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    overlap New Member

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    Hi. I have been running with the new balancer for a few weeks now. Surprisingly, it ALWAYS has shown my #1 Cell >= 0.100 volts higher than the lowest cell when 3 Chargery Balancers never had cell #1 the highest and were able to balance the cells to below 0.020 volts down to ~ 0.007 when they would shut-off.

    The BMS16C NEVER equalizes the voltage of the cells. It must be defective, correct?

    Thanks!
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    dan2l 2014 Prius v wagon

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    Hi Overlap.
    I have detailed data on three functioning BMS16C balancers. My best bet is that your balancer is not defective. The BMS16C works a little different and I am still figuring that out. I can say that the BMS16C is clearly better than the DB8s.

    Can you get me data? The actual voltage reading for all 16 cells. If you do this manually I would like to see it at rest after setting over night with the bumper plug unplugged. And also right after the completion of a full charge.

    If you have CellLogs and want to automate the data collection, then shoot me a PM so that we can start Emailing the data files.

    Then we can look at that data and give you some informed advice.

    Thanks,
    Dan
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    pbui Member

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    The BMS16C online manual on page 2:

    Upgraded Version:
    One single BMS manages 16 pairs of battery cells, i.e a total of 32 cells;
    Suspending charging once any single cell exceeds 3.8V;
    Suspending output once a single cell drops down to below 2.5V;
    System sleeps if any cell drops to below 2V;
    Advanced cells inter-charging (balancing) feature at 1.0-1.4 A current (coming soon).

    So, is the manual outdated then ?

    Pb
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    dan2l 2014 Prius v wagon

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    Hi Pb,
    I do not know about what is meant by "coming soon". I do know that what I have now is clearly better than the DB8s. I appears to me that the balancing feature is working today. Clearly the overcharge protection is working.

    My guess would be that what you found is out of date.

    Thanks,
    Dan
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    overlap New Member

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    Hi Dan and others, thanks for your responses.

    Dan, I do not have data as I do not have the loggers. My job requires 1st hand data all the time and I appreciate your request. At the same time the observations is so straight forward and never changing that I think the data could only refute these claims.

    ALL the time now for 2 or 3 weeks with the car sitting in the garage unplugged day after day or or during the past 15 charges, there is ALWAYS a delta between the highest and lowest battery of 0.098 to 0.102.

    If battery balancing means anything, this delta should be eliminated whether done by resistors (passive) or capacitors (active).

    If this is indeed the data and such a straightforward observation it is, then it appears the balancer is not balancing. Reluctantly, I will contact Jack. I do find the note in the documentation interesting. Perhaps mine is one of these.

    Everyone Else, what is the smallest delta between the cells that you are observing?
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    linuxpenguin Active Member

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    Just for sake of argument here, balance can only be observed on the high and low end of the battery pack (the voltage curve on LiFEPO4 cells is a straight line in the middle of the pack). If you are observing significant delta voltage in the middle of pack discharge you probably have capacity issues.

    Depending on the accuracy of the BMS in question, it's reasonable to expect less than 10 millivolt differential when balanced (0.01v) after a full charge.

    Andrew
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    dan2l 2014 Prius v wagon

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    Hi Overlap,
    I think you are too symplistic in your thinking about this. Balancing is mor complicated tha just looking at the delta from high to low.

    Taking the data manually is simple. Push the button, write down 4 voltages, push the button, write down 4 voltages, Push the button, write down 4 voltages, Push the button, write down 4 voltages. You do not need a data logger to do that.

    If you choose to not communicate with data I think that you will not get the information that you need for improvements.

    Thanks,
    Dan
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    dan2l 2014 Prius v wagon

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    Hi Andrew,
    Yes this is very true. That is why I asked for data at the end of a charge as well as at rest. These can both be read manually. Getting data at the low end is much harder to obtain. You really need a data logging system to capture the low point.
    Almost flat. I see a variance from 3.1 to 3.3v in the middle. But the variation from cell to cell can be enough to confound this data even in perfectly good cells. I respectfully disagree with your statement about probably have capacity issues. I would say may have capacity issues.

    Thanks,
    Dan
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    linuxpenguin Active Member

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    Ohhhh Dan :rolleyes:,

    I never said he did have a capacity problem, just pointing out that he need only pay attention on the high and low end of the pack for balance. I also said that if he is observing a /significant/ delta-V in the middle that is a tell-tale sign of a capacity problem and/or a balance problem.

    My opinion would be that 0.2v is high for varience in LiFEPO4 batteries, especially in the middle of the pack--but hey, who cares about opinions anyway? :). Back when I had a LiFEPO4 system in my car I was always able to get the cells within 0.01v (10 mV) balance of each other using top-end passive balancing--granted, it was with a different BMS...but I digress.

    Load can screw up balance readings with a multimeter / cell-log (the BMS would be applying a small load if its actively balancing too). I assume the readings you are referring to were taken at "rest" w/o the BMS active?

    Andrew
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    dan2l 2014 Prius v wagon

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    Hi Andrew,
    I think you and I are in general agreement. Maybe our differences are from misunderstanding the other persons statement.

    I assume you 0.2v comment comes from my commenting that the "flat" area goes from 3.1-3.3v. What I meant is with a LiFePo4 cell disconnected from everything and at rest, it will be at about 3.1v if its SOC is at the bottom of the flat area. And it will be at about 3.3v if its SOC is at the top of the flat area. In this region smaller variations confound our ability to really know real SOC. I did not mean to infer that those variations were in the range of 0.2v.

    Thanks for your comments. You do help to clarify what I am thinking in many cases.

    Thanks again,
    Dan
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    pbui Member

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    I guess the bottom line is "how do we determine that the balancing is getting done ?" i guess if your delta V increases as the batteries get cycled/used (over many days); then it's not working ?
    Pb
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    DaveinOlyWA 3rd Time was Solariffic!!

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    i have charger balancers on my Zenn. they have lights that flash when they are actively balancing. i take it, yours do not?
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    overlap New Member

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    The BMS has flashing LEDs. (Reminded me of the Holly Hop Drive :))

    5 hours ago I drove approximately 20 miles with the Enginer kit enabled. The battery charging ended at least 1 hour ago. Here is the batteries at-rest voltage. When charging the Hight and Low voltage is "always" 3.46 and 3.36 with an AV of 3.38. Nevertheless, during charging or at rest, there is always a 0.098 to 0.102 volt gap that never reduces.

    TV 53.7 AV 3.35
    1 3.43 H 12 3.34 L
    3.43 3.35
    3.36 3.38
    3.37 3.35
    3.37 3.34
    3.34 3.34
    3.35 3.34
    3.35 3.35
    3.38 3.35
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    dan2l 2014 Prius v wagon

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    Hello overlap,
    Thanks for the data.
    So Cell One is at 3.43v after 1 hour. Based on my experience I would guess that this cell was at 3.8v when the balancer turned the charger off.

    If you leave the system unplugged over night you will see that this cell# 1 will drop to about 3.35 and the others will also drop some.

    Can you leave the system unplugged overnight and then collect the data in the morning before doing anything with the system.

    Thanks,
    Dan
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    JeffreyDV New Member

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    I think something is either wrong with some of my cells or my BMS16C balancer. After using the system for a while I observe on my Scan Gauge that there is no longer any current being provided by the Enginer system. When I check the cell levels on the BMS, I find cells 1-4 all below 3 volts. All the other cells are over 3.2 volts. This has happened about 4 times now. While I am pleased that the BMS is shutting down the system to protect the batteries, I am concerned that the same 4 cells are always the low ones. Shouldn't the balancer keep the cells relatively uniform? Prior to installing the BMS I was using the system and monitoring the cells with CellLogs. I never saw this type of situation, all the cells remained fairly close in terms of voltage. I also find it annoying that the red low battery light does not come on when the BMS shuts down the system. If I didn't have the Scan Gauge I wouldn't know the system was not operating.
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    dan2l 2014 Prius v wagon

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    Hi Jeffrey,
    You can put the CellLogs back on for one Charge/discharge cycle. Then record the data and download the data in LogVeiw and Save the table to XLS file. Then if you Email me those two xls files I can analyze them and give you a good Idea of what is happening.

    I have had the BMS16C on for several weeks now. In my case it seems to slowly bring cells one at a time up to match the highest cell. In the middle of this process it does not look right but in the end it worked very well.

    You can speed this process if you want. To have me help you further, shoot me a PM with your regular Email address.

    Thanks,
    Dan
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    JeffreyDV New Member

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    I didn't disconnect the BMS yet but I wrote down some numbers. The first set is the morning after an overnight charge:
    01- 3.33 02- 3.34 03- 3.34 04- 3.32
    05- 3.33 06- 3.35 07- 3.42 08- 3.42
    09- 3.33 10- 3.35 11- 3.38 12- 3.36
    13- 3.33 14- 3.40 15- 3.47 16- 3.45

    The second is over 24 hours after the BMS shutdown the system:
    01- 2.92 02- 2.77 03- 2.64 04- 1.60
    05- 3.20 06- 3.22 07- 3.26 08- 3.26
    09- 3.24 10- 3.26 11- 3.26 12- 3.20
    13- 3.22 14- 3.27 15- 3.27 16- 3.27

    The system is currently charging.
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    MJFrog Active Member

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    Bank #1 is not good, esp. cell #4. It's in danger of going bad if it hasn't already.
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    overlap New Member

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    I wanted to see more detail about the data and assembled this quick Excel view:

    PriusChatEnginerVoltageFullyChargedToCutOffAndBadBattery.jpg
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    overlap New Member

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    Conclusion: My particular BMS16C's voltage is very inaccurate and I have also NEVER see evidence of it actually balancing cells either in fact or even based off it's fictitious voltage samples that never makes progress based on it's LCD screen. I finally unbolted the Enginer's battery tie-down bars and rotated the battery packs terminal-end-up to have easy access. (After removing the lid from it's hinges.) Completely ignoring variability between in any two volt meters and only looking at the differences between the battery voltage when using any one volt meter, the BMS16C volt meter is very inaccurate and also does not identify the highest or lowest cells.

    Spending hours manually balancing the cells myself and getting the overall pack energy capacity higher than it has ever been, I can see now a quality BMS, Battery Management System might even need to be as expensive as the valuable batteries themselves that it manages and protects.

    I would certainly be willing to pay for a MUCH better balancer than the BMS16C or the Chargery Balancers. Oh yes, of the 3 Chargery Balancers I have, two of them are worthless for the same reason that their relative voltage values across the batteries are at best dis-information :).

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