Thank you wiz for this 90% clear answer.
Most modern Sealed Lead Acid batteries can be used in any orientation at any time although some manufacturer's specifications recommend that they should not be used upside down. I assume that this is something to do with the gas pressure release valve these batteries have that is normally located at the top of the battery.
But why most SLA batteries can be used in any orientations and not all of them. normally SLA is SLA who ever the manufacturer isn't?
It would be wrong for me to say that every SLA battery can be used in any orientation. I'm not sure if I've have seen every battery ever manufactured
or if I have, what if someone manufactures a new one tomorrow that has different recommendations? Wouldn't my 'advice' then be incorrect?
I have noticed that some years ago there were some SLA batteries that recommended orientation in only one way (I'm assuming that this was because they had gas pressure release valves that may not been able to cope with wrong orientation) and these days most manufacturers state that they can be used in all (or most) orientations (new valve design?)
The simple answer is actually that you should always obtain any important information you need to know with the manufacturer of that particular piece of equipment. Different manufacturers may deal with or solve problems in different ways.
This is also why BS also can't always provide definitive recommendations for battery orientation ( and other stuff