12V Battery Voltage Question

[JoeMultihuller]

I just bought a 2002 Insight with 17,000 miles on it. Having just spent over four years living on a boat off-grid, I've become very attuned to 12v battery happiness.

Inasmuch as I'm an Insight newbie and am experiencing some fairly significant IMA battery level variations (perhaps normal, as I live in the hills), I thought I'd first monitor the 12v battery voltage level just to get an idea of its normal behavior. So we went for a pleasant 80-mile drive in the country (av'g. 64.3mpg - I'm still learning)...

I simply plugged in a digital voltmeter into the accessory socket and expected to see a fairly steady float voltage somewhere around 13.5v. I was shocked by the results: this voltage VARIES RAPIDLY and ranges from 13.6v down to 9.8v, often sitting in the 10v range for minutes at a time. I couldn't correlate this to either IMA level or IMA charging/discharging status nor to engine revs nor lights/accessories. Made me suspect that I have an intermittent shorted cell or two in the 12v battery. After letting the car sit overnight in the garage, I measured 12.37v across the 12v battery without turning anything on. Perhaps a little low, and maybe time to search for a battery replacement...

Our Insight came with a factory-original "Maintenance Free" wet-cell semi-sealed battery which I presume contains plates which are lead-calcium. These batteries are optimally charged at14.8v and prefer float voltages of 13.1v-13.4v (a little lower than the 13.6v I measured).

(deleted long-winded technical discussion comparing all sorts of battery types)

The favored replacement for our Insight's stock battery is the Hawker Odyssey which is an AGM VRLA. The OdysseyFactory.com website recommends charging at 14.4v-14.7v and floating at 13.6v-13.8v. Not a problem, and should be quite compatible with whatever the voltage regulation is from our DC-DC Converter (i.e., if it works with the MaintenanceFree battery then it's just fine for the AGM, presuming it's got a current limiter which will accommodate the AGM's lower internal impedance).

So far so good, and I'm about to place an order for the smaller (lighter) Odyssey PC545 , together with custom aluminum mounting bracket and terminal adapters. This smaller battery was selected since I live in a mild climate, we don't need deep-cycle capability (playing the stereo while parked for a few hours won't deplete it), and if we have to crank for more than five seconds using the starter, something else is wrong.

Before I do that, however, has anyone else monitored their 12v? If so, what are the voltage variations experienced?

Thanks in advance, and thanks to those who previously discussed and showed pictures of their replacement 12v batteries, and sorry for being so long-winded.

[Billy]

I think the PC545 is the best choice. I have had one for several years in my airplane, and it does a SUPER job. It has plenty of cranking power for my 105 hp engine, even in sub-freezing temps. It already has lasted longer than a standard lead-acid battery........Billy

[Willie Williford]

I have a "Battery Gauge" permanently mounted in my Insight. It is connected to one of the hot lead on the cig. lighter.
In the AM (first start) and the first position on the ignition switch shows 12.5 volts. Second position on the switch shows 11.7 (No load other than the computer loading, etc.)
While running, (idle) the voltage will indicate between 13.5 and 13.9 volts, even with a "max. load" (lights, radio, fan, AC) the gauge reads 13.8 most of the time and never below 13.5 volts.

I use a "Hawker" Genesis 12V13A, weight 10.8 pounds and it was installed on 12/3/03 after being used on a "heart monitor" machine for 2 years. (Bought used) for $15.00. Have started the engine 4 times with the 12V battery when the IMA battery "overheated" during a summer trip. No problems since installation.

PS
Haven't seen a factory installed battery that is maintenance free. The "eye" of the battery is deceiving.

Hope this helps.

[JoeMultihuller]

Hi Billy and Willie,
Thank you both for your feedback. You're right, even though it says "Maintenance Free Battery" right on its case, a lead-acid wet cell needs occasional nourishment. Off to buy the PC545...
Joe

[JoeMultihuller]

Installed a Hawker Odyssey PC545 battery using a battery box from West Coast Batteries (http://www.odysseybatteries.com/pc680hd.htm) and my own two custom anodized aluminum brackets. Removed the original Insight battery box. The pieces can be seen on http://www.KatieKat.net/Vehicles/Insigh ... gParts.jpg
The installation:

The only permanent mods to the Insight are two 6x1.0 screw holes I drilled and tapped into the box crossmember. Used all eight of the original battery-mounting screws and added two 1/4x20 stainless screw/washers/locknuts (don't have any metric SS on hand).
The longer bracket also attaches with two screws to a control bracket underneath (the two screws just visible in the photo).
Placed a piece of foam between the battery and the crossmember.
The original battery ground cable was excessively stretched, so I replaced it with a longer one (12" would be fine, but all the local autoparts store had was 19"). Kept the original ground cable (attached redundantly) in case I need an on-the-road battery replacement.
A brief test run showed no more excessive 12v voltage variation, with the voltage hovering around 13.6-13.8v when the dc-dc converter is kicked in, but dropping to about 12.2v when it occasionally opens up (haven't figured out its logic yet).
Thanks to all who contributed to the previous Forum 12v battery discussions and mods.
JoeS.

[jsnable]

Hey Joe,

Nice install! I will look into the Hawker battery as I know my 12V is close to shot.

Also, hello from another LAH resident (Robleda Road). I will keep an eye out for another silver Insight around town...

Jay
2000 Silver

[Armin]

Joe,

I have a theory for the DC-DC turning on and off seemingly at random:

A) at very low loads, the DC-DC is very inefficient. It draws at least 1.5A from the 144V system in addition to what it needs to supply the 12V side. (This is common for SMPS)..

B) Maybe Honda was concerned about constantly floating the 12V battery at the fairly high level they use. So they turn off float when there is no or little load and only turn it back on when the voltage drops below a certain point (I seem to remember it was 12.0V, but I don't have my notes handy).

In either case, with the engine running or in auto-idle-stop, I have never seen the 12V side drop as badly as you reported. Where do you measure the voltage? Maybe it's the drop across a fuse or wire?

[JoeMultihuller]

Hi Guys - thanks for the notes.
Jay, I sent you a PM.
Armin - I am simply measuring the battery voltage at the accessories connector which looks like a cig. lighter outlet, but with no load I would expect it to be reading the battery voltage reasonably accurately (depending where their pickoff point is - I just received the service manual and haven't delved into it yet). On my list of things to do to the Insight is to put in some decent battery monitoring instrumentation; e.g., http://www.katiekat.net/Cruise/KatieKat ... ifications
I hope to be much smarter about the car when I return from a 2Kmile trip in a couple of weeks - barely driven it since I bought it - it's been raining Don't get the wrong idea - all my other cars get washed once every five years, whether they need it or not - and the original paintjob on my '67Saab is still good - waxed it once, back in '68
JoeS.

[nemystic]

The info in this thread is starting to raise concern, as next week’s cold weather in the northeast could possibly necessitate 12 start(s).

I have the original 12V battery, to which I added distilled water about 7 months ago. I’m not aware of any specific problems, as the period between re-cals has often been several months.

Since “Sputnik” doesn’t have A/C, I sometimes operate an interior 12V fan in the summer. I’ve noticed the fan speed changes frequently and significantly, with a consistent correlation to driving conditions. (I don’t remember all the specifics, but regenerative braking is one of the events that always ramps up the fan speed. I’d thought this was normal for the Insight.) I haven’t checked the voltage yet (while driving) with a DVM, but my guess would be that the voltage is varying by at least 10%, probably more.

If I have a chance to make some measurements (with and without fan motor load) I’ll post the results.

[nemystic]

Please reference the previous messages for context of the following observations.

The following voltage measurements were made on the 12V accessory connector (traditional “lighter”) with approximately 30 degrees F outdoor temperature. The garage temperature at initial starting was approximately 45 deg. F. All but one measurement was rounded to the nearest 0.1VDC.
‘Apologies to fellow engineers for not presenting this in spread-sheet format.

Start switch on, engine off: 12.3VDC
Start switch on, engine off, peripheral 12V fan on: 12.1VDC
Engine on, peripheral fan off: 14.0VDC
Engine on, peripheral fan on: 13.95VDC
Normal driving conditions: 14.0VDC +/- 0.4%
This includes:
Headlights on;
Regenerative braking;
Auto Stop (engine temporarily off)

I stopped the car and turned off the engine after approximately 10 miles and made the following measurements:

Start switch on, engine off: 12.6VDC
Engine on, normal driving conditions: 14.0VDC +/- 0.4%
This includes:
Headlights on;
Peripheral fan on;
Regenerative braking;
Auto Stop (engine temporarily off)
Maximum battery (IMA) assist;
Headlights, internal fan, peripheral fan, and tape player on.

Quite unlike my observations last summer, there were no noticeable variations in the peripheral fan speed under any of the conditions listed above.

Conclusions:

Considering that the “12V” battery voltage was very stabile (at 14 volts) under nearly all typical driving conditions after the engine ran for over 1 minute;
 The OEM 12V battery performance may possibly be maintained for 3 years + with the addition of distilled water, and/or;
 Variations in battery voltage (12V) are less likely at northern USA winter temperatures.

Hopefully, with the help of a passenger, I’ll have a chance to check and post measurements next summer.

CAUTION: As a safety consideration, please don’t attempt to read peripheral instruments while driving.

Despite hesitant periods of contemplation, “Sputnik” had no 12V starts this past week, despite 2 days where the daytime temperatures in my workplace parking lot didn’t exceed 10 degrees F.