trouble shooting 12v welder

[coachgeo]

grrr.... I got autologged off before I was done typing, now I got to do it all over again.... that suks.

ok.... typing faster

got a battery powered wire feed welder. Crude but works. wire feeder is seperate power supply. Weld power source is presently 3 marine batteries in series. (36v). Been welding great, laying beads like butter. sweet welds then out of the blue with no changes to welding material I get shiat for welds and burn backs. no heat it seems.

think I have either battery problems, charging problems, or conductivity problems. I have an typical Volt/amp/ohm meter but dont think Im using it right.

How do I test welder calbes between batteries and weld tip to make sure they are conducting well? I get full voltage but cant seem to find a way to measure amps with this meter. Meter's battery is dead but isn't that for Ohms? Cables look fine. no corrsion. a few broken strands on the end of the wire where it connects to the welding tip. Very few like 5-10 out of the hundred or so there.

chargers are auto on/off trickle chargers 3- one for each battery (not hooked up when welding). 1.5 amp output. Are these putting enough volts in battery but too little amps??

One battery may not be holding well. Seems to want to stay at 10v. It's a sealed battery. any testing suggestions on this? I have hooked one of the other batteries trickle chargers to it to see if it's charger is not up to snuff. I swapped all the chargers to a different battery

Open to suggestions.

[MicroZone]

Check with the manufacturer ...or did you build it yourself ?

[MAC702]

Batteries have to be tested with a load bank. You can easily get 12V from your VOM and still have no significant power available in a battery.

[Rick V]

George,

It sounds like you are not getting current into the wire.
Does it weld like it used to on 2 batteries or on just 1?

RE: Meter's battery is dead but isn't that for Ohms?
If it is a digital display or an analog (needle) display with an off/on knob, you need a battery inside it to operate it properly. If it's an inexpensive analog needle type with no off/on knob, you are right - the battery is there for resistance measurements only.

RE: How do I test welder calbes between batteries and weld tip to make sure they are conducting well? I get full voltage but cant seem to find a way to measure amps with this meter.

You can measure the voltage drop along a length of cable - say between the +ve terminal of your battery to where it (the same cable) connects to your MIG gun. A Wire Table (on the web) will give you the resistance per foot of any gage cable. e.g. If you measure 500 millivolts (1/2 volt) over 10 feet of cable that has a resistance from the table of say 0.001 ohms per foot, then you can figure the amps flowing in that cable from V=IR or I=V/R.
I amps = (500 /1000 volts) / (10 ft x 0.001 ohms) = 50 amps

Charging at 1.5 amps overnight puts about 12 hours at 1.5 amps = 18 amp per hours into the battery. If your batteries are the typical marine deep cycle batteries, they are rated at about 100 amp per hour. So, you going to need 100 / 1.5 = 66.6 hours almost 3 days to charge one battery from being discharged. You have three batteries - but three chargers so three days.

Now I don't know for how long you weld for at a time, but that rig of your's probably pumps out 200 - 300 amps of welding current at 36 volts (I recall you could do 1/4 inch in one pass). If you mess about for say 10 minutes gun-on time, my guess it you have drawn considerably from your 100 amp per hour capacity (that rating is only for a 25 amp/hr draw, it drops a lot with heavier current draw).

RE: One battery may not be holding well. Seems to want to stay at 10v.
That is a BAD sign! Sounds like a dead cell. With one dead cell in the circuit, it will severely limit the amps you can deliver - that cell will be charging in reverse. Very hard on the cell!
Try welding with just the two good batteries; if it is better than with all three - the low battery (cell) may be toast unless you can recover it with a long charge time.

I'll bet on that one low battery.

Rick V

[coachgeo]

Great responces thanks. I'll take my standard batt charger over there and put it on a different battery per day to help get more amps pumped into each battery.

[coachgeo]

Can I wire them in parallel or something and charge them all at once off my larger charger at the same time?

[Tailshaft56]

You can't charge batteries in parallel. The one with the lowest internal resistance will get most of the amps. They can be charged in series if you can supply the correct voltage, A little over 36 volts in your case.

[Rick V]

George, here is a typical Copper Wire Table.

American Wire Gauge Copper Wire Chart
AWG---------Stranding-----------Inches--------------mm----------Circular mil area----Weight lbs/1000 ft ------ kg/km----D.C. Ohms per 1000 ft----Ohms/km
8---------------49/25---------------.147---------------3.734---------------15,697.0---------------47.53---------------70.73---------------0.67---------------2.2
8---------------133/29---------------.147---------------3.734---------------16,984.0---------------51.42---------------76.52---------------0.61---------------2.0
8---------------655/36---------------.147---------------3.734---------------16,625.0---------------49.58---------------73.78---------------0.62---------------2.0
6---------------133/27---------------.184---------------4.674---------------26,813.0---------------81.14---------------120.74---------------0.47---------------1.5
6---------------259/30---------------.184---------------4.674---------------25,900.0---------------78.35---------------116.59---------------0.40---------------1.3
6---------------1050/36---------------.184---------------4.674---------------26,250.0---------------79.47---------------118.26---------------0.39---------------1.3
4---------------133/25---------------.232---------------5.898---------------42,613.0---------------129.01---------------191.98---------------0.24---------------0.80
4---------------259/27---------------.232---------------5.898---------------52,214.0---------------158.02---------------235.15---------------0.20---------------0.66
4---------------1666/36---------------.232---------------5.898---------------41,650.0---------------126.10---------------187.65---------------0.25---------------0.82
2---------------133/23---------------.292---------------7.417---------------67,936.0---------------205.62---------------305.98---------------0.15---------------0.50
2---------------259/26---------------.292---------------7.417---------------65,475.0---------------198.14---------------294.85---------------0.16---------------0.52
2---------------665/30---------------.292---------------7.417---------------66,500.0---------------201.16---------------299.35---------------0.16---------------0.52
2---------------2646/36---------------.292---------------7.417---------------66,150.0---------------200.28---------------298.04---------------0.16---------------0.52
1---------------163,195.9---------------.328---------------8.331---------------85,133.0---------------257.60---------------383.34---------------0.12---------------0.40
1---------------172,508.0---------------.328---------------8.331---------------82,984.0---------------251.20---------------373.81---------------0.13---------------0.41
1---------------817/30---------------.328---------------8.331---------------81,700.0---------------247.10---------------367.71---------------0.13---------------0.42
1---------------2109/34---------------.328---------------8.331---------------83,706.0---------------253.29---------------376.92---------------0.12---------------0.41
1/0---------------133/21---------------.368---------------9.347---------------108,036.0---------------327.05---------------486.68---------------0.096---------------0.31
1/0---------------259/24---------------.368---------------9.347---------------104,636.0---------------316.76---------------471.37---------------0.099---------------0.32
2/0---------------133/20---------------.414---------------10.516---------------136,192.0---------------412.17---------------613.35---------------0.077---------------0.25
2/0---------------259/23---------------.414---------------10.516---------------132,297.0---------------400.41---------------595.85---------------0.077---------------0.25
3/0---------------259/22---------------.464---------------11.786---------------163,195.0---------------501.70---------------746.58---------------0.062---------------0.20
3/0---------------427/24---------------.464---------------11.786---------------172,508.0---------------522.20---------------777.09---------------0.059---------------0.19
4/0---------------259/21---------------.522---------------13.259---------------210,386.0---------------638.88---------------950.72---------------0.049---------------0.16
4/0---------------427/23---------------.522---------------13.259---------------218,112.0---------------660.01---------------982.16---------------0.047---------------0.15

I had built a charging unit for a battery bank of 6, 100 amp/hr batteries in an inverter based power system for my home. My charger consisted of a 6 horsepower gas engine driving a 150 amp car alternator. I used 4 gauge booster cables to take power from the alternator to the bank of six 12 volt marine batteries connected in parallel. I had the same problem - how to monitor the output current of about 150 amps from the alternator. According to the copper wire table, 4 gauge wire is about 0.25 ohms per 1000 ft or 0.00025 ohms per foot. I measured the voltage drop over 15 feet, basically from the alternator +output terminal to just before the +clamp at the battery.
The 15 feet gave me a resistance R of 15 x 0.00025 ohms = 0.004 ohms
At 150 amps, this creates a voltage drop of V = I x R = 150 x 0.004 = 0.563 volts.

Actually, I measured the resistance of my cable length by using two cheap ($15) digital meters, one set for current (10 amps) and the second to measure the voltage drop. Example: Using a one marine battery and an external resistor, I passed 10 amps through the 15 foot cable and measured the voltage across the 15 feet as 42.3 millivolts. So V=IR, R=V/I=42.3 millivolts/10 amps = 4.23 milli ohms or 0.00423 ohms. Once I had the actual resistance of my wire (close to the AWS table), I could convert voltage drop to amps passing through the wire.

In fact, you can tap into your welding cable at a few choice spots with a couple of small wires (18 gauge) to bring the voltage out to your meter for a permanent monitor of amperage. The choice spots are carefully chosen so your voltage display actually reads in amps.

Example: In your case, if you were using say 12 feet of #1 gauge wire. According to the table that has a resistance of about .12 ohms per 1000 ft or 0.000012 ohms/ft. So 100 amps will yield a voltage of V=IR=100 amps x 0.000012 ohms/ft = 0.012 volts/ft (12 millivolts/ft).
OK, 100 amps ... 12 millivolts over a foot. Lets get that to 10 millivolts so the volts numbers are the same as the amp numbers. 12 millivolts over a foot = 10 millivolts over .83 feet ( 1/12m x 10 =.083 ft or 10 inches).
Thus 100 amps = 10 millivolts over 10 inches. Hey, if you can tap into the welding cable at two spots 100 inches (8.3 ft) apart, you will read 100 millivolts when the current through the cable is 100 amps; 100 = 100! You have a direct reading of the amps and you can actually see what your welding current while welding - I'd be interested to know just how many amps that 3 battery system of yours delivers... maybe upward of 200-300 amps?

Have fun - let's hope your weak battery is OK.
I measured my battery bank (6, 12 Volt 100 amp/hr batteries in parallel) - just sitting for a week after a full charge, the voltage is 12.55 volts.
If I were to charge it at ~10 amps, the voltage will rise quite quickly (1 hour or so) to say 13.5 then slowly (another 3 to 5 hours) rise to 14.3 or so.
With a 90 amp load being drawn from my 6 100 amp/hr batteries in parallel it takes about an hour to drop to 12 volts then stubbornly holds there. I never drop my battery capacity below 50% (300 ampere-hours) because to go below that significantly reduces the life of the batteries - the number of charge discharge cycles. The info gleaned from the web says 200 - 500 cycles at 50% discharge and less than 100 cycles if you go to 80% discharge.

George, it sounds to me like you may have been pushing you batteries pretty hard and not getting them fully recharged. The weak point in your system appears to be the small 1.5 amp chargers. In the surplus store here I see 12 amp automatic chargers (marine jobs with the labels removed - same unit i paid $55 for, saw it at WalMart for $49) for ~25$. One of those would deliver about 4 amps/battery or 3x what you have now. You could run a couple of those chargers in parallel - they don't fight.

Best luck,
Rick V

[Rick V]

I just saw Tailshaft56 comment - "You can't charge batteries in parallel. The one with the lowest internal resistance will get most of the amps. They can be charged in series if you can supply the correct voltage, A little over 36 volts in your case."

I sure that is correct in theory but in practice (my experience), there is little problem at all - especially if the batteries are similar in capacity and design.

I've been doing exactly that every week for the last three years with no problems. In fact, in my parallel bank of 6, 12 volt batteries, 3 are marine deep discharge cheapees from COSTCO and the other 3 are slightly larger units deep discharge units from Crown. When charging, they seem to divide up the charging current quite nicely between them. I do get some gassing from the COSTCO units before the Crowns but over a year the water levels have hardly declined - certainly no major difference between the batteries.

My one 12 volt 12 amp automatic charger does them all. If I have a big discharge, then I bring the bank up with my 150 amp engine/alternator unit until the current decreases to about 25 amps, then I top em off with the automatic charger.

Rick V

[coachgeo]

I just saw Tailshaft56 comment - "You can't charge batteries in parallel. The one with the lowest internal resistance will get most of the amps. They can be charged in series if you can supply the correct voltage, A little over 36 volts in your case."

I sure that is correct in theory but in practice (my experience), there is little problem at all - especially if the batteries are similar in capacity and design.
....Rick V

Worth a try. To make sure I do this right. How do you reccomend I wire the three in a parallel fashion with the charger?

[Rick V]

George,

I'm concerned about that one 10 Volt reading battery. Until you get that battery charged up and holding as per normal, say 12.5 volts, you will be limited in how you can charge your batteries.

I don't recommend putting that suspect battery in parallel (+ve to +ve and -ve to -ve) with two good ones else that 10 volt battery will grab most the current - OK if it comes up in voltage but...
if that weak cell stays bad, that battery will never come up in voltage; it will stay at ~10-11 volts. In that case, most all the output of your charger(s) will keep going into that 10 volt battery and the voltage of the parallel bank will not rise about 10-11 volts. Eventually, the 10 volt battery will be gassing heavily while the other two batteries just sit there getting nothing.

With the batteries disconnected from each other, check the voltage on each battery. Say you get:
Bat 1 = 12.5 volt, Bat 2 = 12.2 volt and Bat 3 = 10.1 volt
I would parallel Bat 1 and 2, +ve to +ve and -ve to -ve, and connect your larger charger (+ve charger to +ve battery and -ve charger to -ve battery) to that bank. Put Bat 3 on a separate charger - and leave it there until you get it up to 12+ volts.
Note: Sometimes (20%) you can recover such a weak battery by several charge/discharge cycles - the battery recovering capacity with each cycle.

If you can get Bat 3 up to 12+ volts and it holds there for several hours without a charger on it, then you can joint Bat 3 that into your bank - again +ve to +ve and -ve to -ve.

As for the chargers, you can mix them up as you like as long as they are connected in parallel: +ve to +ve and -ve to -ve. Why? The diodes inside a specific battery charger prevent the current from the other chargers from entering that specific charger. So, none of the chargers 'see' each other. e.g. You can parallel (+ve to +ve and -ve to -ve) your three 1.5 amp trickle chargers with say a 12 amp charger and a borrowed 20 amps charger - again always +ve to +ve and -ve to -ve. This will put out about 3 x 1.5 + 12 + 20 = 36.5 amps. I say 'about' because as you add more chargers (current) the battery bank voltage will rise so you deliver less current - those 5 chargers will likely deliver about 31 amps or so.

Actually if you get Bat 3 back, you can hook your batteries back up in series again and connect a 1.5 amp charger to each battery as you did before. George, there was nothing wrong with your original charging set up but I suspect you didn't have enough charging amps or didn't allow enough time to fully recharge the batteries.

Best luck
Rick

[sunpowered]

:cool: I would disconnect all the batteries and test them each alone, then let them sit for a hour and recheck. if there is a problem you will see the drop in voltage.I can also tell you to check amps on 12 volt you need a DC amp meter as a AC amp meter will not work for this. I know a little about batteries as I have been solar for years. I would look at cleaning all contacts as dirty contacts are your wosrt enemy. I hope this helps a bit.

[Rick V]

George,

You should make an estimate of how much amp-hr you are drawing.
Assume you are doing your typical welding set up. How long do you weld for at a given time?

e.g. Say, you run beads for say 30 seconds then mess about and run another 30 second bead 3 minutes later. You continue in this fashion for 15 minutes. Then 1/2 hour break, then back at it for a total period of 3 hours. Call that a day. In a day then:
Number of 30 second bursts = (15/3) x (3x60 / 45) = 5 x 4 = 20
Current on time = 30 sec x 20 bursts = 10 minutes
Say your rig delivers 250 amps during a burst, that becomes 250 amps x 10/60 = 41.6 amp-hour. If your batteries are rated 100 amp-hour, the best you will do is about two days of welding before your battery bank is depleted to 50% capacity.

Say you have been recharging at the end of each day. You have pulled out ~42 amp-hr from each battery. If you charge each battery using a separate 1.5 amp charger, it will take at least 42 amp-hr / 1.5 amp = 28 hours to recharge. If you only charge for 24 hours/day less 3 hours welding = 21 hours, you are short about 7 hours (28 - 21) per day of charging = putting in only 21/28 = 75% of what you took out. In two days, you are at 56% (.75 x .75), 3 days = 42% (.75 x .75 x .75) , 4 days = 32%, 5 days = 23%, 6 days = 18% and 7 after days your batteries are at 13% of their capacity.
Could this have been what happened?
So George, what are your welding numbers - How long do you weld for at a given time?

Rick V

[Tailshaft56]

I just saw Tailshaft56 comment - "You can't charge batteries in parallel. The one with the lowest internal resistance will get most of the amps. They can be charged in series if you can supply the correct voltage, A little over 36 volts in your case."

I sure that is correct in theory but in practice (my experience), there is little problem at all - especially if the batteries are similar in capacity and design.

I've been doing exactly that every week for the last three years with no problems. In fact, in my parallel bank of 6, 12 volt batteries, 3 are marine deep discharge cheapees from COSTCO and the other 3 are slightly larger units deep discharge units from Crown. When charging, they seem to divide up the charging current quite nicely between them. I do get some gassing from the COSTCO units before the Crowns but over a year the water levels have hardly declined - certainly no major difference between the batteries.

My one 12 volt 12 amp automatic charger does them all. If I have a big discharge, then I bring the bank up with my 150 amp engine/alternator unit until the current decreases to about 25 amps, then I top em off with the automatic charger.

Rick V I was a little hasty by saying can't. Shouldn't would have been appropriate. I agree if all batts are about equal it would work ok. But like you mentioned 1 bad batt will keep the others from charging. if you need max performance from each batt then they would need to be charged seperately or in series.

[coachgeo]

got them charged equally. Layed about 5 mins of beautifull bead then NOTHIN- Notta- could barely heat up the wire. Checked voltage and it was good everywhere. Including thru the piece I was working on.

took batteries to Autozone, according to them I got two dead marine deep cycle batteries. These of course are a pair of ones I bought used but supposidly good. The third one that tested fine was free.

Anyway..... what to do now.

well..... buy another used set of batteries orrr? http://www.weldingweb.com/showthread.php?t=6388

[Rick V]

George I have two options for you:

1 - Batteries
COSTCO sells 100 amps-hr marine batteries here in Canada for about $60 each. Three of those will set you back $180. However, it is end of season and I saw these cleared out two years ago at 1/2 price. BUT - you are going to have to invest more $ in a decent charging system.

2-Inverter power supply
Look at the posting "Converting Stick Welder from AC to Full Wave DC".
According to #5 yesterday, 11:08 PM from MotoFab, and I quote...

I don't want to dissuade you from your rectifier project Rick, but this Harbor Freight 80ADC inverter is on sale for $119.99. It might be easier to buy a complete box in the long run, but I know how it is once I get the scent of a project. Anyway . . .

I have one and it works real well. It is made in China, but it is the GYS brand in other markets. It has the Dinse cable connectors, and a cast bronze work clamp. Pretty nice by any standard. It is quite happy with 3/32" 7018 DC+. And uses a 20A circuit and is good with a 50ft 12AWG extension cord.

You can parallel multiple units and make a lotto amps. 160A for $240. Same goes with that HF 130A DC 220VAC TIG/Stick product. Just parallel the front panel pots and you have 260A for under $400 on sale. I mean since you are electrically industrious.

Jim
===========
George, you could parallel up two of those inverter units to replace your batteries. e.g. 160A for $240
You would then be free of battery hassles.
You also would have ajustable current 0 - 160 amps.
That would give you a pretty flexible MIG unt - and as a bonus, you would pick up stick capability.

If you can afford the stick/TIG units, then for $400 you would be armed with 0 - 260 amps and capable of doing DC stick, TIG and MIG.

Decisions, decisions... :)

Rick

[coachgeo]

ahhhhhhh... more complications to all this. Come to find out these batteries that went bad are Gel Cells. Very expensive ones. (Prevailer Dry fit) From what I am reading this changes everything. For one the "Battery Life Saver" may not do squat to these. Also they are VERY PICKY when it comes to charging, etc.

More info on this type battery here

http://www.phrannie.org/sources.html#4H

[coachgeo]

George ..., you could parallel up two of those inverter units to replace your batteries. ...That would give you a pretty flexible MIG unt - and as a bonus, you would pick up stick capability...

Decisions, decisions... :) RickYep, Another factor is going the inverter welder route means I still have to eventually buy two batteries. You see two if not all three of the batteries I was welding with are also intended to go into the off road camper I am building. I got lucky (so I thought) on the two marine batteries. Thought I got just the right tickets for le$$ (good for welder and the camper)After reading the info on Gell cells looks like I may have fubared this all myself by not charging the gell cells correctly and by mixing in a flooded cell type (the third battery is typical cheap marine battery and NOT a gell cell)

[coachgeo]

Yep, Another factor is going the inverter welder route means I still have to eventually buy two batteries. You see two if not all three of the batteries I was welding with are also intended to go into the off road camper I am building....Well with much mental thought (I tend to overthink things) I bagged the route of replacing my batteries and upgrading the charging system. After looking at the cost of two inverter welders on sale (70 buks each) and the cost of two new medium level marine batteries that I would probably burn out before I even get the truck running I decided to go the inverter welder route. A cost I didnt count on was heavy duty extension cords. Still think I came out ahead in the long run

More on all this HERE (http://www.weldingweb.com/showthread.php?t=6403)