11-11-2020, 05:26 PM | #11 | |
Getting Wild
Join Date: May 2016
Location: Atlanta, GA
Posts: 129
|
Re: LiFePO4 BMS Wiring Help
Quote:
You did pique my curiosity with the 2 AWG wire requirement. I will switch it from 4 to 2AWG as you suggest, but considering this is only the connection between cell 8+ and cell 9-, how is it that those little metal plate connectors have less resistance than a 4 AWG wire? Not doubting you, just trying to understand. |
|
Today | |
Sponsored Links
__________________
This advertising will not be shown in this way to registered members. Register your free account today and become a member on Buggies Gone Wild Golf Cart Forum |
|
11-11-2020, 07:15 PM | #12 | |
Gone Wild
Join Date: Apr 2017
Location: SE TN
Posts: 2,218
|
Re: LiFePO4 BMS Wiring Help
Quote:
|
|
11-12-2020, 06:52 AM | #13 |
Gone Wild
Join Date: Sep 2012
Location: Charlotte, NC
Posts: 9,329
|
Re: LiFePO4 BMS Wiring Help
What is the gauge of the B- and C- wires from the BMS?
Good connections and crimps are more important in this case since that short piece of cable will not have much resistance and 4ga is more than enough. Any voltage lost in those connections during high current will affect the cell voltage readings. The CALB cells have a clever design where the distance between two adjacent modules is the same regardless if you place them on the long or narrow sides. That is not the case on your cells and I don't know if you are making your own connecting busbars or if the company sent you both short and long busbars so this suggestion may not apply. If You do have long busbars (8 total) to connect the cells between the modules that are next to each other on the narrow sides you can wire the entire pack with busbars and not use external cables, the pack connections would be on the bottom left (+) and right (-) sides of the box. You would need only one long busbar if the pack connections were the two posts near the box center hole. I looked at the link for the BMS and I did not see the on/off signal switch wired to the board on their picture, how/when does that relay power off? It mentions a timer to put the BMS to sleep (relay off, no balance, no monitor and no communications) but not how to get the BMS out of sleep mode. |
11-12-2020, 09:23 AM | #14 | ||
Getting Wild
Join Date: May 2016
Location: Atlanta, GA
Posts: 129
|
Re: LiFePO4 BMS Wiring Help
It's 2ga everywhere else. I went ahead switched it to 2ga between cell 8 and 9, just to keep it consistent, if anything else.
Quote:
Quote:
|
||
11-12-2020, 10:41 AM | #15 |
Gone Wild
Join Date: Sep 2012
Location: Charlotte, NC
Posts: 9,329
|
Re: LiFePO4 BMS Wiring Help
You just need the short buss-bar between cells 8 and 9, no other cell orientation changes are needed on your design.
I saw online they sell both length buss-bars for those types of cells, I understand it is too late for you but perhaps future members reading this thread will have the opportunity to get the two size buss-bars for a more compact setup. I would ask the seller the question about the BMS relay coil handling, meaning how does it turn off and back on again. Even if it is automatically based on the BMS detecting a load (which means the BMS would not be totally "sleeping") You then need to ask if they have a "soft start" circuit. If You have a voltage converter for 12v, there will be a good size spark when that relay "closes" or the BMS may never go to sleep depending on the threshold current needed to wake up the BMS since the cart is always using current. Those boards have a place to solder two small gauge wires to make a "on/off" signal switch, depending on their answer you may want to do that before mounting everything and then enable the switch in the software. |
11-12-2020, 04:20 PM | #16 | |
Getting Wild
Join Date: May 2016
Location: Atlanta, GA
Posts: 129
|
Re: LiFePO4 BMS Wiring Help
Quote:
|
|
11-12-2020, 04:54 PM | #17 |
Gone Wild
Join Date: Sep 2012
Location: Charlotte, NC
Posts: 9,329
|
Re: LiFePO4 BMS Wiring Help
Having a relay instead of FETs is a good idea for that design as it allows for more current handling without the heat concern, it is just a matter of finding out how they handle the relay activation as it needs to be powered OFF when not in use so it does not burn the coil.
Perhaps it is some type of "latching" relay so that is not even an issue. WalterM6 may have more information since he got the same type of BMS before you did. |
11-12-2020, 05:33 PM | #18 |
Getting Wild
Join Date: May 2016
Location: Atlanta, GA
Posts: 129
|
Re: LiFePO4 BMS Wiring Help
Thanks. Yeah, I'll wait for him to chime in. I was planning to follow his setup, but his battery issue set him back a bit. Sounds like he may be back on track.
|
11-13-2020, 07:19 PM | #19 |
Gone Wild
Join Date: Apr 2017
Location: SE TN
Posts: 2,218
|
Re: LiFePO4 BMS Wiring Help
Good news. I got my batteries installed today. The problem with the runaway battery was solved by top balancing the cells. They are all now within 10mv. Set my max voltage to 53.6V, 3.35 v/c. That is supposed to be 99% charge. The idea about the binding posts worked out good. I got all the big terminals connections secure with them. Btw I went with 4 ga for the B8-B9 connection, it was more flexible. I took it out to test drive and the performance was similar to the leaf pack. I took it up the biggest and longest hills and the neither the battery or the terminals showed any great heat increase. That was one of the things I was worried about because of the small bus bars and hardware. The only thing I have left is to calibrate the SOC reading. I am now a happy driver.
|
11-13-2020, 08:56 PM | #20 |
Gone Wild
Join Date: Apr 2020
Location: Hurricane, Utah
Posts: 2,744
|
Re: LiFePO4 BMS Wiring Help
So jealous! Congratulations!!!
|
Tags |
16s, bms, lifepo04 |
|
Thread Tools | |
Display Modes | |
|
Similar Threads | ||||
Thread | Forum | |||
LiFePO4 Battery Charger | Lithium Club Car | |||
LifePO4 golf battery | Lithium EZGO | |||
LiFePo4 in 48v truck | Extreme DC! | |||
LiFePo4 batteries | Electric Club Car | |||
LiFePo4 conversion | Electric EZGO |