BMS voltage settings

[burningwings]

I am ordering a new Bestech BMS for 18s 12p 18650 pack. Should I have the balance voltage set at 4.18v to increase battery life ? How about max voltage settings . They seem able to adjust the various voltages to order. What are the ideal settings for long battery life and decent range ?

 

[Ykick]

I try to not get too "fancy" with regard to "adjustable" settings. IMO, you'll never realize any difference or advantage between 4.2V - 4.18V balance voltage other than it's more likely to delay your order on the production line. Especially 12P groups?

EDIT to add - those boards can't dissipate enough heat to do any meaningful balancing on such large Ah capacity cell groups, IMO.

Here's a recent D167 datasheet with fairly standard settings I've been using across 6qty Bestetchpower BMS/PCM circuits:

 

[dmwahl]

If you're going to adjust the balancing voltage, go down to 4.10V or even 4.00V, 4.18V is nothing. The idea is to reduce the level of charge to limit it to something like 80-90%, 4.18V is basically 100%. Check the charge curve for your particular cells, but 80-90% should be in the 4.0-4.1V range. Doesn't take much balancing current unless you want really fast charging to 100% (which you don't seem to), and even then it isn't too important as long as you can periodically let it sit and balance for longer. 84mA of balance current like the datasheet Ykick posted will take care of 1Ah of imbalance in about 12 hours. Assuming you're not piecing the pack together with used laptop and power tool cells that are in varying states of health, they should stay pretty well balanced.

 

[shinyballs]

Does anyone have any experience of BestechPower really adjusts the HVC and also LVC from the factory according to the customer's needs?
Example: LVC = 3.30V, HVC = 4.10V

 

[circuit]

They do not. You get what you get... Like 4.6V cutoff voltage. I mean you will get 4.2V balancing threshold, but overvoltage cutoff will be like 4.6V.

 

[izeman]

@circuit: I can't confirm that. Mine works as ordered.
You have to know that you are very limited in what values the comparators will allow. So a certain HVC will need a certain LVC.
The only REAL problem those bms have is that they do not monitor if the cells are still connected. So if one balance wire gets lose the bms will continue working and you will lose some monitoring.

 

[circuit]

You are correct on issue with losing connectivity to one or more cells.
But as far as I know, for all analogue PCMs, OVC and balancing thresholds are different. I did not yet see a PCM with double rating: shunting threshold and OVC threshold.
I have tested a PCM received from bestekpower, and shunting level was more or less as specified, but OVC is much higher. So if you have an imbalance on your battery pack, some cells will be stressed a lot.

 

[shinyballs]

I just got a reply from Lucy. For the HCX-D166 bms, she said these are the only choices -

We do not the match as you want,4.10V.3.30V

we have the match as below:

1)4.25V,3.00V;2)4.28V,3.00V;3)4.28V,2.8V;4)4.20V,2.90V; this is our in common use.

 

[shinyballs]

I'm planning to use the bms in parallel with a VIctor dc-dc converter(33-75V input, 12V output) for my 72V pack. Are there any issues using it this way?

 

[izeman]

No