From what I gather.....C means capacity? If you're charging nicads or metal hydrides, if the "C" is 1500A or 1.5A, the charge rate should be 10% of 1500=150ma.............if you're charging lipos and the "C" is 1500A or 1.5A, the charge rate should be 1500ma.....is that correct? when someone posts how to charge batteries, I find it troubling if the charge rate is not identified with the particular type of battery they're talking about....there seems to be a whole lot of difference on the charge rates.......2nd question....I think that buying a battery pack that your can monitor/charge each cell is the way to go, seeing as how a single cell can have an effect on the battery, even ruin it by overcharging and all those other ways lipos can go bad..wish I'ld have known that sooner. Please let me know if my thinking is on or OFF......Thanks guys

you got it ,all so the C rating is disgharge 1000ma @10c=10amps 1000ma@20c=20amp draw

C is also used to designate how many cells are in a nimh or nicad pack.

So a 7C 600mah nimh pack would have 7 batteries in it.

For some reason, 'S' is used for Lipos. Not sure why....

As for your second statement, that is the direction lipo's are going. It seems most of them come with a second connector (called taps) which are used to charge the battery. These taps allow the user to charge one cell at a time (or all at the same time if you are using a balancer or multiple chargers) so the pack remains balanced.

When dealing with nimhs or nicads, apparently a slow discharge/charge cycle every now and again will keep those packs balanced.

Pretty general rule of thumb is to charge all batts at a 1C rate. Only small ones need to be less.

The S in lipo batts designates how many "cells" are in series, the P designates if any are paralleled.

To BEAGGS-TIME PILOT and UDUD Thanks a lot guys for answering my inquiries, it makes me understand better and now I know I'm on the right track, but......so much to learn...oh well...you gotta crawl before you can walk...TX again, guys

To the best of my knowledge, the term C should NOT be used to designate how many cells are in a pack. I've seen it used like that by newbies, but it's not correct.

Normally, the number of cells in a NiCd or NiMH pack is designated simply by using the word "cell" as in "I'm running a 7-cell pack."

S stands for "series" as in "cells in series" with regards to LiPoly technology.

Jerry,
Your on the right track! The "one size fits all" approach to chargers is not the way to go with Li-Po's, check out FMA's new cell pro charger and discharge protection module available soon. (at the WRAM show, I hope, I hope) Their system prevents cell imbalance , period. and the DPM warns you when 1 cell approaches cutoff, your ESC can't do that. The only downside to the DPM is it adds a little weight, probably too much for the park flyers, but then their packs don't cost what like in a .40 or .60 glow conversion, or even a 3S 2000Mah pack for my 2M sailplane[8D]
Good Luck,
Pete

Pete....thanks for the info....I will be very careful when charging....making my battery pack to come out of the cowl (for charging ) was a little extra work but now I can charge one pack and fly one, plus the larger space will serve to better cool the battery in flight, can't wait to test hop my Pitts 400 EP ARF, but first, the snow must go away....TX again...Jerry

Guys...I haven't heard, read, or spoke about this particular happening...I don't think it's out of bounds...if it is, then a Moderator will say so and I'll stand corrected.....here's the question.....what the heck happened to what used to be the top in this field of ours.....what happened to RCModeler?...too expensive to put out?...mismanagement?...contributers quit?...I enjoyed that magazine and looked foreward to each issue...am I the only one to miss that magazine?

Lots of good info above but if things are still not totally clear, perhaps this will help.

AMPS, VOLTS, AND THINGS THAT YOU NEED TO KNOW ABOUT THEM!
by Ed Anderson

This note is intended to clear up a few terms and concepts around electricity
as it applies to electric airplanes.


Think of electricity like water. Volts = pressure Amps = flow

Volts is like pounds per square inch, psi. Says nothing about how much water
is flowing, just how hard it is being pushed. You can have 100 psi with zero
water flow.

Amps is flow, like gallons per hour. You can have flow at low pressure and
you can have flow at high pressure.

Amp hours is how much flow can be sustained for how long. It is used as a
way of measuring how much electricity is in the battery. Like how many gallons
of gas in your tank. It is a capacity number. Says nothing about flow or
pressure, it is about capacity.

Amps and mili amps? We are just moving the decimal point around.

1 amp (short for ampere) = 1000 miliamps (mili means 1/1000)

Examples

So a 7 cell NIMH or NICD pack provides 8.4V (pressure).

The motor will draw electricity from the pack at a certain flow rate, or amps.

If you have a have a 650 mili amp hour pack, it can deliver a flow of
.650 amps (650 miliamps) for one hour. If you draw it out faster, it doesn't
last as long. So your motor might pull 6.5 amps for 1/10 of an hour, or about
6 minutes.

A 1100 mah pack has double the capacity of the 650 mah pack, so it should
last "about" twice as long.


What is C in relation to batteries?

C ratings are simply a way of talking about charge and discharge rates for
batteries.

1C, = 1 time the rated mah capacity of the battery. So if you charge your 650
mah pack at 1C, you charge it a 650 miliamps, or .650 amps.

1C on a 1100 pack would be 1.1 amps.

2 C on your 1100 pack would be 2.2 amps

Motor batteries are often rated in Discharge C and charge C.

So a 1100 mah pack (1.1 amp hour) might be rated for 10C discharge, so you can
pull 11 amps ( flow ) without damaging the battery.

Then it might be rated at 2C charge rate (flow), so you charge it at 2.2 amps
(2200 mah)

How did I do? Things clearing up?

If you have a 500 mah pack - any kind - and it is rated at 16C that means it
can deliver 8 amps.

If you have a 1000 mah pack - any kind - and it is rated at 8C that means it
can deliver 8 amps.

If you have a 1000 mah pack - any kind - and it is rated at 12C that means it
can deliver 12 amps

If you have a 1500 mah pack - any kind - and it is rate at 8C that means it
can deliver 12 amps

If you have a 1500 mah pack - any kind - and it is rated at 20 C that means it
can deliver 30 amps.

If you have a 3000 mah pack - any kind - and it is rated at 10 C that means it
can deliver 30 amps.

So, if you need 12 amps you can use a pack with a higher C rating or a pack
with a higher mah rating to get to needed amp deliver level.


One last point. Motor batteries vs receiver batteries

Some batteries can sustain high charge/discharge rates. Others can not.

Those used as transmitter/receiver packs typically are made for low flow/amp
rates while those made for motor packs can sustain higher rates.

So, having a 600 mah pack does not tell you if it is a motor pack that can put
out 6 amps, or if it is a transmitter/receiver pack that would be damaged if
you tried to pull power at 6 amps. It is enough to say that they are
different.

Clearly a motor pack could be used for a transmitter/reciever job, but a
transmitter/reciever pack should not generally be used as a motor pack.

Basics:
http://www.modelaircraft.org/mag/FTGU/Part8/index.html

Lithium Batteries
http://www.*********.org/lithium_bat...eakthrough.htm

New Electric Flyer FAQs
http://www.ezonemag.com/pages/faq/a105.shtml

More than you asked for but maybe wanted to know

BATTERIES AND BATTERY CHARGERS
by Ed Anderson

Let's look at batteries and chargers. Let's just say that you need to use the
right charger for the
right battery. Don't mix and match or you could create a dangerous situation.
Used properly they are all safe to use. If you want to know more about NIMH,
NICD and Lithium batteries, these links contain useful information.

Battery Basics:
http://www.modelaircraft.org/mag/FTGU/Part8/index.html
Notes on Lithium Batteries
http://www.*********.org/lithium_bat...eakthrough.htm
safety warning on Lithium Batteries
http://www.modelaircraft.org/safetycom.asp


Transmitter and Receiver Batteries

These are typically made
from NICD or NIMH cells that are designed for lighter loads than motor
batteries. As such, they need also to be charged at slower rates. The
general rule is 1/10 C charge rate where C is the rated capacity of the
battery. So, on a 600 mah transmitter or receiver pack would be charged at 60
mah. At this rate you would charge an empty pack for 10 hours to bring it
fully up to charge adn in fact you have to charge them a little longer than
that to really get them fully charged, so figure 12 hours to be sure. This is
handled nicely by the charger that comes with the radio system. This is an
example of such a charger.
http://www2.towerhobbies.com/cgi-bin...&I=LXNK66&P=ML

Quick charging these packs is not recommended as a standard practice.
If you quick charge them, they will likely get hot. Don't quick charge them
in the plane or the radio as the heat build up could damage some of the
surrounding electronics or might deform plastic or epoxy based components near
them. Fast charging at 1C will generate a lot of heat and can lead to early
pack failure which could happen during a flight.

There are after market chargers that are focused on transmitter and receiver
packs. Here is an example from AccuCycle
http://www2.towerhobbies.com/cgi-bin...&I=LXL357&P=ML

Charge 'em slow and treat them right and they should last for years. If you
tend to fly for long periods, pick up an extra transmitter and/or receiver
pack and charge them slowly, at home. Here are a couple of examples.
http://www2.towerhobbies.com/cgi-bin...ry&FVPROFIL=++
http://www.amondotech.com/index.asp?...S&Category=228


Motor Packs

The motor on the typical parkflyer needs to pull power at a much higher rate
than a receiver pack can provide. So the batteries that power the motors are
typically of a different design/grade so that they can supply electricity
at these rates. As a result when we charge them we can charge them much
faster too.

The general rule here is that NICD motor packs can be charged in the 1.5 - 3C
range with 2C typical. NIMH packs are best charged at 1- 2C with 1.5C
typical. Higher performance packs can take the higher rates. See what the
maker recommends. This way you can get in your flight, then put the battery
on a charger and be ready to fly that pack again in 15 minutes to an hour.
Have 3-4 packs and 2 field chargers and you may never have to stay on the
ground for more than a few minutes. That's the way I do it.

Lithium motor batteries are becoming popular. However their chemistry is very
different from NICD and NIMH cells. As a result they need a different type of
charging process. If you are using Lithium packs, you MUST use a charger that
is specifically designed to charge lithium or you could end up with an
explosion and/or a fire. This is not joke. Don't ever put a lithium pack on
a charger that is not designed for lithium cells. Typically Lithium packs should not be charged over 1C, but follow the charge rate recommendation of the battery maker carefully!
Video of a lithium battery being overcharged.
http://rc.andersh.com/video/lithiumbattery.wmv

S and P terms

When we talk about battery packs, a designation of XSYP is sometimes used.
This indicates how may cells are in serial and how many groups of these cells
are connected in parallel. While the terms are most common in the Lithium
world, they can just as easily be applied to NIMH or NICD packs.

So a 3S2P pack is made up of 6 cells. There are two groups of 3 cells. The
three cells are connected in series. This is the 3S designation. When
connected in series their voltages add. So 3.7V Lithium cells in a 3S
configuration would have a voltage of 11.1V and be designated as a 3S1P pack.
If these cells were rated at 2000 mah each then this would be a 3S1P 11.1V
2000 mah pack.

Now if we took two of these 3S1P packs and connected them in parallel, the
capacity adds, not the voltage. So this would now be a 3S2P pack rated at
11.1V and having a capacity of 4000 mah. Like connecting two gas tanks
together. The motor in you truck would not be stronger but you could drive
further because you are carrying more fuel.

You could do the same with NICD or NIMH packs. .


Battery Chargers

There are timed chargers and peak chargers. Timed chargers, often bundled
with RTF airplanes, work well if you always run your pack all the way down. If
you have one, use it, but I don't recommend you go out and buy one. Peak
chargers, are the way to go. They read the pack and know when it is fully
charged.

An AC powered charger is convenient to use at home, but won't help you
recharge at the field. All of mine are DC peak chargers except for my radio
chargers. I have a car booster pack that runs my DC equipment in my shop.
And, by the way, I have used it to jump start cars. Works great! This is
similar to the one I have.
http://www.sears.com/sr/javasr/produ...al=AUTO&pid=02 871472000

While many peak chargers are focused on charging motor packs, most also have
low charge rate settings that can be used to charge transmitter/receiver packs
too.

Here are a few examples of peak chargers for your consideration. I have the
first three shown here.

HobbyZone Peak Charger - $19
Simple and inexpensive - I have 2 of these from my Aerobirds I added
different types of connectors so I can use them for all kinds of battery
packs. They work just fine. 4-7 cells NIMH and NICD
http://www.horizonhobby.com/Shop/ByC...ProdID=HBZ1026

Hitec CG-340 - $39 I have had this one for 24 months. This is an older
model. It works well, but there are better choices out there. You need to make
or buy leads Easy to use for NIMH and NICD - up to 16 cells -
http://www.horizonhobby.com/Shop/ByC...rodID=HRC43340

Triton Charger - $130 - This one showed up under the Christmas Tree - :-)
Better than the CG-340. It handles up to 24 cells NICD/NIMH cells or 4 cell
Lithium cell packs as well as Lead/acid field box batteries.
It will also cycle battery packs which my others will not do. So far I am
very happy with it.
http://www2.towerhobbies.com/cgi-bin...&I=LXCJG7&P=ML
Reviews
http://www.rcbatteryclinic.com/triton.htm
http://forums.radiocontrolzone.com/p...d.php?t=135705
http://www.rcuniverse.com/product_gu...product_id=19\


I don't have these but have heard good things about them.

GWS MC 2002 Peak Charger - $49
Seems to be a good value for a first charger for NIMH and NICD packs of 4-12
cells. It has charge meter, but not the digital display or memories of the
Triton or others. Includes a variety of connectors. It can not slow charge
receiver/transmitter packs due to 90 minute charge time cutoff.
http://www2.towerhobbies.com/cgi-bin...?&I=LXHHV3&P=7
http://www.horizonhobby.com/Shop/ByC...ProdID=GWS3000
http://www.gws.com.tw/english/produc...it/charger.htm

Great Planes PolyCharge4 DC Only 4 Output LiPo Charger - $100
http://www2.towerhobbies.com/cgi-bin...?&I=LXKAU0&P=7
If you are seriously into LiPoly ( not Li-ION) This may be the charger of your
dreams. Charges 4 Lipoly packs at one time. Each charge port is limited to
30 watts, so it can charge 1S or 2S packs at up to a 3 amp rate. 3S packs can
be charged at up to about 2.5 amps and 4S packs can be charged at about 2 amp
rate. Therefore, this charger seems a very good choice for 1S or 2S packs up
to 3000 mah capacity, 3S packs up to about 2500 mah and 4S packs of up to
about 2000 mah. You can charge packs of higher capacity but it will take more
than 1 hour to charge based on the typical 1C charge rate for LiPoly packs.

If you have packs with a 2, 3 or 4P designation, this charger might also be
good for you. 3S4P packs up to about 10,000 mah would work well if each 3S
component can be charged separately. 4S4P packs up to about 8000 mah would
also work, if you can charge them as four 4S1P packs of 2000 mah each.
Discussion thread on this charger
http://www.rcgroups.com/forums/showt...4&page=3&pp=15

A review of a group of Lithium battery chargers
http://www.rcgroups.com/links/index.php?id=4676

Sometimes I have 3 chargers running at the field at one time charging motor
batteries for my parkflyers or receiver batteries for my sailplanes. I hate
being grounded. So they are put to good use.

I invite others to provide insights on the subject or to recommend chargers
that have served you well.
__________________
Clear Skies and Safe Flying
Ed Anderson

I'am just wondering to sustain the life and capacity of batteries are you advised to fully de-charge the battery before a full recharge?
i've simply wired a connector on to a halogen bulb the type often seen in kitchens as down lighters and after a flight ive just simply connected the battery and let it de-charge full before whacking it back on the charger is this going to help

flying stock f27 stryker with 9.6V 900mAh Ni-Mh Battery

If you are flying NiCd packs, there is some value ot that. Older NiCds had a problem with develping memory. I hear the newer ones don't have this issue. However I do run mine down once in a while. I use the battery cycler feature of my Triton Charger to safely take them down to .9V per cell. Below that, I am lead to believe may not be good for the cells.

NiMh and Lithiums don't have a memory issue so you really don't need to do this. But about once a year I do cycle my NiMh packs, just for good measure.

No Lithiums would suffer badly from your light method. If you get a Lithium pack below about 2.5V, the pack degrads fast. And, if you get it well below that level, again I am lead to understand that you will seriously damage the pack.

If you have a LVC, low voltage cut-off on your ESC AND you are using a timed charger rather than a peak charger, then I would say running till the LVC cut-off stops the motor is OK for NiCd and NiMh packs.

Hi aeajr,
The problem with deep discharging a Ni-Cd "battery" is that it can result in cell reversal, that's why proper cyclers, like the current Triton and and way back to the old Digipace cut off at about .9V per cell. A single cell can be safely discharged totally, you can put an old glow plug in your Ni-starter and leave it on the bench overnight and not damage the cell (just don't stand it next to a pile of oily rags[X(]). NiCads from way back, like the late 60's probably were prone to "memory", of course back when I was a kid you were told you would get a cramp and drown if you went in the water in less than an hour after eating

In an earlier post Matt Kirsch addressed the issue of the C designation in battery packs, and he was quite right in his response. The only reason I mention it weeks later is that just for grins, check page 9 of the current Tower Talk and see how the copy writers messed up on that one, a 1500mah 3S 8 cell Li-Po, I think not

Pete

I recently pulled all my airplanes and radios out of a 12 year storage. Long story why they got placed into storage, won't go into it here. Anyway, I have a "New in the Box" Futaba Skysport 6 radio that was in my inventory 12 years ago. I have charged and discharged the tx & rx batteries a couple of times, and they seem to be holding a charge OK. Question is..... should I trust these batteries? I bought a new JR 4.8v 1000 mah rx battery, and it appears that my futaba charger for the 500mah pack may not be enough to charge this new battery. Any guidence here would be appreciated. Also wondering if maybe I should just belly up to the bar and get a Triton charger.

FFOURU in Okla

I am probobly going to buy an ELctrifly 1500mAh 3s battery for my plane and i was wondering if that would last for 10 minutes on a BP 21 motor and if they are a good brand...and where can i get Dyamond LiPos

Your 500 mah charger will definately charge your 1000 mah receiver pack. I charge 2000 mah packs with a 500 mah radio charger and it works great. Just takes forever. Your will need about 30-36 hours for the first charge. Depending on how much you run it down I would give it 15-20 hours on the recharge unless you think you have drained it below 4.6v, then I would go the full 30 hours again.

You will be charging at 1/20C so you really can't overcharge it. 48 hours probably would not harm it at all.