Can HX (battery internal resistance) be improved?

[nlspace]

Hx as a percentage has never made any sense to me.

Is it conductance? Is it internal resistance? If so why not call it by what it is?

That is why i traced the schematic to try to figure out what in the hell it was doing and trying to measure. Still don't know but i'm searching patents too.

 

[lorenfb]

Hx as a percentage has never made any sense to me.

Is it conductance? Is it internal resistance? If so why not call it by what it is?

That is why i traced the schematic to try to figure out what in the hell it was doing and trying to measure. Still don't know but i'm searching patents too.

It's just a percentage of the original, when the battery was new, conductance is just like SOH which starts at 100%.

 

[MikeinPA]

nlspace, is it possible the LBC is estimating SOC, SOH, etc for each cell pair? The current is the same for every cell pair, and the LBC is collecting voltage at the cell level.

 

[nlspace]

i found some old patents for inventions by a fellow, Keith S. Champlin, who made devices to measure mostly qualitative battery health without using high current loads. Uses op amps with both AC and DC elements to determine a signal proportional to Conductance. With calibration and scaling this can create a linear relation to the original capacity in A-Hrs, or to the rated cold cranking amps, CCA.

So i'm gonna assume the LBC is calculating the Hx as a percentage of the original Ahr capacity of the Pack since there is no specification on CCA for an EV. Maybe this is another method to express the state of health when measured from another approach than using coulomb-counting.

As a result of my research and investigation i conclude that the answer to the OP is NO, you can't do anything to improve or change the Hx in any meaningful or useful manner. Hx really means very little and has no useful purposes with respect to driving or charging your EV other than as a relative comparison to the SOH value.

 

[MikeinPA]

A partial analogy for CCA rating in lithium cells would be the rated continuous current (related to internal resistance); this declines with age, and the LBC would provide this value as a performance metric like horsepower is for ICE vehicle. Another possibility is charge acceptance--the LBC could be reporting on the maximum acceptable charge rate as a percentage of some original value (also related to internal resistance); this metric would also be useful to the operator because it shows how fast the vehicle can refuel. Hx could even be both of these, percentage of maximum original power available and percentage of maximum available charge rate available.

 

[Lothsahn]

Thanks I appreciate the responses. My 24kWH battery has 10 bars so marginally better than the degraded 30kWh.

When I test drove the car I didnt pay attention to the regen bubbles, didnt look at leaf spy while driving, I should have. Also should have read the DTC error codes, seem to have forgot how to check out a used car.

The car lived in Oakland CA at least for first 18K miles which is where the Nissan national records stopped. Car did have the PC630 recall for the battery reprogram done at 18K miles.

Then it qualifies for a battery capacity warranty. Get yourself a new battery! Make sure you take it in to the dealer before the warranty ends. DON'T WAIT. Keep in mind you may be waiting a year or two. It's a mess out there.

That said, I don't know if a 24kWh can be put into a 2017--people are usually trying to go the other way. It can definitely be done, but it may require purchase of a Can Bridge (muxsan or Dala). Electrically a 2015 and 2017 should use the same plugs, so you won't need adapters there. The question is just "can you clear the P3102 code in the computer using LeafSpy". Dala might have a chart on it--could Google it, or try swapping the batteries!

 

[Ronin78PL]

Mamy akumulator 40 kWh z 2018 r., z zaledwie 60% HX, ale różnicą ogniw wynoszącą zaledwie 3-4 mV i przebiegiem na liczniku wynoszącym 40 000 mil, a wciąż pozostało 35,2 kWh. W każdych warunkach sprawdza się więcej niż świetnie.

I'm trying to find a way to even out the cell differences. My 2023 Leaf 10,000 miles has 21 mV SOH 95.44% and HX 84.06%.
Could you briefly describe how to use and charge the car? Maybe I charge it to 100% too rarely? This happened to me several times, maybe 5-6 times in these 10 months.

 

[Chad E. Mo]

Point of reference:

I charge my 62kWh pack to 100% after two 50mi trips, every other day (not driven on alternate days). Charge to 100% at work, charge to 100% at home.

I see each charge session taper from 6.6 kW to zero, pause 5 min then a low power charge for 5min... the pause and low power charge repeated two more times.

My assumption is the three pauses are the balancing resistors drawing down the high cells, and the low power charges bringing the entire pack back up. (I haven't had LeafSpy log the cell voltages overnight to validate the assumption.)

My recent status is ~9mV diff, 91%SOH, 94Hx%.
38k miles on a 2020, ~50 QCs, ~180 L1/L2.

The graph is from my EVSE outlet monitor.



I don't usually leave the car at 100% more than 24 hrs.

 

[hornstudio]

I'm trying to find a way to even out the cell differences. My 2023 Leaf 10,000 miles has 21 mV SOH 95.44% and HX 84.06%.
Could you briefly describe how to use and charge the car? Maybe I charge it to 100% too rarely? This happened to me several times, maybe 5-6 times in these 10 months.

I never charge when SOC is above 80%, no topping. I only charge when necessary. Most times I charge when 1 of 12 bars are left. I always charge 100% and with 1 phase 3,6kW.

 

[mux]

Some years ago i traced out the LBC schematic for the "conductance" measurement, aka internal resistance, and posted here:
https://www.diyelectriccar.com/thre...ry-controller-lbc-details.204369/post-1067783

The function is active when relay RLY1 is energized from IC1 to connect the Pack HV+ to HV- across a resistor divider circuit which has a divider-output measurement range of about 3.2 to 4.2 VDC for a Pack voltage of 300 to 400VDC.

The microcontroller IC1 has a timer which outputs to drive an RC network with time constant ~0.45s and create a saw-tooth sinusoidal which is summed with a low voltage DC and referenced with respect to the Pack low side HV- connection.

IC7 and IC8 had their part numbers etched off, so somebody wanted to hide what they are using.

The little white relay can be seen in the upper right quadrant along with the widely-spaced resistors in this photo:

This is not actually how Hx is measured, this is the isolation resistance measurement circuit! You can almost perfectly trace it out according to the TIDA application note:

https://www.ti.com/lit/pdf/tidudj6

It uses those same isolated opamps. Same circuit is used in the Isabellenhütte IVT sensors.

Hx and other pack characterization measurements are derived from pack voltage and current data, it's not a discrete measurement. And that's because there is not 'one' internal resistance measure - internal resistance is a compound phenomenon comprised of actual Joule resistance (resistance as you and I know it), chemical diffusivity and ion mobility.

 

[nlspace]

Good find, thanks for sharing.