cyclon battery top up ?

If it is the Hawker / Enysys cyclon type batteries, they are AGM and I did not know any maintenance was possible or advisable other than a recharge. I have never topped one up, or attempted disassembly (all my old bikes are fitted with them and I have only ever had one fail). I would wonder if they can safely be topped up and even if they can, would they still reliably reseal after disassembly / reassembly? Could do more harm than good. I would be inclined to buy a new one. There is a manual available on-line if this helps:

https://www.enersys.com/493c0d/globalassets/documents/product-documentation/cyclon/amer/us-cyc-am-007_0408.pdf

Hi Robert,
Cyclon batteries are brilliant and can have a 15 to 20 year life in float charge situations.
They do not tend to self discharge and i have had batteries at 10 years without charge still hold a voltage above the recommended recharge of 2V per cell (6V across terminals).

if the cell access you are referring to is the plug in the centre then this is not to be removed. it is an emergency valve to ensure the pressure can escape safely in the event of a fault or overcharge. it is fully sealed at all times, even to the point these can be used in a vacuum!
The lead is so pure in these that if you have pulled the plug out the internals will start to oxidise and the battery will be ruined in no time.

The oxygen recombination chemistry in these batteries is around 99% so they do not require any "top up" for their life. if you look at the document link submitted by Steve section 3.5 explains the chemistry

How do i know this, i design industrial standby battery chargers and in 25 years we have sold hundreds and thousands of cyclons (amongst others) and very rarely do we get any issues.