EBike Quick Charge: Ultra-fast charging battery to substitute for Specialized SL Extender battery? Logarithmic Charging Strategy.


Active Member
I would like to build a portable 1 to 2kW car electrical system around scooter components. Scooters have fast charging. The following picture illustrates my goal. Charge a battery from EV J1772 stations for use with camping appliances like water heater, conventional 110V outlets, radiant heaters, etc.....

The Vectrix charger has a cooling fan and heat sinks, as explained in the second video. That gives me pause.

I have a feeling that I cannot use J1772 as i would like. J1772 has its own protocol. I suspect there might not be generic batteries that can be charged from EV charging stations.

I wonder how difficult fast charging is to implement for eBikes? TQ has clearly implemented it. I am forming the impression that Specialized will be late with its fast charging implementation. Fast charging seems complex to implement and test.

Why do scooters charge using XLR plugs, rather than Mosenberger used on eBikes?

I know from audio, the XLR have balanced inputs, they are grounded differently from conventional line inputs. XLR can detect errors and filter out noise.

The more I investigate fast charging for eBikes, the less I like it.

DC fast charging is more complex in that it must evaluate the condition of the battery and apply a charge level that the battery can safely absorb. A cold battery must be charged slower than a warm one; the charge current must also be reduced when cells develop high internal resistance and when the balancing circuit can no longer compensate for cell mismatch. (See BU-410: Charging at High and Low Temperature)

DC Fast Charging is not designed to fill the battery completely but to allow the vehicle to reach the next charging station. Using Level 2 is the preferred routine for everyday charging.

Level 2:
7kW typical

Wall-mount; 230VAC, 30A two pole, charges a mid-sized EV in 4 to 5 hours. This is the most common home and public charging station for EVs. It produces about 7kW to feed the 6.6kW on-board EV charger. The cost to install a Level 2 EVSE is about $750 in materials and labor. Households with a 100A service should charge the EV after cooking and clothes-drying to prevent exceeding the allotted household power.

EV driving range per minute charge: 670m (2,200 feet)


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Active Member
The thought just occurred to me that storing lithium batteries inside a car is unsafe. Temperatures can exceed 170F when a car is parked in the sun. Could these conditions cause lithium batteries damage or make them explode?

170F is hot enough to sanitize a car from covid19.
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Active Member
  • 42V = ten, 4.2V cells connected in series, for current chemistry.​
  • Amperage equates to number of cells connected in parallel​
    • Specialized Extender weakness is 3A configuration​
      • A 9A charger means a fundamentally different cell configuration, tripling parallel connections.​
      • The Extender fits into a cylindrical container, limited by bottle cage.​
    • The main battery is constrained by downtube dimensions.​
      • 42V is ten batteries in series, which is probably exhausts downtube length.​
      • The amperage is limited by downtube diameter, which is also likely exhausted.​
  • A fast charging system for the Creo seems very unlikely in the near future.

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Active Member
I can't use lithium cells for a portable electric system, because temperatures can approach freezing at the places and time when I hope to use them.

Another safety issue is cold temperature charging. Consumer grade lithium-ion batteries cannot be charged below 0°C (32°F). Although the packs appear to be charging normally, plating of metallic lithium occurs on the anode while on a sub-freezing charge. The plating is permanent and cannot be removed. If done repeatedly, such damage can compromise the safety of the pack. The battery will become more vulnerable to failure if subjected to impact, crush or high rate charging.

No lithium remains in the cathode of a fully charged LiFePO
4 cell. (In a LiCoO
2 cell, approximately 50% remains.) LiFePO
4 is highly resilient during oxygen loss, which typically results in an exothermic reaction in other lithium cells.[11] As a result, LiFePO
4 cells are harder to ignite in the event of mishandling (especially during charge). The LiFePO
4 battery does not decompose at high temperatures.[17]
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