I resume this old post.
Someone knows a good charger that can be set below 200mAh for AAA cells?
The smart chargers that Panasonic often bundles with standard Eneloops are slow chargers. Look for models BQ-CC17 or BQ-CC75.
Charge rate is 150mA on the AAA contacts, and 300mA on the AA contacts. These settings are not adjustable.
.THIS.
I was under the impression that too low of a charge current causes the charger not to know when to terminate the cycle
I think I read this on one of HKJ reviews
According to what I have read and seen in my experiences, that is correct.
I usually charge at 1C or slightly less.
I recall some older slow chargers appear to cut off based on time (eg. after several hours).
However, this obviously won’t work well if we remove and re-insert the battery in the midst of charging cycle, as the timer will then reset.
This is what I do. I got enough AA and AAA eneloops kicking around that I don’t need it charged fast. After I charged a cell sometimes they will sit for a month or two before I cycle them into the next device.
Thanks for suggest I’ll check if they have dV termination.
I’m using now the Ikea Vinninge USB (110mAh each AAA cell)
but seem that didn’t have,just a timer.
So if you put an half charge cell it will overcharge,not good
I also want try to build one by myself from 5V source
with auto termination.
The circuit shouldn’t be that complicated
I boiled out a set of Eneloop AAA’s at 1,000 mA charge rate…
I now use 300 or 400 mA rate.
It can, but low enough charge rates also present low risk of harm from overcharging. Also look up HKJ’s test of the BQ-CC75. It uses a very low charge rate (0.16C), but actually terminates early, if anything. You might not get maximum runtime due to not topping off, but it looks like a really gentle charger.
https://lygte-info.dk/review/Review%20Charger%20Panasonic%20BQ-CC75%20UK.html
If you ever look up the details on the battery cycle life test (IEC 61951), the one by which Eneloop gets to claim a 2000+ cycle life, it’s interesting to see that it requires the batteries to be overcharged every single cycle.
Every 50 cycles there is a capacity check cycles that charges at 0.1C for 16 hours = 160% charge
The rest of the cycles charge at 0.25C for 3:10 after an 0.25C discharge for only 2:20 = 120% charge
Whether this is better or worse for the batteries than higher charge rates that use -dv/dt termination, I do not know. I suspect slightly better. Regardless, it’s clear that you can get really long useful lives out of LSD NiMH batteries even if your termination is not very quick, as long as the charge rate is low.
Avoiding deep discharges also helps. The IEC test is a relatively shallow discharge. AA Cycler does relatively fast charge/discharge cycles in his tests, but I believe the main reason his tests get significantly fewer cycles than the batteries are rated for is that his setup discharges down to 0.9V. Even at the cycle lives he gets, however, NiMH are an awesome value.
This is quoted from BatteryUniversity.com
“It is difficult, if not impossible, to slow charge a NiMH battery. At a C rate of 0.1C to 0.3C, the voltage and temperature profiles do not exhibit defined characteristics to trigger full-charge detection, and the charger must depend on a timer.”
Link here BU-408: Charging Nickel-metal-hydride - Battery University
I know BatteryUniversity has been around a long time and maybe slow to update, so maybe the technology has improved.
The most optimal charge currents are around 0.5-1C.
I don’t charge AAA NI-MH at such high currents,they dont tolerate heat well and are easy to kill more than lithium cells.Often their label indicate standard charge very low, like 0.1C
…THIS…
You are good anywhere in the 0.5C - 1C range
I have done this for years with NO problems at all. Never killed a NiMh cell either.
EDIT TO ADD: I have AAA Eneloops that are 8+ years old too. Always charged at 0.5 A.
That don’t mean you instant kill them. in this way their cycles and capacity will be reduced with increases impedance on small NI-MH cells
400mA-500mA for AAAs, is what I use for standard Eneloop types.
Chris
Yep, I have always charged my AAA Eneloops at 500mA. Never once had a problem with them “heating up” during charging.
Some are well over 8 years old & still going strong.
Same here —- 8 yrs + old with very little capacity loss
In your experience, news half-charged LSD should be used or recharged the first time?
What is the ideal voltage for long storage?
I don't think it really matters.
So it's your choice if you want to charge them right away, or just use them as is.