Great Experiment!
Great Experiment as always!
I wonder if you could hook up a switch that's tied into the alternator's draw to switch the load on and off... For example, on decel with engine on, you could flip the heavy-duty switch to begin charging (kinda like TangoJetta's fuse, but with a switch). This may extend battery life. RH77 |
Another thing to consider is the injector response is changed slightly when the battery voltage is reduced - think about it - it gets a pulse of a certain voltage which may be the full battery voltage through the ECU. Lower that voltage and the valve may open a little slower and end up leaning the air/fuel mixture - anyone ever trim the supply voltage to extend the mixture range? If anything it could affect performance at higher RPM.
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This likely would mean you are stopped at the lights idling or rolling down a hill. Alternatively it could be switched by a vacuum switch. Of course keeping an eye on an ammeter and voltmeter gauge set would be handy just to make sure your not leaving the battery discharged. |
Brock -
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Rated Power (Wp) = 10 Max Power Point VMPP (V) = 16.5 Max Power Point IMPP (A) = 0.6 Short Circuit Current ISC (V) = 0.8 Length/Widht = 21" x 17" The max Amp of 0.6 may be too wimpy, yes? If no, then would a smaller Deltran charger be more appropriate? Or maybe skip the charger alltogether and attach the solar panel directly to the car via some simple cicuitry, yes? Thanks, CarloSW2 |
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Lead acid batteries die most often from water loss from overcharging , being left disharged or undercharged for long periods of time and to a lesser extent overheating from external sources. If a switchable ALT was employed and the battery returned to full before switching the engine off (or charging of AC at home up to full) then I really doubt any significant life reduction of a battery. In fact , it may even extend the life if the car is always overcharging it. I think it would need some experimentation to bust or umm ,unbust? this one , unfortunately the results would take years to obtain and even then , there are many variables that can affect battery life even in normal service. |
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The now charging ALT will also give a braking effect as well. This could save on brake pad/disc wear + with the FE savings from effectively no ALT it must come out on top against the possible life reduction of the battery. i think its worth a try |
What poo-poo's that idea is that ime normally coasting in N by the time I touch the brake pedal. :)
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Besides, what about those massive losses to belt friction and the pulley fan while the alt isn't being used? So wasteful... :D |
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OT - Silveredwings: You sold the BMW too? Did I miss a thread? Are you bicycling everywhere now?
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Jangeo Deltran actually makes a 5.5 and 20 amp version as well but once you get up to about 20 amps I would suggest the Iota line with a smart controller, they are cheaper for charging amp.
Gregg you are correct, maybe I wasn't clear. Overcharging a battery is bad for it. When I say a fully charged battery I am assuming a safe good full regulated charge, definitely not over charging the battery. Also deep discharges in particular a complete discharges will and do damage a lead acid battery. The longest life, or most watts out of a battery will be obtained by cycling the battery to abut 70% charged or sucking about 30% of the power out and then fully correctly charging it again. And yes most car alternators do a poor job of correctly charging a battery and often over charge the battery thus shortening its life. |
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I'm getting 32 - 37 depending on traffic but I'm still getting used to the clutch and its short gearing. I need to learn how to fix the entries in my GS garage... |
You should definitely start a new thread. Let's hear the whole messy story. (While Matt's updating the garage code - note: looks like he didn't understand part of your post in the link you provided above.)
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Aparantly true , this car had the same battery and it lasted 40 or so years before finnaly giving up. Amazing. |
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More news from eCycle - they have been testing the next generation of controller with the regen voltage regulation/limiting and have been pushing 400+ amps from 48 volts (4 group 29 batteries) and the results look great. They will probably push the unit to 600 amps peak and 400 continuous (20kw!!) that you can hold in one hand!!! |
JanGeo you are the regulator ;) I have a similar setup myself. I just prefer to recommend an automated 3 or 4 stage charger to people who don't understand proper charging or don’t have the time to watch it themselves.
And ya the Deltran chargers are a lot for what they are, but for someone like my brother who wants to connect it and walk away and then forget it for a week, Deltran is the way to go. I really like the Iota chargers in the larger amperages as well and they are more reasonably priced. Again you can build them yourself for a lot less if you know what you’re doing :) WOW, 20KW that is some serious power. Do you have a link to them? |
I do have the Deltran 12 volt 5.5amp unit for the Hawkers and it is pretty smart in that it holds 14.9 volts for 6 hours to top off the cells and balance them then drops to 13.5 to float them. Fortunately I have PowerChek modules on the 3 in series so one Deltran does all three at the same time taking a little bit longer to fully charge by like you say - set it and forget it. BUT the variac can put out 1200-1500 watts on 3 or 4 batteries - darn line cord gets hot!
Yeah 20kw is going to be great - just wish it wasn't $995. I think I will setup my scooter and push the motors that I have to 200 amps or more and see how they handle it - from what I have seen they start to moan and really pull when I start pumping in the amps. They are rated at 225 continuous if properly cooled but I only need a lot of amps for a few seconds to get to full speed. The new controllers are not on line yet so don't look for them. They are a join venture with another big company and eCycle has taken the driver section of the controller from Navitas and adapted a newly designed control logic with the proper sensing and limiting to plug into the driver board and made a great new product. More testing is being done with it and maybe a price break will occure later this year. The only thing left is some programming of the limits to make it easier to set - right now it requires resistor changing and some jumpers. I already Told Dan I was interested in one before the end of this year. |
Good link, clencher. You're the link man for sure.
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The thing I keep coming back to is only the 15% loss on the alternator. I find it really hard to believe that an alternator can turn 85% of the mechanical power in to electrical energy. Maybe they do, but it seems really high to me. Heck a switching inverter is lucky to be 90% efficient with no moving parts. And a DC motor attached to an AC motor is also only about 50% efficient. So how the heck can an alternator be more efficient then a motor inverter? I would think an alternator is about 50% efficient at the top end. Maybe I am all wet, but this just doesn’t sit right with me.
It also wouldn't explain the larger gains we are seeing by disabling them. 100w or less then 1/4 HP should mean a 10% increase in mileage HP wise. Maybe they are 85% efficient at 50% loading and only 25% efficient at 10% or normal loading? |
Numbers I get from eCycle is that the alternator is about 60% efficient but again at what load. They have a pretty free spinning rotor even when magnitized and slip ring brushes so not much loss there so you get into I2R losses at high currents and the diode drops all the time. It really comes down to how much current the car draws constantly . . . 20 amps at 14 volts is 280 watts doubled for 50% efficiency is still only 560 watts . . . add some belt and fan losses in the alternator and you get less than 1 HP. If you like I can run an alternator on an electric motor and tell you how many watts it takes - all I need is a belt and pulley for the motor.
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Sounds like way to much work but I would be curious to know what it really takes to drive the alt.
It's funny you mention that because one of my first thoughts was to drive the alternator in my car off a 1 hp DC motor from the spare battery. Seemed like an evil circle and I thought the losses would be less to go the inverter/charger route. It also allows me to very easily re-connect the alternator for trips or if my wife takes the car. |
Posting this message on behalf of John David Shelton, who is the founder/moderator of the MaxMPG Yahoo group: https://autos.groups.yahoo.com/group/maxmpg/
John David is currently serving in Iraq. He has limited bandwidth (thus the request to post this for him). EDIT: his personal web site: https://maxmpg.org/ Feel free to reply to his thoughts on alternators / charging (prompted by this thread and my write-up at metrompg.com). He periodically reads stuff here at GS. Quote:
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I'll take a stab at a couple of John David's points...
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You know I was just thinking if we knew the amount of watt hours that we would need to operate for a desired time how about using a higher voltage NiMh or NiCad pack and regulate it to 14 volts out - I have some cheep 20-60 volts input 15 volts out (adjustable) - switching regulator modules 80% efficient and since the NiMh battery can be cycled a lot more than an SLA that could supliment the cars 12 volt battery and you could run a 12 volt to high voltage charger to recharge when going down long hills or slowing down although that recharge time would be minimum - solar or grid recharge would be easy enough at higher voltage.
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Would a larger battery require more amps to recharge it if the ammount of discharge to start it is the same? |
Diesels vs. Gassers
Unfortunately, gassers need ignition/spark to operate, whereas a Diesel doesn't need a battery once running. This and the electrical systems such as power steering on newer cars would require quite the load.
If you know your maximum commuting distance, adjust it for temperature, and perform the calcs, I'm sure a zero-alternator/plug-in system could be implemented. The cost/weight is up to the experts... RH77 |
DRW there really isn't much of a penalty for a larger battery beside weight. Well a typical lead acid uses about 1% of its rated power a day to stay topped off. So you could say a typical 440CCA battery, about a 60AH battery uses about .6 amps a day. A battery twice the size would use 1.2 amps a day to stay topped off. Not much in the grand scheme of things, but something.
Rh77, while it’s true that diesels don’t need much power once warmed up they require a LOT to get up to temperature. Even in the middle of summer my car will run its coolant glow plugs (60 amps or about 800watts) until the coolant hits 120F. I believe it does this to warm the engine quicker to help with emissions. In winter the car will run the regular glow plugs (80 amps or just over 1000w) for about 10 seconds before cranking and about 20 seconds after cranking depending on the outside temp. The two sets of plugs never run at the same time though. |
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And yes, I was freezing cold most of the time in the Winter unless we drove a distance and kept it running all day. RH77 |
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I wonder how it compensates. I'd guess that probably injector performance gets sluggish as voltage drops, so it lengthens the pulses to ensure enough fuel gets in.
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I'm still tryign to figure out exactly what this does, but it clearly has something to do with voltage and injectors. |
On the Mitsu ECU it uses something called 'deadtime' to adjust injector pulsewidth as system volts varies. Deadtime is a set ammount of pulsewidth added to the calculated injector open time. In effect, injectors need a certain ammount of time to open/close, during which they don't flow the full ammount of fuel. If volts are low, the injector opens slower. Once open it doesn't matter what the volts are. The Mitsu ecu has a table of deadtime values that can be changed, and they often need to, since swapping to larger injectors of higher or lesser quality is common in the DSM world. The stock deadtime values follow a similar curve to what red91sit posted.
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Oh, one more thing. The Mitsu ECU stops trying to run the car at around 9 volts. There may be a similar cutoff point on other cars. YMMV :)
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Part of the reason for the mileage improvement is, of course, you took away the horsepower drain of the alternator. Sadly, the only thing is, you now are running solely on the battery(ies).
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The topic of generating electricity with thermocouples always seems to come up in the alternator-less threads.
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