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Old 09-06-2020, 07:06 AM   #321
Sergio
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Default Re: Basic Nissan Leaf 7 module Lithium setup with Generic Chinese BMS

I could not read those small screen shots, what are the settings for: "Cell over voltage" trigger and release values that You are using to test?

What was the cell voltage before you plugged the charger to test?
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Old 09-06-2020, 09:59 PM   #322
itry2fly
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Default Re: Basic Nissan Leaf 7 module Lithium setup with Generic Chinese BMS

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Originally Posted by Sergio View Post
I could not read those small screen shots, what are the settings for: "Cell over voltage" trigger and release values that You are using to test?

What was the cell voltage before you plugged the charger to test?

The screenshots show that on the Overvoltage event, the "Charge OFF" icon flashes red, and on the Undervoltage event, the "Discharge OFF" icon flashes red. It appears the BMS only cuts the MOSFETS on whatever logic includes the "Discharge" side.

For HV testing, I was using cell voltage of 3920mV / 3850mV release. For the pack HV test I just set it to 54000mV to get them to trigger.

With the C- and B- disconnected to everything, I have continuity between them on BMS during the HV Overvoltage test, and no continuity (working as designed) during the LV Undervoltage tests.

Do you think there is not enough difference in the voltage thresholds or something maybe preventing the HV cutoff? I am going to have to find a way to run the battery pack down a bit before I do much more testing since the charge is getting close to my 57.4 preset anyway. I have a couple of 24V cooling fans I'll connect in series I think to get it back down for now.
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Old 09-07-2020, 09:05 AM   #323
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Default Re: Basic Nissan Leaf 7 module Lithium setup with Generic Chinese BMS

The IOS screenshot showing only one side OFF is typically an indication the BMS is Split Port (P- and C-) design or the software somehow is configured for that type of board.

Since the boards are generic, meaning the same PC board is used for both "split" and "same" ports designs, the software may have an accessible configuration setting for that feature.

Check all of the screens of the IOS app and see if there is a system configuration for "charge/discharge=same port" or equivalent.

As long as the P1 light stays ON the BMS is not disabling the relays and no protection is provided.
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Old 09-07-2020, 12:40 PM   #324
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Default Re: Basic Nissan Leaf 7 module Lithium setup with Generic Chinese BMS

Some just occurred to me, perhaps that BMS C- connection you have is two directional paths with opposite directions.

If You want to test it, disconnect the charger negative output from B- and connect it to C-.

The BMS B- connection to pack wire needs to be able to handle the charging current.

As long as your charger output is less than the BMS rating it should not be an issue.

If the "charging off" means the C- only stops that from returning to the charger negative, then the charger current will stop even if K2 stays latched.
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Old 09-09-2020, 07:08 PM   #325
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Default Re: Basic Nissan Leaf 7 module Lithium setup with Generic Chinese BMS

Ok Sergio, thank you I will try that tonight and see what happens. I emailed the BMS seller to see if they have any ideas as to whats up on the unit as well.
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Old 09-10-2020, 12:17 PM   #326
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Default Re: Basic Nissan Leaf 7 module Lithium setup with Generic Chinese BMS

I also sent an email to the developer to understand if there has been a software update that changed the behavior or if there is a different firmware that I can flash into my BMS.

As far as I remember when I was testing all this stuff around Christmas, the BMS was disabling both FETs on either fault.

With the newer apps (Version 3.1+) You can see that only the "charge" FET is being disabled during an over-voltage condition.

I have changed the drawing in the first post to reflect the charger negative connection directly to C- to be safe.

If only the "charge" FET is disabled during over-voltage and the charger negative is not connected to the common "C-" port, there needs to be a small isolated dc-dc converter to pump current backwards on that "C-" in order to detect the "charge" FET being turned off.

I may play with that concept as it would be the only way to catch an over-voltage during Regen brake.

The isolated dc-dc converters are cheap from China (less than $10) but it takes quite a while to get them delivered.

The BMS firmware already accepts a "global" FET shutdown command that it is currently sent when you press the "lock" button, so hopefully it is possible to issue the same command on either LV or HV condition.

I will post more information if I receive a reply from my request or have a chance to do further testing.
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Old 09-13-2020, 08:24 PM   #327
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Default Re: Basic Nissan Leaf 7 module Lithium setup with Generic Chinese BMS

Quote:
Originally Posted by Sergio View Post
I also sent an email to the developer to understand if there has been a software update that changed the behavior or if there is a different firmware that I can flash into my BMS.

As far as I remember when I was testing all this stuff around Christmas, the BMS was disabling both FETs on either fault.

With the newer apps (Version 3.1+) You can see that only the "charge" FET is being disabled during an over-voltage condition.

I have changed the drawing in the first post to reflect the charger negative connection directly to C- to be safe.

If only the "charge" FET is disabled during over-voltage and the charger negative is not connected to the common "C-" port, there needs to be a small isolated dc-dc converter to pump current backwards on that "C-" in order to detect the "charge" FET being turned off.

I may play with that concept as it would be the only way to catch an over-voltage during Regen brake.

The isolated dc-dc converters are cheap from China (less than $10) but it takes quite a while to get them delivered.

The BMS firmware already accepts a "global" FET shutdown command that it is currently sent when you press the "lock" button, so hopefully it is possible to issue the same command on either LV or HV condition.

I will post more information if I receive a reply from my request or have a chance to do further testing.
I'll be curious to see what you find out. I haven't tidied everything up yet so I can back and make this change pretty easily. At some point before I make that wiring change, I will set my voltages lower and see if it will cut out the way that it is currently wired. Mine definitely cuts out on low voltage and cuts out when turn off the BMS.

The charger itself cut off the way it was supposed to the last time I charged it a few weeks ago.
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Old 09-14-2020, 10:21 AM   #328
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Default Re: Basic Nissan Leaf 7 module Lithium setup with Generic Chinese BMS

If You are still assembling the pack go ahead and run the charger negative to C- as the drawing in the first post reflects.

The charger does stop by itself but since it cannot see individual cell voltages it could potentially be an issue with an unbalanced pack with a charge voltage near the top of the range.

I only charge my pack to 4.05v/cell and the cells are in pretty good balance (<0.01v) so it is not critical but I may re-wire mine later if no other solution.
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Old 10-08-2020, 06:57 AM   #329
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Default Re: Basic Nissan Leaf 7 module Lithium setup with Generic Chinese BMS

Thank you so much for this thread Sergio as I'm pretty sure its going to be the model I use to build a pack for my 1991 EZGO Marathon. I found this charger on Aliexpress (because your original link is no longer available on Amazon) and after studying the pictures and specs, it seems like its the same one (rebranded) and should work for a standard 7 cell pack. If it works, it will also be another option for people who can afford to wait for a charger. Thoughts?

Aliexpress charger link
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Old 10-08-2020, 08:45 AM   #330
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Default Re: Basic Nissan Leaf 7 module Lithium setup with Generic Chinese BMS

Most of those Chinese charges are the same generic model with a private label on top.

The diagram on their site shows a trimpot that may be for voltage adjustment but you should ask the seller if the charger output voltage is adjustable as some models are not.
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