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.

[raynekat]

Lots of great info there Superhawk.

I have one of those new fangled Lithium batteries from Anti-Gravity.



They are pretty high tech and super light weight, but are not designed for cars with large loads.
I don't believe an early 914 utilizing mostly LED lighting (headlights, turn signals, brake lights), no AC, no heated seats would draw that much current.

But maybe with all the lights on and the wipers going, I'm starting to get a pretty good load on the battery?
What are your thoughts on that?

With the key off the battery shows about 13.2 volts.

I was thinking about testing the battery's load capability with one of these load testers.



It's entirely possible that this battery will not work for me unfortunately and I'll have to go with a more "conventional" style battery.....

[Superhawk996]

Lots of great info there Superhawk.

I have one of those new fangled Lithium batteries from Anti-Gravity.



They are pretty high tech and super light weight, but are not designed for cars with large loads.
I don't believe an early 914 utilizing mostly LED lighting (headlights, turn signals, brake lights), no AC, no heated seats would draw that much current.

But maybe with all the lights on and the wipers going, I'm starting to get a pretty good load on the battery?
What are your thoughts on that?

Dangerous territory. (IMG:style_emoticons/default/happy11.gif) I'm sure to create a debate with this one.

Li-ion batteries haven't made prime time in OEM automotive circles for a lot of reasons.

Here's a couple quick facts:
Antigravity RS-30 is listed as a 30 amp-hour battery.
An Optima 34R is listed as a 50 amp-hour battery.
A group 42 Lead Acid battery would typically be 50-70 Amp hours.

A 30 amp-hour battery is a rating that IMPLIES that it would have the ability to deliver 30 amps for 1 hour or 1 amp for 30 hours. However, batteries don't work that way in practice. A 30 Amp hour battery cannot deliver 30 amps for 1 hour. It's output will fall off drastically as it discharges and the voltage potential of each internal cell declines. There are also issues with the internal battery chemistry occuring when it is discharced too fast or too long. Especially so with Li-ion.

So as a starting point your chosen RS-30 Li-ion battery is at a disadvantage with respect to it's ability to deliver lots of current over time. Your chosen Li-ion only has about 3/5 (60%) the power capacity (i.e. current draw over time) of the Optima AGM and let's just round to maybe 1/2 the power capacity of a Group 42 Pb-Acid wet cell battery. I don't know what your actual load is with your updated LED lighting. It can be measured with a simple current clamp. You are correct that the lighting probably isn't a huge load but also know that LED' ligting can be deceiving - the total draw is less than conventional lighting of the same light ouput but you're still probably drawing 5-8 amps total between headlamps and tail lamps. @Spoke may have more info on what LED total draw is for headlamps, taillamps, and Instrument lighting.

The wiper motor on the other hand is going to draw significant power. More so if the bearings & linkage bushings are worn and creating more motor drag. Again, a current clamp would let you measure the load of the wiper motor.

Li-ion batteries are not great at maintaing their power capacity over time. Especially if they are allwed to become deeply discharged.

You can try the load tester but Li-ion will be a bit deceiving. Li-ion batteries are good at providing lots of instant energy but are not so great at providing high power over long periods of time. Those simple load testers are "calibrated" for Pb-acid. So it may say that it is great when you instantly connect the Li-ion but if you leave it connected, it may drop off quite quickly. If you decide to use that load tester for an extended duration, I'd stay within eyeshot of the battery (with safety glasses on) and have have a fire extinguisher handy. Just as a precaution. Li-ion batteries deserve more respect than Pb-acid for sure. I use Li-ion them in RC cars high discharge & charge rates and I've definately had cells buldge which is the precursor to a thermal runaway. I store them in a vented metal ammo box . . . just in case.

Li-ion batteries are a completely different animal. They have their uses but I'm not sure I'd recommend one for a 914. For racing - definately yes to reduce weight. For a daily driver no, beause they can be fickle and I have no idea how well thier internal battery managment system (BMS) is doing at maintaining internal cell to cell balancing and you don't have any control over the power capacity drop off over charge cycles. In fact, I'm not sure how the BMS works in these batteries. It is conceivable that as current continues to be drawn out of this Li-ion battery, it may reduce the current just to protect itself. Honestly, I have no idea how the BMS in these aftermarket batties is set up. Maybe others with more knowledge on that could chime in.