DIY Battery Handbook Initiative

upnorthandpersonal

Administrator
Considering the amount of users this site is seeing and the amount of people that are embarking on building their own battery (and the repeating issues we see), we thought it would be a good idea to compose a clear and concise recommended (best practices) document. This document would explicitly use the 'lessons learned' from others that ran into problems, and draw from the root causes of those problems.

There are going to be various topics like : top balancing, compression, matching and environmental controls, fuses, etc. but the context will be pretty well constrained and so it should not be that 'controversial'.

In the next few posts, let's see if we can find out if there is enough interest in such a document. We would then start out with an outline and guidelines as this will result in much less work later on and make the document more cohesive in general. We suggest that the final document will live in the Wiki and have its own section there.

Again, the goal is not to become a huge document with all sorts of nuances, but a general best practices that is clear, concise and easy to digest for those new to the game.

Thanks to @Posplayr for getting the ball rolling!
 

Rednecktek

Solar Addict
As someone terrified of burning up $BigMoneyMoney trying to make his own batteries, please make sure that the Step-By-Step sections are subdivided into categories such as "Expert", "Advanced" and "Complete N00B".

Layman friendly explanations are always appreciated, I still can't wrap my head around how a BMS is supposed to work and why one would charge individual cells before building a battery and then just charging them up as a unit.

Complete Noob, maybe less. :)
 

upnorthandpersonal

Administrator
please make sure that the Step-By-Step sections are subdivided into categories such as "Expert", "Advanced" and "Complete N00B".

The goal is not to have those sections/categories at all. The idea is that the best practices are documented in such a way that they are clear, and there there are no 'advanced' aspects that can only be done for people with more experience. For example, best practices might describe where to put the Class-T fuse and its rating. It doesn't go into discussing/arguing for/against/alternatives to Class-T fuses. Class-T fuses are the best practice, so those are in the document.
 

upnorthandpersonal

Administrator
I still can't wrap my head around how a BMS is supposed to work and why one would charge individual cells before building a battery and then just charging them up as a unit.

Those would be very clearly presented in topics such as 'top balancing'. We know this information is spread out all over the place and there are multiple ways to do this, etc. The document would give the one that is considered safest (safety would be a primary focus in general) and will not go into nuances.
 

toms

Solar Addict
Great idea, from a forum that almost universally recommends connecting a charger to a cell without using a high voltage disconnect - i think you’ll struggle to get a consensus on “best practice” with safety as a priority.
 

Short_Shot

Photon Sorcerer
A single page document with wiki links to each aspect would suffice, would it not?

You can walk through the process step by step, starting with a short glossary (explaining the difference between cell, pack/battery, and banks of batteries) and a reference to doing an energy audit to identify necessary capacity.

Then a link to series vs parallel.
And a link to ohms law stuff and the difference between amp or watt and amp/watt-hours.

A short description of what's needed and why followed by a link, such as:

Step X: Balance each cell in each battery.

A group of cells placed into a battery pack should be balanced one way or another. The two options are top and bottom balancing and there are competing theories on which is better and when to do so.

Most commonly, top balancing is done.

Read up on top balancing (link).
Read up on bottom balancing (link).

This is done to ensure each cell behaves in a predictable fashion even when they are not perfectly matched.

Whichever is chosen, be sure you understand why and that it's done properly.

Step Y: And so on.
 

Short_Shot

Photon Sorcerer
Great idea, from a forum that almost universally recommends connecting a charger to a cell without using a high voltage disconnect - i think you’ll struggle to get a consensus on “best practice” with safety as a priority.
Let us know when you find a cheap 3.65 volt disconnect for parallel balancing and we will probably be able to talk @Will Prowse into doing a video and recommending it or not.

Personally, I believe this issue is solved by setting your power supply properly in the first place.
 

DJSmiley

Solar Addict
And you might include something like 'common made mistakes' (with urgent suggestion to read also)

There continues to be a stream of people
- Connecting power supply, adjusting to 3.65V after connecting, and finding out their cells are overcharged -> Adjust PSU fist
- Using crappy cables, usually the ones provided with a cheap current supply -> Use proper cables and lugs
- Overtorquing threads, damaging them -> how to fix
- Cell inbalance due to bad connections and crimps -> sand, properly clean, and how to make / examples of proper lug crimps
 

mrzed001

Voice of reason
Yep. This is why we needed the Up in smoke section.
To see what mistakes users made.
To be able to collect them and make advices against them.

There is the Wiki, the FAQ ... and not really organized and user friendly.
I suggested a tree/hierarchy structure for there like (just a stupid list):

Battery
- DiY from Cells
- - Before buying Cells
- - Cell buying options
- - Before building a pack
- - - Cell identify
- - - Cell testing
- - - Cell top balance (not optional)
- - Building a pack
- - - Cell placement/cabinet
- - - Cell separation
- - - Cell compression
- - - Cell order series and parallel
- - - Busbar options and todo when connecting the cells
- - - - Seller given nickel plated copper
- - - - User made flexible cable
- - - - Aluminium busbars
- Manufactured like 12V battery
- - Battery buying options
- - Battery pack build
- - - Battery placement
- - - Battery order series and parallel
- - - Battery connectors, cables

BMS (not optional)
- Types
- - FET based
- - Relay based
- Balance types
- - passive balance
- - active balance
- Before buying a BMS
- Buying options
- BMS to battery build
- - BMS placement
- - BMS cable order
- - BMS cable management
- How to start the BMS
- How to monitor the BMS
- BMS connections like RS485

Where you can open categories and select possibilities like battery is DIY (from cells) or 12V battery, and if DIY then there is the what to do list (for building it) like before buying what to do, how to order, how to top balance ...

A step-by-step handbook is a good idea too. But I am afraid that every system is unique. Like some start from cells, some from 12V battery. Different connections, different protections (no BMS, but balancer), .... different build and build problems.
 

Short_Shot

Photon Sorcerer
Yep. This is why we needed the Up in smoke section.
To see what mistakes users made.
To be able to collect them and make advices against them.

There is the Wiki, the FAQ ... and not really organized and user friendly.
I suggested a tree/hierarchy structure for there like (just a stupid list):

Battery
- DiY from Cells
- - Before buying Cells
- - Cell buying options
- - Before building a pack
- - - Cell identify
- - - Cell testing
- - - Cell top balance (not optional)
- - Building a pack
- - - Cell placement/cabinet
- - - Cell separation
- - - Cell compression
- - - Cell order series and parallel
- - - Busbar options and todo when connecting the cells
- - - - Seller given nickel plated copper
- - - - User made flexible cable
- - - - Aluminium busbars
- Manufactured like 12V battery
- - Battery buying options
- - Battery pack build
- - - Battery placement
- - - Battery order series and parallel
- - - Battery connectors, cables

BMS (not optional)
- Types
- - FET based
- - Relay based
- Balance types
- - passive balance
- - active balance
- Before buying a BMS
- Buying options
- BMS to battery build
- - BMS placement
- - BMS cable order
- - BMS cable management
- How to start the BMS
- How to monitor the BMS
- BMS connections like RS485

Where you can open categories and select possibilities like battery is DIY (from cells) or 12V battery, and if DIY then there is the what to do list (for building it) like before buying what to do, how to order, how to top balance ...

A step-by-step handbook is a good idea too. But I am afraid that every system is unique. Like some start from cells, some from 12V battery. Different connections, different protections (no BMS, but balancer), .... different build and build problems.
Yeah but this post was specific to a DIY pack.
 

DerpsyDoodler

Photon Sorcerer
Yep. This is why we needed the Up in smoke section.
To see what mistakes users made.
To be able to collect them and make advices against them.

There is the Wiki, the FAQ ... and not really organized and user friendly.
I suggested a tree/hierarchy structure for there like (just a stupid list):

Battery
- DiY from Cells
- - Before buying Cells
- - Cell buying options
- - Before building a pack
- - - Cell identify
- - - Cell testing
- - - Cell top balance (not optional)
- - Building a pack
- - - Cell placement/cabinet
- - - Cell separation
- - - Cell compression
- - - Cell order series and parallel
- - - Busbar options and todo when connecting the cells
- - - - Seller given nickel plated copper
- - - - User made flexible cable
- - - - Aluminium busbars
- Manufactured like 12V battery
- - Battery buying options
- - Battery pack build
- - - Battery placement
- - - Battery order series and parallel
- - - Battery connectors, cables

BMS (not optional)
- Types
- - FET based
- - Relay based
- Balance types
- - passive balance
- - active balance
- Before buying a BMS
- Buying options
- BMS to battery build
- - BMS placement
- - BMS cable order
- - BMS cable management
- How to start the BMS
- How to monitor the BMS
- BMS connections like RS485

Where you can open categories and select possibilities like battery is DIY (from cells) or 12V battery, and if DIY then there is the what to do list (for building it) like before buying what to do, how to order, how to top balance ...

A step-by-step handbook is a good idea too. But I am afraid that every system is unique. Like some start from cells, some from 12V battery. Different connections, different protections (no BMS, but balancer), .... different build and build problems.
Getting a bit out of scope.

The scope is “DIY Battery Handbook”.
 

upnorthandpersonal

Administrator
A single page document with wiki links to each aspect would suffice, would it not?

In principle yes - and links to details would be good, but the Wiki needs some work and I think it can be a lot more clear.

The main idea is similar to what INCOSE did with their SE handbook (keeping in mind the target audience, and scope), with a focus on safety - see the "up in smoke" thread.


It doesn't touch on the topics this would, and is much broader in scope than this should be. The majority of the issues we've see in "up in smoke" thread can be used as examples where a simple failure analysis can come to the root cause of the issue. The 'root cause' is what this document would focus on to prevent these cases. It's also not the goal to summarize each an every nuance (remember the compression thread) - while these threads provide valuable information, no one is reading these in their entirety, and it would be relatively straight forward to focus on key aspects, a minimal set of guidelines, to do the minimum to be safe (even if that means sacrificing performance).
 

upnorthandpersonal

Administrator
For example, based on data and the associated experiences from the "up in smoke" thread "last fire..." you can pretty much establish a recommended (best practices) design using a typical BMS with Low/High voltage disconnect in addition to fire blocking so that any cells that fail and cook-off are contained. It doesn't matter if the BMS is FET based or Relay based - this is getting too much into details where people have opinions on one or the other. The root issue is: use a BMS with Low/High voltage disconnect in all cases and put your cells in a safe place in case something goes wrong (so your house doesn't burn down like that other thread in "up in smoke").
Does that mean everyone will follow these things to the letter? Of course not, you'll always have exceptions which can be judged on on a case by case basis - the idea is that the document describes a best practices from a safety perspective so that the majority of issues dealt with by new users (bloating cells, no BMS, power supply issues, compression/fixture issues, etc. ) have a clear best practice use case without all the nuances you get in pages long threads.
 

mrzed001

Voice of reason
Yeah but this post was specific to a DIY pack.
That is true.
But even DiY packs vary like 4s, 8s, 16s, 2pXs or Xs2p ...
Different build, different BMS, different fixture, ... not to speak about the different ways the cells in a 16s pack can be placed :)
So for a linear handbook you need a specific build to explain step-by-step.
 

upnorthandpersonal

Administrator
That is true.
But even DiY packs vary like 4s, 8s, 16s, 2pXs or Xs2p ...
Different build, different BMS, different fixture, ... not to speak about the different ways the cells in a 16s pack can be placed :)
So for a linear handbook you need a specific build to explain step-by-step.

It would be too out of scope I think to go into each possible battery configuration. However, we can focus on what they all have in common: use of a BMS and BMS minimum requirements, dealing with your terminals, cells in parallel yes/no and why?, fixture requirements, fusing, disconnects, etc.
 

mrzed001

Voice of reason
It would be too out of scope I think to go into each possible battery configuration. However, we can focus on what they all have in common: use of a BMS and BMS minimum requirements, dealing with your terminals, cells in parallel yes/no and why?, fixture requirements, fusing, disconnects, etc.

So you think it more like a best practice handbook (for separated sub items) than a step-by-step how to build handbook ?
 

Short_Shot

Photon Sorcerer
That is true.
But even DiY packs vary like 4s, 8s, 16s, 2pXs or Xs2p ...
Different build, different BMS, different fixture, ... not to speak about the different ways the cells in a 16s pack can be placed :)
So for a linear handbook you need a specific build to explain step-by-step.
It doesn't need to be as drawn out as stated.

A few picture diagrams can cover the goofy configurations.

4s 8s 16s are the same thing, just different voltages.

Putting cells in parallel within a pack is the same thing to XsYp - each group of "p" cells becomes one "s".

It's easy to simplify.
 

upnorthandpersonal

Administrator
So you think it more like a best practice handbook (for separated sub items) than a step-by-step how to build handbook ?

Yes, not a step by step guide - a best practices guide to prevent fire/bloated cells/potential other safety concerns. Something succinct, based on all the issues that we've seen in threads like the ones in the "up in smoke" forum. All of it should come from a safety first perspective, even if that means more expensive (Class T fuses for example) or comes with a performance penalty.
 
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