Paulfrench35
New Member
Hello, what is the use of this page in the JKBMS software?
JKBMS and wire resitance
- Thread starter Paulfrench35
- Start date
BentleyJ
Solar Wizard
Values are the calculated internal resistance of each cell. If a large deviation appears on one cell it could indicate that cell is failing. Keep in mind the value would also include any problems with the wire and/or connections at the wiring harness plug and at the battery itself. Those should always be checked first before assuming the cell is bad.
Paulfrench35
New Member
Are you talking about that? Is this the value in ohms of the red balancing wires?
Cell Wire Resistance
Cell Wire Resistance
BentleyJ
Solar Wizard
Yes, those are the calculated values for total wire resistance of the cells & wiring. I re-read your first post and realized you were asking about a different menu item. Not sure, but it looks like it is a calibration form where the user can input the resistance of the wires and connectors so this amount gets subtracted from the calculated value thus showing true cell resistance values?
Hopefully some of the other JK BMS users can clarify this for us. I'm using the stand alone 2A Bluetooth balancer. It has the Cell Wire Resistance values but not the item shown in your first post.
Hopefully some of the other JK BMS users can clarify this for us. I'm using the stand alone 2A Bluetooth balancer. It has the Cell Wire Resistance values but not the item shown in your first post.
Steve_S
Emperor Of Solar
The values shown on Page-1 are for the cell leads to the terminal and calculated by the BMS. Your numbers are very good BTW, pretty hard to get much better than that.
On the settings page, you can override the values IF required but you'd need a really accurate multimeter to test each wire. I've not seen anyone need to do so.
On the settings page, you can override the values IF required but you'd need a really accurate multimeter to test each wire. I've not seen anyone need to do so.
Paulfrench35
New Member
Yes, I'am talking about this.
Paulfrench35
New Member
Should the length of the red and black wires (+ and -) coming out of the cells and going to the mppt charger be the same length or is it not important?
BentleyJ
Solar Wizard
No they don't have to be the exact same length. Based on the pic they are a short length so wire resistance is negligible as long as they are sized properly for the amperage.
The exception to the above is with multiple batteries connected in parallel to a bus bar then the cables should be the same length.
The exception to the above is with multiple batteries connected in parallel to a bus bar then the cables should be the same length.
Paulfrench35
New Member
In the case of several batteries, cables of different lengths cause what problems?
Steve_S
Emperor Of Solar
Various things can occur but mostly imbalanced charging. Unlike Lead Acid based chemistries which are "Brute Force" all Lithium Chemistries are actually Millivot & Milliohn sensitive (hence the fancy BMS'). Equal Length battery cables & consistency is quite important especially when dealing with paralleled packs. You can run packs with different AH's ie 230, 280 & 304 together quite easily, larger differences (over 100AH) require some fancy math and working out averages for things like EndAmps/TailCurrent and understanding that they will charge & discharge proportionately in relation to their capacities.
RCinFLA
Solar Wizard
- Joined
- Jun 21, 2020
- Messages
- 3,695
It is calculated from a balance current pulse push.
It is not super accurate but good enough to detect a bad sense wire connection. The measurement will be less accurate the more you back down balancing current setting.
It is easy to snag a sense wire and pull it out of its connection terminal lug. A bad bus bar connection may also be detected in the measurement, but it would have to be a really bad bus bar connection like forgetting to tighten down a lug nut. When you see a single abnormal resistance, first thing is to check bus bar connection before focusing on sense wire connection.
Normal cell voltage measurements momentarily shuts down any balancing current during the cell voltage sampling to avoid sense wire voltage drop from balancing current that would impact cell voltage measurement by BMS. This is a common practice for even low balancing current BMS's.
There is a limit to how much the sense wires series resistance can be before their resistance starts to impact the balance constant current circuitry controlling the amount of balance current delivered. If sense wire voltage drop gets too great the DC-to-DC boost converter creating the balance current will hit its maximum allowed voltage boost causing less than target balance current to be delivered.
It is not super accurate but good enough to detect a bad sense wire connection. The measurement will be less accurate the more you back down balancing current setting.
It is easy to snag a sense wire and pull it out of its connection terminal lug. A bad bus bar connection may also be detected in the measurement, but it would have to be a really bad bus bar connection like forgetting to tighten down a lug nut. When you see a single abnormal resistance, first thing is to check bus bar connection before focusing on sense wire connection.
Normal cell voltage measurements momentarily shuts down any balancing current during the cell voltage sampling to avoid sense wire voltage drop from balancing current that would impact cell voltage measurement by BMS. This is a common practice for even low balancing current BMS's.
There is a limit to how much the sense wires series resistance can be before their resistance starts to impact the balance constant current circuitry controlling the amount of balance current delivered. If sense wire voltage drop gets too great the DC-to-DC boost converter creating the balance current will hit its maximum allowed voltage boost causing less than target balance current to be delivered.
Berseker
New Member
- Joined
- Mar 22, 2020
- Messages
- 282
Just a general jk bms question..
my bms didn't come with neg and pos cables. is there a limit to what length of cable, I can use on the bms?
presently I have 35mm 7 inch and 9 inch for the p & b ports, I recall the OEM cables on some jk bms models are only 3 inch or so, hence why am wondering if the longer cables on mine would cause an issue
my bms didn't come with neg and pos cables. is there a limit to what length of cable, I can use on the bms?
presently I have 35mm 7 inch and 9 inch for the p & b ports, I recall the OEM cables on some jk bms models are only 3 inch or so, hence why am wondering if the longer cables on mine would cause an issue
chaosnature
New Member
- Joined
- Sep 15, 2022
- Messages
- 535
Hi All
any one know why we are getting all unknown values even though the CAN is o.k?
View attachment 196537
The Bluetooth code works - suggesting it has to be the GIO Pins wrong, i have tried 16/17 and 01/03 and even swapped them around.
please advise
regards
any one know why we are getting all unknown values even though the CAN is o.k?
View attachment 196537
The Bluetooth code works - suggesting it has to be the GIO Pins wrong, i have tried 16/17 and 01/03 and even swapped them around.
please advise
regards
ScrotpusGobbleBottom
Corn Pop was a bad dude.
This looks like mine. Do you have a box? Does the box have the PCB balance lines going down the middle? I have been telling myself that is why.
They are all unequal length and traces instead of wires for most of the run.
Like this?
Attachments
Steve_S
Emperor Of Solar
Those resistance number are simply AWFUL ! Seriously, they should be anywhere from around 0.045-0.075 if properly crimped and done with the full length wires as provided.
Use only Dry Crimps on the sense leads. 20-22AWG barrel !
Double strip the wire at the end, fold it over, insert into crimp barrel and crimp tight with a ratcheting crimper. * Silver Solder adds potential resistance and serves no extra purpose.
Use only NON-Insulated terminals to ensure a really good crimp.
Always seal over the barrel with Heat Shrink 1/8" shrink tube is perfect.
I've built "numerous" packs over the years and following above instructions has always yielded very close results. My current set of 6 Packs in my own bank are all between 0.059-0.067 for each BMS.
Use only Dry Crimps on the sense leads. 20-22AWG barrel !
Double strip the wire at the end, fold it over, insert into crimp barrel and crimp tight with a ratcheting crimper. * Silver Solder adds potential resistance and serves no extra purpose.
Use only NON-Insulated terminals to ensure a really good crimp.
Always seal over the barrel with Heat Shrink 1/8" shrink tube is perfect.
I've built "numerous" packs over the years and following above instructions has always yielded very close results. My current set of 6 Packs in my own bank are all between 0.059-0.067 for each BMS.
Mine was an EEL vertical kit. Everything was pre-done. Although I did notice a few had the heat shrink too close to the bolt surface. I assume they are done properly, but didn't cut the heat shrink and look. The bus bars are the flexible ones with orange around them. On their video it showed a larger bus bar at the bottom attaching the two stacks. However they were showing batteries with two bolt holes and mine are a single stud.
Attachments
Yes mine has the PCB board. See my pic.
Your crimps look great. Mine were all done an on a PCB board. The bus bars had screw mount holes to attach the wires. On a few the heat shrink covered part of the mating surface. I made note of that but didn't think too much about it at the time.
ScrotpusGobbleBottom
Corn Pop was a bad dude.
Yes as mentioned, i think this has to do with traces instead of wire.
Mine is an EEL as well. And resistance looks exactly the same
I sent a message to EEL. They asked for a photo. Which I sent. I will let you know what they say. Maybe this is where you change the wire resistance settings in the JK BMS to reduce this number to a normal level. Or the PCB board is defective.
ScrotpusGobbleBottom
Corn Pop was a bad dude.
Cool, yeah it's a bad design.
The jk inverter bmd did come with other cables. If you want to rewire it, that's a good option
yea those are high. I have my cells in vertical lines so I had to extend the last 8 wires.. 5cm or whatever per cell, so the last one is double the length about. It has 0.064..
using 20 gauge "door bell" wire found at basically any store with wires (home depot / lowes / walmart etc).
oh didn't see this, yea it is bad especially for that.
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