Rechargeable Batteries in BT Synergy Cordless Phones

We’ve had our set of three BT Synergy 5500 cordless DECT handsets since 2009, and after about 3 years of heavy use, the rechargeable batteries appear to have come to the end of their life.

The manual with this BT handset does state that performance will deteriorate over time, and normal Nickel-metal hydride batteries, like the ones used in this phone, typically can only survive about 1000 full charges. Oddly, it seems that the handset we use least, has fared the worst, presumably as it almost never gets run down to flat and fully recharged.

BT Synergy 5500 DECT cordless

BT Synergy 5500 DECT cordless

Replacing the batteries in the Synergy 5500

The act of replacing the batteries is very straightforward, so no need to go into much detail here. For us, the hard bit was finding the replacements….

BT Synergy 5500 DECT cordless battery compartment

BT Synergy 5500 DECT cordless battery compartment

The two batteries originally supplied with each handsets are as follows:

  • Type: 1.2 Volt AAA Ni-MH
  • Rating: 550mAh
  • Manufacturer: Kaifeng New Energy Co. Ltd (China)
  • Standard charge: 16 hrs at 55mA
Kaifeng 550mAh AAA battery

Kaifeng 550mAh AAA battery

Possibly rather naively, we assumed that it was a simple case of popping out to a high street electrical shop such as Currys, and buying a replacement set of rechargeable batteries. That’s exactly what we did – opting for a set of Energizer 700mAh batteries. These worked perfectly in one of the two handsets be tried, but not in the third identical handset. We also tried a higher capacity 850mAh battery, but this failed to work in any phone, despite being fully charged.

AAA Energizer battery

AAA Energizer battery – not quite a success for us

After consulting the manual and doing some checking online, it seems that BT cordless phones are very fussy about what types of batteries can be used. We put in a call to BT’s Synergy Helpline on
0800 145 6789 to be told that many rechargeable batteries don’t work and it’s important to buy the correct ones that are designed for the phones and with the correct power rating. Apparently only batteries rated between 550 and 750mAh will work – and they strongly recommended buying the correct replacements otherwise the phone may not work.

In the end, we were sold three sets of replacement batteries for £15.98 (inc postage and packing), with an estimated 5 days delivery. (Price as of May 2013)

Since ordering, we’ve found an online shop selling batteries suitable for the BT Synergy 5500 – sell packs of 750mAh with claim to be compatible. Price for 6 batteries is £10.20 including postage and packing – a saving of £5.78 on BT’s price.

We also looked on Currys Partmaster, normally a great place to buy spares, but at the time of checking – no stock. It;s worth having a look though: Partmaster Cordless Phone Batteries

It pays to shop around.

This entry was posted in Phones.

30 Responses to Rechargeable Batteries in BT Synergy Cordless Phones

Leave a Reply

Your email address will not be published.