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Kevin Graehl

Kingsong internal charger mod 18xl. USBC MacBook input. 87 watt convenience.

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I hate brick chargers.    Now I can charge by plugging in common MacBook usbc or generic usbc chargers.   Or plug into a car cigarette lighter.     Still can use OEM 150 watt charger.      I rarely go past 50 percent battery.  So I'm happy with the slower charging speeds.   

 

Can be adapted to ebikes, onewheels, skateboards.   

Screenshot_20190419-220045_Photos.jpg

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While you have done very precise work, I would think that the MacBook power supply doesn’t offer the kind of constant current - constant voltage switching that the Li-ion batteries on an EUC require from a charger. While laptop batteries are also Li-ion, the charging goes through the laptop mainboard, which in my understanding takes care of the charging process.

I would at least make sure not to charge up to 84V, and let the original charger do the cell balancing every now and then.

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?  Bms is intact.   I'm simply applying 84.1 volts to input of BMS.   Nothing special.  

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8 hours ago, mrelwood said:

I would at least make sure not to charge up to 84V, and let the original charger do the cell balancing every now and then.

Cell balancing is done by the BMS, not the charger. From my latest readings most presumably while the CV phase and maybe already a bit before. But should mostly depend on the specific BMS design. Like with cell overvoltage charge input shutoff at some fixed cell voltage threshold a resistor is put in parallel to reduce charging current for this cell. Batteryuniversity.com states/?recommends? some 70-80% state ot charge for doing this. Afair 80% SoC is just at the change from CC to CV?

43 minutes ago, Kevin Graehl said:

?  Bms is intact.   I'm simply applying 84.1 volts to input of BMS.   Nothing special.  

If one applies 84.1V to the input of the BMS with not full batteries that's one of the secure ways to destroy the cells and/or the BMS - depends on whats the weak link.

I assume your ?step up converter? Has some current limiting and so acts like a constant current source until the battery pack is reaching 84V?

 

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Posted (edited)

clearly you don't understand how fixed switching power supplies work.   Or i need to go back to school.   Every wonder why a car battery alternator puts out 14 volts, but a half charged battery slowly climbs from 12 volts, to 12.2, 12.4 etc until it reaches the 14 volts?  

 

yes, current limiting..   I'm simply limiting current to 70 watts.  voltage is free to move around *set at a max of 84.1 volts  .

Edited by Kevin Graehl

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Posted (edited)

As far as I can tell, the unicycle chargers aren't "smart" and doing a CC/CV charge, but just current-limited DC supplies which produce the same effect since its running at limit for the first 90%, and above 90% the voltage difference is so small that the current flow begins decreasing.

 

I've messed around with using 2 chargers in parallel, and there's no "communication" period when you plug them in to determine the battery state, you can connect and disconnect them arbitrarily and see the current flow respond organically, (like, it'll increase even if it's dropped to just 0.5A on one charger, if you plug in the second it'll jump to 0.75) as if they're just plain DC supplies.

 

Therefore, most current-limited DC-output circuits will perform a CV/CC charge just as an emergent property of how  the circuitry works.

Edited by tudordewolf

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