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]

Superhawk....again some great comments and insights.

The Antigravity Rs-30 has 1200 cranking amps and weighs 11.5 lbs (one of important reasons I chose this battery....possibly the wrong one).

The Optima 34R has less at 800 cranking amps and weighs in a whopping 37.9 lbs. Obviously this is necessary (the added weight) to get the higher amp-hr rating.

Actually, after the current (or voltage) drops low enough in the Antigravity battery, it turns itself off saving enough power to do 2-3 restarts. Supposedly you'll never get stranded. ??? When I was driving around at night with all the lighting on and the wipers going, my little LED gauge plugged into the cigarette outlet was dropping down to 10V. That got my attention as well as the lights dimming quite a bit while idling at the stoplight.

Sounds to me, a larger amp-hr battery may be in my future.
You are likely right that this would be a great battery for a race car.
It's very lightweight and starts the car.

Wonder if this Antigravity will fit in my Vespa??? (IMG:style_emoticons/default/idea.gif)

[Superhawk996]

Superhawk....again some great comments and insights.

The Optima 34R has less at 800 cranking amps and weighs in a whopping 37.9 lbs. Obviously this is necessary (the added weight) to get the higher amp-hr rating.

Actually, after the current (or voltage) drops low enough in the Antigravity battery, it turns itself off saving enough power to do 2-3 restarts. Supposedly you'll never get stranded. ???

Yup, to steal from my previous post: Li-ion batteries are good at providing lots of instant energy (i.e. cold crank amps) but are not so great at providing high power over long periods of time.

The restart / shut off below a voltage limit is the battery managment system. What we don't know is if the BMS is throttling back the maximum current draw allowed as the battery state of charge drops with your loads applied. Sounds like it is, if you're getting down to 10 volts! Would be really interesting to put a current clamp on it and monitor how much current is being delivered as time goes on.

What I don't have a good answer for is what the voltage regulator will do in response to a Li-ion BMS system and it's interactions. At 10 volts It should be applying full field to the alternator trying to generate more current. The problem is the BMS might also be limiting current into the battery if the BMS is sensing that the internal Li-ion battery cell temperatures are too high either from too much charge rate or too much discharge due to load. I honestly don't know on that one.

Out of curiosity are you using an LED to light the gauge generator light? If you are using an LED for generator lamp lighting, do you have a resistor in that generator lamp circuit to allow the alternator to begin fielding current initially at start up?

FYI - not sure what your budget is but you could pick up a cheap AC/DC current clamp with sometthing on the order of a 60A range and tell what is going on for sure if you don't already have one.