difference in ni-cd and ni-mh

[flybynighter]

hey everyone, im fairly new to the whole hobby grade rc stuff and have a battery question. i bought a new batery for my wheely king and it was an ni-mh. and asked for a charger at the same time and the charger she gave me said nicd only on it? is this charger safe to use with my new battery or should i get a new charger?

Eddie

[O.C.D.]

NiCad:
Charging

NiCd batteries can charge at several different rates, depending on how the cell was manufactured. The charge rate is measured based on the percentage of the amp-hour capacity the battery is fed as a steady current over the duration of the charge. Regardless of the charge speed, more energy must be supplied to the battery than its actual capacity, to account for energy loss during charging, with faster charges being more efficient. For example, the typical "overnight" charge, called a C/10 charge, is accomplished by applying 10% of the batteries total capacity for a period of 14 hours; that is, a 100Ah battery takes 140Ah of energy to charge at this rate. At the "fast charge" rate, done at 100% of the rated capacity, the battery holds roughly 80% of the charge, so a 100Ah battery takes 120Ah of energy to charge (that is, approximately 1 hour and fifteen minutes) The downside to faster charging is the higher risk of overcharging, which can damage the battery.[3]
The safe temperature range for a NiCd battery in use is between −20°C and 45°C. During charging, the battery temperature typically stays low, around 0°C (the charging reaction absorbs heat), but as the battery nears full charge the temperature will rise to 45–50°C. Some battery chargers detect this temperature increase to cut off charging and prevent over-charging.
When not under load or charge, a NiCd battery will self-discharge approximately 10% per month at 20°C, ranging up to 20% per month at higher temperatures. It is possible to perform a "trickle charge" at current levels just high enough to offset this discharge rate; to keep a battery fully charged. However, if the battery is going to be stored unused for a long period of time, it should be discharged down to at most 40% of capacity (some manufacturers recommend fully discharging, or even short-circuiting), and stored in a cool, dry environment.

[edit] Inspecting

The battery should have no external damage and depending on the number of cells it should have 1.2V per cell when fully charged and about 0.8–1V when discharged .

[edit] Charge condition

High quality NiCd’s have a thermal cut-off so if the battery gets too hot the charger stops. If a NiCd is still warm from discharging and been put on charge, it will not get the full charge possible. In that case, let the battery cool to room temperature then charge. Watch for the correct polarity. Leave charger in a cool place or room temperature when charging to get best results.

[edit] Charging method

A NiCd battery requires a charger with a slightly different voltage charge level than a lead-acid battery, especially if the NiCd has 11 or 12 cells. In addition, the charger requires a more intelligent charge termination method if a fast charger is used. Often NiCd battery packs have a thermal cut-off inside that feeds back to the charger telling it to stop the charging once the battery has heated up and/or a voltage peaking sensing circuit. At room temperature during normal charge conditions the cell voltage increases from an initial 1.2 V to an end-point of about 1.45 V. The rate of rise increases markedly as the cell approaches full charge. The end-point voltage decreases slightly with increasing temperature.



NiMh
Charging


NiMH Charge curve


The charging voltage is in the range of 1.4-1.6 V/cell. A fully charged cell measures 1.35-1.4 V (unloaded), and supplies a nominal average 1.2 V/cell during discharge, down to about 1.0-1.1 V/cell (further discharge may cause permanent damage). In general, a constant-voltage charging method cannot be used for automatic charging. When fast-charging, it is advisable to charge the NiMH batteries with a smart battery charger to avoid overcharging, which can damage batteries and cause dangerous conditions. A Ni-Cad charger should not be used as an automatic substitute for a NiMH charger.

[edit] The delta-V charging method

One of the preferred charging methods is the "delta-V" method, according to Panasonic and other battery manufacturers. This is illustrated in the "NiMH Charge curve" figure. The battery is rapidly charged at constant-current, at a high rate of "1C". After the battery is fully charged, and as it begins to overcharge, the voltage polarity of the electrodes inside the battery will begin to reverse, and this will cause the battery voltage to decrease slightly. A "delta-V" type battery charger will sense this drop in voltage, and when a set threshold is exceeded, the charge cycle must end, and the charge current must be stopped. In some cases, a very small "trickle charge" may remain. The "charge curve" graph also shows that the charge voltage will change depending on the charge current. (Incidentally, it also changes with temperature and battery age.) This generally means that a constant voltage charging method cannot be used automatically, because it will either be unsafe, or it will not charge batteries reliably and consistently. This is unlike a lead-acid battery for example, which can in theory be more easily charged at a suitably chosen constant-voltage.

[edit] The delta-temperature charging method

The delta-temperature method is similar in principle to the delta-V method. Since the charging voltage is nearly constant, if constant current charging is used, then a near constant power is entering the battery. When the battery is charging, most of this power will be converted to chemical energy. However, when the battery is fully charged, most of the charging power will then be converted to heat. This results in an increase in the rate of change of temperature, which can be detected by a sensor measuring the battery temperature. This signal is monitored by the battery charger, which then stops the charging current.

[edit] Manual charging

If a suitable battery charger is not available, constant-voltage or constant-current charging can be done manually, at a moderately high charging rate, if careful attention is given. For proper charging, the voltage and/or current must be set to a suitable charging rate for the particular battery, and a timer should be set. Periodic monitoring is strongly recommended to avoid overcharging (resulting in a voltage drop), or overheating (resulting in an excessive temperature rise and possibly an overpressure condition).

[edit] Trickle charging

Some equipment manufacturers consider that NiMH can be safely charged in simple fixed low-current chargers with or without timers, and that permanent overcharging is permissible with currents up to 'C'/10 h. This may be what happens in some types of cheap cordless phone base stations and the cheapest battery chargers.[citation needed] Although this may be safe when the current is low enough, it decreases the battery capacity and longevity. According to the Panasonic NiMH charging manual (link below), permanent trickle charging (small current overcharging) can cause battery deterioration, and it is the least preferred charging method concerning battery performance. If it is used, the trickle charge rate should be limited to between 0.033×C per hour and 0.05×C per hour for a maximum of 20 hours to avoid damaging the batteries.
For a slow charge, or "trickle charge" process, Duracell recommends "a maintenance charge of indefinite duration at C/300 rate".[3] Some chargers do this after the charge cycle, to offset the natural self-discharge rate of the battery. To maximize battery life, the preferred charge method of NiMH batteries (and most types of batteries), uses low duty cycle pulses of high current rather than continuous low current.

This may help and it may not. In my experiences in the past I used a Cad charger on HiMh's. NiMh retain memory and need to be treated with more care than NiCads. With the wrong charger they can get messed up. I only know what I have done, but I am sure others can say with more efficiency.

[spyderzombie]

flybynight ..............what kind of charger is it and what is the mHa of your batteries and how many cells are there in your battery?

[spyderzombie]

i would say you are safe to charge your bat as long as the charger has a internal volt meter or has connections for a volt meter let me know if your charger has these...........and I will assist you , on how to charge batts

[flybynighter]

well doc j33p thanks for all the info ... unfortunately its alll french to me right, now ill read it through in a bit to try to understand it a little better.

spider zombie: its a cheap 2-3 hour charger says dc output 9v 700Ah, not sure of the brand name (dont have it here with me right now).and the battery is a dreadnaught 3000mah.

i bought it when i first got my truck and got the cheap one cuz im on a budget and didnt want to invest in a good charger cuz i didnt know how much id actually use it. thats all the info i can provide right now..... thanks for anyhelp you can give

[spyderzombie]

yea it looks like you will have to buy a better charger try to find one that has peak detection on it at least like I mentioned with volt meter

[spyderzombie]

I look on the web for you for a charger that wiil work for cheap........ok brb

[spyderzombie]

try these these are just examples.........look for some like these at LhS or check venders

http://www.ckrccrawlers.com/shop/ind...roducts_id=317

http://www.ckrccrawlers.com/shop/ind...products_id=72

http://www.integy.com/cgi-bin/webc.c...692&p_catid=23

you can try a cheap one like these as well
http://www.dynamiterc.com/Products/D...ProdID=DYN4020
http://www.dynamiterc.com/Products/D...ProdID=DYN4010

what you will have to do is plug a volt meter in to the slots and visually watch volts, once volts peak out the batt will start to discharge when the volts drop by .20 battery is fully charged example......... peak is .....10.80V you would stop the charge at 10.60V if this makes since to you


good luck and let me know if you need more assistance

[flybynighter]

thanks for all the help spiderzombie. ill have to look into getting one of these chargers

so when reading the voltmeter manually i would let the charge go to 10.8 and let it drop to 10.6 and disconnect it right?
p.s. the batteries im using are 7.2 volt

[DanTaylor]

FBN I'm gonna make this very easy for you. This is the only charger youll need.

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXCLD5

Its very easy to use and can charge almost anything. it will certainly charge your current battery and wont set back your pocket book. ive found them as low as 30 bucks+ shipping on ebay before and they are well worth it brand new.

[dacaur]

Originally Posted by DanTaylor

FBN I'm gonna make this very easy for you. This is the only charger youll need.

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXCLD5

Its very easy to use and can charge almost anything. it will certainly charge your current battery and wont set back your pocket book. ive found them as low as 30 bucks+ shipping on ebay before and they are well worth it brand new.

Hey if you have this charger, does it show how many Mah you have put into the pack as you charge? im using a triton Jr right now but its DC only.

[Brainstain]

Yes it shows you as it charges. It lets you set all the current ratings, has 10 profiles, is NiCd and NiMh compatible, let's you choose between 1000ish mah and like 4800 or something and is super easy to use if you read the instructions. I have two and I love them.

[spyderzombie]

flybynight the chargers that are listed here or one like these, what you would do is watch the volts on each battery will be different, on the volts you would have to keep an eye on the volts the top voltage # and then let fhem drop down .20........ each battery will have diff. peak depends on quality, new, old etc. ,
I am not saying that you have to buy a charger like these but if you dont have the money to afford a more expensive charger you can get by with one of these

http://www.dynamiterc.com/Products/D...ProdID=DYN4020

http://www.dynamiterc.com/Products/D...ProdID=DYN4020

I dont know about you but I would invest in a desent battery charger
I personly have this charger because it is simple and versatile and I charge cells for nitro glo plugs radio batts and etc.

http://www.integy.com/cgi-bin/webc.c...d=1508&p_catid=

[flybynighter]

hey guys....
thanks for all the help.... any body got any reviews of the charger Dan Taylor mentions... i could spare that much i think.... i think im gonna be using it a fair bit.

[DanTaylor]

FBN I used them when I was racing nitro and had ZERO problems with them. im back into electrics and there are a few guys around my local track that use them as well. Very simple charger does exactly as it says its gonna do and is by far the best bang for your buck charger on the market.

Quick google search and I found these.

http://www.myrcbox.com/review_duratrax_piranha_acdc.htm
http://shop.tinyrc.com/product.php?p...255&bestseller
http://reviews.pricegrabber.com/vehi...ast/m/2773884/
http://www.beatyourtruck.com/prodrev...nacharger.html

If you want to see more simply goto google and type in this duratrax digital piranha review itll show you many more reviews.

[Pooflinger1006]

Im fairly new to the crawling thing but bang for buck i still use that duratrax charger more than any of my other ones, i have one of their intellipulse (I think is what its called), i think it charges a little bit better but doesn't have a screen on it.

If there is one thing i have found out in R/C, Save a little money and buy the better product, it's normally worth it in the long run for quality and function.

[flybynighter]

i think i may go with that charger.... everyone seems to be sayin its a good bang for your buck charger. thanks for all the help guys. its much appreaciated

[DanTaylor]

Originally Posted by flybynighter

i think i may go with that charger.... everyone seems to be sayin its a good bang for your buck charger. thanks for all the help guys. its much appreaciated

You wont regret buying that charger. for what your gonna pay for it there is NO better charger on the market. Good luck with it man.