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Discussion Starter #1
What is the battery state of charge indicator a measure of? I know it's the amount of charge left in the hybrid battery pack, but is it voltage, amps....what?
 

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Amps is a measure of current flow, so it's not that. (The charge/boost indicator is likely based on amps flowing into/out of the battery)

I believe it is volts (electrical pressure/potential) run through some "normalizing circuit" or similar to keep some control over the range displayed.

There are some of Mike's threads I think where he talks about measuring the pack and comparing it to the display.
 

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The problem with that theory, John, is that when you aren't using the battery, there is zero current to plug into your equation which will always result in a zero answer.

If the display were using your formula, it would go up and down wildly along with the charge/boost meter's movements. Therefore I find that it is not possible that it is using your formula.
 

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Ok I was trying to make it too simple. But its been discussed at length in the past.

The "formula" is correct. The BCM just keeps a running tally and that is what's displayed.

[edit / addendum] jtmco gives a nice analogy in his post below. And my example here may still be too vague (math "word" problems)

P=IE Power = current (I) times voltage (_E_lectromotive force)

Power over time = energy as used several times in this thread. ;)
[end]

HTH! :)
 

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Let me take a stab at this.

I think the units of the State of Charge Indicator are Energy.

The batteries are rated at 6.5 Amp-hours and 144 Volts or 864 Watt-hours of Energy. But you cannot measure this directly without draining the batteries. What you can measure is the Voltage of the pack and the current (Amps) that leaves (or enters) the pack. You can also measure the amount of time that the current is entering or leaving the pack. By multiplying the three together: Volts x Amps x Time, you can calculate how much energy has entered or left the pack (in Watt-hours or with some conversion in Joules).

By analogy, suppose you had a one gallon bucket of water but it is hidden behind a curtain so you cannot see it. You are, however, allowed to see how much water flows into or out of the bucket. To keep track of how much water was in the bucket, you would drain it all out, fill it with one gallon, and then monitor how much you put in and take out. That way, you know how much is in the bucket at any one time.

But the system is imperfect. You never know EXACTLY how much water (read current) went into or out of the system so every once in a while, you decide to "recalibrate". You drain the bucket and fill it up again. This is what the Insight is doing when it has a "recal"

I think John addressed it to some extent a long time ago in the following post:

IMA Battery recalibration - Assist while recharging?


HTH

Jim
 

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Imperfections in the system are created by variations in the temperature and charge dependant internal resistance of the cells (that produces unacounted for wasted energy in the form of heat), self discharge of the battery pack over time, and degradation of the batteries capacity with age.

The battery indicator is the electrical equivalent of the gasoline fuel gauge.
 

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Discussion Starter #8
jtmco said:
I think the units of the State of Charge Indicator are Energy.
Which are measured as units of what? If this gauge had numbers on it what would the units be known as?
 

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Geez Resist :!:

Pick one, any one you want for "energy".

Although some are obscure and others by definition will require a lot of leading zeros to express this relatively puny amount of energy. There all the same thing and can be mathmatically equated. And while BTU's could be used you'll have to do the math should you choose this unit of energy. Yes it would be "valid" but then people will look at you like your crazy for choosing it.

Hint:
This is where your supposed to google-up some further information for yourself. ;)

But since its an electrical device I'd stick to the commonly accepted electrical energy equivalent units Kw.
 

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I'd already typed up all this before John's latest post so at the risk of getting carried away (and because it is fun to think about).....


The units of Energy could be:

Joules
Calories
BTUs
Ergs
Watt-hours
Watt-seconds
kiloWatt-hours
or even equivalent volume of gasoline (say gallons)

Watts or kiloWatts is Power and Power is Work / time. Since Work is the same as Energy, then Power = Energy / time or Energy = Power x Time. That means Watts x Time gives you Energy so Watt-hours, Watt-seconds, or kilowatt-hours are all Energy units.

When you buy electricity from the "Power" company, you actually buy Energy. They charge you by the kiloWatt-hour (kWh). They multiply the rate at which you use the power (in kiloWatts) by how long you use it (in hours). So, for example, if you use a 100 Watt light bulb for 15 hours, that would be 1500 Watt-hours or 1.5 kWh (since 1000 Watts = 1 kiloWatt). In Virginia, that would cost you about $0.12 (1.5 kWh x $0.08 / kWh).

I think the Insight battery pack has 864 Watt-hours of Energy (6.5 Amp-hours x 144 Volts). Since 746 Watts = 1 hp, that means that the Insight batteries can provide 1.16 hp (864 / 746) for one hour. If you want 10 hp, you get about 6 minutes.

Just to think about the numbers on the gauge a bit more, it could be from:

0 to 0.864 kWh

or multiplying by 3600 seconds in an hour,

0 to 3110.4 kiloJoules (kJ) (since 1 kJ/s = 1 kW)

Since food is measured in Calories (big C - really kilocalories) and since 1 Calorie = 4180 Joules = 4.18 kJ, then if we divide by 4.18, the gauge could read:

0 to 744 Calories (about 2 candy bars)

Finally, if you wanted to pretend like it was a gasoline equivalent, Gasoline has about 43,000 kJ/kg of energy. Dividing into 3110.4, that means the gauge could read

0 to 0.0723 kg of gasoline.

The density of gasoline is around 800 kg per cubic meter, so the guage could read

0 to 0.00009 m^3 of gasoline

and since 1 US gallon = 0.00379 m^3, then the equivalent in gallons would be

0 to 0.0239 gallons of gasoline

or

0 to 3 ounces of gasoline

or

0 to 6 tablespoons of gasoline.

Are my numbers believable? I think they are. 0.02 gallons of gasoline is 1/50 of a gallon. If you get 50 mpg and you can drive 50 miles on a gallon of gas then 0.02 gallons would take you about 1 mile which I believe is about the capacity of the Insight battery pack.

My apologies if I have gone overboard, if I’ve overexplained things or if I’ve made a conversion mistake, but I think I have it about right.

Jim
 

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Good comprehensive post Jim :!: :)

But you gave away my planned "incomplete" term Kw (should be kWh) so now we'll never know if Resist did his homework. :p

But such a post "burns" too many calories for it to be "fun" for me to write anymore. ;) :p
 

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Well Jim, I got a good chuckle reading it. I also found the relationship between gasoline volume and battery capacity thought provoking. Thanks. :D
 

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You can't. It's a proprietary program with a GUI.

However, in the spirit of "gas gauge" let's call it a "charge guage".
 

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It is essentially the same thing that is on the side of your home to measure how much electricity you use. Those devices are generally called Watthour meters:

Watthour meters

In most homes, the value on the meter always increases, but if you had your own generating capacity (solar cells, windmill, diesel generator) you could sell power back to the electric company. If you produced enough, you could keep the meter at a steady value or even make it go down.

The big difference is that the batteries in the Insight have a limited capacity so there is a maximum value. I would probably call it a Watthour guage.

I have this funny picture in my head of getting of those big old Watthour meters and mounting it on the dash of the Insight (probably with duct tape!).

Jim
 

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I think Kip is right--you can't. I'm not sure if Resist is wanting to go into Radio Shack or somewhere and buy a meter with which to measure his battery capacity, or what, but regardless, there is no simple device that I know of that could work.

It's just like with a normal car battery. You can measure the voltage, or you can measure the current flow through a circuit at any given time, but neither will tell you the capacity of your battery, or the remaining energy in it.

the closest real world thing I can think of that deals with anything similar is the electronic car battery charger that I recently bought. It is very smart and does some things like vary the amount of charging it does based on readings it takes over time, but even that thing doesn't offer any opinions on percentage of charge, or amount of energy in the battery.

Hey Resist, how about share with us what you are trying to accomplish, maybe we can provide more helpful suggestions?
 

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Google is amazing!!

I just found this:

DC Watthour meter

Follow the links to :

electric bicycle battery fuel gauges; DC Amp Hour meter; Amp hour meter simulator; or FAQs

From the FAQ's, It doesn't look like it will run backwards. In other words, you can measure discharge, but you cannot measure the charging side, but at least it gives an idea of what is going on.

I also thought of another Energy unit: Electron-Volts (eV)

1 eV = 1.6 x 10^-19 Joules

So, without accounting for Mike's good point about the limited use of the battery capacity, the gauge would read:

0 to 1.94x10^25 eV

Jim - basking in the glow of my extended warranty :D
 

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Discussion Starter #19
ethicalpaul said:
Hey Resist, how about share with us what you are trying to accomplish, maybe we can provide more helpful suggestions?
I'm just trying to know if this gauge was something Honda made up on their own or it is a standard unit of measure. Since what we see in the dash shows no units of measurement I just was wondering what the actual units were.
 
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