Improving charging system in an automobile.

Discussion in 'The Projects Forum' started by ksoggs, Jul 4, 2010.

  1. ksoggs

    Thread Starter New Member

    Jul 4, 2010
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    I spend a lot of time in my car. And i have a lot of electronics in my car.
    Many times i need to work out of my car, or spend significant amounts of time in my car using my electronics. I have a large and powerful laptop, phone charger, ipod charger, gps, small amp and sub, interior lighing, etc etc...

    I have found my alternator keeps up with the power demands all day long... but my wallet gets thin real fast from using all that gas. Sooo i decided to upgrade my cars abililty to power me without the engine on.

    I have gotten a hold of some powerful deep cycle batteries, should give me plenty of power to do my road side duties without needing the engine running.

    BUT.... i want to setup some better control of the charging system to keep everything, including myself, happy. So here are a list of things i would like to encorporate into my charging system....

    1. drop alternator output to closer to 13.7v. (either try to adjust my current volt regulator, or add in a second adjustable one) (currently sits at mid-14v and i am told this will cause a deep cycle to gas over time and shorten its useful life. the battery is rated at 13.6-13.8 float voltage, so i thought dropping my overall alternator output to this level would keep my batteries happy for much longer. but i know it would take longer for them to charge back up.... unless part 2)
    2. add in some type of multi-stage charge controller. I would like to be able to add bulk, absorption, float, equalize charging to my cars system... I know in RV's and Boats they make little units that plug into the normally-fixed votlage output, and it adds these features, evern some solar systems have that as an upgrade feature... but i have not seen anything like this for a car's alternator. So i wondered why not? and how can I adapt one to work for an alternator? or how can i make my own to do this?
    3. I would like to include some type of battery level indication and control... maybe a voltage gauge to keep an eye on how much battery i have left and how fast im using it up.... but more importantly, some sort of undervoltage-cut-off. if i am really wrapped up in my rest-stop-research, and i forget i am on battery power, the cut-off will kick in before i get to the point i need to get a jump.
    4. i also toyed with the idea of a dual pole voltage switch, i had thought about adding a solar panel charger to the car... but would like it to be disconnected when the alternator was on, but kick back in when the car wasnt running. I would also like to have the option to have certain accessories turn on or off based on the system voltage... so say maybe have a little flashing LED light up on the dashboard like an alarm warning, and the solar charger enabled when the car is off (13v or less) but then have the solar panel and led turned off, but something else is turned on, like a phone charger....

    Yes, i thought about just relying on the key of the car... and just using relays to do all of the above. But i would feel much safer if this was all done based on voltage, not on a key. A key only gives you on and off... i would much rather have a few steps... engine on and voltage above 13v = everything on but solar charger and alarm warning light... then say from 13v down to maybe 11.5v everything is on... including the LED and solar panel... but then if voltage drops below 11.5 then the batttery is disconnected and power reserved for starting only. perhaps only the solar panel connected at this point.


    All just ideas at this point... Have been wanting to talk about them with some people in the know... and see if there is a better way to do this, or if i some steps are not needed....

    I have read a number of other threads on here with people asking about one part here or there... but i wanted to lay out my whole plan, get some feedback. and didnt want to steal someone elses thread.
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    Sounds to me like you just need an RV with a built-in generator.

    No point in trying to build a Rockefeller Center in a 4-door car.

    Solar would be pointless for you. You could cover every square inch of your car and you still wouldn't get enough power.

    You need more efficient toys.
     
  3. ksoggs

    Thread Starter New Member

    Jul 4, 2010
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    no... i dont need that much power at all.... But yeah that would be nice....

    Between my laptop battery, and some car battery, i usually have enough power for most "stops" But i have come pretty close to not being able to start the car back up a few times. And i know that is bad news for a starting battery to get that low.

    So adding a little more power (larger deep cycle battery) and some safety features should be all i need.

    the solar is not to power my devices at all. The power supply on my laptop alone is 65w... (it is one of the DC-DC cig lighter power supplies, not and inverter and a 110v supply) But 65W is way under rated for my laptop. It is a 17" portable workstation... and is designed to run on a 150w+ power supply. The 65w just suppliments the laptop battery... if i let the laptop battery die, it can take hours before it even shows a single bar charging at 65w. So 65w is the bare minimum to keep my laptop running..... and i know a solar panel the size of my entire trunk is only good for about 15watts... So i had no intention to run anything off solar... that is more or less just to keep things topped off and charged up when i am parked.

    Granted NONE of this is needed at all... I could just find a dennys and order a coffee and use their wifi and outlet... problem solved.

    but i love creative solutions to things.... and i would like to make some electronic gadgets that will help me to work around this little hurdle.

    To me it is more about the journey and the lessons learned along the way. Yeah i could just buy a kit and learn to make my own AM radio... but what do i want an am radio for??? I would rather practice making things that would actually help me solve a problem.

    I come from a computer background. So i know all of these things are super simple to do on a computer with logic... "if V >13.5 then...." etc...

    and i know much of this can be done manually... NO relays and NC relays wired into the switched ignition...

    So i have to imagine that it shouldnt be too hard to do any of the above... i just need a way to "sence" the voltage and be able to use that as a "switch" There are such circuits in use all the time.... i would just like to learn how to make and use them.
     
  4. ksoggs

    Thread Starter New Member

    Jul 4, 2010
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    oh yeah.... and it isnt a 4 door. It is a 2 door 4cylinder.... 2008 chevy cobalt.... and i think my gas usage at idle is probably pretty close to that of an RV generator.

    My Ex had a big RV... which is how i know all about the deep cycle batteries and their charging systems.

    point here is not to use gas. but just to get a little more use out of stored power and free energy.
     
  5. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    Do you know how much power you need, and for how long?

    What is the total wattage requirement of all of the devices you use?

    It's very hard on an automotive battery to be drained like that. They're designed to provide maximum current for a short burst during engine cranking, and then to be immediately recharged. The way you've been draining it during stops, look forwards to buying a new battery within the year. It's likely the plates are already crumbling.

    Do you have an idea where you might put such a battery, or how large it would need to be?

    Unless it's a sealed lead-acid battery, you will need to put it in the engine compartment, as the fumes vented are potentially explosive - so good ventilation would be mandatory. Having a large, heavy object like a battery in the passenger compartment is an obvious hazard; it would need to be anchored to the chassis somehow. This means doing things like drilling holes in the floor to mount anchor points, and running heavy-gauge wiring through the passenger compartment or underneath the car. Since it is not a good idea to penetrate the firewall, you will probably have to run wiring underneath the car to the engine compartment. If your vehicle has a cigar/cigarette lighter (many newer vehicles do not) then that could be used for a power access point.

    Adding a large SLA battery will increase your vehicle gross weight, which will decrease performance and fuel economy just from the weight - then add in charge requirements on top of that. By the way, charging/discharging a battery comes at a cost; charging is only about 75% efficient. For every amp you put in, you only get 750mA back out. The higher the charging/discharging rate, the more power is dissipated as heat, with the exception of some newer AGM batteries.

    A 65W output 90% efficient supply represents about a 5.6A current drain on a fully charged battery. As the battery discharges, the current drain increases significantly. It's just about like leaving your headlamps on.

    That would be a bargain indeed - great coffee and truly cheap power.

    Just making these "gadgets" is going to be quite a chore, and require an intermediate-to-advanced skill level.
    For example, the battery charge controller - an AC-powered version of a lead-acid battery charge controller is here: http://focus.ti.com/lit/an/slua058/slua058.pdf
    Such a design can be quite efficient, and maintains the battery at optimal levels. Adding temperature compensation would make it a very good design indeed. Have a read through it and see how well you understand it.

    Have you built electronic projects before? I don't have any idea of your skill level.

    Well, sort of. Relays are cheap, and tolerate a lot of abuse. However, as long as the coil is energized, they're using power.

    I see. Well, first off, you need to spell out your power requirements, and see how far you can whittle them down, yet still get done what you need to do.

    I haven't looked under the hood of one of those, but I think I'd find a sewing machine in there... ;) Newer vehicles really have the engine compartment packed, particularly in compact vehicles. So, that pretty much leaves out anything but a SLA (sealed lead-acid) battery in the passenger compartment.

    There is no "free energy", it all comes at great cost.

    A charge controller might be around 90%-92% efficient.
    Charging a lead-acid battery is roughly 75% efficient.
    Right there you're down as low as 67.5% efficiency - and that power has to come from your alternator while your 25% efficient gasoline engine is running.

    Did you know that you can reduce your workstations' power usage considerably just by enabling its' power-saving features, like reducing the CPU speed and automatically turning off the HDD after a brief period of time?
     
  6. retched

    AAC Fanatic!

    Dec 5, 2009
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    Also, there are usually backlight options for laptops to save power. Look in your power-saving options. There should be a dim setting. That will cut usage by a decent amount.

    Also, in your device manager, you can set devices to sleep after x amount of time.

    This will keep your wi-fi from searching for a signal the whole time you are not using it.

    Parking the HDD and changing refresh rates, as well as lowering the resoloution of the monitor and or the color depth.

    That all makes processors work harder and hotter.

    Harder=more juice
    hotter=more juice
     
  7. Wendy

    Moderator

    Mar 24, 2008
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    While solar couldn't power that setup, it could recharge it some. Better than nothing I'm thinking.

    I'm wondering if SLA (Sealed Lead Acid) batteries could handle the temperature extreme you get in a trunk. They definitely aren't as efficient, but could be a good alternative.

    You might need a heavier duty alternator. Looking for more efficient devices is definitely a worth while project.
     
  8. ksoggs

    Thread Starter New Member

    Jul 4, 2010
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    in brief.....

    i have my laptop setup on as much of a diet as it will let me go..... all the things you guys mentioned are already in place... HDD, backlight, sleep, hibernate, cpu speed, fan speed, video power, wifi disabled, etc etc.... i spent hours setting up my power scheme for battery savings. but this is a big laptop. it is a portable worstation. 17" screen with 1920x1200 res. quadro workstation graphics, 4 gb memory, 2 internal hard drives, quad core cpu. this laptop puts most desktops to shame... but yeah, battery life is not a strong point.

    but as i mentioned... the laptop is the primary requirement here.... my current power suppy is a 65w dc-dc model... the laptop doesnt like the fact its only 65w... it would prefer something 150w or greater... but it deals with it on my power saver scheme.

    I would like to get at least a couple hours of laptop usage without the engine running. But i would not mind more....

    i also like to camp and tailgate.... so would be nice to be able to play the radio for hours, or run 12v accessories or a inverter for a while without needing the car running or fear of a no-start.


    my "sewing machine" happens to put out over 300hp... faster than most cars on the road, including most sports cars under $50,000. and does all this while still getting 33mpg freeway. (that was another "project" i tackled a year or 2 ago)

    The battery is already trunk mounted from the factory... and i planned to install the depp cycle there. i am working on a battery box/tray for it right now.
    the battery i located is a 135Ahr AGM SLA High rate deep cycle. it has a service life of 10 years if kept at a 13.8 max float.
    so this should solve most of my issues... but i need to make the car more battery friendly. i dont think the battery would like the 14+ volts of constant power my alternator puts out.

    and that is why i am here!!!! so help a guy out!
     
  9. ksoggs

    Thread Starter New Member

    Jul 4, 2010
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    oh yeah... here are some pics....
    here is the battery i am going to try to use....
    [​IMG]

    and here is where i will be mounting it....
    [​IMG]

    notice i placed it on the passenger side... the battery weighs 105 pounds... i weigh over 200 pounds... i sit on the driver side... so this guy becomes my counterweight.

    yes, i am aware 100 pounds of lead in the trunk will reduce performance and economy. but considering i made a 3 hour trip the other day with me (200 pounds) my buddy (300) and 400 pounds of cargo... and still got 33mpg average on the ride back... and that included racing and beating a brand new camero rs. (mind you that was with nearly 1000 pounds of added weight and a full tank of gas....)

    so yeah.... no energy is "free" but when it is a biproduct of something that is going on anyway... it is close enough to free for me.
     
    Last edited: Jul 4, 2010
  10. retched

    AAC Fanatic!

    Dec 5, 2009
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    This is easy. You need a battery isolator relay.

    It will monitor your batteries voltages (The accessory and the starter) and switch the alternator between the two, giving the starter battery priority.

    This will keep the trunk batteries topped up during drives.

    As for getting more hours of usage, That will just require more or bigger batteries.

    Here is a cheaper one:
    http://www.northerntool.com/shop/to...s&cm_ite=171214?ci_src=14110944&ci_sku=171214

    But I would find one that has active monitoring and switching.

    These also keep your starter from sucking your accessory battery and such.

    You may also consider a second one of those big mamba-jamba batteries to improve life.

    Remember to keep an eye on discharge rates and depth. You dont wanna suck these things dry.
     
  11. ksoggs

    Thread Starter New Member

    Jul 4, 2010
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    Yeah, i thought about the isolator relay... but that still does not change the fact that the deep cycle isnt going to like the 14.4 volts of constant current for long drives.... I would still like to scale it back to its suggested float voltage of 13.8 if possible.

    and i totally agree with you.... I need to watch discharge voltage... i have no desire to drin these things to nothing... i know that the deeper the discharge the shorter their expected life... which is another reason for asking about a low-voltage cut off. in case im not paying attention... and i do suck more than i wanted to... it cuts me off.

    and yes, a solar panel wont power anything i need... but it will help to slow the battery drain, and help to charge things up when i am not using the car.


    see i have already thought about all this stuff... i just need some help on how to make it happen.....






    OH... i know how to solder, i know about logic and basic electrical stuff.. i have played around with breadboards and such... i am a newbie to making stuff from scratch, but i am a fast learner....
     
  12. retched

    AAC Fanatic!

    Dec 5, 2009
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    It wont need the constant float voltage.

    Once it is full, the relay will switch to the starter battery.
    I dont know if the one I linked to has that option, so search around. There are ones that switch between the two.
     
  13. ksoggs

    Thread Starter New Member

    Jul 4, 2010
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    yeah but see... what do i learn from buying something like that off the shelf?

    I would rather learn how something like that works and make it myself.... that is half the fun....

    anyone can buy something... not everyone can make their own.

    ok..... how about this..... why doesnt someone tell me how to make a simple "voltage sensing switch" something that monitos a circuits voltage.... and opens or closes another circuit based on a given voltage....

    you give me that much.... i can figure out the rest...

    make a few of those switches, hook them up to some relays... and i will be able to make my own isolator relay setup to charge the deep cycle till full, then cut out....

    not the ideal setup.... but at least it is simple and i learn something...

    i get the idea no one wants to help a guy learn how to make stuff.

    i dont expect to be able to compete with intel in a month or anything... but with what i do know about electronics and logic and all, i cant imagine that most of my requests are all that complex....


    i am fine with modifying current electronics too.... like i dont need to make my own 4 stage smart charger from scratch... but if someone can tell me how to eliminate the AC portion of it... and configure it to go from 14.4V dc input to the multi-stage output and a final float charge of 13.6 or so... that would be swell...

    i know it cant be hard to make a voltage switch.... i have several of them on simple electrical devices i already own.... i know there isnt much to the entire device... so there cant be much to the part that "turns off unit based on batery power as set by the pot on the side"

    Im a pretty smart guy... i am very good at figuring out how things work.... but i just need some fundamental knowledge so i feel safer trying things out.... i dont want to assume "oh all i need is a pot to set voltage cutoff" when surely the pot is only giving an input to a more complex device that actually controls the switching....
     
  14. retched

    AAC Fanatic!

    Dec 5, 2009
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    There are battery charging ICs that you can use that will properly monitor voltages and use a multi staged charging modes for proper charging and maintaining. You can set the voltages by using external components.

    Also, you can make a upper-point voltage switch with a few (or one properly rated) zener diodes and a relay.

    Zener diodes conduct when the zener voltage is reached.

    So if you have a 13.9v zener diode connected to the coil of a normally closed relay, once the voltage reaches 13.9v it will conduct, energizing the relay and opening the circuit.

    You can use the relay in-line with the cable from the alternator to the battery so when the voltage of the battery reaches the zener level, the relay cuts charging.

    When the voltage drops below the zener level, the relay will de-energize returning to a closed state and continuing the charging cycle.
     
    ksoggs likes this.
  15. ksoggs

    Thread Starter New Member

    Jul 4, 2010
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    See now THAT is the good stuff i was hoping to find on a board like this... just that simple lil bit of knowledge about zener diodes opens up worlds of possibilities....


    and where do i find these battery IC's... how hard are they to setup? will they run off a 14v alternator input? or they designed for AC to dc?


     
  16. ksoggs

    Thread Starter New Member

    Jul 4, 2010
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    so i assume i would only need a zener diode with a wattage high enough to power the relay i was ussing.... it wouldnt need to be rated for the alternator output at all right?

    and what would you say would be a good cut-off voltage? and what volatage would it be monitoring? actual battery voltage? alterntaor voltage? a combination of both?

    for a agm sla... with 14.?v constant voltage input... at what point would i want to cut the charge to the battery? and then how do i group the diodes to get a voltage that i want, if not available already? (if i wanted say 14v... but they only came in 15 and 12... are they like resistors? just add them up in series? average in parallell?)
     
  17. retched

    AAC Fanatic!

    Dec 5, 2009
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    The zener need only be rated for the what the relay coil will draw. not much at all.

    I would be measuring the battery voltage.

    This is not going to be as easy as you think.

    In order to measure the battery voltage, you have to disconnect the charger for a few milliseconds read the voltage and decide what to do.

    Thing is, the battery will be at (or will be read at) the charger voltage.

    So you would need some logic to open the relay, if the zener conducts while the relay is open, keep it open.

    You could do this with a dpdt relay, a timer and some logic.

    You could open the relay to measure the voltage every minute or so, if the battery voltage is over the zener voltage while the charger is disconnected, it would stay disconnected. Once the zener stops conducting, the process restarts. Opening the relay to check every minute again and again.

    Or, use an IC:
    http://focus.ti.com/docs/prod/folders/print/bq2031.html
    http://www.linear.com/pc/viewCategory.jsp?navId=H0,C1,C1003,C1037,C1078
     
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