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[herculeesjr]

If you've seen my recent posts you know my onboard charger failed, I'm now fully relying on my Charge Tank to do any charging. With this I've lost the convenience of being able to just carry a standard C13 ~10ft cord to plug in wherever a 120v outlet is and now have to carry a ~25ft J1772 charge cable with me on longer trips. This cable is thick and long and takes up almost all space in either a saddlebag or top box, it also disconnects power when the bike is 100% charged which unless someone can correct me if I'm wrong, means I don't get cell balancing with the Charge Tank. Maybe someone can correct me on that if I'm wrong? I just know the onboard charger charges the battery then a couple days later does cell balancing, so the Charge Tank is unable to do that because once at 100% the J1772 box shuts off power to the bike.
So here I have a question... there are guides out there on how to make an open source J1772 charger cable at whatever length you want and all remain 100% to J1772 spec meaning they cut power at 100% charge. I am wondering, and I know many of you won't like this question, if it would be feasible to create one that does not include a relay that disconnects power and instead has a 20a manually actuated power switch. I'd still obviously have circuitry that informs the bike it can charge up to 15a 120v, and this power would remain on till I manually flip the switch off, thus allowing the Charge Tank to remain on for cell balancing.
So could I make a slightly dumb (and yes I know more dangerous) J1772 charge cable that remains powered until I shut it off, or would this throw up an error or something due to J1772 standards? I'd want to make it as a J1772 connector - ~1ft cable - waterproof controller box with switch - ~1ft cable to C13 connector - however long C13 cord I need (I have a 3ft, 6ft, 10ft, and 25ft) for where I'll be. I look forward to hearing how doable this is or how wrong I am!

[Crissa]

No, the cell balancing happens immediately at 100%.  It should still be happening if you leave it connected for a little while at 100%.  That's part of the taper.

There's no reason the granny cable should shut off, it doesn't know what power the vehicle is at.  However, it would want to shut off for while you're plugging it in and out to reduce arcing, perhaps that's what you're noticing?

-Crissa

[herculeesjr]

No, the cell balancing happens immediately at 100%.  It should still be happening if you leave it connected for a little while at 100%.  That's part of the taper.

There's no reason the granny cable should shut off, it doesn't know what power the vehicle is at.  However, it would want to shut off for while you're plugging it in and out to reduce arcing, perhaps that's what you're noticing?

-Crissa

From my experience with the EVSE cable I bought (https://www.amazon.com/gp/product/B07HH4LJD2/) once the bike hits 100% charge it shuts off power to the bike, however I'm not sure if that's immediately at 100% or if cell balancing happens and then it shuts off hours later. From there you have to key the bike on to restart the charging process as the battery relay has now opened, not that I do that as it's already fully charged.
I know it's shut off as the battery relay is open, dash is completely off, and the display on the charger says "Ready" which is what it says when unplugged from the bike instead of "Charging/Charged".

[DonTom]

If you've seen my recent posts you know my onboard charger failed, I'm now fully relying on my Charge Tank to do any charging. With this I've lost the convenience of being able to just carry a standard C13 ~10ft cord to plug in wherever a 120v outlet is and now have to carry a ~25ft J1772 charge cable with me on longer trips. This cable is thick and long and takes up almost all space in either a saddlebag or top box, it also disconnects power when the bike is 100% charged which unless someone can correct me if I'm wrong, means I don't get cell balancing with the Charge Tank.

Cell balancing starts at around 90% SOC. So your cells will still get balanced just fine with the charge tank.


You can make your granny cable much shorter. See here.


-Don-  Reno, NV

[herculeesjr]

If you've seen my recent posts you know my onboard charger failed, I'm now fully relying on my Charge Tank to do any charging. With this I've lost the convenience of being able to just carry a standard C13 ~10ft cord to plug in wherever a 120v outlet is and now have to carry a ~25ft J1772 charge cable with me on longer trips. This cable is thick and long and takes up almost all space in either a saddlebag or top box, it also disconnects power when the bike is 100% charged which unless someone can correct me if I'm wrong, means I don't get cell balancing with the Charge Tank.

Cell balancing starts at around 90% SOC. So your cells will still get balanced just fine with the charge tank.


You can make your granny cable much shorter. See here.


-Don-  Reno, NV

Oh okay, I did not know it started around 90%. I thought it required a full charge and resting period before it could do cell balance, like the onboard charger does. Well that's good to know then that there's different methods with different chargers.

I've looked into modifying the EVSE to make the cord shorter, but I was interested in building my own in hopes of it being cheaper instead of spending another $150-$200 just to cut it open and shorten the cable. Basically leave one at home mounted to the wall, then a compact portable one for on the go.

[DonTom]

Oh okay, I did not know it started around 90%. I thought it required a full charge and resting period before it could do cell balance, like the onboard charger does. Well that's good to know then that there's different methods with different chargers.

I've looked into modifying the EVSE to make the cord shorter, but I was interested in building my own in hopes of it being cheaper instead of spending another $150-$200 just to cut it open and shorten the cable. Basically leave one at home mounted to the wall, then a compact portable one for on the go.

It still needs to get to 100% SOC to complete the cell balancing. It ends just before the contactor opens or stays at 100% SOC for a while. Perhaps five minutes if the contactor is still closed after hitting 100% SOC. But 100% SOC  on the display varies by quite a bit, so could take a little longer.


You can modify the cable you now  have, most likely. No need to buy another. First take it apart to see how easy it is to modify. They are not all the same, some are more difficult than others. I have done a few of them. I have yet to find one that could not be modified for a much shorter cable. No need to modify the input  side, which is much thinner anyway and that will add length to your extension cable. You can still use the modified cable at home.


But if you do buy one, make sure it can handle the capacity of your charge tank if you want to be able to charge at the full rate. And then look for the smallest  in physical size.


-Don-  Reno, NV

[Richard230]

I watched my bike with the OBC charge last week as it was connected to a Kill A Watt meter, as I have done several times previously. My bike did not taper the charge. The current kept on increasing to just under 13 amps and then the power shut off immediately about 20 minutes after hitting 100% SOC and then showed 11 watts on the meter at which time I pulled the power cord.

Perhaps it tapers the charge every certain number of charges and I just don't happen to see it happening. Or perhaps the cells are so well balanced that the BMS doesn't feel the need to balance out the battery pack.  I was expecting to see some obvious cell balancing as I used to see when I owned my 2014 S, but so far I have not seen that activity with my 2018 S. Both bikes have a PT.

[DonTom]

I watched my bike with the OBC charge last week as it was connected to a Kill A Watt meter, as I have done several times previously. My bike did not taper the charge. The current kept on increasing to just under 13 amps and then the power shut off immediately about 20 minutes after hitting 100% SOC and then showed 11 watts on the meter at which time I pulled the power cord.

Perhaps it tapers the charge every certain number of charges and I just don't happen to see it happening. Or perhaps the cells are so well balanced that the BMS doesn't feel the need to balance out the battery pack.  I was expecting to see some obvious cell balancing as I used to see when I owned my 2014 S, but so far I have not seen that activity with my 2018 S. Both bikes have a PT.

There is no need for it to taper off when at only 1.3 kW.  You would see it taper off if you were charging at 6KW. Near the end of that 6 KW charge, it will be below two KW, not much different than you have with only the OBC.


Near the end, it's all about the same no matter what your charge with.  Even when I use a 25KW CCS charge on my Energica, which is 25KW in the mid range, it will be around two KW at 99% SOC.  I can watch the slow down start at around 80% SOC and it's obvious and progressive dropping in power from there. Perhaps 15 KW at 80% and 10KW at 90% SOC but around 2 KW at 99%.  Now you know why they rate charging to 80% SOC. 


-Don-  Reno, NV