. Gel batteries also recombine but much less efficiently. You cannot top any of these types up.
Sealed maintenance free or MF is a wet battery with a large electrolyte reserve, low gassing when correctly charged and should not need topping up during its working life. They do vent somewhere. Sometimes there is a pipe connection with a sealing plug, sometimes the venting is concealed and will have a ceramic or sintered polymer disc that stops spillage and is also anti explosion, it stops flashback in the same way as a Davy mining lamp does. Often you can top up MF batteries by finding the vent cap(s) under a label, or it may be a lever out strip. If you repeatedly fast charge, topping up may be necessary. The maintenance free "warranty" is usually based on never going over 13.8V, 14V if you're lucky.
There is constant confusion of these terms, not surprisingly. The pic in VicS's post is an MF, not an SLA.
Sealed lead acid (SLA) or valve regulated lead acid (VRLA) or absorbent glass mat (AGM) batteries - all the same thing, VRLA is the official ISO/BS term now - have no free liquid acid in them and no removable plugs. When being charged the electrolysis gases recombine internally with almost 100% efficiency. This is not catalytic. They vent via a pressure relief valve if overcharged. The positive pressure helps the recombination. Gel batteries also recombine but much less efficiently. You cannot top any of these types up.
Sealed maintenance free or MF is a wet battery with a large electrolyte reserve, low gassing when correctly charged and should not need topping up during its working life. They do vent somewhere. Sometimes there is a pipe connection with a sealing plug, sometimes the venting is concealed and will have a ceramic or sintered polymer disc that stops spillage and is also anti explosion, it stops flashback in the same way as a Davy mining lamp does. Often you can top up MF batteries by finding the vent cap(s) under a label, or it may be a lever out strip. If you repeatedly fast charge, topping up may be necessary. The maintenance free "warranty" is usually based on never going over 13.8V, 14V if you're lucky.
There is constant confusion of these terms, not surprisingly. The pic in VicS's post is an MF, not an SLA.
pessimist
Well-Known Member
Thanks all.
Binman
Well-Known Member
You might find that you have a small round window that shows colour green, when charging or or full which would mean battery is fine.
oldharry
Well-Known Member
? They were fitted as standard on electric bikes where they could be in daily use on a deep discharge/charge cycle. Makers always specified ONLY use the supplied charger which controlled the charge rate, but the batteries were standard SLAs usally around 12AH (mine are, anyway) . Newer machines use LiOn or suchlike which have much better capacity/weight ratios.