Project Precedent

[simicrintz]

Good for you, UncleJerm!! I feel the same way about my pack; I learned a ton and would also do it again in a heartbeat!

[UncleJerm76]

Originally Posted by Pat911

Hi UncleJerm, Due to the discharge curve of LiFePO4, 3mv cell difference at 3.32v is meaningless. You really need to check the difference at 3.5v or better still, 3.6v or above. That's the real test. You may be out 100mv-200mv at that point.

Cheers
Pat.

Hi Pat thx again for the comments - I appreciate each and every one of them. You are absolutely correct on the flat LP4 curve. The following is kind of “in the weeds” ….but for my daily routine I am only charging using 3.5v CV and as the amps taper off to zero I achieve a much longer absorption time. The charger then kicks off when current falls below 10mA. I am doing this not only to allow more time for Daly to balance but also to maximize the life of my pack, I don’t feel there is enough capacity at 3.65 to justify it - not for me. Since I have a 200aH pack so there’s no reason to squeeze out those extra drops of capacity when i can make my pack last longer by not doing it. But on my next LONG ride I’ll try to remember to grab a few screens as the pack drains. That should offer a better story for you but so far I’m impressed at every SOC I’ve measured.

My balance logic: The BMS will protect if individual cells ever go to far over/under voltage so the only point of me having a well balanced pack is to use the entire pack capacity without one cell kicking the high/low limits, that’s really it. If I’m balanced after the charger kicks off and cells don’t drift far apart as the pack drains then I call that a huge success!

[UncleJerm76]

Originally Posted by simicrintz

Good for you, UncleJerm!! I feel the same way about my pack; I learned a ton and would also do it again in a heartbeat!

Thank you sir! Ive been reading some of your posts from your project - do you have a build thread documenting your whole process? I always enjoy reading those ...and I have a soft spot for the DS too

[Pat911]

Originally Posted by UncleJerm76

Hi Pat thx again for the comments - I appreciate each and every one of them. You are absolutely correct on the flat LP4 curve. The following is kind of “in the weeds” ….but for my daily routine I am only charging using 3.5v CV and as the amps taper off to zero I achieve a much longer absorption time. The charger then kicks off when current falls below 10mA. I am doing this not only to allow more time for Daly to balance but also to maximize the life of my pack, I don’t feel there is enough capacity at 3.65 to justify it - not for me. Since I have a 200aH pack so there’s no reason to squeeze out those extra drops of capacity when i can make my pack last longer by not doing it. But on my next LONG ride I’ll try to remember to grab a few screens as the pack drains. That should offer a better story for you but so far I’m impressed at every SOC I’ve measured.

My balance logic: The BMS will protect if individual cells ever go to far over/under voltage so the only point of me having a well balanced pack is to use the entire pack capacity without one cell kicking the high/low limits, that’s really it. If I’m balanced after the charger kicks off and cells don’t drift far apart as the pack drains then I call that a huge success!

Everything you've written there is absolutely correct, including your thoughts on keeping cells in balance.

[simicrintz]

Originally Posted by UncleJerm76

Thank you sir! Ive been reading some of your posts from your project - do you have a build thread documenting your whole process? I always enjoy reading those ...and I have a soft spot for the DS too

Somewhere I have pages of questions about how to do this, with a ton of replies and help from others on here (and which without I never would have got this done!). I'm not sure if it is really a build thread as much as a thread exposing my ignorance!

I'll try and find it and update; we gotta keep these old rigs going!!

EDIT: Bugs me to leave things hanging; here it is (do not read and operate heavy machinery-drowsiness may occur!)

https://www.buggiesgonewild.com/showthread.php?t=168103

[UncleJerm76]

Originally Posted by simicrintz

Bugs me to leave things hanging; here it is (do not read and operate heavy machinery-drowsiness may occur!) https://www.buggiesgonewild.com/showthread.php?t=168103

Awesome, I read the whole thing. Looks like it spawned serval side discussions that everyone learned something from. Thanks for the share!


Sent from my iPhone using Tapatalk

[UncleJerm76]

So how much did it cost to build my own 200AH Lithium Battery Pack from start to finish? Well below is my *true* cost sheet. I should note that the prices shown were mostly from last year and since starting my build back in July 2021 costs have dropped significantly! Literally the same exact items from the same exact sellers would be equal hundreds less if bought today. Procrastinators rejoice!

This isn't a "must have" list by any stretch, many items were tools that Ive been wanting, some are just nice-to-have and others were required. Before I started this project the estimates in my head were $2500. In any case hopefully this will help a passer-by or two who's been thinking about what would it all cost to do a DIY battery project. Any if you take out all the unnecessary tools and the nice Power Supply & Voltmeter, it's roughly about 1/2 of a drop-in solution. All prices are after tax and shipping:

$1,614.90 = 16pcs CALB Grade A 200aH Cells
$0,395.57 = 500A 16S Daly Bluetooth BMS with Fan Cooling
$0,243.95 = 0-60V 0-18A Bench Power Supply, (note: I started with a cheap one and realized how handy they are to have around, so i upgraded)
$0,142.06 = Klein CL800 600a accurate voltmeter (because all Ive ever used were free HF meters :)
$0,105.99 = 100ft SS Strap Band & Banding Strap Tool
$0,065.77 = Battery Cable Lugs, smaller terminals, spool of balance wire & heat shrink
$0,044.98 = 500A Waterproof Battery Monitor and Shunt
$0,042.29 = 10 Ton Hydraulic Terminal Crimper
$0,038.41 = Various Molex & other plug connectors
$0,032.49 = Ratcheting Weather Proof Terminal Crimper
$0,019.92 = Ratcheting Wire Terminal Crimper
$0,013.96 = Terminal Removal Tool Kit :)
$0,012.99 = HD 1/0 Cable Cutters
$0,007.42 = Micro Cutters
--------------------------------------------------------------------------------------------
$2,780.70 = Total

[dc.901]

Originally Posted by UncleJerm76

So how much did it cost to build my own 200AH Lithium Battery Pack from start to finish? Well below is my *true* cost sheet. I should note that the prices shown were mostly from last year and since starting my build back in July 2021 costs have dropped significantly! Literally the same exact items from the same exact sellers would be equal hundreds less if bought today. Procrastinators rejoice!

This isn't a "must have" list by any stretch, many items were tools that Ive been wanting, some are just nice-to-have and others were required. Before I started this project the estimates in my head were $2500. In any case hopefully this will help a passer-by or two who's been thinking about what would it all cost to do a DIY battery project. Any if you take out all the unnecessary tools and the nice Power Supply & Voltmeter, it's roughly about 1/2 of a drop-in solution. All prices are after tax and shipping:

$1,614.90 = 16pcs CALB Grade A 200aH Cells
$0,395.57 = 500A 16S Daly Bluetooth BMS with Fan Cooling
$0,243.95 = 0-60V 0-18A Bench Power Supply, (note: I started with a cheap one and realized how handy they are to have around, so i upgraded)
$0,142.06 = Klein CL800 600a accurate voltmeter (because all Ive ever used were free HF meters :)
$0,105.99 = 100ft SS Strap Band & Banding Strap Tool
$0,065.77 = Battery Cable Lugs, smaller terminals, spool of balance wire & heat shrink
$0,044.98 = 500A Waterproof Battery Monitor and Shunt
$0,042.29 = 10 Ton Hydraulic Terminal Crimper
$0,038.41 = Various Molex & other plug connectors
$0,032.49 = Ratcheting Weather Proof Terminal Crimper
$0,019.92 = Ratcheting Wire Terminal Crimper
$0,013.96 = Terminal Removal Tool Kit :)
$0,012.99 = HD 1/0 Cable Cutters
$0,007.42 = Micro Cutters
--------------------------------------------------------------------------------------------
$2,780.70 = Total

Thanks for this info! Am curious, you have charger and motor terminals connect at BMS (along with battery), or you have bus bars?
Sorry, I should perhaps look at the pics bit closely.

[UncleJerm76]

Hi DC901, I did buy large terminal blocks but didn't use them. I kept it as simple as I could; The stock cart had all the negative terminals at the controller, so I left it that way. I simply cut the main negative cable that used to run from the controller to battery pack negative, and then put the BMS in line where I cut it. I think this pic I posted >>here<< illustrates that best.

[simicrintz]

Originally Posted by UncleJerm76

Awesome, I read the whole thing. Looks like it spawned serval side discussions that everyone learned something from. Thanks for the share! Sent from my iPhone using Tapatalk

You're welcome.

In reply to your other post, I am afraid to add up what I spent And I am certainly not sharing it with the wife if I do......