The battery builders club

[Andy87]

Batteries are dangerous if not treated right. Nobody want to have a fire at home or lose a board due to a wrong battery design.
This thread should be a summary of clean safe battery packs as well as a place where you can come and ask questions all about how best to build your own pack. Feel free to upload pictures in progress and ask our opinion about the layout, weld quality or what ever you not sure is right done or not.

@moon if I remember right you had a punch of pictures from well made pack. Maybe you would like to post some of them?

[moon]

Yeah I’ll upload some, did delete a few but got most of them here

[Zach]

What perfect timing! Im writing a comprehensive “how-to” of battery building As we speak!

[Andy87]

Very much needed here. Looking forward to it!

[ZachTetra]

What do we think about this assembly style? ABS cell holders, 10 awg current carriers, cell > steel > solder > copper joints

Pros:

• Minimal risk of bridging p-packs
• shields underside of battery
• flexible (only when enclosure mounted)
• hella cheap ($20 for 10s4p) (only requires soldering iron)
• replaceable cells
• tested up to 10A

Cons:

• unknown amp capacity (tabs limit to maybe 20ish)
• 37% larger footprint over cells (no wires)
• only single stack

Notes:

• holders can be cut to make a smaller holder
• optimal configurations are 8s and 12s (6s, 7s, and 10s have leads come out an outer corner)
• use 4 slot holders (less cost and footprint per cell)

Procedure:

• buy holders, 10 awg, 22 awg, solder on eBay for $20ish
• wait 2 weeks for shipping
• fold the pins away
• tape holders for convenience
• make an XT90 pigtail (it’s the perfect width for the middle)
• strip sections of the 10 awg to match the tabs
• solder 10 awg to the top of the tabs (heavily tin both sides)*
• add more solder because it never hurts
• all the typical balance lead stuff
• insert your cells of choice
• shrink wrap the whole thing (190mm wide)
• drop it into your enclosure

*Work with the frame sideways so gravity doesn’t pull the solder over the contacts (it’s already a super tight fit)

These are my two battery packs made in this style (10s2p and 12s4p)

[Zach]

This is my planned structure for the guide, am i missing anything? Any input guys?

1. Common terminology and fundamental ideas
   What is Series
   What is Parallel
   Cell Specifications (size, discharge, charge)
   Nominal voltage and charge/discharge practice
   Servicing your battery

2. Is it worth it? Understanding the options
   Risk assessment
   Compression
   Lipo
   NESE
   Prebuilt

3. Planning your pack
   Size and weight
   Discharge
   Layout

4. Ordering cells
   Reputable sellers

5. Sticking your cells together
   Silicone vs Hot glue
   Insulating using Fishpaper and Kapton

6. Spot welding vs Soldering
   PCB’s
   Copper Braid
   Nickel braid

7. Always use (battery) protection
   Discharge vs Charge-only
   Wiring a BMS
   Team spark or team antispark

EDIT: Gonna add balancing wires here (like preventing crossing)

9. Connectors 101
   Genuine vs Knockoff
   What should be used

10. Charging
    Fusing your Charge port
    Charge rate

[ZachTetra]

Maybe water proofing?
And antisparks/loopkeys

[Zach]

Was thinking antisparks and loopkeys would be under conectors 101, but can easily make that under protection.
In terms of waterproofing, what can be done to our packs to make them more waterproof? Liquid electrical tape? MG compounds? Hailing @b264

[ZachTetra]

I believe @hyperion2 makes water resistant batteries by sealing the entire pack in a special shrink wrap and @b264 recommends using MG acrylic conformal coating on the BMS (or at least that’s what he recommended me)

[Andy87]

Looks good. Point 5 I would definitely add the good old plastic cell holder/spacer.

[Grozniy]

And @b264 for loop key build process

[BigBen]

I’m going to dig through and see if I can find a few more.

[Andy87]

The bend over taps for the balance wires are made all in the negative terminal?

[BigBen]

Yes. Otherwise you risk a short?

[Andy87]

Not necessarily, but if to connect them on the positive I would use some fischpaper on the corner as well. As you can see on your pack there is a tinny gap between the terminal fishpaper cover and the fischpaper which goes around the pack. This gap would be connected to the cell negative if the isolation tube gets damaged.

I mean if the balance tap would be over this corner for example

[BigBen]

The balance tab isn’t there though. It’s 5 cells to the left. Same voltage but no risk of a short.

[yelnats8j]

What about cell level fusing?

[BigBen]

Not something I’ve ever used. If anyone has a wealth of info on this then bring it on.

[yelnats8j]

@akhlut @Chaka

They seem to know a lot about it

here is a little on it with PCB’s

akhlut/BATT-PCB

[yelnats8j]

Also one big thing is to always fuse your charge ports.
@b264

If anyone needs a fuse Ill send you 2 free of charge just PM me. ( 8 people Left ) (US Only)
7.5 amps