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I have a Philips QT4045/70 beard trimmer which I’vee had for 12 years and has served me really well. I’ve had to charge it much more frequently recently and it is not operating with enough power to trim by beard very effectively. Inspired by an iFix article from the US I decided to take it apart to see if I could replace the batteries. After great difficulty I managed to do this without breaking any of the pieces (although I haven’t put it back together yet!). However, the batteries are unmarked other than with the following: “SAN NiMH 8JH” I’ve search everywhere I can think of online for information and even contacted Philips but they won’t give me the battery specification, they claim it is proprietary data. I know the batteries are Nickel Metal Hydride and I’m pretty certain they are 2 AA batteries joined together so I think they will be v1.2 each (total 2.4v) but can’t be certain and I’ve no idea of the capacity. I’ve found a few places selling the battery units I need with the metal tabs to solder onto the wires in the beard trimmer but without the specification for the original battery I’m reluctant to risk using any of these. My battery knowledge is pretty limited but I’m worried that there will be an issue charging replacement batteries with the original charger if the new ones are a different spec. I separated the original battery unit to see if there was anything written on the joined section that would give me more information but nothing. Each battery has the following dimensions: Height = 49 mm Diameter = 13 mm So the original unit is 26mm wide as the 2 batteries were attached along their lengths. Does anyone know which batteries I can use? As I said my main concern is the charging of these replacement with the original charger but I also need to know the batteries will power the trimmer. Any help much appreciated. Thank you very much,
Hi @mussiefixer , Just get the largest capacity NiMH AA solder tab batteries that you can or want and install them as per the original batteries. You mentioned 2.4V so presumably they are in series connection i.e. +ve of one battery connects to -ve of the other. When batteries are connected in series connection however the current capacity (mAH) of the overall “battery” in not increased, only the voltage e.g. 2 x 1.2V 2000mAH batteries in series = 2.4V 2000mAH battery. When batteries are connected in parallel connection i.e. +ve of one battery connected to +ve of the other, then the voltage stays the same but the current capacity is cumulative e.g. 2 x 1.2V 2000mAH batteries in parallel = 1.2V 4000mAH battery Just ensure that they’re a recognized brand as with them you are more likely to get the stated capacity than unknown brands. In this instance capacity only matters because it determines how long the trimmer can operate on the batteries before they need to be recharged, i.e. the greater the capacity the longer it will operate but conversely the longer it will also take to recharge. The trimmer’s battery charging circuits will monitor the battery voltage as it rises when the batteries are being charged. I’m assuming that there is no thermal monitoring i.e. no sensor connected to the batteries so the charging circuits rely on monitoring the battery voltage and the charge current. As the battery voltage increases the charging current will decrease as the battery voltage is in opposition to the charging voltage
This battery replacement video should help as well as it discussed battery types https://www.youtube.com/watch?v=--ou2OKV…
