HybridFan — Thanks for your voltage readings. I think that you may be experiencing exactly the same low voltages that I am finding. I had everything switched "off" when I took my readings. [By the way, in Canada the TCH has an OFF position for the headlights, but the DRLs can't be switched off. The AUTO position is after the ON position — see the Owner's Manual for both versions.] Perhaps you can repeat your readings tomorrow morning? I'd appreciate it! Here's what I find:

1. The ScanGaugeII can be woken up by pressing the Home (red ring) button, even when the car is OFF (I hadn't realized this until now), since the OBDII port remains powered at all times. Indeed, there's continual communication on the CAN bus — it's what the car's different devices use to communicate with one another — and so it must remain active. For example, if one enters an exterior door detection zone with the SmartKey, there is a signal sent from the door's antenna to the ECU that deals with such things. I discovered yesterday that the 12-V battery's voltage is monitored continuously, even when the car is OFF. So, it's actually not necessary to switch the car to ACC or ON before taking a ScanGauge voltage reading! [Other ICE-related data isn't being updated (e.g., the water temperature), since the ICE's ECU is presumably powered "off" when the car is OFF.] Just press the Home button to wake up the ScanGauge, and you'll get a valid battery voltage reading at any time.

2. This morning I opened the trunk and directly measured the 12-V battery's voltage with a voltmeter while the car was still "off" (since yesterday evening). I got 12.4 V. According to page 373 of my Owner's Manual, this is only "half-charged."

3. I then switched the car to ON, and found that the battery's voltage had dropped to 12.0 V, and continued to fall slowly to 11.9 V, and then 11.8 V as I watched on my voltmeter in the trunk. The ScanGauge inside the car gave comparable voltage readings. Now, page 373 says that 11.8 - 12.0 V means that the battery is "discharged." This should not be happening!

4. I then put the car into READY mode, and the voltage immediately rose to ~14.2 V, as the NiMH battery was now charging the 12-V battery via the dc-dc converter that sits behind the high-voltage battery unit. [Interestingly, this contains the "pre-charge" circuitry that TSB EG059-06 replaces with a re-designed module!] After the ICE started up, the voltage continued to read between 14.2 and 14.9 V as I drove the car. This seems normal. It is charging the 12-V battery when the car is in the READY mode.

5. I then parked the car and switched it OFF. I used ScanGauge (by pressing Home to wake it up repeatedly) to monitor the battery's voltage after switch-off. It dropped steadily through 13.4 V and through 12.6 V ("fully-charged"), and continued to sag slowly into the "undercharged" region. I'm sure that, if I check it this afternoon when I go back to my car, or tomorrow morning (while the the car is still "off"), I'll find it to be ~12.0 V or below.

Can you duplicate this experiment and report your readings, please? I'll repeat my experiment again tomorrow morning. This is worrying. These "absorbed glass mat (AGM)" batteries are intended to be able to survive repeated deep discharge, unlike "normal" engine-cranking batteries, and so my battery's "perennially undercharged" state probably won't have seriously affected its life, but this shouldn't be happening! If yours is doing the same, it may be that we have found a design and/or a 12-V battery manufacturing problem. These AGM batteries, from the information that I've been able to find, should not be charged rapidly, and indeed Toyota says, on page 373, that the maximum charging rate is 5 amperes. (The charging circuitry monitors the battery's temperature, and sets the charging current accordingly.) On the other hand, this battery doesn't have high current demands, and so shouldn't normally need any more extensive charging than it can be given during normal driving, unless the car is left for long periods in ACC mode, running accessories like the audio system — which I don't do. So, I can see no valid reason for this to be happening. (It's only a 48 Ah battery, so it doesn't have great storage capacity.) I'm puzzled.

If any other ScanGauge owners are out there, please measure your 12-V battery as above, and report your findings! Thanks.

Stan

 

Stan writes:These AGM batteries, from the information that I've been able to find, should not be charged rapidly, and indeed Toyota says, on page 373, that the maximum charging

Stan, I have been using the Glass Matt Batteries in aircraft since they came out,the first ones by Johnson controls and found out they will not read battery voltage like a wet cell battery when at rest. the voltages you see ar very normal for a GMB. I found early in the game that if they showed 11.5 they needed charge and would carge them like a normal battery at high amps 5-10 amps, I ruined 2 batteries before they told me not more than 2 amps tops at charge time and never again had one fail. Again i talked to a lot of battery engineers over that period of time and they set me straight on the GMB.

 

HybridFan — Let's try to get to the bottom of this Auxiliary battery potential misbehavior, please. I have repeated my experiments a number of times now, with basically the same result each time. Waking up my ScangaugeII by pressing its Home button while my TCH is still OFF, I can monitor the auxiliary battery's voltage after the car has stood overnight. I find that I get a reading around 12.3 V each time. This has remained true even though the ambient air temperature has varied quite a bit over this period, from -6 to +6 degrees Celsius. As soon as I power the car ON (but not READY), it drops to around 11.9 V. Then when the car is started (i.e., READY), it rises to 14.2 V as the dc-to-dc converter starts charging the auxiliary battery. All lights and other ancillary devices have been switched "off" for these experiments. Can you confirm similar behavior from your TCH? I'd appreciate hearing from you in this regard. Thanks! I suspect that the battery is behaving correctly, but having more than just my own data would be really useful.

It has been said in this thread that this is an AGM (Absorptive Glass Mat) lead-acid battery. Do we know this for a fact? Toyota doesn't say in their literature. Could it be a gel-cell type? From the Web, I see that both types are apparently rather similar in their characteristics, and somewhat different from flooded-cell lead-acid batteries. [For example, their voltage apparently rises rather than falls at low temperatures.]

Stan

 

Stan -- I did try to follow up on the original request last week or so but just couldn't get my ScanGaugeII to "wake up" while the car was in "OFF"... It would only give me "Connecting...", as if the OBDII port was powered off as well (or in deep sleep mode). After several attempts each following morning, I gave up and hoped someone else would try it out / follow up with you instead.

Your renewed request this afternoon prompted me to try it again tonight, but I had to "improvise" by briefly turning the car from "OFF" to "ACC" to "ON" and back to "OFF" again (1/2 sec each cycle) in order to still have the car turned off and ensure that the OBDII port was not completely powered off / in sleep mode as yet (as it probably does 10 minutes afterwards???).

At any rate, below are the sequences and readings I got before my drive back home tonight. The readings were after the car had been resting for +10hrs in a covered garage, so it's probably as good as an "overnight" test case (let me know if you don't agree & I need to repeat during a "real" morning). That said, it should be pointed out that -- unlike yourself -- I did not have my trunk open while measuring as I do not have a stand-alone voltmeter for a "physical/direct" read-out... so maybe your figures will come out slightly different simply by having the trunklight on. :-)

I completed 2 sets of tests. One set was with all "adjustable" electrical components on "OFF", incl. the main headlights, the radio, the indoors cabin light (just in case!), etc. The other set was just like the last time, i.e. with the headlights set to "AUTO" (which -- unlike the "OFF" position does include DRL's being turned on here in the US, as you very well know). Each series was repeated a couple of times to make sure I got accurate/sustainable figures. Also, each test set went through the Steps 2 thru 5 as you described before, i.e. "OFF" to "ON" to "READY" and back to "OFF" again. Finally, each step was kept in that "position" roughly 5-10 secs, save for Step 5 (which took quite a bit longer, obviously).


(A) All adjustable electric components OFF:
2. "OFF" -> 12.4/12.5 V
3. "ON"" -> 12.2/12.3 V
4. "READY" -> 14.1/14.2 V
5. "OFF" -> sudden drop to 12.9 V, 12.7 V, 12.6 V... eventually stopping at 12.4/12.5 V

(B) Headlights on "AUTO", main cabin light on "DOOR" (but doors closed):
2. "OFF" -> 12.4/12.5 V (same as above, duh!)
3. "ON"" -> 11.9/12.0 V
4. "READY" -> 14.0/14.1 V (not quite 14.2 V as yet, not sure why)
5. "OFF" -> sudden drop to 12.4 V... eventually resting as 12.1/12.2 V (as the headlights remained on for 30 secs), then back to 12.4/12.5 V


Finally, an FYI that after my commute I did quickly scan the gauges again (as I usually have it on TRIP-related scans, not GAUGE). It was up to 14.6 V right before I powered it off for the night, at which point (yet again!) it quickly faded 12.8/12.7 V and ultimately resting at 12.4/12.5 V...


Hope this helps... I still suspect the diff'ce between 12.4/12.5 V and 11.9/12.0 V while "ON" but not "READY" has to do with usage of any electrical component, incl. either the trunklight or your "forced" DRL's perhaps?

 

HybridFan — Thank you for trying to make the battery voltage measurements I requested. One of the reasons why I started monitoring my TCH's 12-V battery voltage was that I had been experiencing the same "Connecting ..." issue with my ScanGaugeII that you have now reported! When I told Ron DeLong of Linear-Logic (the manufacturer) about this, he suggested that I was suffering from a momentary 12-V battery "brown-out" (drop in voltage) that misled ScanGaugeII into thinking that it had been disconnected — hence its attempt to re-Connect. I had been trying to see if I indeed had a brown-out problem by monitoring the TCH battery's voltage. I had seen no substantial voltage drops occurring, however, and so had told Ron that I could see no evidence of a brown-out. Ron was coming to the conclusion that my ScanGauge (or TCH!) might be behaving abnormally, when you reported the same issue with your ScanGauge yesterday!

Here's what I have learned from Ron and from my own investigations so far:

1. ScanGaugeII will try re-Connecting if it sees the battery voltage dropping below 3 V for more than 100 ms. It will interpret this as a disconnection, requiring it to try Connecting again. I've never seen such a low battery voltage, and I'm sure this isn't happening.

2. ScanGaugeII wakes up when it sees a voltage rise of at least 300 mV over a 1.3 s period. This occurs when the TCH is switched from OFF, ACC, or ON to READY. The voltage then rises to 14.2 V as the NiMH battery starts charging the 12-V battery through the dc-to-dc converter.

3. When "on" with its LCD display on "White" and "High," ScanGaugeII draws a current of ~100 mA from the 12-V battery. When sleeping, it still draws a current of ~40 mA from the OBDII port (which is permanently powered). [Incidentally, this residual drain will consume ~1 Ah of charge every day. The 12-V battery is a 48 Ah unit, and this drain would discharge it over a period of a month or more. So, ScanGauge should be disconnected if the car is to be unused for more than a few weeks. I can now confirm that the 12-V battery is an AGM type — see page 4 of TSB PD020-06 posted to this group by schmidtj.]

4. If I make sure that my ScanGaugeII is showing the Gauges screen with VLT displayed when I switch my TCH OFF, then I can usually (but not always) wake it up by pressing its Home button without triggering the "Connecting ..." problem. It will then display the current battery voltage even with the car OFF, and then go back to sleep. I think you must be on this Gauge display screen when switching OFF for this to work — I don't think you can change the display without triggering the "Connecting ..." problem. This may be why you couldn't make the measurements with the car OFF.

HybridFan, can I trouble you to try this and see if it works for you too? Thanks! If so, you should also succeed in making an early-morning measurement with your TCH OFF, and disturbed no more than by opening its door. Let me know what happens. I would like to suggest that you also drop Ron DeLong an e-mail at ron.delong@linear-logic.com and let him know that you're having the same "Connecting ..." problem as I'm finding, and that you also have a TCH. It looks to me more likely to be a ScanGaugeII programming issue than a TCH battery problem. That said, however, I'm still puzzled by the battery's low voltage readings after standing for many hours. It's almost as if the battery is draining significantly while the car is OFF. I'm currently attempting to make some readings, using a current probe, to see what the standby current is from the 12-V battery when my TCH is OFF. I'll report back on what I find.

Stan

 

Dear All — Here's my report back on my battery measurements, as promised, and a further comment on the original issue, namely, what needs to be done after disconnecting the 12-volt battery.

1. On the battery front, I think that all is well, and that this was a false alarm. Here's what I found from my careful measurements of the 12-V battery's voltage (both directly at the battery terminals and also as reported by ScanGaugeII) and current measured with a clamp-on current probe, after my TCH has stood unused overnight:
(a) About 1 minute after the car is switched OFF, assuming that there are no ancillary devices still drawing power [like ScanGaugeII, which draws some power from the (always powered) OBDII port even when asleep], the battery current drops to as near to zero as I can measure with the current probe. After standing overnight, its terminal voltage is ~12.6-12.8 V.
(b) When the car is put into ACC mode, the current drain is ~4.5 amperes. The battery's terminal voltage drops to ~12.3-12.4 V (and ScanGaugeII reports ~12.2-12.3 V).
(c) When the car is switched to ON (but not READY), the current drain rises to ~9.7 A. The battery's terminal voltage drops to ~12.1-12.2 V (and ScanGaugeII reports ~11.9-12.0 V).
(d) When the car is put into READY mode, but before the ICE starts, the battery current reverses to ~15-20 A charging, as the dc-to-dc converter begins charging the 12-V battery from the high-voltage NiMH battery (and ScanGaugeII reports ~14.2 V).
(e) While driving with the ICE running, ScanGaugeII reports that the 12-V battery's voltage varies between 14.7 and 14.9 V until it is fully charged, when it drops to ~13.7 V.

It was the low ScanGaugeII voltage readings in conditions (b) and (c) that triggered my initial concern that the 12-V battery appeared to be seriously discharged after standing overnight. Note the differences between the actual battery terminal voltages and those reported by ScanGaugeII in cases (b) and (c). The terminal voltage is okay, but ScanGauge's readings were worryingly low. Question: Why are ScanGauge's readings low? Answer: I believe it's because of the resistance of the 140 A fusible link that's built into the 12-V battery's positive terminal clamp. I estimate that its resistance would have to be of the order of ~0.02 ohms, if it is to melt when subjected to a 140-A current, and at the currents measured in conditions (b) and (c), the voltage drop across this fuse would amount to the 0.1 V and 0.2 V differences (respectively) that I measured between ScanGauge's readings and the actual battery terminal voltages. If I'm right, all is well with the 12-V battery. Good!

2. I have spoken to the expert "hybrid" technician at Forbes Waterloo Toyota, and he believes that the "idle speed re-learning" only needs to be redone after disconnecting the 12-V battery if there's a problem starting the ICE. He says that the idle speed re-learning is normally done automatically and adaptively as the car is driven, and so this re-initialization procedure isn't normally required each time the 12-V battery is disconnected. This sounds reasonable and sensible to me. Please let us know if you learn anything different on this issue. Thanks.

That's the promised update. The best of 2007 to you all!

Stan

 

Stan, thank you for the great information and all of your hard work. I never expected this kind of evolution to my original question. I continue to learn more about my car everyday thanks to you and people like you who are willing to share what they know about their cars.

Regards,
Ray

 

Very good artical Stan! Thanks

 

A bit more information — Further to my Post #26, the 12-volt battery's current will not drop to quite zero after 1 minute of inactivity, as I stated, since the TCH's SmartKey system initially keeps transmitting (at a rate of 4 times per second) trying to make contact with any fobs in the vicinity. This will draw a small amount of battery current (maybe a few tens of milli-amperes). According to the New Product Features (Functions?) Manual (posted to this site), page BE-125, if no fob response is received for more than 5 days, the TCH increases the transmission interval to 3/4 second; and then after 14 days without response, it deactivates the SmartKey system completely, thus reducing the current drain to precisely zero after 2 weeks. As the Owner's Manual tells you, in order to reactivate it you then need to use the fob button or mechanical key on a door or trunk lid.

Stan

 

This is a slightly on and off topic question. So I apologize.

Here goes....

If you have a peripheral device that draws power, for example a audio amplifier, normally you connect this directly to your 12v car battery. In the TCH, would you follow the same principle?

Mike

P.S. -- awesome work guys....this thread has a TON of info in it!