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Building your own 14.8V 18000mAh battery


(Etienne Demers) #1

Hello,

Due to shipping restrictions we were not able to purchase the battery from Blue Robotics.

If this is the case for you, do not be alarmed. Building your own is not too difficult.

Here’s your shopping list:

Heat Shrink Tubing: https://www.aliexpress.com/item/Wide-180MM-Diameter-115MM-PVC-2-1-Heat-Shrink-Tubing-Battery-Wrap/32789619207.html?spm=a2g0s.9042311.0.0.ykJ102

Heat resistant tape: https://www.aliexpress.com/item/10mm-X-100Ft-Gold-High-Temperature-Heat-Resistant-Kapton-Tape-Polyimide-BGA-Free-shipping/32780815592.html?spm=a2g0s.9042311.0.0.ykJ102

10AWG silicone wire: https://www.aliexpress.com/item/10AWG-Flexible-Silicone-Wire-RC-Cable-10AWG-1050-0-08TS-Outer-Diameter-5-5mm-5-3mm/32832064351.html?spm=a2g0s.9042311.0.0.dDg5U3

Nickel strips: https://www.aliexpress.com/item/100pcs-lot-0-15mm-x-7mm-x-100mm-Quality-low-resistance-99-96-pure-nickel-Strip/32333149144.html?spm=a2g0s.9042311.0.0.dDg5U3

Eva foam: https://www.aliexpress.com/item/5pcs-lot-50-50cm-2mm-EVA-Foam-Sheet-Handmade-Sponge-Paper-DIY-handcraft-Materials-Multicolour/32366174527.html?spm=a2g0s.9042311.0.0.dDg5U3

Spot Welder: https://www.aliexpress.com/item/Free-shipping-by-DHL-POWER-787A-MCU-Spot-Welder-Battery-Welder-Applicable-Notebook-and-Phone-Battery/32510885967.html?spm=a2g0s.9042311.0.0.dDg5U3

XT90 connectors: https://www.aliexpress.com/item/Original-Amass-10-Pairs-XT30-XT60-XT90-Male-Female-Bullet-Connector-PlugFor-RC-FPV-Lipo-Battery/32774990373.html?spm=a2g0s.9042311.0.0.4YFG8R

JST-XH 4S wire and connector: https://www.lazada.com.ph/set-of-10-30cm-jst-xh-4s-lipo-balance-wire-extension-leads-cables-681849.html

For the batteries, we purchased them from a local vape shop. We couldn’t get the same brand as the ones used in the BR battery but we got an equivalent. The one we got was LG Choco: https://www.mistwoodvape.com/collections/power/products/lg-choco

On top of that, you will need a soldering iron, glue gun and PPE.

Here is the drawing of the battery assembly:

Note that this is a 4S6P whith means that you need to connect 4 banks in series to get to the required voltage (3.7V*4=14.8) and each bank has 6 batteries in parallel to get the required mAh. (3000mAh * 6 = 18000mAh)

Here is the pattern we chose for this project:

Side 1

Side 2

Here are some fabrication pictures and the finished product: (be kind its our first try)

After building this first battery, I found that the shrink wrap we got was a bit too wide, I would recommend a smaller diameter to do a nicer finish.

Note that the fitting inside the 3inch enclosure is tight so you have to keep everything as low profile as possible.

If it’s of any interest, I can put a link of the final procedure and job safety analysis. Let me know.

In conclusion, it would take 3 batteries for us to break even. I would still recommend BR’s battery if you can get it shipped. There are considerable risks involved in making this. Make sure you know what you are doing, never solder directly on the batteries and protect the contacts with electrical tape when you are doing your manipulations.

Cheers,
E.


#2

What is the total cost for this DIY battery?


(Etienne Demers) #3

It cost me about 150USD for 24 batteries

The rest of the material come in bulk and cost me about 140USD

The welding machine cost me about 85USD

So 375USD all in with shipping and enough material to make about 10 batteries (except for the silicone wire)

So lets say 175USD per additional battery

I also bought a 400W charger which is why I mentioned I would break even with 3 batteries. I won’t post the link to this charger as it would compete with BR’s charger which would be a d**k move.


#4

If you are in Europe, they can be shipped from Nido Robotics


(Etienne Demers) #5

Hello all,

I just thought I’d share my experience with the battery packs I made.

The LG Choco turned out to be a very bad choice. Multiple failures if you go over 50% gain.

I am now using Enook 3200mAh batteries which works very well. I have clocked 4 hours with 25% lights on all the time and 25% thrust. Continuously on depth hold or stabilize.

Cheers,
E.


#6

Hi Etienne,

Thanks for sharing this. In my day job we have been producing batteries in a very similar fashion to your technique and, after a couple of fires and a refusal to ship from a major shipping company, we had a major review meeting today to discuss our ongoing battery strategy. I’ll sum it up as follows:

  1. We will no longer build battery packs in-house.
  2. We will lay out a specific set of designs and outsource to pro battery manufacturers.
  3. They will produce the batteries and provide the necessary QA/QC documents along with a Safety Data Sheet (SDS).

From our experience, it is worth noting that if you get a failed cell it can drop its internal resistance and then overload all the other cells in the circuit, this results in a minor fire which gets progressively worse. I can’t share the ugly photos but we were very lucky that nobody was injured.

Furthermore, there are now cells which have internal protection like this one. We are going to be testing them but it’s worth noting that all these cells have guarantees and SDS’s but all those assurances disappear once you start packing them in combined battery packs.

This is where we get into the everlasting argument between Li-Ion and LiPo. I’ve been flying drones with LiPo’s for 8 years and the charger will tell you when it’s time to retire a battery but Li-Ions can get very scary without any warning - just take a look at the e-cigarette videos on Youtube.

After all my research, I am happy to continue with LiPo. This isn’t an empirical decision - it’s just a gut feeling from previous experience.

SROV.


(Etienne Demers) #7

Thanks for Sharing,

I agree that assembling these batteries is a bit risky. The negative pole wraps up all the way around so its easy to short and have a fire for sure.

The choice of batteries is a big factor unfortunately, I am limited to what is available here in the Philippines.

The Enook have not given me any issues to date so hopefully they will prove to last long enough until I get the surface power sorted out.

Cheers,
E


(Lance) #8

It would increase your cost but for a little bit of added security and redundancy you can get a protection board to regulate your batteries and improve their life. For aerial operations where weight is huge factor I could see skipping it, but for dive batteries or any ‘really big juice’ packs I wouldn’t go without… My dive batteries see a lot of abuse and the protection boards have saved me from some very nasty accidents. They’re solid state and can be potted right into your battery unit if your solder connections are good.

edit: Also as others have stated, you want avoid cheap vape or offbrand batteries at all costs, although I get it may be hard to find good batteries in some parts of the world. Cheap Li-Ion batteries are not made to the same standards and are more prone to catastrophic failure. There is a fair bit research on this; NASA did failure tests on a handful of manufacturers, and they send 18650’s into space incidentally. I use Panasonic for 18650.


(James) #9

how would i go about getting a better detailed plans on building this battery?