battery

[fmfarrisjr]

I'm embarrassed to ask this. I have to replace the battery on my 1948 Dodge Custom. I took the 6 volt battery out --- forgetting to check if it was positive or negative ground. Can some one please advise if it is positive or negative ground?

 

[Plymouthy Adams]

if stock positive ground....hard to say who may or may not have changed the polarity over the years....check the size of battery clamp hole and orientation to ground..other checks can be made, like some will say check the polarity of coil...this is not a true factor as the car will run the same either polarity....before you get too involved...set it in as positive....while observing the ammeter, pull on headlights....no damage can be done doing this, if meter deflects to discharge....you got a winner...if you shows charge....you've been flipped.

Edited July 17, 2021 by Plymouthy Adams

[Los_Control]

I am just asking because not sure .... If it is a original + ground car, you hook the battery up this way.

Can you tell by the way the volt meter is working? ... if it is charging it is correct ... if it is discharging then you need to switch the battery connections?

 

Make sure the radio is not turned on, other then that I do not think anything would be hurt if installed backwards.

Or is there a better way to tell?

[maddmaxx1949]

Check the wire from your ignition coil to the distributor as well. The polarity of that wire should be the same as ground.

[Plymouthy Adams]

see.....this is not 100% valid....there is no guarantee that the unit was swapped to negative ground, system polarized and the ignition wires not flipped....the coil cares less....the point care less....as long as the path makes/breaks...you have secondary ignition.

[keithb7]

Positive and negative battery cable posts are different sizes. So are the related mounting clamps. Generic clamps may not be, however will be after they’ve been torqued tight. Check the sizing. Match each to the cable going to ground and to the starter.  Reinstall new battery so they are matched properly. 

[chrysler1941]

Here is another test.

Hook up battery. Turn on light and see what way amp needle points.. Charge = wrong 

[Sniper]

42 minutes ago, Plymouthy Adams said:

see.....this is not 100% valid....there is no guarantee that the unit was swapped to negative ground, system polarized and the ignition wires not flipped....the coil cares less....the point care less....as long as the path makes/breaks...you have secondary ignition.

 

This is not the complete issue.

 

Here's a very good write up on why coil polarity is important.

 

http://mgaguru.com/mgtech/ignition/ig104.htm

 

 

[Plymouthy Adams]

Sniper...my position and post I will stick with as the owner did not relate to the battery post why would he be concerned with the coil.  And as an added if he were to run it either polarity the odds are with the low power, low rpm engines that are further babied beyond belief in regard to rpm...he will never see any significant change in performance.   Well just what would he see....if you very observant of point wear....you will see the deposit of the metal transfer from one point surface on + to the opposite point surface on -    If we were talking performance I would have made an issue...but for a used car where things get changed over time and less than observant owners, I will stick with the statement  this is a 'care less' check.

[Sniper]

There are two mindset when fixing something.  One is to mind the small stuff, the other is "care less".

 

I am not of the latter camp.  If you fix the small stuff, the big stuff never happens because you took care of it when it was small.

 

If you are a "care less" type then the big stuff is always happening.

 

It's all in the details.

 

 

[Plymouthy Adams]

the care less statement on the battery you stripping off line like a 30 lb bass as you take the post out of context.   The care less is not that you should not take mind to correct...just that if it is not.....will not be noticed at the low rpm these cars operate and with as stated POs of this car over the years....unless you have ensured the polarity at the coil prior...it could not be relevant to actual polarity today.  

[Los_Control]

Just now, Plymouthy Adams said:

The care less is not that you should not take mind to correct...just that if it is not.....

Are you sure about this? .... If a + ground coil from new has been run in the 3600 rpm range, ran that way all of it's life ....

 

It is the side of the coil that the energy is coming in from .... A simple way to explain it, you are getting power from + or - on the coil ... electricity flows both ways.

I really do not think it matters if it is 6 volt, 12 volt ... ballast resistors do matter.

But if you switch polarity on any used coil, you will run into strange issues at higher rpm.  The coil is basically broke in to run one direction, when you swap polarity it is now running a different direction. .... while rpm matter and where you notice it. I would think the rpm is connected to the motor and not the coil.

[Plymouthy Adams]

the coil is a wire secondary and primary and a common internal connection separate of the case........what properties of the wire are being altered....and if this was valid.....when swapping from 6+ to 12- are you going to pull your wiring harness and reverse it?  Other ignition components exhibit the change in polarity per their wear pattern, we talking tune up expendables.

 

as an added......

 

the condenser will lose its ability to go to max charge over time based on the points resistance and why it is a must be a change item to obtain full spark again on tune up....

Edited July 17, 2021 by Plymouthy Adams

[chrysler1941]

Actually both Plymouthy Adams and Sniper are correct in different ways.

 

Coil will produce a spark with "wrong" polarity and engine will fire. It's not optimal, spark is weaker but our 80 years old engine with 5:1 compression and some 2500 RPM don't care. 

Stronger spark is needed at higher compression like in modern engines.

 

Now shake hands

[Sniper]

It's not like it's a major evolution to check or for that matter wire the coil correctly.

 

Sloppy is as sloppy does.

 

When I find someone has done this is makes me wonder what other things did they do wrong as well?

[Plymouthy Adams]

I agree Sniper and I took your post to heart that you strive to do right....which we all should do.  But as we all were not there, do not know the conditions as found...hard to say anything is 100%  but we should knowing try to make so when discovered.  Many folks here have cars they have no clue how it is wired.  Never verified this or that and why when something goes wrong they lost as Hogan's goat.  

[desoto1939]

6 hours ago, Plymouthy Adams said:

I agree Sniper and I took your post to heart that you strive to do right....which we all should do.  But as we all were not there, do not know the conditions as found...hard to say anything is 100%  but we should knowing try to make so when discovered.  Many folks here have cars they have no clue how it is wired.  Never verified this or that and why when something goes wrong they lost as Hogan's goat.  

Plymouthy: i have to agree 100% with your comment.  There are more people buying these old cars just to have an antique car. They have not done any homework on the car prior to buying it and most have not been exposed to the positive grounded cars. Most only know that the cars they are driving are negative so they assume that this is the only way to hook up the battery.  My first suggestion is to check with a car club and to get to know members and ask questions of the members then get familair with the car read up on the car, history then go make the purchase.

 

Lack of knowledge can really hurt you. Like buying a house without a home inspection. If no inspection then you find out whats wrong afteryou bought the home and then can not negotiate a price.

 

Rich Hartung

[keithb7]

I bought one of these old cars, just to have an antique car. I knew nothing about 6V or positive ground systems. I had a total lack of knowledge and had done no research done before buying.

 

Its been an awesome journey. I rely on friends and people here who are helpful. I’ve learned a ton. I’m still a hack.

Its sure been a fun journey. If i did my research in advance, would I have ever bought an old Mopar? I don’t know. I’m sure glad I just dove in.

[Sniper]

18 hours ago, Plymouthy Adams said:

I agree Sniper and I took your post to heart that you strive to do right....which we all should do.  But as we all were not there, do not know the conditions as found...hard to say anything is 100%  but we should knowing try to make so when discovered.  Many folks here have cars they have no clue how it is wired.  Never verified this or that and why when something goes wrong they lost as Hogan's goat.  

 

Agreed, as I once told my son, we are all ignorant of something.  No shame in that generally speaking.  However, the difference between stupidity and ignorance is that the stupid know they don't know but do it anyway.

 

As an example, on that Model A I posted about in the OT forum, when I ran into voltage on both sides of the coil with the key off, I stepped back and did some research rather than start pulling wires and such.  I had initially assumed someone messed up when they installed the new key switch.  Turns out I would have been wrong as Ford put the switch between the coil and the points rather than the coil and the battery.  Never seen that before and I did not assume I knew better.  Had I just jumped in and stared rewiring it as I thought it should be I would have compounded my ignorance with stupidity.  As it is, I saved myself some aggravation and learned some new things.

 

Now, to the point of coil polarity.  The primary and secondary normally share a common ground.  When you wire it backwards they no longer share that common ground and the secondary must now ground thru the primary windings which is why we see the issues mentioned.  Now when the ignition system is all new and shiny and perfectly adjusted you may not notice any problems.  But as plugs foul/wear, ignition wires get older, points start to get dirty, cap and rotor start to erode, etc it all takes something out of the spark.  You're already starting behind the 8 ball with a miswired coil.  Just fix it.

[Plymouthy Adams]

as I stated...and will say yet again......it is not a valid check point for polarity as it can be wrong from the get go and the car will run as either way.....I further said on these old cars it will not be noticed in low power these engine have.  I never once said not to make it correct.....again you continue to take me out of context.    This was an exercise to help the man make a battery orientation.....I also knew someone would say check the coil wire and thus the comment it may not be valid as we have no idea who may or may not have changed things about.   This person had no clue is his car was positive ground and based on that I knew he had no clue as to what the polarity of his coil should be.  

 

We both agree that the coil should be wired with proper polarity.....NOW....can we agree that we as individuals have never seen every car our forum members own and for certain we can say we have seen that the wires have been wrong on members cars in the past.  You seem to want to push home the correct coil polarity....and yes I agree....but unless you have seen his car.....how can you say what he has is correct.   You cannot, you can assume....when helping with a simple question keep the answer simple....whereas....it was....how to determine my polarity with the battery now out....battery post size is a major indicator at the battery.....current drain on the ammeter should confirm...but then again...I assumed he knew if his ammeter worked proper in the past....  

[Sniper]

You are taking me out of context.  Coil polarity should be observed regardless of ground polarity.  If you have positive ground then the positive terminal of the coil should be hooked to the points.  If you have negative ground then the negative side of the coil should be hooked to the points.  

 

NEVER once did I claim or imply the the coil wiring was a valid check for battery ground check, in fact the opposite is true. 

 

If someone has a question as to what is "wrong with me" don't run to PA as he claims, PM me.