Battery SOH - bragging rights or bullshit?

[chl]

No one said that, ever !
...
But people are not saving money by charging slower, so it would be incorrect to tell them so.

Huh? Yes they are!

If they charge with a lower current they are wasting less kWh to wire resistance, and that is what the utility charges for.

Lower current, less energy wasted to wire resistance.

It may be a small number of kWh per charge, but it adds up.

I have a 75ft run, so 150feet total of 6AWG with about 0.04 ohms per 100 feet, so 0.06 ohms total.

I did the numbers for my wiring at 80A vs 32A as an example.

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To add about 10kWh to the battery:

At 80A it takes about .52h (31 minutes) if there were no losses due to the wire resistance.
80A x 80A x 0.06 ohms x 1 hour = 384 Wh energy lost in 1 hour
But in 0.52 hours x 384W = 199.7Wh is lost due to wire resistance
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If I use a 32A charge current it would take about 1.3h if there were not wire resistance losses.
32A x 32A x 0.06 ohms x 1 hour = 61.44 Wh energy lost in 1 hour
In 1.3 hours x 61.44W = 80Wh lost due to wire resistance
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The 32A charge wastes less energy than the 80A charge for adding about the same kWh to the truck battery.

Numbers don't lie.

And the difference in energy per hour wasted is about a factor of six: 384/61.44.

So even though it takes longer to add energy to the battery, it is more energy efficient to use a lower current.

The utility charges for the energy you are using whether you add it to the truck or waste it.
The less you waste, the less you pay.

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Or put another way, it actually uses more energy at 80A than at 32A to add a kWh to the battery, and you pay for it.

Like I said, it may be a small amount of cost per charge, but over time it adds up.

Maybe time is more important to the owner than cost, then fine, use a higher current.
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Due to wire resistance in my example:

In one hour at 80A x 24V (19.2kW), 18.82kWh is added to the battery.
For every hour at 32A x 240V (7.68kW), 7.62kWh is added to the battery.

Wasted energy costs money.

Hope that makes more sense seeing the numbers?

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[chl]

FWIW, I don't charge to 100% unless I'm going on a trip outside my usual sphere. Example, a.friend that lives about 80 to 90 miles away, family that is 100 plus miles, etc. I want to be sure to use the extra charge above the 80% I typically charge to. Really, I have probably fully followed their criteria only a few times.

However I was responding to the person that appears to be having balancing issues. Their responses.suggested to me that they had never changed to 100% for balancing. So for that person, it seems prudent to give it a go to see if it improves their situation, or flushes out another problem.

Yes, I agree, it would be worth a try.

If there is a bad cell or two, it won't help/fix that issue.
But if there was a lot of BMS 'drift' causing the delta, then it might.

In the Leaf forum over the years it has been an issue and results were mixed.
With the Leaf, to see a balance improvement, the process of up and down between 100% and 10% had to be done three times with long pauses (5 hours or better overnight) in between!

But what people found out was a large delta was generally not fixable this way and indicated a bad cell or two. With the Leaf, there were people who would replace down to the cell pair level, quite a task!