Minimum voltage needed to start car?

Discussion in 'Fuel Economy' started by Sulfuric, Jan 6, 2013.

  1. Sulfuric

    Sulfuric Well-Known Member

    After getting into a crash on June 1st :( I got a new (to me) car, a 1996 Honda Accord, manual transmission.

    I recently bought an Ultragauge and am very happy to finally be able to see all the details.
    My main question is this:
    What do you think is the minimum voltage needed to start my car?
    If driving normally, it hovers around 14.2 volts, and when in FAS it drops to the mid 12 range. However, during my nighttime P&G it's been falling to as low as 11.5v toward the end of my trip. I'm just concerned that it might drop so low that I won't be able to start my car with the key.

    Relevant: I have an Optima Yellow Top battery, only 6 months old, and my starter is takes an average amount of volts/amps to start the engine

    Edit: this probably would be better off posted in "General" but I forgot how to delete threads so help me FSM
  2. herm

    herm Well-Known Member

    No idea about the voltage but it has to be fairly low since all it has to do is provide ignition, fuel pump etc and drive the head lights.. the head lights must consume much more than all those other. You are not using the starter right?

    Sorry about the crash, I hope all is well healthwise.. tell us more about the Accord.. price??? :)
  3. herm

    herm Well-Known Member

    Here in Miami all Accords are made of gold, I think they appreciate when you drive them off the lot.

    CPLTECH Well-Known Member

    Voltage drops even in a new battery when a high current starter is energized. I think the best thing to do is to kick-start whenever possible, as Herm implies. Also, is your driveway on a slope so as to kick-start in the AM? Many do not realize the additional fuel the alt takes to run the lights or the blower since the minimum idle is computer regulated. Those of us that drove carburated cars heard the engine slow. My SG2 shows at idle a 10% increase in GPH whenever those are turned on. It seems to me that the small cars have a low amp capacity alt compared to the big engines so that it doesn’t tax the little motor so much. That may be why it can not keep up with the battery.

    Be aware that batteries are made for certain purposes. A marine battery for trolling is designed to give a certain AH over a “long” period of time, but poor as a starter battery. Whereas a car battery will give lots of amps briefly to start the car, but not so good over a “long” period of time. When replacing a battery, I always opt for the largest CCA I can get in that size. Usually doesn't cost that much more.
  5. Sulfuric

    Sulfuric Well-Known Member

    I'm talking about starting the engine with the starter, perhaps at a light somewhere on my drive back from work. No driveway (apt complex near college), and I don't have a marine battery, I believe that would be a "blue top". Optima makes reds for normal cars, yellow for vehicles that run a lot of accessories (big stereos and the like, I think, but also doubles great when P&G'ing a lot), and blue for marine.

    Accord details:
    $1400 from small time dealer (plus taxes), ~145 miles
    Approx $1.2k in repairs + new tires immediately (I knew that would happen)
    Rack and pinion went bad about 2 months later
    Rack and pinion fixed for free like it should have been, but they *did NOT do an alignment afterwards* and I forgot
    Drove 120 miles out of alignment
    New front wheel bearings + alignment + something else needed ~$450
    Something + alignment when I went home ~$230
    Hopefully fixing chronic alignment problems tomorrow
    I didn't stick up for myself when I should have and made the shop pay for my front wheel bearings, so lesson learned there hopefully :(
    Overall very sour about car but very happy with mpg
    Also the passenger inside door handle broke and the windows are slow to roll up in the front
    Last edited: Jan 7, 2013
  6. CRT1

    CRT1 Newbie McNewbster

    I find that I start to have problems in my FIT the 11.2-11.4 V range with a fully warm engine. It will still start if it drops that low but that is when I start to get really worried. I'll ease up on the FASing until I can get the battery topped off again.

    Also, note that it is MUCH harder to crank a cold engine than a warm one, so you will need a higher V to start your engine before it is fully warmed up. I also try to use my ear and ease up when it doesn't quite sound right starting up. This is sometimes at higher Vs.

    A lot of the guys around here who FAS a lot use a trickle charger at night. I don't have an outlet near my parking spot so I have been topping off my battery about once per week. Probably not good for battery longevity but its all I got.
  7. priusCpilot

    priusCpilot George

    What kills the battery as some of you guys know is the sulfation buildup on the plates. Im testing out a few disulfators out so once I know whick one works Ill post. They make one that you just leave on the battery and it keeps it from building sulfate. Also you can setup and solar charger so alls you do it plug it in were you park.
  8. herm

    herm Well-Known Member

    Maybe one of those solar chargers on the dash?.. only way to keep the battery alive on a friend's car with only a 2-3 mile commute.
  9. WriConsult

    WriConsult Super Moderator

    Twice, on my previous car, I inadvertently let the voltage drop too far while FASing, and found myself unable to restart at a red light. In one of these instances my Jetta's battery was starting to fail, and in both instances the voltage drop came on earlier than you might expect in broad daylight because that car's DRLs are active anytime the key is in the RUN position.

    Unfortunately I had not been watching the voltage prior to either of these incidents (or they wouldn't have happened) so I'm not exactly sure how low it had to go before I couldn't engage the starter.

    Ever since then, I have made a point to always have the VLT gauge displayed on my SG, and I watch it carefully anytime I'm FASing in city conditions, especially at night when I have the headlights on. Basically I start to get nervous anytime the voltage drops below 11.5, though I don't know exactly how far I can safely let it drop.
  10. some_other_dave

    some_other_dave Well-Known Member

    Starting is one thing, running is another. My old 914 would die below 9V, probably because of the aftermarket electronic ignition setup I had in it. I think with points, it would have run lower than that.

    On a modern car, there is probably a good bit of head-room between normal system voltage and "too dead to run the car". I'd be worried if it dropped below 10 at any point, but I think 11 is OK for the short term. Over the long term, low charge levels (e.g., below 12V) can lead to battery damage or at least it dying on you earlier than it might.

    How much voltage it takes to crank the engine over depends on lots of things. How easily the engine cranks (e.g., high compression and new tight motor or low compression and old tired motor, oil thin and warm or thick and cold, etc.), how efficient the starter motor is, how much capacity and internal resistance the battery has, what sort of voltage drop there is through the power and ground paths from the battery to the starter and back, and so on. Many of those things vary from start to start even on the same car.

  11. herm

    herm Well-Known Member

    A deep cycle battery is fine for starting 4 cyl cars in Florida, modern fuel injection plus geared starters makes for instant starts.

    I would think you need to expect a certain level of repairs in a 96 car, bearings and a steering rack perhaps means crash damage?.. but bearings need to be repacked and seals replaced at some time or they will fail. I hate old style power steering, nothing but headaches.

    Water pumps, timing belts, hoses, belts, radiators, thermostat, antifreeze, brake cylinders, brake master cylinder, brake fluid (should be replaced often in Florida due to the humidity) and probably MT components such as the master and slave pumps plus fluid should be maintained.. all this stuff is easily done at home with minimal tools. Replace the the cables, coils, sparkplugs every 100k miles or so, use OEM parts.
  12. EdwinTheMagnificent

    EdwinTheMagnificent Legend In His Mind

    I wore out the steering rack in my 89 Civic and there were no (front-end) accidents. In the first five years I owned the car I considered it to be a go-kart and drove it that way. Manual steering , the way a car's s'posed to be. After about 12 years and 200K miles , you could steer the car with just the throttle. I automatically would turn the wheel a little bit when accelerating to compensate. The price of a new rack was HUGE , and I had other parts of the car to keep alive as well.
  13. RedylC94

    RedylC94 Well-Known Member

    That's surprising. No problems with the manual rack in my Subaru in nearly 200K miles, or the one in the GLC in 587K, although all four tie rod ends have been replaced in the latter due to wear.

    I agree with Herm about "old style power steering," especially in vehicles that do not need it.
  14. some_other_dave

    some_other_dave Well-Known Member

    You can steer all cars with the throttle! :) Turn the wheel some, then control the actual line the car takes with the "loud" pedal. More gas == wider line through the turn, less gas == tighter line through the turn.

    ...Of course, if you're not near the limit of adhesion that might not work as well. ;)

  15. Unleaded

    Unleaded Well-Known Member

    My car will start at 10 volts. Ask me how I know.
  16. MaxxMPG

    MaxxMPG Hasta Lavista AAA-Vee Von't Be Bach

    I remember reading in an old GM service manual that the PCM shuts down at 10.2v to protect the circuitry from low voltage. In that event, even if the starter cranks or you try to push start a manual, the engine won't fire because it's "brain dead" - no spark and no fuel injection. I'm sure that varies from make to make and even from one platform generation to the next, but it suggests that heading below 11 volts is greatly increasing the odds that you're going to need a set of jumper cables.
  17. phoebeisis

    phoebeisis Well-Known Member

    Wow-you guys some sort of dirt track racers-steering with throttle
    Or maybe those crazy Euro trash running those "street looking " rally cars all over creation-snow etc-lotta funny Finland names-(Finlanders are excluded from the Euro trash comment)(two n's or one?)

    Gotta agree with Herm- a $1200 16 year old car Gotta' expect to dump PLENTY of $$ into it-maybe 200,000 city miles-yeah Herm claims no potholes-but city miles are HARD miles-

    In my 61 years-I've learned to buy the absolutely best(usually most expensive) used car-you can afford.
    Maybe One owned by some lawyer with a LLP who claimed it as a business car-so he could write off the maintenence(giving him a 50% discount on it) the downside is affluent folks are a pain to deal with-won't come off their price like poorish folks-me- will.

    Of course you bought a $1200 car- because that was what you could afford-hoping to find a diamond on the rough-sometimes you luck out-my Suburban-195,000 miles-$2950-lucked out because gas was so expensive even well cared for Suburbans were dogs to sell.
    That NEVER happens with Hondas-

    Oh don't beat yourself up on demanding they pay for the bearings-probably had nothing to do with the no alignment-just worn out-
    besides-shops can AND WILL just tell you-NO this isn't our problem-nothing you can do about it-and they are now pissed at you-and might not do as good a repair
    It is helpful at some shops-to find out who will do the actual repair-slip them $5-and imply more is coming-do this BEFORE they start work on it-tell them you know they work hard- like you-all true-so you appreciate them doing a good job
    Yeah do give them a bit more-$10 post labor-
    in some shops they really push the mechanics hard-time wise and pay wise
    $20 more bucks on $1000 in repairs-not much
    ps Like herm said used Hondas-rarely bargains used-great cars-but they just don't depreciate like a chevy Suburban for example-and they are expensive to repair-not as wide a selection of Ebay cheapo but adequate parts-one chevy advantage if you DIY
    SOMETIMES-it might make more sense to buy a low mile Cobalt or Malibu or Focus or even Aveo (don't yell at me guys-esp about the aveo)
  18. herm

    herm Well-Known Member

    Charlie, write an article on best used cars to repair and buy.. but properly researched with costs for repair parts and assume all do it yourself.. dont forget to add the cost of gasoline.
  19. some_other_dave

    some_other_dave Well-Known Member

    No dirt for me, just pavement! Well, there was dirt when I overcooked my entry to turn 10 at Thunderhill and had to drive straight off, but I'm not counting that. ;)

    Also very large parking lots, with a course laid out in traffic cones. Yes, I was (and hope to be again!) an autocrosser.

  20. The Doctor

    The Doctor Old Dude, New Car

    Just a thought!

    On another forum, one member commented that he was having starting problems.
    The starter would growl a little but the car would not start.
    Making a long story much shorter..... he found the problem was the Mickey Mouse grounding between the starter and the NEG terminal on the battery.

    The grounding path was from the starter into the engine block, and from the engine block to the Rt side shock tower, then through the body to the Left side shock tower and through another small cable to the battery.
    The point where the grounding cables attached to the shock towers was a heavily painted surface, so the only ground was through the little bolt that held the cable in place. He cleaned off the paint under the cable ends and that solved his grounding and starting problem. His dealer was of NO help at all in solving his problem.
    It was definitely a DIY fix.

    I had not had that problem, of poor starting, but after reading about the fix, I implemented it on my own car, with the addition of a heavy 24" ground cable from the top of the engine (a convenient attachment point) to the NEG terminal on the battery. I should NEVER have a starting problem due to improper or insufficient grounding.

    I also take steps to prevent corrosion on my battery terminals, with Anti-Corrosion felt washers under the terminals and some A-C spray on the terminals themselves.

    So I'm just wondering...... how many other cars might have a poor ground path between the starter and the battery. :confused:

    What you're seeing on the SG with the motor running is the output of the alternator, not the resting voltage on the battery itself. With the engine off, put a digital VOM across the battery to check its resting voltage. It should be over 12.0vdc, if it's charging properly.

    I just now checked my own battery. The car has been OFF for about 18 hours and the battery voltage is 12.67vdc. I would consider that normal, for Florida anyway.


    PS: By their chemistry, maintenance free batteries take longer to charge and higher voltage to charge completely, than do the full maintenance batteries.
    For that reason, I prefer a full maintenance battery for my own car. My new car came with a Maintenance Free battery, but if I lived up North where I'd be doing a lot of short trips and COLD Starting, I would replace it with a higher capacity Full Maintenance battery.
    I notice that when I see batteries on the rack at the retail stores, most of them are the Full Maintenance type.
    Last edited: Jan 11, 2013

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