neptronix said:N.E.S.E with 21700's. It'll be expensive but it will be easy to build a pack.
BlueSeas said:http://www.smartgauge.co.uk/batt_con.html
agniusm said:BlueSeas said:http://www.smartgauge.co.uk/batt_con.html
I would skip that article. 10A draw drop in a string between couple batteries with such thick cable is nonsense.
He writes himself that it is simulated with god knows what integers.
Math would suggest that it would total at 0.00032 ohm with hes numbers."Typically the batteries are linked together with 35mm cable in a good installation (often much smaller in a poor installation). 35mm copper cable has a resistance of around 0.0006 Ohms per metre so the 20cm length between each battery will have a resistance of 0.00012 Ohms. This, admittedly, is close to nothing. But add onto this the 0.0002 Ohms for each connection interface (i.e. cable to crimp, crimp to battery post etc) and we find that the resistance between each battery post is around 0.0015 Ohms."
john61ct said:The varying load issue from connection layout is not **nearly** as great an issue when the paralleling is done at the 1S level.
If these packs were serially wired, and then put in parallel at the top level (say 20S6P rather than 6P20S) then yes, that "geographic issue" would be concerning.
999zip999 said:You can bolt these together look at the A123 build thread on bolting together cells ez peze.
https://endless-sphere.com/forums/viewtopic.php?f=31&t=109869.
Like this.
https://endless-sphere.com/forums/download/file.php?id=82024&mode=view
I built a A123 20ah pouch battery with this method.
7years 1,485 charge cycles.
agniusm said:Your suggestion of the testing will result in 0 difference. Parallel cells balance each other out so you will see no measureable difference.
999zip999 said:Read article
Ok there is a throw rod on this through rod there is tubing like used for the refrigerator ice maker it goes on the outside the rod to insulate it it's all said in the article it even tells you what pieces to buy and what nuts the whole thread at that point is a hold your hand and walk you through it all the way to where you can buy the parts and the part numbers it's the most no braining thing you can do plus 30ah cell.
Clearly you don't, and what "analogy"?BlueSeas said:I'm not sure I understand your logic. In the linked article, they are 12V batteries, however I think about them as a new chemistry cell with 12V nominal potential. I'm pretty sure his analogy would remain the same.
999zip999 said:Oh I gave photo have how hears link on second page go look.
https://endless-sphere.com/forums/viewtopic.php?f=14&t=38761
Durtlege I think .
john61ct said:Clearly you don't, and what "analogy"?BlueSeas said:I'm not sure I understand your logic. In the linked article, they are 12V batteries, however I think about them as a new chemistry cell with 12V nominal potential. I'm pretty sure his analogy would remain the same.
The issue there is uneven current rates when paralleling too many serial strings, thus uneven wear, thus reduced reliability and lifespan of the bank overall.
Really the solution is no more than two strings, ideally just one. Smart people just don't use a bunch of 12V units to build deep cycling banks anymore anyway.
But they act nothing like 12V cells in any case.
Cells in parallel (IOW @1S) function as a single battery, no uneven current rates, that page is just irrelevant to that scenario.
BlueSeas said:agniusm said:Your suggestion of the testing will result in 0 difference. Parallel cells balance each other out so you will see no measureable difference.
Not enough time for the cells to equalize if you break apart the paralleled group of cells right away. But there is probably a better, even easier way.
For some Headway capacity testing, I'm going to try and reopen the battery testing lab setup I used a few years ago.
But while I'm in there, I will parallel 4 cells using some wire instead of bus bars. Put them under a constant load. Take current measurements with a clamp on meter at each interconnect level. That will provide a real life answer to this question.
What gauge wire should I use? Smaller wire will make the difference larger. This would probably make it easier to see. What is the profile in mm of the bus bar you use? The limits of my testing setup is 30-40A unless I build a bank up to 12V, where I have more load options. With 4P, the max amperage of the final interconnect is 75% of the test value.
Here is a chart of voltage drop for various wire sizes at 25A. When you do a high current test, what generates the most heat? Is it the cell, the connection to the cell, or the bus bar?
Nothing would make me happier than to discover the cells are evenly loaded. Than I won't be as paranoid about equalizing the resistance path to the load for every cell in the bank.
999zip999 said:A set of kokram cells 16s and how many amps for how many watts. Math... Cheap EZ those cells will be gone tomorrow. But you asked us before you buy.
BlueSeas said:I have my eye on these:
https://a123batteries.com/a123-systems-3-7-volt-26ah-prismatic-pouch-cell-amp26-nmc/
A little smaller with less capacity than kokram. But think they will fit. Cheaper than the Headway's...but that's for just the cells. Haven't seen much discussion on these, but I haven't spent much time looking yet. They are a really good value on the $$ per amp scale.