RC India

Hello all, I got my wattmeter and i need some help. Kindly tell me what are the different readings and how are they useful? i was testing a turnigy aerodrive 42-60 sk series motor with 6s 4400 mah (two 3s 2200 in parallel), apc 12X6 E prop and 80 amp besc. the readings are something as in pic below. how do i calculate thrust to weight ratio? and what about other readings. thx

(http://img534.imageshack.us/img534/6590/hk0101.th.jpg) (http://img534.imageshack.us/i/hk0101.jpg/)

how much did this thing cost

20$

in rs after reaching inida
including customs and shipping

1st of all, two 3s 2200 in parallel does not make 6s 4400!!!!
it will be stilll 3s and 4400!!!! means in parallel ur voltage will be only 11.1 v but with 4400

but in series it will be 6s but 2200!!!! means ur voltage will be 22.2v but at 2200

In that case its series cuz wattmeter shows over 23 volt. BTW I am new to electric setup so i would like to know some things first. kindly clarify, does this mean I can use any combination of batteries like (one 3s 2200mah and other 2s 1300mah) or (one 3s 2200mah and other 3s 1300mah)? In second combination cells are 3 but diff mah, does it matter? i am using this thing to connect the batteies

(http://img6.imageshack.us/img6/188/601bx601a2ps.th.jpg) (http://img6.imageshack.us/i/601bx601a2ps.jpg/)
 

Rs1500 approx

also what is better series or parallel?

Dear,
Making Parallel, Ampear Hour gets added but both voltage remain same and the load sharing (Load Current here) is totally depend upon inversely proportional to the battery internal impedance (Resistance) ratio. Therefore, you can use different AH cells in parallel just checking that both EMFs are same so that circulating current not flow.

In series, as the load current are same that flow through the cell, the ampear hour capacity should be same. and more than that, battery status (Charging/Discharging should be maintained. As, the current pass through the both and time required are to be same, you have to use same AH Capacity otherwise, the series pack capacity will be maintained by the minimum one. Here you can mix different cell voltage pack as they connected in series.

In different pack (Specially in NiMH / NiCd) whild discharged, you check the different cell voltage and you can find the lowest voltage is the weakest one. Just connect a small load during measure so that source drop occure. Now just charge the single (or if required two) so that all cell discharge voltage should be same order. Then check the performance of the pack. Surprisingly you can get better capacity from the pack again.
This you can also do by charging individually with slow charging and checking voltage so that each cell got full charged and you can get same result.
===============================================================
This is because, though all cell in pack are same, but not truely same. Their internal trickle discharge rate are minor differ from each other. Initially all are fully charged. Now let after discharge (One flight) one cell voltage (on load) got down means fully discharged and others let with some charge. Now while charging, the other cells got charged earlier than the weakest one and some charge difference will occure. This will be adding with time and your cell pack efficiency drops with time. So, you need to scale all cell at least after 1000 Cycle I recomend.

Thanks.

A lipo can last 1000 Cycles?  :headscratch:

CP, if you put 2 3S in parallel then your cells will become 3s 4400 mah and not 6s 4400 mah.

Here is what you should see:

Current:
1)Your 2200 batteries 20c in parallel can give you a maximum of 88 amps, but you should not draw more than 70 amps from it. Good for your batteries.
2)Your motor should not consume more than 70 amps with the prop.

Put your watt meter between the motor and batteries and chek to see if the amps are not more, amps indicated by A on your meter. Slowly increase throttle and see readings. Also make sure your ESC is getting good air flow. Check the temperature periodically.

Voltage:
It also shows how much the voltage drops when load increases.

WATTS:
It shows voltage x amps

AH:
It shows how much mah the motor has consumed from your battery since you started the experiment.

Connect watt meter properly. Connecting the battery to watt meter where you are supposed to connect motor will burn it.

You would need a spring balance setup etc to calculate thrust to weight ratio. Cant do that with a watt meter. You can see the trust by visiting hobbycity and reading user reviews for respective props.


Aaal da best!

http://www.youtube.com/watch?v=tHxM2QngCw8