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Old 04-15-2021, 04:20 PM   #31
Pat911
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Default Re: Best and most affordable charger for lithium leaf 14s pack

Quote:
Originally Posted by DaveTM View Post
The advantage of a charger with CANBus is your ability to set (or change) the top charge limit with your BMS.

My current setup is the charge the pack to 57.0 volts or 4.07V per cell. Initially I set it at 58.0 volts (4.14V per cell) but backed it off to extend the life of the pack.

As I understand it, the charger "knows" to charge the pack to 57.0V. The charger doesn't know (or care) what each cell is charged to.

So, for an overcharge to occur, both the charger and the BMS would have to fail at the same time. Possible....but not probable for such an event to occur.
That's not what was stated earlier when another member posted that the BMS tells the charger to reduce its current. So the communication that occurs is only to pass configuration parameters from the BMS to the charger? They do not need to communicate to be able to do that. I set my charger maximum voltage at what I want to charge to. I can also set my charger maximum charge current.

I can set minimum and maximum cell voltages as well as balance start and stop voltages, pack minimum and maximum voltages etc....all within the BMS itself. The BMS will disconnect the charger (and load for that matter) under any fault condition without actually communicating with the charger.

A BMS is a supervisory or safety item and as such should be treated as one. Everything should go on around it as normal (charging and discharging) with it only intervening when it has to. In normal operation it should never cut charging or discharging. In industry, a safety system is always stand alone as you don't want a failure in a connected system or device to prevent the safety system from doing its job. Connections to/from a safety system should be kept at an absolute minimum for it to do its job effectively, nothing more, nothing less.

A true BMS will not even balance. A separate balance board SHOULD be utilised. But this topology requires double the amount of connections to the battery pack as both the BMS and the balance board need to know individual cell voltages. It is common practice now to combine these functions to make wiring simpler especially in high cell count packs. Hence when we talk about a BMS, what we really mean is a BMS with balance.

Cheers
Pat.
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Old 04-15-2021, 05:09 PM   #32
Ryan Tug Smith
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Default Re: Best and most affordable charger for lithium leaf 14s pack

Lol i feel you. Ill push it in the pool if i have to. And its charging now. So ill watch it until bed time. Then unplug the charger. A couple questions on the zeva set up.
*BMS min voltage. I put 3.14v on mine
*BMS max voltage. I put 4.15v on mine
*Balance voltage. Dynamic
*BMS hysteresis. 0.20v. No idea what this is
*max charge voltage. 58v
*max charge current. 10amp
*Rev current disp. No
*soc waring i did 30%
*full voltage. 58v
*warn current. Off
*trip current. Off
Sorry guys i know thats a lot but ive got so much tied up in it i cant mess this up and have to do it again.
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Old 04-15-2021, 05:51 PM   #33
DaveTM
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Default Re: Best and most affordable charger for lithium leaf 14s pack

Quote:
Originally Posted by Ryan Tug Smith View Post
Lol i feel you. Ill push it in the pool if i have to. And its charging now. So ill watch it until bed time. Then unplug the charger. A couple questions on the zeva set up.
*BMS min voltage. I put 3.14v on mine
*BMS max voltage. I put 4.15v on mine
*Balance voltage. Dynamic
*BMS hysteresis. 0.20v. No idea what this is
*max charge voltage. 58v
*max charge current. 10amp
*Rev current disp. No
*soc waring i did 30%
*full voltage. 58v
*warn current. Off
*trip current. Off
Sorry guys i know thats a lot but ive got so much tied up in it i cant mess this up and have to do it again.
I can't comment on your settings tonight. I'm exhausted from the day's activities. When I can, I'll look and compare them to what I have my settings at.
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Old 04-15-2021, 07:14 PM   #34
Pat911
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Default Re: Best and most affordable charger for lithium leaf 14s pack

Quote:
Originally Posted by Ryan Tug Smith View Post
Lol i feel you. Ill push it in the pool if i have to. And its charging now. So ill watch it until bed time. Then unplug the charger. A couple questions on the zeva set up.
*BMS min voltage. I put 3.14v on mine
*BMS max voltage. I put 4.15v on mine
*Balance voltage. Dynamic
*BMS hysteresis. 0.20v. No idea what this is
*max charge voltage. 58v
*max charge current. 10amp
*Rev current disp. No
*soc waring i did 30%
*full voltage. 58v
*warn current. Off
*trip current. Off
Sorry guys i know thats a lot but ive got so much tied up in it i cant mess this up and have to do it again.
Those settings are perfectly safe. They will not over charge or over discharge but you might want to drop the hysteresis a little. The hysteresis is the fault condition release voltage. So if the charging trips at 4.15v, the BMS won't reconnect until it drops to 3.95v
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Old 04-15-2021, 11:20 PM   #35
Bobbob
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Default Re: Best and most affordable charger for lithium leaf 14s pack

The manual say hysteresis is for stationary only. It can be turned off by setting to zero. Sergio also confirmed this on one of his posts on the Zeva.


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Old 04-16-2021, 05:46 AM   #36
cmysstailights
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Default Re: Best and most affordable charger for lithium leaf 14s pack

What do you have your balance voltage set at

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Old 04-16-2021, 05:50 AM   #37
cmysstailights
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Default Re: Best and most affordable charger for lithium leaf 14s pack

This was a few years ago.

I reached out to ian from zeva and here is his reply.

My question

Zeva bms on 7 leaf pack.* I keep hitting a high cell.* How does the bms balance work?* Will it still balance when stopped (attached pic)?* When it hits the high cell will it still balance.* Charger set to 58.0v 10amps.* Bms settings 14 cells, min volt 3.0, max volt 4.15, balance 4.14, hysteresis .02, stationary mode yes.**

His reply

Hi Andrew,

Yes, it will keep doing balancing even if a high cell has tripped the LV relay output. Looks like you have about 0.07V imbalance at present which isn’t too bad, but the BMS will be able to improve that over time.

58V max from the charger gives 4.143V average, so with the trip voltage set to 4.15V you only have 0.007V tolerance for imbalance between cells (assuming the charger’s output voltage is accurate - might not be exact), which is quite tight. I’d probably recommend bumping up the Max Volt to say 4.20V to give it a bit more margin. This is still a safe voltage limit for Leaf cells, and should prevent these BMS trips. Once the BMS has had some time to improve battery balance you may be able to reduce it again, though there’s no real harm having a larger BMS tolerance for imbalance if you’re not charging to the upper limit of 4.20V/cell.

Any particular reason you’re using a fixed balance threshold? Usually I’d recommend leaving it on Dynamic so that the balancers can be working more of the time (whenever they detect an imbalance, rather than only at the end of a full charge).

Kind regards,

Ian Hooper

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Old 04-16-2021, 06:39 AM   #38
DaveTM
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Default Re: Best and most affordable charger for lithium leaf 14s pack

Here are my settings. I have to actually look at my monitor to see what I have the SOC warning, Warn Current, and Trip Current are. I don't have those settings on my spreadsheet documentation. I put my settings that differ from your's in RED to highlight the differences.

*BMS min voltage. I put 3.14v on mine
*BMS max voltage. I put 4.15v on mine
*Balance voltage. 4.08 (That's 57V\14)
*BMS hysteresis. NO SETTING ONLY for stationary mode
*max charge voltage. 57v
*max charge current. 15amp
*Rev current disp. No
*soc waring i did 30%
*full voltage. 56v INSTRUCTION SAY 1V BELOW PACK V
*warn current. Off
*trip current. Off
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