I'm getting close to finishing the electronics for lighting my model and trying to work out how to actually power it. Most of the components use 5v, but one of the LED strips (about 12 little smd leds on the strip) uses 12V at about 177mA current draw. So I need something that can handle 12V and supply about 2300mA when everything is running (sound effects and lights).
I'd prefer something in the model itself so I don't have to have wires running to it all the time. Looked at disposable batteries, but that's a hassle for removing them and replacing them. So I looked into a DIY rechargeable battery pack, but I'm a little nervous about getting that correct, from what I've read it's harder than it looks and if things go wrong then I end up with a melted model :(.
So I got a TalentCell 12V 3A battery pack, it's got all the electronics built into it, so all I'd need to do is maybe resolder some things after I reposition the parts for better placement in the mode. It opens up easily and the battery pack part appears to come out, it's just held in place with adhesive. I'd like to take it apart to be able to place it more effectively in the model and then move the on/off switch and so on to more effective places in the model. Has anyone done something like this? Any advice before I blow myself up (ha, ha!)?
Are you sure? I do not know your skill set or resources, be sure you make no mistooks and have the proper protection gear on and a good fire extinguisher handy.
Well I'm new to this kind of thing, and i've done some simple circuits for this project. But never dealt with modding a power supply. Here's what I'm thinking. Here's the battery pack:
What I was thinking was to disconnect it from the case and place it here
or possibly here:
in the yellow outlines. Alternately if I could separate the cells that would be even better so I could place in different places in the model (purple outlines).
Does this make any sense?
You will see that on top of the cells is some electronics. One of the functions of the electronics is to properly manage the charging and discharging of the cells in the battery so they are safe. Lithium batteries a great for starting fires if you don't treat them very carefully.
My concern with what you are doing is that you inadvertently remove or reduce the protection the cells currently have and end up with your project going up in smoke.
So, the cells might well fit in the spaces you suggest, but you have to be very careful about retaining the electronics, properly connected and working. If it were me I'd find a space where everything can fit without taking it apart.
Oh! It would be interesting to see the model, preferably all lit up
@anon15785262 Please refrain from opening the battery pack and use the cell pack in your model. You mentioned you don't have prior experience in handling Lithium chemistry cells/packs. They need battery management system to ensure the cells operate in safe operating region. The BMS(the green pcb on top of cellpack) is calibrated for cell-pack connections(voltage sag between interconnections) so don't separate cells in the pack!
If you have no other option but to use the lithium chemistry cells, then go for a pack whose cells are made of Lithium Iron Phosphate chemistry, they very less prone to thermal runaway.
!!Stay away from Lithium Cobalt chemistries NMC/NCA !!
There is sufficient literature for self learning on Lithium cells in Learn About Batteries - Battery University
Spend time, fastest way to success is slowness.
Not mine, some one else's quote.
Use good PP safety gear while working with these.
Thanks,
Sarath.
OK so I did some more research yesterday and ordered a BMS circuit (https://www.amazon.com/Comidox-Protection-Anti-Overcharge-Over-Discharge-Over-Current/dp/B07J9NXQ6W) and single cell battery case holders. From what I've been reading I can't see any reason not to wire them in such a way that I can place them in different zone (see the purple outlines in the above picture). Plus using the holders I don't need to solder anything directly to the battery at all, so that should be much safer.
I'll keep this pack and use it for something else (there's a Millenium Falcon that's going to need help soon).
I should mention that I also ordered 3 individual samsung 18650 batteries as well, so I'll be building my own setup here.
I can't comment on that particular BMS but in principal what you propose is reasonable.
Just remember that if using three separate battery modules, you then need a completely separate charger power supply for each of the three.
And you risk the batteries having different charge states, meaning that one may shut down before the others and be subjected to reverse voltage as a consequence.
OK. That's not my plan, I intend to connect the batteries together in serial, but instead of wired right next to each other, use longer wires (maybe 3-4 inches max) between them so I can put them in different positions to use space better.
So you are going to use the same single charge controller specifically designed to use with the three cells together?
OK I made the potentially stupid assumption that " Comidox 3S 12V 10A" means that each circuit piece is set up to handle 3 in series baterries? Was I wrong? I was under the impression that 1 BMS circuit handled 3 batteries? Yes, the plan is to use the batteries together.
Maybe I am mis-reading but I think @anon15785262 is going to use the cells physically separated but electrically in series, so 'together' in that sense. Assuming the chosen charge controller is designed for 3 cells in series and is connected correctly I don't see an issue with this.
Terminology
It has become common usage to refer to a single cell as a 'battery'. A single cell is not a battery, a battery is 2 or more cells wired together in some way.
On top of the battery pack from post#3 is a charge control unit. After the battery pack has been fully charged what is the voltage at the output of the charge control unit?
The charge control unit is connected to 3 batteries, meaning the charge control unit can be a 3S or a 3P. Learning which type of charge control unit you have will go towards being able to use the battery pack.
I'd use the charge control units batteries and charge controller over 3 separate batteries and a DYI. The reason is, let me ask. Are you familiar with how to solder a Li battery to a metal tab without destroying or damaging the Li battery?
Me I put the batteries in a battery holder and wire the holder to either a S or P configuration. In this case space is tight. Those batteries from the case are already soldered to metal tabs by a robot designed to solder metal tabs to a Li battery.
Most likely you will just use the batteries and the charge control unit. The electronics still attached to the case is to be discarded.
After letting us know what the V's are of the charge control units' output, not the battery packs output V's, then we may be able to help you out with connecting the battery pack to your project.
Yes that's exactly the plan. Going on the label the controller is being sold under (i.e. "Comidox 3S 12V 10A" ), I'm assuming it's ok for 3 cells in series.
the voltage is 12.66 according to my meter. So that would mean it's in series. The cells are connected with tabs like you mentioned so I'm not even going to attempt to separate them, it's not worth the hassle. As I mentioned, I ordered 3 cells already, and I have individual cell holders and a 3S BMS controller
So the goal is to wire these up in series and then hook them up to the controller.
Aren't those wires a bit thin to handle 10A?
It looks more like a power supply of an alarm clock...
Probably, but I'm not going to be sending 10A through them. The max is 2300mA, and possibly lower, maybe 1900mA.
Hi @anon15785262,
The circuit which you ordered is for Lithium Iron Phosphate chemistry.
The Samsung 18650 cells which you ordered are based on cobalt chemistry,
they are either NMC or NCA.
The operating voltage range of Lithium Iron Phosphate is 2.5 volts to 3.65 volts.
For Cobalt based lithium cells the operating voltage range is 2.5 volts to 4.2 volts.
The charge and discharge behaviors of NMC/NCA lithium cells and LiFepo4 lithium cells are quite different.
You also need to look into the following( i missed to mention those)
- How much heat is expected inside the enclosure in a worst day?
- What is the operating temperature range of the lithium cells?
- Below 0 degree centigrade if you charge the cells, they are guaranteed to loose capacity! have you considered it.
- What is the acceptable continuous C-Rate of the lithium cells? (this parameter is important.
The risk is very high as you are new.
I would strongly recommend to start with LiFepo4 cells and not MC/NCA/NCM.
Use good PP safety gear while working with these. Be Safe