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[DonTom]

That is NOT how a CC/CV power supply works. The bike is never supplied with voltage above the final charge amount. What happens is its supplied at the constant current limit, until the charger hits the max voltage. then the current slowly drops as the voltages come closer. At no point is the output voltage of the charger raised above that battery max to increase the current.

Actually, it is exactly  how a Constant Current power supply works. It changes the voltage as necessary to keep the current constant. But the battery will drop the voltage, but the voltage always has to be a bit higher then the battery resting voltage or else there is no charging and no current.

A 100 volt battery "charged" at 100 volts  means ZERO current. The current draw has to be from the charger having more voltage than the battery resting voltage. That is what creates the current draw to charge the battery.

Constant current supply  means the power supply voltage changes with the varying load to keep the current constant.   Without CC, the current draw would change  as the battery SOC changes.

BTW, I do realize it's a bit more complicated as stuff such as battery temperature is taken into consideration in our E-vehicles, which will also change the charging current (by lowering the voltage to lower the charge current). IOW, CC might not always be so CC.

-Don-  Reno, NV

[DonTom]

I did some more testing today.

My 2017 DS ZF 6.5 was indicating 85% of the charge left after a ten mile ride.

The resting voltage of the battery was  then 110.3 volts.

Adding a quick charger (withOUT the on-board charger) the voltage is 111.3 volts.   A one volt increase.

Adding the onboard charger (now both chargers) the voltage is 112.9 volts. 1.6 volt more increase.

So with both chargers, the battery voltage is 2.6 volts above the battery resting voltage, under the load of the battery.

I expected the charging voltage to be a bit higher voltage above the battery resting voltage, considering the current these batteries  draw.

But at least we now know our "96 volt chargers" are really  more than 11 volts  above the battery voltage if no load. IOW, 117 volts or above.

The no load charger voltage cannot be tested as these Zero quick chargers need voltage from the battery to turn on. They measure zero volts when not connected to the battery.

But we do know that the battery does charge to  above 117 VDC when at 100% charge is indicated, proving the charger voltage has to be at least a slight bit above that.

I also realize other things can effect these readings, others might get slightly different readings based on  SOC, battery temps, or whatever. But one thing for sure is that our 96 volt chargers are quite a bit higher than 96 volts. And our batteries charge to around 117 VDC, so the charger's unloaded voltage has to be even higher than that. But that unloaded voltage cannot be easily tested.

-Don-  Reno, NV

[togo]

> ... the battery will drop the voltage, but the voltage always has to be a bit higher then the battery resting voltage or else there is no charging and no current.

A 100 volt battery "charged" at 100 volts  means ZERO current. The current draw has to be from the charger having more voltage than the battery resting voltage. That is what creates the current draw to charge the battery.

Constant current supply  means the power supply voltage changes with the varying load to keep the current constant.   Without CC, the current draw would change  as the battery SOC changes.

> BTW, I do realize it's a bit more complicated as stuff such as battery temperature is taken into consideration in our E-vehicles, which will also change the charging current (by lowering the voltage to lower the charge current). IOW, CC might not always be so CC.

Actually I don't think there's a mechanism to communicate to external chargers to slow charge rate due to battery temp. If you hit the battery temp limit, the contactor opens, and everything stops till it cools. And on an older bike there's a fair bit of air gap insulation, on a hot day you are stuck for a while. Better to catch it before it happens, because riding at 55mph cools the battery better than being stationary.

> But we do know that the battery does charge to  above 117 VDC when at 100% charge is indicated, proving the charger voltage has to be at least a slight bit above that.

No. You'd damage the battery.  But hopefully the self preservation circuitry would kick in, the contractor would open.

When the supply hits 116.5v it switches to constant voltage mode, the current drops, and the battery voltage sags and the current thus increases again, reaching an equilibrium where you are feeding into the battery at the shower rate, *not* exceeding the voltage. Charging slows as you reach 100% SoC. If you were to charge rapidly to 116.5v, and stop, you'd end up with an immediate sag of a volt or two and like 90% SoC once the battery has rested. I do this fairly often (To avoid being at 100% SoC. I live at the top of a hill, and don't like having regen disabled.)

...
> And our batteries charge to around 117 VDC,

Yes

> so the charger's unloaded voltage has to be even higher than that.

No

> But that unloaded voltage cannot be easily tested.

I've watched it with a voltmeter under charge. Heck I monitor voltage from the mbb interface fairly regularly (diginow dongle). Doesn't exceed 117v. It flattens there and current tapers accordingly.

[MrDude_1]

Actually, it is exactly  how a Constant Current power supply works. It changes the voltage as necessary to keep the current constant.

yes, that is how a Constant Current power supply works, HOWEVER all Zero motorcycles (and lithium batteries for that matter) are charged with a Constant Current AND Constant Voltage power supply.. thats the CC/CV in my quote.

The way it works is simple. On any load below the current threshold, the supply stays at the set voltage. As the load increases beyond that, the current limiter kicks in and lowers the voltage.

But the battery will drop the voltage, but the voltage always has to be a bit higher then the battery resting voltage or else there is no charging and no current.

A 100 volt battery "charged" at 100 volts  means ZERO current.

You are not incorrect. However I think you have a bit of a logical issue there. If the battery is fully charged at 100v, and its at 100v, then of COURSE there is no current flowing. the battery is fully charged!

However if the power supply is at 100v, but the battery is still at 99v, current is still flowing, but only a tiny trickle... that is the entire reason why you can charge an EV to about 85% at high rates, but it slows down topping to 100%, as you get closer, it charges slower!

Instead of these made up numbers, lets use the Zero's actual battery.
The zero battery has 28 cells, meaning if each cell was at 4.15 as charged, the pack voltage is 116.2.
Once you reach a current level that is below the factory chargers level, an extra external charger is not required. Its not going to make it any faster.. so you dont have to worry about setting it at exactly 116 point something.. just have it around 115 and then you dont need to worry about your multimeter being perfect. Or if you're after that last 30seconds of saved time, set it to 116 on the nose with a calibrated fluke meter after the length of the leads... whatever floats your boat.

Constant current supply  means the power supply voltage changes with the varying load to keep the current constant.   Without CC, the current draw would change  as the battery SOC changes.

The current draw DOES change as the battery charges. It stays at whatever the chargers current limit is, until the voltage limit is reached, then the current drops as the voltage stays constant.
Alot of people think this is some how programmed in, but its actually just those two limits being reactive to the load given by the battery.
Super simple.
The hard part is handling the error conditions... for example, on a switching power supply if you suddenly disconnect the load, you can get some nasty spikes... enough to play pop-goes-the-FET.

BTW, I do realize it's a bit more complicated as stuff such as battery temperature is taken into consideration in our E-vehicles, which will also change the charging current (by lowering the voltage to lower the charge current). IOW, CC might not always be so CC.

-Don-  Reno, NV

nope. the BMS handles all that. If the battery is too hot or too cold to accept the charge, it just disconnects the contactor and your supply does nothing... it also disables the enable signal right before the contactor, but not everyones charger pays attention to that (although they should)

[DonTom]

I took some more readings today. Here is what I discovered on the Anderson Connector while only the onboard charger is used:

Percent of charge indicated:96 %=114.5 VDC.   98%=115.2 VDC, 99%=115.5 VDC, 100% (Green charge indicator still blinking)=115.8 VDC

3 minutes later=116.1 VDC

4 minutes more (indicator solid on) 116.5 VDC.

5 more minutes= 117.0 VDC

15 minutes later (bike still plugged in)= 1.0 VDC  (this must mean the contactor relay opens well after the green light is solid, not at the same time).

Plug removed=0.6 VDC

Plugged back in (key still off) 116.8 VC  Many minutes later voltage drops (dropping below 40 VDC when I checked).

Unplugged bike, key on=  116.7 VDC

-Don-  Cold Springs Valley, NV

[DonTom]

The way it works is simple. On any load below the current threshold, the supply stays at the set voltage. As the load increases beyond that, the current limiter kicks in and lowers the voltage.

Okay, but what do the two SMALLER pins do on the 4 conductor Anderson connector?

You are not incorrect. However I think you have a bit of a logical issue there. If the battery is fully charged at 100v, and its at 100v, then of COURSE there is no current flowing. the battery is fully charged!

True, I worded it a bit silly. But even if it's half charged, the charging voltage will have to be so much above the battery resting  voltage  to charge it to get any charging current.

From the measurements I took today, 117 VDC is the charging voltage on a nearly fully charged battery. The battery resting voltage is a bit less, 116.7 VDC checked about an hour after being fully  charged.

So the fully charged battery voltage is 116.7 VDC on my 2017 Zero DS ZF 6.5.

-Don-  Cold Springs Valley, NV

[Keith]

Here are the specs for the Quiq charger. The 96V model can put out 135VDC but obviously it never does with the Zero program.

[Keith]

Okay, but what do the two SMALLER pins do on the 4 conductor Anderson connector?

This is the enable line. The charger puts about 3.5 volts on it, the bike pulls it down to about 1 volt to start charging. This signal will control the pack contactor off the bike as I show here http://electricmotorcycleforum.com/boards/index.php?topic=7116.msg59032#msg59032

[DonTom]

Here are the specs for the Quiq charger. The 96V model can put out 135VDC but obviously it never does with the Zero program.

Thanks, but I wonder why the math doesn't add up:

Max voltage is 135. Max current is 8.5 amps.  1,147.5 watts.

But they say the max power is 945 watts.

Even on our Zeros, if they draw that 8.5 amps:

117 VDC x 8.5 amps max spec=994.5 watts.   Yet spec is only 945 watts.

I wonder if they mean just don't exceed the 945 watts regardless of voltage and current draw.

-Don-  Auburn, CA

[Keith]

The charger is programmed by Zero to deliver a set current, usually 8.5 amps, at whatever voltage it needs to get that current. Then when it reaches full charge it limits the voltage to about 117 as you have seen. The charger LED shows green then. When the bike decides it is done (after balancing?) the contactor opens and you get red flashing indicating no load. The current might reduce at the higher voltages to stay within the rated power wattage, but I have not seen that indicated by the yellow LEDs. But that could be why it takes longer to finish charging above 90% or so. I don't have a current shunt to measure what it does at the end of the cycle, maybe someone who does knows for sure.

[Skidz]

DonTom, read up on LiPo charging techniques. A lot will become clear...

[DynoMutt]

As to server PS, if they are cheap enough and can be tuned up to 114VDC-116VDC, then don't transport them on the bike, leave any that are needed the places, such as home or work, where the charging is to be done.

[DonTom]

As to server PS, if they are cheap enough and can be tuned up to 114VDC-116VDC, then don't transport them on the bike, leave any that are needed the places, such as home or work, where the charging is to be done.

I am crious why you say don't transport them on the bike.

I sometimes take a Zero Quick charger (weight of these are about the same as the side case capacity, ten lbs) with a server "Y" cable so I can charge twice the speed at a ChargePoint or wherever. The SR with PWR tank needs all the help it can get to recharge. Even with two chargers, the wait is quite long with  the SR w/pwr tank.

-Don-  Auburn, CA

[togo]

They are made for a server room, not to be bolted onto a bike frame or rack, but I imagine in a shock-absorbing pelican case, they might last you a bit.  But they aren't potted or waterproofed, they are not intended for vehicular use.

[DonTom]

They are made for a server room, not to be bolted onto a bike frame or rack, but I imagine in a shock-absorbing pelican case, they might last you a bit.  But they aren't potted or waterproofed, they are not intended for vehicular use.

OIC.  I was thinking about the way I carry mine. In a saddlebag that is rather water-proof.

Charging on the road isn't much of an issue with me, as I own 8 motorcycles, six are ICEs.  I normally only use the Zeros for short distances, but sometimes it's nice to be able to extend the range a bit while having a meal or whatever. I find these E-cycles so fun to ride as long as I am not trying for a long distance. 

-Don-  Auburn, CA