How to interpret battery charger output

[Lewis Downey]

Please see the attached pic. The battery charger is set at very low amp output - 2amps @ 12volts. There are two gauges, one shows significantly more than 40 DC amps the other shows "Weak".

My CI is held in the electro by a threaded SS rod that passes through a small piece of wood. If I am not careful the wood gets hot enough to char. Normally I run it using the 10 amp setting to keep the wood from burning through.

Thoughts appreciated. Thanks in advance!

[Paul Beer]

Lewis, I think your problem is the rod being stainless steel...A picture of the hook up would be helpful...I use an iron hook to hold the cast iron which is held by a piece of PVC pipe over the top of the tank. You are shorting out or something by using a stainless rod I think...I'm sure some of the experts on this will show up shortly...Paul

[Jeff Friend]

I also use a stainless threaded rod supported over the electrolyte with a piece of wood.  Stainless has a higher resistance, but it isn't so high that it  will cause a problem.  What I noticed first is that the ammeter is reading 200 amps.  No wonder you are charring the wood.  I get good results with 10 to 20 amps on a large skillet (No. 9 or 10).  I clean one side at a time, so if you have 360 degrees of anode, your current will be higher.  My opinion is that you are sending too much current through your system.  Now before everyone chimes in saying that those ammeters are inaccurate, I do not agree, as long as they have not been damaged.  The ammeter on my Sears charger is within around 10 percent of the reading from a Fluke ammeter.  Even if your ammeter was reading 25 percent high, you are still in the range of 150 amps.  That is a lot more than you need.

Ohm's law (i = V/R) tells us that there are two factors that affect the current flow:

1.  V, which is the charger output voltage, and
2.  R, the resistance between the anode and cathode.

Current flow goes up with voltage and down with resistance.  The voltage is not something we can control as it is determined by the windings in the transformer.  We can control resistance.  If the electrolyte conductivity is too high, caused by too much salt being dissolved into the water, or the anode and cathode are too close together, the current flow can be high.

As for the other indicator, it has no bearing on cleaning cast iron.

Jeff

[Lewis Downey]

Paul, Thanks for your comments.

Jeff,

Thanks for chiming in. I agree that too much current is passing through... what to do about it? Notice that the control for the current is set to 2 amps.  If I bump the current up, the top gauge does move to the right.  Is the battery charger defective or is it something else?

This is an interim electro - something to use while I work out design issues for a 55-gallon version that will use interchangeable anodes (curved, flat, one of each, anode in the center, etc). This interim electro does not have 360° coverage, but it does have anode material on four sides. The stainless plates are connected to each other using 12 gauge copper wire above the electrolyte. Maybe I should use larger gauge wire but is that really the issue?

[Lewis Downey]

Paul, The first picture below shows two connectors. The top one is used to hang CI in the lye bath. The bottom one is used with the electro.  For the electro, CI is secured with a stainless wingnut and washers.

The wood blocks have a t-nut that holds the threaded rod as it passes through and allows height adjustment by threading the assembly up or down. The wooden block is secured in a larger wooden yoke. By turning the threaded rod the CI can be angled in the tank to get better visibility to the stainless anode material.

Charring is happening where the t-nut contacts the wood block.

[Jeff Friend]

Lewis,

I ran a test on my charger.  I checked the output voltage with no load and with a No. 10 skillet attached.  My electro unit has one plate about 8 inches wide and it is generally 10 to 12 inches from the piece being cleaned.  Here are the results:

Amp setting     No load output voltage        Voltage with load       Load
2 A                  9.08 V                               8.17 V                      ~8 A
40 A                13.49 V                              12.00 V                    ~15
200 A              17.92 V                              not tested

The charger can give a higher current by increasing the output voltage (Ohm's Law again).  That is what the selector switch is there for.  Since your charger is on the 2 A setting, you can't decrease the output voltage.  With your four anode plates, you essentially have 360 degree coverage (see note below) and it's not possible to increase the distance between the anode and the utensil being cleaned.

What is one to do?  Dilute you electrolyte solution.  I'd start by taking out a few gallons (saving the electrolyte for later) and replacing it with tap water.  Turn on the charger and see what your current flow is.  You might have to do a lot of diluting to get the current flow you want. 

I suspect that you attach the negative lead above the block of wood.  If you attached the lead below the block, the current (and the heat that is generated) would not flow past the block.  Some heat would be conducted up the threaded rod, and at 200 A, the rod might conduct enough heat to still char the block.  And make sure your connections are really good.  It takes a robust connection to carry 200 A without heating.  Unless your current flow is low, I do not think you can get a good enough connection by attaching the charger clip directly to the threaded rod.  There just isn't enough metal there to carry the current without heating.

Note
Have you been to Walmart lately?  When you have finished shopping and it is time for the dreaded checkout line, I doubt that you go to the cashier that is closest to you.  You look for the line that you think will be the easiest to get through.  If register 3 is backed up, you might walk all the way to register 25 if it has no one waiting in line.  Electrons flowing through electrolyte do the same thing, but in a much more orderly manner than Walmart shoppers.  Electrolytic cleaning is not a "line-of-sight" phenomenon, although in some configurations, line-of-sight is a close approximation.  Think of it as the checkout at Walmart.   :-/

Merry Christmas!

[Paul Beer]

Jeeze Jeff,that is some explanation.....but a good one for us cowboy electricans...I just clamp the negative on the pan it's self and clamp the positive on the top edge of the steel lining. I use 50 amps and don't have any heating....cleans things just fine...Use tap water with a little ph additive

[Cheryl Watson]

Lewis, I can't see the entire front of the battery charger... but... why are you using the timer?

When the timer dial is in the off position, simply turn counter clockwise to the HOLD position to turn the charger on, then to Off to turn the charger off.


I have had Schumacher chargers that malfunctioned with the timer dial. (fortunately right after purchase and exchanged promptly).

[Lewis Downey]

A couple of updates.

Cheryl, The power switch is in that position for the photo. In day-to-day operation I run it in the HOLD position.

Jeff,

re. diluting the electrolyte. I tried two new dilutions with interesting results.  The initial concentration was 25 gallons of water with three pounds of Rooto lye. I read somewhere that Rooto is about 95% pure; I don't know that to be a fact but using that purity the initial strength was approx. 1.37%.

I removed 5 gallons of electrolyte and replace it with water - so the new strength is about 1.095% A quick test and hardly any current flowed. With the battery charger set at 10 amps the output showed less than 2 amps.  Progress.

I pulled 2.5 gallons of the new dilution and replaced it with 2.5 gallons of the previous electrolyte.  The battery charger ran using the 10 amp setting and ta-da, the output read as about 8 amps. Nice. I could do the math for the third dilution but I'm not gonna - maybe at the end...

Now for the kicker. With the charger running I glanced down and saw a wisp of black smoke where the wire enters the red lead. Yipes. :o I turned off the charger, squeezed the clamp and wire simply broke off.  Pics attached. :'(  Virtually all of the damage had to have happened earlier.

[Lewis Downey]

Another update. I bought the battery charger from Northern Tool on August 18th. It is well within its warranty period but NT won't honor the warranty because it was damaged while in use for something other than charging batteries. I'll call Schumaker on Monday to see what they say.

Next thing. The clamps are designed such that either side of the clamp can be used to attach the wire. I could solder the wire back into the other side of the clamp, but I'm concerned that the damage was caused by some issue inside of the battery charger --  a rejiggered clamp might be unsafe.

[Mark R. Smith]

The clamps could be a big part of the problem. Did you have them in the lye solution? I use the washing soda for the electro solution. Lye separate solution. I have the charger clamps out of the solution for the one clamping to the cast iron I have it clamped to a steel L bracket and a solid copper wire from some 12 gage Romex to a bolt in a C clamp that clamps to the cast iron for a solid connection.

[Lewis Downey]

Mark,

Neither of the clamps goes into the electrolyte. The red clamp is attached to the portion of the stainless steel anode that protrudes several inches above the electrolyte. The black lead attaches to the angle at the top of the threaded rod, above the wood block (as Jeff suspected).  The CI is firmly attached to the bottom of the threaded rod.

Previously I added nuts and washers at the top of the rod, then attached the black lead to the washer. That worked fine but why incur the extra hardware. Instead I simply bent the rod. I am beginning to wonder if there is enough contact area but the gripping action from the clamp is strong. How much contact area do you need?  I've also thought of adding another 90-degree bend at the top. In that configuration the rod has an upside-down squared-off U-shape for the clamp to grip.

[Mark Zizzi]

I think it just got too hot from running at 200 amps for too long, just like the wood charring.  If it were mine I would just reattach the cable to the other side of the clamp and try it now that you have diluted the electrolyte. If you contact Schumacher don't tell them what you were using it for. They won't like it either.  ;)

[Jeff Friend]

I agree with Mark.  Attach the lead on the other side of the clamp.  I suspect that the electrical connection was compromised which caused the heating.  It won't take much resistance at 200 A to smoke the insulation.

It doesn't seem likely that only 8A would be flowing and your connection heated to the point of failure.  A possibility is that the connection fried during your tests and before you read the meter, so the indication of 8A would be misleading.  Replacing 20 percent of the electrolyte solution (5 of the 25 gallons) would have made about a 20 percent decrease in current flow - not much of a change. 

Your charger may be just fine, so I would make the repair Mark suggests and see what happens.  When you reattach the clip, you might want to solder the strands of the cable together and solder the cable to the clip.  This will give a better connection and will keep the connection from corroding.

Let us know what happens when you get it all back together.

[Lewis Downey]

okay... first time I have soldered anything in about 15 years. I soldered the wire to itself, crimped the wire to the clamp, and did what I could to solder the clamp and wire to each. My soldering iron was probably the weakest one commercially available when it was purchased; at some point I gave up on using it to heat the clamp, wire, and solder all at the same time. I used a butane torch to melt the solder. The end result is less than pretty. Some of the rubber coating on the wire melted.

After everything cooled, the battery charger was set the to 10amps and turned ion. It instantly read between 40 and 200 amps of current, so I turned it off immediately.

That's the report.

[Jeff Friend]

Lewis,

At this point, I would suggest verifying that the charger is working properly. 

1.  Is the fan running when you turn on the power?  If it isn't, the diodes or windings in the transformer could have overheated.

2.  Do you have a volt meter or know someone that does?  You should be getting 14 volts +/- a few on all three settings.  If you are getting something much higher, say 20 or 25 volts, something is wrong with the charger.

If the charger seems to be working properly, start over with the electrolyte solution.  I would suggest filling you tank with just water, putting in a pan, and turning on the power at the 40 amp setting.  You shouldn't get any current flowing.  Add Rooto 1/8 of a cup at a time, mixing the contents of the tank thoroughly after each addition. (a paint mixer on an electric drill would work for this, but make sure the charger is off before mixing.)  Record the current each time.

Jeff

[Duke Gilleland]

Thru the years, I always found over heating at clamps was caused by BAD CONNECTIONS. You might have a faulty connection even though it is getting enough power thru to register on the meter and sparking. I  have had good luck thru the years using SOLID copper wire. This is as Paul said: "A Cowboy electrician observation" [smiley=horse.gif]. All those EYE bolt connections are causing resistance & heat. I have burned the clips off of smaller "cracker box" chargers before. Had good luck with the Sears manual charge larger units.

[Lewis Downey]

Another update, but first thanks Jeff, Duke, and everyone who spends even a few moments thinking about this on my behalf. What an incredible resource.

The fan worked with the charger turned on. I tested the connections at the clamps with a voltmeter and got the following approximate values for voltage with no connections made -- i.e. the battery charger turned on but not connected to the electrolysis tank.
2 amp setting: 9volts
40 amp setting: 12volts

On the theory that everything is working mechanically but too much current is flowing, I changed out the piece of cast iron in the electro. The piece that brought all the trouble into focus is a No. 12 Lodge skillet. It is quite large.

The anodes form a box that is about 18"x14". Even when adjusted to provide maximum spacing the No. 12 skillet was pretty close to the side anode plates. As a quick test, I pulled the #12 skillet and replaced it with a regular sized square grilling skillet - about 9" on a side.

With the battery charger set to 10 amps the current read somewhere between 40amp and 200amps with the No. 12 skillet in the electro. With the smaller skillet, it reads less than 40amps.

After a couple of hours of cleaning the square grilling skillet I will the following using the Lodge 12SK again and report the results.
1 - Remove the side anode plates (and check current)
2 - Dilute the electrolyte per the Jeff's plan  (and check current with side plates removed)
3 - Put the side plates back in  (and check current with the diluted electrolyte)

Thanks again everyone.

[Lewis Downey]

This situation is approaching a resolution.  I am mid-test and the variables are beginning to come together. Data are shown below. I did the math from the previous dilution of the electrolyte and determined that the  strength was 1.19% by weight.

I did not measure the temperature of the electrolyte, but the electrolysis tank is in the basement where the ambient temperature is in the mid-60s. The 4 plates form a box-like structure as shown in a pic somewhere above; the dimensions are 18"x14" give or take. When the charts below shows 2 plates, the smaller side plates were removed, so that the two large plates were still in use. When the charts shows 1 plate, only one of the large plates was in use.

Electrolyte strength: 1.19%
Battery Charger set to 10 amps

		DC current	DC current
placement	# plates	Lodge 12SK	8" sq skillet
centered	4	300+ amps	38-40 amps
centered	2	60-70 amps	35 amps
middle: about 6"	1	22 amps	21 amps
max dist.: about 12"	1	18 amps	18 amps

After taking those readings I removed half of the electrolyte and replaced it with water, cutting its strength in half.

Electrolyte strength: .6%
Battery Charger set to 10 amps

		DC current	DC current
placement	# plates	Lodge 12SK	8" sq skillet
centered	4	38 amps	24 amps
centered	2	29-30 amps	20 amps
middle: about 6"	1	16 amps	12 amps
max dist.: about 12"	1	10 amps	9 amps

These numbers are behaving exactly as you would expect. More current flows with the larger the piece of cast iron. More current flows with more anode area. More current flows the closer the cast iron is to the anode.

I find it interesting that with a single plate the size of the cast iron does not have as much affect on the current.

I plan to completely replace the electrolyte with a fresh batch mixed at very close to .25% by weight. That is a nice easy 1/2 pound of Rooto per 25 gallons water. At that dilution with normal sized cast iron (like a No. 8 skillet) and 4 plates, I hope that the current setting on the battery charger will roughly match the current flowing per the DC Current gauge. If it does not match match exactly, there should be enough control over a given piece (removing plates or adjusting the distance to an anode) to make sure that the previous situation of 400 amps of current does not occur again.

Jeff, Great diagnosis!  :D  As of now I am back up and running in limited fashion with full and safe function on the horizon.

Before replacing the electrolyte, I am going to clean a couple of nasty pieces of steel cookware. It may be a day or two but I will report the results of the new electrolyte  dilution once it is in the tank.

[Jeff Friend]

Lewis,

That was a great post.  I really like seeing the data and appreciate the time it took you to pull all of those numbers together.  One question - did you use a real ammeter like we discussed on the phone or the meter on the charger to get the current readings?

Jeff