1 hour charging (6.6kW) gives more than 25% capacity

I'm usually charging at my company using a 6.6kW charger.

Say an optimistic charging efficiency of 90%, then an hour charging would give around 6kW.

6kWh is 25% of LEAF batter, 24kWh.

However, my observation is that an hour charge gives more than 25%.

For example, today the batter was at 20%. After an hour charging, the battery showed around 58%.

Was my math wrong? Or, can the charger provide more ampere? (The charger shows the wattage, around 6.5-6.6kW)

My another speculation is LEAF shows the remained battery percentage in a non-linear way: for an instance, 20% battery is actually 35% or so.

Is there anyone who has a similar experience?

carolle said:

I'm usually charging at my company using a 6.6kW charger.

Say an optimistic charging efficiency of 90%, then an hour charging would give around 6kW.

6kWh is 25% of LEAF batter, 24kWh.

However, my observation is that an hour charge gives more than 25%.

For example, today the batter was at 20%. After an hour charging, the battery showed around 58%.

Was my math wrong? Or, can the charger provide more ampere? (The charger shows the wattage, around 6.5-6.6kW)

My another speculation is LEAF shows the remained battery percentage in a non-linear way: for an instance, 20% battery is actually 35% or so.

Is there anyone who has a similar experience?

Click to expand...

Your are mixing your terminology, and without a CAN buss reader (leaf spy, etc.) you really cant quantify the Battery Voltage and SOC accurately.
The "Charger" is contained in the Car.
If you have a "6.6" Kw charger in the vehicle, it outputs about 6.0Kw to the batteries.
Yes, the EVSE you plug into can output a variety of rated current deliveries, which are negotiated between the vehicle and the EVSE at the start of charge.
We have seen in the real world that as the voltage of the pack increases, the Kw delivered decreases . (output remains "constant" so as 1 increases, the other decreases)

If I remember correctly, the leaf can only access about 21Kw of it's capacity, so 25% of that would be 5.25Kw, again, depending on where in the voltage spectrum you happen to be.

If you get access to a DCQC that has some nice readouts, you can actually watch this happen in real time.

BTW, there are LOTS of threads om here that deal with charging.

Only around 21.5 Kwh of the battery is usable... Also, the OBC is 6.6Kw input but only 6.0Kw output to the battery... Nissan cheated a little by changing the spec to input power on the 2013+ unlike the 2011/12 that was output power...

carolle said:

6kWh is 25% of LEAF batter, 24kWh.

Click to expand...

Your battery will charge even faster in percentage of charge terms as it's capacity degrades. Trouble is, it will also discharge faster as well.

It's also not unusual for voltage to vary, usually -5% to +5% from nominal (240V), but it can be as extreme as -13% to +6% and still fall within spec. So it's possible to charge the LEAF at 254.4V. This would provide a faster-than-spec charge (27.5 * 254.4 from the wall = 7kW vs 6.6kW nominal).

I get 250V at my house (but haven't been charging at level 2 since my OpenEVSE melted due to crappy fuses). Work is closer to 238V.

KillaWhat said:

carolle said:

I'm usually charging at my company using a 6.6kW charger.

Say an optimistic charging efficiency of 90%, then an hour charging would give around 6kW.

6kWh is 25% of LEAF batter, 24kWh.

However, my observation is that an hour charge gives more than 25%.

For example, today the batter was at 20%. After an hour charging, the battery showed around 58%.

Was my math wrong? Or, can the charger provide more ampere? (The charger shows the wattage, around 6.5-6.6kW)

My another speculation is LEAF shows the remained battery percentage in a non-linear way: for an instance, 20% battery is actually 35% or so.

Is there anyone who has a similar experience?

Click to expand...

Your are mixing your terminology, and without a CAN buss reader (leaf spy, etc.) you really cant quantify the Battery Voltage and SOC accurately.
The "Charger" is contained in the Car.
If you have a "6.6" Kw charger in the vehicle, it outputs about 6.0Kw to the batteries.
Yes, the EVSE you plug into can output a variety of rated current deliveries, which are negotiated between the vehicle and the EVSE at the start of charge.
We have seen in the real world that as the voltage of the pack increases, the Kw delivered decreases . (output remains "constant" so as 1 increases, the other decreases)

Click to expand...

Yep, OP needs to get the EVSE vs. charger straight. See http://www.mynissanleaf.com/viewtopic.php?f=6&t=14728&p=332668#p332668" onclick="window.open(this.href);return false;.

If the EVSE's display shows 6.5 to 6.6 kW, it's likely the line voltage is at/close to 240 volts.

At my work, I've confirmed w/the Chargepoint techs (who came on site) that our line voltage is 208 volts, so it's not surprising my Leaf typically draws ~5.8 to 6.0 kW on our Chargepoint EVSEs.

Re: the negotiation, from what I understand from https://code.google.com/p/open-evse/wiki/J1772Basics" onclick="window.open(this.href);return false; and some other readings, the duty cycle of pilot emitted by the EVSE indicates to the vehicle how many amps at max it can draw. The vehicle's on-board charger must draw no more than the amount indicated by the pilot.

Also given the power sharing capability of http://insideevs.com/chargepoint-introduces-ct4000-series-charger-with-unique-power-sharing-option/" onclick="window.open(this.href);return false; and https://code.google.com/p/open-evse/wiki/Hydra" onclick="window.open(this.href);return false;, the pilot emitted can change at anytime.

And yes, the Leaf's battery has about ~21 kWh usable, when new. And, not all of the energy that makes it out of the wall makes it into the battery, due to charging overhead. http://www.mynissanleaf.com/viewtopic.php?p=155305#p155305" onclick="window.open(this.href);return false; has some charging efficiency figures. Does anyone have them for '13+ Leafs w/6 kW OBCs, esp. near 30 amps?