Simple electronics questions

[BreckenridgeCruiser]

I have a simple question. I installed two new batteries this weekend, and removed a bunch of corrosion on the wires and ends. Changed all four terminal clamps.

I also took off a tap the PO put on the positive terminal of the low side battery (it was not connected to anything since he pulled the radio when he sold it to me). There is a ground wire attached to the negative terminal of the second battery that runs down past the starter and seems to be attached to the frame. I thought this was a ground for the tap, but then realized that this must be the second ground for the high side battery since it's NEG terminal is attached to the POS of the low side.

I guess I wanted to know a bit more about the flow of electricity here. Am I correct in assuming that for each battery, 12V comes back to the battery through the independent grounds? IF so, that means each battery brings back what it needs to stay 'even'? What would i do to my batteries if this High side ground was not attached?

I'm asking about flow because I have heard that I will have ground issues if I wire a second 12v ALTand battery to run accessories. If each battery will pull the 12v it needs then I would have 36V running through my ground being split between 3 batteries. What issues would I have?

[HZJ60 Guy]

Well, Im no electrical expert but it's nice to have a battery isolator if your going to be connecting multiple battiers. I have a samurai with two optimas. I have a 200 amp isolator and a big solonoid that allows me to turn the non starting battery on or off, but it's always being charged. That way if the starting battery goes dead the other isnt connected to the system. I can just flip a switch and add it to the system to start the car. Or, if Im winching a lot I can add that battery to the system for extra amps.

[BreckenridgeCruiser]

I forgot to mention that the truck is a 24v.

K

[lostmarbles]

Originally Posted by BreckenridgeCruiser

I forgot to mention that the truck is a 24v......

Yes. Obviously HZJ60guy assumed yours was 12V (like I easily could have too).

Originally Posted by BreckenridgeCruiser

......... Am I correct in assuming that for each battery, 12V comes back to the battery through the independent grounds? ...................

If each battery has an independant ground then I think you could be in BIG trouble. (I don't have a 24V cruiser so I'm just trying to work out what I THINK would happen.)

I think the alternator will be trying to charge a PAIR of 12V batteries IN SERIES (24V total) and yet you will be getting it to charge only the first one (by having that link between the two batteries "grounded"). Furthermore, you will be charging this first battery with 25V+ rather than 13V+.--------- So I think you'll be cooking that first battery while running the second one flat.

Even if you were to run 2 wires (both completely un-earthed) to a 12V load (such as a radio) from one of your batteries, the alternator will still try and dump 25+ volts across that load as far as I can see!!!!!!!!!!

[lostmarbles]

Originally Posted by HZJ60 Guy

Well, Im no electrical expert but it's nice to have a battery isolator if your going to be connecting multiple battiers. I have a samurai with two optimas. I have a 200 amp isolator and a big solonoid that allows me to turn the non starting battery on or off, but it's always being charged. That way if the starting battery goes dead the other isnt connected to the system. I can just flip a switch and add it to the system to start the car. Or, if Im winching a lot I can add that battery to the system for extra amps.

Wow. Must see if I can label things as well as that when I next post photos!!

I doubt it though. I'm too tight to buy any software. (I just use what came with my DELL computer.)

[roscoFJ73]

Originally Posted by lostmarbles

Wow. Must see if I can label things as well as that when I next post photos!!

I doubt it though. I'm too tight to buy any software. (I just use what came with my DELL computer.)

I downloaded Paint.net for free but you can use Paint that comes with Windows
You send the pic to Paint and choose the A symbol for lettering and you click on where you want to start typing names.
Then shut it down and it will ask if you want to save ,yes or no and click yes and it goes back to the pic file

[lostmarbles]

Originally Posted by roscoFJ73

I downloaded Paint.net for free but you can use Paint that comes with Windows
You send the pic to Paint and choose the A symbol for lettering and you click on where you want to start typing names.
Then shut it down and it will ask if you want to save ,yes or no and click yes and it goes back to the pic file

Thanks rosco. I've been doing that. - And I've been selecting "text box" for the labelling. But "Paint" doesn't seem to give me the choice of a "clear background" for the text boxes (which is what I need). I guess I need to just play with it a bit more to find that option. (But I hate computers. They're just a TOOL for me. Certainly not a HOBBY.)

[lostmarbles]

Originally Posted by lostmarbles

.......Even if you were to run 2 wires (both completely un-earthed) to a 12V load (such as a radio) from one of your batteries, the alternator will still try and dump 25+ volts across that load as far as I can see............

Oops. Could have suffered a bit of diarrhea here.

Even if the 2 separate unearthed wires do give your radio/whatever roughly 12V (not 100% how much the alternator will increase this), you still have the problem that most 12V accessories use the body of the item itself as the "negative wire". (So you'd have to have your radio installed in a fully-insulated holder.)

Nother Fing: I must have misunderstood. Surely you can't actually have each battery's negative terminal earthed separately. Because if you did, both sides of the second battery would be "to ground" and that battery would be effectively "shorted out".

[roscoFJ73]

Originally Posted by lostmarbles

Thanks rosco. I've been doing that. - And I've been selecting "text box" for the labelling. But "Paint" doesn't seem to give me the choice of a "clear background" for the text boxes (which is what I need). I guess I need to just play with it a bit more to find that option. (But I hate computers. They're just a TOOL for me. Certainly not a HOBBY.)

The paint.net does the clear boxes. So does paint if you can work it out. I got it once but can never remember how

[kim]

Originally Posted by BreckenridgeCruiser

I have a simple question. I installed two new batteries this weekend, and removed a bunch of corrosion on the wires and ends. Changed all four terminal clamps.

I also took off a tap the PO put on the positive terminal of the low side battery (it was not connected to anything since he pulled the radio when he sold it to me). There is a ground wire attached to the negative terminal of the second battery that runs down past the starter and seems to be attached to the frame. I thought this was a ground for the tap, but then realized that this must be the second ground for the high side battery since it's NEG terminal is attached to the POS of the low side.

Your batteries in a 24v system should be wired something like this;

low side ------------------ high side
+ - -----------------------> + -

The negative post from the low side should be connected to the positive post on the high side thus leaving you with a positive, 24v post and a negative which grounds body to engine where you have indicated.

Also, it is very good of you to remove ANY taps to the positive post of the high side battery as this will kill both batteries in a short period of time. A converter is a better option for 12 volt power or, as you mentioned, a third isolated battery with it's own 12v alternator.

[lostmarbles]

Originally Posted by kim

....should be wired something like this....
low side ------------------ high side
+ - -----------------------> + -

......The negative post from the low side should be connected to the positive post on the high side

Hi Kim. Now that I've gotten involved in this head-scrambler, I want to unscramble it (for my own benefit as much as for anyone else's) as much as I can.. What you have said above seems incompatible with what you say below:

thus leaving you with a positive, 24v post and a negative which grounds body to engine where you have indicated..........

Shouldn't you have drawn it instead like this (to get that 24V +Ve post)?:
{Frame}---{-Ve low-side-battery +Ve}----{-Ve high-side-battery +Ve}------to starter motor etc (where the "multiple dashes" represent cable/wiring connections).

(I'm assuming a 24V system is negative-earth just like a 12V system.)

Like you (if I am reading what you're saying correctly - which I may well NOT be), I see anything connecting onto that link between the two 12V batteries as a source of trouble because of the alternator being 24V and needing to charge both batteries IN SERIES.

PS. OK. I've lost sight of what Breckenridge said about his question being SIMPLE.

[BreckenridgeCruiser]

I'll try to make it more simple. Here's what happened.

I have the system set up right (like the diagram. earth to neg - Battery - pos to neg - Battery - pos to starter). but when I took off that wire off of the neg on the high side, there was sizzling when I tried to start it.

With the additional ground back to the high side, it starts and glows fine.

I have an idea. How do I check and make sure that I have the stock 24V starter? I wonder if the idiot I bought the truck from replaced the starter with a 12v. Just an idea. if so, then he would need the ground for the starter to work right, Correct?

[lostmarbles]

Originally Posted by BreckenridgeCruiser

.......I have the system set up right (like the diagram. earth to neg - Battery - pos to neg - Battery - pos to starter). but when I took off that wire off of the neg on the high side, there was sizzling when I tried to start it.

Hi there Breckenridge.
You obviously wouldn't try to start your engine with the "link between the two batteries" missing so I'm assuming the wire you say you removed must be that "mysterious extra ground wire" you refered to in your first post that "seems to be attached to the frame".

This is where you need to investigate!!!!

It can't be attached to the frame directly because that would mean your "low side" battery would be shorted out (grounded to earth both sides).

[quote] With the additional ground back to the high side, it starts and glows fine. [\quote]

As I say, - I can't see how that wire could be simply "an additional ground" (in the normal meaning of that term). There must be something between that wire and the frame. (Like a "diode device" that allows 12V to be drawn from the "high battery" without "shorting out" the "low battery"?]

...I have an idea. How do I check and make sure that I have the stock 24V starter? I wonder if the idiot I bought the truck from replaced the starter with a 12v. Just an idea. if so, then he would need the ground for the starter to work right, Correct?

I doubt the starter would be 12V because that would be silly. The main reason for your vehicle being 24V is "easier starting" (greater power output from the starter motor). But I do suspect you have at least one 12V "load" installed by the PO for that "mystery wire" to be there. (If it affects the starter - then perhaps it is a 12V starter solenoid? - Maybe the PO couldn't find a 24V replacement?--- This solenoid uses the small current that flows through your ignition to switch the BIG current that flows through your starter motor. At the same time, it engages the gearing between the starter motor and the "ring gear" on the engine flywheel..)

PS. I remember seeing a number of posts on MUD warning about the consequences of obtaining/using 12V off one battery in a 24V system. (Other owners of such vehicles should comment on this.)

[kim]

Let's try it this way; passenger side is on the left.

Harness <------(+) [ Battery ] (-)<---------(+) [ Battery ] (-)<-------(ground)--=


"I have the system set up right (like the diagram. earth to neg - Battery - pos to neg - Battery - pos to starter). but when I took off that wire off of the neg on the high side, there was sizzling when I tried to start it."

I swapped my batteries one time and I also had this sizzling because I didn't tighten the ground to the body near where it attaches to the high side negative terminal. The 'sizzling' was actually a grounding that took place between the throttle body cable and the cable mount on the firewall. It was arcing pretty good.

[lostmarbles]

Originally Posted by kim

........Let's try it this way; passenger side is on the left.
Harness <------(+) [ Battery ] (-)<---------(+) [ Battery ] (-)<-------(ground)--=................

Ta Kim. I have no trouble following this one.

................ 'sizzling' was actually a grounding that took place between the throttle body cable and the cable mount on the firewall...........

Uggggghhhh. Sounds nasty!



PS. I think my trouble arose from which battery is called "low-side" and which is called "high-side". I'm calling the one earthed to the frame "low-side" and the one connected to the starter motor (with the 24V output) "high side". (And we probably confused everyone more by talking of "first" and "second" batteries which is an extremely vague way of explaining which batteries we're referring to.)

[kim]

Originally Posted by lostmarbles

Ta Kim. I have no trouble following this one.



Uggggghhhh. Sounds nasty!



PS. I think my trouble arose from which battery is called "low-side" and which is called "high-side". I'm calling the one earthed to the frame "low-side" and the one connected to the starter motor (with the 24V output) "high side". (And we probably confused everyone more by talking of "first" and "second" batteries which is an extremely vague way of explaining which batteries we're referring to.)

From everything I have read on this subject, the low side battery is the one with the harness and the highside is grounded to the frame.

[lostmarbles]

Originally Posted by kim

From everything I have read on this subject, the low side battery is the one with the harness and the highside is grounded to the frame.

Ah. OK. Well my "logic" must be screwy then Kim. (Wouldn't be the first time by any means.)

I wonder why they label them that way?

It makes more sense to me for the battery whose positive terminal is 12V (with respect to the frame) to be called LOW and the one whose positive terminal is at 24V (with respect to the frame) to be called HIGH.

Well - At least people know which batteries I've been calling "low" and "high" now!

[Jim_Hbar]

The "low" battery is the one with it's negative post connected to ground, and let's call that "0" volts.
The + side of the "low" battery is 12v higher, so let's call that "+12" volts.
The "high" battery has it's negative post connected to the positive of the "low" battery, so it is also "+12" volts.
The + side of the "high" battery is 12v higher, so let's call that "+12+12" volts - "+24" volts for simplicity.

+24 is "higher" than 0, thus the reason for that being the "high" battery

The other end of that cable is NOT grounded.

If any wire is connecting the +12V node directly to ground, it is a dead short, and at least one of the following will happen;
The fuse in that line (if there is one) will instantly blow.
The wire will spontaneously melt, and act as a fuse.
The battery will melt and open, internally.
The posts will melt off of the battery
The low battery will blow up.
The cruiser will burn.
Or, if you are really lucky, and have very poor connections, you'll only kill the battery in a few short very exciting minutes...

You guys need to be more careful about "guessing" when dealing with this schmitt - a dead short on a battery is never good, and it will only cost you the battery - if you are lucky. The worst consequence is a battery that blows up in your face.

If you want/need a more technical answer, or want to compare credentials, PM me.

[lostmarbles]

Ta Jim_Hbar. You've made a very useful summary here. (Kim and me were just sorting out the correct terms to use.)

Since I like to "eavesdrop" on other peoples' conversations (view other peoples' threads) to gain knowledge, I like this form of "open discussion". This way, if someone disagrees, or feels they have something useful to add, they can just butt in and say it. The thread initiator can then sift through all the replies, and in doing so, can readily add more weight to certain posts than others.

Also I think it is important for "Newbies" to discover (via this sort of open-discussion) that there are no "know-it-alls".

[BreckenridgeCruiser]

Okay an update on the setup.

1) I was describing Low side as the 0 to 12v battery and high as the 12 to 24v battery. The harness is coming off of the POS high side and the ground is to the negative low side.

2) The starter is the original ND with the part number badge visible.

3) I will look at the Red/White wire off of the highside NEG terminal and find out where it goes tomorrow morning.

4) To confirm the wire setup:
Ground -> NEG (lowside) POS -> AND Red/White Wire -> NEG (highside) POS -> Harness

One thing.... where is the 0 volt ground (lowside) supposed to be connected? Mine is bolted to the battery tray... It struck me as odd when I saw it but it didn't make sense until the description of the arcing to achive ground.... What should my ground wire be attached to? Where is the stock location?

Thanks again to everyone for your continued help... This is really worrying me and I'm gald to be getting experinced help on this!

[lostmarbles]

Originally Posted by BreckenridgeCruiser

.... where is the 0 volt ground (lowside) supposed to be connected? Mine is bolted to the battery tray...

My 12V BJ40 had it bolted to the sheetmetal of the LH mudguard which is even worse. (This was how it left the factory apparently.)

I recently added another thick battery lead connecting that point to the engine itself (via a bolt head on the alloy timing cover). The result is that my BJ turns over faster now than ever before.

[kim]

Thanks for the clarification, Jim.

[BreckenridgeCruiser]

Okay, I traced the wire from the Highside NEG terminal. It WAS a second tap and not a ground. It was running to a wiring board that powered a trailer hitch. That would explain why, when I replaced a tail lamp bulb on the drivers side (the side past that block, the 24v bulb melted the plastic a little.

So, I then took off the tap and the truck ran fine.

I guess the sizzling i saw first was a bad ground cooking off some of the terminal cleaner or impurities.

Thanks to all for your help.

I Still have a few questions about testing Glowplugs and about where I should move the ground to make the system as strong as possible, But I'll make a new thread about those.

Kraig

[BreckenridgeCruiser]

I am a newbie to testing electircal systems and had a question about testing glow plug health.

I tested the voltage at the front cylinder glow plug and got a 20.5V reading for a second or two and then it dropped to around 10v. it sat there until the raly shut down the glow (around 10-15 seconds).

I read in the FSM that you also need to test the Amps getting to that plug. I have a cheap combination meter from Sears that has mulitple settings of what you want to read, V, Ohm, and Amps in different ranges. I have to admit I barely know how to use it properly.

What setting should I use and how should I place the sensors to get the right reading?

Where can I get a good set of not too expensive glow plugs?

Thanks