ReInVolt PHEV Plan

Correct. I'll edit the text.

Also correct.

The problem is as an author, "I knew what I meant to say" but often leave out things that those not active in the area would understand. Usually, I have to read my text in reverse sentence order and even then, sleep on it.

My thanks for these helpful points which I am adopting.

Bob Wilson

 

REINVOLT ESTIMATED TRACTION BATTERY CAPACITY

In an ideal world, we would use the same traction battery capacity measurement systems used by the Department of Energy, a whole pack cycle. If we disassembled the pack, we could use the MRC989 to measure each module. But in the field our data sources are limited and we have to do with what is available.

The usual approach is to fully charge the battery and measure the Ahr for discharge. But the Prius battery controller tries to prevent a full charge due to the risk of overcharging the best modules or on discharge, a fatal, reverse charge. The nominal full charge is 80% of maximum and 40% of minimum. But within this range, we can measure the voltage change at a given current and project the battery capacity. It isn't perfect but sometimes it is good enough.

EXPERIMENTAL DATA

From a standing start at the bottom of a 525 ft. (160 m), 8% grade hill, the fully warmed up car with earlier descent charge, the brake was held and the accelerator floored. Within a couple of seconds, the ICE was running at steady speed and the brake was released. The car accelerated up the hill cresting at 78 mph indicated (84 mph true due GPS corrected from oversized tires: )

The amount of power that can be drawn from the battery is a function of speed. But to reach a given speed, the battery charge will be drawn down. So to start with a maximum charge, we use a standing start and then look for a region of somewhat linear voltage drain. Here is the raw data:

	Column 1	Column 2	Column 3
0	time	Volt	IB(A)
1	4:06:19	322.62	1.35
2	4:06:27	313.56	12.24
3	4:06:36	306.35	31.13
4	4:06:44	283.20	64.96
5	4:06:53	278.24	63.40
6	4:07:01	274.17	62.28
7	4:07:10	268.91	65.94
8	4:07:18	261.44	77.70
9	4:07:26	256.37	78.97
10	4:07:35	252.41	80.35
11	4:07:43	248.37	85.10
12	4:07:52	245.51	83.61
13	4:08:00	278.61	-21.98

These are data points and not terribly useful. So I prepared this table that interpolates the data between each point by averaging each pair of observation to generate:

	Column 1	Column 2	Column 3	Column 4	Column 5	Column 6	Column 7
0	time	dt (hr)	V(avg)	IB(avg)	Ahr	W
1	4:06:23	0.00235278	318.09	6.80	0.015987125	2	161.42
2	4:06:31	0.00234722	309.96	21.69	0.050899514	6	721.37
3	4:06:40	0.00236944	294.78	48.05	0.113839958	14	162.46
4
5	4:06:48	0.00235833	280.72	64.18	0.151357833	18	016.61
6	4:06:57	0.00236111	276.21	62.84	0.148372222	17	356.72
7	4:07:05	0.00235278	271.54	64.11	0.150836583	17	408.43
8	4:07:14	0.00236111	265.18	71.82	0.169575000	19	044.87
9	4:07:22	0.00234722	258.91	78.34	0.183869653	20	281.32
10	4:07:31	0.00235556	254.39	79.66	0.187643556	20	264.71
11	4:07:39	0.00236111	250.39	82.73	0.195322917	20	713.51
12	4:07:48	0.00236111	246.94	84.36	0.199171528	20	830.62
13
14	4:07:56	0.00235000	262.06	30.82	0.072415250	8	075.38

So using this data, I've calculated a conservative battery capacity:

	Column 1	Column 2
0	dVolt	-33.78
1	dt (min)	0.990
2	amp (avg)	73.50
3	dV/dt	-34.12
4
5	Max V	294 (*)
6	Min V (1V/cell)	114.00
7	dV	-180.00
8
9	minutes	5.274866785
10	Amin	387.7191927
11	Ahr	6.46

* Although higher voltages were measured, I used the highest with higher currents. If I use higher voltages, the Ahr capacity goes up, significantly.

The 6.46 Ahr is the lower limit of the traction battery capacity. These measurements were at nearly maximum current and power draw, 20 kW, nearly 10C. In most datasheets, 0.1C discharge rates are used which suppresses the I**R effects of internal battery resistance.

Now if we treat the 294 V as the 80% limit, then the Ahr capacity would be 6.46/.8 = 8.08 Ahr. This is possible because my re-hydration experiments have seen at least three NHW11 modules approaching this range with 7.2 Ahr:

I have deliberately underestimated the traction battery capacity that could easily be in the 7-8 Ahr range.

I can find no evidence that a ReInVolt pack built from salvage NHW20/ZVW30 modules suffers from the aging and loss of capacity seen in the NHW11 modules. This is based upon using the most conservative practices: 10C discharge rate; lower than maximum starting voltage and; ignoring the 80% upper charge upper limit.

Bob Wilson

 

SUMMARY

• ReInVolt Capacity - there is no evidence that NHW20 modules suffer similar degredation that is seen in the NHW11 modules. Independent measurements by the Dept. of Energy, 'oldnoah' and myself have documented the loss of original NHW11 module capacity. In contrast, the ReInVolt pack has double the Ahr capacity of my fully functional, 133,000 mile, NHW11 pack. Suggestion: we, the NHW11 community, need a better method of measuring traction battery health.
• ReInVolt Battery Electrical Quality - the module-pair balance at ~0.08 volts is less than half of my existing pack balance, ~0.20 volts even after sitting unused four weeks.
• ReInVolt thermal characteristics - there is no evidence of any problem cooling the ReInVolt modules. The improved, lower internal resistance of the NHW20 modules significantly reduces the rate of heating compared to NHW11s under descending hill, forced charging.
• ReInVolt case - the first case had a bolt hole misalignment and the installer of my pack reported some evidence of 'bent as if once dropped.' I didn't see it but then I didn't install it either. Regardless, case fit remains a challenge when dealing with used parts and shipping on a pallet. There was never any question about whether or not it would fit.

Thank you David Taylor and your team. I am quite pleased with my new ReInVolt pack. The quality of these rebuilt packs is excellent.

Questions? Comments?

Bob Wilson

 

I've been thinking about this and what you are asking for is environmental testing of the NHW11 and NHW20/ZVW30 modules to establish:

• aHr = F(temp, C)
• max temp = F(temp, C) :: tested to destruction

I'm thinking about this and though I have the equipment and skills to do first order testing, it isn't clear what benefit we derive other than to put quantitative numbers to the limits.

There are ~54,000 NHW11 Prius in the USA minus an average loss of ~3% per year. We know from existing reports that 'heat is the enemy' and that comes from climate, speeds over 65 mph, and hilly terrain. But the existing, say 50,000 NHW11 Prius owners were never aware of these limits and simply drove the car as any other car. But assume we have the engineering data, what then?

Many of these owners, especially those after the first owner, have no clue as to vehicle's service life. I would certainly publish the limits but they really need to be translated into useful data or guidelines that a non-technical owner/driver can use. Let me give some examples:

1. Avoid climbing hills faster than 55 mph
2. Draw no more than 6.5 amps from the battery for more than several minutes
3. Climb a hill limiting the engine rpm to 4,000 rpm or less
4. Climb a hill so the engine provides the hill climb power

All of these rules achieve the same goal, minimizing traction battery heating. But which ones are most useful or usable?

It gets even worse if we start spouting battery temperatures given how few even have instrumentation to monitor the traction battery temperatures.

I abhor ignorance and am disgusted by those who seek to limit our knowledge by stopping information sharing. But if I spend the time to measure the true limits of NHW11 modules and even the NHW20 modules, is that a good use of my time?

So let me turn the tables, if I provide you with sample sets of NHW11 modules, are you interested in measuring the environmental limits?

I may pickup the environmental limits if I decide to restart my module refurbishment experiments. If I do, I will need some basic engineering data having to do with pressures and gas behavior inside of the modules. But that area though interesting has a lower priority compared to my 'Franken Prius'.

Bob Wilson

 

In my line of work, this is high praise . . . 'doing too much.' <GRINS> There certainly are enough people who do not do enough. Thanks!

If I decide to get active again in NHW11 module refurbishment, I will have to do more life-cycle testing and analysis. But I have no plans to do this on the NHW20 modules since there is no evidence they have similar problems. Based upon the 38 NHW20 modules stress tested in my ReInVolt pack, they are awesome.

Indeed, I'm quite impressed.

This doesn't mean I now go about abusing the ReInVolt pack with 'pedal to the metal' hill climbs and repeated descents. I couldn't stand the mileage impact! Rather, I abused the ReInVolt pack to have confidence that it is tough enough to stand up to usage that would severely stress the old style, NHW11 modules.

Curious, I would like to know the thermal limits of the NHW20 modules and the extent that the NHW11 battery controller protects the pack from heat stress. We can look up the relevant P-codes from the Maintenance manual and I believe good Prius friend Patrick Wong has some experience with an overheated, NHW11 traction battery. But from what I have seen, a ReInVolt pack won't be nearly as easy to destroy as the readily available, NHW11-based packs.

Bob Wilson

 

Agreed!

I usually suggest folks ask for a print out of the module voltages to at least get a clue to the pack balance. It is far from perfect and to a great extent limited by what the car can read out. Still, it is better than just lookin' for error codes.

What seems to work best (or less bad) is to help folks with a ScanGauge. Not perfect, still it is the best of thin set of choices.

Bob Wilson

 

Understand, I have measurements:

Galileo: The Telescope & The Laws of Dynamics

Until anyone has better measurements, I really don't care. It is the difference between thinking from the ignorance of the 'dark ages' versus empiricism, the age of enlightenment.

If you have better data, trot it out. That is what "Skin in the Game" means!

Nothing in the universe can separate someone who volunteers to believe nonsense versus those who in contrast choose the meter movement of an instrument. I prefer the instrument and leave those who wish to believe 'wishes' to the hell of their own making.

Do I need to make it more clear?

Obviously, we've laid our cards down and . . .

When I read this:

I considered it high praise . . . and still do. But I didn't realize it was the same dogma, the same call for ignorance and censorship that condemns those who make measurements. I didn't realize that this was a complaint about someone reporting what they observed. I had greater expectations but am not surprised.

Bob Wilson

 

Well let's see what 'pointless' means:

• NHW11 pack - the weakest module pair in the NHW11 pack measured ~3.5 Ahr. This is consistent with the values 'oldnoah' measured with his pack modules. I will be keeping these modules for the next phase.
• ReInVolt pack - measured a conservative, capacity of no less than 6.5 Ahr. The likely value is on the high side of 7-8 Ahr.
• Similar cooling - the NHW11 module pack showed a steady 1C/10 minute cooling rate at 10V fan voltage which appears to be a similar cooing rate as the ReInVolt pack
• NHW20 modules - significantly better constructed than the NHW11 modules with improved terminal seals
• Toyota reports - NHW20s have lower internal resistance which reduces I**R heating

If you have better facts and data, trot them out.

Bob Wilson

 

No difference in ordinary driving. I got the car back at noon last Saturday and did my initial set of tests. Then workdays Monday and Tuesday were in the upper 70s, mild, and I was seeing normal mileage in the middle 50s. Wednesday a cold front arrived and drove the temperatures down to the 40s and 50s. Friday was a workday and normal cold weather performance using my neighborhood warm-up profile.

Acceleration was as before, somewhat muted by the larger diameter tires and the weight of two battery packs. Randomly monitoring the Blo and Bhi with the ScanGauge, the car has behaved normally with the difference running ~0.1 V whereas the original pack was ~0.2 V. But the original pack had been at this ~0.2V difference for as long as I've been able to monitor.

The only detectable difference was in maximum acceleration going up Brindley Mountain from a standing start. The car reached 78 mph at the top without running out of battery or showing turtles. Previous maximum hill climb speeds had seen traction battery exhaustion at the crest. This is a significant improvement although not likely to be repeated. I had long ago learned that hill climbs should be at 55 mph, completely engine powered, and that remains my practice. <grins>

Not widely known, there is a period of about 40-45 seconds when the car first starts when cold that with modest acceleration, it runs mostly on EV power. This is the time it takes for the catalytic converters to reach operating temperature. This 40-45 second window is just enough to reach 35-40 mph while the ICE fuel consumption holds steady at 0.60 GPH. A warmed up ICE would burn 1.5-2.0 GPH to reach the same speed. Both traction batteries easily handled this modest power demand.

At work I park near the exit where I can watch for on coming traffic before starting the car. When I see a break coming and no one in the way, I start the car and smoothly pull out and accelerate to 35-40 mph before the cats light off. This often gives an initial MPG of 40-42 MPG and a slight drain in the traction battery SOC indication. I see no difference between the NHW11 and ReInVolt pack state of charge indication.

Once the cats light off, the lowest fuel consumption during warm-up is ~0.30 GPH in "N". If in "D" and stopped it will often burn ~0.60 GPH to recharge the depleted battery. Warm-up is an area where the NHW11 pack may make a difference.

Bob Wilson