Are sealed lead acid batteries safe?

[TonyS]

My original equipment Bosch lead acid batteries are now 10 years old and although working OK, I am going to replace them. I would like the same mounting, as the base clips can then be re-used.
The equivalent 140 Ah battery with same dimensions and mounting is a Varta Commercial K8 630 HD Battery, at £133. However like most batteries today, it is sealed.
When I look at my CRV car battery, at 8 years old, is also sealed.
When a sealed battery reaches the end of its life, how does it fail? A battery with fillers on each cell shows a loss of water in the failing cell. This cannot happen in a sealed battery, or can it?
All gel batteries are sealed, and are quite common on boats.
Is there any problem in replacing with a sealed battery of equivalent spec?

 

[macd]

Many so-called 'sealed' batteries in fact are not. Often all you have to do is peel off a big label to reveal top-up buttons underneath (as I did the other day with a 'sealed' Bosch).

 

[TQA]

Yes they are safe. Just have a charge rate limit. Even if overcharged they have safety valves that pop so you get venting.

 

[pvb]

Totally safe. They're not "sealed", but have a pressure sensitive valve to vent them if they gas excessively. Most "sealed" batteries don't have a facility to top up, even if you rip the labels off them. I have a bank of sealed batteries, and experience indicates they last 8-10 years in my usage pattern. Failure mode is either progressive loss of capacity, or failure of one cell (usually shorted) which shows as a reduced voltage.

 

[TonyS]

Thanks all. I will now buy with confidence!

 

[cliff]

Thanks all. I will now buy with confidence!

Don't - have a hunt around first for flooded cell batteries - the type one can top up - they take a lot more punishment than the "sealed" type and can be charged at higher rates. Conventional wet cell batteries are available.