How to wire a balanced Lipo battery pack...

[camracer]

One of my customers suggested I add a tachometer so I found this to throw in the mix. I figure it can tell me when the clutch is slipping as well as give me good rpm data while the gun is firing. I think I will mount it, and the volt meter on the top rail somehow.

http://www.ebay.com/itm/DC-7-30V-Power-Digital-Speedometer-Tachograph-Tachometer-Yellow-LED-Display-/351295189450?hash=item51cad331ca:g:-0YAAOSwEK9TxvBy

Cool idea!

[camracer]

Has anyone tried using the round cell holders that hold three batteries?  I was going to put two of those in a tube.

http://ecx.images-amazon.com/images/I/414UANmUtRL.jpg

http://www.amazon.com/uxcell-Parallel-Connection-Holder-Battery/dp/B00K86S3QE/ref=sr_1_4?s=electronics&ie=UTF8&qid=1451625103&sr=1-4&keywords=battery+holder+for+18650

Do you remember my 5 cell 18650 battery holder I made years back?? Or how about Drozdandconfused's "dynamite stick holder?

[Parellax]

I'm pretty sure each holder would only yield 4.2 volts with the combined capacity of the batteries. I tried to find some round holders that are wired in series. No luck so far.

[Parellax]

You can hot glue the single cell holder to the back of a double cell holder. This will also save some space, and money.

http://www.ebay.com/itm/10-X-Battery-Case-Box-Holder-For-2x-18650-Batteries-Cell-In-Parallel-For-Arduino-/251562892381?hash=item3a92511c5d:g:tR0AAOSwhh5ToWss

http://www.ebay.com/itm/New-Hot-5Pcs-Battery-Case-Box-Holder-for-18650-Li-ion-Batteries-Cell-3-7V-/252091236855?hash=item3ab1cf01f7:g:~h8AAOSw9r1V9pGb

[Parellax]

Here is what you are looking for, but I can't seem to find a source for spares. Note how it is wired in series. You might try contacting the company. This is out of an UltraFire RL-2088 flashlight.

[Parellax]

I ordered a small project box that should hold the volt meter, tac. my current idea is to have a connecting port in the left side of the housing that I can plug the box into when I need to know something. Think of it as a diagnostic tool. I will be able to simply unplug it, and still have full use of the gun with the low voltage alarm functioning, and auxiliary power in the battery compartment.

[camracer]

I'm pretty sure each holder would only yield 4.2 volts with the combined capacity of the batteries. I tried to find some round holders that are wired in series. No luck so far.

Why not just re-wire it?

[Parellax]

Hey Cam. Were you able to somehow use the reverse function of the motor controller. I can't see how it can be wired without reversing polarity to the board. Right now I have the function bypassed, and was thinking of using the dead side of the switch in place of your momentary mag motor switch because I already installed it. Also even when the switch is off the board is still drawing power. There is an LED that will not turn off unless the batteries are disconnected.

[camracer]

Hey Cam. Were you able to somehow use the reverse function of the motor controller. I can't see how it can be wired without reversing polarity to the board. Right now I have the function bypassed, and was thinking of using the dead side of the switch in place of your momentary mag motor switch because I already installed it. Also even when the switch is off the board is still drawing power. There is an LED that will not turn off unless the batteries are disconnected.

The motor controller should only swap polarity on the output, not the input when the forward/reverse switch is switched.
My controller's LED's go out after power is cut. If yours is staying lit, it may be because the circuit board's capacitor is still charged.
Try pulling the trigger after you switch off your gun. That should discharge the capacitor and the controller's LED should go out.
If not, you may have wired the controller incorrectly.

I can help you figure it out.

[Parellax]

Here is a short video about what I have done so far.

https://youtu.be/pEiKZom7B00

[camracer]

First, why do you have six batteries in there?? That will give you over 25v. Sergey's board can handle 24v. At least that is the limit for mine. Did Sergey change something on your newer board??

You do have the motor controller wired wrong. (I'll call it MC for short)
The four post wire connector on the MC should NOT have battery voltage going into it!! That is for connecting the forward/reverse switch. Your switch that came with the MC should have four pins....?? Two of those go to what you labeled post 1 & 2, the others to 3 & 4. I cannot remember if 1 & 2 are forward or reverse or if 3 & 4 are, but it doesn't matter, as a flip of the switch will just switch the motor direction.

First you need to run power wires from your batteries directly to the battery contacts on Sergey's circuit board. Next run wires back from the output side of the power switch on Sergey's board and connect that to the power input on the MC. There is the dual post connector that has the + & - printed next to it on the MC circuit board. This will complete the power circuit so that when you turn on the gun's power switch, it will then and only then power the MC.

Next you need to run wires from the MC's +/- output (this is the other two post wire connector opposite side of the board from the power connection posts) to the female power jack on the gun (where you plug in the magazine's wires). Also, you need to completely disconnect the circuit connection from the female jack on Sergeys board. You will be essentially bypassing Sergey's board and now use the MC to power/control the motor. Just be careful not to blob solder on Sergey's board where it shouldn't go!

Done!

Here are some photos of my set-up showing wiring/battery placement/location for control knob and voltage monitor.
The dark green wires (from old Christmas tree lights) are the outputs to the motor. The thin gray and black wires (kind of hard to see) are power to the MC. The multi-color ribbon wires are for my balancing charger connector (which you cannot see buried under that mess of wires). I suppose I will make an access port on the stock at some point if I feel like it.
You can see that I removed the heat sinks on the MC and carefully bent the chips flatter to the circuit board. put some electrical tape where you need to, if you need to, to prevent a short circuit.

Hope this is clear enough for you to follow!

---Cam

[camracer]

More photos of my connection points:

[Parellax]

I am running six cells because fully charged they measure 24.09 V. I know this is above the capacitors rating of 25 V so I am taking a chance. The 14500's are high drain so they are only above the capacity of the capacitor for a short period of time. Sometimes I let them sit for a few days after I charge them to let them drop to, or below 24 V.

I have my batteries connected to the +, and - terminals on the MC, and the opposite side is running to the Dean's connector hot glued into the stock where it plugs into the back of the frame. I don't have the batteries running directly to the switch connector. I just bypassed one motor direction with a jumper on the four pin connector, and disconnected the unneeded wires from the switch. Because I want to run directly to the board I didn't want to accidentally reverse polarity, and burn up the board.

I took a board, and wired the whole circuit including the mag outside of the stock first, and it worked fine. I can also drop the fully charged voltage of the cells with the MC below the capacitors limit this way. I didn't have any problems until I removed the wires from the unwanted side of the switch. Maybe that somehow grounds the component that got smoking hot. I really don't care about reversing the motor because I have only had one jam over the years, and I still would have had to take the mag apart to get to it.

I am mainly doing this to see what kind of rpm to voltage the motor puts out under different voltages, and psi's. The only halfway suitable tac I could find goes to 9,999 rpm, but maybe I can project a curve from my results. If I am missing something please let me know. Here is the circuit I tested before I wired it in the stock.

[camracer]

When you say, "I didn't want to accidentally reverse polarity, and burn up the board", I assume you are talking about Sergey's board. Sergey's circuit board is protected against accidental reversal of polarity. And, if you connect the MC the way I told you, even if you reversed the motor, it will ONLY affect the motor, not the whole of Sergey's circuit board.

Also, I agree with you about only needing the forward control. The switch is unnecessary. I never use the reverse function.

You said: " I can also drop the fully charged voltage of the cells with the MC below the capacitors limit this way."
Yes, but you are also limiting voltage to the whole of Sergey's board the way you have that configured. What is the point of using five or six batteries if you limit the voltage to the Sergey board? You need that voltage as high as possible for the solenoid, right?

I really suggest you wire it the way I told you to.
Anyway, do what you want, it's fun to experiment.

[Parellax]

This is kind of one of those killing time projects while I wait on the new barrel, and modular components. Sure Sergey's Board has reverse polarity protection, but reversing the polarity will render it inoperable until it is repaired. I really try to stress this with my customers. This happened to the first SB-4K twice, and not by me either although I have done it before.

The point of dropping the voltage to the board while running six 14500's is to initially keep it below 24 V. After the batteries drain down a little it can be ramped back up providing more voltage than five cells can supply. I will need to do some tests to see if the higher voltage is more reliable at 2K.

Either way I am stuck if I can't figure out why the component on the board is overheating. As always I really appreciate the help.