Jump to content

Inmotion Factory 1.5A Charger Not Cutting Current


WARPed1701D

Recommended Posts

So I have finally had time to mess around with my charge doctor and wanted to to a baseline charge log from what the V8 considers empty (tiltbact and shutdown) to full charge. I sat up last night waiting for the charge to complete and the currrent to drop to 0 and it seemed to take forever. I ended up going to bed and leaving it. I woke up this morning and the charger was still trickling 0.03A into the wheel. Looking at the Charge Doctor website the inventor mentions that his Firewheel charger did this and it is well known that Li-Ion should have the charge stopped unpon completion. Trickle charges are not good for the cells. I've attached the charging graph below. Is this normal? I wondered if the parasitic draw of the Charge Doctor could be fooling the charger to keep the power flowing but another chart of a Gotway wheel by the invetor shows a clear cut off of power from the charger. Anyone care to enlighten me what is going on here. Is this OK. Is this bad.

Background: This is the first time I have logged a charge with the Charge Doctor. I'm going to do it twice with the 1.5A charger and twice with the eWheels fast charger to learn when and how (V or A) to set the Charge Doctor auto-shutoff for each charger (as the curve and constant current/constant voltage transition will move) so I get the charge level and depth of discharge I want. I will post the results when I have them and expect to repeat this in 6 months to gauge battery wear.

ChargeDoctor.png

Additional Info: The light on the charger LED did turn green just before the charge doctor showed 0.05A but it appeared to have no effect on the output.

Link to comment
Share on other sites

No knowledge, just guesses here:

  • I believe my Gotway charger also shows like 0.02A on the CD after finish.
  • This may also be a tiny current coming from the wheel (Test: does the CD stay on if you keep it in in the wheel and then remove the charger from it?).
  • Maybe it's also due to the CD. As it stops at 1.5A by default, that may not be actually full for the wheel. This is why you should ocassionally charge your wheel fully without a CD (and keep the charger in for 20 mins or so after the light went green) so the batteries are 100% full and can then balance (which they may not do after an incomplete charge which one thought was complete).
  • I don't think this is a problem any way. But I'm removing my charger+CD relatively soon after charging (usually to 85%) or the charger when I charge to 100% without the CD, so it's never in there more than an hour or two at most.
  • The BMSes also should stop overcharging by themselves, shouldn't they? @KingSong69 You're going to know that, don't you?

My guess is, the CD does not actually charge to "full" due to the 1.5A stop, and somehow this results in what you see.

Link to comment
Share on other sites

6 minutes ago, meepmeepmayer said:

No knowledge, just guesses here:

  • I believe my Gotway charger also shows like 0.02A on the CD after finish.
  • This may also be a tiny current coming from the wheel (Test: does the CD stay on if you keep it in in the wheel and then remove the charger from it?).
  • Maybe it's also due to the CD. As it stops at 1.5A by default, that may not be actually full for the wheel. This is why you should ocassionally charge your wheel fully without a CD (and keep the charger in for 20 mins or so after the light went green) so the batteries are 100% full and can then balance (which they may not do after an incomplete charge which one thought was complete).
  • I don't think this is a problem any way. But I'm removing my charger+CD relatively soon after charging (usually to 85%) or the charger when I charge to 100% without the CD, so it's never in there more than an hour or two at most.
  • The BMSes also should stop overcharging by themselves, shouldn't they? @KingSong69 You're going to know that, don't you?

My guess is, the CD does not actually charge to "full" due to the 1.5A stop, and somehow this results in what you see.

Thanks for the reply Meep. Some answers to the points you raise.

The V8 appears to have a diode in the charging circuit as removing the charger form the CD while still connected to the wheel kills the CD dead. There is no backfeed from the connector ar at least not enough to run the CD on its own. I tested this before I ran the log.

The CD had the auto-cutoff function disabled during this charge specifically so I could log a normal uninfluenced charge to determine the point at which I want to cut-off in the future for my desired level of charge.

Link to comment
Share on other sites

5 hours ago, WARPed1701D said:

Trickle charges are not good for the cells. I've attached the charging graph below. Is this normal? I wondered if the parasitic draw of the Charge Doctor could be fooling the charger to keep the power flowing

I don't think you are quite realising what is going on here. Lithium Ion chargers do not "drop to zero" they do this:

  • hold the current at the maximum (1.5 Amps in this case). The voltage slowly rises as the cells charge.
  • When the voltage reaches the maximum, hold the voltage at the maximum (4.2 V x no of cells) which should be 84V in this case.
  • As the cell voltages rise closer and closer to 4.2V per cell the current slowly drops.
  • At some point the charger goes from red to green to indicate the battery is charged. This will be triggered by the current dropping to somewhere around 100mA to 200mA. That is all that happens, current continues to flow and the cells continue getting closer to 4.2V.
  • Not all cells are made equal, some will reach 4.2V before others do. The BMS will shunt those cells to halt the voltage increase, allowing lower cells to continue charging like this image.jpeg.3febebec5181b31d2a93e0c708049fd8.jpeg
  • if the charger gets above 84V then when all cells have reached 4.2V all of the BMS shunts will turn on and shunt current around the cells. They cannot handle a lot of current, typically around 30-50mA. If the charger stops at 84V then current will slowly drop to zero, but it is an exponential curve, in theory it will take infinite time to get infinitesimally low.
  • The BMS may cut charging on the input side, but I doubt 84.5V would be enough to trigger that function if it exists on the BMS.
Link to comment
Share on other sites

@Keith

You are absolutely right . I didn't understand the process correctly. This awesome explanation answers my follow on question about how could a BMS balance the cells if the charger cut the power at a specified level. I appreciate the effort in your response.

So basically my BMS was likely shunting power around all the batteries all night long.

 

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

×
×
  • Create New...