need help on lipo batt...

[eekin]

hi guys...

i started this hobby with nitro planes.. then stopped coz racing 1/10 cars.. then now starting back but going into electrics.. but the problem is, all these motor and batt calculations are making me cuckoo... as i'm more familar with the more direct nitro concept..

so pls bear wit me and help me with the problems im facing. wanna get evrythg right before maidening my plane..

i jus got myself a green rc lipo batt for my jet. the specs are as follows:

2500mah
4s
14.8v

im planning to charge the batt using my previously owned macro power m6 charger tat i got wen in hk. sumthing like the imax b6

i'm aware tat each lipos have their own max threshold of charge rate setting. eg. max charge rate : 2c

correct me if i'm wrong, in evry intelligent charger, u are able to set the charge rate correct??

but in my case, my m6 lipo charge rate settings are in A (amp) example: my m6 can charge lipos at different current charge rate. ranging from 0.1A - 5.0A

so my problem is, how do i convert the "A" values to "C"? and my lipo batt doesnt display the maximum charge rate tat it can take.

so wat do i do now? i dun dare to charge it as afraid of overcharging it. wat is the safe charge rate for lipos in the value term "c". and how do i convert it to "A" amps?? im very confused now..

can somebody pls help me..?

and how do i calculate how long will it take to charge my lipo based on the charge rate setting??


another problem im facing is BEC issue. my jet is rtf. jus plug and play. comes wit a 45a esc. it says here jus need rx and batt to fly. does it means i do not need an external BEC?? to my understanding. the BEC is the component tat powers up the rx am i right??

i also read abt most inbuilt BEC (dat comes with the esc) cannot support polanes with more than 4 servos. is tat true?? my plane has 7 servos. does dat mean i need a BEC?? if so wat kind of BEC do i need to get. my radio tat im using currently is the sanwa rds8000.



one last qn. i thk my tx nicd batt is spoilt as the previous owner din use for quite some time. it gets drained easily. im planning to switch to lipo. are thr ani modifications i need to make so tat my tx can accept the lipo? or is it as easy as resoldering the terminals and get those tx lipo batts tat are easily available off the lhs??



i apologise if my thread is too lengthy. i jus wanna do it right the first time. many of u knw, alot of newbie give up coz of the discouraging results tat lead to crashes, electronics failure, jus coz of setting up the electronics wrongly.

im not new to flying. but new to electric flying. i dun wanna make my first time, a last time. i wanna last long in this hobby. so bear wit me and help me pls..

thx a million...

[Adrianli]

See my reply in red.

hi guys...

i started this hobby with nitro planes.. then stopped coz racing 1/10 cars.. then now starting back but going into electrics.. but the problem is, all these motor and batt calculations are making me cuckoo... as i'm more familar with the more direct nitro concept..

so pls bear wit me and help me with the problems im facing. wanna get evrythg right before maidening my plane..

i jus got myself a green rc lipo batt for my jet. the specs are as follows:

2500mah
4s
14.8v

im planning to charge the batt using my previously owned macro power m6 charger tat i got wen in hk. sumthing like the imax b6

i'm aware tat each lipos have their own max threshold of charge rate setting. eg. max charge rate : 2c

correct me if i'm wrong, in evry intelligent charger, u are able to set the charge rate correct??

but in my case, my m6 lipo charge rate settings are in A (amp) example: my m6 can charge lipos at different current charge rate. ranging from 0.1A - 5.0A

so my problem is, how do i convert the "A" values to "C"? and my lipo batt doesnt display the maximum charge rate tat it can take.

so wat do i do now? i dun dare to charge it as afraid of overcharging it. wat is the safe charge rate for lipos in the value term "c". and how do i convert it to "A" amps?? im very confused now..

can somebody pls help me..?

and how do i calculate how long will it take to charge my lipo based on the charge rate setting??


Set ur charger to 2.5A charging and this is 1C charging. It will take abt an hour or less to charge ur packs depends on the amt of charge left in the pack.




another problem im facing is BEC issue. my jet is rtf. jus plug and play. comes wit a 45a esc. it says here jus need rx and batt to fly. does it means i do not need an external BEC?? to my understanding. the BEC is the component tat powers up the rx am i right??

i also read abt most inbuilt BEC (dat comes with the esc) cannot support polanes with more than 4 servos. is tat true?? my plane has 7 servos. does dat mean i need a BEC?? if so wat kind of BEC do i need to get. my radio tat im using currently is the sanwa rds8000.


Normally, the inbuilt bec in the esc is for abt 1-2amps only. But CC ICE and Jazz esc has inbuilt bec for 5A usage. You have to check the specs of ur esc to determine. On the safe side, since you are operating 7 servos, go with a external BEC with current more than 5A.


one last qn. i thk my tx nicd batt is spoilt as the previous owner din use for quite some time. it gets drained easily. im planning to switch to lipo. are thr ani modifications i need to make so tat my tx can accept the lipo? or is it as easy as resoldering the terminals and get those tx lipo batts tat are easily available off the lhs??


Yes, just solder on a connector and plug in a tx lipo batt will do.



i apologise if my thread is too lengthy. i jus wanna do it right the first time. many of u knw, alot of newbie give up coz of the discouraging results tat lead to crashes, electronics failure, jus coz of setting up the electronics wrongly.

im not new to flying. but new to electric flying. i dun wanna make my first time, a last time. i wanna last long in this hobby. so bear wit me and help me pls..

thx a million...

[eekin]

thx adrian for replying to my post..


so tat means my charger can only charge up to 2c lah?? is this good or bad??
coz some lipos i see they claim can withstand charge current up to 3-5c.
so normally at home a person wud charge the lipo at wat c rating?? and if at the field, they wud usually go at higher c? ( coz wanna charge faster) and wat are the effects of fast charging lipo at high c rating? is it good or bad?

and for my batt which never spec the max charge current it can take, how many c wud u recommend?



and im planning to buy a decent priced and good amp/watt meter so tat i can see how much current a motor wud draw. wat u reccomend i buy and whr??


thx again...

[eekin]

guys... i got myself a bec.. its amp rating is 3a max 5a..
om running 7 mini servos. those 9g servos.. 3a max 5a bec is sufficient for me?? the guy at the store says its good enuff but i he's like not so confident.. he not confident, i lagi not confident.. hahax.. very hardto find a reasonably priced 5-7a bec man.. the one tat i saw is too bulky. then another one needs an external 2s lipo to run.. haiyo..


adrian, u said tat i need a bec of more than 5a. how u calculate tat? and i running 7 of the 9g servos.. 3-5a bec enuff anot?? small servos need lesser power rite?? haha..

[chessgame]

wow. you got lots of questions. suggest you go down to a field to get someone to help you the technicals.

but some quick ones to help you on the way,
1. As long as your ESC is not fried or your battery is drained , you dont nee the bec.

So just take it easy on first few flights. Measure your batter after the first one to see if the voltage on each cell is not below 3.2 (max) .. i usually land with each cell on battery at 3.5-3.7v

2. As for charging, ignore charging above 1c for the moment. charging at 1c means to charg 2.5 A for your 2500mah battery or 1.3A for 1300mah battery etc.

Finally, maybe easier to state what you are flying and what your power setup so people can help you.

[eekin]

wow. you got lots of questions. suggest you go down to a field to get someone to help you the technicals.

but some quick ones to help you on the way,
1. As long as your ESC is not fried or your battery is drained , you dont nee the bec.

So just take it easy on first few flights. Measure your batter after the first one to see if the voltage on each cell is not below 3.2 (max) .. i usually land with each cell on battery at 3.5-3.7v

2. As for charging, ignore charging above 1c for the moment. charging at 1c means to charg 2.5 A for your 2500mah battery or 1.3A for 1300mah battery etc.

Finally, maybe easier to state what you are flying and what your power setup so people can help you.

hi bro chessgame. firstly thks for ur reply..

ya its easier if i jus go down to the field and take some advices.. but the fact is my working schedule is quite irregular. most weekends i do haf work.. and off days are usually weekdays. i always go to jurong flying field but there weekdays nobody flies except kites..

abt the bec, if u read properly, my concern is not abt draining my batt but whether the bec has enough power to power up my 7 9g servos. im not confident of y current set up coz the shop says my 3a max 5a bec is enuff but i gt feedback tat i need more than 5a bec for my set up.. and i got alot of qns coz im new to electrics. gimme a nitro and i can set it up in no time.


so this is my set up...

70mm freewing edf f-16. with 7 9g servos.
2800kv motor.
45a esc. (inbuilt 5v/3a bec)
4s 2200 20c lipo.
hobbywing 3a switchmode ubec. 5v/3a 6v/3a written there 3a max 5a

[misato]

For analog micro servo (9g type), typical max current drawn is 400mA @ 4.8V and 500mA @ 6V,

A good example servo that follows this spec would be hitec HS-65HB

For digital micro servo, typical stall current is 2A @ 4.8V and 3A @ 6V. Idle amp usage would 240mA.

Figures from http://www.servocity.com/html/hitec_servos.html

Base on this typical figure, we can assume that 7 analog 9g servo would draw a peak of 500mA x 7 servo, which comes to around 3.5A when all servo is at stall position, so a 5A BEC/SBEC would be sufficient.

For those digital servo, it would be 2A x 7 which comes to around 14A. Common BEC seldom comes at this output, but there are always those from Castle which gives 10A or 20A for their PRO version SBEC.

In power calculation, the best is to use the max value sum of all the power consuming electronics with a 20% spare capacity. In practical, this would mean costly electronics will be required. Thus you will need to do some logical grouping of the servo. ie in a most/more demand maneuverer, how many servo will be required at a single instance. For example, if you have 4 servo on the aileron of a delta wing setup with no ruder, a tight loop will most likely work all 4 servo to max for a few short second and the other servo like flaps would likely to be not doing anything. Thus it would mean at this instance, 4 x 2A = 8A and with some allowance, a 10A BEC/SBEC would be sufficient.

[misato]

For analog micro servo (9g type), typical max current drawn is 400mA @ 4.8V and 500mA @ 6V,

A good example servo that follows this spec would be hitec HS-65HB

For digital micro servo, typical stall current is 2A @ 4.8V and 3A @ 6V. Idle amp usage would 240mA.

Figures from http://www.servocity.com/html/hitec_servos.html

Base on this typical figure, we can assume that 7 analog 9g servo would draw a peak of 500mA x 7 servo, which comes to around 3.5A when all servo is at stall position, so a 5A BEC/SBEC would be sufficient.

For those digital servo, it would be 2A x 7 which comes to around 14A. Common BEC seldom comes at this output, but there are always those from Castle which gives 10A or 20A for their PRO version SBEC.

In power calculation, the best is to use the max value sum of all the power consuming electronics with a 20% spare capacity. In practical, this would mean costly electronics will be required. Thus you will need to do some logical grouping of the servo. ie in a most/more demand maneuverer, how many servo will be required at a single instance. For example, if you have 4 servo on the aileron of a delta wing setup with no ruder, a tight loop will most likely work all 4 servo to max for a few short second and the other servo like flaps would likely to be not doing anything. Thus it would mean at this instance, 4 x 2A = 8A and with some allowance, a 10A BEC/SBEC would be sufficient.

The example is based on 4 digital servo. If its 4 analog ones, then its 4 x 0.4A which comes to around 1.6A, thus base on assumed usage, a 3A BEC would be plenty.

[eekin]

The example is based on 4 digital servo. If its 4 analog ones, then its 4 x 0.4A which comes to around 1.6A, thus base on assumed usage, a 3A BEC would be plenty.

bro misato,


finally, hahax.. i fully understand the calculation.. hahax.. thk u... salute salute.. all these while i jus understand tat need 3a or 5a bec but i dun relli get it how they come up with tat calculation. abt all these electronics i jus simple dun haf the knowledge. right now i'm like reading up on the internet evryday jus to learn abt the basics and calculation.. now at least i knw my plane can fly alrd.. haha..


thx alot to those hu replied. bro misato, chessgame, and not to forget, bro adrianli. sorry if i bore u guys with such basic qns.. thx.

[zxyong]

From my experience, the current surge when the servo is "stucked", so normally 3A should be sufficient.

[Adrianli]

Aaah, now you mention that they are 9g servo. I was thinking of huge planes using high torque standard servos.

For seven 9g servos, 3A BEC is more than enough.

[chessgame]

My 1cent,

Your 4s 2200mah 20c lipo is likely to bloat. 20c for discharge is a bit on the low side for duct fan. try to go for 30c at least..

2200 mah at 20c means max amp draw from battery is 20x22=44amp.
Your esc is 45 amp so can take it. Usually esc have a amp burst factor which they handle a short high amp burst.

as such 2200 at 30 c will be 66amp. Provided that you dont full throttle all the way but for short 3-5 s then i think your esc may able to handle it.

Try it at static ground level before you do it in the air.

I am one of those who max my cheapo esc so this advise may not be relevant to those who prefer 100% assurance.

so this is my set up...

70mm freewing edf f-16. with 7 9g servos.
2800kv motor.
45a esc. (inbuilt 5v/3a bec)
4s 2200 20c lipo.
hobbywing 3a switchmode ubec. 5v/3a 6v/3a written there 3a max 5a

[trailblazer]

My 1cent,

Your 4s 2200mah 20c lipo is likely to bloat. 20c for discharge is a bit on the low side for duct fan. try to go for 30c at least..

2200 mah at 20c means max amp draw from battery is 20x22=44amp.
Your esc is 45 amp so can take it. Usually esc have a amp burst factor which they handle a short high amp burst.

as such 2200 at 30 c will be 66amp. Provided that you dont full throttle all the way but for short 3-5 s then i think your esc may able to handle it.

Try it at static ground level before you do it in the air.

I am one of those who max my cheapo esc so this advise may not be relevant to those who prefer 100% assurance.

His plane would just... fly.. but that's about all it would do...

[Housefly]

His plane would just... fly.. but that's about all it would do...

Hey bro..

All planes are meant to fly right? What else do you expect your plane to do? Drift or Sail?