GregH
Posts: 860
Joined: Fri Jul 01, 2011 4:16 pm
Delivery Date: 13 Jun 2011
Leaf Number: 26967
Location: Irvine, CA

SOC vs RAhC

Thu Jul 07, 2011 9:58 am

I think Sparky nailed it on the 0x5bc "SOC" number...
From what I've observed the last few days on my car and gleaned from the service manuals, this number is the Remaining Capacity (in Ahs)
It seems to be scaled to 1/4 Ah and has a very heavy hysteresis (tons of regen needed to bump the number up!)
During charge I observed the number increasing at about 90 second intervals when the pack is low and 100 second intervals when closer to full (approximately).
This would be true as the pack voltage increases under a constant power charge... the current would lower and the Ahs would accumulate slightly slower.
I know many of you with slightly more mature packs are getting 281, but mine is still 278.. actually 277 today (!)
The service manuals talk about a Remaining Capacity CAN message from the battery system, but no mention of "SOC" (which we typically think of as a number from 0 to 100%)
The service manuals talk of a nominal pack voltage of 345 volts (3.6V/cell) and a max 393V (4.1V/cell) and absolute max 403V (4.2V/cell) which is all reasonable for a Lithium magnate chemistry.
24000kWh/345V = 69.5Ah... x4 = 278.
I'm guessing each cell in the 4-cell modules is rated at roughly 35Ah and 3.6V nominal.

Now of course Remaining Ah Capacity and State of Charge are pretty much the same thing other than the scale..
I think on my display I'm going to stick with the raw number which I'm calling Remaining Ah Capacity (RAhC) rather than scaling to 100% and calling it SOC...

Thoughts?
'17 blue Volt Premier w/ACC
'12 SL black Leaf
'11 SL blue Leaf
RAV4-EV 2002-2005
Gen1 & Gen2 EV1 1997-2003
PV 2.4Kw, 10kWh lithium battery SCE TOU-DA

Herm
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Delivery Date: 29 Aug 2012
Location: Timbuktu, Mali

Re: SOC vs RAhC

Thu Jul 07, 2011 12:03 pm

if you could find the actual pack voltage, then you could calculate a true wh capacity scale.. and that would give you the true SoC

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garygid
Gold Member
Posts: 12469
Joined: Wed Apr 21, 2010 8:10 am
Delivery Date: 29 Mar 2011
Leaf Number: 000855
Location: Laguna Hills, Orange Co, CA

Re: SOC vs RAhC

Thu Jul 07, 2011 3:32 pm

If it is measuring Ah from/to the battery, it has no good way of knowing where "zero" is without discharging the battery "completely".

Also, the top 8% of the Amp-hours should give us more energy (more miles actually driven) rather than less energy and less miles driven.

Many experience getting only 50 to 60% of the miles from the Top Bar, compared to the middle bars, even when starting near 278 (to 280) raw.

But, anything is possible.

No matter how this is derived (probably in the BMS), it performs the function of a fuel gauge, with an uncertain (variable) low end.

It appears that another mechanism, like lowest (or highest) cell voltage, is actually telling the car to STOP driving (or charging).

We think we have found battery voltage and current elsewhere.
See SOC/GID-Meter and CAN-Do Info
2010 Prius
2011 LEAF, 2014 Tesla S85
2018 & 2019 Tesla Model 3
PU: SDG&E
Solar PV: 33 x 225W -> 7 kW max AC
Craigslist: Xm5000Li Electric Motorcycle

GregH
Posts: 860
Joined: Fri Jul 01, 2011 4:16 pm
Delivery Date: 13 Jun 2011
Leaf Number: 26967
Location: Irvine, CA

Re: SOC vs RAhC

Thu Jul 07, 2011 3:33 pm

I'd love to find pack voltage! And pack current... Cell voltages and indication of balancing would be nice as well, but I'd bet we'd need to "borrow" a Nissan scan-tool and snoop on the bus during a transaction in order to see how to get that.. It is probably something that needs to be asked for via a CAN message and we need to figure out how to do that. But pack voltage and current? C'mon... it's gotta be in there!
'17 blue Volt Premier w/ACC
'12 SL black Leaf
'11 SL blue Leaf
RAV4-EV 2002-2005
Gen1 & Gen2 EV1 1997-2003
PV 2.4Kw, 10kWh lithium battery SCE TOU-DA

GregH
Posts: 860
Joined: Fri Jul 01, 2011 4:16 pm
Delivery Date: 13 Jun 2011
Leaf Number: 26967
Location: Irvine, CA

Re: SOC vs RAhC

Thu Jul 07, 2011 3:35 pm

garygid wrote:We think we have found battery voltage and current elsewhere.
Where? Is it a secret?
'17 blue Volt Premier w/ACC
'12 SL black Leaf
'11 SL blue Leaf
RAV4-EV 2002-2005
Gen1 & Gen2 EV1 1997-2003
PV 2.4Kw, 10kWh lithium battery SCE TOU-DA

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garygid
Gold Member
Posts: 12469
Joined: Wed Apr 21, 2010 8:10 am
Delivery Date: 29 Mar 2011
Leaf Number: 000855
Location: Laguna Hills, Orange Co, CA

Re: SOC vs RAhC

Thu Jul 07, 2011 5:10 pm

I forget the locations, but try CAN-Do and look at the "recipe" list on the Filters page.
See SOC/GID-Meter and CAN-Do Info
2010 Prius
2011 LEAF, 2014 Tesla S85
2018 & 2019 Tesla Model 3
PU: SDG&E
Solar PV: 33 x 225W -> 7 kW max AC
Craigslist: Xm5000Li Electric Motorcycle

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TonyWilliams
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Location: San Diego
Contact: Website

Re: SOC vs RAhC

Thu Jul 07, 2011 11:50 pm

GregH wrote:The service manuals talk of a nominal pack voltage of 345 volts (3.6V/cell) and a max 393V (4.1V/cell) and absolute max 403V (4.2V/cell) which is all reasonable for a Lithium magnate chemistry.
24000kWh/345V = 69.5Ah... x4 = 278.
I'm guessing each cell in the 4-cell modules is rated at roughly 35Ah and 3.6V nominal.

Excellent observations !!!

Thanks!

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surfingslovak
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Re: SOC vs RAhC

Tue Jul 12, 2011 8:56 pm

GregH wrote: Excellent observations !!!
Great observation, thanks for mentioning it. The max pack voltage would be consistent with the 393V charging voltage seen on the sole QC station in Portland by PDXLeafer.

http://www.mynissanleaf.com/viewtopic.p ... 3V#p109596

GregH
Posts: 860
Joined: Fri Jul 01, 2011 4:16 pm
Delivery Date: 13 Jun 2011
Leaf Number: 26967
Location: Irvine, CA

Re: SOC vs RAhC

Tue Jul 19, 2011 10:46 am

Hey guys! I've been meaning to update this post but been a way for a week or so.. GaryG's CAN-do software shows the locations of the pack voltage and pack current in 0.5V and 0.5A steps and I've since been able to confirm both numbers. A little more precision would have been nice, but I'm not complaining! I've since brought up both numbers as well as a power/regen graphic representation of current on the top of my display alongside the RAhC.. It all fits nicely and behaves just as expected. The highest I've seen on my pack during charge (as high as 280 RAhC, still haven't seen 281) is 394V which implies that even at full charge, the cells are averaging 4.1V. After an overnight "80%" charge, the RAhC was about 230, or about 82% and the pack voltage was resting around 389V or 4.05V per cell.

I've also seen evidence of pack balancing although not directly.. I'd be curious to hear if anyone else has seen this... After a full charge and the blue lights were off, I plugged in my display and of course got no data (car off, not charging but still plugged in). About an hour later I came down to the garage and there was data on the display! Ie the car had woken up.. Did it charge? Did it balance? I don't know.. Maybe one of the folks with time recording on their EVSE unit can say if it comes on periodically for small charges every 15-60min(?) while balancing the cells... This is what I'd expect as the balancing electronics can only slowly discharge the "full" cells compared to the 3.3+kW charge..
'17 blue Volt Premier w/ACC
'12 SL black Leaf
'11 SL blue Leaf
RAV4-EV 2002-2005
Gen1 & Gen2 EV1 1997-2003
PV 2.4Kw, 10kWh lithium battery SCE TOU-DA

User avatar
garygid
Gold Member
Posts: 12469
Joined: Wed Apr 21, 2010 8:10 am
Delivery Date: 29 Mar 2011
Leaf Number: 000855
Location: Laguna Hills, Orange Co, CA

Re: SOC vs RAhC

Tue Jul 19, 2011 10:51 pm

A period of about 45 minutes "doing nothing" followed by about
5 minutes of somewhat-reduced-amperage charging has been observed
to occur at least 2 times after the "main" charging portion is completed.

I assume the "doing nothing" was a time of discharging the highest cells.
So, for now, I call these "equalization" cycles.

Open Questions:
1. Do they occur after every 100% charge?
2. Do they occur after any 80% charge?
3. How many cycles can occur (we have seen 2)?
4. Is this really the cell-equalization mechanism?
5. If they never follow an 80% charge, must a car be charged
to 100% occasionally to maintain cell-equalization?
6. What situation stops or prevents the equalization?
See SOC/GID-Meter and CAN-Do Info
2010 Prius
2011 LEAF, 2014 Tesla S85
2018 & 2019 Tesla Model 3
PU: SDG&E
Solar PV: 33 x 225W -> 7 kW max AC
Craigslist: Xm5000Li Electric Motorcycle

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