OK. I went to Harbor Freight and bought this meter to measure the charge in my detector battery. Sadly...I have no idea how to use it. The instructions were garbage. Where do I set it? When it comes to rifles and reloading you can ask me most any questions. When it comes to this stuff.....
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CEN TECH Digitial Multimeter
- Thread starter xwyokid
- Start date
Critterhunter
New member
I have on of those but it's been a while since I used it (I have several types of multimeters). I think you need to set it to the DC "20" setting to measure voltages up to 20 volts in DC, and also plug the red (positive) lead into the hole below the one it's in to measure voltage (or amps below 10millamps). The red one above you have it plugged into is just for measuring amps above 10 milliamps up to 10 amps but doesn't measure voltage if I remember right. Also, a tip- whenever measuring voltage of unknown heights always start with the highest voltage setting to avoid blowing the meter and then lower it to a scale it's reading within to see a more accurate number. And, if measuring AC voltage there are different settings for that on the dial that you'd use instead of DC. DC for batteries, though.
Also, another tip...When using the ohm meter function to measure resistances NEVER do that if a circuit is energized or it might blow the meter. As a rule whenever measuring resistance in a circuit it must be de-energized.
I've got a couple of those cheap meters that I modded with an internal shunt for measuring amps above the 10 amps it can handle. I use it to measure the amp draw of various props and electric brushless motors on my electric RC planes when building them. You never want to over amp the motor by using too aggressive of a prop, and also don't want to over amp a lipo battery as it can destroy it or cause it to get very hot. Worked like a charm, and much cheaper than buying a commercial watt meter to do that. Watts can easily be figured by knowing the amps and voltage of the motor, but I prefer measuring the amps as it's easier for me to remember the amp limits of a motor or battery.
Also, another tip...When using the ohm meter function to measure resistances NEVER do that if a circuit is energized or it might blow the meter. As a rule whenever measuring resistance in a circuit it must be de-energized.
I've got a couple of those cheap meters that I modded with an internal shunt for measuring amps above the 10 amps it can handle. I use it to measure the amp draw of various props and electric brushless motors on my electric RC planes when building them. You never want to over amp the motor by using too aggressive of a prop, and also don't want to over amp a lipo battery as it can destroy it or cause it to get very hot. Worked like a charm, and much cheaper than buying a commercial watt meter to do that. Watts can easily be figured by knowing the amps and voltage of the motor, but I prefer measuring the amps as it's easier for me to remember the amp limits of a motor or battery.
Critterhunter
New member
That's around peak for a nimh, but write the # down and check it in an hour. Same voltage or lower it's probably peaked. Check again in another hour. Same voltage or lower and it's done.
John,Critter is correct.Try with a nine volt battery to check it should read 9.24- 8.75 as an example. HH Ron
Critterhunter
New member
If that second voltage number you listed was an hour later then the pack is done charging probably. There are minor dips in voltage during the charging process so I'd check it again in say a half hour after the first lower or same voltage is seen from the previous one an hour before...In other words, say 13.5 volts first checked. An hour later it's 13.2. Check again in a half hour. Is it lower or the same? Then it's done. Or is it say 13.6V now? Then you probably saw a minor dip in voltage during the charging and it's still charging. Check in another hour. Is it higher than 13.6V? Probably still charging. Check again in an hour. If you see the voltage sitting about the same or has dropped with two consective checks about an hour apart then for sure it's peaked. The voltage will start going down and continue to once peaked, and then it will reach a point where it pretty much stops dropping and just sits there or hovers around that number and never really climbs much again if at all. That's when it's peaked.
With the low trickle charge rate of the wall transformer it won't hurt to overshoot the charge time by an hour or two or so, so don't get frantic about noticing as soon as it's peaked. You've got time to play and figure out if it's really done. It's only when charging at high amp rates (say 500ma or higher) that overshooting a peak and continuing to charge can start to quickly do some serious damage to a battery. That's why it's important to know how to set the m/v threshold setting for nimhs or nicads properly on some chargers that allow you to do that. If you are say charging at 1C or so and the m/v setting is set way wrong the charger might never see the peak (a drop in voltage of a certain amount) to know the pack is done. That's when excessive sitting on the charger can cause a fire risk if the amp rate is higher than the trickle rate of the Minelab wall transformer.
When the pack is peaked, did you notice if the green light on the GT pack got dimmer or went out? I think they just get dimmer to indicate the charge is done. Never will I understand why detector companies don't ship a halfway decent charger that clearly indicates when a pack is done charging. Makes no sense.
All that being said, I believe the GT charging circuit inside the pack (and on the Elite) *might* terminate the charge when it's peaked (thus the dim or light that goes out), and so the charge is cut off. Still not sure about that though. I do think though that older Sovereigns and the Excaliburs had no charging circuit, or at the most just a thermister to open when the pack got hot (being over charged) and a diode (to prevent reverse voltage flow should the wall transformer be unplugged from the wall but still plugged into the pack...the diode will prevent the battery from being drained by the transformer).
With the low trickle charge rate of the wall transformer it won't hurt to overshoot the charge time by an hour or two or so, so don't get frantic about noticing as soon as it's peaked. You've got time to play and figure out if it's really done. It's only when charging at high amp rates (say 500ma or higher) that overshooting a peak and continuing to charge can start to quickly do some serious damage to a battery. That's why it's important to know how to set the m/v threshold setting for nimhs or nicads properly on some chargers that allow you to do that. If you are say charging at 1C or so and the m/v setting is set way wrong the charger might never see the peak (a drop in voltage of a certain amount) to know the pack is done. That's when excessive sitting on the charger can cause a fire risk if the amp rate is higher than the trickle rate of the Minelab wall transformer.
When the pack is peaked, did you notice if the green light on the GT pack got dimmer or went out? I think they just get dimmer to indicate the charge is done. Never will I understand why detector companies don't ship a halfway decent charger that clearly indicates when a pack is done charging. Makes no sense.
All that being said, I believe the GT charging circuit inside the pack (and on the Elite) *might* terminate the charge when it's peaked (thus the dim or light that goes out), and so the charge is cut off. Still not sure about that though. I do think though that older Sovereigns and the Excaliburs had no charging circuit, or at the most just a thermister to open when the pack got hot (being over charged) and a diode (to prevent reverse voltage flow should the wall transformer be unplugged from the wall but still plugged into the pack...the diode will prevent the battery from being drained by the transformer).
Critterhunter
New member
For sure it's done, your voltage has dropped every time you checked it. Stick a fork in it 'cuz it's done. 
I wouldn't go so long between checks. An hour or so and see if it's the same or has dropped. If it has, check it in say another half hour. Same or lower then for sure it's done. You just want to be sure you don't check too often to where the voltage might drop a little due to the normal charging process but is still going to climb again. By the sound of how often (or less often I should say) you checked, it's done for sure.
And, did the bulb dim or go out on the pack? We need that info for the battery sticky.
I wouldn't go so long between checks. An hour or so and see if it's the same or has dropped. If it has, check it in say another half hour. Same or lower then for sure it's done. You just want to be sure you don't check too often to where the voltage might drop a little due to the normal charging process but is still going to climb again. By the sound of how often (or less often I should say) you checked, it's done for sure.And, did the bulb dim or go out on the pack? We need that info for the battery sticky.
Critterhunter said:For sure it's done, your voltage has dropped every time you checked it. Stick a fork in it 'cuz it's done.
And, did the bulb dim or go out on the pack? We need that info for the battery sticky.
The light never dimmed. Stayed the same brightness from start to finish.
Critterhunter
New member
Wow, that throws a monkey wrench into the works. Anybody else say the same, or see it dim, or go out? Man, 2:41 AM...I need to get to bed.