Urgent Help ! - Grounding of 2 Engine Starting Batteries Connected In Series

If they are in series than only one terminal would be grounded.
E.G if its a negative earth the connections would go:-

Ground connected to negative of battery1.
Positive of battery1 joined to negative of battery2
Positive of battery2 which then connects to you load (starter motor?) postive terminal (via switch).
Load negative trminal will be connected to ground completeing the circuit.
Del

Hi Guys,

I just did the grounding of the battery cables and sadly there is a short circuit.

I have connected the positive terminal of battery 1 to the motor then the negative terminal of battery 1 to positive terminal of battery 2 and then the negative terminal of battery 2 to the battery disconnect switch.

After which , i connected the negative terminal of battery 2 to ground. But this causes a massive short circuit.

Could it be because my load is not grounded?

Therefore, the current is short circuited to ground?

What is the application? Could it be that you have an old system using a positive ground, and there's still another ground connection in the system?

Also, check where the other (non-battery) side of the disconnect switch is wired to.

Meter ohms between the wire that has been disconnected from the battery positive terminal and ground. Remove all downstream connections between this wire and ground before re-energising the circuit.

For a positive-ground circuit, meter the negative wire instead. See Fredski's sketch below.

From your description it appears that you connected starting relay at the negative battery pole. Although you may have already fried alternators, please stop now before you fry everything and seek professional electrician help, because I don't think you understand basics. If you don't stop now, other professional help type is on it's way. S.M.

That statement only holds true for a negative grounding system. Putting the positive end to the chassis as its common ground will be true for a positively grounded system.

It is very common to encounter a positively grounded system in the olden days, where the positive terminal of the battery were tied down to the chassis of the vehicles and used as the common ground.

Just to clarify what Del said (which is perfectly correct) - the "ground" here need not be (and usually isn't) the same as the electrical safety ground used in mains power systems. It would typically just be the vehicle chassis.

Also, there is often a (high current-carrying capacity) wire connecting the load negative to the battery negative, rather than relying only on the connection through the chassis. This is in addition to the ground connection.

Hi, I think what the DEL said is right.you can do like that and another things you should have sure that starting motor is ok.just take the multimeter and check the short circuit of motor and go proceed acoording to del for connecting the batteries in series.no need to ground the batteries just connect the batteries in series to get the required dc voltage.

thanking you.

Hi.

This is exactly what i did.

But there was a short circuit at the negative terminal when i connected this way.

what could be the reason that cause this?

Lets make sure we're talking about the same thing. What EXACTLY do you mean by "short circuit"? If any load is in the circuit, like a door lamp, radio, etc. you'll see a spark when you complete the circuit.

Agreed - and this is even more apparent if the load is a starter motor!

When i completed the circuit, there is a spark at the negative terminal of the battery where the grounding cable is connected to...

Tell me what the LAST thing you connected to complete the circuit was. And where EXACTLY did you see the spark? I wish I had a picture of this. If the "spark" came from anywhere besides the last connection being made you have a bad connection at that spark. Possibly a faulty/grounded part.

Ok.

The last thing i did was to connect the grounding cable from ground to negative terminal and there was spark at the negative terminal of the battery.

Anyway , I had did a check with my multimeter and i realised that my system is positively-earthed.

Is that normal?

A positive ground is not abnormal on older vehicles. How old is the one you are working on? I collect antique fire apparatus, and some are positive ground (and some are negative ground.) Most newer vehicles are negative ground from the factory, but not the old stuff.

Check that disconnect too. It is normally put in the hot wire, but could be put in the ground wire. If someone added the disconnect to a positive ground vehicle, he may have put it in the "wrong" place, and thus confused you!

Trace all wires if you haven't already.

Erm.

I am using the batteries on a Caterpillar genset which is manufactured in 2010.

I would define the spark as a big spark.

The cable lug instantly burnt off upon contact and the battery terminal melted too...

STOP.

There is your answer; "Anyway , I had did a check with my multimeter and i realised that my system is positively-earthed."

Your system is polarized with a positive grounded system. Although the batteries are properly connected in a series manner, the final two + and - resulting terminals should be connected as follows;

The positive end of your battery should be the one connected to the ground and the Negative end direct to the load (starter motor).

To avoid any further damage, make sure to check and verify that the positive terminals of any other electrical loads are also grounded like your starter motor - meaning you have a "positive ground" electrical system in place.

Just how big is this "spark?" A little thing can be a light bulb, or maybe the vehicle computer if it's new enough. A big spark that makes you jump into next week may be a short or maybe the starter if the start button/switch/relay is stuck.

The advice to get a competent electrician is good.

Sure sounds like you are connecting the final connection point while a large load is engaged. As suggested above, look to see that you have a switch/starter button or such that will make the final connection, not the ground cable being the final connection.

If you need 24 volts to start the engine, you're in over your head right now. STOP! You're looking at possible injury from exploding acid batteries, fire, and massive expense for fried equipment in milliseconds!

When you are grounding batteries the negative goes to the engine block & the live to the solenoid on the starter, when you operate the solenoid the circuit is made,but make sure you connect the batteries correctly:- Neg to block, Pos to Neg of second battery, Pos to solenoid or switching panel which ever way it's wired.

You are unqualified to work on this problem (already mentioned by someone). It could get extremely dangerous for you. Go and get a professional before you regret it for the rest of your life.....

Batteries of these types are a huge source of energy when shorted out!!

I will echo the sentiments of others. Don't do this work yourself. You should not be working on a Caterpillar genset, all of which produce lethal voltages and can create arc blast hazards as well.

A qualified individual will be certain how to hook up a battery, will be certain about the the machine's having negative or positive ground, and will not encounter large sparks when hooking things up. A qualified individual will ordinarily ensure that there is no sparking near the battery upon hookup, by making the final connection away from the battery (such as at the machine end of the grounding cable, rather than at the battery end. ) A qualified individual would be able to supply a schematic of what he is attempting to do.

You are lucky that the batteries did not explode.