Battery charger problem

Many of the cheap packs will have the third and sometimes fourth terminal in place but nothing connected to it inside as they are copies of the packs used on older units from other manufacturers .

Can't say I've ever heard that?

The term lithium battery covers a multitude of sins. Primary lithium batteries have a fully charged voltage of 3.7V. On the other hand lithium-ion and lithium-polymer secondary cells have a fully charged voltage of 4.2V. If you charge them to a voltage of 3.7V they aren't fully charged. To complicate it even further LiFePO4 batteries have a fully charged voltage of around 3.8V.

Andrew

You're right Andrew,

That's how I thought it worked, but i checked the data sheet and misread it!

A cheap way to restore fully zonked* cells.

Neil

*Technical term...

Third is a thermistor. If you have a TP4056 module you can (with care) lift pin1 from the ground plane and connect it to the third terminal and it will suspend charging when the pack is too cold or warm.

The datasheet has an example circuit that shows a pair of resistors between + and - supply as a potential divider for pin 1, if high impedance compared to the thermistor and set to give an appropriate voltage thid would allow charging of packs with no thermistor connected. The standard thermistor is ~10K @25C it appears so a pair of 100k resistors would probably suffice.

Neil

Just to digress but still batteries, but Nicads, back in the seventies I was using ultrasound equipment that used rechargeable Nicad battery packs. When we returned from an inspection we would remove the metal clad Nicad pack and place it onto a bench equipped with chargers, one day returned and placed the used battery on charge as usual and left the workshop in search of a very welcome cup of coffee. Quite soon became aware of a crackling sound accompanied by acrid, probably highly toxic, smoke emanating from the equipment room, inside the battery that had just been put on charge was spitting flames and smoking furiously. Power was disconnected and said battery unceremoniously dumped outside, once it had cooled it was retrieved and a post-mortem carried out. The metal case was opened and the cause of the fire was a short circuit with one of the connecting links of the Nicaad cells that had chafed and the insulation failed and the connecting link core made contact with the metal casing of the battery pack, giving an instant fire. I was quite disturbed by this incident because we regularly carried our test equipment with us on aircraft flights, the thought of such a re-occurrence whilst airborne with the equipment stowed in the freight hold didn’t bear thinking about. I am glad that airlines today have at last realised the possible problems of batteries, nicad or li-ion, if carried in aircraft.

Dave W

Thank you, everyone for your help and information. I have to admit a great deal was above my "red is positive, black is negative" level of knowledge - got totally floored by NDIY's mention of 3.7 and 4.2. Am I to understand that I'm dealing with made up series connected packs to provide the 12v? That would entail a REAL stripdown of the cells to do anything remedial, so the bin is looking likely!

rgds

Bill

You will find that the triangular 12V Parkside batteries have changed in the last year. at first glance they look the same, 12V, 2ah, but the new ones do not fit the older tools. The newer type are available at most Lidl shops and a range of tools including an SDS drill, angle grinder and drill driver are on sale especially in the larger shops.

Edited By old mart on 07/10/2019 21:33:30