Leaf 12 volt charging system thread

[cornbinder89]

I'm starting a thread on the Leaf's 12 volt charging system peculiarities.

I noticed that some have reported different voltage readings between battery post and Leafspy.
I ran mine though a bunch of different scenarios while watching Leafspy and a digital volt meter on the battery post.
I noticed at least a tenth of a volt but sometimes exceeding two tenths discrepancy. Leafspy always reported a lower voltage than the meter.
The parking pawl motor is a fairly high draw, shifting in and out of park drops the voltage mush more than all the lights can

With all the "gauges" on Leafspy, it is unfortunate that 12 volt current is not one of them.
Despite what is written in the manual, I could never get the charging voltage much over 14.5 volts. To properly use the IUoU charge protocol, it need to be much higher to fully recharge.
The Key On "engine off" loads seam to be substantial. I'm going to have make up a shunt that I can cut an ammeter in and out to see what they are and what the "dark" loads are.
At present it doesn't seam that even a fairly substantial charge current though the amp shunt bumps up the charging voltage.
Given that finding, it doesn't hold much promise that manipulating the current shunt would improve the charge protocol.
The whole time I was watching and manipulating and watching I never once saw the charging system go to float voltage or even drop the charging voltage from ~14.4.
So far, what I have seen, the Leaf doesn't hold to either common protocol well enough for it to recharge, but oddly doesn't seam to hold what the manual say it should do either.


It is unlikely that the difference between Leafspy and my meter is a simple calibration error as the difference in reading is not in "lock step" and grows and shrinks depending on conditions.
With the current, voltage and temp sensors, it should be a no brainer to make a IUoU system that works, quickly brings the battery back to full charge and then "floats" the rest of the time the car is charging.

 

[Learjet]

Leaf spy difference could simply be voltage drop over the wiring to the point where the voltage is measured.

 

[cornbinder89]

Leaf spy difference could simply be voltage drop over the wiring to the point where the voltage is measured.

I don't think so, as you would expect when the DC-DC converter kicked on, if the wiring were to blame the voltage would be higher at the source (DC-DC) than at the load (the battery)
If it shifted to above battery level when charging took place, I'd agree with your assessment but the difference actually got bigger, where the meter on the battery was recording higher than Leafspy.

 

[Learjet]

I don't think so, as you would expect when the DC-DC converter kicked on, if the wiring were to blame the voltage would be higher at the source (DC-DC) than at the load (the battery)
If it shifted to above battery level when charging took place, I'd agree with your assessment but the difference actually got bigger, where the meter on the battery was recording higher than Leafspy.

Are you sure the power is being measured at the converter...or is it coming from the Bluetooth module and the OBDII port power...or some other source that is downstream from the converter?

 

[cornbinder89]

Are you sure the power is being measured at the converter...or is it coming from the Bluetooth module and the OBDII port power...or some other source that is downstream from the converter?

No idea, but all of those are placed between the battery and the supply, so would tend to bring the difference closer together when powered up.
Battery is at the end of the string, The DC-DC converter is what is causing the voltage to rise, the fact that I see higher differential when charging than when the DC-DC is inactive makes it difficult to see any wiring as being the cause.

 

[BillAinCT]

At present it doesn't seam that even a fairly substantial charge current though the amp shunt bumps up the charging voltage.
Given that finding, it doesn't hold much promise that manipulating the current shunt would improve the charge protocol.

You do see as was reported that the voltage jumps up with the current sensor disconnected? I ask because I've been contemplating an inline module that would periodically disconnect the current sensor (the interval and the time it's disconnected TBD) to keep the battery more charged and avoid the silly flick the wipers work around.

 

[cornbinder89]

So far, my readings showed it jumping to approx 14.4 with the sensor plugged in. I never saw it go to float, but that is what I would expect because the battery wasn’t near full charge.
I’ll have to charge it up and see if it goes to float voltage and what that is.

 

[nlspace]

Doesn't LS report the current next to the 12V battery voltage, lower left corner?

The cable from the PDM to the battery is heavy gauge and can't be over 5 ft long. It's probably larger than 10 AWG, but 5" of 10 ga. would be about 5mR and drop 50mV per 10 Amps. Larger gage wire would have less drop, hard to imagine that the cable is throttling the DCDC.

 

[cornbinder89]

No, L/S only report battery voltage down there.

The voltage I am reading at the battery is higher than what L/s is reporting, I am in no way suggesting that cabling is "throttling" the charge current. That was the point I was making, other were suggesting it was wiring resistance that was causing the discrepancy, but I just don't see how?

 

[Tony 240]

I have installed a 12 volt cord on my Leaf that goes inside to a separate 12 volt system that is charged by my solar system which keeps the battery at a much higher voltage than the DC/ dc convertor does on the leaf. The leaf will only charge the battery up higher when a heavy load is put on the 12 volt system (example fans and wiper blades). Where as a ICE car will always bring the voltage up as soon as the engine is started. Most lead acid batteries last longer if they are brought up to full charge on a regular basis. I used to maintain electric fork trucks and we switched our battery chargers out to ones that would pulse the Dc into the battery, this would make the plates in the battery cells "shake" the build up that is on the plates. We had batteries that were almost 30 years old

 

[Learjet]

No, L/S only report battery voltage down there.

The voltage I am reading at the battery is higher than what L/s is reporting, I am in no way suggesting that cabling is "throttling" the charge current. That was the point I was making, other were suggesting it was wiring resistance that was causing the discrepancy, but I just don't see how?

I understood your post....I was suggesting the voltage drop is from the wires to the point that LeafSpy takes the voltage reading. In fact, the large cable to the battery is preventing the voltage drop and why you are seeing higher voltage when measured at battery. If we don't know where Leafspy is measuring the voltage...then it's all a guess.

Also, once the 12v battery charge current goes below ~2 amps the voltage will lower to the battery.

 

[cornbinder89]

Voltage drop in wiring is a function of the current draw on the line. Voltage reading is a high impedance measurement.
While it is possible that there is something else on line, that is loading the wire, but not sure what that would be?

 

[woeful]

LeafSpy connects using an ELM327 device, which includes a voltage sensor. It may well be reporting that reading, which isn't very precise unless recently calibrated against a reliably and independently measured voltage. If you want a second measurement of the 12V system voltages, best to use an accurate multimeter.

 

[nlspace]

Try landscape mode,

 

[cornbinder89]

Try landscape mode,

Yah know, I thought I remember seeing that on others post, but couldn't find it on my read-out. Thanks.

 

[cornbinder89]

Found it, and it doesn't require landscape, but will not read when the DC-DC is not operating. I'm still learning both L/S and smart phones.
It sure would be nice to be able to change the charge regime. Mine is currently charging at over 10 amps when the car is on, it shouldn't be that discharged.
Got a tender on it now, but really want to find out why there is such variation with people experience.
I'm going to have to make a shut with a switch to be able to get an accurate "dark current" measurement.
I am not doubting that people have real problems, but would like to find a solution that keeps the basic IUoU charge profile.
Had a heck of a time figuring out how to unlock the screen so it would go to landscape!

 

[cornbinder89]

This came up on another site I am on. I think it might be very useful in sorting out the Leaf's 12 volt problem, or at least totally rule out excessive dark current draw.