Any enterprising person want to disable IMA? - Page 7 - GreenHybrid

CGameProgrammer · #61 (**permalink**) 12-15-2005, 04:38 PM

Quote:

Originally Posted by NASAgineer

But the PCU already protects the pack by limiting assist when SoC gets low, why would it need to do anything special in S-mode? It could simply give you assist until SoC drops too low just like it does in D.

Right, and then you have no assist when you need it. In D you quickly use up the battery and then, once over the hill, you have to drive a while to recharge the battery and don't have its assistance until then. Why bother using up the battery just to help go up 1/2 of the hill?

Quote:

And it does give assist at lower speed in S-mode, I just don't get why it cuts out at higher speeds, why is it speed dependent?

Because people don't drive very long at 10 mph; they're only going slow for a moment as they pick up speed. Assist is perfectly fine to help get them going, for a short period of time.

NASAgineer · #62 (**permalink**) 12-15-2005, 04:43 PM

Quote:

Originally Posted by slajeune

I was in stop and go traffic today and I tried the S mode (it is the recommended driving mode for such an event as per the manual). Althought the assist seems more intense, it does taper off VERY quickly. You will see the assist jump up to about 4 bars of assist and taper off with 2 seconds to 0 assist. At least, that was my observations on my drive home. Does this look like what you got NASA?

That makes sense now that I think about it. The ECU interprets the throttle position as a desired power setting. As the ICE RPM's go up, it develops more power so less assist is needed to meet the desired power. In S-mode, the RPM's go up faster, so the power develops faster and assist can drop sooner. I think that's what Elan was trying to say; I just wasn't getting it

. I hadn't really watched it to see how fast it drops off.

I'm wondering is S-mode might be a better way to pulse given that you can get up to speed faster without battery use. You use more gas during the pulse, but the pulse is shorter, so it may actually use less gas overall. Plus, less regen hit later. More experimentation is needed...

NASAgineer · #63 (**permalink**) 12-15-2005, 04:48 PM

Quote:

Originally Posted by dshelman

I'm a little confused about something -- okay, maybe a LOT confused... I thought assist was a good thing, allowing the ICE to rest a little. So, why are we trying to be conservative with assist mode? I understand not wanting to run the battery way, way, way down, but some of what I've read *seems* to imply that assist is bad or negative.

Can someone straighten me out?

Thanks,

Don

It is a good thing in general, but assist use has to eventually be paid back with regen (with interest). If you are going down a steep hill, or you need to stop anyway, you get that regen for 'free', but if you are accelerating up to speed on the freeway and you have to pay back the regen while cruising, it can hurt FE overall. That's the case we're talking about here.