kakemanx

For those of You that has used Li-polys for a while:

Have e-tec 2cell 7.4v 1200 mha
An apache 2500 charger (autocutoff)

If the packs still contains a good amount of juice left, would it hurt it to charge it anyways? (according to specifications 3.7 v pr. cell)
As i could see on the "manual", it's not going to kill the pack. It says that Li-polys do not
have the "memory" problems..

Also have to say...WOW... got my 2 packs today, along with the charger, em300 motor and heatsinks... it's a different world!!
much, MUCH better lift, more stabil flight, motor runs more "silent/evenly" and of course the longer flighttimes

Could'nt be more happy.. weeeeeeeeee

whstlngdeath

My Feedback: (15)

You can charge them at anytime, whether they are low or not. One thing you don't want to do is to discharge them too low. Also, you don't cycle Li-poly batteries like you might the Ni- based cells.

Jesse

ChopperMike

I'm not familiar with the Apache 2500 charger but with many chargers you have to be careful charging a somewhat discharged Lithium battery. Many of the lithium chargers test the battery to determine how many cells it has. A fully charged 2 cell, for example, could be mis-diagnosed as a discharged 3 cell pack and subsequently be charged to too high a voltage. You need to look into this before charging a battery that is mostly charged. Never let the battery fall below about 3 volts per cell.


Regards,

Mike

whstlngdeath

My Feedback: (15)

That's very true, ChopperMike,
I forgot about auto cell detect. There are some speed controls made for Li-poly's that also use this feature to enable auto voltage cutoff. Put a half-charged battery pack on one of those, and it may read it as something else. FMA makes them, and I no longer use them. I've gone with the Castle Creations Phoenix series. I do have a Apache Li-Po charger, and it uses plug-in jumpers to set both the voltage and the pack's capacity. It forces you to make sure that both are set correctly before you start, making the user the "cell-detector" for this charger.

Jesse

kakemanx

whstlngdeath:
My charger also need to physicaly be set by jumpers... have to set correct voltage AND capasity..
I should be ok then regarding aut oshutoff?
Charges around 45 min until it reaches about 90% full, then another 15-30 min. to top it of..

Is there any danger in stopping the charging at 90 full, and use it?

whstlngdeath

My Feedback: (15)

There is no danger in the charging process to stop early. The danger is in having the battery not reach full charge, and then using it with a speed control that senses voltage to set up the auto cut-off. My advice is to let the battery fully charge every time so you don't run into any surprises.

Jesse

kakemanx

Ok thanks... i guess its a hazell to measure the actuall voltage in each cell (in order to avoid any suprises..)

sledge4055

ok here are my qestions i have a few..

ive seen alot of info on these pacs but i am quite confused ont this issue of the C rateing.. and actual amp draws capable of being extracted from a pac .

take for example the thunder power cells rated at 10 to 12 C how do you determin the amp draw from the c rateing is this 10-12 c, a rateing given for the entire pack or per cell cause ive seen other places where a single cell is rated at this same "C" rateing ,

if i wanted to get more amps out of a pack would i look for a pack with multiple parallel cells in it. does
the amp draw capability change as wel as the Mah or what?

what would i be able to get amp wise if i used the 1320 3s packs and added 2 ,3,4 parallel cells to the pack does the amp draw capability increase as well as the Mah,and how do i do this withouth going more than 11.1or 14.7 v per pack combining them this way this is all con fuseing to me.

baisiclly what im looking to do is use either 1320s or 2100s. but id like to have the capability of getting 30 amps out of a pack because it seems that running a straight 1320 3s pack is not capable of running very long without getting very hot with my setup. himax 2025-4200 with apc 11-7 prop and 4.6 gear ratio

curently i need to use about a 10-6 apc prop to keep the cell from getting to hot however the 11-7 pulls my plane like i want it to but the cells dont seem like they can handle it in fact i know they cant cause i already had one cell in a pack feal like the caseing seperated from the cell in side just barely and i would probably not have noticed it had i not been so diligent in inspecting my packs after each flight .

and i as far as looking for a pack and trying to determin the amp draw from the c rateing is some what missleading

seems to me that a pack capable of a 30+ amp draw would be what i need seeing as how im pretty sure i wont draw more than 20 or 25 amps out of it at any given time it ought not get hot enough to compromise the pack

id like to keep the pack weight under 4 onces if possible

what are my options id hate to spent 70-80 or better dollars a pack and destroy them from thermal overload.

PencilShavings

the "C" rating i believe stand for Coulomb (someone correct me if im wrong)

basically if you have a 1320 milli-amp hour(mah) pack, its 1.32 amp-hours, therefore 1C for that pack is an ouput of 1.32 amps. so a 10C discharge rate would mean drawing 13.2amps from the pack. 20C would be 26.4 amps. all you have to do is multiply the amp-hours of the pack , by the C rating.
adding to that, each cell in a pack has the same rating, mah and voltage, when the cells are in series, the voltage of each cell is added to get the total output voltage of the pack, however the mah rating of the pack is still the same

quote: if i wanted to get more amps out of a pack would i look for a pack with multiple parallel cells in it. does
the amp draw capability change as wel as the Mah or what?

you are correct, to get more amps from a pack, you add more cells in parallel, basically what your doing by adding cells in parallel is adding more capacity (mah) to the pack. if we had a 3s2p 1320 pack..the 3 series cells would give us a voltage of 11.1v, and then the 2 parallel cells would double the capacity of the pack, effictively making it a 2640mah pack. so, when you add parellel cells, it affects the mah rating. that and the C discharge ability determines the amp draw capability

quote: what would i be able to get amp wise if i used the 1320 3s packs and added 2 ,3,4 parallel cells to the pack does the amp draw capability increase as well as the Mah,and how do i do this withouth going more than 11.1or 14.7 v per pack combining them this way this is all con fuseing to me.

if you were to take two 1320 packs, and connect them in parallel, the voltage will not change, it will stay at 11.1v. this will work for 2, 3, 4...pack in parallel

if you were to connect two 3cell 1320 packs in series, the total 'pack' would output the voltage of 6 cells in series(22.2v), and the total capacity would still remain at 1320mah

quote: baisiclly what im looking to do is use either 1320s or 2100s. but id like to have the capability of getting 30 amps out of a pack because it seems that running a straight 1320 3s pack is not capable of running very long without getting very hot with my setup. himax 2025-4200 with apc 11-7 prop and 4.6 gear ratio

i guess your options are 3s2p 1320 pack , 3s 2100 pack, and 3s2p 2100 pack...the 3s2p 1320 is good for 31amps (12C) and the 3s2p 2100 is good for 50amps(12C)...(the tppacks.com site referres to the 3s2p2100 as a 4200pack, since 4200 is the total capacity) the 3 cell 2100 pack would be good for 25 amps.

good job on inspecting your packs, you may have prevented a fire in the plane in the air, or more likely on the charger

soulfly

I'm looking into getting Li-polys for my jabo2.

I've noticed that most of the chargers have a manually selectable mah rating, based on your battery. Is it simply a case of matching the setting on your charger to the one nearest your batteries spec, or does it have to be exactly the same??

For example the Apache 2500 charger can be set to 250,700,1200,1700,2000,2500mA charge rates, but i see batteries with mah ratings such as 830mah. 1050mah, 1570mah etc..

[source - like90 battery selection]

d_wheel

Quote:the "C" rating i believe stand for Coulomb (someone correct me if im wrong)

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Nice try . The C in C rating stands for capacity. 10C means multiply the pack amphour rating by 10.

Later;

D.W.