Virtual alternator delete.

[teoman]

Seems voltage can go up %10 from -10 degC to 50 degC.

Something to be aware of.

[Daox]

Yeah, you do loose a lot of capacity at lower temperatures. But, if you charge inside, and/or bring it into work it's not really going to be a big deal. If you leave it in the car... Well it's a bigger deal.

[teoman]

I was thinking more along the lines of charge at night, wait till morning, battery heats up and its voltage rises, caps go badaboom.

[redpoint5]

I plugged in my LiPo and immediately saw my interior lights get much brighter. ThenI heard the Pb battery start gassing due to overvoltage. The LiPo started at 16.68v. I disconnected the Pb battery and started the car. It was a little slow to start with 8ft of 10AWG wire connecting my glovebox battery, and voltage sagged to 7.6v at the lowest, with 160A peak cranking amps.

Voltage quickly settled at 14.3v and 8A draw (114W). The battery got up to 95 degrees. Sadly, I couldn't see any difference in fuel consumption between the first 5 minutes of running the car, and towards the end when the alternator was running. I showed 0.2gph at idle the whole time and 5.5HP.

I'll try again with the ultracap installed and see how it goes, along with a more precise inline meter to track energy use from the battery.

I'd have thought anything above 14v would have killed the alt, but maybe not.

[teoman]

Its the current draw that would kill the alternator.


I would imagine 5 minutes at 9V and the alt would be toast trying to push as many amps as it could to reach 14 volts.

[redpoint5]

Well voltage never went below 14.2v while the car was running and the battery had juice. It sagged to 7.6 during start, but that was for only 3 seconds. The alternator seemed to want to keep voltage at 14.1 at idle and no accessories running.

EDIT: I just charged my LiPo pack on the Lithium Ion mode and it stopped at 16.4v rather than 16.8v after putting in 4.4 Ah. Still a little bit of a stretch for my ultracap bank, but only 0.03v over the rated limit for each cap.

[Daox]

Very interesting! Thanks for testing.

The alternator on the Mirage stops charging at 14.4V according to my service manual. My alt delete circuit sends a false 15V signal to the alternator and it does kill it.

[redpoint5]

Maybe my 2-3C discharge rate is pulling the voltage too low to disable the alt, plus the fact that I've got 8' of 10AWG wire between the battery and power cables.

I'm going to see if I can keep the voltage above 14.5 and also put the Ultracap in as a buffer.

[teoman]

When disconnected if your batts jumped back up to 16V then that means that they could not keep up with demand.


Did you measure from the engine side or the battery side?

[redpoint5]

Min/max voltage was taken at engine end and includes the loss in the line to the battery. The settled voltage was taken from a cigarette lighter voltmeter and verified against my UG.

I'll get my clamp meter on the alternator output next time and have an energy meter connected to my battery.