Lotus Elan

Alternator trip voltage?

PostPost by: Grizzly » Mon Aug 01, 2016 4:12 pm

Hi all.

Just a quick question......

I fitted a Lucas ACR17 to my +2 a few years ago and it trips at 12.6v (my battery with the engine off sits more or less exactly 12v) and i've always had slow indicators (the indicators also do an odd thing the Tell tail blinks once then stops blinking when i have a few things on at once) and headlights that are less than ideal.

Skipping on.......

I fitted a Alternator in a Dynamo case to my 2 seater which trips at 14v (the battery sits at 12.6v with the engine off) Indicators work perfectly, head lights are ok and it generally runs much better.

So before i go fitting the same dynamo/alternator to my +2 as long as i have the correct amp cable between the Alt and battery am i ok running it at 14v? i know nearly every modern car runs at 14v but not sure its wise with my +2 being on it's original wiring loom? or is it simply the amps i need to watch?

I have to admit i love the way my 2 seater runs and i'd really like to do the same to my +2 but i'd rather it didn't come at the cost of the thing bursting into flames.
Chris
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PostPost by: john.p.clegg » Mon Aug 01, 2016 4:46 pm

When you say "trips" do you mean the output of the alternator is 14v ? Most of them are ( give or take 0.5v )

In which case a lot of your worries will disappear...

John :wink:
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PostPost by: Grizzly » Mon Aug 01, 2016 5:55 pm

Yes the voltage the Regulator hold the power at 12 or 14v, so if i take a reading at the back of the 2 seater Alt it's putting out 14v and 45amps as opposed to my other car that runs at 12v 25 amps (not sure the amp rating of the stock dynamo but i know the black box limits the voltage to 12v)

I know most new cars run at 14v but i was just worried i'd start popping the old 12v rated components and putting too much power down 40 year old wires. but the more i think about it 2v isn't that much i guess it's only if i put 120amps through a 40 amp rated loom i may have a bit of an issue.

The thing that made me a little nervous about it was the Lucas ACR i have on my +2 was designed to run at 12v only and i couldn't get my head round why when my car runs so well on 14v? I thought there may have been a reason for it.
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PostPost by: elansprint » Mon Aug 01, 2016 6:12 pm

The voltage regulator on an alternator will cut off when the voltage reaches 14.5V this will ensure battery reaches full charge if other car only reaches 12V this will not be fully charged
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PostPost by: Grizzly » Mon Aug 01, 2016 6:30 pm

That may explain allot........ Guess my +2 Alternator is faulty.
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PostPost by: Orsom Weels » Tue Aug 02, 2016 7:46 am

Ian is quite correct, a 17ACR, & most alternators designed for a 12 volt system, should regulate to circa 14.5 volts & this should not damage any of your wiring or components. A healthy battery should show a good 12.5 volts after being fully charged & then left standing for an hour or so, 13 - 13.5 volts immediately after a run/charge. Batteries for starting are designed to deliver a big punch for a short time, & then be recharged quickly, so require a higher charge voltage to ensure they are fully topped up, also they don't like being deeply discharged & recharged on a regular basis, this will shorten their life, unlike leisure type batteries, as found on caravans/camper vans etc, which are designed to deliver a lower current for a much longer time, but can't tolerate high charge rates, so need to be recharged gently at much closer to their design voltage for a longer period. They can also tolerate being completely discharged & recharged on a regular basis without harm.
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PostPost by: gjz30075 » Tue Aug 02, 2016 9:12 am

Grizzly wrote:
I fitted a Alternator in a Dynamo case


I really want to know more about this! Start a new thread or PM me.
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PostPost by: Grizzly » Tue Aug 02, 2016 10:09 am

Orsom Weels, When i read the spec sheet for the ACR Alt it said 12v @ 6000rpm output. The Spec sheet for the Dynamo-Alternator said 14v @ 6000rpm hence the confusion (as that was what i was getting)

Thats why when i checked them i thought both where working as designed. Since then i've found another spec sheet for the ACR that says 12v @ 6000rpm with a note saying Charging Voltage 14 just below.

http://vintage.mitchell1.com/PClubData/ ... 733026.pdf
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PostPost by: rgh0 » Tue Aug 02, 2016 10:35 am

The Lucas specification is for the current output at 6000 rpm and 12 volts. At lower current loads the voltage will rise to a maximum of 14V as the battery is charged

cheers
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PostPost by: Orsom Weels » Tue Aug 02, 2016 5:34 pm

Grizzly wrote:Orsom Weels, When i read the spec sheet for the ACR Alt it said 12v @ 6000rpm output. The Spec sheet for the Dynamo-Alternator said 14v @ 6000rpm hence the confusion (as that was what i was getting)

Thats why when i checked them i thought both where working as designed. Since then i've found another spec sheet for the ACR that says 12v @ 6000rpm with a note saying Charging Voltage 14 just below.



Rohan has pretty much answered that anomaly, there will also be slight differences in how different companies collect & print their data. The example you've linked is basically giving you the charging amperages at a given RPM, & remember this will be alternator rpm, NOT engine RPM, for the different models, with the 12 volt on the end merely meaning it's for a 12 volt system, as opposed to a 24 volt system for example, hence the qualification underneath giving the charging voltage. Does your +2 have the volt meter or the ammeter ? If a volt meter, you should see a thick line at 13 volts, which is about where your battery voltage should be under normal conditions, consistently lower than that & it's receiving insufficient charge or the battery has seen better days, consistently higher & it is being overcharged, which will eventually boil away the electrolyte & kill the battery.
Bottom line is, if you're not showing around 13 volts at the battery with the engine running at anything over tick-over, something is not quite as it should be. ACR pattern alternators can be had for not a lot of money, but the quality varies widely. In my humble opinion, it's worth paying a little extra & buying from a reputable source who will offer some back up if you have problems.
I'm guessing your alternator in a dynamo case is one of the Stealth 'Dynamators' ?
http://accuspark.co.uk/dynamator.htm?gc ... GwodbCAFbg
If so, I've fitted one or two of these now, it's a nice way to convert to alternator whilst retaining an original look, & at 45 amps they have enough output to cope with almost any classic cars demands, even after we've added electric fans, high output lights, electric headlight lift etc. So far I have had no problems with them, although I know they had a few teething troubles early days. They also offer a significant weight saving over a dynamo, so Colin would have embraced them in his quest to "add lightness" :D
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PostPost by: Grizzly » Wed Aug 03, 2016 1:30 pm

Yes the Alternator i have is similar to the Stealth Dynamators (just two or three times the price, but i got a deal through work) http://www.powerlite-units.com/about-dynalites/

I think as you say the spec sheets are just set out differently and when compared are a little misleading.

Ahh well, i have another dynalite on order so that should fix the low power issues. :wink:
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PostPost by: Andy8421 » Wed Aug 03, 2016 2:03 pm

Alternators don't 'trip'. As long as the load is within its current rating and the rotor is at an adequate speed, an alternator will act as a voltage source - the output is held at a constant voltage irrespective of load.

In the case of a 17ACR, its hot (output voltage is temperature sensitive) output voltage is between 13.8V and 14V at the output terminals. A lead acid battery floats at 13.6V, so under no load conditions, the battery will receive a small net charge.

As the load increases on the system (lights switched on for example) the alternator will produce more current to keep the output terminals at 13.8V.

With the engine at around 2000RPM, under no load with a charged battery, the voltage across the battery terminals should be between 13.6V and 14V. Outside this range would indicate a fault with the battery, wiring or alternator.

For those interested:

http://www.lotus-europa.com/manuals/mis ... /17acr.pdf
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PostPost by: Grizzly » Wed Aug 03, 2016 3:07 pm

I was trying to say the Regulators target Voltage but thought it may get confused. Basically what Voltage does the Alternator Regulate as i was seeing 12v at any rpm on my ACR and 14ish volts on my dynalite, but it's been established now my ACR is faulty.

I just got confused with how the Lucas data sheet i got with the Alt new didn't have the line beneath saying @14v so it just said 12v @6000rpm and my dynalite data sheet said [email protected] which is what i was getting hence the confusion.
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