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Model Forum / Radio Controlled / Helicopters / April 2005batteries
hi guys, just a quick question regarding batteries! i have 2 batteries for my heli, 8.4v 650mah, the other 8.4v 800mah.. what are the difference between these batteries?? does the 800mah actually output more power, or will is basically last longer ?? thanks On 12-03-05 04:52, in article d0ttjh$e3m$1@bigblue.net.au, "jad" <cducme@bigblue.net.au> wrote: snip > i have 2 batteries for my heli, 8.4v 650mah, the other 8.4v 800mah.. > > what are the difference between these batteries?? > > does the 800mah actually output more power, or will is basically last > longer ?? Snap As long as it has the same voltage and the difference is the mAH number it means that it will last longer, it contains more energy. Reidar Otto > On 12-03-05 04:52, in article d0ttjh$e3m$1@bigblue.net.au, "jad" > <cducme@bigblue.net.au> wrote: [quoted text clipped - 10 lines] > means that it will last longer, it contains more energy. > Reidar Otto mind you the extra weight will need more power to lift it and therefore take more current from it, so its not straight forward as a battery twice the capacity will last twice as long Yes thats what I though.. longer mah = longer flight time! Only reason I questioned this is when I was running the 800mah battery in the heli, the Rx literally caught fire!!! thanks guys, jad >>On 12-03-05 04:52, in article d0ttjh$e3m$1@bigblue.net.au, "jad" >><cducme@bigblue.net.au> wrote: [quoted text clipped - 15 lines] > more current from it, so its not straight forward as a battery twice the > capacity will last twice as long sorry to hear that . was it a new battery pack ? Maybe the polarity was wrong . TM > hi guys, > [quoted text clipped - 8 lines] > > thanks >hi guys, > [quoted text clipped - 8 lines] > >thanks In most cases the battery with the highest capacity will only give you longer run time. In some cases though , it will give you more power. If the batteries have a 10c discharge rate the 650 mah will deliver 6.5 amps and the 800 mah will deliver 8 amps. If the motor draws 8 amps then the 650 mah battery will not deliver the power needed. kd > In some cases though , it will give you more power. > If the batteries have a 10c discharge rate the 650 mah will deliver > 6.5 amps and the 800 mah will deliver 8 amps. If the motor draws 8 > amps then the 650 mah battery will not deliver the power needed. But the opposite can also be true, a smaller capacity cell can often deliver more current than a larger capacity one of the same volume as the plates are optimised for current instead of capacity, it's a trade off the designer can make that means the smaller capacity cell can have a lower internal resistance. Greg >But the opposite can also be true, a smaller capacity cell can often deliver >more current than a larger capacity one of the same volume as the plates are [quoted text clipped - 3 lines] > >Greg You're right , internal resistance is what determines, for the most part , the discharge rate , but I did say in MOST cases and I was using a 10C discharge rate as an example for both packs. If a 800 mah pack has a 10C discharge rate , then 8 amps is all you're going to get. The newer packs are getting better and delivering more current , with the biggest improvment being in the LiPoly cells. Some mfrs are claiming 20C discharge rate in their smaller packs in the 350 - 700 mah range. Discharge rate is a very important bit of information when buying a new pack , although sometimes hard to get with the cheaper packs. kd Hi all Sorry if I'm missed something here. Whilst everyone has bee talking about the capacity bit of the battery, could someone explain why the 800mAh battery made the RX catch fire!!! Declan >> In some cases though , it will give you more power. >> If the batteries have a 10c discharge rate the 650 mah will deliver [quoted text clipped - 8 lines] > >Greg Regards Declan Barry Failure of the BEC voltage regulator? Recievers and servos run between 4.8 and 6 volts. If the entire 8.4 volts reached the RX, it would go up in flames (actually, just burn out the components). Leif > Hi all > [quoted text clipped - 20 lines] > > Declan Barry okay.. another one about batteries! do you have to run these batteries (NI-MH) dead flat to avoid the memory problem ?? jad > hi guys, > [quoted text clipped - 8 lines] > > thanks quick answer no they dont suffer that problem it was only NiCads > okay.. another one about batteries! > [quoted text clipped - 15 lines] >> >> thanks >okay.. another one about batteries! > >do you have to run these batteries (NI-MH) dead flat to avoid the memory >problem ?? >jad NO . Even though they were originally advertised as having no memory problems when they were introduced in the early 90's , they do have some memory , although not nearly as much as a NiCd. Just run them completely dead once every 3 months or so and you'll be fine.The rest of the time , just charge them and don't worry about it. NiCd's have both Nickle and Cadmium plates that crystals form on which conceal the active material in the battery from the electrolyte, whereas the NIMH have only nickle plates on which the Crystalline forms.The collection of the crystalline is what causes the memory problem. Cycling the cells prevents the formation of these crystals or reduces the size if they have already formed and restores the full capacity.. Hope this helps kd thanks for that.. much appreciated! when charging, to get a full charge.. is it correct in saying when the batteries are warm to touch, they are fully charged ??? jad >>okay.. another one about batteries! >> [quoted text clipped - 19 lines] > > kd >hanks for that.. much appreciated! > >when charging, to get a full charge.. is it correct in saying when the >batteries are warm to touch, they are fully charged ??? > >jad What kind of batteries are you using ? Nimh , Nicd ? kd >>hanks for that.. much appreciated! >> [quoted text clipped - 6 lines] > > kd got Nimh batteries!! >>>hanks for that.. much appreciated! >>> [quoted text clipped - 8 lines] > >got Nimh batteries!! As Doug said , being warm is not an indication that the batteries are charged , but when they are peaked they will be slightly warm and will get hot if you continue charging. I'm sure you already know this , but be sure to use a charger for Nimh's. Nickel-metal-hydride chargers require more complex electronics than nickel-cadmium systems. To begin with, nickel-metal-hydride produces a very small voltage drop at full charge , much less than Nicd , and a Nicd charger will not sense this.. A nickel-metal-hydride charger must respond to a voltage drop of 8-16mV per cell. Most of today's nickel-metal-hydride chargers use a combination of voltage drop and rate-of-temperature-increase. The charger utilizes whatever comes first to terminate the fast-charge. A Nicd charger will NOT sense the voltage drop and heat and will overcharge and heat the battery. Nimh's are much more sensitive to heat than Nicad so be sure they don't get hot during charging. Hope this helps kd kd1942@aol.com wrote: > As Doug said , being warm is not an indication that the batteries are > charged , but when they are peaked they will be slightly warm and will [quoted text clipped - 14 lines] > Hope this helps > kd Thank you tenishanush9515@duskmail.com | when charging, to get a full charge.. is it correct in saying when the | batteries are warm to touch, they are fully charged ??? No, it's not correct. Well, they might be charged, they might not be. And they might be cold and fully charged. When you charge your batteries, most of the energy gets stored in the chemical reaction, but a small amount gets converted to heat. Once the battery is fully charged, all the power gets converted to heat. So, if you charge at a slow rate, they'll probably stay cool until they're fully charged, then they'll start getting warm if you keep charging. If you charge at a high rate, the batteries will get warm while they're being charged, then they'll start getting hot when they're fully charged if you keep charging. Or they may get hot before they're fully charged if the charge rate is really high. In any event, you should stop charging once it's fully charged -- if you notice it getting warm at a much higher rate, then you're already overcharging the battery too much. This is why a peak charger is important for fast charging.  SignatureDoug McLaren, dougmc@frenzy.com Lead me not into temptation... I can find it myself. |
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