Three Group 31S batteries, all connected parallel = HOTs to HOTs and NEGs to NEGs = 12 Volts.

Truck had been fine, with no symptoms of battery trouble.

Truck sat for 40 hours; then, when I tried to start it, it barely had juice enough to click the relay.

Checked voltage, before doing anything else = 8.4 Volts.

I disconnected all three batteries from each other.

One showed 8.2, one was 9.4, and the other was 10.4 volts.

I hooked the charger to one battery for two hours at 2 amps and thirty minutes at 10 amps; after charging, this battery was showing 12.4 volts.

While the battery was charging, all connections were cleaned and examined = good as new.

After charging, this battery was connected by itself and would start the truck easily.

Hooked the other two batteries to the truck and let it run about an hour.

Voltage for all three was showing 12.4.

Voltage while running was showing 13.8.

Let truck sit for 37 hours.

Now, deader than it was at 6.3 volts.

One thing I did notice was, when I connected the positive cable from the rear two batteries to the one under the hood, sparks flew.

I have never had that happen before.

The rear two batteries were connected to each other and grounded; but, the main HOT cable from them was not yet connected.

The other battery was connected both HOT and ground.

When I touched the HOT from the rears to the other battery is when the sparking occured.

The engine was not running during this.

I assume one of the three batteries is shorting out; how do I determine which one ??

To work with, I have both a digital and analog voltmeters, a small 2-10-55 amp charger, and a load-tester/volt-meter.

Thanks.

 

Try disconnecting the rear 2 from each other and hooking them to the main one at a time, just use caution. Is it sparking a lot, or just like if you were messing with a loose ground?

 

I would disconnect each battery, charge it and let it sit disconnected. One will drop power (due to the internal short)

or pull all three batteries and take them to autozone.

 

Go get a cheap hydrometer battery tester so you can test each cell. You will probably find the bad cell quickly. I carry one in the fiver at all times and periodically test the cells to see if I need to set the inverter/charger to equalizing charge. Amazing what a difference it will make. You might find doing that to the bad one will shape it up, but 12v'ers are not real happy with equalizing - - you will not do it very many times like in a true deep cycle. What you are experiencing is one of the nice parts of batteries in parallel. And, keep doing what you are doing (allowing the bad one to take the other two down that far) and you will quickly be buying three batteries.

Oh, you should always connect the negative ground last when putting in batteries.

Bob

 

Not a big shower of sparks, just about what would be when connecting a cable when a light, or something, is already on.

I dis-connected the single forward battery, charged it, cranked the truck, and let it run a while.

I have the charger on the rear pair and will leave it that way for a while.

I will leave the rear ones not connected, and see what I have in the morning.



FiverBob,
What is an INVERTER/CHARGER and what is meant by EQUALIZING CHARGE ??

Thanks.

 

I would say that you have at least one battery with a failed cell, and you get a spark when hooking them in parallel now because their voltages are different. Their voltages would have been similar when they were all in good condition.

It sounds like the truck attempting to charge the batteries when running. You might also take an amp meter reading to make sure nothing in the truck is drawing power when it’s shut off.

Although equalizing a bank of batteries can be helpful, from the voltages you gave I think they are beyond hope.

A set of batteries in parallel will perform best and last longer if they are all of the same type, amp hour capacity, and similar age. If it were me, I’d replace the set.

 

My fifth wheel has a 2000w inverter to use battery voltage to produce 120v AC. It also replaces the converter (battery charger) for the rig by being what they commonly refer to as a "smart charger". It charges at varying voltages depending on the condition of the batteries and monitors charging temperature also. One setting in it is "equalize" which uses higher than normal charging voltage which cannot be done real often - - it does move some material off the plates to rejuvinate them. Definitely not something you do often on a starting battery - - not a whole lot of plate in the first place. You can buy battery chargers that have the ability to produce equalizing charging.

Your first problem is find the battery and the cell that is giving you a problem. Then, hope your other batteries are still OK. The information given you by Jeff is important. Parallel batteries must be very similar in every way or the weakest will take out the other(s).

Bob

 

This is what I did and, with only one charger, took some time.


I charged each of all three batteries.

After about a 24-hour rest, two showed a shade over 12-V, and the third was down to 4.1-Volts = obviously the bad one.

I slid the harness from it and sent it to the soap-factory; another mule has taken it's place.

Thanks for all the input.

I intend to procure a hydrometer-thingie in the near future.


Also, I have read numerous references, on mostly marine sites, to using fuses between parallel batteries, such that should one battery short itself out, that fuse would blow, thus protecting the remaining batteries and saving their charge.

I have had no success finding out just where and what type fuse I would need for this.

 

Bob,
What brand unit do you have? does it desulphate or just equalize?

My Chevy 6.2 used to cook batteries all the time, 2 batteries in parallel if one has a shorted cell then the 12 volt battery will be trying to charge a 10 volt battery.

Remember for every cell you loose you drop 2 volts.

Hooked the other two batteries to the truck and let it run about an hour.

Voltage for all three was showing 12.4.

If the engine had just been running the batteries should be higher than 12.4 volts, at least 13 volts
My alternator charges at 15.0 volts and the batteries are closer to 14.0 volts until the surface charge dissipates.

I have had no success finding out just where and what type fuse I would need for this.

Use a Separator to parallel the batteries and they will automatically disconnect when the engine is off.

Jim

 

BK, back to your original post...

what you describe is the symptoms of a "short to ground". In other words , one of the trucks circuits has develped a short, draining the batterys at rest. In this situation, having three batterys is increasing amperage, and wont stop them from draining.

Take and disconnet the ground wire from the batterys. Attach a test light between your Neg post and the truck chassis. If you have any light at all then you have an open circuit. Make sure all "auto" lights such as the under hood light are disconnected or off before this test.
If you have an open circuit, then the next step is to start pulling fuses one by one until you can isolate which circuit it is.. a real PITA...
then its tracing the wiring on that circuit until you find the short...

It sounds much much simpler than it is, thisis one of the hardest electical issues to correct( per my ASE Electrical test phamplet)... can drive you nuts trying to track it down. The easy fix is a isolater switch to cut off the battery when not in use, but that doesnt solve the short problem..

Hope this helps, goodluck!

 

Jim, I have a Prosine 2000w unit. Love it. It has the digital control panel readout inside the fiver so I can monitor AC input voltage and frequency, how much AC current the inverter is supplying when running, current drain on the batteries when using them, charging voltage and current, it will not activate on reverse polarity AC input - - cool device.

I thought equalizing was desulphating. I can watch the readout, it will monitor the voltage and battery resistance, then apply a higher than normal charge voltage that will go as high as needed up to 17.? volts. Then, as it becomes happy, the voltage starts coming back down. When it tells me it is completed, a readout with the hydrometer has all cells floating equal. It then holds a charge quite a bit longer. I have only done this twice in the 5 years I have had these batteries. Dry camping for a couple weeks at a time is rough on them but they have held up great. Another great thing about charging with the smart charge technology is the charger backs off when the batteries are charged. This prevents overcharging and boiling off the water which occurs when plugged in for several days. This is my third rig with an inverter/charger - - wouldn't be without one.

Bob

 

Please show me a picture of this "separator" and go some further into detail as to what and how it does.

Thanks.


Chrisreyn,

Thanks for educating me on how to track down a short; as, I have another vehicle that, if I don't dis-connect a cable, will be dead in a couple of days; but, if I dis-connect a cable, it is hot as a firecracker, after weeks of sitting un-used.

I believe the problem with my truck was the bad battery drawing the others down.

Since I removed it, so far so good.

 

Be VERY careful when creating sparks near a battery. Especially if it has removable caps and they are off. The hydrogen and oxygen given off from the battery is very explosive. I blew one up once and got acid all over me and ruined the battery.

Edwin

 

Good point. I also make sure I have some eye protection on.

 

BK,
This is the separator I am using in my truck; actually I have 2 of them.
When they are connected properly, your auxiliary battery is not connected into the charging system until the main battery reaches 13-13.5 volts and then the relay will engage and combine them together.

Now when you turn off the engine or your alternator fails as soon as the voltage reaches 12.4-12.9 volts then the battery will disconnect from the charging circuit.

Everything is automatic BUT you can wire a momentary switch for a BOOST to parallel them for starting if your main battery goes dead, or you can connect it for starter assist, which will parallel them every time you crank the engine.

http://members.***.net/egiandomenico...01314-100A.pdf

I have mine set up with 2 momentary switches so I can add up to 2 auxiliary batteries to start my engine should the main fail. I have used this feature several times.

By pushing 1 or 2 switches I can start with 1000, 2000, or 4000 amps of current. This is by using 2 group 31’s and an 8-D battery in the back.

When you have this much current, you MUST have good cables and impeccable wiring habits, A simple short circuit could be devastating with this much current.
All the cables must be inside loom and fastened securely.

When I was a diesel mechanic for the county we had some coaches that had 4) 8-D batteries on a slide out tray, they were all in parallel. Another mechanic was disconnecting the battery when his 1/2" Craftsmen ratchet wrench hit the positive lug I remember a flash of light and the entire wrench handle lit up white-hot before it melted, it was almost instantaneously.

Another thing people must remember is to remove all of their jewelry, watches and especially their RING.
This was a public service announcement.

On my fender I have a 1/2 X 9/16 wrench and a pair of Klein High Leverage cable cutters stuck to the fender next to the battery using rare earth magnets so I can cut the cable in an emergency.

http://www.mytoolstore.com/klein/j63050.html

I have never had to cut one of my battery cables yet but I have cut many at accident scenes.

Back to the separator, they come in both 100 amp and 200 amp also un-directional and bi-directional.

With the bi-directional unit you can charge the battery bank from the auxiliary side with an inverter/battery charger or generator as if you were in an RV.

The separator will cost about $60.00 and is worth every penny. They also use them in the cars with the thumper stereos to charge the batteries in the trunk and I have found them on E-bay, if you buy them there be sure they will guarantee it is working first.
The 100-amp unit uses the same relay we have on out grid heaters.

Another thing that will kill your battery is if it is dirty or wet on the top, keep it clean using baking soda and water and be careful not to let it get inside the cells.

To test if the battery is discharging through the top, take a test light and clip the ground to the (-) then with the probe move it across the top of the battery from (-) to the (+) if it is leaking the light will light up the closer you get to the (+) wash it of and it will go away.

Jim