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11DCV too much for automotive 12 volt starter
10

11DCV too much for automotive 12 volt starter

11DCV too much for automotive 12 volt starter

(OP)
I have heard that 12VDC auto starter batteries put in cars are designed to operate at 9 to 10 volts and that if a person puts too much battery in the car, the starter can go and not be covered under warranty. He said that the company said that cranking voltage of 11 volts was too high and his warranty was void. He then put the smaller recomended battery back in and he did not have any broken starters after that.
Is there any body that could confirm that starter motors are designed around 9 to 10 volts DC

Thanks

RE: 11DCV too much for automotive 12 volt starter

The starter may normally see something less than 12V, but I'm pretty sure it is rated to operate up to at least 12V if not above.

The thing about a starter motor is that it is not designed to run for very long - intermittent duty only.

But this story sounds like an urban legend to me.  But I don't design starter motors, so maybe I'm wrong.

RE: 11DCV too much for automotive 12 volt starter

Yes frankiee, and I also have a bridge in New York City that I'd like to sell you, along with some prime swamp land in Florida!

Seriously, if anything the LOWER voltage would be a problem because the current draw would be higher than normal, however 11V is well within the normal range for a 12VDC motor. Typical motor design specs are + or - 10% of nominal, but I believe that automotive starters have an even larger range, i.e. 9 - 14V. Go look at a battery tester that includes a voltage scale and you will see a green bar that signifies "normal" that typically ranges from 9 - 15VDC. Car battery FAQ link

If I had to guess, I'd say you had a bad ground connection, and the guy took advantage of the situation to sell you a new battery, knowing that in the process of changing the battery he could fix the connection problem without your noticing. It's a common trick in the auto repair industry that I learned as a teenager working in a service station.

You might also consider posting this question in the Automotive forum (click here to go there -> forum108 ). There are some great folks in there and they have a lot more experience in that specialty.

Eng-Tips: Help for your job, not for your homework  Read FAQ731-376

RE: 11DCV too much for automotive 12 volt starter

Not to mention voiding your tire warranty by driving in the summer with the winter air still in them.  Get real!  This guy got snookered twice; once for no warranty on the starter and then for a new battery he didn't need.

Blacksmith

RE: 11DCV too much for automotive 12 volt starter

2
Can I have the old battery? I'd love to have a 12 volt battery strong enough to damage a starter and I'm willing to take a chance on the starter.
yours

RE: 11DCV too much for automotive 12 volt starter

LOL  winky smile

Gunnar Englund
www.gke.org

RE: 11DCV too much for automotive 12 volt starter

Oh thats a good one, in fact its brightened up my week! Funnier than the guy who once insisted to me that by putting Helium in your car tyres you could go twice as fast. And its almost as funny as the time I saw a guy pour boiling hot water from a metal kettle onto a frozen car-wash pump in the middle of winter in an attempt to free it off. I thought it was a good idea at first, but then quickly realised it would have been an even better idea if he had isolated it first!! fortunatly he was ok, but man.....my ribs still hurt like mad when I picture him jumping and dancing about.
Frankiee? There is no truth in the statement at all. Standard car batteries all deliver 12v, what differs is the capacity, termed and measured in amp/hours. Fitting a higher capacity battery will do no harm to the starter-motor or car electrical system as they only draw what current they need to operate at 12v.

RE: 11DCV too much for automotive 12 volt starter

(OP)
Ok
I get the idea.
Just thought I would ask in case there was any truth to it.
Is that prime swamp land in Florida residential or commercial swamp land?
By the way, did anyone hear that it was so cold up in some of the lakes in Canada that the fish were growing hair on thier b..................... Well, I guess that story is one for the fishing forum.
Thanks people.

RE: 11DCV too much for automotive 12 volt starter

That could be an old 6 Volt battery car design.

RE: 11DCV too much for automotive 12 volt starter

Well, 9 - 10V would still not be normal for a 6V battery, so I doubt it.

Residential swamp land frankiee. All the commercial swamp has been bought by Disney for a new theme park called KatrinaLand. They're building a ride that flings you at 105MPH into a swamp infested with real alligators and snakes, then strands you there. Your only hope of survival is dependant on FEMA. It's scarier than the Haunted House.

Eng-Tips: Help for your job, not for your homework  Read FAQ731-376

RE: 11DCV too much for automotive 12 volt starter

"That could be an old 6 Volt battery car design."

Not really.   I drove a 1963 1200cc VW bug for 3 years with its original 6V starter motor, but with the rest of the electrical system converted to 12V.

With the increased voltage, that starter turned over really fast, resulting in a very fast starting engine, and very short and intermittent useage.  I doubt I turned the key to the start position for a even full second.

I also converted a 1955 Dodge Power wagon for a volunteer fire department with the 6v starter motor running at 12V.  The starter motor ran fine for the 5 years that I lived in that town without any other service.

Dan

RE: 11DCV too much for automotive 12 volt starter

Dang youngsters.  Nobody here old enough to remember 8 volt
batteries?  T'was the only solution for slow/difficult
starting in early big V8's.  Just tweak up the voltage
regulator a bit (you DO remember generators, don't you?),
and add a dropping resistor for the radio's vibrator.
Added benefit of better lighting. :)
I have, in the past, added batteries in parallel, run a
12v/24v starting system, and converted many 6V systems
to run on 12v, 12v systems to 24v, and NEVER changed the
starter unless it was faulty to begin with.
<als>

RE: 11DCV too much for automotive 12 volt starter

My Renault 10 had a whoopee! 10A generator.  I changed it to a 32A alternator in a Crescent City motel parking lot.. While on my honeymoon....

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: 11DCV too much for automotive 12 volt starter

Itsmoked:

Surely you could have thought of other things to occupy your time?

BK

RE: 11DCV too much for automotive 12 volt starter

LOL

That was a trip to remember..




R10 broke down 5 times.  Five unrelated, different things.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: 11DCV too much for automotive 12 volt starter

Keith, pity there wasn't an Eng-Tips Renault forum in those days.

RE: 11DCV too much for automotive 12 volt starter

Keith,

I wouldn't take that from UKpete, if I were you!

But, by the way, how is your ex-wife doing?

BK

RE: 11DCV too much for automotive 12 volt starter

You guys crack me up. lolo

We drove from Santa Cruz, CA up to Spokane to my Dads.

1) The oil line to the oil gauge broke and in 30 seconds
drained the oil pan all over the engine compartment(in back), in the middle of miles of orchards.

2) Then a ticking started that came and went.

3) The crank pulley sheared in half 40 miles from Spokane out in the middle of nowhere.  We had to hike 20 minutes to a wheat farmers house thru Mt. St Helen's ash to call my Dad.  He had to tow us to an ignoble greeting in town.

4) On the way out of town in Mosses Lake the knock came back so loud that we pulled into a Motel and spent an entire day pulling the top end off the engine.  Never found the problem... Put it back together.. No knock.

5) Got back down to 30 miles from Crescent City in the middle of the thick Redwoods and the generator seized.. at dusk.  Luckily my new bride figured out how to sting three sealed bearings on a bolt to replace the generator(4 the water pump) long enough to make it into town at 1 AM..  We took the only room we could find.  There was the biggest healthiest 8" shelf fungus growing out of the shower wall.. But that's another story.

We are still happily married. Where else could she find so much entertainment?


Keith Cress
Flamin Systems, Inc.- <http://www.flaminsystems.com>

RE: 11DCV too much for automotive 12 volt starter

I wonder.

BK

RE: 11DCV too much for automotive 12 volt starter

When I married we went on a tour of Scotland by train, nothing much happened though it did rain.

That sums me up really.

RE: 11DCV too much for automotive 12 volt starter

Tough marrying makes for a smooth marriage. Believe me...

Gunnar Englund
www.gke.org

RE: 11DCV too much for automotive 12 volt starter

Hi Pete,

I love Scotland - it has the finest mountain country in Britain, especially up to the far north-west. Even though it rains nine visits out ten, the tenth time will make it all worthwhile. It is kinda hard to keep that thought going during the other nine!

----------------------------------
  I don't suffer from insanity. I enjoy it...

RE: 11DCV too much for automotive 12 volt starter

Scotty, of course no slight on Scotland was intended!  It only rained occasionally and as we don't do proper walking it wasn't really a problem.  In the bits in between it was exceptional.  West is best I think (e.g. train journey Malaig to Glasgow via Fort William, one of my all-time favourites).

But Brighton's definitely warmer and less damp.

RE: 11DCV too much for automotive 12 volt starter

Gosh, I wonder what the OP thinks about the circuitous route this thread has taken:  golden opp to rib a frequent participant (who shows signs of addiction to eng-tips, as many of us do), marriage, Scotland.  What next?

Anywho, nothing to prevent scammers, such as those who dealt a mighty blow to the OP's wallet, from plying their trade.  (Oh, except knowledge.)

BK

RE: 11DCV too much for automotive 12 volt starter

Quote (itsmoked):

Never found the problem... Put it back together.. No knock.
Works for me every time. I even end up with extra parts when I'm done!

I spent my honeymoon at a beach resort on the Baja coast. Rented a car, and specifically asked for air conditioning, knowing it gets really hot in Baja. Got the car, drove off on a trip in the early AM to see the Bajia de Concepcion where the Grey Whales go for their honeymoons. When it warmed up, I tried the AC. Nothing but fan. Got out and looked under the hood, no belt to the compressor. Naturally, we had only 2 small water bottles with us (another mistake). New wife and I must have perspired 2 quarts of water each, spent the next day sick from dehydration. To top it off, a whale had beached and died a few days earlier, and the stench went on for miles and miles as we drove near and around the Bajia, but because of no AC we had to keep the windows down. Later found out that the belt had broken months ago and they didn't have the right size, so they sacrificed the AC. I yelled at the hotel rental car agent about why he failed to mention that earlier, and he said "But you can roll the windows down sir"! I learned that you must be very specific about what you ask for in Mexico, i.e. working AC, and no matter where you go outside of the hotel, take a case of water with you.

Eng-Tips: Help for your job, not for your homework  Read FAQ731-376

RE: 11DCV too much for automotive 12 volt starter

Mexican car rentals...  heheheh yeah...
Toyota van I rented in Mexico City had a rod knock that was so loud you had to shout over it.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: 11DCV too much for automotive 12 volt starter

Did anyone notice?

BK

RE: 11DCV too much for automotive 12 volt starter

All my boats have 6V starters and 12V batteries.  I haven't had a problem in 20 years.  Maybe they just made better starters in the 30's and 40's.  

RE: 11DCV too much for automotive 12 volt starter

'Fraid the gentleman is right about battery size and its all down to internal resistance.

If you get a large capacity battery say from a F250 truck and connect it into your Suzuki Swift with duff ignition and try to start it you will end up with one knackered starter. If the suzuki started on the key then you would get away with it but as soon as you start to try to draw significant current then the starter will fry its guts as its not designed to deal with what large battery can supply.

If your talking perfect world then it would fry but were not were talking large capacity heavy cranking duty batteries.

RE: 11DCV too much for automotive 12 volt starter

Did you run a systematic test on that Rugged?

Or is that what happened when you tried to make that "near death" Suzuki make a last spin?

I don't know what the nominal voltages of the two systems involved are, but my guess is that they are not the same. F250 winning hands down.

Gunnar Englund
www.gke.org

RE: 11DCV too much for automotive 12 volt starter

rugged,

Got to disagree. A few years ago, in one of our more creative moments, we jump started the site pickup with its 12V electrics by tapping off from six cells in the 110V turbine battery to give us a 12V source. The cells are each rated 2V / 1430AH and weigh about 200kg each. By the theory expounded earlier, the starter motor should have gone into meltdown.

Perhaps if the engine was totally siezed then some damage would arise, but it would be open to debate whether the motor shaft would shear off, the flywheel gear break, motor pinion strip its teeth, or the wiring would catch fire. But not on an engine free to rotate.

----------------------------------
  I don't suffer from insanity. I enjoy it...

RE: 11DCV too much for automotive 12 volt starter

Methinks much of the hoopla here involves the
difference between real starter motors and
toy starters such as are usually installed
in (smaller) motorcycles and some smaller cars.
I personally equate foreign and domestic small
car electronics with the IEC offerings in
motor control gear - adequate if used as
rated, but not nearly as robust as U.S. made
equivalents (SquareD vs. Siemens, for example).
<als>
P.S. you can leave such as Jag and BMW out of
the category, but Mercedes seems to now use
the same type of aluminum-housed crap.  And
probably some of today's domestics (dunno,
been out of it too long).

RE: 11DCV too much for automotive 12 volt starter

Seems like there a lot of speculation but little in real facts.  My copy of Chilton's repair manual states that a 12V starter draws typically 60 A to 120A while the voltage droops to 9 V.  The battery capacity is usually sized to provide some multiple of the starting current.  If you use the low current value, you get a battery ESR of 0.05 ohms for the battery, and a start resistance of 0.15 ohms.  Using the high value, you get a battery ESR of 0.025.  

If you use the low ESR battery on the smaller starter, you get about 68 A of starting current vs. the nominal 60 A, hardly a catastrophic event.  Doing it the other way, you'd wind up with 96 A starting current, less than nominal.

An even smaller starter would a correspondingly higher battery ESR.  Setting the battery ESR to zero results in 12V/9V=1.33x nominal starting current, which seems to be something that should be designed for in the starter motor, since a jump start migh be with a much larger capacity battery and resultant lower ESR.

TTFN



RE: 11DCV too much for automotive 12 volt starter

I must point out that there are two kinds of starter in common use now.
One is the old standby, series wound starter that has been with us for about a hundred years.
Some small motors such as lawn-mowers and outboard motors are using permanent magnet motors. The characteristics are quite different from series wound starters.
However, they will operate at a full 12 volts safely and, to my knowledge, are not used in automobiles.
The standard series starter is a series motor. Check the characteristics of a series motor. The faster it goes the less current it draws. The more voltage is applied the faster it goes. The starting surge is greater with higher voltage but is mostly disipated as voltage drop in the cables. I have seen a few starters fail because of low voltage but never because of over voltage.
I don't have any problem accepting that a failing starter
may well have drained a battery and the application of a good battery proved that the starter had failed. But, proving that a starter has failed is not the same as causing it to fail.
respectfully

RE: 11DCV too much for automotive 12 volt starter

waross you reminded me of what I was thinking - series wound motor - faster it spins more back emf and less current flow through the motor. That was what I was thinking on!

Now you have a reasonable battery hook it up when you try to start the battery voltage drops to say the crank voltage of 9v and the motor is cranking you get the current flow going through. Bigger battery and a goosed engine slower crank speed lower back emf and more juice going through kills the starter.

I guess its one of those things that no body is wrong and no body is right. A stronger battery = more juice.

Rugged

RE: 11DCV too much for automotive 12 volt starter

Hi skogsgurra
In North America The Suzuki will have a relatively small 12 volt battery. The F-250 will have one large 12 volt batterie or possibly 2 large 12 volt batteies in parallel, but both systems are 12 volts.
Cheers
Hi ruggedscot
When I get home, I have to change the ground cable on a truck I recently bought. The cable is too long and too small. If the (small diesel) engine doesn't start right away, it won't start at all. The cable overheats and the starter overheats and the cranking speed falls to almost stopped. At that point, with the overheated starter and partly drained battery, if I connect both of my jumper cables in parallel with the small battery cable the engine starts right up. Less cable resistance = more voltage at the starter.
There have been many starters damaged and destroyed by low voltage but almost none by high voltage. Most automotive starters will take double voltage safely for a year or more of normal starts.
respectfully

RE: 11DCV too much for automotive 12 volt starter

waross, I agree.  I think you are less likely to damage the motor with a higher voltage because it will start more quickly.  

Incidentally, back in the old days I could judge the condition of my battery by listening to the starter.  On my latest car when the battery was fading there was no warning - suddenly the electronics wouldn't let the starter even try.  I thought I had an electrical fault until my neighbour pointed out that was what happened on modern cars when the battery voltage was low.

Even more incidentally, just coming off the drawing board are cars with stop-start.  When the vehicle comes to a rest the engine automatically stops to save fuel, restarting when you touch the accelerator.  The integrated starter-alternator (usually mounted on the crankshaft between the engine and the gearbox) is more powerful and can turn the engine at over 1000rpm, starting it in about 200ms.  The old starters could only turn at about 300rpm and took over a second to start the engine.

RE: 11DCV too much for automotive 12 volt starter

Yes, and they usually have (or will have) a 42 V battery, too. I guess it would be a bad idea to connect that battery to a 12 V starter. So the old "Don't jump-start" warning gets a whole new meaning...

Gunnar Englund
www.gke.org

RE: 11DCV too much for automotive 12 volt starter

Naw skogs.. The 12 volt starter will just start the engine in 1ms!

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: 11DCV too much for automotive 12 volt starter

I am considering applying 24 volts to a 12VDC system on my boat.  The Perkins diesel is not turning over fast enough.  WAROSS posted this earlier (part of a response):
"I have used 24 volts on 12 volt starters many times. There are a couple of tricks to get 24 volts to the starter without getting 24 volts to the rest of the electrical system."

Can anyone tell me how to keep the 24 volts from getting to the rest of the system as mentioned here?  Thank you.

RE: 11DCV too much for automotive 12 volt starter

I was refering to connecting jumper cables.
I your case, I suggest using a Series-Parallel switch. These were used for many decades to start diesel engines in large trucks. The system in normal operation uses two 12 volt batteries in parallel. All the electrics are 12 volts. The charging system is 12 volts. When it's time to start, the Series-parallel switch reconnects one battery in series with the other to supply 24 volts to the starter. All the 12 volt loads and the charging system remain permanently connected to one battery.
This is proven and mature technology.
If you to build it yourself, use a second battery with a solenoid on each side of it. One solenoid connects the second battery in series with the first and the second solenoid connects the resulting 24 volts to the starter.
Two smaller relays (Suitable for charging current and/or load current) may then be used to connect the batteries in parallel for battery charging. I would suggest using an oil pressure switch to control the paralleling relays so as to avoid draining the batteries when the engine is not running. Don't forget to interlock the relays with the starting solenoids.
The Series-Parallel switch is the much preferred solution.
Respectfully

RE: 11DCV too much for automotive 12 volt starter

Boy ... I have a bad feeling here..  Creating 12/24 mixed voltage systems brings a headache(if not several) onto your boat.

My question would be why is the 12V starter not working as it should?  More likely you have a bad connection, bad battery, bad cables, bad starter solenoid, bad armature, or binding shaft.  Going the 24V route may(after a bunch of money and battery locating hassles), make your starter seem real peppy right up until it quits... 20 miles offshore...

Starting systems draw truly huge amounts of current, (I have bored everyone here with my starter's 1,600A draw), the tiniest amount of resistance ANYWHERE in your starting circuit can cause a sluggish starter.

This isn't some pumped up 474 with a blower and an Arnesson direct drive is it?

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: 11DCV too much for automotive 12 volt starter

Actually WAROSS, I was also referring to the usage of jumper cables although I shall consider employing your method here at a later date.  So, any direction you can give me towards doing this little maneuver with jumper cables?  Left alone, I was considering using the jumper cables to make a jumper between the two batteries Positive and Negative terminals (series) to attain 24 volts.  I am mostly concerned with ensuring I do not destroy other stuff in the process.  I have a brand new starter which is doing the same as the old.  It is having problems turning the engine over and maybe there is another problem that needs to be looked at.  There is just not enough "umph" in the two battery bank.  This was not always the problem and used to start up with the blip of the switch but now, the engine will turn but not fast enough and the positive connection on the starter gets very hot very fast which concerns me.  The old starter was doing the same and even started smoking.  I have a battery selector switch on the boat to employ #1, #2 or both batteries.  Maybe my switch is only using one battery when it says it is using two?  Bad switch?  One battery weak?  Bad ground?  Sure appreciate your help as I am going back over to the boat tonight.  I have GOT to get this thing started as hurrican season is upon me!  Thank you!

RE: 11DCV too much for automotive 12 volt starter

Hey Keith Cress: I did not see your posting relating to mine until I had replied a few minutes ago (please read).  Anyway, yes I am concerned and want to do this right but needing to move my boat in a hurry, so was considering the 24 volts.  The engine has started just fine in the past utilizing a two battery bank 12vdc system and since it has, I agree with you that there is another problem.  Maybe I can find some answers on here.

RE: 11DCV too much for automotive 12 volt starter

What size engine?

What type of boat?

By "move" you mean to a pull-out ramp?

Raw water cooled?

Have you checked the oil for water?

Put a voltmeter on the battery terminals directly on the battery connections NOT on the cable terminals and then have someone hit the starter just long enough to get a good reading 2-3 seconds max.

What reading do you get?

Next place the voltmeter leads directly on the starter. Put one on a solid bare spot like the big field screws on the side.  Place the other meter tip directly on the starter's actual power input bolt. Usually the one that the start solenoid outputs to the actual starter motor (talking GM style) (or on a Ford style, on the one big terminal).  Again have someone turn the key until you get a good read. 2-3sec max.

If these two readings vary by more than 1V you probably have connection problems.

You can hunt the connection problem by setting your voltmeter down to a 2 volt setting (or there abouts) and then placing the probes across each and every wire connection.

Example: Place one probe on the battery terminal and one on the cable connector bolted to the that same battery terminal.  You will come to some connection or the PERKO switch or something that will probably show most (90%) of the voltage difference between the original two readings. This would be the problem.

Possibilities: (not limited to)

Battery to terminals connections
Perko switch contacts (measured across switch terminals)
Cable swages (connector to cable)
Starter terminal to cable connections
Undersized cable/s (or secretly corroded to undersized)
Bad contacts inside starter solenoid
Bad engine ground cable/circuit

Let us know.
Good luck!

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: 11DCV too much for automotive 12 volt starter

Keith: This is a 1974 Irwin 32.5 CC Ketch rigged sailboat.  Perkins 4-108 diesel (40 hp I think) and no glow plugs, fresh water cooled.  What I mean by "move" the boat is that we are in hurricane season and I have to get this engine running ASAP to be prepared to move the boat elsewhere via the water ways as 13,000 pounds and 32.5 feet don't go on any trailer I have!  I have checked for water in the drain oil and there is none.  In fact there used to be a whole damn lot of it in there because water came up in the bilge and alomost covered the engine a few months back.  I drained her, pulled the atomizers and filled the holes and the crankcase with diesel fuel.  I then turned the engine over by hand and refilled again and let her sit a few days.  Then I sucked all the water/oil from the crankcase and let her spin with the atomizers still removed.  Long way of saying "there ain't no water in the oil anymore!".  Any way, the problem of difficulty in turning the engine over existed before any of this ever happened but was not always that way.  I will check all utilizing your tips and report back with my findings.

RE: 11DCV too much for automotive 12 volt starter

Nice craft the Irwin.



Hmmmm..  sea water into the starter...   That may end up being the problem but I'll wait to hear the results of your measurements.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: 11DCV too much for automotive 12 volt starter


"the positive connection to the starter gets real hot real fast"
This is the first problem to fix.
Take this cable off the starter and the other end (th battery), and check the crimp. You will have to either get a new cable, or remake the crimp, possibly by soldering. Not easy.
Regards, Ray

RE: 11DCV too much for automotive 12 volt starter

Excellent point rtronics!
I quickly jumped to my old days as a boat mechanic "recipe for a repair routine".  I'd check the voltage across that connection first! Just so I knew.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: 11DCV too much for automotive 12 volt starter

I went by the boat after work and inspected the battery cables leading to the battery selector switch.  Number one battery is the one that has been showing less voltage on the LED bar readout so I checked its cable first.  I did not even bother to put a volt meter on them at this point.  While the terminal end itself and connection to the battery and switch are good and clean, the wire in the cables itself has the green stuff all in it and my experience tells me that at least on a boat, this could continue on up the cable for its entire length.  I may cut off the cable a few inches back and see if it gets any better.  If so I plan on soldering on new terminals.  If not I plan on just replacing both the cables.  The ground appears to be made fast although that cable may be suspect as far as corrosion goes as with the positive cables.  More soon!

RE: 11DCV too much for automotive 12 volt starter

You asked about 24 volts with jumpers.
This only works with systems with seperate solenoids, like old Ford pickups. The jumper battery has to be isolated, that is not sharing a common ground or other connection.
With a negative ground system the negative jumper cable is connected to the "Hot" terminal of the solenoid. Take a deep breath and put the positive junper on to the starter side of the solenoid. The starter will start to crank as soon as you make contact. Expect a lot of sparks. 24 volts will arc more than 12 volts and as a result do damage quite quickly if allowed to persist.
This works great with pickups. I would use it on a lobster boat or a shrimp boat with a nice roomy engine room. Most of the pleasure crafty I have seen tend to have very cramped engine rooms. This method may not be a good idea in cramped quarters. If you have starter mounted solenoids, this method will not work.
Hi Keith;
re; "Boy ... I have a bad feeling here..  Creating 12/24 mixed voltage systems brings a headache(if not several) onto your boat."
The series parallel system has one battery, the charging system and all of the electrical equipment permanently connected. 12 volt system. The only time that there is 24 volts present is when the starter is energised and only the starter sees 24 volts. As soon as the starter is de-energised, the second battery is reconnected in parallel with the other battery to share the 12 volt load and for charging. The system was almost universal for 40 or 50 years on over the road diesel trucks. Cat engines, Cummins engines, Detroit diesels, and probably a lot more.
You will not be able to use your One, Two or Both switch. You may provide battery disconnect safety with a seperate battery disconnect switch for each battery.
Good points about checking the electrical system everyone. Especially checking the starters for water damage. The starting problems I most often run into are poor or discharged batteries, and or worn out engines that have to be cranked a lot faster than when the engine was new.
respectfully

respectfully

RE: 11DCV too much for automotive 12 volt starter

If it's not his wiring or a corroded starter it may well be the engine. Most engines that have been flooded with saltwater have serious problems within about a year.

I had one customer who had a boat that had the same sounding sluggish turnover.  I determined that it wasn't electrical. Might have been a 'weak' starter.  I finally tried turning over the 327cu-in by hand and could not even begin to budge it.  Then I stuck a wrench on the crankshaft.  I could barely eek it along.  Turned out it had lots of internal corrosion and bearing problems because the water cooled exhaust system(which uses raw water) had choked allowed water into the engine.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: 11DCV too much for automotive 12 volt starter

I think fsmyth's answer about the ruggedness of the starter is the only thing that can have some bearing on this. I have seen lawnmower starters with nylon gears on them so sticking a big battery onto this starter could cause the gear to be damaged. Not likely it would damage the motor itself though.

Waross talking about the shunt regulators in some motorcycles could explain why not to boost them, especially with the boosting vehicle running.

Dad has a tractor that was converted to 12V and has been so since before I was born. It's not used every day but it's still got a lot of starts on it. The starter motor has survived just fine but it did need the gear replaced.

A starter motor being damaged by applying 1 more volt to it....no very likely.

RE: 11DCV too much for automotive 12 volt starter

I agree with you itsmoked.
I think that DieselGrease has two problems.
One: What is causing the sluggish starting.
Two: How to get it going if it has to be moved out of the way of an approaching hurricane.
I think that both issues have been addressed.
respectfully

RE: 11DCV too much for automotive 12 volt starter

One joint to check that is frequently missed is the starter to engine connection which can be corroded and have a high resistance.  The larger starters have a ground terminal with a separate cable, but most smaller ones like this Perkins won't have that.  

RE: 11DCV too much for automotive 12 volt starter

Thank you WARoss and CCJersey.  Ok, I once more spent some time at the boat on the problem.  I mentioned earlier that I had a battery switch (with L.E.D. bar type readout voltage indicator on panel) for a 2 battery bank arrangement.  There are four positions on the switch which may be selected: Battery 1, Battery 2, Both or Off. I had been noticing that even after a full charge to both batteries, that battery #2 when selected would display good voltage on the readout, when BOTH selected the readout is the same as when just #2 is selected,  but when selecting battery #1 the reading is very weak, and yet both batteries would show a full charge when load tested independently.  I also checked the voltage with a meter at the back of the battery selector switch with the same results thinking perhaps a few of the tiny L.E.D. lights may have gone bad on the #1 side of the voltage indicator but the results were the same.  I then disconnected the batteries and switched them around.  Same results!!: Position #1=little or no reading, position #2=strong reading, position BOTH=same as #2 position reading.  I guess it would be easy at this point to say that I have a bad battery selector switch but easy there, not so quick.  I know I have two good batteries and the cables from the batteries to the switch are good and with good connections at both ends.  I did notice when inspecting the battery cable leading from the selector switch to the starter that the connection at the starter should be re made as it appears corroded, but would this cause what I mentioned above with #1 reading weaker than #2 when both batteries are good?  I am beginning to think that maybe even the connections at the back of the switch are wrong.  The idea is to employ two batteries to assist in the starting of the motor.  Here is how the wires are connected at the back of the switch: Position #2 goes to starter, postion BOTH goes to battery #2 and position #1 goes to battery #1.  Dieselgrease weary now.  Dieselgrease want to rest or burn boat down to water.  Help.    

RE: 11DCV too much for automotive 12 volt starter

Do not burn boat to water line while at dock.. Expenses can mount quickly..

Switch should be hooked up:

Both => starter
#2 => #2 battery
#1 => #1 battery

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: 11DCV too much for automotive 12 volt starter

Keith: Yes it makes more sense to me that the switch should be wired in as you said.  I will try that, thank you.  By the way, how long have you had your Irwin?

RE: 11DCV too much for automotive 12 volt starter

I wish! I had a sailboat.. The last one I had sat mostly in my driveway. It was an International Tempest.  A rocket ship that needed a lot of work and was a hassle to launch and recover.

I stuck that Irwin picture in only for our fellow poster's edification.

Your present switch wiring explains a lot of your indicator problems.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: 11DCV too much for automotive 12 volt starter

Keith: Your "fellow poster's" name must be Jake Cinnamon?  Yeah I am going to change the wiring on that switch and make sure I have two batteries working "together" on 12vdc to crank that bad boy before I go and hit it with 24.  I never had to put 24 on it before and don't want to have to resort to that unless necessary.  I mentioned approaching "hurricane" in another posting only because where I live and the damage I sustained last year.  If another comes I am moving the boat a bit inland for a couple of days.

RE: 11DCV too much for automotive 12 volt starter

You can make sure you have the switch right by switching to a certain battery, and lifting the ground connection of the other one and see what you have left at the indicator panel and to the starter.  If lifting the ground kills the supply, either another bad connection or something still wired up wrong, or a bad battery.  

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