Odd behavior today

[biododge1]

lol! well, there goes a theory i had..(was hoping u had the new one)

[eq1]

One thing that's sort of stewing in my brain, is the way voltage for NiMH batteries behaves. As most people say, voltage (perhaps resting voltage only) doesn't really tell you much about the state of charge for NiMH batteries. That's starting to gel. Like, for instance, you can tell the SoC for lead acid by the terminal voltage only. In contrast, 'terminal' voltage for a NiMH pack can be the same whether you have a 75% SoC or 100% SoC pack, at least that's what I'm seeing...

I think SoC for NiMH is only revealed by changes in voltage under load (or temperature)... I don't really see much difference in resting pack voltage after a grid charge versus just normal day to day conditions. If anything it's a bit lower now. But I think the way voltage changes under load now, charge and discharge, might be a little different...

[3-Wheeler]

Larry,

I can not really help you that much.

I have MIMA, so background charging is out of the equation.

Also have the fan wired to run on low at all times, unless the batt temp goes up.

As Eq1 mentioned, static battery voltage tells nothing. I can see 160volts when initially turning on the ignition switch but not starting the motor. Then it drops to 154 volts after the motor is started. This is entirely due to a "leaky" replacement stick that I got from Eli, and it self discharges higher than any of the stock sticks. Of course I did not check this adequately enough before putting it in the car! Chalk it up to experience!

Jim.

[eq1]

Here's another weird behavior I saw today. As I might have mentioned, I usually get a background charge of about 5-10 amps just under 65% SoC. And I have a positive recal threshold/checkpoint at 72%, which I believe is fairly typical. Now, if I drop below 65%, I'll get the background charge and it will take SoC up to 70.2% and stop. Today, I dropped below 65%, background charge kicked in, and it took it up to 70.2% - BUT it also positively recal-ed up to 75%. Like yesterday's musing, this I've never seen before, ever. Over my travels today I lost precisely 2% capacity (yesterday I lost 5%)... And, the really weird thing is my pack voltage was quite lower than it normally is when it does a positive recal; it was only about 164, rather than the usual 168-169V...

True, I get the 'forced charge' after a negative recal and the pack seems to positively recal not at 72%, but at 60% and/or at a particular number of net amp-hours (it seems to put back in exactly enough to get the pack up to 6500 mAh, from the point at which it negatively recals. For example, if you negatively recal at 50% SoC, the car assumes or calculates that you have 3250 mAh in the pack and then puts back in another 3250). But, negative recal and forced charge is a different routine than just a typical background charge...

So... I don't know, grid charging does seem to do something to the pack beyond what the car can do alone; grid charging produces some seemingly anomalous battery management behavior. I just can't really see what the car is thinking when it decides the pack is at a particular SoC, when it decides the pack is at 75% SoC. Maybe it's the 164V mark: if the battery sits at at least 164 volts for a period of time the car believes the battery is at 75% SoC. Usually I'll get a pos recal at 72% when the car takes the voltage up to 168-169, yet it usually quickly drops to about 164-165... And yet, there doesn't seem to be much difference in pack voltage whether the battery is fully charged 100% or what the car believes to be 75%. So there's a little more to it... Pretty sure it's gotta be the rate of change in voltage under various loads, and/or something similar... Rate of change in temperature at the 4 thermistors might play a role... Just not something that can be easily spotted when all I have is pack temperature...

[diamondlarry]

With today being the third day in a row for the fan and 10-12 amp background charge and what Eli said about the 32F threshold for the pack, everything is actually normal. I don't like it at all. It was colder (18F) on my way to work and with all my coasting/gliding done with the engine running, I got 76 mpg. With the background charging, I struggled to even get 60 mpg on the way home. I wonder how many solar panels it would take to trickle charge the pack enough to warm it to over 32F?

[eq1]

I guess your calpod switch doesn't disable this background charge? Mine does for the 'normal' ones... I wish there was a way to just disable background charging altogether; it doesn't make sense for people who pay close attention to their Insight driving...

[diamondlarry]

It has been so cold lately that I'm even having the background charging on the way to work as well as on the way home; single digits. I noticed some interesting things today. When I first start off, I get 8-12A of charge and regen goes up to the 25A range. This afternoon, it got to where I was seeing 2-5A and, while regening, I was seeing the usual 4 or 5 green bars, but still only seeing about a 5A max going into the pack. It took all but about the last 1/2 mile of my 12 mile trip home before the background charge went away. I have a question for Eli and/or Peter: How high can the pack voltage go before I should get concerned? I was seeing a steady 180-181V and it would sink to around 175V after a run up through the gears after using assist when taking off from stops, then it would slowly climb back into the 180 range. I've seen it go as high as 183V.
EDIT: I'm running currently the 010 BCM.

[Willie Williford]

dialar;
Because you are in such cold weather, You have to realize the IMA sysytem is basically overcharging the batterys to get their temperature up in the "operating" range.
You might see 180V volts briefly but I don't think constantly.
Peter of Eli will explain more technical aspects.

HTH
Willie

[Eli]

I think the worry surrounding the original BCM and cold weather is more cyclical in nature. A little bit of overcharge, as we know, is good. Too much will wear the battery prematurely though.

You might want to look for an 020 BCM to see how the behavior changes, though I imagine by the time you found something and got it installed the weather will have changed.

To answer your question, 180V is fine at low currents and cold temperatures and doesn't represent an overcharge situation. Would need more like 184-186V for that.

The maximum the car will allow is 192V.

[diamondlarry]

Ha! Yeah, it'll be awhile before I get my hands on an 020. I was just on Ebay and there is only 1 020 and they want $220 for it.