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Thread: car battery

  1. #21
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    Copper Top

    Food for thought if you are going to use a Deep cycle Battery you should consider upgrading your Alternator. Allmost all of the new cars on the market have underrated Alternator.

    This casues a problem if you are draining your battery over and over, the alternator can never catch up, unless you plan on taking a nice long drive across country. To add to this problem if you never let the battery catch up you are just getting by as you run you system.

    The idea of Mfg's underrating the Alternators helps for gas mileage on underpowered engines. This should not be a problem with older cars and trucks, gasmileage was a concern then. The flip side of this is you will start to see mfg using higher voltage powersources in the near future. At the rate of electrical systems exceeding the powersouce, you will start seeing 24 to 48 volt systems. If you ever get a chance to see the History of the Auto on either the History Channel or the Discovery Channel. It showed a great insight on where the auto mfgs were going.

    While working the 12 volt field on heavy rescue equipment, we replace the OEM alternators in FORD and FREIGHTLINER units using 240 to 300 AMP ones. On top of that we use 4 to 8 Group 31 (deep cycle batteries).

    Of course what im describing would be over kill for a little 4 banger, Heck I doubt the engine could turn a 300 amp alternator under load lol.

    Anyway I just wanted to throw this in, due to the fact this has not been covered from my what I have read so far.

    If your gonna spend the cash on a high end stereo system budget in a little extra for a updated Alternator. Unless you like forking the cash over for new batteries ever so often.

    Now before everyone goes bashing me (I hope not). This doesnt apply to all installs just to the power hungry users out there and you know who you are...

  2. #22
    Maximum Bitrate SjLucky's Avatar
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    unless you plan on taking a nice long drive across country.
    I do that everyday to work... Oh the Joys of the Country Livin... I can **** off my front porch can you?
    Quote Originally Posted by menudude View Post
    thank you all for your help minus the useless post by sjlucky...

  3. #23
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    DaFlea: Food for thought if you are going to use a Deep cycle Battery you should consider upgrading your Alternator.

    This is not always true. There's no need to upgrade the stock alternator just because you're upgrading to a deep cycle battery even if you're running a decent stereo system with 500 watts RMS that can peak up to 1500 watts on top of the deep cycle battery. A deep cycle battery with a physical size to your stock battery doesnt have higher capacity than the stock battery. If it does, it's not much. The stock alternator will handle the deep cycle battery with no problems. The advantage of having a deep cycle battery is that if it does get deep cycled, it can be recharged back to near 100% of its original capacity. A none deep cycle battery will only be recharged to 70% of its original capacity at best.

    DaFlea: Allmost all of the new cars on the market have underrated Alternator.

    What's consider underrated? Majority of passanger cars have at least a 65 amp alternator. Some domestic cars have 90 amp alternators. Some domestic full size trucks have 125 or 140 amp alternators which are capable of running dual deep cycle batteries. If you ever look at the fuse panels under the hood, you will find a 7.5 amp fuse for charging. It's funny that you will never have to replace that fuse.

    DaFlea: This casues a problem if you are draining your battery over and over, the alternator can never catch up, unless you plan on taking a nice long drive across country. To add to this problem if you never let the battery catch up you are just getting by as you run you system.

    That's very debatable as to what extend does an alternator's output goes to charging the battery. Alternators never quit producing power. A battery is a constant load that the alternator has to keep charging. Even if the battery is fully charged, it is still a load to the alternator because of the voltage difference.


    DaFlea: The idea of Mfg's underrating the Alternators helps for gas mileage on underpowered engines. This should not be a problem with older cars and trucks, gasmileage was a concern then.

    I think you mean "gasmileage wasn't a concern then." underrating is not the right term you're looking for but I understand what you mean though. underrating would be like a 100 amp alternator that's being rated at 65 amps. I think you mean a lower rated alternator. Here's food for your thought. electronics now a days are more efficient than ever, meaning they use less power than it's predicessor. Let's say an 04 Camry's electrical system is 50% more efficient than the 1985 Camry. If the 1985 Camry uses a 65 amp alternator, wouldnt you think the 04 camry would only require a 32 or 33 amp alternator? Why would the 2004 Camry still use a 65 amp alternator then? I know that 04 Camry probably dont use a 65 amp alternator but I'm using that as an example.

    DaFlea: The flip side of this is you will start to see mfg using higher voltage powersources in the near future. At the rate of electrical systems exceeding the powersouce, you will start seeing 24 to 48 volt systems. If you ever get a chance to see the History of the Auto on either the History Channel or the Discovery Channel. It showed a great insight on where the auto mfgs were going.

    Yes, 36/42V system is in the works for quite a few years now.

    DaFlea: While working the 12 volt field on heavy rescue equipment, we replace the OEM alternators in FORD and FREIGHTLINER units using 240 to 300 AMP ones. On top of that we use 4 to 8 Group 31 (deep cycle batteries).

    God I hope so!! 4 to 8 group 31 deep cycle batteries?!?! you HAVE to upgrade the alternator no matter how you cut the cake.
    Let's use your example for a minute here. 240 amp alternator to 4 batteries. 240/4=60 amps per battery. 300/8=37.5 amps per battery. Pretty close to the 65 amp alternator to 1 deep cycle battery.

    Rescue vehicles would be considered as having life support onboard. They need un-interupted electrical power to power life support equipments. Fire trucks would need the power for the pumps and hydrolic latter and all the strobe lights. Which is VERY VERY important to have 8 deep cycle batteries and 300 amp alternator. a normal car would not have life support equipment onboard. So not having a high power alternator to power your 5000 watt system is not going to kill you.

    DaFlea: Of course what im describing would be over kill for a little 4 banger, Heck I doubt the engine could turn a 300 amp alternator under load lol.

    I know you're joking and I understand the joke but if you look at the numbers closely it's possible. (300 amps X14.4v)=(4320 watts)/(746watts/hp)= just under 6 horse power to power a 300 amp alternator.

    DaFlea: Anyway I just wanted to throw this in, due to the fact this has not been covered from my what I have read so far.

    It's actually been talked about here before. You just have to put 2 and 2 together to figure it out.

    If your gonna spend the cash on a high end stereo system budget in a little extra for a updated Alternator. Unless you like forking the cash over for new batteries ever so often.

    It took me 7 years and 104,000 miles to nearly fry my 65 amp alternator in my truck. I've had a decent system in my truck since the day I bought it. It still works til I turn it up loud.

    DaFlea: Now before everyone goes bashing me (I hope not). This doesnt apply to all installs just to the power hungry users out there and you know who you are

    I think in order to have to upgrade the alternator, you have to run at least 1000watts RMS and listen to constant bass all the time. Average joe and most of us, the stock alternator and battery will do just fine. Bass is what requires the most power. All of the music and voice require only 10-15 amps at high volume. Since every song you listen to has a beat to it it means that the bass amp is not producing constant bass notes all the time. This means the alternator is charging the battery when the bass faint or none and only powering the bass amp when the base note hits. Get the point?
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  4. #24
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    Quote Originally Posted by SjLucky
    I can **** off my front porch can you?

    Yeah, but the guy downstairs doesn't appreciate the fact.


    Back on topic, I found out on Sunday evening that installing XP sp1 plus all the MS critical updates since XP came out, drains my standard 6cyl BMW battery.

    Luickily leaving it overnight allowed it to recover just enough to start in the next morning.

  5. #25
    Variable Bitrate mutilator's Avatar
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    i used to have one of those casetronic cases with the internal dcdc, i left that on all night many a time, no problem
    if u did it too regular tho, it becomes great exercise in the morning.

  6. #26
    FLAC DodgeCummins's Avatar
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    There are a couple of other variables.

    A larger engine will require a larger starter, and therefore more powerful battery(ies). So like in my case the stock electrical system is quite stout, 120A alternator and dual batteries.

    Just running the standard fuel injected gas engine takes a bit of electricity. The intank fuel pump, computer, injectors, and ignition all draw off the alternator.

    Your built in accessories draw power, all the fancy lights, electric seat heaters, sunroof, power windows, etc. Also when you start your engine the battery is drained a bit.

    So when the engine runs, the alternator has to power ALL those accessories, AND recharge the battery.

    Big example, my truck has twin ceramic heaters to preheat the incoming air for cold weather starts...even with the engine running at speed, the draw on those heaters is enough to dim the lights when they cycle on.

    If the alternator cannot supply all the power you demand, then the battery will start supplying the rest...until the battery goes dead.

    A rough idea on how much juice these parts take is by reading the fuses for the various parts...obviously the fuses are rated higher than the actual draw (otherwise they would always blow) however they are only slightly higher than the actual draw...I doubt if they are even double the acual draw.

  7. #27
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    if you are soo worried, drop in a marine deep cycle battery in. just make sure it can supply starting amps and then some

  8. #28
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    followup

    I wont quote the whole reply becasue of the length of the post.

    I thank you for the math behind the madness. Really all I was getting at is the fact alot of owners try to push there audio systems beyond what the MFG rated the system for.

    And if you are planning on investing the money in a Carputer system you should seriously address the charging system as well. Either Deep cycle or standard OEM batteries. I was mearly explaning the background of a heavy rescue charging system.

    The issues about the 300 Amp Alt and a 4 banger is. A 300 Amp Altenator is allmost 12 inches round. I remember installing two of them in a unit that was sent to New Mexico where the avarage run was 80 miles.

    Talk about power to spare.

  9. #29
    FLAC cproaudio's Avatar
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    I just worked on a friends's 2001 Jetta 4 banger. It has a 90 amp alternator. i'dbe happy with a 125 amp alternator. It's enough to power my system full crank with out dimming my lights. I only have a 65amp on mine. It dims a little. The 1 farad cap helped a lot. 1 more thing. If you're adding just a CarPC to your vehicle but no system your stock battery and alternator will do just fine
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  10. #30
    Newbie Retuprac's Avatar
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    For those who are really serious about running a 12 volt system for an extended duration , the best setup is 2 6v
    golf cart batteries linked in series. A car starting battery might do 15/20 deep cycles , a deep cycle / marine may do twice that if your lucky, but golf cart batteries can be deep cycled 150+ times. I use this setup for my RV.

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