Alternator delete consequences

[EcoCivic]

Originally Posted by redpoint5

Lol, and I'm the opposite; an optimist expecting best case scenario. That's why I'm usually late to things, and sometimes run out of fuel. I could probably stand to be a bit more pessimistic and be pleasantly surprised when things go better than anticipated.

LOL. I wouldn’t say that I’m a pessimist, but I like to know that something will still continue to function even under the worst case scenario that I could be in. For that reason, I go overkill on a lot of things! But my logic is just because a situation is unlikely doesn’t mean that it’s impossible, and therefore the possibility can’t be ignored. Yeah a smaller battery pack would probably work fine under normal conditions, but I’m not willing to take that risk.

[teoman]

I can measure the torque consumed by the accessories, engine drag and engine output on my car.

I can put a graph up soon. This data was collected to measure engine drag in relation to oil and coolant temps.

[EcoCivic]

Originally Posted by teoman

I can measure the torque consumed by the accessories, engine drag and engine output on my car.

I can put a graph up soon. This data was collected to measure engine drag in relation to oil and coolant temps.

That’s cool, thank you! I can measure the amp draw of each accessory with my amp clamp too

[redpoint5]

I've got a cheapo inline meter I like to use to more precisely measure accessory draw. It's $15 on Amazon. I put Anderson Powerpole connectors on like this image.



Of course, you have to take measurements with the engine off because it won't measure alternator output. That makes the measurements less reliable because 12v accessory draw will be lower than the 13.3v or so that alternators like to stay at.

[Ecky]

Amazon has some nice DC clamp meters for ~$30. Probably not accurate at very low currents but no splicing needed.

My "alternator" is in the back of my car so I can measure all draw pretty easily.

[redpoint5]

Does measuring alternator output reliably tell you accessory draw? I used battery draw only since I know it's reliable and will only output what is being consumed. With an alternator, you don't know if it's feeding the battery, or supplying a load.

I suppose if you take a baseline measurement with the car running, you can subtract it from whatever the reading is when an accessory is turned on. Still unsure of accuracy since alternators can vary output depending on the load it senses and bump up voltages.

I've got a decent DC clamp meter that goes up to 400A that I use to measure starter draw.

[teoman]

I am able to read the value directly from the ECU of the car.

[Ecky]

Originally Posted by redpoint5

Does measuring alternator output reliably tell you accessory draw? I used battery draw only since I know it's reliable and will only output what is being consumed. With an alternator, you don't know if it's feeding the battery, or supplying a load.

I suppose if you take a baseline measurement with the car running, you can subtract it from whatever the reading is when an accessory is turned on. Still unsure of accuracy since alternators can vary output depending on the load it senses and bump up voltages.

I've got a decent DC clamp meter that goes up to 400A that I use to measure starter draw.

Mine is wired:

"Alternator* -> Battery/capacitors -> Car

So, I just clamp between the battery and car on the positive and I have an accurate reading. You're right in that in most vehicles, the alternator isn't a great place to measure instantaneous current, but the average should still be correct.

[EcoCivic]

Originally Posted by redpoint5

Does measuring alternator output reliably tell you accessory draw? I used battery draw only since I know it's reliable and will only output what is being consumed. With an alternator, you don't know if it's feeding the battery, or supplying a load.

I suppose if you take a baseline measurement with the car running, you can subtract it from whatever the reading is when an accessory is turned on. Still unsure of accuracy since alternators can vary output depending on the load it senses and bump up voltages.

I've got a decent DC clamp meter that goes up to 400A that I use to measure starter draw.

I would say it would be accurate, presuming the amp meter is accurate of coarse. A healthy, fully charged battery will draw almost no current, usually well under 1 amp.

But if you want the most accurate measurement possible, I would suggest fully charging the battery either by running the engine or using an external charger, check the amp draw of the battery with the engine running by clamping the meter around one of the battery cables, allow the amp draw to stabilize, and then subtract the small amount of current the battery is drawing from the measurement.

In my opinion, that would be a better way of checking the draw of accessories because they will be running on their normal voltage. Resistive loads such as incandescent lighting and heating elements will draw more current the higher the voltage, while capacitive loads (like computers and some LED light bulbs) will actually draw more currant when provided a lower voltage because they are designed to maintain a specific output.

[oldtamiyaphile]

Originally Posted by redpoint5

Of course, you have to take measurements with the engine off because it won't measure alternator output. That makes the measurements less reliable because 12v accessory draw will be lower than the 13.3v or so that alternators like to stay at.

Just add a PSU or battery charger that holds at 13.8v.