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Old 04-07-2021, 12:34 PM   #1 (permalink)
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Another Altenator thread-smart charging using tilt sensor

I am thinking of a idea to control battery charging with an incinometer ( tilt sensor).

Idea is to only allow the altenator to charge the battery when car is going down hill or braking. It could be adjusted to a certain grade.

This is what I want-

Going down hill- charging
Using brakes - charging

Going uphill- not charging
Going on level land-not charging
Sitting at redlight- not charging

Voltage drops below 12.4- charging

I think I can do this with an ardunio and a tilt sensor, along with a relay to cut the field current on the altenator.

I don't want to use the brake light switch to trigger charging because then it would charge while waiting at red light, I would rather it only charge when there is energy going to waste.

I believe I might get a warning light on the dash when it's not charging, but that might not be a bug, but a feature. It will allow me to see when it's charging or not.

My question is do Tilt sensors sense tilt when the car is breaking?



Only fault I see is car would charge while at a redlight and facing down hill.

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Old 04-07-2021, 12:50 PM   #2 (permalink)
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Nice idea!

An inclinometer should be able to detect loss of forward momentum and/or slope.

Of course, just because you're pointed downhill doesn't mean you've got free energy to spare. Most hills around here aren't steep enough to even maintain speed. Your alternator will spend half of the time on since half of the time you're tilted upwards, and half downwards.

Perhaps you could have a threshold at which it engages, representing either a hill steep enough, or engine deceleration great enough that it's worthwhile to engage the alternator.
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Old 04-07-2021, 01:54 PM   #3 (permalink)
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My thought is I will adjust the angle of the sensor to match the grade I want it to be active.

I found this sensor which uses a metal ball. I'm sure it will activate under hard breaking-
https://www.sparkfun.com/products/10289

but I fear the ball may vibrate on and off the switch.
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Old 04-07-2021, 01:56 PM   #4 (permalink)
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I would also periodically fully charge my battery to prevent sulfation
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Old 04-07-2021, 02:01 PM   #5 (permalink)
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Just had an idea! I could program the ardunio to only charge the first 15-20 seconds the brake light is on. It would be rare for one to brake for a longer time than that.

This would allow me set the tilt sensor more aggresivally to only charge on steeper hills, but still allow charging even with mild braking.

I would also allow me to use an solid state tilt sensor

Last edited by Vwbeamer; 04-07-2021 at 02:10 PM.. Reason: add more info
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Old 04-07-2021, 02:19 PM   #6 (permalink)
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Very interesting idea. I've had the idea of using a microswitch on the accelerator to turn it on when the accelerator is not being depressed. But I liked your idea since that would turn it on only when decelerating, so not at idle.

Except it could turn on if stopped on a downhill incline. But that's not necessarily something that's going to happen often, depressing on where you live and drive.

The only other idea would be to have the alternator turn off when there's no speed from a speed sensor.

Of course if you add a start-stop system then charging at idle, even stopped on a downhill grade, wouldn't be a problem
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Old 04-07-2021, 02:30 PM   #7 (permalink)
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Accelerator switch is a better idea, except the stopped/idle problem.

You want the alternator to come on during coasting too, not just braking, so even slight deceleration should trigger the alternator to come on.

You'd ruin a battery quickly on any highway travel where you're spending more than 10 minutes without going downhill or braking.
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Old 04-07-2021, 02:46 PM   #8 (permalink)
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Seems like a good idea.

I'd assume it would register deceleration the same as a downward slope. You know what assumptions are worth, though.

Not sure why you wouldn't want it charging at a light. Yes, it would use a bit more gas...but at that point, 100% of your gas is going to waste. At least you'd be getting a bit of something back for it. Killing the engine would kill the alternator - and everything else - from wasting gas. Coasting with the engine on would amount to the same thing.

You could get creative and use the throttle position sensor as part of the information the Arduino is looking at. Could take it farther and figure out how to make the alternator pout out lower voltage (12.6-13) when at a light or engine-on coasting, go full ham when braking.

Personally don't see "regen braking" worth the effort with a regular alternator and a 12v lead battery...they just don't accept a quick, high-current charge easily. The right kind of lithium might. Bigger lead would accept a charge faster, but then you're carrying more weight.

YMMV.
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Old 04-07-2021, 04:02 PM   #9 (permalink)
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Quote:
My question is do Tilt sensors sense tilt when the car is breaking?
en.wikipedia.org/wiki/Inclinometer#Factors_which_influence_the_use_of_in clinometers
Quote:
Factors which influence the use of inclinometers
(Overall accuracy varies depending on the type of tilt sensor (or inclinometer) and technology used)

Gravity
Temperature (drift), zero offset, linearity, vibration, shock, cross-axis sensitivity, acceleration/deceleration.
A clear line of sight between the user and the measured point is needed.
A well defined object is required to obtain the maximum precision.
The angle measurement precision and accuracy is limited to slightly better than one arcsec.
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Old 04-07-2021, 06:08 PM   #10 (permalink)
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Quote:
Originally Posted by Stubby79 View Post
Seems like a good idea.

I'd assume it would register deceleration the same as a downward slope. You know what assumptions are worth, though.

Not sure why you wouldn't want it charging at a light. Yes, it would use a bit more gas...but at that point, 100% of your gas is going to waste. At least you'd be getting a bit of something back for it. Killing the engine would kill the alternator - and everything else - from wasting gas. Coasting with the engine on would amount to the same thing.

You could get creative and use the throttle position sensor as part of the information the Arduino is looking at. Could take it farther and figure out how to make the alternator pout out lower voltage (12.6-13) when at a light or engine-on coasting, go full ham when braking.

Personally don't see "regen braking" worth the effort with a regular alternator and a 12v lead battery...they just don't accept a quick, high-current charge easily. The right kind of lithium might. Bigger lead would accept a charge faster, but then you're carrying more weight.

YMMV.
Thanks for your input. you got me thinking.

I think there will be a pay off for smart charging. The purpose of letting the battery go down to 12.4 is because at the lower voltage it can accept more current. I would consider a lithium battery after the lead acid battery dies. A .3-.7 mpg gain would be worth the sub $60 cost to me. Truthfully, at current gas prices few mods make financial sense. There is also the benefit of reduced pollution from saving a few gallons.

I agree lithium offers more benefits, at a greater cost.

My main reason for not charging at lights is most cars made in last thirty years automatically control the throttle to handle loads at idle and a alternator charging a heavily discharged battery would be a noticeable load and burn more fuel.

But now you have made it really simple if don't mind charging at red lights. just hook a relay to brake switch to cut the field current except when braking. edit- or the accelerator switch idea.

That would be super simple. add in the tilt sensor in parallel with the brake light switch( diode to keep tilt sensor from turning on brake lights) so when one or both is activated, the relay gets power to energize the field windings.

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