Adding regenerative braking to the Mirage

[Daox]

Haha, so it does. Perhaps I'll get around to it before winter.

[Daox]

Today it was rainy and dark out, so on went the headlights and some wiper use. The trip using those accessories over doubled the power usage. This does include regen as well.

I got the new gauge, but haven't installed it yet. I am very much looking forward to a gauge that works the way I would like it to.

[mpg_numbers_guy]

Do you have an idea how much of the 9.46 ah was regen and how much was consumption?

LED headlights will lower your power draw by quite a bit - 30w/pair vs 110w/pair = 6.67 amps saved.

[Daox]

Nope, no idea. Unfortunately, I can't differentiate at all with the current gauge. Once I get the new gauge on the battery, I will probably move the old gauge to the output of the alternator. This will allow me to see the power in/out of the battery total, and just the power out of the alternator. This should give me a very good idea of what is going on.

[Daox]

For whatever reason, the alternator delete circuit stopped working the other day. I am guessing it's probably a bad solder joint since it's acting like it an open circuit and charging at 15V. The thing has just been flopping around in my center console for weeks now.

So today's commute was done with the alternator on. I put the fuse back in place of my circuit. It was abnormally light traffic so I was able to push the mileage pretty high. 65 mpg was the result. My guess is if I had the delete working that it would be nearly 70 mpg though.

[Daox]

Alright, update time. I checked the circuit this past weekend. I found no problems. So, I tried the circuit again and it seems to be working perfectly again... I have no idea why it acted up again.

So, I have been using it all this week and it's been great. Last night for example, I got home from work and plugged in. My wife and I had a meeting to go to and left about 30 minutes later. The charger was already done charging. That's a nice indication.

This meeting was about a 35 minute drive there and 35 minutes back. The entire trip we had the heat going and headlights on. This was pulling about 20-25A from the battery. The battery is about 80Ah, and it was around freezing temperatures. As we kept going, I made sure to use regen as much as I could to keep it as charged as possible. The voltage started out at about 12.2V and slowly dropped until it was roughly 11.1V when we got home.

What I really found interesting was how regeneration acted as the battery became more and more discharged. Usually, on my trip to work I engage the alternator and it jumps to 60A or so and quickly tapers off to some lower number. Last night on the way home as soon as I would engage the alternator it would peg at ~80A and stay there. As the trip went on, I noticed it would jump to 80A, but the max voltage was lower and lower. Towards the end of the trip I was only a little over 13V while still charging at 80A. This makes sense of course, but it is a new observation for me.

So it seems that on my daily commute I don't use enough battery capacity to get the battery out of the constant voltage mode of charging and into the constant current mode. Unfortunately this limits the power I can get out of the regen setup. On the plus side, my battery is definitely large enough and lasts longer than I thought it would, especially in the cold.

[Ecky]

Thanks for the update! I keep an eye on this thread, since I now have an alternator too. It's been some years since I had one.

[Daox]

I have a quick update on this mod. I need to update my circuit so it stops charging at 15V. This fall I noticed decreased cranking power now that its been colder out. I investigated and noticed the water level in the battery was low. I think I put in just over 1 quart of water into it to top the battery off! Apparently 15V at 80-90A charging causes some water loss haha. The stock operation of the voltage regulator is to charge at a max of about 14.5V and once the battery is closer to full it drops down to 14V. Doing this shouldn't reduce the usefulness of the regenerative braking too much. It just won't charge it quite as aggressively when its more fully charged.