Archives

Last year, a couple of friends of mine bought an HCH-2 and they've been generally happy with the car thus far. However, when we were comparing notes between their average FE and mine there was quite a bit of a difference.

At their request I visited them a few weeks ago just for a double check as they were not too certain if there was something wrong with the vehicle. They had also taken the vehicle in to the dealership to have them look at the presumably low FE they were getting. Naturally, as it is often the case the technicians had a look at the vehicle and they gave it a perfect bill of health. I actually know those technicians as I go to the same dealership for regular service - they are pretty good. Hummm...

Anyway, at first glance there was not a big difference between my car and theirs other than the exterior color. 20 minutes later, we got in the car, I plugged in my scangauge which was calibrated for my HCH-II and went for a short drive.

Several minutes into the drive I noticed something was very different from what I had seen before in the few HCH-2 I have driven (including mine). Event though I avoided assist the IMA battery seemed to lose its charge rather quickly. Interesting.

I also noticed that the voltage read by the scangauge was not only peaking at 14Volts but was also staying at that voltage indefinetely. Very interesting.

I turn off the car at a cul-de-sac and I let the voltage stabilize at an expected 12.X Volts level. To my susprise, it not only got down to 12 volts but it continued to dip below 12 into the low 11volt range.

At this point, after plugging my trusty motomaster 2W solar panel to the 12 volt battery terminals I unplugged the +V red terminal from the battery and placed my Fluke multimeter in series (set to DC AMPS) and completed the circuit in order to measure the current draw by all the accessories in Rod's car. (the solar power panel was also disconnected at this point). Hummm... 420 Milliamps. That's way too high a draw.

So I asked Rod, what kind of modifications he had done to the car because the current draw seemed a little too high. He walked me over to the trunk and showed me a VERY nice Blaupunkt Audio AMP system. No wonder the car's audio sounded so darn good.

Anyway, we disconnected the audio amp power and went for a little drive afterwards. After 10 minutes I noticed the voltage reported by scangauge stabilized in the 12.x volt range with the car running. That's good. Not only that but Autostop occurrend more frequently and the AS stops actually lasted quite a bit longer. We experienced no forced regens at all this time for the duration of the 45 minute drive.
The FE improved from a first run average of 5.8 liters (40.5mpg) to 4.9 liters/100km (48 mpg). The runs were performed on the same streets on a weekend with no rain and temps in the 17C (63F) range.

Moral of the story thus far:

If you want better FE then take in easy on the accessories. This includes heated seats, HID's, Amps and other high powered audio kits that many folks add to their HCH-II's.

As matter of fact, I am now seriously considering going with LED tail lights, blinkers and side markers- especially after seeing these results.

In Rod's case, the IMA SoC was inevitably feeding the accessories on a full-time basis by trying to keep the 12V battery charged. This pretty much meant that the FE was going to be impacted a little more than I expected. Not only that but I was totally surprised by HOW MUCH of an impact his accessories' power draw had on the overhall FE.

I am pretty familiar with some of the FE setup techniques based on the removal of DRL fuses and so on, but what amazed me the most if how that audio Amp (while in operation) actually dwarfed the DRL as an appliance. Geesh.

Soon after my weekend visit, Rod decided to remove the AMP (he claims he gave it to his brother in law ) and he's been reporting far better fuel economy with far less forced regens. He's picking it up pretty good since, and after our little chat today he even decided to inflate his tires ASAP to a rather commendable pressure of 44 psi. Nice.

In the past (particularly at GH), I've actually tried to discourage people from burdening their HCH-II with high powered accessories solely on the basis of good old inference. Now that I have some ad-hoc measurements, I feel more compelled to be more authoritative in that regard.

But on the other hand, not everybody who owns an economy hybrid cares about FE as much. And at the end of the day, I would rather have them driving a slightly under-performing HCH than a much larger and thirstier vehicle.



Anyway, I just figured this to be an interesting story. Perhaps instead of just alerting some folks a little, it may prompt them to reconsider their choices before they overload that little battery in the engine compartment. ;)

I am going to do some tests on my 07 Prius (before I turn it in to its new owner in a few weeks) just to see if it is affected by this issue as much. I suspect it is not affected as severely. Any thoughts & comments?



Cheers;

MSantos

Humm. That might explain why my voltage is about 11.5V when FASing ;)

If that amp is pulling close to half an amp in SHUTDOWN,
then it's flat-out defective. Or needs a power switch.
.
_H*

That's a lot of power to draw, the battery would probably become discharged in under a week if the car was left alone. I haven't seen that happen with some amps my friends have so there could have been a problem with that particular amp or its installation.

I've disabled my DRL's which is calculated to save me about 2% on the highway. Also looking into some lower powered driving lights for conditions where it's hard to be seen but lighting the road isn't necessary. It's mainly for looks but I try to use slightly improved fuel economy as justification for spending my money.

Of course, now it is too late to check whether the install of the AMP was done correctly or not, but based on my knowledge of how "hard" it actually is to tap on the ACC 12 volt line, I would venture to say that the installers simply plugged the AMP straight onto the +12V rail.

As is common nowadays, in this car the ACC power line is relayed. That means the ACC power is only "on" when the key is in the ignition and on the ACC position. So the typical approach would perhaps be to drive a suitable relay from that "signal" and then switch the power to the AMP from the +12V rail. My belief is that they left the thing "live" even when the car was "off" thinking that the unit would not "leak" significantly when no audio signal was fed to it. Again, at this point this is mere conjecture based on a little bit of the readings taken at the time.

Amazingly the 12V battery was never totally drained overnight. However, what trully surprised me was not so much the reprehensible and obvious "leaking" that occurred while stopped, but rather the impact that it had when the car was on and how it forced the IMA to persist the "charge" state.

Cheers;

MSantos

Hi MSantos:

___Great detective work if I do say so myself. I have been on Tom for over 2 years to remove that 100 #’s of dead weight from the back of his car ever since I saw the 12V hanging in the 11.8 range within 30 seconds of entering into a FAS. I think he likes his tunes too much to give it up however ;)

___Good Luck

___Wayne

My next mod will entail removal of the factory radio for more gauge space. Never listen to it, and the clock is off by an hour half the time.:D

Randall

msantos,

Very interesting read!

This is what I do to my computers! (load too much stuff, then it crawls six months later) :(

Ive watched my Bass Link. It doesn't hit me that bad. Whats bad is the sorry excuse for a battery and 12v system in the Civic. Its been a point of hate concerning Civic's from the start....

psy

...Whats bad is the sorry excuse for a battery and 12v system in the Civic. Its been a point of hate concerning Civic's from the start....



Agreed.

I think I've seen motorcycle batteries that were larger than the one on my HCH-2. Heck, even my lawnmower's battery is larger !!! :confused: :o


Cheers;


MSantos

I would venture to say that the installers simply plugged the AMP straight onto the +12V rail.This is considered the correct way to install an after market amp. The amp should have a control wire - when this wire goes hot, the amp turns on. After market head units typically have a place to connect such a wire, so that when the head unit comes on, the amp does also. If his HCH still had the factory deck, the amp was likely on all the time. :(

FWIW, I have an amp installed (a relatively small and efficient one) and I have never noticed much additional current draw when it is on. I definitely notice the draw from the headlights, though.