Stupid alternator

[spyro]

Sorry for the title, but you guys don't know how I hate this device right now!

I have a K5 GSXR600 engine and I'm finishing this year's car's wiring with the final step: install the alternator.

Last year this was pretty easy:

1. Connect the regulator to the alternator (3 phase cables)

2. Connect regulator's ground cable to engine ground

3. Connect regulator's positive cable to the battery +


This year is giving me lots of issues: the engine is not the same so we checked the alternator and looked like it was burnt, so we changed it. Then we connected the regulator just as the last year's car and the ouput was just 0,7V.

We tried with another two regulators and they all do the same. Moreover they heat up pretty fast, so It seems they're working.

We tried testing the phases with a multimeter and they all give 65V at idle and 21,2A. So that looks good.

A guy suggested that perhaps the regulator needed two ground points: one for the ground cable and another for the metalic case of the regulator, so we tried putting a cable that would connect the case with the engine ground and nothing happened.

Surprisingly (not only with this guy's suggestion; it happens with and without this auxiliary ground) when we try to start the engine up, the regulator's output will give 10-12V, but once the engine is in idle, it will give 0,7V again.

Any ideas before I make myself a hat with these three regulators and show it on every FSAE event? Thank you!

[MileyCyrus]

Hi Spyro,

How are you measuring the voltage? Have you viewed the battery voltage as the car is running, via your ECU or across the battery terminals? I'm pretty sure most regulators/rectifiers need a load/voltage source to reference, so they can know the voltage of the battery and regulate there output to roughly 14.5V and then dump the excess power into the heatsink. I think this would explain why it is getting hot quick, and possibly why on startup, when not much power or voltage is being produced, so it doesn't bother regulating and you see the 12V.

Cheers,

[BillCobb]

Didn't you read the book "Race Car Vehicle Alternators" ? Perhaps another vote for a "I really don't know what I'm doing" candidate.

Stick with snowmobiles. You don't need a Master's degree to fix one. Brad was right .....

[spyro]

Hi Spyro,

How are you measuring the voltage? Have you viewed the battery voltage as the car is running, via your ECU or across the battery terminals? I'm pretty sure most regulators/rectifiers need a load/voltage source to reference, so they can know the voltage of the battery and regulate there output to roughly 14.5V and then dump the excess power into the heatsink. I think this would explain why it is getting hot quick, and possibly why on startup, when not much power or voltage is being produced, so it doesn't bother regulating and you see the 12V.

Cheers,

Hi Miley. Even the regulator's plus cable is connected to the battery +, both ECU and tester are agree that the voltage between + and - is just the battery output. It tells 12,6V (Pb battery) and It should tell 14,5-14,8, right?

[spyro]

Didn't you read the book "Race Car Vehicle Alternators" ? Perhaps another vote for a "I really don't know what I'm doing" candidate.

Stick with snowmobiles. You don't need a Master's degree to fix one. Brad was right .....

If I knew what I'm doing I wouldn't come here to ask for help, mate. If you're suggesting to do what Miley says, I inform you I actually did it and it didn't work.

Thank you for your reply anyways.

[spyro]

Oh and Miley, in last year's car the regulator would start working immediately after starting the engine. Perhaps this is not the same regulator model? I'll check it right now.

[jd74914]

Hi Miley. Even the regulator's plus cable is connected to the battery +, both ECU and tester are agree that the voltage between + and - is just the battery output. It tells 12,6V (Pb battery) and It should tell 14,5-14,8, right?

Is that what the manual says? Ours has always just worked (except once for a shorted stator), so I've never actually measured battery voltage while running.

Do you have a manual to look in to make sure it is wired per factory? I've never seen a K5 rectifier; we run a K1-K3 which only has connections from the stator and positive/negative leads to the battery. It's a very straightforward hookup. Are all of the connections ok (ie: crimped well, etc.)?

I don't understand how you are getting 0.7V? Are you measuring with the rectifier floating (no load) at idle? You definitely don't want to put energy into it without a load or I'm pretty sure you will fry it since it'll have to send everything to heat.

Just FYI: It's actually a stator with rectifier. Alternators have built in diodes for the AC/DC conversion and then a voltage regulator while stators natively output an AC waveform which is rectified.

[spyro]

Is that what the manual says? Ours has always just worked (except once for a shorted stator), so I've never actually measured battery voltage while running.

Do you have a manual to look in to make sure it is wired per factory? I've never seen a K5 rectifier; we run a K1-K3 which only has connections from the stator and positive/negative leads to the battery. It's a very straightforward hookup. Are all of the connections ok (ie: crimped well, etc.)?

I don't understand how you are getting 0.7V? Are you measuring with the rectifier floating (no load) at idle? You definitely don't want to put energy into it without a load or I'm pretty sure you will fry it since it'll have to send everything to heat.

Just FYI: It's actually a stator with rectifier. Alternators have built in diodes for the AC/DC conversion and then a voltage regulator while stators natively output an AC waveform which is rectified.

First thank you for your help.

What we did first was connect all the wiring schematic just as the manual says:

http://i.imgur.com/cZGEX02.png

But the voltage between + and ground was just the battery's, not what the manual says:

http://i.imgur.com/oXrU0qn.png

We tried with 2 more regulators and it happened the same. So we measured voltage and current at the 3 phases to look for discordances, but they all give normal values (65V AC & 21.2A AC).

We then discovered that while the starter motor is running it will give 10-12V from the positive cable of the regulator (of course, without load, just floating) but will go to 0,7V when the engine starts.

[MileyCyrus]

Hi spyro,

Is 12.6 the nominal voltage for lead? From a couple years back I think I remember out lead one at around 12.3. (Side not: have you looked into LiFePO4? They weigh substancially less and are designed as a direct replacement for lead, and ours ha proved pretty much indestructible and doesn't need any fancy looking after like LiPo).

I'd also say to check the connections/crimps. I remember our dyno one used to float around that voltage and never any more due to it's connections.

Also, if you have an current meter, it might be interesting to see whats going to the battery from the reg when it's connected and running.

Cheers,

[Charles Kaneb]

12.6 V is about 3/4 charged for a lead-acid battery - FIRST robots use a 6-cell lead-acid battery as their main power source and max charge is usually obtained by going up to 13.2 or so.

Have you connected a load as shown in this circuit? Some modern car alternators don't run unless there's a current draw above a certain threshold. Try connecting your radiator fan and see if anything changes.

[spyro]

Seems like its working now, not sure why because it's wired just as I firstly said.

It's not giving 14.5V, it's giving around 13 at 5000rpm so it still needs to be checked out.

Thank you all for your help. I'll make the regulator-hat anyways.

[BeunMan]

...
Side not: have you looked into LiFePO4? They weigh substancially less and are designed as a direct replacement for lead, and ours ha proved pretty much indestructible and doesn't need any fancy looking after like LiPo).

...

Yes and No. The voltage is ~13.6v for a 4 series pack which is somewhat higher than lead-acid. They seem indestructable but combining differentiating charging (between 12-15V, unknown amp during racing conditions) still kills them though slower than any other Li(Po/Ion/Fe/S) and without the nasty hydrogen buildup and explosion afterwards. The safest bet is to allow them to drain anyway: Keep your power budget around what the alternator can provide and have the batterypack as additional supply and starter supply. Then charge them with a good balancing charger. You can easily calculate the required battery size and recharge cycles.

If you use them to start your engine you can do this, a typical 4 pack can deliver over 100A peak, but if you start it with partialy drained batteries and get them to overdrain under 12v they break down. Balanced charging might recover them but never like they were before.


On the original post:
0.7v Line-to-Line looks like the differential between two out-of-balance AC signals of ~65V normally in sync (e.g. one leading the other by a very small margin). Would be a wierd setup.

If it is ground to 12v+ voltage it might indicate the device has a complicated charging circuit designed to stop charging the battery in case it is full and periodicly switches it on. The 0.7v being the voltage over the IC when shut down (high impedance). Never seen any of those on any engine alternator though. Highly unlikely.