I tried the search but did not really find what i was looking for. I just got a Maha c 9000, and i am curious as to how fast i could safely charge a set of batteries. I am new to this so please be patient. I have a set of energizer 2500 mAh aa batteries. For example would it be safe to charge them at a rate of 5000 mAh and have them charged in around 30 min. I know that fast charging is not the best practice nor will i use fast charging on a regular basis. I am just curious as what my limitations are if i really had to charge them up in a hurry. Also have some Duracell 2300mAh. Eneloops to come in the near future.
Maha c 9000 How fast is safe?
- Thread starter Glock40
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BentHeadTX
Flashlight Enthusiast
Not sure if the Maha C9000 can charge at 5 amps.
I have charged a Sanyo Eneloop 800mAH AAA cell at 1,800mA with a LaCrosse BC-900 without any ill effects that I can detect. Normally, I charge the 800mAH Eneloops at 500mA and they work fine.
I have charged a Sanyo Eneloop 800mAH AAA cell at 1,800mA with a LaCrosse BC-900 without any ill effects that I can detect. Normally, I charge the 800mAH Eneloops at 500mA and they work fine.
Mr Happy
Flashlight Enthusiast
The maximum charging current on the C-9000 is 2 amps, but the charger and cells get pretty warm when you use that setting. I've charged a set of 4 Eneloops at 1.6 A and the cells still feel quite strongly warm at the end of charging. The charger might have terminated on temperature rather then delta-V. It's probably OK, but I would go with the default 1 A charge unless you are in a hurry.
Mr Happy
Flashlight Enthusiast
Well, you could experiment. Just choose a time when you can watch the charger and keep an eye on progress. Others have reported using 1.8 A without problems. (Not that there is actually a problem with 2 A, but some may not like how warm it gets.)
SilverFox
Flashaholic
Hello Glock,
It is best if you don't exceed 1C charging. A 1C charging rate for a 2000 mAh cell would be 2 amps.
Battery manufacturers recommend charging in the 0.5 - 1.0C range, or charging at 0.1C for 14 - 16 hours. Some special purpose cells can be charged at 2C rates, but you should expect reduced cycle life from them.
The 15 minute chargers are proof that you can charge NiMh cells at higher rates, however your cycle life may be limited to around 150 cycles, depending on the cells.
Tom
It is best if you don't exceed 1C charging. A 1C charging rate for a 2000 mAh cell would be 2 amps.
Battery manufacturers recommend charging in the 0.5 - 1.0C range, or charging at 0.1C for 14 - 16 hours. Some special purpose cells can be charged at 2C rates, but you should expect reduced cycle life from them.
The 15 minute chargers are proof that you can charge NiMh cells at higher rates, however your cycle life may be limited to around 150 cycles, depending on the cells.
Tom
TorchBoy
Flashlight Enthusiast
Re: Maha MH-C9000 - how fast is safe?
Current is measured in amps or milliamps. 1000 mA = 1 A.
Capacity is measured in amp-hours or milliamps-hours. 1000 mAh = 1 Ah. It's the amount of current given for a certain amount of time.
Charging a 2500 mAh battery at a rate of 5000 mA (= 5 amps) would have them charged in 30 minutes, as you say. Charging it at 2 amps (the max the MH-C9000 can do) would charge it in about 4/5 of an hour, or 48 minutes.
Forgive me if this is teaching you to suck eggs. (I hope they use that expression in Kentucky.)
Current is measured in amps or milliamps. 1000 mA = 1 A.
Capacity is measured in amp-hours or milliamps-hours. 1000 mAh = 1 Ah. It's the amount of current given for a certain amount of time.
Charging a 2500 mAh battery at a rate of 5000 mA (= 5 amps) would have them charged in 30 minutes, as you say. Charging it at 2 amps (the max the MH-C9000 can do) would charge it in about 4/5 of an hour, or 48 minutes.
You didn't specifiy whether "safe" to you means safe for the batteries or safe for not burning down your house.
Listen to Silverfox, he's spot on.
Charging a battery at it's rated capacity (1C) is the "safest" for the battery in that if you don't exceed that rate, the battery will perform in the way it was designed, and for the approximate number of charge cycles it's engineered to reach.
Charging more than 1C will generally shorten the overall life of the battery, and unless you have a specific reason to charge faster than that (zombies on the way?), you will be happiest with that rate.
It's likely that you could charge at 2C or higher and still not burn the house down, but then you'd be back here at CPF with more questions, this time about why your batteries don't seem to last very long.
GaryF
Enlightened
Don't really understand the reason people want to shorten the life of their batteries by charging them at the high rates....more money than me to burn or maybe just impatient I guess.
Short answer....yes it can be safe to hit a 2500mA AA with 5000mA. Make sure your charger has thermal cutoff/limiting capabilites.
Long answer.....take a look at the Energizer 15 min. charger.....hits an AA cell (from 1 to 4) with a blistering 7.5A.....YES that's 7500mA.
http://data.energizer.com/PDFs/CH15MN.pdf
Talk about shortening the life of a battery.
Actually did some simple cycle tests on a pair of these before getting rid of them. Only tested 3 types of batteries (4 ea.) though (Energizer 2500, I-Power 2300, and Duracell 2300).
Actually had a couple of the I-Power cells (junk IMO) get less then 10 cycles before they died. The other two got less than 25 cycles.
The Energizers (4 of them lasted between 62 and 90 cycles) died pretty quickly too.
The Duracells lasted between 82 and 173 cycles (one cell made it to 173 before it died).
FYI...I consider a cell useless when it can no longer deliver about 70% of its rated capacity.
Granted just simple charging and then using a pair of Lacrosse BC-900's to discharge them all at .5A rate. But, it sure shows that if you want to use the HIGH charge rates, especially rates in the neighborhood of 3C-4C you ARE NOT going to get anywhere near the manufacturers advertised amount of cycles which is usually 500 or 1000.
Even though I don't have the tester to verify it with now, I almost guarantee that if you treat an Eneloop to those rates....you won't get anywhere near the 1000 cycles they advertise.
Besides with the LSD batteries nowadays, I just don't see the NEED to 'BLISTER CHARGE' them (as I call it). Buy a few extra batteries and charge them up ahead of time.
Short answer....yes it can be safe to hit a 2500mA AA with 5000mA. Make sure your charger has thermal cutoff/limiting capabilites.
Long answer.....take a look at the Energizer 15 min. charger.....hits an AA cell (from 1 to 4) with a blistering 7.5A.....YES that's 7500mA.
http://data.energizer.com/PDFs/CH15MN.pdf
Talk about shortening the life of a battery.
Actually did some simple cycle tests on a pair of these before getting rid of them. Only tested 3 types of batteries (4 ea.) though (Energizer 2500, I-Power 2300, and Duracell 2300).
Actually had a couple of the I-Power cells (junk IMO) get less then 10 cycles before they died. The other two got less than 25 cycles.
The Energizers (4 of them lasted between 62 and 90 cycles) died pretty quickly too.
The Duracells lasted between 82 and 173 cycles (one cell made it to 173 before it died).
FYI...I consider a cell useless when it can no longer deliver about 70% of its rated capacity.
Granted just simple charging and then using a pair of Lacrosse BC-900's to discharge them all at .5A rate. But, it sure shows that if you want to use the HIGH charge rates, especially rates in the neighborhood of 3C-4C you ARE NOT going to get anywhere near the manufacturers advertised amount of cycles which is usually 500 or 1000.
Even though I don't have the tester to verify it with now, I almost guarantee that if you treat an Eneloop to those rates....you won't get anywhere near the 1000 cycles they advertise.
Besides with the LSD batteries nowadays, I just don't see the NEED to 'BLISTER CHARGE' them (as I call it). Buy a few extra batteries and charge them up ahead of time.
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BlackDecker
Enlightened
+1 to why bother with Energizer 2500mah cells when you can buy the far superior LSD cells like Sanyo Eneloops or Rayovac batteries... you could have them charged up in advance and never need to blister charge any cell. The LSD cells will hold a charge over a year with no significant loss of power.
Because i already had them before Eneloops ever came out and they work just fine for what i need them for. I dont feel like throwing them away just to buy some new Eneloops. Also in my first post i said that i did not intend to fast charge just asking a simple what if. Just wanting to know what my new charger is capable of. When shopping for a new car i am sure you will be curious as to what the top speed of the car is. That does not mean that you will be traveling at top speed.
BlackDecker
Enlightened
Actually, no I don't care what the top speed of the car I'm shopping for. As long as it will do the speed limit and an occasional jump beyond that speed, that is all I care about. I'm more concerned with a car's longevity, fuel economy, options and features. To each our own, they say.
