Virtual alternator delete.

[oldtamiyaphile]

Denmark gets 1200-1600 hours, Australia gets double that.

We get roughly double the panel output that Denmark does.

Global Solar Atlas

I saw zero measurable gains from 100W on the petrol Kangoo, just as I saw no gain from 40W on my Mercedes.

This was all with roof mounted panels. Mounted inside your car a panel would be shaded most of the time -it only works for that small amount of time that you can drive with the panel facing the sun. 105Wh assumes the panel is angled towards the sun. On a vehicle the ideal angle is zero degrees. So more like 85Wh/day - assuming you only drive into the sun, and park facing the sun.

That's a tiny amount of energy - if you drove all day that's ~8w that you're getting, roughly the same effect as replacing your tail lights with LED. You haven't specified the size of your battery, but by the sounds of it, it's tiny. A 7.4Ah battery has no problem starting my cars. The point being it's not even a case where you can store a lot of power while parked for use later in the day.

My Trafic uses 3.8/100 at a steady 74km/h (lowest speed in top - A/C on 3-400kg on board). 360W gives me 0.2-0.3/100km. Adjusted for a behind glass 50W panel that would be 0.02l/100km - smaller than you can reasonably measure. Bare in mind that 360W of solar panels will never produce 360W of power when mounted on a car -about half the rated output is what you'll see.

If you look at my side bar, I've got all sorts of cars. The LiFe is in the Proton, a very simple car (MPEFI). The improved charge efficiency saw a solid 10% gain. If I connect a grid charger/ solar panel it just switches off immediately as the alt keeps the battery 98% full. Solar panels are pointless in this situation as there's no where for the current to go while parked, same goes for a really small capacity battery.

On the Trafic, with a 120Ah battery, stop start, all city driving and low RPM hypermiling, I found that the alt really couldn't keep up with demand - meaning stop/start didn't work. So now when I park, the power is stored in a large battery - which means stop start works 90+% of the time. The alternator sits at 11.7 volts with the engine running.

[Luno]

I think because people drive in different environments experiences are different. Typical city driving in Copenhagen it is very sedate except for the 4 lane city rings, usually only one lane with double lines, so nobody are pulling stunts. When I drive in Berlin or Hamburg, it is a constant show of horsepower going from stop light to stop light, or so it seems to me, though this might be considered by Germans to be light driving? Likewise driving in rush hour congestion mostly my milage would be in the low 20's mpg or worse, so when I manage 47mpg in the city, it is when traffic is spaced out enough for me to accelerate slowly and coasting from around 30 mph, with engine off when possible, timing the lights perfectly every second or third time. And you are backing me up on this; weight is extremely important when accelerating. Driving alone compared to with wife and 3 children, two of them adult requires an acceleration 3 times as slow to have the same numbers on the display and likewise I would need to coast sooner, from a lower speed to counteract the larger mass Luckily I lose coasting speed slower with a heavier car, so I will still make it to the next light, by I'll be 10 times as annoying to other drivers, so getting rid of 50 kg, is measurable at the pump. As said, I'll get back with exact numbers on the solar panel contribution and exact measurements of my cars amp draw in different conditions. Before,when I still had my failing lead acid battery I drove 706km on 28L gas with gets me 3.94L/100km highway, Which is quite good but not extraordinary for a car this size, just to point out that there is no magic here beside low rolling resistance, few parasitic loads and hard core hyper milling to get these numbers I in city driving where alternator load is a main fuel cost.

[oldtamiyaphile]

Well, if you're comparing to a failing Pb battery then anything is possible. I gained 16Mpg tank to tank swapping lead for lead in my FIAT.

[Magician]

I have a 13W panel and an 18 Watt panel hooked up to my 92 VX and keep the panels in my hatchback area. When I park at work, I park so the back of my hatch face the sun in the morning. I open the hatch during this time and position the panels so they are facing the sun optimally for the next 3-4 hours. It always charges my stock battery fully within a few hours. In the colder months, I put my alternator belt back on and turn my switches back on that interrupt the alternator circuit. This has been very effective and my mpg's instantly start climbing when the alternator is out of the picture. I haven't done A-B testing, but as I said, my mpg's very noticeably increase. Probably 8-10% gain.
My drive to work is about 7 miles. I have driven my car a long as 90 minutes, but that gets into the battery being at a voltage that I feel could start damaging it. I don't let it go below 12.2 volts. Most of the time it doesn't go below 12.4 volts and typically I stay above 12.6 volts. I do have LED lights all around including the headlights. In the not so often case that I drive for an hour or so and can't charge by sun later in the day, then I'll hook up my car charger. I rarely use the fan in the car, NO AC.. never has had that.. manual crank windows,,,very basic car. MPGuino is hooked up as well. I have that thing calibrated so well it's impressive. Solar works great for me.

[Stubby79]

Found this on my walk this morning. Thought of this thread...

[teoman]

Would auto start stop systems be effected negatively by this?

[ratgreen]

Great stuff, would love to see some pics, and maybe a diagram of how you have everything set up. Which BMS and caps etc you used. I've got hundreds of 18650s laying around. But I dont trust chinese BMS's and I dont want to float charge them. But you as saying that its ok because they are not going fully charged. Makes sense I guess. Keep it up I look forward to seeing results.

[teoman]

How do you stop the batteries from undercharging?

[redpoint5]

Originally Posted by teoman

How do you stop the batteries from undercharging?

He doesn't disable the alternator. It's "virtually" disabled from the fact that the battery is charged above ~14v. When the alternator detects voltages above this, it freewheels instead of generating power.

Once the battery drains below some threshold, the alternator detects this and supplies power, keeping the battery from further discharging.

I'm curious at what voltage threshold the alternator kicks in, as it matters from a battery health perspective. Too low, and there is risk of damaging the battery.

I bought a 5 Ah Li-ion battery so I can experiment with this. At $30, it's fairly cheap to play with to get a sense of how well this setup works. If it works very well, I might consider stepping up to a higher capacity.

[oldtamiyaphile]

I don't understand the mystery surrounding this mod. The alt holds the same voltage it always did ~14v.

Everything from the various Li battery threads applies.

Except if your flammable battery sets your car on fire, you may not get an insurance pay out.