Charging Ni-Cd batteries in a Ni-Mh charger. Is it ok?
- Thread starter JoPalm
- Start date
Only if your charger is made for Nicad's. I'd check with the manufacturer of your charger to make sure. If it's not made for a Nicad battery, you could damage your batteries, charger or worse. I have a Maha C204xx and it charges both Nicad's and NiMH's. I think it has to be a "smart charger", so it doesn't overheat the batteries.
Check out Thomas Distributing for info on this. They have some FAQ's and you can email them if you want. They are the place everyone seems to go to on the digital camera forums for friendly knowledgable advice (and products).
Sal
Check out Thomas Distributing for info on this. They have some FAQ's and you can email them if you want. They are the place everyone seems to go to on the digital camera forums for friendly knowledgable advice (and products).
Sal
If it's a trickle charger, the kind that requires at least 12 hours to fully charge dead batteries, it will be fine. But if charges faster, it depends on how it senses full charge.
When nicads approach full charge, their voltage drops slightly, while with nimhs it just stops rising. So a nimh charger that senses this drop will overcharge nicads.
Nimhs don't heat up until they reach full charge, while nicads heat up before then. So a nimh charger that senses temperature will undercharge nicads.
Some charger chips, such as the Maxim MAX2003A, sense rate of voltage and temperature rise rather than constant values, making them suitable for both types of batteries.
Linear Technology and Maxim Integrated Products make battery charger chips and have a great deal of applications information about them.
When nicads approach full charge, their voltage drops slightly, while with nimhs it just stops rising. So a nimh charger that senses this drop will overcharge nicads.
Nimhs don't heat up until they reach full charge, while nicads heat up before then. So a nimh charger that senses temperature will undercharge nicads.
Some charger chips, such as the Maxim MAX2003A, sense rate of voltage and temperature rise rather than constant values, making them suitable for both types of batteries.
Linear Technology and Maxim Integrated Products make battery charger chips and have a great deal of applications information about them.
I don't know who makes the Ni-Mh charger I have since it came with my olympus camera. It's an "Olympus Ni-Mh batter charger BU-100". I can't find anything on their site about recharging nicads in them. Takes about 3 hrs and a bit to charge my nimh's. All the nimh's i have are 1600mAh. Havn't tried nicads in them yet cause i don't know what might happen..hehe.
Thx for the info guys.
Oh one more thing. What's the usual mAh on nicads... I have a pair of rechargable sony ones that are 700mAh but i'm wondering like what are those duracell and energizer ones rated at...can't find them on the batteries..ehhe
Thx for the info guys.
Oh one more thing. What's the usual mAh on nicads... I have a pair of rechargable sony ones that are 700mAh but i'm wondering like what are those duracell and energizer ones rated at...can't find them on the batteries..ehhe
I also have that Olympus charger along with the Maha and I wouldn't put Nicad's in the Olympus charger. It's a "dumb" charger unlike the Maha's "smart" charger. I bought the Maha with a set of batteries for $35 as an extra charger and it turned into my main charger and only use the Olympus charger now in a pinch. I thought that this was cheaper and better than the $50 Olympus charger/battery combo.
jamarno: Well done! Thanks for the very insightful explanation on how the chargers and batteries work. All I knew was that it's basically a no no to charge Nicad's in certain chargers designed for Ni-MH's.
Like I said, you may get a definitive answer from the guys at Thomas Distributing on whether the Olympus charger will be ok for Nicad's. They sell a ton of batteries and chargers to us folks over at rpd (rec.photo.digital). You might also want to visit the NG if you're into that sort of thing. Lot's of very knowledgeable people over there too.
Sal
jamarno: Well done! Thanks for the very insightful explanation on how the chargers and batteries work. All I knew was that it's basically a no no to charge Nicad's in certain chargers designed for Ni-MH's.
Like I said, you may get a definitive answer from the guys at Thomas Distributing on whether the Olympus charger will be ok for Nicad's. They sell a ton of batteries and chargers to us folks over at rpd (rec.photo.digital). You might also want to visit the NG if you're into that sort of thing. Lot's of very knowledgeable people over there too.
Sal
My brother has an auto charger that charges both Nicd and Nimh. Although there is a switch to set the type of battery I believe it?s for the ?auto-sensor? (and not the charging rate). The voltage peaks for Nicd/Nimh?s when they reach full charge react slightly different so the sensor has to change it?s settings.
Nicds and Nimh cells are the same voltage ?~ 1.20 ?and charge at the same voltage so ??essentially? ? you can charge them both in the same charger. I charge Nimh?s in my old Nicd charger all the time, but they take about 2x as long to charge because Nimh?s have a much higher rated capacity.
7hrs ? Nicd ..600mah ?(milli-amp-hours)
14hrs ? Nimh 1200mah
A lot of the newer Nimh chargers charge at a faster rate because of the higher capacity of Nimh?s (about 2x) 1200-1800 versus Nicd?s which are normally 600-700 - but there are high-capacity Nicd?s rated 1000mah. My old Nicd charger charges AA at ?150ma ? 2.8volts (2 cells) and has no autoshutoff so it?s basically a trickle/slow charger. .
So Nicd?s will charge in a Nimh charger and their charging time will be about half that of Nimh?s (depending on their capacity).
Almost all chargers that charge higher than 0.1C (10% Capacity) usually have an auto sensor that either steps down charging to trickle mode when finished or shuts off. As Jamarno pointed out, if the charger has autoshutoff sensor -it might not sense the voltage correctly so it might shut off too soon or go too long??? Quick chargers also have a heat sensor in case the batteries get too hot. Rayovac has a quick charger that will charge Nimh?s in about an hour ? charge rate = 1.0C.
Both Nicd and Nimh have built in overcharge protection in their chemistry - but it only goes so far. The battery info sites state you can essentially overcharge Nimh?s at ? 0.1C ? (slow charging/trickle)? for a year without doing damage to them - although you will shorten the life somewhat. That?s why they?re rated 500-1000 charges. Best to take them out when charged.
If your Nimh charger charges 1600mah batteries in just over 3 hrs it would probably charge those Nicd?s in 1.5hrs or less. This is a very fast charge rate (much more than 0.1C). I wouldn?t want to leave the Nicd?s in much longer than that.
energizer? ? has some real cool tech information about Nimhs and Nicds.
Nicds and Nimh cells are the same voltage ?~ 1.20 ?and charge at the same voltage so ??essentially? ? you can charge them both in the same charger. I charge Nimh?s in my old Nicd charger all the time, but they take about 2x as long to charge because Nimh?s have a much higher rated capacity.
7hrs ? Nicd ..600mah ?(milli-amp-hours)
14hrs ? Nimh 1200mah
A lot of the newer Nimh chargers charge at a faster rate because of the higher capacity of Nimh?s (about 2x) 1200-1800 versus Nicd?s which are normally 600-700 - but there are high-capacity Nicd?s rated 1000mah. My old Nicd charger charges AA at ?150ma ? 2.8volts (2 cells) and has no autoshutoff so it?s basically a trickle/slow charger. .
So Nicd?s will charge in a Nimh charger and their charging time will be about half that of Nimh?s (depending on their capacity).
Almost all chargers that charge higher than 0.1C (10% Capacity) usually have an auto sensor that either steps down charging to trickle mode when finished or shuts off. As Jamarno pointed out, if the charger has autoshutoff sensor -it might not sense the voltage correctly so it might shut off too soon or go too long??? Quick chargers also have a heat sensor in case the batteries get too hot. Rayovac has a quick charger that will charge Nimh?s in about an hour ? charge rate = 1.0C.
Both Nicd and Nimh have built in overcharge protection in their chemistry - but it only goes so far. The battery info sites state you can essentially overcharge Nimh?s at ? 0.1C ? (slow charging/trickle)? for a year without doing damage to them - although you will shorten the life somewhat. That?s why they?re rated 500-1000 charges. Best to take them out when charged.
If your Nimh charger charges 1600mah batteries in just over 3 hrs it would probably charge those Nicd?s in 1.5hrs or less. This is a very fast charge rate (much more than 0.1C). I wouldn?t want to leave the Nicd?s in much longer than that.
energizer? ? has some real cool tech information about Nimhs and Nicds.
Oh ya, about Energizer and Duracell AA?s.
Alkaline AA?s are generally rated about 2800mah (milli-amp-hours)compared to Nimh rechargeables which are 1200-1800. (I think rechargeable alkalines are only 1000mah.). The problem with alkalines is that they achieve a 2800 rating at a very low discharge rate ? typically ? 1/25 ? 1/30C (Capacity). For example; if you discharge alkalines at 100ma (milli-amps) you would get 2800mah/100ma = 28 hours of use. Typical walkman use. If you discharge alkalines at even 0.1C (10% capacity) = 280ma they don?t handle it very well and you will not even get close to 2800/280 = 10hrs use. ? more like 6-7hrs which means the alkalines are now only providing about 2000mah?s worth of power. As you move up the power drain of alkalines more - their power rating gets even much worse. The chemistry in alkalines cannot cope with even moderately high discharge rates while maintaining their power rating like Nicd/Nimh?s can.
One can drain a 1600mah Nimh at 1600ma (1.0C) and it will not even break a sweat. That?s almost 6x the 280ma drain where the alkaline starts to show significant capacity drop off. Most Nimh?s can be discharged at 1- 4x their rated capacity without showing a significant drop in overall output (still 90% their rated capacity or higher). Rayovac tech doc?s state that their Nimh?s can cope with as high as a continuous 10x (10C) discharge rate without damage and 15x for 2-3sec.
This means a 1600mah Nimh can provide way more high-current on demand than an alkaline can even though it?s overall capacity is rated less. It?s also why alkalines don?t work well in digital cameras. Digital camera?s draw quite a high current and generally destroy alkalines which cannot cope with the high current draw. I?ve read of people only getting 30 digital pictures with alkalines where Nimh?s will provide serveral times that.
Some of the newer ??Titanium? ? alkalines have been re-engineered to cope better with high drain devices like digital cameras but they still don?t cope that well and can?t touch Nimh?s, which provide at least 2x the pictures or more in a digital camera even though their milliamp rating is about ½ that of alkalines.
Blast
Alkaline AA?s are generally rated about 2800mah (milli-amp-hours)compared to Nimh rechargeables which are 1200-1800. (I think rechargeable alkalines are only 1000mah.). The problem with alkalines is that they achieve a 2800 rating at a very low discharge rate ? typically ? 1/25 ? 1/30C (Capacity). For example; if you discharge alkalines at 100ma (milli-amps) you would get 2800mah/100ma = 28 hours of use. Typical walkman use. If you discharge alkalines at even 0.1C (10% capacity) = 280ma they don?t handle it very well and you will not even get close to 2800/280 = 10hrs use. ? more like 6-7hrs which means the alkalines are now only providing about 2000mah?s worth of power. As you move up the power drain of alkalines more - their power rating gets even much worse. The chemistry in alkalines cannot cope with even moderately high discharge rates while maintaining their power rating like Nicd/Nimh?s can.
One can drain a 1600mah Nimh at 1600ma (1.0C) and it will not even break a sweat. That?s almost 6x the 280ma drain where the alkaline starts to show significant capacity drop off. Most Nimh?s can be discharged at 1- 4x their rated capacity without showing a significant drop in overall output (still 90% their rated capacity or higher). Rayovac tech doc?s state that their Nimh?s can cope with as high as a continuous 10x (10C) discharge rate without damage and 15x for 2-3sec.
This means a 1600mah Nimh can provide way more high-current on demand than an alkaline can even though it?s overall capacity is rated less. It?s also why alkalines don?t work well in digital cameras. Digital camera?s draw quite a high current and generally destroy alkalines which cannot cope with the high current draw. I?ve read of people only getting 30 digital pictures with alkalines where Nimh?s will provide serveral times that.
Some of the newer ??Titanium? ? alkalines have been re-engineered to cope better with high drain devices like digital cameras but they still don?t cope that well and can?t touch Nimh?s, which provide at least 2x the pictures or more in a digital camera even though their milliamp rating is about ½ that of alkalines.
Blast
One more tid-bit.
Nimh?s have even a little higher self discharge rate than Nicd?s and will typically lose 30-40% their capacity just sitting on the shelf for a month. After 2 months I wouldn?t expect a set of fully charged Nimh?s to have that much left. Alkalines on the other hand (if I remember correctly) will retain 90% of their capacity for 5-7 years.
Blast
Nimh?s have even a little higher self discharge rate than Nicd?s and will typically lose 30-40% their capacity just sitting on the shelf for a month. After 2 months I wouldn?t expect a set of fully charged Nimh?s to have that much left. Alkalines on the other hand (if I remember correctly) will retain 90% of their capacity for 5-7 years.
Blast
One more post regarding Ni-MH's they dont like a high charge or discharge rate compared to Ni-Cd, I've proven this in my RC 4WD buggy- I killed a new set of Ni-MH cells in weeks by using the fast 15 minute charger on them, the drain from the Mabuchi motor is in the order of many amps too, the Ni-Cd cells last about a year.
Ni-Cd and MH batteries have a very low internal resistance which means they can deliver enourmous amounts of current, if a circuit fails and badly designed (without fuses, current and temperature) then rechargeable batteries can easily start a fire because of the current they can deliver, whereas alkalines and carbon batteries will just fade off progressivly. Alkaline and carbon batteries have a linear voltage decay curve, so as you use the battery, the voltage gradually gets lower and lower and lower.... Ni-Cd's and MH's have a more logarithmic(but not exactly) voltage decay curve, they have an open circuit voltage of 1.24 volts (alkalines have 1.5v) and will maintain at least 1.1 volts over 90% of their charge so it is much more difficult to predict the life of a rechargeable battery, but the benefits are great in that the battery can keep a product operating in the desired region for much longer durations.
I thought I'd post some more useless info for y'all to ponder over
Cheers
Ni-Cd and MH batteries have a very low internal resistance which means they can deliver enourmous amounts of current, if a circuit fails and badly designed (without fuses, current and temperature) then rechargeable batteries can easily start a fire because of the current they can deliver, whereas alkalines and carbon batteries will just fade off progressivly. Alkaline and carbon batteries have a linear voltage decay curve, so as you use the battery, the voltage gradually gets lower and lower and lower.... Ni-Cd's and MH's have a more logarithmic(but not exactly) voltage decay curve, they have an open circuit voltage of 1.24 volts (alkalines have 1.5v) and will maintain at least 1.1 volts over 90% of their charge so it is much more difficult to predict the life of a rechargeable battery, but the benefits are great in that the battery can keep a product operating in the desired region for much longer durations.
I thought I'd post some more useless info for y'all to ponder over
Cheers
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