Enertia's charge meter accuracy

[lumberjackprince]

I know that measuring the charge remaining is tough to do accurately but I'm curious if mine is a little wonkier than others or if my conditions are the cause. When I leave for work, on the first two miles I loose 20% of my charge, even though my speed averages 30mp for those first two miles. The normal temp when I leave is around 40F.

It is 15.2 miles to work and the charge normally reads around the high 30%s when I arrive. Then, when I plug it in, the charge normally read around 50%, like I would have expected averaging 35mph. It does take the specified time to charge, which makes me believe that the remaining charge listed while I am charging is the more accurate number.

I am happy to find that charging after only drainging it halfway is fine (from the other thread today) but I'm curious if others have the same high consumption reading at the start or is this just from it being sooooo coooooold and me too stubborn to take my car?

[HighlanderMWC]

So far most days have been at 51F when I come to work. My first 2 miles are at 30-35mph and then I have a hill at 45mph. I don't recall ever being below 90% after the descent on that hill, usually 92%.

I usually only get fast drops in the readout below 50%...but that's always at night (just a little bit cooler here).

[BrammoBrian]

Originally Posted by lumberjackprince

I know that measuring the charge remaining is tough to do accurately but I'm curious if mine is a little wonkier than others or if my conditions are the cause. When I leave for work, on the first two miles I loose 20% of my charge, even though my speed averages 30mp for those first two miles. The normal temp when I leave is around 40F.

It is 15.2 miles to work and the charge normally reads around the high 30%s when I arrive. Then, when I plug it in, the charge normally read around 50%, like I would have expected averaging 35mph. It does take the specified time to charge, which makes me believe that the remaining charge listed while I am charging is the more accurate number.

I am happy to find that charging after only drainging it halfway is fine (from the other thread today) but I'm curious if others have the same high consumption reading at the start or is this just from it being sooooo coooooold and me too stubborn to take my car?

Sounds like old battery state of charge algorithm to me. I'd give your service tech a call...

[lapwing]

Don't underestimate just how tough it is to estimate what's left in the tank. The same very tight no sag voltage characteristics that make LiFePO so sweet as a power source, make it pretty tough to gauge state of charge.

[Richard #230]

Originally Posted by lapwing

Don't underestimate just how tough it is to estimate what's left in the tank. The same very tight no sag voltage characteristics that make LiFePO so sweet as a power source, make it pretty tough to gauge state of charge.

That is why it seems to me that using the amp hours used display on my bike is a better way to estimate energy consumption and the amount of juice left in the battery system. Voltage seems to move around so much on my bike that I can't tell what is really going on. At least power consumption is a solid number. When my 50Ah system hits 40Ah of usage, the power really does drop very noticeably all at once. Now I know what the limits are and can stay away from the point where the batteries drop off the curve.

[BrammoBrian]

Richard,

The Enertia uses an algorithm that predicts state of charge based on multiple battery characteristics, including, but not limited to, voltage and current. The issue seen with Lumberjack's bike is a known issue relegated to a very limited number of bikes that left the factory before we were issued an updated algorithm from Valence based on some testing results we provided. The current algorithm is quite effective at predicting charge remaining and eliminates the tendency for the SOC to increase once the bike is at rest and the battery voltages rebound.

[Richard #230]

Thanks for the comment, Brian. I wasn't thinking of the Enertia, but only with regard to using a voltmeter to determine battery charge. Obviously I have no knowledge about the specifics of the design of the Enertia. I have no doubt that Brammo did a thorough job of developing the bike's charge meter.

I might add that when I picked up my GPR-S I was told to use the voltage display as a guide to the battery capacity remaining and not to rely on the Ah-used display. In my case, I decided to ignore that advice.