Amp draw??

[Bud Fox]

I had a short that I had to find in a car that I have. I disconnected the negative cable and put my gauge leads on the cable and the battery to find how many amps I was drawing. I am curious how to find an amp draw on a 24v system. Not having a problem but just wanted to know in case. THANKS IN ADVANCE

 

[Don M]

The voltage makes no difference. It works the same.



Don~

 

[BK]

In general Don is correct.



But there are some 24v systems that have a 12v sub system.

The engine starts and runs off of 24V, and things like the headlights and such are 24V.



But for things like radios and certain computer controlled things, there is a 12v sub system that can have it's own battery. In this case you want to just attach the current meter in the positive lead for each system.

 

[redram]

ummmm, the Dodge electrical system on a 5. 9L CTD 12 Valve or 24 valve is a 12 volt electrical system with two 12 volt batteries connected in parallel, not series.



Per my 96 Manual,

"Models equipped with the diesel engine option are equipped with two 12-volt batteries, connected in parallel (positive to positive/negative to negative). The secondary battery, on the passenger's side, is dedicated to providing current for the operation of the intake manifold air heater. The primary battery, on the driver's side, is dedicated to all other vehicle electrical requirements. In order to ensure accurate diagnostic results, these batteries must be disconnected from each other, as well as from the vehicle electrical system, when being tested. "



Connecting batteries in parallel does not increase the voltage, it increases the reserve amperage for high loads such as cold cranking, etc.



Connecting batteries in series would result in a 24 vdc system, ie two 12 vds batteries connecting one positive to one negative and measuring the voltage at the remaining positive and negative would result in a 24 vdc system.



Hope this helps.

 

[BK]

I'm wasn't talking about our Rams, I very much understand how and why are batteries are connected.



RedNuts' just asked a general "curious" question about 24V systems.

There are many different ones that I've worked on both in commercial and military vehicles.



Be aware that you will now start to see , if you haven't already, auto's going to a main 42Vdc system, with an aux 12V system.



Bob

 

[fest3er]

Originally posted by redram

... Per my 96 Manual,

"... The secondary battery, on the passenger's side, is dedicated to providing current for the operation of the intake manifold air heater. The primary battery, on the driver's side, is dedicated to all other vehicle electrical requirements. "

Huh. I'd love to meet the basket-weaving major who wrote that. With the batteries connected in parallel, they both batteries share the load equally.



Fest3er

 

[Don M]

Wrongo, the batteries are parallel. Manual a'int right.



Don~

 

[redram]

To Don M

Read the entire 'quote' from the manual. It clearly states that the batteries are connected in parallel. Not sure what you are referring to when you state that the manual is wrong?



I agree with fest3er though, how would you isolate one battery from the other for the different functions such as starter, heater grid, etc.....



Just trying to help by providing quotes from the manual, wasn't trying to start a war... . we've got that already ..... we just don't know where the battle line is and who the enemy is. !!!



God bless the USA!

 

[Don M]

The manual is, technically speaking, wrong. You can not dedicate different loads such as the grid heater, starter, etc to two batteries that are connected in parallel.

There is no way to isolate the current draw in a parallel connection without isolation modules to do so and the ram does not use them.



Don~

 

[BK]

In RedRam's defense , he quoted the manual, and it paraphrases the reasons "why" the second battery was put into the truck.

Two are needed to provided enough capacity to handle the truck's requirements.

Further more, they are in parrallel yes. . , but there is a difference in how to wire the batteries and where to place the load wires to try and distribute the load so the resistance between the batteries does not contribute to one battery seeing more than the other. If you to wire ALL of the load connections to say the battery on the drive's side and just brought over the "jumper" leads as they did to the second battery and thats all you did, you would see more dead driver side batteries that passanger side batteries.

The "jumper" cables that parrallel the battieries added a series resistance between the batteries AND will not promote great sharing. .

So wiring them in parrallel and distributing the load connections between batteries is the best comprimise to be made to help battery life and load current sharing..... which is what the FSM is trying to point out.



If you had a mission statement for a system design that said XYZ systems when failed cant not inhibit vehicle starting, there would a be a switch of sorts (whether electromechanical or solidstate) to discount the batteries and it's loads... and they would be isolated from the starting battery.

But since this isnt a vehicle with a battle fault condition to worry about... . it's wired together with some decent thought from the Dodge electrical engineers...



-Bob

 

[Don M]

BK

The quote clearly states the batteries are dedicated to different loads. Their words, not mine. What I said was the manual was "technically wrong" in my second post.



You can not dedicate loads on a parallel circuit without isolation.

You said it yourself in the theoretical specification you spoke of.

Distribution of the load is somewhat possible, but I have to say that some current is gonna flow from both batteries and there a'int no way around that one Baby.



Finally, everyone is on same page here and radram needs no defense if there was never an offense from me to begin with



Don~

 

[BK]

Don,

"Wrongo, the batteries are parallel. Manual a'int right. "





This is a real gray matter,,, in many ways... . no pun intended. .



... Your right that the batteries are on parrallel, but your wrong that the manual just isn't right. . your right that the Ram doesn't have an "isolation module", but it does have, based on the load currents, what can be a considerable resistance in the interconnecting cables and they will act to inhibit proper sharing for proper (optimum?, maybe a better word for some loads) operation of cetain loads... ... .



I think something was lost in the writing of it, knowing the system and how these thing happen (writing of manuals)...



I had said...

"... . manual, and it paraphrases the reasons "why" the second battery was put into the truck.

Two are needed to provided enough capacity to handle the truck's requirements... ... "'





Yes, in the parrallel connection some current flow will always flow from the other battery (if the EMF potentials are correct) if you were to put all the load wires onto one battery, but how much?... BUT Dodge didn't just put all the load wires on one battery. . since there are multiple voltage sources, dodge decided correctly, to distribute the load currents connections among the - voltage sources -.

I can raise the resistance between the points to where that 2nd battery will provide hardly any current to the loads on the other battery.

From my other email... .



"If you were to wire ALL of the load connections to say the battery on the drive's side and just brought over the "jumper" leads as they did to the second battery and thats all you did, you would see more dead driver side batteries that passanger side batteries"

Basic fact since the batteries will NOT share well at all if Dodge hadn't wired them as they have, the series resistance of the jumper wires will not allow proper sharing at these current levels.

And the one battey does not have the capacity to handle the load alone.



Maybe what the tech writer should have written to be 100% correct...



-Due to the required loads that your wonderfull Cummins has, Dodge has installed two batteries in your wonderfull Ram.

Since these load currents are VERY high and are drawn by different loads we've directly wired x,y, & z to battery 1 and a,b & c to battery 2. This will help extend battery life.



-Since these load current are very high and some loads are voltage dependant for proper operation, do not attempt to power these loads (run your truck) without having both batteries installed, connected properly and in good working condition. The wiring between the two batteries maynot provide enough conductivity to allow proper operation if both batteries are not installed. Modifing or changing connections my violate federal smog laws.





Or something like that...





Bob

 

[Don M]

I agree with everything you have posted.

I somewhat disagree on how the manual was written to say the loads were dedicated.

We both agree they are not dedicated. Somewhat load distributed yes. I was concerned someone could read into what the manual states and believe the loads to be dedicated to each battery. This could get some folks into a pickle, so to speak. Someone could, in theory disconnect the passenger side battery to do work on the grid heater after reading the word "dedicated" and still get current through the drivers side battery via the jumper wire.

That is why I stomped on the text of manual and called it "wrongo". It simply is not dedicated per definition and "technically incorrect".



Agreed?



I thought of you on L. I. yesterday during the mess. Looks like you are just fine. I'm glad to see that.



If people concentrated on the really important stuff in life, there would be a shortage of nice beaches like yours.



Don~

 

[BK]

Don,

Just to clarify,

-yup we basically agree.

-yup the manual wasn't written clearly, maybe we should polish what I wrote and they should replace their verbage with ours.

-yup I agree, since the batteries are hardwired in parrallel, your point about working on one load and needing to disconnect BOTH batteries and soo one is a correct one.



But ... those were not my real points, we also don't need someone thinking their truck my be ok with just one battery. .

-the loads "are" dedicated to each battery to promote distribution of loads to each battery since the batteries wont share well if you hap-hazzardly wire these big loads. . and the one battery can not handle the load well.

We've already seen what happens when the ESR of the batteries goes up, the alternator ripple is higher on the 12V buss and the computer's just don't like it.



Thanks for asking, I'm still running on a lot of nervous energy. I have one fiend that's one of NY finest and another thats a member of NY bravest... . don't know how they are...

Plus... my story is here, lack of morning appointments and circumstance kept us out of there:

https://www.turbodieselregister.com/forums/showthread.php?s=&threadid=24796

4th down from the top on the 1st page...

And to follow that up, our worries were confirmed about the bridges...

http://www.news12.com/CDA/Articles/View/0,2049,5-5-20106-242,00.html