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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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#81
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Plain bearing example
Jim Wilkins wrote:
The HF carbon pile has a 15 second timer to warn you to grab the reading and turn the current down. Since it's unstable at low current / light pressure I didn't attempt to determine how much power it could handle continuously. My guess is less than 100W, from comparing the disk stack to wirewound rheostats of similar size. The timer circuit limits the voltage it could withstand. The manual specifies: "15 seconds per test with 1 minute cool down" "3 tests in 5 minutes maximum" 500A is claimed to test a battery rated at up to 160 amp hours or 1000 cold cranking amps. When the battery on my main vehicle was drained by leaving the hatch ajar for a week I replaced it to avoid the risk of getting stuck somewhere in frigid weather - right now it's 3F outside. I traded in a junk battery and kept it and it's still good for 150A at 16 years old. The HF load tester is to help me squeeze more life from batteries I don't depend on. https://archive.org/details/73-magazine-1976-11 page 159 Has an adjustable solid state load. You can add more pass transistors to increase the current it can handle. You could add an op-amp and a DAC to set the current from a computer if you want to get fancy. -- Never **** off an Engineer! They don't get mad. They don't get even. They go for over unity! ;-) |
#82
Posted to rec.crafts.metalworking
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Plain bearing example
"Michael A. Terrell" wrote in message
... Jim Wilkins wrote: The HF carbon pile has a 15 second timer to warn you to grab the reading and turn the current down. Since it's unstable at low current / light pressure I didn't attempt to determine how much power it could handle continuously. My guess is less than 100W, from comparing the disk stack to wirewound rheostats of similar size. The timer circuit limits the voltage it could withstand. The manual specifies: "15 seconds per test with 1 minute cool down" "3 tests in 5 minutes maximum" 500A is claimed to test a battery rated at up to 160 amp hours or 1000 cold cranking amps. When the battery on my main vehicle was drained by leaving the hatch ajar for a week I replaced it to avoid the risk of getting stuck somewhere in frigid weather - right now it's 3F outside. I traded in a junk battery and kept it and it's still good for 150A at 16 years old. The HF load tester is to help me squeeze more life from batteries I don't depend on. https://archive.org/details/73-magazine-1976-11 page 159 Has an adjustable solid state load. You can add more pass transistors to increase the current it can handle. You could add an op-amp and a DAC to set the current from a computer if you want to get fancy. I used a large water-cooled active load to test battery packs at Segway. I don't need that much expense and complexity at home since I don't sell a product that I have to guarantee. I do have enough large fixed and variable power resistors to pull up to 65A continuously from a 12V battery. Instead I use DC-AC inverters as constant-power discharge loads with low voltage shutoff to protect the battery. My standard loads are a 30W soldering iron to imitate a laptop and a 100W crockpot which approximates the laptop, keyboard light and an external TV/monitor. The inverters draw more current as the battery voltage drops and reflect the available runtime of a real load better than a non-compensating constant current or resistance load would, although a resistor load is simpler and may be a better long term indicator of a battery's age deterioration. I bought a battery protector that I haven't tested yet, too many outdoor projects. It's intended to switch a boat or RV to a backup battery before the primary one drops too low to start the engine. I'd have it switch the battery under test from the discharge load to a charger. The datalog will capture the time of the jump. Serial- or USB-connected DVMs are fine for logging batteries because their 1 or 2 readings per second rate is good enough and being optically isolated they're unaffected by the common-mode ground voltage differences that high currents produce in cables. Plus they can't accidentally short-circuit the battery through the laptop. I was fortunate to be facing away and slightly outside the fireball when the tech next to me caused that type of accident with scope probes. -jsw |
#83
Posted to rec.crafts.metalworking
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Plain bearing example
On Wed, 21 Dec 2016 14:24:36 -0500, "Jim Wilkins"
wrote: "Michael A. Terrell" wrote in message ... Jim Wilkins wrote: The HF carbon pile has a 15 second timer to warn you to grab the reading and turn the current down. Since it's unstable at low current / light pressure I didn't attempt to determine how much power it could handle continuously. My guess is less than 100W, from comparing the disk stack to wirewound rheostats of similar size. The timer circuit limits the voltage it could withstand. The manual specifies: "15 seconds per test with 1 minute cool down" "3 tests in 5 minutes maximum" 500A is claimed to test a battery rated at up to 160 amp hours or 1000 cold cranking amps. When the battery on my main vehicle was drained by leaving the hatch ajar for a week I replaced it to avoid the risk of getting stuck somewhere in frigid weather - right now it's 3F outside. I traded in a junk battery and kept it and it's still good for 150A at 16 years old. The HF load tester is to help me squeeze more life from batteries I don't depend on. https://archive.org/details/73-magazine-1976-11 page 159 Has an adjustable solid state load. You can add more pass transistors to increase the current it can handle. You could add an op-amp and a DAC to set the current from a computer if you want to get fancy. Have to check that out. I used a large water-cooled active load to test battery packs at Segway. I don't need that much expense and complexity at home since I don't sell a product that I have to guarantee. I do have enough large fixed and variable power resistors to pull up to 65A continuously from a 12V battery. Ceramic wirewounds? That's some watts! I'm switching to a 20gal water heater and using the 1kW of solar to heat it with a 900w 24v element. One of the two original 3,800W elements will be left installed and put on a timer to run for one hour (while power is available) to bring it up to heat if the solar doesn't make it. The bursitis is easing so I'll be back on the project some day soon, weather permitting. Instead I use DC-AC inverters as constant-power discharge loads with low voltage shutoff to protect the battery. My standard loads are a 30W soldering iron to imitate a laptop and a 100W crockpot which approximates the laptop, keyboard light and an external TV/monitor. The inverters draw more current as the battery voltage drops and reflect the available runtime of a real load better than a non-compensating constant current or resistance load would, although a resistor load is simpler and may be a better long term indicator of a battery's age deterioration. I bought a battery protector that I haven't tested yet, too many outdoor projects. It's intended to switch a boat or RV to a backup battery before the primary one drops too low to start the engine. I'd have it switch the battery under test from the discharge load to a charger. The datalog will capture the time of the jump. Why would you run accessories on anything -but- the acc battery, Jim? Relay charges both when power on/engine running, but only the acc battery is used when the engine is off. Your main starting battery stays full at all times. Install that protector, mon. They should draw no power when the switch is off, and the coil only takes a dozen or two watts when it's on, so it's not a noticeable drain on the alternator. That's a half hour project. Serial- or USB-connected DVMs are fine for logging batteries because their 1 or 2 readings per second rate is good enough and being optically isolated they're unaffected by the common-mode ground voltage differences that high currents produce in cables. Good call. Plus they can't accidentally short-circuit the battery through the laptop. I was fortunate to be facing away and slightly outside the fireball when the tech next to me caused that type of accident with scope probes. Oops! Lucky man, you are. -- ....in order that a man may be happy, it is necessary that he should not only be capable of his work, but a good judge of his work. -- John Ruskin |
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