6 volt hi amp load test?

[Jerry]

Had problem with my E-car. 1985 Ford ranger with 20 six volt golf car batteries.

A while back one of the batteries exploded during the night. My charger was on as usual. The metal braket used to hold the batteries in place was the problem. Some curozion built up bad enough to cause a carbom track to arch and ignite one battery.

I removed the metal braket, took all the batteries out a scrubed em up clean, replaced the bad battery, even installed new and bigger jumper cables. This is a 120 volt system.

Now however theres something wrong. After a full charge the voltage drops off real fast. Normal driving leaving the house fully charged, start out at 144 volt get to work at 126 volts. Now its leave home at 140  volts get to work 80 volt and smell an overcharged battery real bad.

I've done voltage checks while charging, after resting overnight, SG test with no battery under 1250 most 1275 some 1300, load tested each battery at 60 amps they all check fiarly close.

So now I'm thinking of a big heay load tester to seperate the real workers form the lazys.

300 to 400 amps each to isolate the weak one or ones.

I've got a 400 amp aircraft relay. I'm thinking for the load, I've got a 240 volt 3500 watt heater eliment. Its about 36" long. I'll cut it up in a bunch of 2" lignths and perelell as many as I can make with some 1/4"X2" copper bars about 2ft long. Then use some of the 4/0 cables I've left over from the new jumper wire and use the big 4/0 ring tungue conectors for a good solid bolt on test. I also have a 400 amp, amp meter and shunt and a stop watch.

This testing will take some time do to the bolt on for each battery but so far my other testing has not pointed out the bad batt or batts. Its makin me crazy I gotta try some thing.

Any sogjestions are very welcome.

Unhappy EV driver.

                           JK TAS JErry

[crashk6]

I hate to tell you but the likely reason your smelling overcharged batts is due to the fact the charger is charging the older batteries to the same level as the new one... and as they are older their actual capacity is slightly less than the new one, more charging will eventually boil them to death. When something catstrophic like that happens in a series string bank it's time to replace the whole set. Now of course the remaining older bats can simply be reconfigured and given a new job as the are not truly bad.

I would also examine the charger and recalibrate it. I may have minor electrical damage contributing to an overcharge state.

Watch that corrosion, it is to an EV what dirty oil is to an ICE vehicle.

I'm just glad you didn't lose the truck to fire!

--

crashK6

[ghurd]

Bummer about the truck.

Silly idea?  Get 20 of those Harbor Freight $3 on-sale meters, one for each battery.

Put them on the passenger seat and watch which ones are acting strange while driving.

Maybe only 10 and run half the test one day, other half the next.

Those 99 cent red and green felt battery washers... they work great!

No idea why.  But they do.

G-

[pwr]

1.  Never mix new batteries with old batteries.  That said, you can do so as long as you realize and solve the real problem, which is;
   
2.  The more cells operated in series, the more likely you will end up with one or more cells which won't accept a charge while the rest of them need it.  The cells which won't accept a charge (probably they are lower in capacity and full charged), will drop a disportionate amount of the overal voltage.  This aggravates the situation, and eventually those cells will overheat, catch on fire, kaboom.
   
   

Forget load testing as a way to test the cells.  Its a whole lot simpler.  Charge the batteries until the charger thinks they are full.  At that time, measure the voltage of the individual batteries.  The ones which have much higher voltage than the rest are the culprits.

How do you mix old and new batteries.  First, charge them for 24 hours in parallel.  Then disconnect them for another 24 hours and measure their voltage.  Those which aren't close to the majority need to be replaced.  Even after doing this you will not get full life from the batteries, but if you stay alert for unequal voltages while charging you'll be able to squeeze some extra life for your dollars.

[Jerry]

Thanks every one for your help. I apreciate all the input.

However I goofed when reporting the egg smell. It dose not happen during charging.

IT only happens while driving and at the end of my normal daily trip. 80 volts from 140 volts.

NO problems at all while charging. I charge at a rate of, Start charge amps 15 and morning end charge around 5 amps.

So I have concluded the problem only exsists under heavy load.

Therefor build a heavy load tester to find the bad bat or batts?

Thanks again guys. I'll build the big load tester and report back my results.

                        JK TAS Jerry

[Drives]

Similar to some of the ideas mentioned here, why don't you make a bunch of high current shunts from some smaller diameter copper wire. (See past posts, I'm guessing 1 foot of #1 AWG?).  You have a good facility at your shop to check calibration of each one.  Then install the shunts in series with each battery.  Run the current signal wires off the shunts (milivolt level signals) in multipair telephone wire (for example) up to the cab.  Terminate on a multi screw terminal block.  Then run the voltage sensing wires off each battery up to the cab the same way.  Once you have labeled the signal wires to indicate which battery voltage and current, you will be able to have someone drive the truck while you use you meter to monitor each battery.  

Thus your truck will be your heavy load test, and you will be able to determine exactly what is happening under heavy load.

Hope this helps.

 

[TomW]

Dean & Jerry;

Add some switches and meters and he could just monitor them on the fly any time. I will refrain from suggesting a datalogger for brevity.

One of those stereo speaker switching panels might be a way to switch among the battery sense wires and a guy in the car audio biz might have one of those in the boneyard ;=>

Cheers.

TomW

[RP]

Speaking of heavy wire...  Consider this:

The resistance of 12 gauge wire is 1.588 ohms/1000 ft. which equals 0.01588 ohms/10 ft.

Take 10 feet of 12 gauge wire, form it into a coil about a foot in diameter and then crimp and solder the ends into lengths of 3/8" copper tubing.  Dunk the coil in a bucket of water and use the 3/8" copper as conductors to your new "power sink".  This should draw ~378amps at 6 volts.  

The copper tube ensures that almost all the heating occurs under water and crimping a few inches with a hammer and then soldering shoud give a cheap reliable transistion splice.

Copper is not great for resistance but at these current levels it'll dissipate plenty as heat.  The water will keep it from glowing and falling apart.  This wouldn't be suitable as a dump load for long term use but as a test load it should do fine.

Hope this helps

[richhagen]

I have golf cart batteries in my Commutavan.  I use Dual Pro chargers which are onboard and charge each 12V string independantly.  Since the outputs of the chargers are isolated, the batteries should charge OK unless one of the two batteries in that string are bad.  

Would not a regular 12V battery load tester work to test the batteries?  It would take longer because at 6V the current would be 1/4, but it should work.  Measure voltage, load down for a period of time, and then check condition again.  The weak batteries would show a lower voltage while under load after the load had been connected for a while.  Just an Idea.  Rich

[crashk6]

You know I could swear the last time I was in my local harbor freight tools I saw a load tester that was switchable between 12 and 6 volts... Might be worth looking into!

--

crashK6

[Drives]

Jerry:

I forgot to mention, but I have seen large load banks made by using a drum filled with salt water.  You just take your two battery wires, and connect them to pieces of copper pipe or rod.  Next, suspend the "electrodes" into the salt water solution, and viola!  Instant hot water bath...watch out that you don't boil out the drum dry. I suspect a quality plastic garbage can would work if you don't get the solution to hot.

If you aren't conducting enough current, just add more salt to the solution.  I've seen standard winter rock salt used.

This maybe a different idea for you to use.

[pwr]

You have a load tester - its your vehicle.  Why not measure the temperature of all the batteries after driving it.  While you're at it, measure the voltage.  Don't be surprised to find one or more of the cells with reverse polarity.  If so, they are charging during operation of the vehicle and gassing to generate the smell.

More than likely, individual cells in the 6-volt batteries will have reversed, not the whole unit.  If one cell is reversed, you will have a 4-volt battery.

I've been designing battery systems since the 1960s, and I have never owned a load tester, preferring to use actual loads when the problem demands it, which is almost never.  Load testers are a handy tool for an auto mechanic who wants to convince a customer that they need to buy a new battery.  Their technical value is essentially zero.

[monte350c]

Hi Jerry,

Sorry to hear about the problems.

You probably already know this one.

If you have a standard volt-ohm meter that has alligator clips at the ends of the test leads you can clip a short piece of something conductive (I often use a nail or cotter pin) into the end of the positive and negative leads of the meter.

Then pull the caps off the batteries. Safety glasses are a great idea. Dip the cotter pins into the battery acid of 2 cells next to each other. You will see about 2 volts between each cell. The last cell has to be measured between the post and the electrolyte. You don't have to touch the plates when you're doing this - just the electrolyte.

If there's something funny going on with a cell in one of the batteries this will help to pinpoint it. (like shorted, reversed etc.) Sometimes it helps to put a small load on while doing this but not usually needed.

I've identified bad cells in a lot of batteries this way.

Ted.

[Ungrounded Lightning Rod]

Before you go into deep testing, have you:

 - Checked the electrolyte level in all the cells

 - Done an equalizing charge on all the batteries.  (If your big charger isn't up to it, do it independently on the batteries one or two (with a 12v charger) at a time.)

 - Rececked the level, and then

 - Checked for a low-voltage battery or a cell with a deviant specific gravity?

What you're experiencing sounds to me like an unequalized battery.  (In this case the "battery" is the total collection of cells.)

So if you haven't already done so, what you might need to do is equalize it, re-water it, replace any batteries with cells killed by deep discharge when not equalized, equalize and re-water AGAIN if you had to replace any, and THEN try it.

A big battery bank that gets out of equalization can push a horrendous voltage across a discharged cell.  Perhaps that's what you're smelling.  And it also needs a whoping voltage to do an equalization - which could lead to trouble if a cell is going dry or dead.

By the way:  After you scrubbed your car's guts down you might want to rinse it with a sodium bicarbonate solution (and then water to rinse that off) just to head off more corrosion.

[RobC]

I have a dumb question, why not just feel each batt after you drive to work. If you are smelling something you should be able to feel a hot battery or a hot cell. I would wear safety glasses incase it decides to blow while you are checking. I know all the other load tests etc etc probably should be done as well but what have you got to lose? RobC  

[Jerry]

WOW

Thanks guys so many responses. I'm inpresed. Its for sure I'll be doing something to get the E-Car back on the road. I hear gas prices are going up again?

The large load tester is about half done so I'll try that. I'm a littel afraid to take the truck out on the road and risk a battery explosion or maybe a long walk?

Besides the load tester will be adjustable for higher voltage and since I have 2v, 6v, 12v and 48 volt systems it will come in quite handy.

I found out the amp meter is 500 amps. The aircraft relay is 400 amps. The test leads are 4ft each of 4/0 welding cable.

I'm building the tester on a pice of 1" plywood 12"X 30". The 5/8" diameter load coils will be away from the wood with an aluminum heat shild protecting it from ignition.

At this amperage the test should be in short duration.

I'll let you all know how it works out. Thanks for all the input.

                           JK TAS Jerry

[ibedonc]

Jerry you need to read this

http://www.los-gatos.ca.us/davidbu/sparrow/s_diary.html

read about the bat voltage clamping circuit

look for comments at "4686 Miles" , you can search for that , but good reading for what you are doing

[Tallwind82]

If I am reading this right you are suggesting a potentially dangerous load test.

If you suspend two separate electrodes in saltwater and connect them to the battery terminals you have a hydrogen generator! The electric current separates the hydrogen from the oxygen, copper electodes will use some of the oxygen through oxidation. The bubbles you see are HYDROGEN, VERY FLAMABLE!!

Be very careful if you try this, no sparks or other sources of ignition.

[nothing to lose]

Well Jerry,

We all know it is more fun to build than to buy and often cheaper, but if your needing it quick HarborFrieght has a 500amp load tester pretty cheap normally. I don't recall what the stores sale price is on it, maybe around $50 or even alot less. I know I was going to buy one myself awhile back but then I wanted something else more important at the time and could only afford one so I skipped the load tester.

I always go to HF store with a bunch of money and look for on sale items, problem is I find more items than I have money for and have to choose which to buy

It has a dial knob so I think you can adjust it for various loads for different testing too. Like you may only want to test at 50amps for a car batt. but 500amps for a series of trojans perhaps. Being ajustable is good, not sure of any other features it had, but I did like it and wanted it myself. (For certain it was far cheaper and better than the $70 50amp tester I orderd from auto zone before I found the HF store!!)

What I wanted it for myself was to test the entire bank when wired up. Figure it's 416amps to power my 5K inverter under full load and also 832amps for the 10K surge. So cranking up a 500amp load on a bank should let me know how well I have it wired up for the inverter use. You know, if I have a bad wire or connection, it should show up

Also a good indication how long I could run the inverter maxed out with a continous load on the bank. Like crank it to 400amps and let it run while watching volts close.

Not really sure the tester could be run continous, the expensive 50 amp I have says only a minute or so, so maybe that's about all for the HF 500amp one also, don't know.

All the 50amp one is is a heater element basicaly, load test and it turns red hot.

The 500amp one said carbon pile load tester though. Not sure the difference if any.

[nothing to lose]

Your right, they have at least 3 at HF.

The carbon pile 500amp one I just posted about a second ago. Around $50 or less I think.

A 50amp often on sale for about $13.

A 100amp also often on sale below $20.

The 50 and 100 amp ones are like my 50amp one with a heater element in the back that turns red hot.

The one I have does 6V or 12V no need for a switch, has a needle and the scale is marked in volts and color coded for good week bad for 6V and 12V, so I could even test a 8V with it if I do a bit of geussing, 8V ain't marked but easy enough to figure out.

The HF ones are about the same and I would buy those any day instead of the $70 I paid autozone for my 50amp tester!!!

[Drives]

I don't disagree that this process may be used to produce hydrogen. I don't know enough about the process to fully understand how boiling salt water by passing current through it causes H20 to separate.  

However, I have seen it used as a load test for motor shops after they repair a large 3 phase generator.  It was "neat" to watch the solution boil, and froth as the generator shaft was spun at different speeds to produce varing outputs.  There was never an arc produced, rather just passing current through the solution.

I'm sure it is dangerous, but being a smoker back then, we all were smoking cigerattes around the setup.  The barrel was outdoors, that may have been our saving grace as to why we did not blow up.  To my knowledge, this testing procedure has been used for at least 15 years now....never did see a sign that said don't smoke around the barrel.

[Tallwind82]

 The process is essentially the reverse of that used by a fuel-cell only easier. In a fuel-cell the hydrogen and oxygen are combined via the catalyst and electric current is produced.

 One of the experiments with the chemistry set I had when I was a kid was to make hydrogen out of water. A test-tube was filled with saltwater and suspended upside-down in a bowl of salt water. One wire from the battery was inserted into the test tube, and the other into the saltwater surrounding the test-tube.

 Being a pyro I, of course, had to light off the hydrogen for fun.

 In my experiments I never noticed any heat build up, but then I was only using (2) D-cell batteries for a total of 3 volts. I suppose with 3ph 220v (or whatever voltage you were testing) the process would be accelerated enough to boil the water, which could be what kept it from igniting, the steam may have caused the hydrogen to dissipate quickly.

Just had an interesting thought;

A hydrogen generator would be a good way to use the excess power from a windmill, once the batteries are charged. The hydrogen could then be compressed and stored for use in a fuel-cell either for a fuel-cell powered car, or a backup power source. Basically using the water-hydrogen conversion coupled with a fuel-cell as a big battery.

[Jerry]

Thanks Don.

Thats a good read. The whole story is very intresting and very long.

                        JK TAS Jerry

[Nando]

JK TAS JErry:

Do not make your life difficult, get a 12 volts 500 amps battery tester and check the 6 volt battery 2 at one time.

Test 1 & 2, then 2 & 3, then 3 & 4 , then 4 & 5, So on to find the bad one, if properly done (RECORD DATA) you may find the bad batteries, one problem would be the first and the last battery, that do not have second test position, though you may be able to define if good or bad.

Regards

Nando

[Jerry]

Hi Nando.

To late. I've built and used the large (25LBS) tester. It works great. We use the large lift truck 2 volt cells in some of our large audio systems. We add one of these cells to our very large exsisting 12 volt battery banks for a 14 volt bank.

Car audio compitition sanctioning bodies now alow up to 18 volt battery banks onboard your car.

This tester gives us a way to aply a very heavy load to a single 2 volt cell. I think about 133.33 amps for a 2 volt cell since its a 400 amp load at 6 volts.

I can also remove one or more of the 3 resistor/coil sections for 12 volt testing since by relay is only 400 amp rated.

With mega watt car audio system, electric vehickles, 12 volt, 48 volt and 120 voltr RE systems this versytile load tester is very handy.

                           JK TAS Jerry

[scottsAI]

If the battery is excessively dropping voltage under load.

Then, like the other guy said, measure the battery while driving!

Yes, that simple. All the batteries should have the same voltage.

You will find one that is much lower, even reversed.

Using only Two meters, measure high half, and other meter lower half.

If you trust your in vehicle meter, then only need to use one DVM.

Each half should be nearly the same. With 10 batteries some variation will occur.

When you find which half is the problem then do the same thing again.

Split the half in half. Then again, and again.

You can find any battery in 5 measurements.

Remember, the load test is done when the battery voltage is dropping below what you knew as normal before. More than one battery may be a problem.

Using several meters will shorten how many tests you need to do.

10 DVM from HF at $3.99 is much less than the load tester they have.

Have fun.

Scott.

[ghurd]

And 10 or 20 meters at the same time is just plain fun!

But I love blowing fuses too.

G-

[scottsAI]

Yes :-)

Burning wires is even better!

[ghurd]

Big fun!

I just smoked all the wires on a $4 item.

Shipping from Asia was $55.

Not sure if I had $59 worth of fun.

There was sparks, stink and smoke, but no real flame.

Evedently, it needs a redisign for 'short circuit protection'.

[ghurd]

And now the wife won't let me work in the kitchen.

[scottsAI]

I have a shop in the basement.

When I burn wires nobody knows but me!

Have fun.

Scott.