recharging ~120V battery system on the fly

[Onidaren]

I am designing a modular hybrid tadpole and need to find some way to recharge a 120V phosphate battery pack while the vehicle is using it. The idea here is to avoid carrying around a massive battery bank by supplementing with one tiny, lightweight generator like this one: http://www.amazon.com/Earthquake-11613-Portable-Generator-Compliant/dp/B00FL89I2W/ref=zg_bs_5006643011_3 or this one: http://www.amazon.com/Yamaha-EF2000iS-4-Stroke-Generator-Compliant/dp/B002RWK9N2/ref=sr_1_1?s=lawn-garden&ie=UTF8&qid=1431706866&sr=1-1&keywords=yamaha+ef2000is and two lightweight solar panels like this one: http://www.amazon.com/dp/B00IK19VF6/ref=wl_it_dp_o_pC_nS_ttl?_encoding=UTF8&colid=JR9JJK1AEGXY&coliid=I2UP4V9T4SKY94&psc=1

Why 120V? To reduce losses due to resistance. Also because the generator puts out 120V, so the charging system will not require a voltage step up or down, just a rectifier/smoothing package.
Why fossil fuel? Because of energy density, flexibility of energy sources, and off the shelf cost. As it is, a small LiFe pack will cost a few thousand dollars and so a $300 generator becomes a mighty attractive addition. Motors do not chew up 20kW+ all the time unless your name is liveforphysics, John in Cr, farfle, or a few exceptional others. The battery exists to handle bursts of power for a handful of minutes, and then recharge with the generator and solar panels.

For those interested, here are the rough design specs:
Total Weight: ~180kg (400lbs) maximum, including the driver plus a backpack (no passengers)
Speed: ~65 mph (105 kmh) on a near-dead battery (meaning 29 cells in the battery pack, minimum)
Hill climb ability: 0-65 mph at 20 degrees (not quite tree-climbing but close)
Mid-monster motor or Hub Monster (no ventilation holes drilled in the case. I live on a dirt road)
Mid drive system a must
LiFe, used chevy volt battery cells or similar, OR 3x 36V 20ah ping battery in series (high kWh/$ ratio)
Don't care much about the controllers (the motor requires 2 of them) as long as they are sturdy and inexpensive for this application.
I care about cost, but I am not willing to buy something that will blow up or otherwise fail in short order.

By law, this will be considered a motorcycle and licensed as such. However, it is NOT a motorcycle. It is much closer to a car on three wheels, but I don't call it that either because most people think of four wheels when I say "car".
After many iterations of testing and revision, the finished vehicle will look like this, but smaller and electric with only one seat (the pictured vehicle is gas-only):

 

[Nobuo]

you will use the same controller with the generator and solar panels?
120V controllers are expensive, from $600.

I would forget about gasoline generator (althought the energy density of gas, those cheap generators are between 15% - 20% efficiently) and invert all in high quality solar panels, batteries and Hub motors with regen .

 

[dnmun]

maybe that would work if you had a 120V AC battery.

 

[Onidaren]

you will use the same controller with the generator and solar panels?
120V controllers are expensive, from $600.

I would forget about gasoline generator (althought the energy density of gas, those cheap generators are between 15% - 20% efficiently) and invert all in high quality solar panels, batteries and Hub motors with regen .

I would love an all-in-one 120V charge controller that handles solar and gas generator input at once, if it exists and is less expensive than the two components separately. I'm pretty well decided on the voltage- there's really no other way to make a vehicle that holds its own on the highway. As for the generator, I'm 100% certain I want one in spite of the low efficiency. Range and speed are both very important, and I can't have both without either a generator or a truckload of batteries, even with lipo. So I am balancing the two, and throwing in solar for good measure. I can't go full solar because of limited surface area, plus I will not depend solely on good weather for my fuel to get home. I want to clarify something: this will be licensed as a motorcycle and will not have pedals.

This is a long term project. I would rather spend time than money (though I'm not going to build a controller from scratch, like some have done!). I have plenty of other aspects of this to build and test while I look for a solid controller at a bargain price.

 

[teslanv]

Just go buy a cheap gas motorcycle. - You are totally missing the point of an LEV.

 

[John in CR]

Onidaren,

We need to get realistic about performance goals. 65mph on a low battery on the flats is something readily achievable. 65mph up steep grades is something else completely. A 20° slope is a 36% grade is crazy steep, and hauling 400lbs 65mph up it requires just over 26kw at the wheel. I was able to hit 50mph with my 400lb load on a road with a near continuous 20% grade, but the constant acceleration/deceleration due to the curves made for very high system stress. That's on a pristine asphalt road built to get big wind turbine parts to the top of the mountain. I can only imagine the conditions of a 36% grade road. eg The road up to Pikes Peak has only 12% grade up it's steepest sections of significant length. Have you been up any of the roads you're talking about in a vehicle going 65, and if so what kind of vehicle?

MidMonster isn't close to being up to the task of 65mph up long steep climbs without non-existent 200V controllers. HubMonster might be, with high enough voltage, and long enough straights, but it will definitely require good cooling mods (simply drilling holes doesn't count). Don't worry about the dirt roads...A simple housing with a basic screen and filter will do the trick, and at the power levels you're talking about you'll need to suck air through the battery bay to keep it cool anyway.

That little generator won't come close to keeping up, so why bother with the noise. It might be ok for charging while camping, but again why bother with the noise if you're planning portable solar anyway.

Let's back up and get a good handle on your energy and power needs. What about distances? With mountainous terrain use google maps and apps that can really lay it out for you. You have to build for greater than peak requirements for a durable system.

One last note is regarding hills and top speeds. Just like your car can't go the same speed up hills as it can on flat highway, it's even more true for electrics. Our motors can't make the torque required for hills at the high rpms of max speed on the flats. 65mph up a very steep hill, not counting the crazy steep climb you mentioned, will require a system capable of well over 100mph on flat road, probably 110-120mph. Climbs are no joke, and the names you mentioned don't do what you're talking about.

Don't be dismissive regarding controllers, because once you get above 10kw for meaningful periods of time, controller selection narrows considerably.

I don't mean to knock the wind out of your sails, I'm just a voice of reason, so you're not disappointed in the results.

John

 

[Onidaren]

We are straying from the question which is the entire point of this topic: has anyone tried charging a 30s+ battery pack with a generator and succeeded, rather than dismissing it as a stupid idea? Toyota, Chevy, and others have all done it for full-size cars and made money in the process! I am simply trying to do the same on a smaller scale, for a one-seat vehicle.

I understand, though, that the battery and charging system cannot be separated from the other important parts of the vehicle's power system - it all has to work together. So now I will attempt to answer John's questions.

I'm serious about the hill angle. I have measured it. I live on it. However, most of those steep parts are short (say, 300 meters give or take). Right now I drive a honda CRV 4x4 and it handles the hill but I've never gone 65 on it - that would be too dangerous in my case. Though I never go that fast, I am purposely designing for more than I would normally throw at it. Perhaps we can accept a more realistic speed expectation such as 50mph? I HAVE gone that fast a few times, but only in the best driving conditions

the key phrase here is "short steep hills" as opposed to "long steep hills."

The small generator isn't supposed to supply all the power at once. I can pick one of similar size and weight but more output, if you think that is a good idea. As for noise, I don't mind. I am not building a shrine to mother nature here - I am building an electric hybrid vehicle for fun, and for the challenge.

I am trying to stay below 10kw and 120V for a number of reasons, the first of which is cost. If I can't get the performance I want out of 10kW and maybe 20kw peak, I will have to settle for lower performance at first and then upgrade. That is ok with me; like I said, I will be/have been patient and work with this over years until it does what I want.

I am not trying to make a motorcycle. Also, I need to reiterate that solar power is unreliable and so it has to be backed up by something more so.

 

[dnmun]

i still think the 120V AC battery is the biggest problem with charging directly from that generator.

but the cost of the generator and several solar panels and stuff to carry it and make it work add up to about $1k already. add another $1k for the bike, and then another $2k for the motor and battery, if you can find an AC battery that cheap.

suddenly you have $4k invested in a noise maker that has less performance than just a regular ebike with a $3k DC battery of about 10kWh capacity.

 

[amberwolf]

I don't know that anyone here has done the direct charging of a 120V pack from a generator output, but there are several ways you can do it..

The thing is, no matter what voltage you use, you still have to do a conversion and regulation and current limiting, etc., out of that generator and into the pack. So you still have to use what amounts to a standard charger system that can handle the current at which you need to charge it.

The simplest way to do that is to use an actual standard charger, running off the 120VAC from teh generator, with it's output connected to the pack. There's a number of "brands" of such chargers, some of them programmable and some of them orderable with a charging profile of your choosing. Some have been for sale on the ES marketplace, used, and we've even been spammed by various vendors of them. I don't recall any names at the moment, but you may be able to find old threads in the online market area for some of them.



Anyway: Presumably that charging has to be capable of doing it as fast or faster than you use it up, so you don't have to stop and wait for it to recharge. So the charger has to be capable of actually running the vehicle completely by itself, in that case.

If you don't need to actually charge as fast as you use it, and don't mind sitting around waiting however long it takes to get to the charge level you need, then you only need a charger capable of that level of performance.


If you don't want to use a standard charger, and if you are sure the generator's output will be very constant, you could just rectify it's AC output and use inductors and capacitors to smooth any variatiosn or spikes out, then use that filtered DC to direclty charge the pack.

It'd still need a current limiter, but you could use a brushed motor controller for that, one capable of the full voltage you'd need, and set it's current limit up so that it can't go any higher than the max charge current of your pack. Set it's throttle to whatever gets you the average voltage output necessary to charge your pack. Then just use more inductors and capacitors on the "motor" connector of the controller, whcih is where you'd hook up the battery charge connector. The generator's filtered output would go to the input of the controller.

I've never tested this idea, but there's no reason I can see for it not to work.

I am not trying to make a motorcycle.

Then you've got us confused.

It's tough to know what exactly it is or what exactly you need in order to do what you want, after the above statement plus the ones quoted below from previous posts, because a motorcycle is really what you are describing:

For those interested, here are the rough design specs:
Total Weight: ~180kg (400lbs) maximum, including the driver plus a backpack (no passengers)
Speed: ~65 mph (105 kmh) on a near-dead battery (meaning 29 cells in the battery pack, minimum)
Hill climb ability: 0-65 mph at 20 degrees (not quite tree-climbing but close)

I want to clarify something: this will be licensed as a motorcycle and will not have pedals.

 

[Punx0r]

If you kick the arse out of that generator it might get you 25mph continuous.

I think you may have missed Dnmun's point regarding an AC/DC compatibility issue...

 

[knighty]

google capacitance charger


then you just need a high voltage cut off

 

[dogman dan]

Not so bad an idea really, just lower the expectations of what you get out of a small generator.

That generator puts out AC. And there is a bit of wattage disparity. There is a reason a prius that goes 65 mph doesn't run on a 40cc engine.

It's 120v of AC, not DC so you will have to suffer some losses to convert to DC. No way around that.

120v AC at 800w max is the output of that generator. I have an 800w generator, and I assure you it won't like 800w continuous. So figure on more like 600w. It does have a 12v output plug, but it only puts out 48 watts of DC. That's for jumping a car battery.

So you have about 5 amps of AC, This is not enough to even run a skill saw, let alone do much to keep a vehicle going 65 mph. But, It will eventually, after losses converting to DC, charge your battery. EVENTUALLY, the key word. That generator would handle running an 8 amp, 72v charger.

In terms of wattage, 600w might get your 400 pound vehicle to 20 mph, so you can definitely limp home on it when the battery is empty. Nothing wrong with that idea. Some recharge as you go is better than nada, if you would otherwise be stranded. But I'd rather not have to run it all the time. Better perhaps to have it for use only when absolutely needed.

Only 58 decibels to run it, so noise isn't much of an issue. Especially if you are going over 30 mph, wind in your ears will be louder then. 4 stroke, so not so stinky as the tiny 2 stroke generators.

This small generator would be just about perfectly matched with a satiator. But that would be a 48v charge. For somebody touring where there are no plugs, an 800w generator an a satiator set to 600w of pull would allow just about infinite cruise at 20 mph.

For your setup, you will need two 60v chargers that can be connected to the pack at the same time (isolated), and presumably two 60v BMS. I'm assuming two 60v will be easier and cheaper to find than one 120v. Set each charger to about 250w, so the AC in draw on each will be only about 300w of AC. So when you run them, the generator will pull at 600w continuous. You could use an AC wattmeter to dial in your chargers wattage output to just exactly 300w ac input.

 

[Onidaren]

I understand the differences between AC and DC. I want the option of rectifying and smoothing the AC output myself eventually for a direct connection to the battery. At first, I want to use a battery charger. What I was unsure about is whether a charger will freak out if I am draining the batteries at the same time as the charger is running. I'm also looking for any other options I might not have thought of already. So basically you guys have answered my question.

The solar panels will put out an amp at best if we step them up from 12V to 120V, so I am considering using the panels to charge a 12V pack to power things like headlights and electronics.

Onidaren wrote:
I am not trying to make a motorcycle.

Then you've got us confused.

I have posted a picture of something similar to what I have designed, plus an explanation. This should clear things up some.

I want to reiterate that if the 800w generator isn't up to the task, I will get a more powerful one that fits in the same space, more or less.

 

[teslanv]

I find that sometimes one needs to step back from the problem and reassess...

 

[amberwolf]

I have posted a picture of something similar to what I have designed, plus an explanation. This should clear things up some.

I want to reiterate that if the 800w generator isn't up to the task, I will get a more powerful one that fits in the same space, more or less.

That picture and explanation makes things a whole lot clearer.

However...by the nature of it's operation (not legality cuz that's all just really paper silliness), it really is a 3-wheeled motorcycle in it's power requirements, weight, usage, etc., more than it is a tiny car. So there's no reason to say you're not building a motorcycle--that just confuses the issue for those helping you.

I understand your desire not to label it something you may not want to, but sometimes you have to use a term that doesn't say what you feel in order to get across most of the details of what you're describing, when what you want doesn't exist yet.


Anyway: Whatever generator you use, unless you are willing to sit at the side of the road for potentially hours (all at once, or a few minutes here, a few there) waiting for it to recharge your pack enough to get you where you want at the speeds you want, is going to have to be capable of completely operating the whole vehicle on it's own, without the battery pack there at all.

The reason is that if it can't, it also can't recharge the pack as fast as you use up the power, and you will end up sitting there waiting for it to charge, a lot.

A generator that *reliably* does what you want may be a lot larger than you want to use.


An 800w generator, even if it could produce 800w continuously, is not going to run a vehicle of the weight and acceleration performance and speeds for traffic/etc. It might operate it at 20MPH average, with traffic stops and starts and whatnot eating up the power with accelerations.




Keep in mind that I have a bike (and a trike, and a trailer) myself that are for cargo and hauiling St Bernards around, that with any load or dog in there plus me easily weighs more than your proposed vehicle. it's not as aero as yours could be made to be, becuase it's higehr off the ground, etc., so you could get some power loss back by going velo on yours.

It takes about 500W on average to keep up 18-20MPH, not including any power for accelerations. Because it's a bicycle-class vehicle, and in AZ thsoe aren't allowed more than 20MPH, I don't know what it would consume for sure constantly to do the 40-50MPH it would take to keep up with traffic on the roads, not counting acceleration power to get there fast enough to not get run over (which is about 5x-6x that power to get to 20MPH in about 4 seconds, beating some cars across to the opposite-side crosswalk before they outpace me past 20MPH).

But it would probably be a lot mroe than 800W. At a guess, based on what I've seen with 20MPH+ gusty headwinds on some trips, it would take about 1200-1500W, minimum, to maintain 40-50MPH. Not sure what it would take to quickly accelerate to those speeds, quick enough to not get run over by lead-foot drivers.



You can run the actual numbers in the various simulators around the web. Playing with the http://ebikes.ca/simulator is one good way, and it may show you other things you havent' thought about yet. Others are listed on the ES Wiki. http://endless-sphere.com/w



Anyway, I just want to be sure you understand the power requirements you'll need to satisfy, and size your generator and such according to those and your tolerance for waiting around for a charge.


Also, you might go over to EVAlbum site and look around at vehicles there; some of them show power usage info, etc, and will help you figure out what some of what you want to do will take, based on real-world experimentation and usage.

 

[999zip999]

This is more of a dream post. Or George jetson.

 

[Onidaren]

if it can't, it also can't recharge the pack as fast as you use up the power, and you will end up sitting there waiting for it to charge, a lot.

That's correct. I will need to size my battery pack according to the range and speed I expect to drive one-way, which is about 30 miles. That is the beauty of having a generator: you only need enough battery for half of a round trip, and the generator can pick up the rest. How much battery that is exactly will depend on which kind I am able to buy. A 2000W generator will get me closer to 35mph by itself which is much more acceptable in a pinch, so I think I'll go that route. Thanks for your input (and for all the other comments too), it has really helped as a sanity check for the project.

This is more of a dream post. Or George jetson.

it's no dream: http://www.arcimoto.com/development
http://can-am.brp.com/spyder/

 

[John in CR]

As much as I believe electrics and know they are the future, I would instead simply build an aerodynamic lightweight trike powered with leg power plus as quiet and appropriately sized ICE as possible for a way over 100mpg vehicle.

My suggestion at first would be to learn and appreciate the risks of RC Lipo. Build your trike as electric only with plenty of battery space, but buy just enough RC Lipo to get good performance for a shorter distance. That will be an economical start and help you gain an understanding of the energy requirements of what you ultimately want. The only reason I say RC lipo is that they're the only batteries readily available for hobbyists to purchase that have sufficient power density to do what you want with a small economical pack. eg The little 4 cell hardcase pack many of us have used have 5ah of capacity and have a 20C rating. Which means a string of single packs in series can deliver 100A. They typically go on sale for about $25/ea. You probably want to get enough for 2 in parallel for reasonable testing without running them really low. 8 packs in series gets you to 118V nominal, so that's 16 packs, but buy a couple extra in case of a dud or two. That's $450 plus US shipping, and you'll need another $150 or so in supplies and charger(s), but it's a hell of a bargain way to get in.

That's not a worry-free super convenient pack that could be sold to the public, because you'd have to include human interaction as a human BMS, but it would be just shy of a 1.2kwh pack that weighs 19lbs plus the box you make for it. It would enable short runs at quite high power, but going easy and low gearing you could do a 30 mile run with an aero trike fairly easily as long as there's not to much climbing involved. A 1000watt bulk charger would fill it back up in about an hour. If you use a conservative top of charge voltage and keep the discharges less than 70 or 80% DOD, as well as watch and maintain balance, then you could do plenty of test runs and since that would be low wear and tear on the batteries you could easily sell them on the forum and recover most of your money before making a larger investment in batteries for the long-term.

 

[parabellum]

I understand the differences between AC and DC. I want the option of rectifying and smoothing the AC output myself eventually for a direct connection to the battery. At first, I want to use a battery charger. What I was unsure about is whether a charger will freak out if I am draining the batteries at the same time as the charger is running. I'm also looking for any other options I might not have thought of already. So basically you guys have answered my question.

The solar panels will put out an amp at best if we step them up from 12V to 120V, so I am considering using the panels to charge a 12V pack to power things like headlights and electronics.

Onidaren wrote:
I am not trying to make a motorcycle.

Then you've got us confused.

I have posted a picture of something similar to what I have designed, plus an explanation. This should clear things up some.

I want to reiterate that if the 800w generator isn't up to the task, I will get a more powerful one that fits in the same space, more or less.

I believe you can skip the idea of rectifying and smoothing or capacitive charging right away, before falling in to illusions. Have tried both on honda i1000, it switches right off even at 100w detecting this crappy PF. It may work on brut force gens.

 

[cj7hawk]

To the OP - I've been developing a small generator for bicycles - current weight is under 10 pounds, maximum DC output is 1000w and currently it's built for 24v, but could be modified easily to 36 or 48v without physical changes... It's pretty efficient - I'm getting around 180 mpg economy with it, so I'm pretty much destroying most realistic bicycle economy standards for petrol based systems at the moment - mind you - that's combined electric/petrol economy - I only get about 150 mpg petrol only.

It's quiet and small, and can directly charge batteries at 24v, while maintaining high output to stop battery voltage dropping - I've almost finished the third prototype so it can auto-start and it's been maintaining up to 400w continuous for my application.

The system meets all EPA and CE requirements, is four stroke and relatively quiet. It also meets safety standards for small petrol engines...

If you're developing and want to chat about it, PM me - I don't mind sharing technology

It's also possibly worth mentioning that it costs less to make with COTS parts ( and 3D printed parts ) than a decent battery too !

Great stuff you're doing - I was fortunate not to read forums before I invented it, so I didn't know it was impossible until I actually solved all the problems with that kind of technology - Mind you, I wanted something small enough and light enough to fit on a normal bicycle on an unsupported ( fixed to the seat post only ) rear rack, so I did set myself quite a challenge. You'll find details of it elsewhere on these forums -

Thread is here: http://endless-sphere.com/forums/viewtopic.php?f=3&t=68164

Regards
David

 

[dogman dan]

For many of us, it's just more practical to carry enough battery to do a 30 mile run at 40 wh/mi use rates or less.

Onidaren, he wants to run at a higher rate, so he'll need a bigger generator. In my experience, chargers, or RC charger power supplies run fine on commercial generators. There is nothing funny about the AC output of them.

Only the excessive weight of many generators is the deterrent, along with some noise. Good small gennies are pretty quiet. My big cheap one is a loud mo fo.

10 pound, quiet generator able to put out 500w of 48v continuously, YES PLEASE. Hell, even if it really needs to run all day at 350w, that would work for me real good with one of my 300w chargers.