RC India

RC Equipments => Batteries and Chargers => Topic started by: amir on December 02, 2009, 09:04:53 PM



Title: charging single cell lipo
Post by: amir on December 02, 2009, 09:04:53 PM
hi
how to charge single celled lipos ?
will mobile charger work?
anyone have experience with it ?


Title: Re: charging single cell lipo
Post by: ankur on December 02, 2009, 09:22:17 PM
the idea of charging using mobile charger was proposed by me lol


Title: Re: charging single cell lipo
Post by: amir on December 02, 2009, 09:23:37 PM
yaa..
but i was the first to post
 ;) ;) ;) ;)


Title: Re: charging single cell lipo
Post by: ankur on December 02, 2009, 09:57:36 PM
well folks this topic was put up when we two were talking of 1 cell lipo as i asked him to buy for me

actually i have charged many types of batteries including ni-mh , ni-cd , li-ion [of mobiles] all barely- by just using that charger and they work fine

but i don't know the results of it on lipo


Title: Re: charging single cell lipo
Post by: RotorZone on December 03, 2009, 01:00:56 PM
The mobile chargers usually give out a little over 5V. The actual charger chip is inside your phone. So no, you cannot just plugin a LiPo.

Building a single cell LiPo charger is quite easy if you can do soldering. There are no balancing issues, so the circuit for a current and voltage limited charger is very simple and cheap.


Title: Re: charging single cell lipo
Post by: anwar on December 03, 2009, 01:35:51 PM
Do you have any recommendations for such a circuit with parts that are easily available locally ?


Title: Re: charging single cell lipo
Post by: ankur on December 03, 2009, 01:37:50 PM
i cAN do soldering tell me the circuit


Title: Re: charging single cell lipo
Post by: RotorZone on December 03, 2009, 04:11:19 PM
See page 20 "current limited voltage regulator" and current limited 6V charger on page 22 of LM317 (http://www.national.com/JS/searchDocument.do?textfield=lm317&x=0&y=0) datasheet. Read this datasheet for the details of the regulator IC. You need to set the output voltage to 4.2V and current to 1C value of of your battery.

Adaptation of this circuit with component values for LiPo cells has been popularised by http://shdesigns.org/lionchg.html in RC world. You can pick up the circuit from here if you don't want to do the calculations yourself.

Since you are going to use a mobile charger with about 5V output, there is not enough headroom for dropout voltage of LM317. You could substitute LM2940 (http://www.national.com/JS/searchDocument.do?textfield=lm2940&x=0&y=0) in place of LM317 for your application.


Title: Re: charging single cell lipo
Post by: ankur on December 03, 2009, 04:29:22 PM
any thing simpler than it which requires less things-something simple availble?

and i have a charger that outputs 4.5v at 600mah


Title: Re: charging single cell lipo
Post by: ankur on December 03, 2009, 04:30:24 PM
is that charger ok?


Title: Re: charging single cell lipo
Post by: sushil_anand on December 03, 2009, 04:36:10 PM
Quote
is that charger ok?

No. You will need at least 6V at the rated current (1C) of your LiPo.


Title: Re: charging single cell lipo
Post by: RotorZone on December 03, 2009, 04:51:58 PM
Don't try experiments with LiPo, overcharging can result in fire.

It doesn't really get simpler than the first circuit http://shdesigns.org/pdf/lionchg.pdf. If that is challenging, you have to look at buying.


Title: Re: charging single cell lipo
Post by: ankur on December 03, 2009, 09:40:15 PM
can u tell me where to buy one?


Title: Re: charging single cell lipo
Post by: anwar on December 04, 2009, 11:28:42 AM
No. You will need at least 6V at the rated current (1C) of your LiPo.

Since the mah rating of the lipo was not mentioned, how was this calculation done ?


Title: Re: charging single cell lipo
Post by: ankur on December 04, 2009, 04:23:19 PM
http://www.funnhobby.com/showdetails.aspx?id=1152

is this charger ok


Title: Re: charging single cell lipo
Post by: anwar on December 04, 2009, 04:34:41 PM
The page does not display well, but it says the output is 8v or 12v.  So that would work for two cell or three cell lipos. 

You were after single cell chargers, right ?


Title: Re: charging single cell lipo
Post by: ankur on December 04, 2009, 04:43:02 PM
Quote
is that charger ok?

No. You will need at least 6V at the rated current (1C) of your LiPo.

ya i was over charging 1cell lipo only but read the post above to understand my intentions


Title: Re: charging single cell lipo
Post by: anwar on December 04, 2009, 04:50:04 PM
ya i was over charging 1cell lipo only but read the post above to understand my intentions

Which post ? Anyways, this does not look like a good match for one cell lipo charging.


Title: Re: charging single cell lipo
Post by: ankur on December 04, 2009, 05:27:05 PM
then tell other possibilities other than those given by rotorzone


Title: Re: charging single cell lipo
Post by: anwar on December 04, 2009, 05:29:16 PM
Just curious, what are you guys planning to do with the one cell lipo ?  Almost all routine use of lipos in the RC world happens on two cell lipos or higher, so this is most interesting  :headscratch:


Title: Re: charging single cell lipo
Post by: ankur on December 04, 2009, 05:36:59 PM
TO BE USED ON SMALL PLANES WITH BRUSHED MOTORS THUS MAKING IT VERY CHEAP


Title: Re: charging single cell lipo
Post by: ankur on December 04, 2009, 05:38:58 PM
Well,Anwar bahiya i expected that u used small electric  helis which run on these batteries and thus should be able to answer this question


Title: Re: charging single cell lipo
Post by: anwar on December 04, 2009, 05:48:46 PM
Hmmm..  they are borderline, more like toys  ;)

And they come with their own charger, did you lose yours ? Single cell chargers are harder to find, precisely for the reason I mentioned (they are not common in the RC world). 

For example, if you are willing to pay Rs550 for a charger, why not spend a little more, and get another toy heli or toy plane ?

Of course they are available...

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXWLT6 (expensive)
http://www.rcgroups.com/forums/showthread.php?t=1116487 (some cheap options)

If you absolutely do not want to build your own based on the plan Rajesh posted (which seems to be a widely used option), eBay sounds like your best route.


Title: Re: charging single cell lipo
Post by: ankur on December 04, 2009, 06:22:56 PM
Actually Amir bhaiya has order multiple lipos [single cell] for me-they are of two tpyes with different 'mah'
ask him the 'mah' of the batteries and tell us the charger for them[better if its is 1 or cheap two of them]


Title: Re: charging single cell lipo
Post by: anwar on December 04, 2009, 07:44:54 PM
Rajesh - What would be a best guess on the total cost of building that first circuit you posted using locally available components ?


Title: Re: charging single cell lipo
Post by: RotorZone on December 04, 2009, 09:51:38 PM
It is really cheap, may be about 25Rs or so. Of course a DC power supply - adapter or any other source is extra.


Title: Re: charging single cell lipo
Post by: anwar on December 04, 2009, 11:06:00 PM
Ankur - Aren't you missing out on a great cost opportunity by not soldering it yourself ?  :headscratch:  :o 


Title: Re: charging single cell lipo
Post by: ankur on December 05, 2009, 06:49:03 AM
actually currently i can't  solder since i have broken my hand so can use my left hand only
when it'll recover i'll definitely try it
meanwhile anyother ideas/comments


Title: Re: charging single cell lipo
Post by: Ashta on December 08, 2009, 12:53:16 PM
i cAN do soldering tell me the circuit

To safely charge a LIPO, one has to follow the charging algortham for the LIPO. There are many Lipo charger ICs available which has these built in algoritams implemented thru Timers/ comparators/ temperature sensors etc.
I had made a charger as part of an GPS tracker board, (pl see the photos)few years back, using MAX 1758 IC. I was using this board for some time for my RC purpose till i bought a standard charger.
For another DIY pl see this link. this uses a microchip controller.
http://www.rcgroups.com/forums/showthread.php?t=793441





Title: Re: charging single cell lipo
Post by: sushil_anand on December 08, 2009, 02:42:33 PM
Quote
Since the mah rating of the lipo was not mentioned, how was this calculation done ?

The relevant part was the minimum voltage needed to charge a single cell LiPo since there is a drop across the regulator.  The 1C refers to the current rating of the Lipo. If it is 600 mAH then 1c would be that. If 2,000 MAh then 2A, and so on.


Title: Re: charging single cell lipo
Post by: anwar on December 08, 2009, 04:43:18 PM
So the gist is that at 6V is needed to charge something to 4.2V accounting for the drop on the regulator ? Was the 6V calculated by consulting the datasheet of the regulator, or was it an approximation ?


Title: Re: charging single cell lipo
Post by: ankur on December 20, 2009, 06:01:39 PM
the mah of the batteries are 850 and 138
please tell me the adequate chargers


Title: Re: charging single cell lipo
Post by: sushil_anand on December 21, 2009, 11:31:34 AM
I would suggest a supply with a minimum voltage of 7.5 DC. 

Referring to the circuit, R1 - which is the current limiting resistor - would be 0.75  and 4.7 ohms for 860 and 138 mA. Please note that these resistors will limit the MAXIMUM current. Actual setting of the charge current (within this limit) will be set by R4. You will also need to change R2 to 2700 ohms.

All these refer to the first diagram in the link.


Title: Re: charging single cell lipo
Post by: ankur on December 25, 2009, 10:10:05 PM
I would suggest a supply with a minimum voltage of 7.5 DC. 

Referring to the circuit, R1 - which is the current limiting resistor - would be 0.75  and 4.7 ohms for 860 and 138 mA. Please note that these resistors will limit the MAXIMUM current. Actual setting of the charge current (within this limit) will be set by R4. You will also need to change R2 to 2700 ohms.

All these refer to the first diagram in the link.

setting r1 to the desired values will work for this circuit?
http://shdesigns.org/pdf/lionchg2.pdf

also can diode d1 in the above circuit be replaced with a led[since i have a bunch of them just i need to get that LM317T adj. regulator and 2N2222A NPN trans. i 'll make it


Title: Re: charging single cell lipo
Post by: ankur on December 28, 2009, 11:08:34 PM
am i right?
please answer my question soon as i m not able to make my charger circuit due to these confusions


Title: Re: charging single cell lipo
Post by: RotorZone on December 29, 2009, 12:08:51 AM
No you cannot replace D1 with LED. D1, R6, Q2, R5 and DS1 are for LED indication that charging is going on. If you use other means to monitor the current, for example using a meter, then you can get rid of all these components and put a short in place of D1.


Title: Re: charging single cell lipo
Post by: sushil_anand on January 04, 2010, 04:52:30 PM
Ankur

My apologies for not replying to you earlier. I was out of town for 10 days in locations not too accessible to the net.

Rotorzone is correct. But do note that the "monitor" circuit just tells you that some charging is taking place but not the actual current.


Title: Re: charging single cell lipo
Post by: ankur on January 05, 2010, 01:42:23 PM
ok,thanks for help


Title: Re: charging single cell lipo
Post by: sahilkit on January 05, 2010, 07:13:46 PM
i have built this charge and works fine ! but precautions have to be taken while using the charger !!!

http://www.rcindia.org/batteries-and-chargers/diy-lithium-ion-charger-1-3-cellsselectable-current-for-60-conditions-apply-!/


Title: Re: charging single cell lipo
Post by: ankur on March 06, 2010, 04:03:46 PM
does those loingchgrs stop charging automatically or is it mannual??


Title: Re: charging single cell lipo
Post by: sahilkit on March 06, 2010, 07:10:22 PM
they stop charging automatically and as an indication the led light goes out (meaning battery fully charged n on standby)


Title: Re: charging single cell lipo
Post by: ankur on March 06, 2010, 10:58:10 PM
ok thanx