On 17/11/2020 21:08, DJC wrote:
On 17/11/2020 17:17, Martin Brown wrote:

Not dissimilar to an oil tank Watchman and the batteries typically
last a few years so it isn't much of a hassle.

Official Watchman replacement batteries are a ripoff though but tear
down instructions for rep[lacing one are available on Utube.

My Watchman. instruction leaflet included battery replacement
instructions. Just a standard CR2430 from eBay.

The older Watchman models used a custom built set of AA batteries in a
copper pipe and sold for an extortionate amount of money eg.

http://www.tankdepot.co.uk/shop/266_100/oil_tank_gauges_and_security_products/oil_tank_gauges_and_level_monitors/oil_watchman_niveau_series_replacement_battery.htm ?

Appear to be discontinued so DIY is now the only way to do it.

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Regards,
Martin Brown