How Does a Battery Charger Detect Different Battery Chemistry?

[easysurfer]

Don't worry. I won't go putting in batteries not specified for a proper charger.


Question asked out of curiosity. How does a charger know, say if an AA battery is Ni-cad, Ni-MHi, Alkaline or Lithium Ion. An AA battery will physically fit in an AA charger.

 

[Time2]

Don't worry. I won't go putting in batteries not specified for a proper charger.


Question asked out of curiosity. How does a charger know, say if an AA battery is Ni-cad, Ni-MHi, Alkaline or Lithium Ion. An AA battery will physically fit in an AA charger.

I don't know of a charger that is compatible with all those battery types.

 

[easysurfer]

I don't know of a charger that is compatible with all those battery types.

Not looking for a charger that detects all. But say, an AA charger. How does it tell on battery is Alkaline vs NiCad vs NiMH? Charger won't want to charge an Alkaline, for example.

 

[NW-Bound]

A charger may attempt to autodetect the battery type by its voltage.

Alkaline and zinc-carbon primary (non-rechargeable) cells will have a nominal voltage of 1.5V. Ni-Cad and NiMH cells will be about 1.2V at rest.

A charger will immediately detect an Alkaline cell because its voltage is too high.

I don't believe a charger can differentiate between the Ni-Cad and NiMH types reliably. They are just too close in characteristics and differ only at the terminal charging stage when they are full.

I have not seen a lithium cell in the AA format. Its nominal voltage is either 3.2V for LFP, or 3.6V for other types, NMC, NCA, etc...

I have a lithium charger that will attempt to detect whether an 18650-format cell is LFP or NMC/NCA. I guess it can watch how the cell voltage behaves under charge.

An LFP cell voltage when full is 3.6V. Any attempt to put more charge into it will cause the voltage to quickly rise to 3.7V, 3.8V and beyond. All lithium cells are like this. It's like trying to overfill a bottle. A full bottle cannot take another tablespoon and will overflow.

For NMC/NCA/LiPo lithium types, the full voltage is 4.2V.

 

[Freedom56]

A charger cannot differentiate battery types. Chargers that I have that can charge NiCad or NiMHi have a switch that you have to set. Normally chargers are designed specifically for the battery type they are charging.

 

[MC Rider]

A charger cannot differentiate battery types. Chargers that I have that can charge NiCad or NiMHi have a switch that you have to set. Normally chargers are designed specifically for the battery type they are charging.

On another forum I just saw a battery maintainer for car or MC with a switch for lead acid or lithium. Fwiw.

 

[RobbieB]

Yeah, even the "multi-chargers" I have make you select the type. Even between flooded, gel and AGM lead acid. And of course lithium if capable.

 

[MC Rider]

Have one I got from Dad, it has to be at least 50-60 yo.
Still works, you check to see if it charging by feeling the case for vibration.
There might be a switch for 6v or 12v.

 

[RobbieB]

Those work fine and they work for all types.

Just check voltage often while charging and don't forget to disconnect. Could get messy -

 

[Jerry1]

A charger cannot differentiate battery types. Chargers that I have that can charge NiCad or NiMHi have a switch that you have to set. Normally chargers are designed specifically for the battery type they are charging.

I don’t know, I have this charger and there’s no switch.

Opus BT - C3100 V2.2 Digital Intelligent 4 Slots LCD Battery Charger Compatible with Li-ion NiCd NiMh Batteries

 

[NW-Bound]

I don’t know, I have this charger and there’s no switch.

Opus BT - C3100 V2.2 Digital Intelligent 4 Slots LCD Battery Charger Compatible with Li-ion NiCd NiMh Batteries

The V2.0 manual of this charger makes no mention of the LFP lithium type. It will charge a lithium cell to 4.2V, and this is an overcharge for the LFP cell.

The NiCad and NiMH types are reasonably close, so there's no real danger if the wrong type is chosen by the charger.


PS. The V2.2 version has a manual switch for LFP cell selection. It's internal and the back cover must be removed.

The charger integrates the minus delta voltage for NiCd or NiMh battery charging termination, and for Li-ion batteries charging to 4.2V with pre-selected constant current. ( 3.7 Li-FeO4 and 4.35 type high voltage batteries charging mode can be selected through switch on board )

 

[NW-Bound]

The problem with the internal lithium cell selection switch of the Opus is that you have to open the case to change the battery type.

I have a Miboxer charger which allows lithium cell type selection by pressing a button. This is much more convenient.

The manual of the Miboxer charger has this warning in Chinglish:

LiFePO4/4.35 Li-Ion battery, the charger cannot be identified automatically, you need to manually select the battery type.

If the LiFePO4 is not set manually, the charger will charged the battery as Li-ion 4.2V and the battery is at risk of explosion.

 

[Jerry1]

Most of what I charge are Eneloop AA and AAA batteries. However I do charge one other battery that is a 3.6v 18650

https://olightworld.com/olight-18650-lithium-ion-3600mah-battery

I’ll look in the charger tomorrow to see how the switch is set.

 

[NW-Bound]

Most of what I charge are Eneloop AA and AAA batteries. However I do charge one other battery that is a 3.6v 18650

https://olightworld.com/olight-18650-lithium-ion-3600mah-battery

I’ll look in the charger tomorrow to see how the switch is set.

The above so-called 3.6V lithium-ion cell is the common type that is charged up to 4.2V. The default setting of the Opus charger is for this type. You are OK.

The LFP lithium type is not common in the 18670 physical format. Its nominal voltage is 3.2V. Its maximum charge voltage is 3.6V, although some brands claim they can go to 3.7V.

All this nominal and max voltage ratings can be confusing to the layman, particularly as 3.6V is the nominal voltage of the common Li-ion cell, but this happens to be the max voltage of the LFP cell.

There's another type of lithium chemistry called LTO (lithium titanate oxide), which has a nominal voltage of 2.4V, max 3.0V. I have not seen an LTO cell in the 18650 format.

 

[NW-Bound]

Here's a voltage curve of a Li-Ion cell that I linked from the Web. The cell voltage varies with the load and the state of charge (SOC).

The maximum voltage is 4.2V at 100% SOC, and the cell should not be discharged below 3.0V. The nominal voltage is said to be 3.6V or 3.7V depending on the manufacturer.

The voltage curve of a LFP cell is similar, but maxes out at 3.6V, and the nominal is 3.2V.

 

[Jerry1]

Interesting - Thanks!