Looking for a tool

nomad123

100 µW
Joined
Oct 5, 2017
Messages
8
Hello,
I've been searching for a webpage that had a simple tool where one could select the number of cells in series and parallel, then select if connecting in parallel first or series first and it would show a simple diagram and at the bottom would be a list of pros and cons of each type. It's mostly for educational purposes rather than for a wiring diagram of any sort.

I'm somewhat confident that I came across this via a link in a thread here but I just can't find it now. Been searching both here and on google without success.
Hoping someone who reads this knows the page and can link me to it.

Thank you.
 
mark5 said:
wesnewell used to post a link sort of like that but nothing about after showing you the wiring, the webpage would list the pros & cons of p vs. s. It was this webpage: http://scriptasylum.com/rc_speed/lipo.html

Also see:
parallel connection 1st or in series? https://endless-sphere.com/forums/viewtopic.php?f=14&t=41462

Thank you! The first part is kind of what I was looking for.
Re wiring: Similar to how the link above shows how the cells are connected, it would show the connections between cells depending on if they were parallel then series or series then parallel.
 
As I see it, the main pro's of series first, if using RC packs, is less connectors to add, or replace with soldered y's, when doing series first. A much neater assembly, with less octopus wiring.

The other pro is that you can separate out a bad section easy. Again, this applies to plug and connect stuff, not spot welded 18650 assemblies.

Personally, I did something in between. You know me, always different a bit. With RC packs, I found 10 ah a good size for multiple uses. Some bikes need 10 ah for a light ride, others wanted 40 ah for a long ride. I would take RC packs and parallel 5 ah bricks, then series, then if I wanted more than 10 ah, parallel again. This gave me 3-4 blocks of 48v 10 ah to use as needed, depending on the bike and the ride length. In general, I would charge as 10 ah sections, but could charge as 40 ah if I chose to. In all cases, I do not parallel any balance wires. I like to check each pack individually, when needed, and my use pattern only requires about 4 balance charges a year. To balance, I bring up any low cells by single cell charging. No bms, but its not impossible to have one on each section, and then still parallel them.

A very old, pretty crappy section can parallel with other new good ones to make a large long range pack. Provided no cells in the crappy old pack are any worse than the others in the pack. Just slightly puffed, 2/3 capacity cells, no less than half capacity ones puffed all to hell.


On the other hand, parallel first allows two major pro's as well. If spot welding 18650's or any other permanent connection, now you can have one balance wire per cell group, and any slightly weaker cells get support from the strong ones. In this situation, you must be careful not to include any truly shitty cells, because if you do, you are stuck with them.

And of course, once you have your big pack assembled, you can now use a bms and get balance charges every cycle.

And once you have a bms protected pack, or naked pack, its still possible to parallel several of them. Then its parallel, series, then parallel again.

So as you can see, what I favor is that,, some parallel, then series, then more parallel again, when packs would have been very large if done just parallel first. For me this is the only way, because I usually have 4-6 bikes, and one ride wants 10 ah, another 20, and another 40 ah.
 
dogman dan said:
As I see it, the main pro's of series first, if using RC packs, is less connectors to add, or replace with soldered y's, when doing series first. A much neater assembly, with less octopus wiring.

The other pro is that you can separate out a bad section easy. Again, this applies to plug and connect stuff, not spot welded 18650 assemblies.

Personally, I did something in between. You know me, always different a bit. With RC packs, I found 10 ah a good size for multiple uses. Some bikes need 10 ah for a light ride, others wanted 40 ah for a long ride. I would take RC packs and parallel 5 ah bricks, then series, then if I wanted more than 10 ah, parallel again. This gave me 3-4 blocks of 48v 10 ah to use as needed, depending on the bike and the ride length. In general, I would charge as 10 ah sections, but could charge as 40 ah if I chose to. In all cases, I do not parallel any balance wires. I like to check each pack individually, when needed, and my use pattern only requires about 4 balance charges a year. To balance, I bring up any low cells by single cell charging. No bms, but its not impossible to have one on each section, and then still parallel them.

A very old, pretty crappy section can parallel with other new good ones to make a large long range pack. Provided no cells in the crappy old pack are any worse than the others in the pack. Just slightly puffed, 2/3 capacity cells, no less than half capacity ones puffed all to hell.


On the other hand, parallel first allows two major pro's as well. If spot welding 18650's or any other permanent connection, now you can have one balance wire per cell group, and any slightly weaker cells get support from the strong ones. In this situation, you must be careful not to include any truly shitty cells, because if you do, you are stuck with them.

And of course, once you have your big pack assembled, you can now use a bms and get balance charges every cycle.

And once you have a bms protected pack, or naked pack, its still possible to parallel several of them. Then its parallel, series, then parallel again.

So as you can see, what I favor is that,, some parallel, then series, then more parallel again, when packs would have been very large if done just parallel first. For me this is the only way, because I usually have 4-6 bikes, and one ride wants 10 ah, another 20, and another 40 ah.

Hey! Thank you for the detailed info.
So i'm really looking to build a pack for a motorcycle... about 4 Kwhr at 48V. So i'm looking at 13s33p. My plan was to build 33p and then put 13 of these in series. It will be a sort of permanent pack with a BMS. Using some off brand chinese 18650 cells.
Looking at build videos on youtube... I intend to have one bus bar running through the parallel pack and connect the cells using a thin gauge wire to act as a cell level fuse. This also allows me to make the battery modular so I can better manage the space I have to work with.
What do you think? Does that sound feasible?

I'm a little confused on your parallel-series-parallel method. The way I understood it is: Using my example, it would effectively be 2 packs at 48V and X Ahr. Each with its own 13SxP setup and then they are connected in parallel? So effectively a more modular setup allowing to add more 13SxP packs to increase Ahr if needed. How would the BMS be connected though? Would it require a BMS on each individual pack or would it be possible to have a single BMS manage the multiple packs added in parallel?
 
Back
Top