Maha C9000 NLee the engineer Misleading review

[apagogeas]

I have chargers which run at 0.25C or less, and which seem to terminate pretty reliably - cells seem to have essentially as much in them as when charged at faster rates, and are not unduly warmed at the end of charge.

That is indeed the problem. With such low rates, the cells don't really get hot (so to notice something is wrong) and if there is a missed termination they are cooked to death. You'll never know unless if you time the charge and know in advance how much charge is already in the battery. So, the charge and the charger might look perfectly normal but at the same time it may cook the battery to death and still give the impression everything is just fine and terminates properly and reliably. Batteries can give a good -dV signal even at such low rates, however this is not true under all circumstances during their full extend of useful life (depends on the quality/condition of the battery). Brand new or well used batteries are the most prone to fail at some point in their life in producing the necessary -dV with low charge rates. Very stubborn batteries may fail to produce that -dV even with higher charge rates but the chance of this happening is drastically reduced.

 

[Unicorn]

He's overstating the problem of pressing a button. While technically accurate, he does make it sound almost as bad as a review stating the product is damaging to batteries, or is actually difficult to use.
I'm pretty ignorant about batteries to be honest. Much more so than most people here. And if I can understand a few button presses, almost anyone should be to.

 

[uk_caver]

That is indeed the problem. With such low rates, the cells don't really get hot (so to notice something is wrong) and if there is a missed termination they are cooked to death. You'll never know unless if you time the charge and know in advance how much charge is already in the battery. So, the charge and the charger might look perfectly normal but at the same time it may cook the battery to death and still give the impression everything is just fine and terminates properly and reliably. Batteries can give a good -dV signal even at such low rates, however this is not true under all circumstances during their full extend of useful life (depends on the quality/condition of the battery). Brand new or well used batteries are the most prone to fail at some point in their life in producing the necessary -dV with low charge rates. Very stubborn batteries may fail to produce that -dV even with higher charge rates but the chance of this happening is drastically reduced.

Charged at ~0.2C, my 3x4Ah battery packs are cool through the bulk of charge, and get detectably warm towards the end of charge. If I kept putting them back on charge as soon as charge terminated, they would definitely get rather warmer than they do normally, so even a 0.2C rate seems sufficient to heat them once they are full, hence a lack of significant heat seems a useful signal of, at least, a lack of prolonged overcharge.

Also, with regard to charge termination and low charge rates, almost everyone seems to refer to -dV termination as if that's the only voltage signal that can be used.

I'm sure that many years ago I read datasheets for dedicated charge-control chips which either had selectable termination, or had different chips with -dV and 0dV termination for use with NiCd and NiMH cells respectively.

Possibly people making sub-0.5C chargers for NiMH cells aren't terminating (solely) on -dV.
If using microcontrollers, it's trivial to add multiple termination conditions such as 0dV, max voltage, etc, and also to average many voltage readings to significantly reduce noise and to therefore allow more sensitive termination conditions to be used.

 

[markr6]

NLee has a ton of cred on Amazon, so one needs to be careful when making a decision and to not base it on one person regardless of their knowledge or experience. I for one trust what he's saying but the subjective aspects ultimately come down to the buyer.

For what it's worth, my BC-700 has been functioning perfectly charging 2000mAh Eneloops at 700mA. With my new Eneloops XX (2500mAh), I'm not so sure. The very first charge seemed to get too hot, and the second charge (Test mode) appeared to under charge them to 1.40v and never gave a "Full" indication. The timer simply kept running but they apparently wern't accepting any more charge. I'll keep an eye on the next charge; if I have more issues I'm simply going to get another charger to charge these Eneloop XX's at a higher rate.

 

[rwharold]

I have, with much interest, read all the posts on this thread. I too was confused about the different chargers, but I did my own research before making a decision to purchase the Maha C9000. I thought I would share with all of you my own review of the C9000. I would appreciate any comments that you might have.

5.0 out of 5 stars Best all around charger. Improved version! Better than La Crosse., February 16, 2013
By
Richard W. Harold (Reston, VA) - See all my reviews
(REAL NAME)



This review is from: PowerEx MH-C9000 WizardOne Charger-Analyzer (Electronics)
I did a lot of research on AA/AAA battery chargers before I made this purchase. I read NLee the Engineer's review and several reviews on Candle Power Forums to get the very best advice. I narrowed down the choice between the La Crosse BC 700/1000 and The Maha Powerx C9000 chargers. Almost all the reviews that I read recommended the Maha Powerex C9000 over the La Crosse models. I had questions about each model so I tried to telephone Technical Support at each company. I had no luck what-so-ever with the La Crosse Company. The telephone was answered by a recording saying that Technical Support was busy and asked to leave a message and they would call me back. I tried calling La Crosse three separate times on different days and always got the same recording and NEVER recieved a call back. Then, I tried to call the Maha Energy Company and got through to a live Technical Support person on the very first attempt. I called them several times because I kept having new questions. I got through each time with no delays or recordings. The other deciding factors were the comments about the La Crosse failure rate and having only a one year warranty. The Maha Powerex C9000 comes with a three year warranty and has a more rugged design! After weeks of research, I finally decided to purchase the Maha Powerex C9000. It just arrived yesterday. The first thing I noticed is that it is not as "HUGE" as some reviewers have commented. It's just the right size leaving plenty of room between the batteries for effecient cooling. I first tried to do a Break-In (charge/discharge/charge) cycle on some discharged eight year old Radio Shack 2000 mA NiMH batteries. The charger just would not charge or break them in. The screen went blank and the display went from Break-In back to Charge with nothing happening. I got the same result on all 4 cells. I immediately called Maha and the Technical Support agent told me that my batteries were bad and could not be recharged or broken in by the C9000. The strange thing is that the batteries are used in my fire/police radio scanner which has a 9 V 300 mA power supply/charger which continues to charge my batteries without any problems. I guess there must be some type of defect in the batteries, but they still work! At the same time that I made my purchase of of the C9000, I also bought a 10 pack of the highly rated, new 1500 cycle 2000 mA LSD Sanyo Eneloop AA batteries. After reading the well written instructions on the C9000, I decided to run the new Eneloops through the Break-in cycle as recommended for new batteries. IMPORTANT NOTE: Be sure to FIRST run a DISCHARGE cycle at 500 mA BEFORE a Break-in cycle to avoid over charging 2000 mAH batteries. The manual does NOT mention this critical step, but it's necessary according to the experts at Candle Power Forums and NLee the Engineer. The first thing that I noticed was how very easy it was to program the four separate slots of the charger. Just a few button presses to choose the 2000 mA rating of the Eneloops and that was it. I repeated the process for each slot. Definitely not as hard to program as some reviewers have stated. One thing to remember is that even a brief electrical power interruption will cause the charger to reset to the defaut setting of Charge at 1000 mA. So it's highly recommended to plug the charger into a UPS to prevent any resetting of the charger. I checked the bottom of my charger and noticed that I have production lot number 0L0HA. This must be the very latest version because I noticed a major change in the charger's operation. It no longer makes a high pitched sound when charging as some reviewers have stated. It's totally silent! Yes, the display is bright which makes it easy to read and it makes a good night light for my bedroom. I am thoroughly satisfied with my decision to purchase the C9000. It's a remarakable, well built, and effecient charger. I would highly recommend it to anyone looking to purchase the very BEST charger on the market.