Hi.
What is the best practice to connect 7.2V 3000mAh battery to a PCB?
The battery comes with very thick wire.
If I use standard holes in PCB, the battery wires feel too big.
I had designed a PCB with standard 0.1" pitch terminal blocks.
So the holes are pretty close to each other.
Is there al option for me here to safely connect the wires to this PCB?
I tried using a slightly thinner wire and the wires burned as they got heated up too much I think.
ssdesign:
Is there al option for me here to safely connect the wires to this PCB?
That would depend on what the PCB is doing.
If you want good (or even any) answers to a question, always spend a little time explaining what the project is and what it does, the forum does not know.
Do you work for Samsung? Is the 8 going to blow up?
J/K of course, but putting a rechargeable lithium battery on a board without an precise analysis of the current requirement seems like it could lead to 'power supply related problems' in the future.
Sure,
The project is a robot that the kids are building for a school project.
It is using 6 VEX motors. VEX motors require this 7.2 battery to run, thats why using this battery. Its not for Arduino.
The motors are powered by a 7.2v battery and they are controlled using Arduino 101.
101 is connected to an Android app built using MIT app inventor.
The circuit is simple, each Motor has three pins, one goes to Ground, one to Arduino pin and one to battery power.
GND from the battery is also connected to all the GND's from motors which connect to Arduino GND.
What are 'VEX Motors' ?
How much current are the motors expected to pull?
VEX motors are provided by vexrobotics.com
Specifications are here:
Stall current 4.8Amps
Free current 0.37 Amps
ssdesign:
VEX motors are provided by vexrobotics.comSpecifications are here:
https://www.vexrobotics.com/motors.htmlStall current 4.8Amps
Free current 0.37 Amps
So the board needs to cope with 15A or so.
The battery will need to be removeable for charging, I would solder some thick silcone leads to holes in the PCB (with strain relief) and put one of the standard RC type connectors on the wire ends, in the same way as a connector is fitted to a speed controller.
This size of current load is not suitable for most 0.1" style headers and connectors.
You will get some ideas if you Google 'quadcopter power distibution board' and look at the images.
You should use a suitably high-current-rated terminal block for distributing power to your motors and PCB,
certainly not soldering in a LiPo direct to a PCB, that's scary dangerous (a short circuit during soldering
would explode molten solder in your face and maybe set the cells alight).
Use the appropriate matching connector for the pack, add a suitable fuse to protect all the wiring.
12SWG wire soldered to pads on the PCB is the standard way for high current ESC etc. Connect these to an EC3/EC5 or XT plug/socket. Don't used Deans connectors as they are a pain in the arse
--
Mark
ssdesign:
I had designed a PCB with standard 0.1" pitch terminal blocks.
So the holes are pretty close to each other.
Did you make the board at home? What is included on this board,,just connections for the motors?
You could always re-make the board using traces more suited for the application and use screw terminals to attach the battery. Those are .2 spacing, but if you are soldering the wires directly, you could put them as far apart as you want.
Thanks for all the suggestions.
After considering the current load, I have decided not to stall the batteries. Hence I will not be drawing 4.8 current.
Also, the battery is not directly connected to the board, as @srnet mentioned, they need to be removed for charging.
I have a tamiya connector which connects to the PCB and I have now placed the two ends of the connector far apart so that there is no accidental short.
But
I was thinking, inspite ot all safety precautions and now having less current draw, what kind of a battery protection circuit can I use for my battery?
My battery is 7.2V 3000mAh Tenergy battery
This one: https://www.amazon.com/gp/product/B0037U35SO/ref=oh_aui_detailpage_o06_s00?ie=UTF8&psc=1
I would like to know if there are some protection circuits that I can use with this.
ssdesign:
I would like to know if there are some protection circuits that I can use with this.
None you can buy that I can think of. Although when used for the intended application, and RC Car, the speed controller will normally shut off the motor when the battery gets too low, although the rest of the circuit remains powered.
I would not be too concerned about safety issues with NiMh batteries, if the robot is accidently left on, then yes the battery will go flat, which may not do it much good, but it wont become dangerous.
A lithium polymer battery is a completly diffenent issue, let them go flat and they do become dangerous. They can and do explode and violently. Definetly to be avoided for a school project.
srnet:
...
A lithium polymer battery is a completly diffenent issue, let them go flat and they do become dangerous. They can and do explode and violently. Definetly to be avoided for a school project.
Heh. They do indeed! I fired a 100W laser into a dead, bulging lithium battery (in a hood, behind a shield) for a school project. It was spectacular.