Battery change due to Stop/Start not working

[gerdsooz]

My 65 reg XC60 has had intermittent Start/Stop problems for 3 years, with Volvo not able to rectify beyond changing the support battery 2 years ago and I finally decided to change both batteries after 5 years. Both batteries were easy to change and both original batteries were AGM type and vented. However, my replacements were Bosch S5 and Yuasa with only the Bosch being vented with a hole at the top. The smaller Yuasa support battery did not have a vent hole. I therefore only have the vent tube going to the Bosch (i.e.I removed the further extension that went to the vent hole of the smaller battery). All is good and working as expected. However, I'm wondering if a problem may develop further down the line because the support battery is not vented! Should I worry about my replacement battery not being vented?

[scbamber]

The data sheet for 2020 Yuasa support batteries (eg YBXAX 14) specifically mentions the 6mm end vent hole for vehicle OE breather pipe fitting.

It may be covered with a simple blanking plate and not so obvious.

The risk of not connecting the vent is small but it is better to have no risk. I hope you didn't throw away the old extension tubing and connector!

[gerdsooz]

My battery is https://www.tayna.co.uk/motorcycle-b...yuasa/ytx9-bs/ which is definitely not vented. I've kept the extraction tube in case I need it again. I've actually not found a vented battery matching the spec and vented. Volvo specs don't mention venting. I guess these things are there for a reason. I suspect the Volvo electronics stop the charging process if they detect certain emissions of gasses through overcharging from the vent and that's the danger. Perhaps I'll get one from the dealer...