What's your volt meter reading when cruising around town? Options

[raynekat]

Just curious what the typical volt meter reading is:

1) when you're sitting at the stoplight

2) cruising down the boulevard at 3-4000 rpm

Trying to see if I'm seeing typical or low readings
Thanks

I just recently noted a low charging issue that I believe came down to an alternator/voltage regulator mismatch.
I was using a Bosch VR with my Motorola alternator.
Now I've switched to a Marchal VR and the charging voltages look better.
About 13.75 volts while cruising.

[Superhawk996]

My car still has normal light bulbs in all the gauges including the generator light. The generator light appears to act normally. Turn the key, and the generator lamp lights up until you start the car. When I first start it up, I get a small glow until I blip the throttle and get the revs up, and the light disappears. After a few minutes warming up on the hand throttle, upon release of the hand throttle and idling at about 700-800 rpm, you don't see the generator light.

The engine is your standard MFI with the CDI box arrangement.

When I had my issue, I had the headlights on, brakes on and wipers on plus the engine of course.

I'll pick up one of the current clamps that you mentioned here in the next day or so, and report back on what I find. Is it easy to measure DC current? Or are we measuring AC current? Thought most everything on the car was DC.

Glad to hear the Generator bulb is still incandescent. That takes one variable out of the loop. Seems to be working properly.

Don't underestimate a CDI current draw. Quick info I can find seems on Summit Racing site for a Mallory CDI indicate about 0.7 to 0.9A/1000 rev's. So at a 3000 RPM cruise, that is 2.7A just from that device alone.

We are measuring DC current.

With a current clamp it is super easy non invasive measurement.

Just place the clamp around the red wire that leads from the alternator to the B+ source (actually starter motor terminal IIRC) to see what the alternator is doing on its own (is it sourcing current to the battery, how much current, etc).

Likewise, if you want to see the net inflow/outflow of the battery, you can put the clamp around the large (like 4AWG gauge) red battery wire. This is where you would be able to see what your actual electrical loads are that the battery is sourcing current to.

There are hall effect AC/DC current clamps that can read both AC and DC current. The super cheap ones (like $30) usually are AC only - you don't want one of those. However, I think last I looked, you could find one that measure AC & DC for about $80.

Just be sure that it has something on the order of a 0-6A or 0-10A low range for DC current. Be sure to look at specs on low end units. Sometimes the range is 0-60A; depneding on the accuracy, something on the order of 6A load might very well be +/- a couple of amps which might make it difficult to see what is going on. Could definately tell current direction (charging or not charging) but it might be hard to see if the Li-ion BMS is throttling current by a couple amps.

[raynekat]

Here's the current clamp I purchased.
Took quite awhile to find the right one as most on eBay, Harbor Freight, etc only do AC current.
I wanted DC current.

This Uni-T UT210E from China (oh why oh why can't Americans make something like this for a decent price?).
It was $62.48 delivered.
How can you go wrong? (IMG:style_emoticons/default/blink.gif)

The specs that I was most interested in:
DC current
2.000A with 1mA resolution and +/- 2%+8 accuracy
20.00A with 10mA resolution and +/- 2%+3 accuracy
100.0A with 100mA resolution and +/- 2%+3 accuracy

So the selector can choose between 3 ranges for current.



https://www.ebay.com/itm/New-Uni-T-B4Q094-U...353.m2749.l2649

Guess the next question is where exactly would I measure for current draw?
On one of the main cables coming out of the positive terminal from the battery?

[raynekat]

On a positive note, I checked the charging at my battery with the car running about 2500 rpm.

It was measuring 13.85V which seems like a decent enough value for the alternator/voltage regulator system.

[Superhawk996]

Guess the next question is where exactly would I measure for current draw?

See my previous post for suggested locations. (IMG:style_emoticons/default/smile.gif)

Interested to see what results you get on actual current draw.

[raynekat]

Superhawk....I think you were dead on about that Lithium Ion battery not being "big" enough.
It just doesn't have the reserve to keep up with the electrical usage on the car.
This is what I measured on one of the big cables coming off the positive terminal on the battery.
The values you see listed below is the total reading I read off the clamp meter....not what each additional component added to the total (i.e. engine running with running lights on was 6.6A....the running lights alone were something close to 3A).

At idle (baseline): 3.6A

Add running lights: 6.6A (only about 3A added, Spoke's LEDs in rear, normal in front, with LED side marker bulbs)

Add headlights: 9.2A (guess the 914Rubber LED headlights are fairly energy efficient...added 2.6A)

Add front fog light: 16.1A (these are normal bulbs...about 7A)

Add rear fog light: 18.2A (again a normal bulb.....only about 2A added)

Add wipers on low: ~25A (the meter was really jumping around with the wipers)

At idle with wipers only: 8-10A (about 6A added)

So the 30 Amp-hr rating on the Lithium-Ion battery is not enough to keep up with all these loads turned on at the same time. I didn't even try adding the defroster fan or higher wiper speeds as the car (or built-in circuitry of the battery) turned itself off pretty quickly after I added the wipers and got the load up in the 25A range.

Luckily the battery always keeps a reserve allowing a couple of restarts after it shuts itself off. So the battery operated as advertised it seems.

Takeaway..... This battery is OK for race cars (autocrossing) and driving around town during the day in nice weather. Which is what I will likely only be doing. Any nighttime or distance driving and I'd want a different battery. I'll definitely be thinking about moving up to a 50-70 Amp-hr battery this Spring at any rate.

[Superhawk996]

Nice work and great information for the community. Thanks for taking one for the team! (IMG:style_emoticons/default/cheer.gif)

Yeah, that is definately too much for a 30Ah Li-ion battery.

So reported numbers are at idle, I know it would be hard to document running over time, on the road, but I'm 99% sure you will have two things occur:

1) Any battery (including Lead/Acid) will begin to lose cell to cell voltage as it discharges and current will drop accordingly according to Ohms law I= V/R where R is fixed by the components. Actually I'm 100% sure on this one!

2) Ultimately the battery managment sytem (BMS) will end up disconnecting the load (internally) to the battery so that the Li-ion battery doesn't completely discharge, which would harm the battery. On the way to that point, a Li-ion BMS MAY begin to throttle current to the load as cell voltages dip depending on how the BMS was designed to operate. I think it your case, it didn't throttle current since you said it allowed up to about that 25A draw and then just suddently disconnected.

Out of curiosity, did you get the current clamp around the alternator ouput wire (B+ that goes to starter)? I'm sure you're alternator is pumping out some juice to help offset the draw when you're running which explains how you are able to get more than say 1 hour of running time if you were indeed drawing 25A total on just the battery.

Alternator is 50A so in theory it should offset completely but the reality of stop & go driving is that you're probably spending more time idling than you think and at that point, the battery will have a hard time keeping up and you'll see the dimming that started the thread discussion.

[bbrock]

Thanks for posting those number Doug! This is something I've been very curious about. Especially the draw with LED lights. (IMG:style_emoticons/default/beerchug.gif)

[GeorgeRud]

Makes me long for the days of ammeter gauges on the dash. I did install a voltmeter in the ashtray area to be able to keep track of system voltage at least. However, the glowing light is a good backup and much better than nothing.

[GeorgeRud]

Usually reads about 13.5 volts while driving. I don’t know how accurate the VDO voltmeter is in comparison to the plug in ones (but I do use one in the cigarette lighter socket on my 911.

[Spoke]

...I don’t know how accurate the VDO voltmeter is in comparison to the plug in ones...

I measured the VDO voltmeter in my car and found the voltmeter to be within 0.1V in the 8 to 16V range. The real error as we all know is connecting the voltmeter somewhere in the 914 wire loom where voltage drops are common.

[VaccaRabite]

Out of curiosity, did you get the current clamp around the alternator ouput wire (B+ that goes to starter)? I'm sure you're alternator is pumping out some juice to help offset the draw when you're running which explains how you are able to get more than say 1 hour of running time if you were indeed drawing 25A total on just the battery.

Alternator is 50A so in theory it should offset completely but the reality of stop & go driving is that you're probably spending more time idling than you think and at that point, the battery will have a hard time keeping up and you'll see the dimming that started the thread discussion.

I've got an Odessey PC925 battery in my car and I can confirm some of this for sure.

It works GREAT for trips where weather is not a problem, night or day, and has a TON of cranking power.
As soon as I turn on the wipers though I can watch my volt meter start to dip as I drive, until it settles in at about 10.5 volts.
The PC925 is listed as a 28AH battery. One of my tasks for this year is to get a more conventional battery with a better AH rating.

Zach

[raynekat]

Here's what the "offending" battery looks like for those curious.
It's made by a company called Antigravity.
And this particular model, RS-30 with Restart, is no longer manufactured by them.
It's light weight....about 11.5 lbs and has a battery hold bracket available.
The bracket was slightly too wide to fit in the stock 914 battery tray, so I took it down to a local water jet company and had them carefully trim it to fit.
The bracket is aluminum.



A pic of the battery/bracket installed in the 914.



Unfortunately it will likely not be a great choice for more of a "daily" driver type of car.
For only the occasional Sunday drive (in nice weather), auto crossing or track days, I think this is a great option. It definitely starts up the car without any issues.

Scary part of the the Antigravity battery line-up is that the battery I had purchased was by far the battery with the largest amp-hr rating.
Most are much smaller than the 30 amp-hr the above battery has.
So they are indeed only "starter" batteries....for starting up your car and not much more.

[raynekat]

Looking at one of these AGM batteries as a replacement for my Lithium-Ion.
Looks like it has plenty of AmpHr: 62.
Weight is a bummer (41 lbs), but that's what a daily driver battery weighs it seems.
And not inexpensive as automotive batteries go.
Terminals appear to be in the right locations....a big plus.
Will do a bit more research on them.
There is an Odyssey that would fit and has 55 Amp-Hr but the terminals are wrong.



Here are the specs:

D4700
MSRP: $321.99

12V BCI Group 47 AGM Battery, Max Amps 2,900A, CA: 760A, Ah: 62, 2000W / 3000W
Weight Lbs. – 41.19
Weight Kgs. – 19.14

Length – 9.49 in
Height – 7.48 in
Width – 6.93 in

MAX Amps – 2900
CA – 760A
RC - 110
Ah - 62

M6 Terminal Hardware Included

3 Year Warranty

[raynekat]

Received my new battery today from JEGS.

Man is it ever heavy (~42 lbs) compared to the Lithium I'm replacing (~11 lbs).
The new battery has a bunch more Amp-hr.
62 Amp-hr vs 30 Amp-hr for the Lithium.
Should do a lot better keeping up with the electrical load while driving around, sitting at stop lights, etc.

So it's an XS Power battery, model D4700.
This is one of those AGM batteries so acid leakage won't happen.
Specs:
12-Volt
CA: 760
CCA: 668
Ah: 62, 2000W / 3000W
Max Amps: 2900
Reserve Capacity: 110 Minutes

I purchased mine for $279.99 including shipping.
I think the price is very competitive for this type of battery.
Also needed is a set of battery terminals for another ~$10.

Some might not like the flashy looks, but I think it's fine.
You could always come in with some cut vinyl to hide them....



ps I did have the battery terminals reversed for this pic. The larger one goes on the positive terminal. Ha

[raynekat]

So the real important thing for me is fit in the car.
I obviously did all my measuring before purchase and this battery looked perfect.

And it was.
Fits the stock battery tray perfectly.
Even the stock hold down clamp works nicely.
This battery has the necessary "cleats" front and back such that it is very secure when clamped in place.
Not too tall.
Can't tell you if the rain tray would get in the way as I don't run one with my six.

Another super important thing is that the terminals are in the correct location with the negative closest to the firewall.
It was like this battery was meant to go in a 914.

I may get a bit creative with some vinyl and some graphics to change to cosmetic looks of the battery, but that's a minor issue in my mind at this point.

Time to drive and enjoy the car without worrying about the battery any more. (IMG:style_emoticons/default/first.gif) (IMG:style_emoticons/default/beerchug.gif)

[ctc911ctc]

Kitty Forman : So, what do you want for your birthday?

Red Forman : Whatever you want. Money is no object, as long as it's reasonable.

Eric : I want a cassette player for the car. A cassette player, not an 8 track. NOT an 8 track. Okay?

Kitty Forman : Why don't they put record players in cars?

Red Forman : OK, Eric, if you don't want an 8 track, you won't get one.

Kitty Forman : Oh, but Red, he wants one.

Eric : No, I don't. I don't want an 8 track.

Red Forman : You'll get a Delco. A genuine GM part for a genuine GM car.

(IMG:style_emoticons/default/beer3.gif) (IMG:style_emoticons/default/beerchug.gif) (IMG:style_emoticons/default/beer.gif) (IMG:style_emoticons/default/drunk.gif)

I seemed to remember there was a gold foil sticker indicating matching VR to altenator,don't know if it was on the 914/6 as it looks like a 911 part.
Found this pic;

[raynekat]

My car had 2 issues.
1) non matching voltage regulator to the alternator
2) battery with insufficient Amp-hr rating

Now all is well in the Kingdom of Oz.

[FlacaProductions]

@raynekat - that's a really good find and while I think the graphics are a bit "much" I'll say that the white doesn't look bad at all in your setup. Do you think it would work in a /4 with a rain tray? I'm guessing with it being the right code and size to fit the battery tray, it would....

Also - maybe one of the original 914 HO Campaign battery covers would fit and cover up the graphics on the top?

[raynekat]

@raynekat - that's a really good find and while I think the graphics are a bit "much" I'll say that the white doesn't look bad at all in your setup. Do you think it would work in a /4 with a rain tray? I'm guessing with it being the right code and size to fit the battery tray, it would....

Also - maybe one of the original 914 HO Campaign battery covers would fit and cover up the graphics on the top?

I agree that the white looks fine in my car. Actually the XS wild graphics go with my tartan seats to some degree. (IMG:style_emoticons/default/shades.gif)

Good idea about the battery cover.....just ordered one with the band to hold it on.

I think I may come up with a fun Bosch vinyl graphic for the side of the battery and it will finally look the part.

This battery is only 7.5 in tall, so it would likely still fit with a rain tray as well.
I have a lot of room between the top of the battery and the bottom of the engine lid.

This battery was incredibly easy to install....it fit that well.
Like it was designed for the 914.

[raynekat]

Here's what the battery looks like with one of the covers on it....
Helps to clean up the look a bit.
Got cover from AA and it fits perfect.
Wonder how long the rubber band will stay in one piece?