Printable View
Anyone ever seen an alternator put out 15 volts?
(EDIT: sorry, probably should have said I see 15 volts on the recorded data.)
We ran the car about 80 miles the other day over several sessions, and voltage crept up from 13 to 15.1 over the course of the day, with the last five laps never under 14.9.
Now of course I can't replicate it in the shop to troubleshoot, shows the 'expected' 13.3v
Thoughts? thx
I've had a bad regulator do that on a tow vehicle--
cooked the battery, fried the points, blew every bulb that was on
thx, I immediately thought 'regulator' as well, especially as voltage plateaued and was dead constant 15.1v for five laps...Quote:
Originally Posted by Charlie Schmidt
but why then is it back to 'normal' 13.3 in the shop one day later ??? hmmm
I've seen those voltages routinely with a belt driven alternator on a F2000 at full rpm. Even the dynamo will record 14+ volts. AFAIK, the regulator changes the voltage from AC to DC, but don't quote me.
Thx Bob, but was has me a bit mystified is how the voltage ramped up almost uniformly from 12-13 to 15+ over the course of 40 laps in 3 sessions, yet now when in the shop is back to 13-ish..... :confused:Quote:
Originally Posted by Bob Wright
to illustrate, here's the rising voltage on the 3rd, 11th, 15th, and 20th laps of the day;
looks for all the world to me to be a failing V regulator, but why is it back to 'nomal' 13v the next day ???
Electronics have good and bad days, it could be the humidity could be the heat could have been a vibration it picked up. If you unplugged the connectors you might have cleared the resistance or reset the connector.Quote:
Originally Posted by Lotus7
thx, but the only difference between 15.1v at the track and 13v in the garage the next day was a 10 mile ride in the trailer. Could have been vibration, will look again for something loose.Quote:
Originally Posted by Pi_guy
It is a voltage regulator by definition. If voltage is too low than it can be something else (dynamo output), but if too high, it can only be the VR. I would question even the bad connection possibility, if voltage too high. Our regulators are undersized, are being overworked, and in an overheating condition in our application, which is why we are continually burning them up. I expect your varied output is heat related. Time to have another regulator ready to go. The question would be whether you want to benefit from the higher voltage until it stops working altogether. Presumably, the extra voltage has no penalty as the dynamo is working the same. The only penalty is that it will stop regulating at some point. If you check after each session, it would probably never ruin your day.
^ This...Quote:
Originally Posted by problemchild
Quote:
Originally Posted by Pi_guy
Voltage is directly proportional to resistant (V=IR) and resistance increases with temperature due to increased vibrations of the molecules inside the conductor. Therefore voltage increases as temperature increases.
voltage DROP increases over a fixed conductor length with temperature. Voltage output does not increase with temperature, at least not from a generator which is dominated by the magnetic field aspects.
It MAY increase the output of some battery chemistries.
The temperature sensitivity in a voltage regulator is likely due to a cracked component inside. As it heats up the parts move and you can get a wide variance of effects depending on the type of component that is broken and what technology that component uses to do its thing.
Diode is semiconductor device. And semi-conductor are negative temperature coefficient materials i.e. resistance decrease with increase in temperature or in other words current increases with increase in temperature.Quote:
Originally Posted by Rick Kirchner
Sure, but the device overall is temperature compensated. Go back and read your original. It makes no mention of diodes....flow within a semiconductor is different than within a conductor.
What are we talking about a regulator with four diodes and a few other components. I spent some time thinking about it sorry if I didn't present all my thoughts up front. Just trying to come up with explanation of voltage change. I will go paint my boat bottom.Quote:
Originally Posted by Rick Kirchner
The heat I am referring to has nothing to do with ambient. The VRs overheat in normal use and more so as they go bad. When you replace them after they fail, they are visually burn damaged. That may not qualify as "heat related" in engineer talk, but I expect most racers will understand the concept.
"ambient" is a relative term. You'd expect an alternator to be rated by the manufacturer for continuous operation at something over 200 deg F - that would be the heat load inside an engine compartment. Now the device itself produces heat in operation which they expect airflow to carry off, so go a bit over that, say 250. If its a standard part for a street car they're designed to go 100K mi on a car in the desert....Quote:
Originally Posted by problemchild
Voltage regulators are mostly series resistive devices - in other words, the excess current (not going to the field coil) is dumped into a resistor (or a semiconductor) which heats, and that heat is dumped into the body of the alternator. If the regulator is burn damaged then the alternator is producing way more voltage than expected (RPM too high) and the internal components can't handle the extra current, or the body is too hot to carry the heat away from the regulator - or both. I may have bungled this explanation to some degree, but there are good explanations here: http://www.billavista.com/tech/Artic...ble/index.html. and here:https://www.homemade-circuits.com/ca...lator-circuit/
I'd remove the regulator if possible and mount it someplace external on a heat sink with a scoop to cool air. If that's not possible, then a scoop to cool air for the whole thing. You may want to do that with the diode block as well.
Looking through classifieds I noticed that very few Zetecs carried the alternator on the gearbox as used to be common. If its suddenly fashionable to carry them up front on the motor I'd look at both high rpm and lack of adequate cooling - maybe some telltale strips on the device for starters.
That is also an issue with the Kubota dynamo regulator if it's revved too high. It will burn up its stand-alone regulator if it spends much time above 4200 dynamo RPM or in an excessively hot environment.
Link to post on that subject:
http://www.apexspeed.com/forums/show...7&postcount=29
One could infer from this that over-revving a standard alternator could do the same thing, so limiting its maximum RPM might eliminate the issue similar to what I did with the Kubota dynamo.
It would also eliminate generating unnecessary heat and thus save a tiny bit of HP.
As noted, the regulator shunts excess charge to heat.
There however is little need for the regulator/rectifier to be attached to the alternator. Simply moving the regulator to a place with better airflow can improve life. Combination regulator/rectifiers have become common, but in racing applications it may be better to separate the devices. I make a unit for vintage motorcycles that does exactly this.
Mine is on the side pod floor.
Carry a spare
https://www.primusracingparts.com/Tr...or_p_4681.html
Probably not significant, but...
Having the alternator/regulator generate excessive heat when it could be avoided is wasting HP.
Rather than post a separate thread, I thought I'd ask the question here since it seems the people who know are watching this post. Anyway, I'm thinking of not running an alternator, and just running off a lithium battery. Why? Because my alternator quit sometime last weekend and I essentially ran off the battery for 3 sessions, without charging it in-between. The battery drained to the point where the car wouldn't run during the last race on Sunday. I know I should have been looking at voltage between sessions, but we were dealing with other issues, like getting DQ'd then reinstated for running the wrong rain tires (another story). Anyway, if any of you have some advice about running without an alternator, good or bad, I'd like to hear it.
Daniel Swanbeck runs his total loss but he runs a very large Odyssey. I have the Kubota kit and still 'top up' between sessions.Quote:
Originally Posted by Lyngengr
Last year when I had a fuel pump go bad I was able to finish the session even when the power draw was massive. Without the alternator it was a certain DNF.
Right now, finishing races is more beneficial to me than the weight savings or increased power.
Are you running the axle driven one?
Are you sure it quit early on? If it quit in the session before the battery gave up, that's not an indicator that you can run w/o the alternator.Quote:
Originally Posted by Lyngengr
I run a kubota dyno and have a 1,450 AH Li battery. The battery will run the car most of a weekend without the dyno hooked up (ask me how I know) but when it runs out of power it will fail with no warning and generally hurt the battery. With the dyno working, I usually charge it once a weekend, but have found I don't really have to. The Zetec and MZR battery draw is primarily the electric fuel pump.
We ran 4 days last weekend. On the first day, 4th session, the car died coming into the pits, I scrolled over to the voltage readout on my AiM G-Dash and saw a voltage of around 7 or so. I was using a brand new Antigravity Lithium YTX12-24 battery. I put it on the Lithium charger that evening, went to dinner, and came back with the charger flashing red indicating a battery internal problem. So I replaced the battery with a fully charged Odyssey PC950 and assumed it was a battery problem. Ran that afternoon, twice the next day, and twice the following day, with the last session a race. Got 4 laps in and the car started to backfire and eventually wouldn't accelerate. I coasted into the pits and looked at the voltage again, it was 8 and the car won't run with less than 9. So now I'm suspecting the alternator. I had the same thing happen previously when the alternator quit with a broken stator wire. It will charge, but not fully.Quote:
Originally Posted by DaveW
Now I know I should have been looking at the voltage after every session but I just assumed it was a battery problem on the first day. However, assuming the battery wasn't the problem, but the alternator, I basically got 4 sessions, and almost 5, with the PC 950 and probably would have with the Antigravity as well. So this leads to my question - why not run with only the battery in a dead load situation, and charge it after each session? Getting rid of the alternator will save a few pounds at the rear of the car. I know other drivers who do this, and really have no issues, especially with a Lithium battery, which starts with a voltage above 13.
Interestingly, after getting the car back to the shop, I connected both batteries to the chargers and the Antigravity and PC 950 charged up just fine, neither one showing any issues. The Antigravity was sitting on a bench, I charged the PC950 in the car with a direct connection to it, not through the car's system. I pulled the alternator yesterday and spun it up on my workbench with a drill, connected to a voltmeter, and it did produce a voltage reading (less than 1 volt). I have a spare alternator and I did the same thing with it, getting basically the same voltage. I will take both to an alternator shop on Monday for a better assessment.
OK, I'm asking, how do you know the battery will run the car without the dyno. And when you say "runs out of power" do you mean the dyno quits?Quote:
Originally Posted by Bob Wright
Yes, the snowmobile version with internal regulator. The spare is the same thing.Quote:
Originally Posted by BeerBudgetRacing
I would suspect that part of the issue is that the charging needs of the lithium battery are not adequately met by an alternator designed to go to a lead-acid battery. The alternator is a charger, and you notice that lithiums usually have a dedicated charger to meet their specific needs in order to maximize life.
One thing to watch out for is having the alternator field active when the vehicle is just sitting with the ignition off and perhaps the master on. THAT will discharge a battery pretty quickly. Need to have the field ignition-switched.
Yes, a Zetec car will run a session or two with a faulty charging system. Considering all the problems I see on my cars, and others, with electrical issues, I have made maintaining the charging system a priority. Electronic components need 12 volts in a way that traditional systems on kent/pinto cars do not. If you are trying to operate reliably on 11.2 volts as opposed to 12.2 volts, it will be an uphill battle.
I recommend having a fully functional charging system AND putting a battery charger onto the battery after every session.
Even with a battery (DEKA ETX18L AGM) that will accept pretty much any type of charging system as long as it is functional, I do what you just recommended. That has so far (13 years and counting) been entirely trouble-free.Quote:
Originally Posted by problemchild