12v Extension Not Working With Our Tyre Inflator

HKF

HKF

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The Charente, France
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Benimar Europe 740
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Since August 2021
Hi everyone :)

I bought a 12v extension lead ( https://www.amazon.fr/dp/B0C7C3P2L9?ref=ppx_yo2ov_dt_b_product_details&th=1 ) to use with our heavy duty tyre inflator (up to 180 bar) for the MH. When we try to use it, it runs really slowly, then cuts out. Have I bought an extension that's not man enough for the job? If so, can someone recommend one that will work, please? Thank you so much :)
 
Have a look here....basicly the 12v supplied falls as a function of cable diameter and length......longer needs more diameter......

Voltage Drop Calculator | 12 Volt Planet Cable Calculator

Use our Voltage Drop Calculator to select the correct Cable for your campervan, motorhome or boat wiring application. Cable Calculator for Auto and Marine Electrical Components from 12 Volt Planet - Cable Size Calculator
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ianp said:
Have a look here....basicly the 12v supplied falls as a function of cable diameter and length......longer needs more diameter......

Voltage Drop Calculator | 12 Volt Planet Cable Calculator

Use our Voltage Drop Calculator to select the correct Cable for your campervan, motorhome or boat wiring application. Cable Calculator for Auto and Marine Electrical Components from 12 Volt Planet - Cable Size Calculator
www.12voltplanet.co.uk
Click to expand...

Ah-ha, ok, that makes sense :) So, up to now we've used it on the 12v socket in the cab but we also have a 12v socket in the hab. Do you think the one in the hab will be ok to use, or will it not be rated high enough and end up blowing a fuse....or worse?
 
Tyre inflators pull quite a lot of current. With long, skinny wires, it's probably causing quite a lot of voltage drop. Enough for it to flake out.
 
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I extended mine to feed the rear from the dash.
I could blow them up by mouth faster.
Take the extra flex off and ran as it should
Voltage drop 8.16v

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Inflators take 10 to 15 amps that extension you bought will give over a 30% loss at 10 amps so its never going to work.
Best to use the cab socket, hab ones normally only 10 amp max.
 
What make/model of tyre inflator do you have need to know it’s power rating
 
Best not to use sockets at all, use crocodile clips attached directly to the starter battery and run the engine at the same time as inflating your tyres, that way you will have much less voltage drop or none as your alternator will be providing the electricity. And you may need to check if you've blown any fuses in your sockets because as the voltage drops the current increases.
 
ChrisL said:
Best not to use sockets at all, use crocodile clips attached directly to the starter battery and run the engine at the same time as inflating your tyres, that way you will have much less voltage drop or none as your alternator will be providing the electricity. And you may need to check if you've blown any fuses in your sockets because as the voltage drops the current increases.
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You really don't want to use croc clips, dangerous things easy to sparks & arcs & start a fire. I wouldn't want a croc clip anywhere near a Ducato battery positive terminal with all those fuses connected to it.
 
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ChrisL said:
Best not to use sockets at all, use crocodile clips attached directly to the starter battery and run the engine at the same time as inflating your tyres, that way you will have much less voltage drop or none as your alternator will be providing the electricity. And you may need to check if you've blown any fuses in your sockets because as the voltage drops the current increases.
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Nope. As the voltage drops the current drops too.

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tonyidle said:
Nope. As the voltage drops the current drops too.
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Remember that the compressor has a motor in it. Motors require a certain output in watts in order to function, and this is the result of a voltage multiplied by amps. So when voltage falls, resistance scales up in order to supply the difference, and the motor will also draw more current. I learnt this the hard way by doing exactly what the OP did and blowing fuses in sockets, with regard to crocodile clips, if the pump is turned off when the clips are attached then there shouldn't be any sparks and I haven't experienced any with my own high pressure tyre inflator, however it would make a better job of it if you have permanently connected leads with an Anderson socket and corresponding plug on the inflator leads.
 
I have a 12v tyre inflator - the make and model of which escape me (Ring RAC 900 comes to mind but may not be correct) - I understand the emergency services often use the same one. It is supplied only with croc clip cables as the current draw is considered to be too high for accessory sockets. For many years I have used a “free standing” 12v battery (to power the pump) of the type that are often used as standby batteries for intruder alarm systems - current (no pun intended) battery is made by Fiamm and is around a third of the size of a car traction battery. It powers the pump more than adequately and is very transportable. I am mindful of care being required to avoid any electrical “short” and therefore use a small plastic zipped canvas bag with handles for storage. Works for me and also is also useful for remote powering off accessories.
 
I set up a dedicated fused connection with Anderson connectors and put the same on my compressor. I can access it through the passenger door and reach all 4 tyres. 10A fuse if I remember rightly.
 
I use crocodile clips connected to the jump/charging terminals in the engine compartment.
 
ChrisL said:
Remember that the compressor has a motor in it. Motors require a certain output in watts in order to function, and this is the result of a voltage multiplied by amps. So when voltage falls, resistance scales up in order to supply the difference, and the motor will also draw more current. I learnt this the hard way by doing exactly what the OP did and blowing fuses in sockets, with regard to crocodile clips, if the pump is turned off when the clips are attached then there shouldn't be any sparks and I haven't experienced any with my own high pressure tyre inflator, however it would make a better job of it if you have permanently connected leads with an Anderson socket and corresponding plug on the inflator leads.
Click to expand...
The motor doesn't control the current in the circuit. The motor output is derived from the available voltage. The motor represents a load resistance in Ohms which remains constant (although it's complicated by the fact that it is a motor and not a straightforward resistance). So if the load resistance is constant and the voltage is lower than 12 then the current in the circuit will also be lower. Which means that the available motor power will be lower.

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tonyidle said:
The motor doesn't control the current in the circuit. The motor output is derived from the available voltage. The motor represents a load resistance in Ohms which remains constant (although it's complicated by the fact that it is a motor and not a straightforward resistance). So if the load resistance is constant and the voltage is lower than 12 then the current in the circuit will also be lower. Which means that the available motor power will be lower.
Click to expand...
We will have to agree to disagree Tony, if we were discussing a simple resistive load like a light bulb I would agree that amps drop as the voltage drops, but as a compressor pumps up a tyre the load and therefore the resistance increases, if the voltage drops the amps drawn will increase, that is why my tyre pump blew fuses if the engine wasn't running.
 
ChrisL said:
We will have to agree to disagree Tony, if we were discussing a simple resistive load like a light bulb I would agree that amps drop as the voltage drops, but as a compressor pumps up a tyre the load and therefore the resistance increases, if the voltage drops the amps drawn will increase, that is why my tyre pump blew fuses if the engine wasn't running.
Click to expand...
I don't think we disagree. We're approaching it from different angles. As the motor loads up it's electrical resistance decreases and the current rises - to the point at which the circuit fuse may rupture. If the supply leads have sufficient resistance the voltage at the motor will reduce. This reduced voltage in and of itself cannot cause an increase in current. In fact if the voltage continued to fall the circuit current would do likewise.
 
After blowing fuses in the engine bay I now start the inflator before connecting to the tyre valve. This puts a gradual strain on the battery (and fuse) instead of an instant full load.
 

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