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  • Scoonie
    replied
    Originally posted by DubP View Post
    What is an expected amount of sag from a battery like this? I have a similar battery, 13S 9P, and when I go to full load (20A) my voltage meter drops from 52V to 43V. I still get good power and range, but I think that is way too much drop?
    Any more info on the pack?From? Cells used?

    Leave a comment:


  • JPLabs
    replied
    Well, that's a lot. Look how close you get to LVC with a nearly full pack. At 40A my pack drops maybe 6-7V if it's full and cold, hard to say since I just know peak current and minimum voltage, but something like that. At 20A it's just a few volts. There is no right or wrong, no 'proper sag' but the more you have, the earlier you hit LVC, so the less power you can use and still drain the pack low.

    For a given pack the sag will vary mostly with current, and temperature of the cells. More current, colder, both mean more sag. And it increases with age.

    Leave a comment:


  • DubP
    replied
    What is an expected amount of sag from a battery like this? I have a similar battery, 13S 9P, and when I go to full load (20A) my voltage meter drops from 52V to 43V. I still get good power and range, but I think that is way too much drop?

    Leave a comment:


  • JPLabs
    replied
    Cool, charged and balanced, then, thanks. So, I think it's likely your cutouts at higher loads will stop, or be less frequent, anyway. Sag affects the weakest group, and is dependent upon charge level, too. You brought up the weak groups, so will have a bit more reserve voltage for high power pulls, now. But as noted, that looks like a high resistance pack design, so sag at high currents will tend to be an issue. More connection resistance, more sag, more cutouts at higher charge levels, compared to a pack with low resistance current paths.

    Leave a comment:


  • Schrockie71
    replied
    53.9v + on the pack.

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  • JPLabs
    replied
    Originally posted by Schrockie71 View Post
    Bought a Luna 48v advanced charger, Did a hard reset on the BMS and got that working again. All batts were within 0.05mah of each other, my battery gauge on throttle showed full power and yet it is still cutting out. Could the controller be causing this?
    I think you mean they were withing 0.05 millivolts of each other, right?

    If so, great, it's balanced. But is it also charged up? You didn't mention the pack voltage. Could just be low?

    Guys, when asking about battery issues, PLEASE tell us the pack voltage. It gets tiring asking all the time.

    Leave a comment:


  • Schrockie71
    replied
    Bought a Luna 48v advanced charger, Did a hard reset on the BMS and got that working again. All batts were within 0.05mah of each other, my battery gauge on throttle showed full power and yet it is still cutting out. Could the controller be causing this?

    Leave a comment:


  • max_volt
    replied
    My batt up and died. Took it apart and found a tidbit of plastic wrap in the power switch. Lucky it has holes in it so I could see before i jumped it out.

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  • Scoonie
    commented on 's reply
    If you didn’t order a bms with balancing function a monitored 6-8 hour charge should do a pretty good job. Never charge long term unattended IMO. Amazon is a fast source for kit.
    Last edited by Scoonie; 12-04-2017, 11:22 PM.

  • max_volt
    commented on 's reply
    That's an XLR connector. Popular in audio.

  • Schrockie71
    replied
    Received new BMS today and installed it then went to charge and still had a green light indicating a full charge(which its not). I am now in the market for a good reliable charger, 48v 13s with 3 prong male barrel connector and American style wall socket. Preferably something in the U.S. so I don't have to wait 2-4 weeks for delivery. One more question, do I need a balancer/ charger or will the BMS do the balancing?

    Leave a comment:


  • Schrockie71
    replied
    Thanks everyone for all the response!!

    JPLabs
    It was fully covered with duct-tape, I just opened it up to look for problems and measurebattery voltage of individual parallels.

    Scoonie
    How many bridges should I add to connecting rows? Can I just solder on some jumpers, what size wire gauge? VPower built this setup.

    max_volt
    Ordered another 20amp BMS, same design you have in your pic.

    Can anyone recommend any sites to get a decent battery pack. without killing my wallet?

    Thanks again folks,
    Schrockie71

    Leave a comment:


  • JPLabs
    replied
    Originally posted by Scoonie View Post
    Actuallythats a poorly designed pack. Nowhere nesr enough bridges between parallel groups. Paxtana pointed out. 1 problem,and the third problem after build andsag is balance. Who built that mess?
    Hey, that's a real good observation, I think you are right. All the pack current has to go through a single grouping of (sparse) tack welds, a dozen times, just to get out! Tiny surface area, thus high resistance.

    That pack is doomed to sag with high currents, compounding any other issues.

    Way to make a strong first impression, newbie! Nowjus twork onyourtaping a little bit. There's an edit button once your post shows up, in case you didn't notice that. ;-)

    Last edited by JPLabs; 12-03-2017, 08:12 AM.

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  • max_volt
    replied

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  • max_volt
    replied
    I have the same pack that i bought by accident. Marked as 20ah it works on my mtb but cuts off on the fattie. Possible off brand 2200mah cells. vpower can offer a good price but spotty quality. The 6a charger smelled very burnt so he is sending a new one.

    Prolly ok for 750w but over 1000 is pushing it.

    Schrockie71 what amp bms did you order?
    Last edited by max_volt; 12-03-2017, 06:25 AM.

    Leave a comment:

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