66% or better

Sequential battery charging


I’m getting pretty interested in building an electric motorcycle, and I ran across this little hack to charge multiple batteries with one charger. It uses a 4020 counter that’s pulsed by my dear friend the 555 to activate a series of relay pairs to switch a single charger sequentially between battery cells. A more advanced version could use a microcontroller to monitor the state of each cell to ensure even charging. If you’re thinking of constructing an uber-ups, this could be useful.

Comments

  1. Dave says:

    yea your gettin me interested in building one too! when we gonna talk about the 36 volt dewalt batteries?

  2. Tom Parker says:

    looks good not sure what i’d use it for though :(

  3. trump says:

    I tried to do such a thing a year ago, let’s see if you can! $)

  4. SOI Sentinel says:

    Ack, where to begin. I’m curious why they didn’t use a standard 12V battery charger. A few in parallel would have allowed them to vary charge current in large blocks. I think once they try and tackle their own home made power supply for this they’ll find it a LOT easier to vary the power (via supply side SCR into an isolation transformer that feeds a high current bridge rectifier and filter cap). I don’t think he’d be interested in the alternative (PWM control from a line bridge rectifier – capacitor combination to a lower value DC capacitor… they call this a one quadrant DC drive at this size, not a buck or stepdown power supply). DC current is easy to measure by linear Hall effect sensors these days, as I wouldn’t want to think of the size of a shunt resistor required to get anything useful out of this.

    Oh, and a beefier electric motorcycle was done by an EET team for senior design at my alma mater, but I only found one reference article to it online…

    http://www.postcrescent.com/apps/pbcs.dll/article?AID=/20060829/APC04/608290567/1029

    Beefier body than the one posted previously, and other then the plan to switch to LION batteries, they’ve also designed the power electronics themselves. Nifty and ambitious.

  5. Pretty cool but I don’t see how it would be usefull in the long run to charge a whole pack. However, I can see that it might be usefull as a type of BMS (Battery management system).

  6. Alan says:

    I wonder if over time the batteries will develop problems from being charged separately. Even matched batteries from the same run will have slightly different charge and discharge characteristics. I would be curious if not charging them as a single series battery would have any negative side effects.

  7. Alexander says:

    The issue with all EV (Bikes, trikes, cars, trains, whatever) is that they still rely on dead dinos for the power. The power companies still burn them because they are cheap.

    Sure, your breaking free of ‘big oil’ but your still dependant on _someone_ for your ride to work.

    And the best part is, if everybody had a EV that they needed to charge every night… the power grid would collapse! Fantastic!

    EV are oool now, and don’t get me wrong–they are cheap to ‘fill up’–but you have to look into the future 15 years. And elecricity will rise up higher to compensate for everybody drawing more watts out of the grid.

    What we need is everybody to have solar cells on their houses. Every last one of them plug into the grid, and that will solve the issue once and for all. Use what you got, and we haven’t even begun to tap the power of the sun. not even close.

  8. trebuchet03 says:

    “The issue with all EV (Bikes, trikes, cars, trains, whatever) is that they still rely on dead dinos for the power. The power companies still burn them because they are cheap.”

    That’s 100% correct, and I agree with you for the most part. The turbines that the power companies use are far more efficient than the ICE that would have been in the vehicle. Yes, it is still burning fossil fuels. But, it is getting more power per pound and then being used at a higher efficiency.

    Meh, even nuclear (and now we’re going to have members going nuts on us) – its too bad the united states has fallen behind in that area. Hell, Canada – our neighbors to the north, have a better system (from production to management) than we do… We don’t need to be enriching all this uranium…

    While its not a solution, its a start. If it (any alternative) is to be accepted, these smaller steps need to make their way through. We could very well be in trouble in 15 years – but change can not happen in a snap (unfortunately).


    And I completely agree with your solar idea ;) Every year the cost per kW slowly goes down AND even really old panels are capable of producing. I can’t wait until solar road panels are developed. But if the masses are going to accept this while dino fuels are still around, the conveniences they have now can’t go away.


    Last thing… those big power plants don’t throttle back as expected. Yes, occasionally a turbine/boiler is taken offline for maintenance – but not because of daily load fluctuation. That is very expensive to do, very inefficient and can add extra wear (especially if go into wet steam area). In fact, its cheaper to discharge energy not used.

  9. max says:

    wow, this is very useful, i didnt know relays can be used to charge batteries…

  10. Alexander says:

    “That’s 100% correct, and I agree with you for the most part. The turbines that the power companies use are far more efficient than the ICE that would have been in the vehicle. Yes, it is still burning fossil fuels. But, it is getting more power per pound and then being used at a higher efficiency.”

    Yes. But we will be out of them in 2050. Unless we can figure out how to get it from the sand like they’ve been promising us for the last 20 years, we are going to be out of them. But even besides that, the emissions from them–the smog, the heavy metals, the chemicals needed to burn them–are what is really messing things up.

    “Meh, even nuclear (and now we’re going to have members going nuts on us) – its too bad the united states has fallen behind in that area. Hell, Canada – our neighbors to the north, have a better system (from production to management) than we do… We don’t need to be enriching all this uranium…”

    Send it out into space. Why not? Just send all the spent radiation at the sun. What is it going to do? Nothing. There is no reason we shouldn’t be launching our nuclear waste at the sun. We are going to spend far more than what it would cost to send it to the sun to keep it under a mountain for the next thousand years.

    “While its not a solution, its a start. If it (any alternative) is to be accepted, these smaller steps need to make their way through. We could very well be in trouble in 15 years – but change can not happen in a snap (unfortunately).”

    Yes. Because the people of this country have taken the easy route of letting the government run them instead of the people running the government.

    “And I completely agree with your solar idea ;) Every year the cost per kW slowly goes down AND even really old panels are capable of producing. I can’t wait until solar road panels are developed. But if the masses are going to accept this while dino fuels are still around, the conveniences they have now can’t go away.”

    The real issue is not getting solar panels efficient. Yes, it will help, but the problem of the efficiency will go away with numbers. What is the roof of your house doing? nothing. There’s hundreds of millions of square feet going to waste.

    This is what I’m talking about:

    http://www.premierpower.com/solar_energy_residential/roof_solar_tile.php

    If everybody had these, then every electric issue this country has would be eliminated.

    “Last thing… those big power plants don’t throttle back as expected. Yes, occasionally a turbine/boiler is taken offline for maintenance – but not because of daily load fluctuation. That is very expensive to do, very inefficient and can add extra wear (especially if go into wet steam area). In fact, its cheaper to discharge energy not used.”

    I realize that they just keep running them and shunt the load off into giant resistors. They keep the generators running at a constant speed, and they shunt off whatever current they don’t need. Why is California having rolling blackouts in the summer? Everybody has the AC on, and the grid can’t output enough. If they all had solar panels on their houses, nobody would have this issue.

  11. michael says:

    being new to this, i’m curious why you wouldn’t simply charge the batteries as a pack, instead of charging them individually. charging as a pack seems a lot easier but i might be missing something.

  12. trebuchet03 says:

    “Why is California having rolling blackouts in the summer?”

    Fair enough… and very good point ;)

    “Send it out into space. Why not? Just send all the spent radiation at the sun. What is it going to do?”

    Even that makes me (someone very supportive of nuclear) a bit nervous. I know the vessels the material would be in would survive a catastrophic failure. And I know vitrified waste isn’t going anywhere… I just have a bad feeling. The best alternative I’ve heard was to place the casks in a zone under the ocean with no earthquakes that moves under the crust and back to towards the Earth’s core. There was a few zones found to have these traits – sorry I’m sketchy on details, I read about this a long time ago :P

    “emissions from them–the smog, the heavy metals, the chemicals needed to burn them–are what is really messing things up”

    Hey, I’m all for that ;) I just don’t see it reasonable (especially for most americans) to accept the next alternative outright. That is, without some sort of viable transition. Honestly, I really loathe hybrid cars. The idea is great, but the cost considering the average amount of passengers in a car is something like 1.2 people is very high. Hybrid busses, that’s another story (average passengers in 2005 was about 29 persons).


    On the subject of efficiency. A friend of mine from poland had mentioned a system they have in his hometown. They have signs saying the speed you need to travel to get a green light at the next intersection. This means very little idle time. he was somewhat amazed that poland (not exactly a 1st world nation, but getting there) can accept this system. But here, going anything but 5+mph over the speed limit into a red light is not fashionable.


    Hey, don’t get me wrong – I think we’re on the same page for the most part. Maybe a different book, but on the same subject :P You want to hear something sad though… my hometown will not allow those solar roof tiles. “It doesn’t meet code.” Stupid crap of roof tile color!!! Yet one of my neighbors was allowed to paint their house canary yellow and put up a 6 foot privacy fence (hrmmm… robery? No witness? puh).

    “Yes. Because the people of this country have taken the easy route of letting the government run them instead of the people running the government.”

    Agreed… and to add – For some reason, something has to be fashionable to be acceptable. thankfully, not everyone shares these ideals…

  13. Alan & Michael,

    Charging batteries in series can have a detrimental effect on them because the batteries nearest the charger can get over charged while the ones further down the string don’t get fully charged and will eventually go below 80% depth of discharge (DOD) which kills deep cycle batteries.

  14. Alan says:

    I am no battery expert but I have worked on many systems that use huge battery banks and all charged many batteries in series. I am not sure I agree that batteries further down the string will be undercharged since there will be an equal charge current flowing through each battery and all being equal (which is not exactly true) the batteries will have the same charge voltage across each of their cells.

    Just my take on it, please correct me if I am wrong.

  15. I’m probably describing it wrong but you can find more info here: http://groups.yahoo.com/group/ev/

  16. Luke says:

    >Charging batteries in series can have a detrimental effect on them because the batteries nearest the charger can get over charged while the ones further down the string don’t get fully charged

    No. WRONG. Go to chapter 1 of your electronics 101 book and read about electric current.

    This is *NOT* how charging batteries works. High end batteries, like EV batteries, need to be charged by dedicated charging circuits that provide a CONSTANT, carefully regulated supply to a cell or battery of cells. A good charger CONSTANTLY monitors the charging voltage and temperature and how they change over time.

    You will **RUIN YOUR BATTERIES** if you charge them in this manner.

  17. ar0cketman says:

    The biggest problem with solar is it’s still a net drain on the energy system. It still takes more power to generate a solar array than it can produce over it’s lifetime. Things are nearing breakeven, however, and if the new South African solar technology pans out, solar will have long term viability, despite the fact that most US households use significantly more power than falls on their lots in the form of solar power.

  18. trebuchet03 says:

    High end batteries, like EV batteries….You will **RUIN YOUR BATTERIES** if you charge them in this manner.

    these are EV batteries… these are not the high end EV batteries that require special charging… these are AGM lead acid batteries (which I guess you could call “high end” for a non E-vehicle) ;)

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