AMPAGE TESTING (12 Volt DC)

[Geordie Spark]

I used to wonder what a masochist was but now that I know I'm now left wondering if the masochist here is the OP for returning here to post yet again, or me for reading the post !!!

 

[Geordie Spark]

MATE in 12V or car speak, the abbreviation AMP to most people means AMPLIFIER, hence why I used the WORD "AMPAGE" instead of AMP, no auto electrician sayes "AMPERE" or "AMPERAGE", they say AMPAGE or AMP, but to car drivers, they would/may/might confuse this with car AMPLIFIERS. Hence they'd get confused about power watts and sound watts, hence the substituted full word AMPAGE, instead of AMP(s).

That's all well & good ............ or it would be IF this was a car forum, but it isn't !!!!

 

[srands]

That's all well & good ............ or it would be IF this was a car forum, but it isn't !!!!

Yer well not all 240V ac electricians know about 12V dc, and besides this forum isn't called ELECTRICIANS FORUM (Not Auto or 12V dc, just 240V ac), is it, no!

 

[Des 56]

MATE in 12V or car speak, the abbreviation AMP to most people means AMPLIFIER, hence why I used the WORD "AMPAGE" instead of AMP, no auto electrician sayes "AMPERE" or "AMPERAGE", they say AMPAGE or AMP, but to car drivers, they would/may/might confuse this with car AMPLIFIERS. Hence they'd get confused about power watts and sound watts, hence the substituted full word AMPAGE, instead of AMP(s).

Unusually, this an explanation (to something that you posted) that can be described as reasonable ,even if not agreeable,so thanks for that

 

[srands]

Here is the LONG version (After reading the 1st post SHORT version, thought I'd beef it up with some more data, details, etc):



PICTURE VERSION: WORD VERSION:
TOOLS NEEDS: MULTIMETER, SCREWDRIVERS & BLOCK CONNECTORS

This is quite simple see following pictures, the MultiMeter in this instance (DRAWN, POSITIVE TERMINAL) tests the AMPAGE between the POSITIVE SUPPLY (red probe lead) and the POSITIVE LOAD (black probe lead), this is known as breaking the circuit. Hence the NEGATIVE is uninterrupted from SUPPLY to LOAD (In other words, leave it alone). In this instance the positive supply has croc clips, normally I'd use insulated BLOCK CONNECTORS:

PIC1 (multimeter measuring AMPAGE between POSITIVE supply & POSITIVE load)


PIC2 (12V dc Battery Charger powering car cd player, with MultiMeter Testing AMPAGE)


PIC3 (CAR CD PLAYER in house install powered by CAR BATTERY CHARGER 12 V dc 4A)


PRECAUTIONARY NOTEs:
~ Obviously the NEGATIVE and POSITIVE can NOT touch each other (Neither SUPPLY or LOAD)
~ If your MultiMeter has NEGATIVE READING, your PROBE LEADS are the wrong way (Or ignore negative symbol, as AMPAGE figure is accurate).
~ The 12V dc MOTOR/PART or ALTERNATOR/SOLAR PANEL may CHARGE/DRAW a greater AMPAGE/CURRENT then the capacity of MULTIMETER & its LEADS (At this point the actual ampage is unknown). Eg: Most car electrical parts are low current (Indicators, elec windows, elec sunroof, heater, etc), with the obvious exception of a car starter motor (Extremely high ampage/current, totally unsuitable for testing with MultiMeter). Hence if 12V dc part/motor or charge rate of power supply is greater then 10A this may melt your MultiMeter probe leads and/or break the MultiMeter (Unless you have a 20A DC MultiMeter! Obviously the ampage max of those is 20A DC).

OTHER NOTES:
~ The AMPAGE reading of your MULTIMETER, is given by testing 'A' POSITIVE or 'A' NEGATIVE, however the AMPAGE reading is total AMPAGE drawn/charged, so this figure should NOT be doubled in your calculations.

~ My preferred practice/method, & the MOST accurate, is to connect new leads to the battery terminals, so there won't be any other registered ampage drawn from the car battery. So the ampage reading is what it is! (PS. Don't mess about from behind the car fusebox, keep it simple, either direct from car battery and loom OR new power leads from car battery to motor/part/device/appliance your testing with a MULTIMETER.)

~ Alternatively (The least preferred, & least accurate) If you're testing direct from a car battery and it's loom, it may have other parts/motors draining ampage, such as indicators/wipers, etc. So turn ON the ignition (WITHOUT STARTING THE CAR, as the ampage drain would be far too great for the MULTIMETER & PROBE LEADS!), then make a note of what the standard ampage drain is approximately (i), then turn on the motor/device/appliance you want to test (ii). Then subtract the standard ampage drain from the new figure with the appliance/device/motor on to EQUAL the difference (iii) i.e. The ampage of the motor/part etc.


FOR EXAMPLE:
i) STANDARD AMPAGE DRAIN = 0.5a (Car alarm or something else)
ii) STANDARD AMPAGE DRAIN & OTHER MOTOR = 1.5a
iii) CALC 1.5a - 0.5a = 1.0a

This guide is a quick reference when testing 12 Volt DC circuits with a MultiMeter, EITHER: ~ ampage CHARGE to batteries OR ~ ampage DRAWN from batteries.

Why test for AMPAGE? To determine what cable/lead thickness to use, and bigger is always better (Future proof, as you may add more devices to that circuit load). See rough guide below for 12v dc twisted wire (Not Socket wire):

CABLE SPECIFICATIONS for DC 12 Volts
THICKNESS (Either ~ Individual insulated wire thickness in mm APPROXIMATE)	AMPAGE (max of cable/lead/wire)	WATTAGE (max of cable/lead/wire)
2.7mm	3A	36w
3.0mm	10A	120w
3.8mm	20A	240w
5.0mm	35A	420w
6.2mm	50A	600w
1.2CM	AWG8 / 40A	480w
1.6CM	AWG4 / 70A	840w

To calculate correct CABLE/WIRE/LEAD thickness (Or FUSE Ampage) from appliance WATTS:
W = Watts, V = Voltage, A = Amps
W / V = A Eg 10Ws / 12v = 0.8A

Remember this isn’t exact, bigger is always better, thicker cable have less wear & tear overtime, & generally in 12v dc, thinner cable is also inadequate, because the motor/part/device can NOT draw sufficient current from thinner cable.
Here are some good examples, whenever I fit car sound amplifiers, OR large inverters into cars I use AWG8 which has an ampage of 40A, which is far greater ampage then the car sound amplifier or inverters, such as:
~ 40A / 4A (Ampage of an large inverter) = cable 10 times the ampage of the inverter
~ 40A / 20A (Ampage of a 4 channel 400 Watt car sound amplifier) = cable 2 times the ampage of the inverter
Hence fitting much larger ampage cable, then the actual ampage of the device (car sound amplifier or inverter) is common good practice.
To calculate power WATTS max for circuit (If the rest of your system is specified in 12V Watts rather then 12V Ampage):
W = Watts, V = Voltage, A = Amps
A x V = W Eg 20A x 12V = 240Ws (Power Watt’s NOT sound Watt’s)

TYPICALLY AMPAGES OF MOTORS/PARTS/DEVICES:

AMPAGE (12V dc) rated P/H given as multimeter instant reading	PART
1A to 1.6A (Depends on music played!)	CD/MP3 PLAYER
3A to 20A+ (Depends on the music being played!)	car sound AMPLIFIER 400 Watts 4 Ch
0.01 A	CAR CD PLAYER AMPLIFIER REMOTE
0.03 A	4 WAY CIG LED MULTI ADAPTOR
0.60A (Maximum 0.70A)	PORTABLE DVD PLAYER
2.3 A	CAR INVERTER CAN
5.3A to 6A = Charging Laptop (inverter on = 0.4A, inverter off = 0A)	CAR 12V to 240V 1000 Watt Inverter
0.28 a	MOBILE PHONE CHARGER
0.05 A	SATELLITE NAVIGATION
0.06 A	BLUTOOTH CHARGER
2.6 A est	FLASK
4.6 A	PUMP
0.20A (Depends on function)	LED LIGHT
12.00A	HEADLIGHTS
0.03A	ALARM DRAIN
3.00A	ALARM CENTRAL LOCKING
0.36A	INTERIOR LIGHT
0.08A to 0.20A	ALARM/IMMOBILISER
6A	HAZARD LIGHTS
8A Each	ELEC WINDOWS
10A +	ELEC SUNROOF

IMPORTANT NOTE: Cable size, the bigger the better (Bigger: Diameter or circumference of the cable).

Remember most MultiMeters (£10 Maplin job ok) only test upto 10A 12V DC, more expensive MultiMeters (UNI-T from Maplin £30 why spend any more) test upto 20A 12V DC.

 

[srands]

Also remember when you are FITTING (Instead of just testing) power cable, remember the circuit should be adequately fused, for example from SUPPLY (Battery Terminal to Fuse, via ring connector to cable) to the LOAD (Cable, then Motor/Device). Remember the fuse rating is lower then that of the cable ampage, hence if the current is greater then the fuse ampage, the fuse will blow, and if the power negative & power positive touch uninsulated then the fuse will blow because of resistance (The touching of opposites, - and +). Remember a fuse is only a fuse (Cheap & easy to replace), how if you don’t fuse a lead, and resistance and/or maximum is exceeded, then wiring looms and/or motors/parts and expensive & hard to replace (Certainly NOT cheap & easy to replace). Hence on my car I have fused separately the positive & negative, for extra security, as I said before a fuse is only a fuse, to replace fuses, are cheap & easy.


CABLE & FUSE example for 2 typical 12 Volt dc devices

	INVERTER	car sound AMPLIFIER
CABLE	40 A	40 A
FUSE	10 A	30 A
DEVICE (Eg Inverter or Car snd AMP)	4 A	20 A

To calculate power WATTS max for circuit (If the rest of your system is specified in 12V Watts rather then 12V Ampage):
W = Watts, V = Voltage, A = Amps
A x V = W Eg 20A x 12V = 240Ws (Power Watt’s NOT sound Watt’s)


TYPICALLY AMPAGES OF MOTORS/PARTS/DEVICES:

PART	AMPAGE (12V dc) rated P/H given as multimeter instant reading
CD/MP3 PLAYER	1A to 1.6A (Depends on music played!)
car sound AMPLIFIER 400 Watts 4 Ch, 2 channels bridged powering SUB & 2 channels for 2 6x9’s	3A to 20A+ (Depends on the music being played! Eg about 20A @ Vol 25)
CAR CD PLAYER AMPLIFIER REMOTE	0.01 A (Constant when amp used)
4 WAY CIG LED MULTI ADAPTOR	0.03 A
PORTABLE DVD PLAYER	0.60A (Maximum 0.70A)
CAR INVERTER CAN	2.3 A
CAR 12V to 240V 1000 Watt Inverter	5.3A to 6A = Charging Laptop (inverter on = 0.4A, inverter off = 0A)
MOBILE PHONE CHARGER	0.28 a
SATELLITE NAVIGATION	0.05 A
BLUTOOTH CHARGER (Nokia)	0.06 A
FLASK with optional warmer	2.6 A est
PUMP 12V	4.6 A
LED GRILL LIGHT IN RED	0.20A (Depends on function)
HEADLIGHTS	12.00A
ALARM DRAIN	0.03A
ALARM CENTRAL LOCKING	3.00A
INTERIOR LIGHT	0.36A
ALARM/IMMOBILISER	0.08A to 0.20A
HAZARD LIGHTS	6A
ELEC WINDOWS	8A Each
ELEC SUNROOF	10A +

IMPORTANT NOTE: Cable size, the bigger the better (Bigger: Diameter or circumference of the cable).

Remember most MultiMeters (£10 Maplin job ok) only test upto 10A 12V DC, more expensive MultiMeters (UNI-T from Maplin £30 why spend any more) test upto 20A 12V DC.

ALTERNATIVELY To test AMPAGE of 240 VOLT ac APPLIANCES use a plug in ENERGY MONITOR (From Maplin).

 

[Knobhead]

No......

 

[Silly Sausage]

:confused5::freak::ciappa:

Is this geezer on drugs?

 

[Geordie Spark]

:confused5::freak::ciappa:

Is this geezer on drugs?

If he isn't then he should be !!!

 

[malcolmsanford]

It's a spiffing read