Hi there, I'm building a battery bank for a DIY camera ring light. The light is:

20 COB LED's 27-30v 300mA each parallel so needing 27-30v and approx 4-6 amps? (note the LED's are mounted on a large aluminium heatsink with thermal paste so there shouldn't be a problem with overheating).

I plan to make a circuit with a switch between two balanced packs of 4s 18650s.

What I have so far:

• LEDs
• Battery holders (optional, tricky to solder in balance cables)
• Balance charger cables
• Low voltage lipo alarm (x2)
• xT60 connectors
• 250w 10A step up voltage regulator
• LED 30v VU meter
• various cable

The plan:

I have a turnigy 6s and have bought a load of batteries. Due to the 6s limitation and the size limitation of the project (to carry), I plan to have two battery packs of 4s 18650s that I can switch between when one runs low:

1. Position One: 1-4s on 5-8s off, lipo alarm on
2. Position Two: All off (I don't want the circuit to run to the lipo alarm here either to avoid draining the batteries over time)
3. Position Three: 1-4s off 5-8s on, lipo alarm on

I need an xt60 connector input on the box to charge 1-4s and 5-8s independently with balance cables that go into my turnigy charger.

Question 1: What would be the easiest way to a) switch between charging the two packs of batteries inside the project box without needing to open and close it and which switch/s should I use to then switch between the battery packs being connected to the voltage step-up circuit (second half of the circuit)? I will need to have whichever pack is being used feeding into my lipo alarm to make sure I know when the batteries need switching over or charging.

The rest of the plan

After the switches the circuit will run into the Voltage step-up/regulator, then out into the LED Vu to be able to safely see the voltage whilst adjusting the light intensity and finally out into an xt60 connector that can have a lead go to the camera ring light.

Question 2: Is it feasible to remove the voltage regulator potentiometers 5k and 10k and replace them with cables to larger pots to put on the project box? That way I can can adjust the brightness easily without opening the box. Any suggestions are welcomed: the codes on the potentiometers are: w103 13 and w502 13.

I'm very new to all this so in the simplest terms possible would be very much appreciated!

 

Why don't you pick the 9v to 12v version. ???

 

Why don't you pick the 9v to 12v version. ???

Version of...?

 

Why don't you pick the 9v to 12v version. ???
Version of...?

This whole thing is way too complex for you.

Forget it.

 

Yes it is. The potentiometers look like multi-turn? The maximum output voltage of the DC-DC converter is 50V. So you could easily over power the led with a single turn mounted on the front panel. I would add a resistor before and after the pot so that way the pots range is limited to what you can adjust (make it idiot proof). You will have to figure your desired range of voltages by using the voltage divider formula and some experimentation.

http://www.allaboutcircuits.com/textbook/direct-current/chpt-6/voltage-divider-circuits/

So am I right in thinking that having two pots on the board at 5k and 10k are to give rough and fine levels of adjustment? I plan to use this with other stuff but none of which I see going over 30v. With my limited knowledge, would making the 10k pot 14k with a couple of fixed resistors prior to it and making the 5k something more like 1k to make the adjustments far smaller and this safer per turn work too?

Thanks in advance, I am reading up on the page you shared with me right now.

 

Could you draw a block diagram and label the name to show what you trying to do then our members have the same target to discuss with.

 

OK here's my best attempt. Does this help?

 

You know without looking at a schematic of the DC-DC converter one could only speculate what is what. If it were me I would try and turn each pot to it's minimum and maximum and observe the relationship it has on the voltage. Then I would do some reverse engineering and make a schematic of the portion of the circuit the multi turn pots are connected to.

I would also suspect that one of the pots is not for fine adjustment (it could be) the reason I think that is so is because a multi turn pot already has a high degree precision.

It looks like you know what you want to do and how you need to go about doing it. I hope everything works out well for you.

I haven't got the regulator through yet but I will take your advice.

I don't have a clue how I'm going to wire the balance leads. Have been looking for a switch but there are two problems: I can't seem to find one with enough inputs and I don't know how I could wire it to go to the lipo alarm. I know what I want but no idea how to wire it all.

 

The problem is balancing packs. I have 7 knackered old laptop batteries 600-1100mah and 8 batteries I bought around 1600-2100mah. With the amount of variation, putting 6 of the 8 new batteries will put around 300mah difference between cells and leave me with 2 cells wasted. Even doing them in series with balance means charging will take forever I'm told. However it would mean I could just solder wires directly to the batteries and avoid trying to figure out something with those fiddly 18650 cases!

 

OK I've decided to use 6 batteries to make life simpler however with my limited knowledge I need some help.

What switch would I use to go between centre off and the 7 balance cables either going to the lipo alarm or the charger as on and on? Is there a switch able to accommodate 14 inputs and 7 outputs and carry potentially 8a current? If I wired the lipo alarm directly to the batteries it will run until the batteries go flat.

 

Guess I will look for a more active/helpful forum for answers.