Hi guys, I just bought a 12 Volt motorcycle battery to begin my mid-power rocketing. Its not too heavy and supposed to have 400 cranking Amps. I charged it up on my trickle charger for the 14 recommended hrs, (yes, I put the right amount of acid in the cells) and today I went to try to burn an igniter. I bought the Mercury Igniter Lighter. And nothing happened. So I went to see if the new battery had any charge in it. I got out my multimeter and can't get any reading. I replaced to 9V battery in the meter. I've got the red lead in the 10ADC position and the black in the common. the meter is set for 20 DCV? Is this right? I get nothing! The Ohms is working on the meter. The trickle charger started at 6 Amps last night and was on 0 this morning. I assume the battery took the charge. I also had the battery on a piece of wood. Again If I knew how to check, I would at least know if I have power from the new battery. Should I just take to battery to an auto shop and have them test it?
how to use a multimeter?
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Necromancer
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The red lead should be in the Positive Input connector, not the 10ADC connector as this is for measuring current (its basically a short circuit across a shunt resistor internally in the multimeter. The 10ADC is for current measurements only, and since you had this connected across the lead acid battery, you likely blew this circuit (or fuse if it has one)
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This is the correct position - V for voltage
thanks for your reply, I'll check the battery after dinner. OK! so we have the full 12.77 Volts the battery is supposed to have!!! Thank you!!!! Now I know more about this Multimeter. So why no Igniter?? How can I test my new Igniter Lighter with the multimeter?
Necromancer
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Check the igniter with your Red on V(ohms), and set to ohms. This will measure the resistance of the igniter.
If its open, you won't get any measurement. A dead short will be the same resistance as if you touched the leads together by themselves.
Depending on igniter, you should probably get somewhere between 1 and 5 ohms.
If its open, you won't get any measurement. A dead short will be the same resistance as if you touched the leads together by themselves.
Depending on igniter, you should probably get somewhere between 1 and 5 ohms.
bobkrech
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12.77 V is low for a fully charged battery. It should be between 13.5-13.8 volts.
1.) Many new battery chargers are too smart for their own good. They check the battery voltage before they activate the charging cicuit. Usually if the battery voltage is below 10 volts, they assume the battery is frozen and will not charge it. If this is the case, you can get it over 10 volts by charging it from your car battery using the jumper cables: positive to positive, negative to negative.
2.) Most usually have 3 inputs: Positive (red), Negative 9black) and 10 A (red). Whenever you are measuring voltage or resistance you only use the positive and negative terminal. For low current measurements you also use the positive and negative terminals. For higher current measurements you use the 10 A and negative terminals.
3.) DVMs are not designed to measure the current or the resistance of large lead acid batteries. Attempting to do it may destroy the DVM or at a minimum blow the fuse.
4.) To measure the battery voltage set the meter to 20 volts DC full scale and put the red wire on the positive terminal and the black wire on the negative terminal.
5.) Next time you'll find that it's simplier to use a 4 to 7 AH gell cell battery to power a launcher than the motorcycle battery. It's ready to go and you never have to add acid or worry about leaks.
Bob
thanks for your reply Bob, the instructions for the battery say 12.7 Volts is fully charged. I go with it for now. I'll get a proper gel cell when I learn more. I'm building a carrying case for the motorcycle battery today. I still am trying to get the Igniter Lighter from Mercury Engineering to work. I'll mess with that after I finish a masking job I'll into at the moment. I love my summers, nothing to do but build and paint and play! Now I would go launch if I could get this thing to work. I've got 2 larger birds that have never been up.
Necromancer
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Sorry, thats incorrect.
For a fully charged battery, the voltage is nominally about 12.7V. Its usually about 2.10V to 2.13V per cell.
13.5 to 13.8 volts is what the voltage would be if it was under charge with a charger.
Mikus_Superfly
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bobkrech
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You are correct. The voltage I gave is a typical floating charge voltage value, and what you might read just after you remove the charger. You will get a much lower voltage value after the battery rests.
No load volts State-of-Charge in %
12.65V 100%
12.45V 75%
12.24V 50%
12.06V 25%
11.89V or less Discharged
Note: Test the battery at room temperature. Allow 4-8 hour of rest after charge or discharge.
This is a good on-line reference of Pb-acid batteries.
https://www.batteryuniversity.com/partone-13.htm
Bob
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