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LiFePo4 BMS testing

Discussion in 'QRP Corner' started by KC3AJV, Mar 18, 2021.

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  1. KC3AJV

    KC3AJV Ham Member QRZ Page

    I sent an email to TalentCell last night and had a reply this morning. They stated that the max amperage the battery can handle for charging is 12A - I never came anywhere near that.

    My first email to them was short, and did not contain much information. Their reply was about the same, as expected.

    Dear Robert,

    Maximum charge current is 12A.

    Please check if charging current more than 12AH.

    Best Regards
    Name Removed
    TalentCell Technology

    I sent a follow up email with details about the charger, monitor, and load, and explained what I am seeing the battery do. Hopefully they will send another email and let me know what they think is going on.
     
  2. KC3AJV

    KC3AJV Ham Member QRZ Page

    I came in to work a little early to mess with this some more, and hooked up a few more resistors in parallel.
    R1 - 28ohm 100W
    R2 - 30ogm 50W
    R3 - 28ohm 50W
    R4 - 10ohm 50W

    Rt = 4.16ohm calculated
    Rt - 4.6ohm measured with DMM

    The battery has no problem spitting out 2.97A @ 13.0V

    This is starting to baffle me.

    Additionally, I put a meter in line, with fuses, between Batt #1 and the 706. The 706 draws between 20-80mA when I connect it to the battery (I'm guessing that is the relay coil), and draws 1.2A when I power it on with no mic or antenna connected. For sanity, I tried hooking Batt #2 back up again and same deal, no dice. The 706 tries to draw a few mA from the battery (as seen on the DMM) but then the juice dies. Grrrrr.
     

    Attached Files:

    Last edited: Mar 19, 2021
  3. KA9JLM

    KA9JLM Ham Member QRZ Page

    Have you looked at the charts for that battery ?

    A regular SLA charger should work just fine. I use a 4 amp for small batteries like that.

    upload_2021-3-19_8-22-29.png
     
  4. KG7WGX

    KG7WGX XML Subscriber QRZ Page

    Here is what I think is a good treatment of the question of what types of chargers should be used with LiFePO4 -

    https://www.power-sonic.com/blog/how-to-charge-lithium-iron-phosphate-lifepo4-batteries/

    It does address the "drop in" SLA replacement pitch for this type of battery, and goes into some depth on what kinds of SLA chargers will be OK for the battery. From this reference -

    If using a constant voltage SLA charger, the charger must meet the following conditions:

    * Charger must not contain a de-sulphating setting
    * Fast charge voltage of 14.7v
    * Recommended float charge of 13.8v

    As a side note, some smart or multi-stage SLA chargers have a feature that detects open circuit voltage (OCV). An over-discharged lithium battery that is in protection mode will have an OCV of 0. This type of charger would assume the battery was dead and would not try to charge it. A charger with a lithium setting will try to recover or "wake up" an over-discharged lithium battery.

    I think all you can get from the chain of events is that an improper charger was used and now you have what appears to be a damaged battery.

    Why not wait until the correct charger shows up and see if it can "wake up" the battery?
     
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  5. KC3AJV

    KC3AJV Ham Member QRZ Page

    I guess my burning question at this point, is why the battery will happily supply 2+ amps to a parallel resistor load, but konks out when connected to a lesser load of the 706?

    I'm still hoping TalentCell replies, and I can speak with them about it.

    I'll happily admit I am not a battery, or electronics wiz, and there may be a simple reason why the battery is not performing - but I sure don't know why.

    I guess at this point, I'll wait for TalentCell for a reply and get a charger specifically made to charge LiFePo4 batteries.

    I don't know nearly enough about batteries to know what the charts mean. Any ideas why the battery will send amps to resistors but not a radio?
     
  6. KA9JLM

    KA9JLM Ham Member QRZ Page

    Bad fuse holder or power cord would be my guess. Maybe the protection diode in the radio is bad.

    The battery does not send amps unless the radio request it. The resistors will request what PIE says.

    Good Luck. You can figure it out.
     
  7. KC3AJV

    KC3AJV Ham Member QRZ Page

    As an update, after speaking with a representative from TalentCell it was determined that the battery is bad. I sent them links and info to the equipment I added and the charger I used to charge the battery. They let me know that nothing I did or equipment I used should have caused the failure. For information purposes they said the battery can handle charging of up to 12 amps. I don't think I would recommend that, or at least not often. Maybe a once in a while rapid charge. Then again, I am not a battery expert so what do I know.

    TalentCell is shipping me out a new battery at no cost to me. Some Amazon reviews claim horrible customer service. Here is what I did - this is over the course of 6 days and 16 emails (most of them from me to them for troubleshooting and support info).

    -Contact TalentCell via their website 'Contact Us' link
    -Representative reached out and asked me to explain how the battery was behaving
    -I explained in detail
    -Representative asked to know what equipment I added, what charger I used, and what load I was trying to power
    -I sent links to equipment and Icom 706MkIIg
    -Representative explained battery performance and that nothing I did should have caused failure. Representative asked for video of how I am charging. I thought this was kind of excessive, but also appreciated their due diligence
    -I sent video of how I was charging, how the bad battery #2 was performing, and how the good battery #1 was performing
    -Representative let me know the battery was bad and they would send me a new one free of charge
    -I asked for shipping details
    -Representative provided shipping details

    I should have the new battery by the 3/29/2021
     
    KA0HCP, K7WFM, KA9JLM and 1 other person like this.
  8. KC3AJV

    KC3AJV Ham Member QRZ Page

    Another update for anyone interested in these batteries.

    Turns out a capacitor, C6, got knocked off the BMS pcb, causing the performance failure. This is something that certainly should have been caught after final assembly. Fortunately I have some of the skills necessary to troubleshoot and repair this battery, but others may not.

    TalentCell did the right thing, and is replacing the battery; however, good manufacturing would have prevented me needed good customer support. It worked out in the end for me, now I'll have 3 batteries, but it easily could have been a manufacturing error that I could not repair.

    Just sayin'
     

    Attached Files:

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