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CAR BATTERY GOES DEAD AFTER 5 STARTS

 
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ronhedien ronhedien
New User | Posts: 2 | Joined: 10/10
Posted: 10/05/10
01:01 PM

I have a 1985 Bronco (big one) 302.
With a new battery (tried 3 different ones) fully charged the battery goes dead inside of three or 4 attempts. Alt charges, all new cables, etc.
I can sit in the driveway when the Bronco is cold, fully charged and start and stop 15 to 20 times in a row before it starts to drain the battery.
It seems to start better when the Bronco is cold. If I drive it around town or in the country it runs fine, showing charge all the time but after it gets to running temp and when I stop for awhile it will barley start the first time and second time, after that it might click a few times and goes completely dead. I carry one of those jump start batteries, hook it up and it starts right up until the next try. Ohm meter shows 13 amps when running, even with the lights, heater, radio all on.
Any thoughts ???
Ron.  

waynep7122 waynep7122
Addict | Posts: 4561 | Joined: 08/09
Posted: 10/05/10
04:51 PM

this might be a little complex...  but its fixable...

do you have a digital volt meter... they start at about 8 bucks and you don't need to spend over 25 or so...

you are also going to want to print this out...

first.. engine off....  take your thumb... find the alternator.. its got a fan blade on it.. push on the alternator fan blade with your thumb.. if you can move the alternator without turning the rest of the motor.. the  alternator belt is loose...  there is a critical adjustment.. where you find out where it just slips and then go a little tighter...  if you go much tighter.. you will ruin the alternator and water pump bearings......


now that you have verified that the alternator belt is not slipping...

take your digital volt meter... set it to 20 volts DC...
engine off... headlights on for one minute then off...

measure across the battery...
12.65 volts is a full charge..
12.45 volts is a half charge..
12.25 volts. is a quarter charge..

you really need to have a full charge... for proper testing..

now.. start the motor....

if your alternator is working.. you will have 14.1 to 14.6 volts DC...

the tests above.. take about 4 or 5 minutes...

these next tests take another few minutes...

with the engine running and the head lights on...

volt meter still set to 20 volts DC...

1. measure the battery voltage.. 14.1 to 14 .6 is good..

2. measure from the negative battery post to the engine block.. 0.04 volts is good..

3. measure from the negative battery post to the body... 0.02 volts is good...

4. measure from the engine block to the body (firewall area) 0.02 volts is good...


5. measure from the alternator or engine block to the voltage regulator case..   0,01 or 0.02 volts DC...


post your results...  

waynep7122 waynep7122
Addict | Posts: 4561 | Joined: 08/09
Posted: 10/05/10
05:06 PM

i want to keep this separate...

batteries can be discharged slowly.. or fast...


but can only be charged over hours... if deeply discharged..

a booster jump will not put enough recharge back into the battery for it to do more than a quick start..

a Deeply discharged battery...   will be cooked and ruined by trying to charge it with the alternator...  it has to be hooked to a 10 amp charger for a few hours.. or until the amp meter on the charger starts to drop...

a deeply discharged battery that has sat deeply discharged for a few days or a few weeks can  be brought back if you don't try to charge it in a normal fashion.. with a current limiting adjustable power supply...  i charge deeply discharged 12 volt car batteries at 17 volts at 0.25 AMPS short circuit current..   thats 17 volts at a quarter amp max...  this trickles electrons back into the battery and reverses the chemical reaction... this slow charge takes a few days usually... On the Power supply....

if you fast charge it...  or  try to charge it with the alternator.. you will cook and harden the plates and ruin the battery...    the cost of current limiting adjustable power supplies greatly out price a battery.. most are around 300 bucks. and up.... electronics guys use them.. since  i work on a lot of electronics it just payed to get one..  

ronhedien ronhedien
New User | Posts: 2 | Joined: 10/10
Posted: 10/06/10
11:54 AM

Hello,
Thank you for your reply. I had a garage check all of the above after I did just to confirm my findings which were right on with what you said they should be.
They installed a new starter solenoid and changed out the new battery they installed with another new one.
I drove from the shop to the pet store (4 miles) started fine. Then went on to the food store, parked and came out to a almost dead battery, after a couple of tries it finally caught. drove home (2 miles) and shut it off. Tried to start it 5 minutes later and the new battery was dead as a door nail.
What do you think about replacing the starter ???
Ron >>>  

waynep7122 waynep7122
Addict | Posts: 4561 | Joined: 08/09
Posted: 10/06/10
12:59 PM

can you do the battery negative post to engine block while someone tries to crank the engine...?????/

can you monitor the battery voltage.. while its running???/

it should have 14.1 to 14.6 volts.. running....

since that truck is equipped with an external voltage regulator..   i have had serious problems with the wiring between the back of the alternator and the regulator becoming intermittent...


let me explain the wires at the regulator...

F S A I

F is field.. goes to the Fld on the back of the alternator.. this is one of the brushes and the regulator pulses voltage to this to vary the amount of magnetic field created by the spinning rotor.. bigger magnetic field .. more output..

S  is the stator connector  goes to the STA on the back of the alternator...  this is connected to all three phases of the output windings... where they are connected together..   this will have when measured half the output voltage of the alternator when the alternator is charging.. but it has AC voltage...  not dc... it is also usually the power source for the electric choke on carburetor equipped models..

A    this is only at the regulator..  depending if you have an amp meter or a alternator light..   one will be switched power...  the other will be full time battery power..

I   this is only used on cars and trucks with an alternator light.. not and amp meter.. it switches the voltage regulator on.....

but there is another small wire on the back of the alternator...  that is the ground wire...  its goes to the base of the voltage regulator.. where it mounts.. this keeps the alternator and the voltage regulator at the same ground plane ...  remember the engine is sitting on rubber..

so.. take your digital volt meter... with the engine running..    20 Volt DC scale...  probe the A terminal on the voltage regulator.. usually a yellow wire.... do you have power .. same as the battery...

then   switch the digital volt meter to 20 Volt AC scale... or 200 volt AC...   you should have half of the charging voltage when the alternator is working...      if you get ac voltage there and the alternator is not putting out the full charging voltage.. you might have bad diodes in the alternator...

you can shut the engine off...  unplug the voltage regulator...     start the engine... hook the volt meter to the battery... use a jumper wire to jump for a few seconds the F to the A... the charging voltage should almost instantly rise over 15 volts.. disconnect quick...   if it comes up to 15 .. it shows the alternator is working and that is probably has a wiring problem...





i will look around to see if i can find some proper charging system diagnostics ... so you can send them to the shop... what i have printed is proper...   and you or the shop can follow them...  as this is old tech.. most newer techs missed this ...


i will take a look around...  

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