Which JK 24v BMS?

[740GLE]

Sorry what's this mean, that you don't need a JK switch? or that you can use a generic one?

So my JBD came with an optional wired switch that I’ve never used.

I believe the JK switch is similar, it’s also a small gauge single throw switch that I’m guessing isn’t required to turn on the BMS.

Anyone care to comment? The BMS on/off external switch, it’s optional right?

 

[Rednecktek]

So my JBD came with an optional wired switch that I’ve never used.

I believe the JK switch is similar, it’s also a small gauge single throw switch that I’m guessing isn’t required to turn on the BMS.

Anyone care to comment? The BMS on/off external switch, it’s optional right?

I've never needed or used the switch until I did my first JK BMS, now I can't figure out how to NOT need the switch on it!

 

[740GLE]

I've never needed or used the switch until I did my first JK BMS, now I can't figure out how to NOT need the switch on it!

Ohh snap, that’s gonna stink if I have to source a new connector/switch.

Looking at some videos I might be able to pick up the display that has an on off switch if I can’t make the broken connector work.

 

[Rednecktek]

Ohh snap, that’s gonna stink if I have to source a new connector/switch.

Tell me about it! I had to overnight a new BMS so I could replace the leads harness. There's a $200 bundle of wire.

 

[upnorthandpersonal]

I never used the switch. A 9V battery to turn it on, and I haven't had a need to turn them off during normal use. When working on the battery, I just unplug the two balance lead connectors if the BMS has to be off.

 

[omaigadlol]

Thanks for the info! I'm ordering my first JK BMS and trying to see what else I need - just the balance leads plug, right?

 

[740GLE]

I never used the switch. A 9V battery to turn it on, and I haven't had a need to turn them off during normal use. When working on the battery, I just unplug the two balance lead connectors if the BMS has to be off.

Thanks, I’ve also seen diode test of a DMM wakes them up. I’ll keep these options in mind when I convert my 4s over the winter.

 

[upnorthandpersonal]

I’ve also seen diode test of a DMM wakes them up

This works 'sometimes'. It depends on the meter, and some other seemingly random variables.

 

[Bob B]

I am also new to the JK BMS. I have worked with the JBD and the Chargery, and trying to get up to speed a little on the JK. I am getting the B2A8S20P.
I'm also wondering about the power switch ..... I see Hankzor has it for only $.99.

Does powering off via the power switch eliminate all power draw from the BMS?

Also, does the heating option need to ordered with the BMS ... or does it just require the correct cable for the B2A8S20P?

 

[Rednecktek]

The heater requires the 20p-h version.

 

[Bob B]

The heater requires the 20p-h version.

That's what I expected ... Thanks for the verification. Is that the model you are doing your build with?

Not sure I like the idea of having to reach the charge cutoff before enabling heat .... I'd kinda like to have independent control to keep the pack warm enough it never cuts off charge.

 

[Rednecktek]

Yup, although it says 3a max for the heaters so I've put a relay on that circuit to allow for my 4x 20w heating pads.

 

[Rednecktek]

That's what I expected ... Thanks for the verification. Is that the model you are doing your build with?

Not sure I like the idea of having to reach the charge cutoff before enabling heat .... I'd kinda like to have independent control to keep the pack warm enough it never cuts off charge.

I thought about getting another thermostat involved but decided "I paid for this feature, I'm gonna USE this feature!"

I did put the positive to that circuit down wind of the breaker so it doesn't kill the battery trying to heat it up for the months that it's below freezing and unattended.

I also have a couple of those thermostats in the spares bin so I can always convert later.

 

[Capt Bill]

I recently hooked up my first ever JK BMS to my DIY 48v 305Ah LiFePO4 build. I obtained the B2A-24S-20P version. I also paid extra for the Larger 4.3" LCD Screen. I have hook it up, got my app and screen working properly, configure settings how I want, tested some, and really Like this JK BMS, and its' 2A Active Balance abilities. ... One area of minor concern: I NOTICED a voltage deviation between my JK BMS readings, and my DMM v reading of about 0.010V. on one particular Battery Cell. ??? I used that info to start my Balance at 0.015v Diff; instead of less mv. ... My wondering QUESTION; that might get answered later via my diy experimenting ... : Could entering an up or down resistance value to BMS setting for the balance wires ... for that particular cell (they are all default set to 0.000 ohms, same measured via my DMM double check.) ... I Am Wondering ... if I could get the JK BMS Cell volt reading to match my DMM? ... for that one particular cell reading about 0.010v less than my DMM ??? Has anyone played with that idea yet? Not a huge deal/ ... I just like accuracy and perfection. I did notice the balance wires going into white plug can shift a little bit in and out at plug (when disconnected) / so I am going to push each little red balance wire in all the way on next step to see if that might make that particular v reading contrast more accurate. :+)

 

[ArthurEld]

I have 5 of the 200 amp versions. The last one I bought from 18650batterystore. I bought a start switch and a RS485 module to but haven't tried them yet. These BMS's are everywhere and they are very reasonable in my opinion.
These JKs have all of the features I wanted and nothing better has come along yet that I know of.
I've had 4 of them for 2 or 3 years.
Capt Bill, I think the settings have an option to adjust the resistance on each balance lead. Maybe that would give you what you want. I haven't used those settings myself. There is also voltage and amp calibration in the settings.

 

[hwse]

NOTE: For instructions on heating cables,
the green 5PIN cable of the heating cable needs to be linked to the heating pad,
and the rest of the black and red cables are linked to the smart charger
(after the smart charger links the BMS,
it detects the temperature of the battery through the BMS,
which automatically monitors the charging status of the battery)
Heat Function interface
Description of heating function:
Battery temperature is below low temperature charge protection, turn off charging, turn on heating.

Cryogenic charge protection is a parameter that can be set within APP

The heating power depends on the battery voltage and the resistance value of the heating film.

Battery voltage U.

Heating resistance R.

Power equals U*U/R

Heating current I=U/R;

The maximum I (current) of the board design is 3A.

MAX heating power 200W(100W OF B2A8S20P).

I was really happy when JK announced that they would build the heating capability into the JK 8s version, but the programing is less than useful. In my opinion it is not correct to turn off charging and turn on heat at the same temperature. For a heated battery, the idea is to prevent the BMS from turning off charging. It would be better to turn on charging at a slightly higher temperature than the LTD so that the charging will not need to be turned off. It seems that this should be just a programing change which would make it much more useful. Most of the user's I know of who heat their JK equipped batteries do not use the BMS function. They install a seperate thermostat to control heating.

 

[BjornM]

I never used the switch. A 9V battery to turn it on, and I haven't had a need to turn them off during normal use. When working on the battery, I just unplug the two balance lead connectors if the BMS has to be off.

Are you using the B2A8S20P?

I've been looking at the manual for this BMS, and I'm trying to figure out the best way to kick start it after the pack is fully assembled. Are you saying that you connect an ordinary 9V battery between the P- and B- terminals? Manual says to have a charger voltage that is 2 V higher than the pack's voltage, and this will start the BMS. My charger will not go that high when the cells are top balanced.

And the "switch" discussed in this thread, I assume it is to turn the BMS off? No examples of such a switch in the manual. But I assume it could be on the P1 connector pin 10, which is the "Power supply of protection board, connected to battery positive" (from the manual).

 

[upnorthandpersonal]

Newer models have a physical switch to turn them on (and off), and a port on the BMS to connect them to. See:

JK 4S 200A BMS

@Nami wouldnt it be cool the make some settings on the power of the heating pads and let the bms decide if there comes enough power in via loading Amps to power the heatmate... may be 2 settings... so that if temperature lower than setting 2 (discharge limit temperature of the battery) is...

diysolarforum.com

To turn on the BMS with a 9V battery: connect the positive side of the 9 volt to the negative end of the cells, the B- lead of the BMS. Then touch the negative side of the 9 volt battery to the P- lead of the BMS.