What is your favourite battery charger and why?

[keithy]

1. Why not charge at the maximum capacity of the battery. E.g., in the above example, at 2000mA for a 2000mAh battery?

2. Why would the Eneloop data sheet specify charging at 1C when the Maha FAQ http://www.mahaenergy.com/FAQ-C9000/ recommends 0.5C and you charge at 0.3 to 0.5C? (Maybe this has something to do with what you refer to as "charge termination", but I have no idea what that means.)

The higher the charge current, the faster the cells will charge.

However, the higher current tends to be a bit harder on the cells and can lead to a shorter life cycle. On the other end of the scale, too low a charge current can lead to the charger missing termination on the batteries being charged, so they keep charging. Charge termination means the charger correctly identifies that the batteries being recharged are full, and it stops charging.

This is why better quality chargers also include a temperature cutoff as a backup. Full batteries that keep being charged get hot, and this heat is not good for the batteries' life cycle and can lead to the cells venting and losing electrolytes.

At around a 0.5C charge rate, there is good temperature and voltage signs when the battery is fully charged, so smart chargers will usually terminate correctly. I say from 0.3C - 0.5C as some of my chargers have fixed charging rates, like 200mA, 500mA and 700mA. When charging a 2450mAh Eneloop pro at 700mA, that is a 0.35C charge, a 2000mAh AA at 800mA is 0.29C. Other chargers like the Maha can do up to 2000mA in greater increments. My Lacross BC700 does a max rate of 700mA so would be around 0.3C on most of my AA LSD NiMHs. I've been charging them this way for around 4 years, and my oldest cells are still holding capacity at better than +/- 90% of their original capacity.

I need the batteries to charge quicker I will charge at 1C on the Maha, knowing that this might impact on the overall lifecycle of my batteries. People like photographers using multiple AAs for flashes would use this or a higher charge rate to get batteries charged quicker.

These days with me though, I have enough sets of Eneloops and other NiMH cells that I don't need them charged so quickly. So between my goto chargers, I usually have them set at 0.3C or 0.5C when doing a normal recharge cycle.

[peregrinator]

Keithy, yet more excellent information, gratefully received. Powerex should be paying you to write their product information!

[keithy]

No worries. For those interested, NiMHs work on an exothermic hydrogen-based charging and oxygen recombination process. When the charge rate goes over 85% of the charge capacity, the battery internal pressure increases significantly - As the charging process is exothermic, heat is the by-product. When the battery is overcharged the electrical input charge is converted to heat as it cannot charge the battery further. The pressure rises as greater amounts of gas are generated at the charge rate quicker than the battery can recombine. Without safety vents, batteries that are overcharged lead to physical failures.

There have been some stories out there about older type (non-LSD) NiMH rechargeables failing spectacularly, like these:

http://www.scmp.com/article/700123/rech ... des-camera
http://www.scmp.com/article/689950/batt ... -mans-hand

But no details on charger used in these though. One article mentions Camelion brand batteries. I've never experience this though, and generally use good quality chargers, and stay away from "fast" chargers and chargers that don't stop charging and rely on you to switch them off, or a timer.

And as I mentioned, better quality NiMH batteries like Eneloops have venting holes at the positive terminal to release pressure if such an event occurs.

But thankfully NiMH failures are significantly rarer and less dangerous than lithium based batteries.

Regarding the Eneloop datasheet's recommendation of 1C charging, I used to be a bit cynical. 1C will charge the batteries safely and relatively quickly, but probably at the detriment of the battery's life cycle. But if you are a battery manufacturer, you'd want people to keep coming back and buying your batteries, right? I mean, if my batteries are going into their 5th year and still working well, that means I'm not buying more batteries from you in that time. Some of my batches of Eneloops had estimates of 1500 recharge cycles, and I think some went up to 1800 cycles.

Before Panasonic bought the eneloop brand from Sanyo, I thought the older Eneloop datasheets were a little more detailed. The new Panasonic eneloop data sheets are like these https://www.master-instruments.com.au/c ... le/63398/1

You can see the charging current & time mentioned as 2000mA x 1.1hr for a 2000mAh battery. This equates to the 1C charge rate mentioned earlier.

So if you charge a 2000mAh Eneloop at 1C, you will have it charged in about 1 hour. My typical 0.3-0.5C charge rates are a more moderate rate and would charge the same 2000mAh Eneloop in around 2-3 hours. If you have a AAA Eneloop of 950mAh, note that you can go higher than 1C, and it will charge significantly faster, but will impact on the battery's life cycle, and should be done only on if you really need batteries quickly charged.

[Watertank]

A related but not exactly on point question is where is the best place to buy reliable Lithium rechargeable 18650 batteries?- I know I can buy them on ebay etc but having read on various sites that the quality and reliability is not great I would like to use a reputable source.
thanks WT

[Mark F]

I recently purchased some Panasonic 18650B batteries from FastTech who seem to have a good reputation. https://www.fasttech.com/ They cost $17.84 for a pack of 4 (in plastic case). They look right (compared to a couple of others I have) and charged up uniformly. Haven't yet discharged them. These are pretty much the current gold standard at 3400mAh capacity. Anybody quoting capacities above this are highly suspect.

[South_Aussie_Hiker]

18650 are required to be shipped by road freight. Be prepared for a long wait.

[Mark F]

Mine came under expedited freight which only cost a couple of dollars extra - they couldn't be shipped on the free service. Took about 14 days.