Charging Two Li-Po Batteries or increasing Voltage of One
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Charging Two Li-Po Batteries or increasing Voltage of One

by bytedisorder on Wed Feb 06, 2013 1:14 am

I was interested in taking either this (2x3.7v 1300mAh):

http://www.adafruit.com/products/258

Or this (1x3.7v 2600mAh):

http://www.adafruit.com/products/328

And charging them using this:

http://www.adafruit.com/products/259

My dillema seems to be that that charge cant handle two cells and having two plugins for charge on a robot is not consumer friendly. On the other hand 3.7v is not enough to drive my project as my arduino wants 7v-12v in and my servos and sensors want 5v out from the arduino.

Power supplies are not my strong point is there a way that I can use the 2600mAh 3.7v to give my project 7v it needs?
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Re: Charging Two Li-Po Batteries or increasing Voltage of One

by bytedisorder on Wed Feb 06, 2013 1:17 am

I think the way to go is the two 1300mAh in series, but will I be able to use one charger?
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Re: Charging Two Li-Po Batteries or increasing Voltage of One

by bytedisorder on Wed Feb 06, 2013 1:25 am

Alright so I guess the answer is to buy a 2 cell pack but is there anywhere that sells a charger for two packs like the one above?
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Re: Charging Two Li-Po Batteries or increasing Voltage of One

by bytedisorder on Wed Feb 06, 2013 4:12 am

I think the solution is (and if this is terriby wrong somebody correct me):

Two 3.7v lithium batteries
Two charge controllers
One Female DC input
One male 1000mA wall plug

Connect each lithium battery to a charge controller, connect the dc in for the charge controllers onto one female DC 9v input (each charge controller gets 4.5v in). Connect the load terminals coming off of the charge controller so the battery output after the charge controller is in series, but not directly so I don't damage the batteries.

Is this a safe configuration?
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Re: Charging Two Li-Po Batteries or increasing Voltage of One

by adafruit_support_bill on Wed Feb 06, 2013 7:34 am

No, because the common power supply ground will prevent you from putting the two charger outputs in series.

For multi-cell series charging solutions, you will probably find more options at a hobby shop specializing in RC supplies. Just be aware that many of the RC packs do not have over-discharge protection circuits.
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Re: Charging Two Li-Po Batteries or increasing Voltage of One

by bytedisorder on Wed Feb 06, 2013 7:50 am

So what would be your solution to give my bot the 7-12v it needs at around an amp with on board charging? I'd like to do business with you guys.
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Re: Charging Two Li-Po Batteries or increasing Voltage of One

by bytedisorder on Wed Feb 06, 2013 8:05 am

What if I add a switch from on the power supply ground so they don't have a common ground?

In other words two switches, one to enable charging and one to enable the arduino. I dont know there has to be a better solution out there for supplying 7-12v with a decent amount of battery to a project without being plugged into the wall.
:D
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Re: Charging Two Li-Po Batteries or increasing Voltage of One

by adafruit_support_bill on Wed Feb 06, 2013 8:11 am

What is commonly done for multi-cell RC charging is to wire a switch to disconnect the batteries from each other so that they can be charged separately. In the other switch position, the cells would be in series, but disconnected from the chargers to prevent a short circuit. This assumes that you don't need to run the bot while you are charging.
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Re: Charging Two Li-Po Batteries or increasing Voltage of One

by bytedisorder on Wed Feb 06, 2013 8:23 pm

What would that require something like a DPDT switch? I'm just trying to figure this all out before I place my order.
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Re: Charging Two Li-Po Batteries or increasing Voltage of One

by bytedisorder on Wed Feb 06, 2013 9:03 pm

1 2 In Series
3 4 To Charger (off)
5 6 Battery connection
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Re: Charging Two Li-Po Batteries or increasing Voltage of One

by franklin97355 on Wed Feb 06, 2013 10:02 pm

Radio controled hobbies routinely use multicell packs and they make chargers that will charge and balance the lipo batteries in a pack. Check out RC battery packs.
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Re: Charging Two Li-Po Batteries or increasing Voltage of One

by bytedisorder on Wed Feb 06, 2013 10:49 pm

Found a charge and batter that will work for this application:

Turnigy nano-tech 1300mah 3S 25~50C Lipo Pack
http://www.hobbyking.com/hobbyking/store/__11903__Turnigy_nano_tech_1300mah_3S_25_50C_Lipo_Pack.html

Balance Charger Battery Charger and Power Supply
http://www.trossenrobotics.com/p/mini-balance-charger.aspx

For anybody out there looking to do a similar setup.
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