Ammeter guage with sender?

[rcx106]

All the ammeter guages I've seen require that a heavy guage cable runs to the ammeter guage, ie the full current goes into the cabin to go through the meter. I don't really want to do that and it doesn't seem sensible. I've found one guage that uses an inline sensor. And I've heard of guages that just have some induction sensor that goes around the battery cable to sense current. But can't find one! Anyone know?

[ch427]

Its called a current transformer or ct for short and is basically situated around the cable, i dont know of any car ammeters that use this arrangement though.

[rcx106]

I always ask too soon, I Google _inductive ammeter_ and found half a dozen car ammeters that use an inductive pickup.

[buzzer]

I have used one for years... the clip on type like in the link below. Its great for checking the output of the alternator... Not that accurate though, but a good indicator of what's going on. remember they swing both way (oh er) depending on which way round its connected. Best to put it on the battery lead, switch the lights on to see which way its discarding, and then start the car. the needle should go the opposite way if its charging OK.

http://www.ebay.co.uk/itm/Durite-Ammeter-Clip-on-I...

[rcx106]

Ah, inaccurate? Maybe that's why lots of them still use a shunt. I want to monitor how much power is being used from the battery and how much from the battery, when powering a fully loaded 4x4 winch. Reason being that I want to balance the battery and alternator size to get max effect at min weight (ie I don't want two batteries like everyone else if I can avoid it). I've only found one auto ammeter which can handle the output of my upgraded 110A alternator. And only marine ammeters can handle the 220A that my winch will draw. So I'm now looking at non auto ammeters, just regular meters that can be temporarily connected.

[Dogwatch]

Many years ago when I used to build 3-phase welding sets they used an ammeter and shunt for obvious reasons. They were supplied to us as calibrated sets rather than just a batch of shunts and the same number of ammeters.

[Mr2Mike]

ch427 said:

Its called a current transformer or ct for short and is basically situated around the cable, i dont know of any car ammeters that use this arrangement though.

That's because you can't use a current transformer for DC current. You can use a hall effect sensor though.

[Doctor Volt]

Ah, inaccurate? Maybe that's why lots of them still use a shunt. I want to monitor how much power is being used from the battery and how much from the battery, when powering a fully loaded 4x4 winch. Reason being that I want to balance the battery and alternator size to get max effect at min weight (ie I don't want two batteries like everyone else if I can avoid it). I've only found one auto ammeter which can handle the output of my upgraded 110A alternator. And only marine ammeters can handle the 220A that my winch will draw. So I'm now looking at non auto ammeters, just regular meters that can be temporarily connected.

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You are making a big mistake and will end up doing much work for no benefit
Fitting and wiring an Ammeter will be of no use to you, the current draw figures that you get from a hard wired Ammeter will never be constant due to the battery condition varying so much depending on vehicle electrics used, summer/Winter driving and so on,. Even if you were to wire in a Ammeter what do you intend to do once you have built up a current draw to conditions table over a period of time
You will gain nothing from the knowledge that you gain from studying a ammeter
Should you acquire the current draw figures from the winch manufacturer you will then have as much information as you need, the current draw figures from a manufacturers datasheet will tell you more than a Ammeter and you will have not wasted all that time wiring up a heavy shunted meter. Are you aware of the cable gauge that will be required to wire up a Ammeter for your Winch/Alternator and that if one connection is dodgy you will lose most of your vehicle electrics and possibly blow the Alternator diodes

Your idea is a no go IMO

The correct way of going about things is to -

1) Wire your winch to the vehicle battery and use it as and when required, you will soon know if you have a problem - sluggish starting will be the first sign, time will be the test using this method.

2) BEST WAY - Fit and wire a 2nd Battery with a split charge relay for Winch use and nothing else and the job is a goodun

I hope this helps

[rcx106]

Thanks Doctor Volt. What I want to know is how much power the winch takes from the battery and how much from the alternator. It's much curiosity but also I've fitted in a fat heavy alternator only to be told later that the winch will primarily take power from the battery and not the alternator (though two engineers have told me opposite stories).

Anyway, RS Componants do heavy duty ammeters for little over a tenner each so I'll connect them up temporarily and see. I've given up the idea of a cabin ammeter because it's too costly and too much effort. If most power is taken from the battery then I don't see the point of a fat heavy alternator if all I get is faster battery recovery which I don't need. So I'll revert to my stock alternator and fit a bigger battery instead.

[Doctor Volt]

I've fitted in a fat heavy alternator only to be told later that the winch will primarily take power from the battery and not the alternator (though two engineers have told me opposite stories)

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The Winch Motor will only draw current from the Battery
After operating the Winch Motor the Alternator will recharge the Battery to full capacity
Two Engineers have given you incorrect information
Fitting a higher Amp/Hour Battery is a good choice if you will not be using the Winch day in day out (an option I overlooked)
If you are using the Winch often, the Alternator may struggle to recharge the Battery to full state if you are not travelling long distances after using the Winch, if this is the case you will benefit from my best method posted above

Good luck - Happy Winching

[Mr2Mike]

rcx106 said:

Thanks Doctor Volt. What I want to know is how much power the winch takes from the battery and how much from the alternator. It's much curiosity but also I've fitted in a fat heavy alternator only to be told later that the winch will primarily take power from the battery and not the alternator (though two engineers have told me opposite stories).

This depends on the current capacity of your alternator and the current drain of your winch. With the engine running, the alternator will supply the entire electrical system with current up to the point that demand exceeds the alternators capacity. From that point, the extra demand will be taken from your battery.

For instance say you have a 100 Amp alternator and assume the ECU, fuel, ignition and dashboard etc. takes 20 amps which leaves 80 Amps of reserve. If your winch takes 100 amps (for instance) then 80 amps will be delivered by the alternator and you'll be drawing the other 20 amps from the battery.

[rcx106]

So two offline engineers have said these two opposing stories (as far as I understand it)

One says that the alternator, providing it's turning fast enough, will generate the higher voltage. Whereas the battery voltage drops under load, meaning that most of the power will come from the alternator. This is what I hope is true as a bigger alternator is lighter than a bigger battery, and I've already fitted a nice 110 Amp alternator

The other engineer says that in his experience, a lead acid battery is better at providing instant power on demand and thinks that's where most of the power will come from.

[Mr2Mike]

rcx106 said:

So two offline engineers have said these two opposing stories (as far as I understand it)

One says that the alternator, providing it's turning fast enough, will generate the higher voltage. Whereas the battery voltage drops under load, meaning that most of the power will come from the alternator. This is what I hope is true as a bigger alternator is lighter than a bigger battery, and I've already fitted a nice 110 Amp alternator

The other engineer says that in his experience, a lead acid battery is better at providing instant power on demand and thinks that's where most of the power will come from.

Just noticed that you specified that your winch takes up to 220 Amps a few posts up. Clearly your 110 Amp alternator will be completely inadequate to power the winch at full load, in which case you will be pulling a very hefty current from the battery. This will likely be ok if you only ever use the winch at full load for very short periods. For longer periods of operation you are either going to need a larger alternator or size the battery for the expected load.

[rcx106]

The winch I bought in the end is 190A at full load. I know that at full load the battery will at least need to be contributing. I'm just curious where the power primarily comes from under normal use (maybe half load, so ~95 Amps)

[Mr2Mike]

rcx106 said:

The winch I bought in the end is 190A at full load. I know that at full load the battery will at least need to be contributing. I'm just curious where the power primarily comes from under normal use (maybe half load, so ~95 Amps)

Provided the engine is running then any power draw from the electrical system will be provided by the alternator, up to it's current limit. Past that limit, additional current will be drawn from the battery.

The engine management systems (injection, fuel pump, ECU etc.) require some power to run, as well as any other electrical peripherals that may be running (e.g. cooling fan, lights) so you won't actually start with 110 Amps available from the alternator. Also note that the alternator is almost certainly not capable of delivering it's full rated output with the engine at idle.

[Zad]

Check the performance graph for your particular alternator. At or just above idle speeds, output can be pretty restricted.



Obviously, it also depends on the pulley drive ratio.

[Doctor Volt]

There seems to be some confusion here

My posts all revolve around (excuse the pun) your vehicle engine being stationary when you use the Winch, now I do appreciate that yourself and many others will have witnessed recovery vehicles etc having their engines left running while winching or jump starting - Vehicles are left running due to the operator having little confidence in the recovery vehicle electrics and being concered about himself needing recovering should he stop the engine and end up with a flat battery

When a Winch is fitted to a vehicle and that vehicle is maintained properly there is no need to leave the vehicle running when winching unless the winching distance is much longer than the winch cable length such as a vehicle has gone off road and halfway down a Mountain

Also you should consider the high surges in load on the Alternator if leaving the engine running

As long as you wire your Winch to a good Battery you will not need to leave the engine running
I have never ever left my recovery vehicle running and have never had a problem

Confusion is now over - The engineers that advised you about the Alternator doing the work are wrong - How can the Alternator be doing the work if the engine isnt running?

A poster above mentioned about the lack of Alternator output when the engine is at idle speed - The above posters observation is correct, you will struggle to rev the engine and operate the winch, this then leads to you having to fit a hand throttle to your vehicle so as to be able to increase the revs when winching, yes the cost and work is going up and up and for what?

A good fully charged Battery, a good winch motor and suitable Alternator should do the job (no engine running), all recovery vehicles should have 2 x Batteries and a split charge system, then there would be no need to leave engines running

I hope this helps