That's amazing. I want to try it.
The Eneloop datasheet say the batteries shold be charged at 1C.
The only reason you don’t see missed terminations on C9000 when using a ridiculously slow charge rate is because the C9000 terminate Eneloops on voltage not dv/dT or such.
This is from FAQ of Maha:
How does the MH-C9000 detect end-of-charge signals from the batteries?
The MH-C9000 uses a combination of Negative Delta V, Zero Delta V, Peak Voltage, time and temperature to determine the end-of-charge. In addition, proprietary algorithms are used.
Some answers here:
I have an old Uniross 15 minute fast charger that charges cooks AA’s at 4.5 amps!
When I got my c9000 I checked all my old AA’s. The Uniross cells had capacities of about 700 mAh, only my old Duracell AA’s survived the abuse from the Uniross with capacities of around 1400 mAh.
[quote=mfm]
The Eneloop datasheet say the batteries shold be charged at 1C.
/quote]
The 1C rate is considered the upper limit in a Fast Charge mode:
http://www.eneloop.info/fileadmin/web_data/Data-Sheets/HR-3UTGB.pdf
For longer cell life, .5C is recommended.
Recommended where? Not in the data-sheet you linked.
It does apply, the reason it’s not done is because the charger is not powerful enough. Industrial applications can go far, far higher with batteries of many times a D cell capacity.
Maha MH-C9000 FAQs
MH-C9000 Frequently Asked Questions
Basic Operations
What are the recommended charging and discharging current for my battery?
The recommended charging current is 0.5C, or 0.5 times the battery capacity. The recommended discharging current is 0.25C, or 0.25C times the battery capacity.
Both Sanyo and Duracell recommend 1C charging in their technical specifications.
I’m guessing that D cells have more problems getting rid of the heat that builds up during charging. The surface area is less than 3 times the surface area of an AA.
Right before I put up this thread I went ahead and charged the 4 Powerex batteries that came with the charger, AA’s listed as 2700mah. Charged them at 500ma, the batteries finished charging at anywhere from a low of 2984mah to a high of 3186mah. Those numbers seem high to me, are they bad or damaged?
Sounds like you have some really nice cells. I personally charge my Powerex AAs on my C9000 on the preset 1000mA setting. It’s also good to do a full Breakin on the C9000 when charging up new cells.
charging efficiency on NiMH is about 70-80, so if they are 2000mAh cells that were fully discharged it should take about 2500mA to charge them. Most electronics don’t fully drain the batteries, my GPS will die at about 30 charge
Your batteries may have different self discharge rates or come from different batches, so depending on how long since they were made they will self discharge at different rates, assuming the charger never missed any terminations.
+1
I think it's unlikely that they are damaged. But I would increase the charge rate as suggested by Ouchy.
Also, you must remember that due to charging inefficiencies the cells will always take in more energy than their rated value.
A break in or forming charge is sometimes recommended as a yearly task. If these cells have been sitting for a long time without use it would certainly be worth doing. Keep in mind that a break in cycle can take almost 40 hours.
(In this case don't forget to discharge your cells first before you begin the break in.)
Are the figures you quoted charged mAh, not discharge ‘Available Capacity’? If they are figures from Charge mode, they are always higher than the nominals of the cells you put in.
Those are the numbers that popped up for each cell after charging was complete. Only charged the batteries with the charging mode at 500ma, took about 5.5 to 6 hours. If I’m not mistaken those numbers popped up twice in each sequence, or the 2 numbers that popped up were almost the same, say 2984 vs. 2986.
Edit: numbers came up at the end after charging was complete, also included total charging time, volts,…
Below comes Maha’s FAQ: http://www.thomasdistributing.com/Maha-MH-C9000-FAQs_ep_42-1.html
I am using the CHARGE mode. Why is the capacity different than my battery capacity?
The capacity displayed in any charging process is called the “charging capacity.” This is the amount of energy put into the batteries. This number does not equal to the battery’s capacity as it is dependent on the amount of charge already in the battery as well as the battery’s internal resistance.
For example, a half used 2000mAh battery may only show a charging capacity of 1000mAh since the battery is half full.
It is normal for the charging capacity to exceed battery capacity by as much as 30% depending on battery brand and charging rate.
To determine the battery’s useful capacity, you must look at a “discharge capacity.” Such information is available in the REFRESH & ANALYZE, BREAK-IN, DISCHARGE, and CYCLE modes.
Note that the battery is not recharged in the DISCHARGE mode.
On the Powerex batteries after charging them at 500ma, did a 500ma discharge and the capacities were 2373, 2420, 2372, and 2384. Did a refresh and analyze(1000ma charge, 500ma discharge) and the capacities were 2444, 2460, 2426, and 2420. So the numbers I listed earlier were not the actual capacities.
I use the standard charging current (1000 mA) for 1900 - 2100mAh nimh batteries in the Maha MH-C9000.
For AAA batteries i set the charging current to 400 or 500 mA (discharge 300 mA).
My oldest low selfdischarge AA batteries (GP Recyko) must be about 5 years old, and they are still working the same as when i bought them.
Even the very cheap Aldi Top Craft Ready To Use batteries are all working prefect after 5 years.
You don’t have to buy expensive batteries, all the low selfdischarge batteries that i use are very good (Recyko (very expensive), Top Craft (the cheapest), Eneloop).