AMPAGE TESTING (12 Volt DC)

[srands]

Useful reference guide for AMPAGE TESTING of 12 Volt DC.



PICTURE VERSION URL:
https://blufiles.storage.live.com/y...znmbCQXpJVytYH2xzFs/AmpageTesting12VoltDC.jpg

WORD VERSION URL:
https://skydrive.live.com/view.aspx?cid=9EC5688DD90EEC6C&resid=9EC5688DD90EEC6C!581

TOOLS NEEDS:
MULTIMETER, SCREWDRIVERS & BLOCK CONNECTORS

This is quite simple see following pictures (Much easier to do then first impression on reading instructions), 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). 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, then means you have your PROBE LEADS the wrong way (Or just ignore the negative symbol, as the AMPAGE figure will be accurate).
~ The 12V dc MOTOR/PART or ALTERNATOR/SOLAR PANEL may CHARGE/DRAW a greater AMPAGE/CURRENT then the capacity of the MULTIMETER & its LEADS (At this point the actual ampage is unknown). For example 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 the 12V dc part/motor or the charge rate of the 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 given by your MULTIMETER, is given by testing 'A' POSITIVE or 'A' NEGATIVE, however the AMPAGE reading is the total AMPAGE drawn/charged, so this figure should NOT be doubled in your calculations.

~ 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

Alternatively (my preferred practice/method) 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.

I made this guide as a quick reference when testing 12 Volt DC circuits with a MultiMeter, EITHER:
~ ampage CHARGE to batteries
OR
~ ampage DRAWN from batteries.The main reason for this guide is that I was not impressed (And continue to be not impressed with the lack of meaningful instructions) with uncomprehensive manuals supplied with most MultiMeters. Seems odd to make a great feature but don't explain in the instructions.

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 APPLIANCES use a plug in ENERGY MONITOR (From Maplin).

This guide I'm sure will be a great help to test 12 Volt DC circuits, however please feel free to add these links below (Website addresses, urls, etc), the numerous number of posts on this subject (That I couldn't find), and web references to wiring regulations, and any other derogatory negative remarks you have as well!

CHEERS, AND BELOW IS A FULL LIST OF MY OTHER USEFUL GUIDES & SPREADSHEETS (Top entries of electrical interest)

STEPHAN RANDS
AMPAGE TESTING (12 Volt DC)
RING AMP AUTOCALC: 1ST TAB
LIGHTING CIRCUITS, RING & RADIAL wiring diagrams
UTILITY ENERGY MEGACALC
MPG
METRIC AUTOCALC
PERCENTAGE CALCULATOR AUTOCALC
EXCEL USEFUL FORMULAS
MTB ROUTES IN/NEAR HULL, HUMBERSIDE
TIER 4+ CATEGORY TYPE
TIER 4+ MONEY TYPE
AUTOCALC WEBSITE

 

[telectrix]

now i know what current my windows require, i shall sleep better at nights. however in the morning, i'll still have to use the window winder handle as they're not electric. now i'm just off to the "manual van window forum"

 

[Knobhead]

:confused5::freak::ciappa:

Is this geezer on drugs?

He can have some of mine, I’ve got plenty.

Codeine Phosphate puts me out like a light!
I take zero ampage then.

 

[drew35]

What was the point in that post? Most multi meters only test to 10amps so for anything more they're useless. All you need is an amp clamp multi meter, good for 600amps, or an inductive ammeter they cost pence. But in this technological world you can buy a digital ammeter with fuse adapter on the end for five quid. A lot easy than than mess in the pictures! Stick to stealing car stereos!

 

[srands]

What was the point in that post? Most multi meters only test to 10amps so for anything more they're useless. All you need is an amp clamp multi meter, good for 600amps, or an inductive ammeter they cost pence. But in this technological world you can buy a digital ammeter with fuse adapter on the end for five quid. A lot easy than than mess in the pictures! Stick to stealing car stereos!

Mate, In the 12V dc car/house world nearly every part/motor with the exception of a car starter motor, is less then 10A, the only other common exceptions being high output car sound amplifiers, perhaps some air conditioning units, so a 10A MultiMeter £10 or 20A MultiMeter £30 is more then adequate.

Clamp MultiMeters and PAT testers are useless junk, they are a joke, they're expensive mickey mouse nonsense(Metal conducts, but NOT wirelessly!)

And the other meters, are a waste of time & money (Make a circuit, wait an hour, or average out 10 mins over an hour). I guess your making reference to finding out the ampage of a starter motor, goto Halfords (Or your main dealer) and ask them the part (starter motor) specification, it sayes on the side of the box.

 

[alarm man]

Mate, In the 12V dc car/house world nearly every part/motor with the exception of a car starter motor, is less then 10A, the only other common exceptions being high output car sound amplifiers, perhaps some air conditioning units, so a 10A MultiMeter £10 or 20A MultiMeter £30 is more then adequate.

Clamp MultiMeters and PAT testers are useless junk, they are a joke, they're expensive mickey mouse nonsense(Metal conducts, but NOT wirelessly!)

And the other meters, are a waste of time & money (Make a circuit, wait an hour, or average out 10 mins over an hour). I guess your making reference to finding out the ampage of a starter motor, goto Halfords (Or your main dealer) and ask them the part (starter motor) specification, it sayes on the side of the box.

interesting thread srands,it inspired me to have a bit of a tinker with my own car,tho i think ive bit off more than i can chew...look forward to your help..:uhoh2:

 

[Silly Sausage]

:uhoh2:


View attachment 7834

Hahaha!!! Can't stop laughing now...

 

[Des 56]

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


Why would you want to fuse the negative as well as the positive
A circuit will be disrupted with a fuse in the positive only,adding another fuse in the negative has no benefit,its a waste of time and effort


Some starter motors can draw current upwards to 200 amp and will operate directly from the battery via the solenoid,
If you double fuse everything ,does that "everything" include your starter motor

Using thick cables to overengineer for heavy future loads
Relays and solenoids negate the need to switch the bulk of these loads,localised larger cable is the time tested best method

 

[Knobhead]

srands, would you please go to DIYnot, or did they send you here? I’m sure there’s people there that will listen to you

View attachment 7835

 

[srands]

To comment further on calculating AMPAGE drawn, there was discussion that electric motors are all mostly low ampage (Below 10Ah), with the exception about knowing the ampage of a car's greatest electrical consumption part, a STARTER MOTOR, well goto Starter Motor | Quality Starter Motors for any car (Or your main dealer) and ask them for the parts (starter motor) specification, it sayes on the side of the box, or motor.
Note: If starter motor specification is in KW:
KW / 1000 = Watt's
Watt's / 12 V = A. This figure is an instant, as the starter motor drain is for a second (NOT continuously), then the ignition key is released (Starter motor turned OFF) as the engine is started, then the alternator produces current, recharging the battery, obviously there will be small current drains in Ah from small motors/parts, for example, electric windows, indicators, car cd/mp4/dvd player, lights, fan/air con, etc.

FURTHER DETAIL:

BATTERY & STARTER MOTOR EXAMPLE:
CAR BATTERY: 56 Ah (* 10 = 560 A [EN])
STARTER MOTOR 1.7 KW (/1000 = 1700 WATTs / 12 VOLTs = 142 A [EN])

Obviously the car manufacturer deems what is an appropriate battery Ah for their manufactured car model.

An Amp-Hour (ampere-hour, Ah) is a way of describing a battery's capacity - how long it will run before it is drained down. To be more specific: the amp-hour rating for a given battery is the maximum amperage that can be drawn continuously until the battery is completely flat, over a specific time period.

AH stands for amp hours
10 amp hours =
~ DrAW 10 amps for 1 hour
or
~ Draw 1 amp for 10 hours
Or
~ Draw 11 amps for 54 minutes (0.9 hours)
The faster you draw amps out of your battery the fewer amp hours you get in total, and the shorter the life of the battery.

Ampere-hour - Wikipedia, the free encyclopedia
Starter Motor | Quality Starter Motors for any car

 

[Silly Sausage]

Thanks for link to Ampere-hours, you learn something everyday!
Could you please explain to me kWh, I'm just completely baffled by them?
Thanks in advance
A

 

[srands]

Thanks for link to Ampere-hours, you learn something everyday!
Could you please explain to me kWh, I'm just completely baffled by them?
Thanks in advance
A

This needs explaining from both 12 Volt DC and 240 AC Volt perspective:

12 Volt dc, we're NOT concerned about the cost of electric, because a car alternator generates this for free (Well apart from fuel & wear & tear of car & driver!) as is a by product of engine running (One cog turns, a belt to the alternator, another cog turns, electric produced, power lead to battery, charging battery). Hence the only real preoccupation here is what is the AMPAGE of the PART (If unknown use MultiMeter to determine, see 1st msg in this post)? Once this is known, then specifying the correct THICKNESS LEAD/CABLE and FUSE is one of the only fitment considerations

Calcs (W = Watts, V = Voltage, A = Amps):

1000 W's = 1 KW (In other words W * 1000 = KW)

A x V = W (Eg 0.8A * 12v = 10Ws)

W / V = A (Eg 10Ws / 12v = 0.8A)

Ah x 10 = A (EN) (Eg 56 Ah * 10 = 560 A [EN])

DC 12 Volt Cable Guide
Individual insulated wire thickness in mm with approx max	AMPs	WATTs
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

Note: To power an AC 240 Volt appliance in a car, you need an INVERTER (I'd recommend a very generous maximum margin to power your SMALL appliance, such as I have fitted 1000W Inverter for a 100W LAPTOP!). WHY? Because your laptop voltage is different to your car battery, for example: Car batteries = 12V. My Laptop power = 20V with psu (Power Supply Unit AC to DC). And bigger is always better, as may use USB powered extras (Hard drive, cameras, etc), or may get larger spec laptop.

240 Volt ac, we ARE concerned about the cost of electric, because ELEC is charged by the KW.
Small Appliances are stated in WATTs (This figure is the approx figure IF an appliance is used for AN HOUR, even though the reading on ENERGY MONITORS is instantly displayed. For example a kettle may only be used for 3 mins, and it's max maybe 2200 Watt's, however it's consumption is NOT 2200 Watt's unless it is used continuously for an hour!).
Large Appliances over 1000 Watt's are stated in KiloWatts such as KETTLES, DISH WASHERS, WASHING MACHINES, etc.
ELECTRIC used in houses/businesses is measured with an ELECTRIC METER, and in KWs.
Once again specifying the correct THICKNESS LEAD/CABLE and FUSE is an important fitment consideration. Since appliances already come with a LEAD, the same thickness or bigger is adequate. The FUSE must be greater then the Ampage max of the appliance and the cable lead must be thicker Ampage then the fuse Ampage.
However if fitting new SOCKET RING/RADIAL circuit need to be fitted, consideration has to be given the total max in amps of all applainces using that circuit, hence use appropriate socket wire cable, sockets/fixtures, etc.

AC 240V (Appliance Wire) Cable Guide
Individual insulated wire thickness in mm with approx max	AMPs	WATTs
0.2mm	1A	240w
0.5mm	3A	720w
0.75mmm	6A	1440w
1.00mm	10A	2400w
1.25mm	13A	3120w
1.5mm	15A	3600w
2.5mm	20A	4500w
4.00mm	30A	7200w

AC 240 Volts (Socket/W) Cable Guide
Individual insulated skt wire thickness in mm with approx max	AMPs	WATTs
1mm	15A	3600w
1.5mm	20A	4800w
2.5mm	27A	6480w
4mm	36A	8640w
6mm	46A	11040w
10mm	63A	15120w
16mm	85A	20400w

Want a FUSEBOX CIRCUIT and MCB/RCD calculator? See my spreadsheet MCB/RCD CALC See the 3rd tab (If MCB's are different ampages) or 4rd tab (If MCB's are same ampage)


Calcs (W = Watts, V = Voltage, A = Amps):

1000 W's = 1 KW (In other words W * 1000 = KW)

A x V = W (Eg 5A * 240v = 1200Ws)

W / V = A (Eg 1200Ws / 240v = 5A)

Note: To power a DC 12 Volt appliance in a house, you need either an adequate:
~ AC to DC plug: Maplin stores, Mobile phone stores, or stalls in retail shopping centres)
or
~ AC to DC psu (power supply unit): Maplin stores
or
~ CAR BATTERY

Still need more ELEC/utility calculators? See my very comprehensive workbook spreadsheet (See 1st tab, scroll down) ELEC GAS WATER autocalc: 1st tab, scroll down

 

[Knobhead]

You can’t even recognise sarcasm!
View attachment 7913

 

[Silly Sausage]

You can’t even recognise sarcasm!
View attachment 7913

I bumped into him on my way into Maplins to pick my pre ordred ampage meter.
He's not a patch on his mate srands though, showed me a picture he whipped out of those trousers.

 

[Knobhead]

These ampage meters, are they any good and how expensive are they?

Was it a picture of str**ds.

View attachment 7914

 

[Silly Sausage]

No, that's his shy brother