honeywell controller (onboard battery replacement)

i have a 690 honeywell controller the battery is soldered in can i get a replacement batterr if si where

Is it a 699? If it's soldered in I doubt it

I wouldn't be surprised. Post a closeup photo of it including the text.

I needed a similar thing, @bernardgreen showed me what to look for. IIRC it was dark green and once you know the number they are easy to find. I have also had a timer with a battery like a PC motherboard clock button battery, I had to buy a new battery holder with pigtails as it was easier to solder them

Here we are

A 690? Are you sure the number is 690?

I very much doubt even if you could
you are never going to source a new battery for it

Assuming, you're looking at one of these, the question is if it is worth the effort? The days of the programmer and thermostat are in the main over, being replaced with the programmable thermostat, so one can select different temperatures through the day.

The demise of the tungsten lamp, which gave us inferred heat in the evening, boosting the temperature feel of the room, has resulted in people wanting the thermostat to have a higher temperature in the evening to the main part of the day. I moved to one of these years ago, there are models which can also do DHW, today I have a mixture of old and new the old (bottom) does the flat, hardly ever used in winter, and the Nest Gen 3 (top) does the DHW and the central heating is in parallel with the Drayton Wiser (right) as found one thermostat to fire the boiler is not enough, and made a mistake with Nest, as found it will not link to TRV heads, so main house three thermostats can fire the boiler.

This also means if a thermostat fails, we still have some central heating. I am not saying copy me, but I am saying think about what would improve the system, and even if one bit at a time, work out a plan as to what to replace to improve the system.

The battery for the 699 is readily available https://www.heatingcontrolsonline.co.uk/replacement-battery-for-honeywell-st699-p-82.html But there are many sources of similar batteries e.g. CPC Farnell once the size and ratings are known from the markings and likely significantly cheaper.

Pretty sure I've swapped one on my Honeywell controller last Century. Easy enough if one is competent with a soldering iron.

But this may be the opportunity to replace the controller with a more up to date device... e.g. Drayton Wiser.