TapHeating Programmer Battery

There everyone is, trying to get us to save energy and they make a domestic piece of equipment that has no obvious way to change the battery. Yes, it is rechargeable, but after a while even these will die. They do it with cordless phones, and now I find our heating programmer is the same. After the five or ten years it lasts, we are supposed to throw it away and buy a new one. £60 for the sake of a £2 battery. I am not beaten so easily!

ACL Lifestyle LP722 Programmer

The item in question is an ACL Lifestyle LP722 Programmer. This one dates from about 1990 but it is still made by Invensys under the Drayton brand and, as far as I can see, is very little changed though the brochure says they now have lithium batteries, perhaps they are easy to change.

This older model has a 100mAh NiCd battery, part number V100R. This is no longer made (NiCd is going out of style) but the 150mAh NiMH battery, part number V150H/2p is a direct replacement. I got mine from Cell Pack Solutions for £2 + VAT + P/P = £3.34. Quite reasonable I thought, from a specialist supplier. To find if yours is the same you will have to go through some of the following steps to identify it first and perhaps put it all back together while you wait for the part to arrive.

Now down to business. First you need to make sure you have noted down your program settings. This can be done by stepping through the test sequence on the controls to see when things come on and off. Now you need to TURN THE POWER OFF. This is important for your safety and for the equipment. There should be a double pole isolator or remove the mains plug or whatever is needed.

You can remove the programmer from the wall by loosening the screws marked with the red arrows on the picture above. They don’t need to come right out and, in my case, also watch you don’t drop the screwdriver down the back of the bookcase. Now gently pull from the bottom and then lift it off the lugs. It will be a bit sticky because there are 6 pins to come out of their sockets.

Programmer back

Now turn it over and remove the 3 screws marked with red arrows on the second picture. The back can now be removed but note the clips marked with blue arrows which need to be pushed clear. The back needs to come off leaving the six pins behind so take a bit of care.

Programmer circuit board

Now you can see the circuit board. The battery is marked with a blue arrow on the third picture. This is far as you need to go if this is a preliminary investigation. You can see what sort of battery you need, though it may be hard to read the number.

Once you have got your replacement you need to remove the three screws marked with red arrows and carefully lift out the circuit board. This should leave behind the display screen and contact strip marked with red arrows on the last picture. but it may stick to the back of the circuit board. If so, carefully separate them and put it back as shown. If you are unlucky, the cover strip (not shown) and all the buttons will fall out as well. If so carefully put them back in the right order (they have thoughtfully marked the + and – positions) and replace the cover. Take care not to lose the rubber push buttons off the back of the circuit board, but these are all the same.

Programmer inside case

Now you can de-solder the battery; a de-soldering wick or solder pump is best for this, otherwise you will have to use three hands and a pair of pliers! Assemble the new battery in the carrier and solder it into place—the single pin side will need to be soldered on both sides of the circuit board.

To re-assemble, reverse the process above. Be sure to get the rubber buttons correctly located. Don’t over tighten the screws as it is easy to strip the thread. Once it is all back together you can replace it on the wall by hooking over the lugs first then firmly pressing it into place before tightening the screws. Now switch the power back on. It will need re-programming but after about 3 days it should be re-charged and providing a backup.

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