battery charging- what settings

[+smstext]

i have ordered a c9000 MAHA battery charger, just wondered if anyone here could suggest what are the best settings to condition the batteries, charge batteries etc.

 

many thanks in advance.

[+Chrysalides]

i have ordered a c9000 MAHA battery charger, just wondered if anyone here could suggest what are the best settings to condition the batteries, charge batteries etc.

I'm not sure about the conditioning settings for the C9000, but for charging, something around 200 mA is nice and gentle on the battery. Use higher settings if you're in a hurry, but normally 200 mA is good. Higher settings generate more heat in the battery and is what kills them.

[roybassist]

Because the C9000 is a smart charger and employs pulse charging, theoretically batteries can be charged at somewhat higher rates without getting too warm.

 

The instructions that come with it say, “Charging at a rate below 0.33C and above 1.0C is not recommended. Charging too slow may prevent the charger from terminating correctly. Charging too fast may damage the battery.” C = battery capacity.

 

The first FAQ on the MAHA web site says, “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.”

 

I use these rates and haven’t noticed any ill effects; but I’ve only had these batteries since August, 2009. 0.5C will charge a fully discharged battery in about 2 hours. Maha doesn’t recommend different rates for conditioning; but if you use the break-in mode (different from conditioning) it automatically uses 0.1C charge and 0.2C discharge, provided you input the battery capacity correctly.

 

For the fullest charge, leave the batteries in the charger for 2 hours after it says “Done.” It applies a top-off charge of 100 mA for two hours. The top-off current is too low to damage the batteries by overcharging.

[+Chrysalides]

Serious? Below 0.33C is not recommended? I'm surprised. I thought NiMH likes to be recharged at 0.1C.

[+ecanderson]

Serious? Below 0.33C is not recommended? I'm surprised. I thought NiMH likes to be recharged at 0.1C.

Says something (not good) about the charger, actually. The charger has to sense the voltage on the cell during charging, and will watch to see when the voltage starts to DROP (called -dV charging) to make the call on when to stop. Very slow charging doesn't produce a very quick voltage change when charging, and could be mistaken for a bad end charge, and the charge shut down. Slow charging will also produce a more modest -dV at the end that the charger might miss altogether. All of this is because they aren't using a particularly sensitive (enough bits of resolution) analog to digital converter to measure the cell voltage during charge. They figure if they push the cell hard enough, they'll be able to see the voltage moving without missing something.

 

As for the 1/10C charge, you're right that most NiMH prefer something along those lines. However, there are cells being produced with what is evidently a lower internal resistance, and they don't heat up so much at higher charge rates. The manufacturers are all pretty much in agreement that you never want to see the cell reach 45C (or some even advertise 40C) during charging. If a cell is designed such that it presents less resistance to the charge current, it will generate less heat during charge and stay below the "no-no" temperature.

[+Chrysalides]

Says something (not good) about the charger, actually. The charger has to sense the voltage on the cell during charging, and will watch to see when the voltage starts to DROP (called -dV charging) to make the call on when to stop. Very slow charging doesn't produce a very quick voltage change when charging, and could be mistaken for a bad end charge, and the charge shut down. Slow charging will also produce a more modest -dV at the end that the charger might miss altogether. All of this is because they aren't using a particularly sensitive (enough bits of resolution) analog to digital converter to measure the cell voltage during charge. They figure if they push the cell hard enough, they'll be able to see the voltage moving without missing something.

 

As for the 1/10C charge, you're right that most NiMH prefer something along those lines. However, there are cells being produced with what is evidently a lower internal resistance, and they don't heat up so much at higher charge rates. The manufacturers are all pretty much in agreement that you never want to see the cell reach 45C (or some even advertise 40C) during charging. If a cell is designed such that it presents less resistance to the charge current, it will generate less heat during charge and stay below the "no-no" temperature.

Thanks for the info. I've never looked at the C9000 in too much detail. Knowing that, I'm somewhat surprised that it has always been one of the most recommended chargers. I just did a search for the manual of the c9000 and also read the FAQ. It does have a temperature sensor to prevent cells overheating, but I don't know what is the cutoff. Still, it made me glad I chose the LaCrosse BC-9009.

 

To the OP - the manual recommends 0.5C, so you should follow it. If you just plug the batteries in, it will recharge at 1000 mA which should be between 0.33C to 0.5C for all batteries. On the bright side, it should finish charging your batteries much faster than the LaCrosse (5 times faster at default setting).

 

Manual : http://www.mahaenergy.com/download/mhc9000.pdf

 

FAQ : http://www.thomasdistributingshop.com/Maha...Qs_ep_42-1.html

[+Walts Hunting]

I've been using .4 C for my 2700MaH Powerex just fine.

[+ecanderson]

I've been using .4 C for my 2700MaH Powerex just fine.

Those 2700s seem to be an example of a battery that generates pretty minimal heat while being charged fairly aggressively.

 

One of the nice things about the Powerex 2700s, at least at the beginning, is that you have a minimum 2500mAh spec, and most initially perform pretty close to the 2700mAh rating after a few charge/discharge cycles. A few manufacturers play pretty fast and loose with their published rating.

 

Of some interest ... Powerex is dealing in some "1 hour" chargers that are downright scary (see MH-C801D as an example). I'd be very careful what I put into one of these as it will likely toast some other manufacturers' cells at a whopping 2A (optional "soft?!" 1A) charge rate. There are a lot of cells out there that wouldn't tolerate this, even if they've added some temperature sensing to this charger.

[+smstext]

thanks to all those so far who have replied, just now waiting for the postman to deliver my charger.

[+smstext]

an update, got the charger, after doing some refresh/anaylist i was able to weed out a couple of bad batteries.

 

But the question i know have is how much is .3 and .4 if .1 of a 3000mah battery is 300mh does that make .4 1200mh or 720mh? as the manual says never charge lower than .3c or higher than 1.c, now im abit confused.

[+ecanderson]

an update, got the charger, after doing some refresh/anaylist i was able to weed out a couple of bad batteries.

 

But the question i know have is how much is .3 and .4 if .1 of a 3000mah battery is 300mh does that make .4 1200mh or 720mh? as the manual says never charge lower than .3c or higher than 1.c, now im abit confused.

No you're not! You have it right. 0.1C on a 3000mAh would be 300mA. 0.3C on a 3000mAh would be 900mA. 1.0C (yikes!) on a 3000mAh cell would be 3000mA (aka, 3 amps!)

[+EScout]

I use mostly the low self-discharge "Hybrid" type NiMH AAs, and I have the Kodak, Raovac Hybrid, and energyON brands. I usually set them to 700mA charging. Since these cells are rated 2000 or 2100 mAH, that is about 0.33C. I have had the C9000 for several years, and this charging works well.

[+RRLover]

Sooo, . . . When charging, choosing a rate, which rating does one use?

1) Stated capacity of battery packaging, or

2) Actual capacity determined by the charger after the two day break-in.

 

I personally use the determined capacity to choose a rate, not the manufacturer's

stated capacity, as it seems quite optimistic most instances.

 

Norm

[roybassist]

@smstext,

If your batteries are 3000mAH, then 0.33C would be 990 mA. I suggest you charge your batteries at 1000mA. To do that, all you have to do is put your batteries in the C9000 and don’t push any buttons. By default it will charge at 1000mA. Nothing could be easier, and you would be within the charge rate guidelines given by Maha. And if the battery manufacturer exaggerated the capacity, you would almost certainly still be below 0.5C.

[+smstext]

cheers, i was looking at my old charger which charged batteries at 230mah so was a bit worried when i worked out .3 to be 900mah.

 

i have found a set of 2900mah (claimed by manufactor) only to be 1600 and they are less than 6 months old, but do seem to last the longest beating my 2650mah (claimed but are 2400 on charger) by quite a bit.

[+Walts Hunting]

it will recharge at 1000 mA which should be between 0.33C to 0.5C for all batteries

 

You might want to modify that and say it is true for AA batteries. That setting for my AAA's would be 1.25. Might explode them if the temperature sensor failed.

[+smstext]

Another quick question what are the best rechargable batteries for use with this charger and a gps device?

[+Cache Liberation Front]

Though I haven't been using a Maha (I use a Lacrosse, I believe they're comparable), I have so far found the Sanyo Eneloops to work great in my Oregon 450. YMMV.

[+Walts Hunting]

I use both Powerex and Eneloop they both are great.

[+smstext]

What capacity are the eneloops?

[+Dave-Tas]

I am using the IMEDION 2100 in my Dakota 20 and they work well.

[+Curioddity]

What capacity are the eneloops?

The Eneloops are are rated at 2000mAh.

 

At face value that may sound quite inferior to a 2700mAh "standard" NiMH cell, but the standard cells will only be able to deliver that 2700mAh when they're hot off the charger. Let 'em sit for a day or two under ideal conditions and the capacity will be reduced by as much as 20% due to the self-discharge characteristics of standard NiMH cells. I'll add that storing standard NiMH cells in high ambient temperatures like in a parked car with the windows up or even in a dark-colored daypack which is exposed to sunlight will dramatically increase the self-discharge rate.

 

But the self-discharge rate of Eneloops is basically insignificant. I've put my Oregon in my glove box with freshly-charged Eneloops in it and not touched it for a month or more, but it still shows full charge and goes all day when I finally got around to using it again. The same is true for the R/C transmitter I fly my gliders with (a Multiplex Royal Evo-12). I charged it last November, but the weather got chilly and life happened so I never even took it out of it's Pelican Case until last weekend. It was ready to go when I did, though, and I flew planes for hours last Saturday, Sunday, and today with it without fear that I'd ever get a low voltage alarm. And I don't NEED to charge it yet, but I will because there's no reason not to and it's flying season.

 

As for charging cells at 0.1C, that's the suggested norm for constant-current chargers which don't use a peak-detect algorithm (read: wall warts and inexpensive consumer-grade chargers). I've owned dozens of sophisticated programmable multi-chemistry chargers during the years I've been flying R/C and I don't remember a single one which would reliably detect a NiMH or NiCd peak at less than 0.2C. I currently use a pair of Hyperion EOS 0615i DUO3 chargers which cost ~$300 each and they typically won't detect a peak at 0.1C either.

 

NiMH and NiCd cells don't necessarily "like" an 0.1C charge rate any more or less than they "like" a 0.5C rate, but 0.1C is often recommended because it's hard to overcharge cells to the point of damage at that rate. The best rule of thumb is never charge your cells faster than you have to, but charge at at least 0.2-0.3C if you're using a peak detect charger. You also never want to charge over 1.0C unless you consider your cells disposable, and don't let your cells get hot. Warm is OK, but if they get hot then you're doing irreversible damage to the cell chemistry.

 

Oh: And NEVER discharge NiMH cells below 0.9V per cell. That will also do irreversible damage to the cell chemistry. Theres really no practical reason to discharge them below 1V per cell and that's an easy number to remember.

 

I charge my loose AA and AAA NiMH cells (almost all Eneloops) in a Maha MH-C800S in Soft Charging mode. I never have been able to find a specification for the charge rates, but judging by how long it takes to charge 2000mAh Eneloops I'd guess that soft charge equals something like 0.5A or 0.25C. The "regular" charge rate gets cells way too hot for my tastes, so I never use it.

 

I've also never had reason to "condition" eneloop cells. Once or twice a season I'll group 4-8 cells at a time in a "series" battery holder and map a full discharge graph with my West Mountain Radio CBA (Computerized Battery Analyzer) and I have yet to detect any measurable loss of capacity. Some of my cells came from Japan before they were ever available in the United States and have hundreds of charge-discharge cycles on them, and they test as good as my newer cells do.

 

I've NEVER had the same service life with standard NiMH cells.

 

Pete

[+smstext]

and another quick question, how many charges would one expect to get out of a set of rechargables before they become inefficient or at the end of their life?

[+ecanderson]

and another quick question, how many charges would one expect to get out of a set of rechargables before they become inefficient or at the end of their life?

Not something they'll all print, but for the packs we provided for our product, our manufacturers always specified that we should get 2/3 of original capacity at 500 charge cycles.

[+Viajero Perdido]

and another quick question, how many charges would one expect to get out of a set of rechargables before they become inefficient or at the end of their life?

In real-world terms, I've found >2000 geocaches spanning 5 years using 2 1/2 pairs of Energizer 2500s. The 1/2 refers to a pair that died along the way; the other 2 pairs still hold about 2000 mAh per cell according to my charger.

 

I keep waiting for them to kick the bucket so I can switch to low-self-discharge batteries, but they keep refusing to die.

[+smstext]

What capacity are the eneloops?

The Eneloops are are rated at 2000mAh.

 

Oh: And NEVER discharge NiMH cells below 0.9V per cell. That will also do irreversible damage to the cell chemistry. Theres really no practical reason to discharge them below 1V per cell and that's an easy number to remember.

 

 

what will this be in mah? or ?.?c ? sorry for sounding thick, but you dont ask you dont find out.

 

and another quick question, how many charges would one expect to get out of a set of rechargables before they become inefficient or at the end of their life?

In real-world terms, I've found >2000 geocaches spanning 5 years using 2 1/2 pairs of Energizer 2500s. The 1/2 refers to a pair that died along the way; the other 2 pairs still hold about 2000 mAh per cell according to my charger.

 

I keep waiting for them to kick the bucket so I can switch to low-self-discharge batteries, but they keep refusing to die.

 

now seeing these low discharge batteries im waiting for mine to start kicking the bucket so i can have a reason too lol.

[+Curioddity]

what will this be in mah? or ?.?c ? sorry for sounding thick, but you dont ask you dont find out.

NiMH cells have a nominal voltage of 1.2V per cell and they are completely discharged for all practical purposes when that voltage drops below 1V per cell. Below that they can no longer maintain voltage under even the tiniest of loads and the cell chemistry begins to deteriorate in an irreversible way.

 

The mAh rating of a cell is based on it's usable capacity which means a fully-charged 2000mAh cell should be able to deliver 2000mAh of usable energy before the cell voltage drops below that 1V threshold. In the simplest of terms, the mAh (milliamp hour) rating tells you the current in mA (milliamps) that the cell should be able to supply for one hour. In other words, a fully-charged 2000mAh cell should be able to power a 2000mA load for one hour before the cell becomes completely discharged. Likewise, a 1000mAh cell should be able to power a 1000mA load for one hour before it becomes completely discharged.

 

C is a value used to express a rate that you charge or discharge a cell at and it's expressed as a number which is a multiplier and the letter C which means Capacity and equals the mAh rating of the cell. The number you get (when you do the math) is a current load expressed in mA (milliamps). So a 1C load on a 2000mAh cell would be 2000 mA (1 x 2000 = 2000). A 0.5C load on a 2000mAh cell would would be 1000mAh (0.5 x 2000 = 1000).

 

For a real-world example of all this, my Oregon 400t runs for about 8 hours on Eneloop 2000mAh cells before it shuts off. So if we assume that it shuts off when the cell voltage reaches 1V per cell then it draws roughly 250mA when it's on and that's a 0.125C rate of discharge for a 2000mAh cell (0.125 x 2000 = 250) and (2000 / 250 = 8).

 

To continue this example, if I want to recharge these cells at an 0.5C rate I'd charge them at 1000mA (0.5 x 2000 = 1000) and it would take about 2 hours (2000 / 1000 = 2). Likewise if I wanted to charge them at a 0.25C rate I'd charge them at 500mA (0.25 x 2000 = 500) and it would take about 4 hours (2000 / 500 = 4). Of course if it was a dire emergency and I just had to charge those cells FAST I'd charge them at a 1C rate which would be 2000mA (1 x 2000 = 2000) and it would take about 1 hour (2000 / 2000 = 1), but that's not something you want to do to NiMH cells if you want them to last.

 

On a final note, there are 1000mA (milliamps) in 1A (amp). I bring this up because some chargers are set in amps instead of milliamps. The easiest way to convert milliamps to amps is to move the decimal 3 places to the left so 2000mA becomes 2.0A and 500mA becomes 0.5A, etc. Of course that means you can also convert amps to milliamps by moving the decimal 3 places to the right. These exact same rules can be used to convert mAh (milliamp hours) to Ah (amp hours) and back, but it's rare to find consumer electronics batteries rated in Ah.

 

A more detailed explanation goes beyond the scope of what I'm willing to type right now.

 

Pete

Edited June 8, 2010 by Curioddity

[roybassist]

Oh: And NEVER discharge NiMH cells below 0.9V per cell. That will also do irreversible damage to the cell chemistry. Theres really no practical reason to discharge them below 1V per cell and that's an easy number to remember.

what will this be in mah? or ?.?c ? sorry for sounding thick, but you dont ask you dont find out.

The bottom line is, you probably don’t need to worry about this. I believe most GPS receivers will shut themselves down when the voltage reaches about 1V per cell, provided you set the battery type correctly in the receiver. Where you would need to worry about it is in something like a flashlight, where the only thing that shuts it off is you. In that case, just be a bit conservative about how low you run the batteries.

[+Curioddity]

The bottom line is, you probably don’t need to worry about this. I believe most GPS receivers will shut themselves down when the voltage reaches about 1V per cell, provided you set the battery type correctly in the receiver. Where you would need to worry about it is in something like a flashlight, where the only thing that shuts it off is you. In that case, just be a bit conservative about how low you run the batteries.

Unfortunately there are still plenty of people in this world who think NiMH cells suffer from "memory" problems like the old NiCd cells did and they like to deep-discharge them to keep it from happening. The truth of the matter is NiMH cells don't tolerate deep discharges like NiCd cells do and modern NiCd cells don't suffer from voltage depression (the correct terminology) like the early cells did.

 

And the deep-discharge misconception apparently isn't a consumer exclusive. There are commercially available battery charger/cyclers that discharge cells well below the acceptable threshold for NiMH chemistry and the people who are engineering them either don't have a clue or are deliberately trying to encourage new-battery sales.

 

Pete

[+Entropy512]

The bottom line is, you probably don’t need to worry about this. I believe most GPS receivers will shut themselves down when the voltage reaches about 1V per cell, provided you set the battery type correctly in the receiver. Where you would need to worry about it is in something like a flashlight, where the only thing that shuts it off is you. In that case, just be a bit conservative about how low you run the batteries.

Unfortunately there are still plenty of people in this world who think NiMH cells suffer from "memory" problems like the old NiCd cells did and they like to deep-discharge them to keep it from happening. The truth of the matter is NiMH cells don't tolerate deep discharges like NiCd cells do and modern NiCd cells don't suffer from voltage depression (the correct terminology) like the early cells did.

 

And the deep-discharge misconception apparently isn't a consumer exclusive. There are commercially available battery charger/cyclers that discharge cells well below the acceptable threshold for NiMH chemistry and the people who are engineering them either don't have a clue or are deliberately trying to encourage new-battery sales.

 

Pete

I believe that there is indeed a "memory effect" in NiCd cells, but it's actually very small and nearly impossible to reproduce outside of a lab. 99% of the situations that people think are "memory effect" are just overcharging damage due to dumb timed chargers.

[+ecanderson]

I believe that there is indeed a "memory effect" in NiCd cells, but it's actually very small and nearly impossible to reproduce outside of a lab. 99% of the situations that people think are "memory effect" are just overcharging damage due to dumb timed chargers.

I'm assuming you meant NiMH in that sentence?

[Wanthuyr Filho]

Well, perhaps I have a completely different experience with NiMH (ordinary ones) in regard to "memory effect". I have made useless several pairs of batteries in my photo camera (Sony H5) - I think - simply because it doesn't use the whole charge of the batteries, instead, it seems to "turn off" when the voltage gets just a little bit lower than normal - but yet way far from getting "empty". So, just by recharging the batteries again and again after the camera refuses to turn on, after some time these batteries just seem to not hold a charge anymore. Eventually the camera won't even turn on anymore, despite I have tried to charge the batteries or even (strange?!) doing a full "recondition" of the batteries (I also have a couple of intelligent MaHa chargers/analysers). So, in summary, for me it seems that there is indeed a "memory effect" for the NiMH batteries. Now I'm starting a different approach. Everytime a device such as the camera stops due to battery drainage I proceed a full cycle with those batteries (fully discharge then fully recharge). Let's se if it solves the problem.

 

Hugs,

 

WF

[+EScout]

Replying to the last post, some cameras do not like NiMH AAs of any type. Two of mine work well with them, but my latest does not. The NiMHs do not have enough voltage. They only last a few photos. I have to use the CRV3 or lithium AAs, or the R-CRV3. I noticed that some cameras use 4 AAs instead of 2, and I am guessing that they work well with NiMHs.