inverter/converter

[ricel]

anybody out there tried to hook up a 12vdc inverter to 110vac to power up a 36vdc converter to directly hook-up to the ebike battery....sort of continuos 36vdc supply without draining the battery.
i have tried but would like to hear from anybody out there...

[OneEye]

As long as your inverter and DC voltage converter are rated for a sufficient Wattage, and you have a long enough extension cord, this should work.  I can perhaps see this as useful for testing purposes, but if you have the batteries anyway, why would you want to do so?

[ricel]

i think oneeye is missing my point. you don't need long extension wire. an inverter(12vdc to 110vac) is directly connected to converter(110vac then to output 36vdc). the point being is rather than put a series of 3 units of 12 volts to produced the desired 36vdc, we can just use a single 12vdc with an advantages of stable continuous 36vdc inputted to the motor avoiding draining the other 2 batteries thus savings!!! right. I would like to make a point also of 'law of conservation of energy i.e. electrical energy will produce the same amount of mechanical energy'....or increase electrical energy to produce the desired mechanical energy with reserved power......perpetual motion

[OneEye]

Duh!  You're right; I missed your point.  I was thinking 110 AC->12V DC->36V DC, when you clearly stated 12V DC->110 AC->36V DC.

I see a lot of losses with the two step conversion.  Probably 20% loss, although the specific inverter and AC/DC converter will determine the actual losses.  It might be more efficient to go with a straight DC/DC converter (although can you buck 12V to 36V directly?).  Even with a direct DC/DC conversion I don't see the need.  The energy density of your batteries is going to be the same whether you go with one large 12V battery or 3 smaller 12V batteries.  Is there a cost differential?  Enough to justify the losses and the converting hardware?  For a given range you will need just as much weight in batteries (perhaps more) if you create a 12V->36V conversion than if you change the cell configuration to get 36V directly from the series of cells.  The only way to change that is to change battery chemistries to a more power/energy dense technology, such as the Lithium based chemistries.

One area where I could see going with a 12V ->  36V conversion is if you had a fuel cell system with the right power output (say 200W) but at 12V.  It might be better to make the voltage conversion than it would to triple up on the fuel cell stacks.

Forget fuel cells too, they aren't ready.  Let's go with zero point energy.  That should solve our weight and range problems.

[myelectricbike]

  Ah!... How about this idea. Lightning power.    100,000v > (converter) > 36v. You would not even need any batteries except maybe between bolts of lightning.  You could like hold like a lightning rod over your head and only go for a ride when its lightning. If it was raining too you could also take with you a bar of soap and stop along the way to take a shower and to wash your ebike. 



  Disclaimer: Take this face literally. Holding a lightning rod over your head while it is lightning will most likely result in your becoming a big lump of charcoal. Either that or you and your ebike will set a new world speed record for lumps of charcoal and pieces of metal circumnavigating the globe. In other words this idea for powering your ebike is just a joke so don't do it in case you do not actually have a PhD.

 

[OneEye]

Sail power!  Although tacking into the wind while in traffic might be a bit edgy.

[ricel]

seems like nobody is interested. serious about my inverter/converter experiment....so thanks for your time and bye!!!

[OneEye]

Sorry, I wasn't trying to be dismissive, just talking through the idea and trying to add points to consider.  You were correct that I missed your point in my first reply, but I thought my second response was certainly on-topic (other than an off-hand reference to zero-point energy, but I thought it paralleled your comment on perpetual motion quite well). 

Would you care to elaborate on why using a multi step conversion process will give an advantage over a traditional 3 battery series?  The main point is you don't get something for nothing.  By drawing from a single 12V battery instead of a series of (3) 12V batteries, you will draw at least 3x the current from that single battery.  Most of the battery technologies currently in play actually prefer lower amp draws.  And as far as getting from point A to point B, the energy equation is still the same.  You may be leaving the other 2 batteries untouched, but now your battery will discharge in 1/3 the time.  As you mentioned, the "law of conservation of energy" is directly in play here.  My comment on possible uses in adapting fuel cells to e-bikes is on target.

I found a 12V to 36V DC/DC converter on the web.  It was rated at 750W peak (about the right target for us), but only 236W continuous.  That might make it acceptable to a fuel cell application.  The converter was a bit expensive (~$140).

Back to the basic point:  What are you trying to achieve with your conversion experiment?  Is this just a "can it be done" question for grins and giggles, or is there a system improvement objective?  An inverter to AC/DC adapter doesn't magically make energy appear, it simply converts it between one voltage/amperage set of factors to a different voltage/amperage set of factors.  The net energy (required to make the motor go) is still the same.

[myelectricbike]

There are people who have lived their whole lives trying to come up with a perpetual motion machine and some people honestly think its possible. My mailman for instance can't understand why I can't just put a generator on the back wheel to recharge the battery pack while I'm riding. I tried to explain about EMF and how a regenerative controller can tap any energy that is not being used to drive the motor and put it back in the battery and that using a regenerative controller cuts a third off my recharge time.

I explained that the same concept could be used with two BLDC PM motors and would reduce the amount of current that is required by a single motor but not the power necessary to either push the bike or that the bike could provide coming down a hill or from breaking.

Its sounds like two motors could produce more power but the problem is where the power is coming from since that does not change except slightly for the additional weight of the second motor which also requires more power to be applied.

You said it Mike... No free lunch available here except in the form of a regenerative controller.

[OneEye]

And the regenerative controller doesn't comprise a free lunch either.  It merely recaptures some of the gravitational potential energy you and the motor have put into a hill climb.  It would be interesting to note how much of the energy savings from the regenerative controller are coming from the regenerating function, and how much is simply due to the lower top end speed (thus lower wind drag).

[myelectricbike]

Don't forget about peddling at the top regenerative controller speed which is about 75% of the standard controller. As you peddle at top speed you first reduce the energy needed from the batteries and the controller will need to supply less and less until the point is reached where you are putting in enough energy that the controller stops drawing energy from the batteries and waits for you to work a little bit harder so it can start drawing energy from your peddling that it can use to charge the batteries back up. For me this is sweat mode and what I need to loose some extra pounds in addition to either my range being increased or less recharge time when I get home.

[mustangman]

Did someone forget the basic priciple of AMPS X VOLTS = WATTS OneEye and Myelectricbike are correct, There is never a "free" lunch when it comes to energy!!!

[ricel]

you guys, really blew my comments about 'perpetual motion' let's stop this as oblivously everyone believe there's no free lunch. let's talk about efficiency, my units is setup like this; 1) make sure your 36v battery is fully charged 2) I have a 12v motorcyle battery hookup to inverter then to converter/charger of my 36v battery system, thus my fully charged 36v battery is connected in parallel to this inverter/converter supply. in effect there are 2-36vdc power supply. the 12v battery will of course consumed watts with added weight on the bike. it seems to work, but have tried only on short term basis. I know you guys have logged longer mileage on your bikes, maybe that would be the realistic environment I need. that's why i'm asking if anybody did it.
thanks for your input oneye and myelectricbike - it really helps.

[OneEye]

OK, I think I see where you are coming from now.  You are augmenting your 3-pack (36V) battery with an extra battery through an inverter/power pack to provide a parallel 36V source.  Essentially bringing a 4th battery into the system to add its energy to the system's range.

I don't see a significant problem with this, although I imagine I would want to put a switch on the setup so when it is run down you can turn it off and disconnect it from the system.  Someone can step in and correct me if I'm wrong, but I think at the start (when all the batteries are fully charged) most of the power will be provided by the normal 3 battery pack.  As the 3 battery pack runs down, its voltage will sag below the voltage provided by the inverter/converter, so the 1 battery setup will start providing most of the power until it is run down.  When it reaches a point where it can no longer maintain 36V I would want to disconnect it so the 3-battery pack provides all the power. 

I don't see any major problems with the setup, other than the inefficiencies of the power conversion as noted before.  If you were to start from scratch a setup of 3 larger capacity batteries might provide a better solution.  Another option, which I have heard users on Endless Sphere advocate, is to set up a 48V/36V system.  When top speed and power is desired they use 4 batteries.  When a lower speed is desired, they simply flip the 4th battery off the system with a switch and run at 36V.

I'd be interested to hear from anyone else about how they think the power draws would be distributed among the different batteries in your setup.

[OneEye]

Just want to mention again that I haven't been trying to be dismissive.  I've been commenting based on my limited understanding of what you are trying to achieve.  Also, it's sometimes impossible to tell from a series of short posts whether you're dealing with a 6th grader or a PhD in Electrical Engineering on the other end of a forum conversation, so I was also trying to cover all the bases without being insulting.  Thanks for sticking with it and explaining a little more for us.

PS. please don't try to read an insult to your intelligence into the above; it really can be hard to tell the difference between someone who is so far advanced than you they cannot simplify into plain language for you to understand or someone who simply doesn't even grasp the basic concepts

There, have I covered all my bases yet (insert smiley that looks from left to right)

-Mike