ENGEL-<span class="highlight">POWER</span> PACK QUESTION

And I should add that the power pack should be sufficent to start your vehicle - and a 17Ah pack may not be sufficient to start many vehicles.

A 17Ah pack will never start your Navara TD. Diesels need a much bigger pack.

We use a 24ah power pack at work to start everything. 4 litre cummins deisel loader easy, 7 litre 130 hp diesel tractor a little slower but always starts it.

"You'd do better with an 80 amp AGM which you could pick up for under $200. Ideally it should be run through an isolator, but even simply plugged into a cig socket whilst driving will give it 8 or so amps per hour."

Hi Jimbo,
that woud be nice if all you had to do was hook it up with a cig plug - but its not that simple. The AGM will happly accept a lot more than 8 amps at alternator voltage of 14.2v. Most likely it will want 30+amps, so the fuse will blow. Theres nothing in that circuit that will limit current. Theres no way around proper wiring and isolator.

Cheers
Phil

The battery will "want" whatever it needs. If it only lightly discharged then it will recharge at a lower apmereage than if it was heavily discharged

Hi Gary,
I think we are in agreement!
I recharge batteries through a power supply which has an ammeter, so I can see what's going in - most "lightly discharged" batteries will happily accept 10-15amps @13.8v when first hooked up. After that theres an exponential reduction in current. A battery thats discharged to 50% will happily accept over 30 amps initially.

cheers
phil

Phil,

I'm not sure you're right about the battery drawing too much and blowing a fuse. I'm not sure you're wrong either, just quietly.

I've charged my 100 amp AGM on a 4 amp battery charger which works just fine. It does not seem to try to drag more than the 4 amps from the charger and overload it. I am thinking it would be similar with a cig socket. If there is 10 amps available, the AGM will accept that.

To my way of thinking (and I'm no expert), a battery is not a current drawing device, thus it incurs no load as such. It is moreso a reservoir of power that accepts whatever is put into it. That is too say it may have an ability to accept 50 amps, rather than it is drawing 50 amps.

Just my understanding.

Pity so many clowns gave Collyn Rivers the chits, otherwise he would be around to solve it for us.

Cheers,

Jim.

Jim,

I can understand why 12 volts can be so confusing!! But I can assure you that I'm correct here. No matter what we do, you can't alter Ohm's Law (V=iR).

A 4amp charger will NEVER put out more than 4 amps. If you put a bigger load than 4 amps on it (say your 100Ah battery) the voltage supplied by the charger will drop because its not keeping up. Or depending on the charger, it may also have an overload cutout.

A cig socket is different - its attached to the vehicle's battery and alternator which are capable of delivering hundreds of amps (such as when you start your vehicle). So if you hook it up to your AGM battery, and start up your vehicle, so 14.2 volts is now supplied to the cig socket, then the very low internal resistance of the battery will easily accept much more than 10amps, and will blow your fuse. Your fuse may also blow as you crank your vehicle.

There are many on this forum who are well versed in electronics. Theres no solving required on this one!

Cheers
Phil

Jim,
Just to help clear up what happens after you start your car.

#1 Your alternator/regulator will supply a constant 14.2 volts, almost all the time. Just hook up a voltmeter to your battery if you don't believe me.
#2 14.2 volts is 1.6volts greater than the resting voltage of your battery (say 12.6volts) - so current will always be flowing from your alternator to the battery.
#3 The amount of current that flows into your battery depends on the Internal Resistance of the battery (many factors affect this) and the 1.6volts difference.

Its simply Ohm's Law: Voltage= current x resistance.

A discharged battery will have a low internal resistance and a high voltage difference, so it will accept a heap of current. As it becomes charged, the internal resistance rises and the voltage difference falls, so the amount of current going into it will taper off. Eventually when it is fully charged, it will only draw less than 1 amp from the alternator.

Your battery is a "load" on the alternator while it is being recharged. Same as the headlights are a "load" on the alternator because they draw current. Your alternator has no control over how much current is dished out - it merely provides the 14.2 volts and its the internal resistance of everything else (battery, globes, wiring etc etc) that determines current flow.

Cheers
Phil

Hi..
The morale is: Never plug in a battery to charge from the lighter socket, even a 17Ah one can blow the fuse easily when it is flat, unless there is some current limiting.
Cheers

OK Phil,

Bear with me, I'm just a simple man.

This I have experienced. I have a 600 watt inverter. I have run a 500 watt drill from it. I tried to run a 900 watt chainsaw from it and the chain didn't move. My wife runs her 1500 watt hair curler from it, but it does not get as hot as when plugged into 240 volts at home.

Why is this so? (Apologies the the late Julius).

It was explained to me that the chainsaw has en electric motor that needs 900 watts to run. However the hair curler has a simple element in it that is a resistance device and that 600 watts will heat the element, albeit not to its full capacity. Hence the hair curler will accept whatever is available and not try to draw any more, thus not overloading the inverter.

My understanding (and it's only my understanding), is that batteries do not draw current, they accept it.

Anyway, that was my thinking.

Cheers,

Jim.

The current that a battery draws is dependant only on the voltage across its terminals (at a particular temperature and state of charge).

That current will vary greatly with voltage - if I apply 12 volts to a 50% charged battery it will draw no current - if I apply 14 volts it will draw lots of current.

And there lies the problem with the Ciggy socket. You can bet your bottom $ it will go to around 14V once the on-board battery is full. Even your garden variety 7Ah Gel cell will manage to blow the fuse if you connect it while it is flat and the engine is running.

As for your chain saw, Jimbo, it sounds like it may have an induction (not brush) motor. These can draw more than 3 times the rated current on startup. That's what knocks your inverter out.

Cheers

"batteries do not draw current, they accept it"

Jim,
I have no idea what you mean here. Can you explain?

Batteries have current flow in when being charged and current flows out when being used. Does it need to be any more complicated than this?

Regarding the inverter, which is a separate issue, your drill worked because the surge current of the drill was less than the surge of the inverter (probably about 1000watts on yours). Your chainsaw needs more current than your inverter can supply so it didn't run. As you've said, the hair curler is simply a resistor - so it will just work poorly.

Back to the original issue, you can't charge a 100Ah off a cig socket in your car without blowing the fuse :-)))) There is no limiting on the current apart from blowing the fuse.

Cheers
Phil

I'm buggered if I can understand all this theory.

Over the weekend I'll drain my AGM and then hook it up to a cig socket to see what happens.

Be clear, I'm not doubting anyone. I just need to find out the facts (as they happen in the real world as opposed to theory) and judge for myself.

Thanks to all for their input.

I'm glad we're all still friends and this has not degenerated into name calling.

Hi Jim,

If I left your original post alone, others will follow your suggestion - at best they will only blow the fuses - at worst they can cook some wiring or the socket.
Its best not to post suggestions that you haven't done yourself, or know about.

Yes, you are still doubting the unanimous advice you've been given! Thats why you started another thread and sought a 4th and 5th opinion.
The people who have posted responses are all experienced with DC and are in the "real world".

We are all just trying to be helpful, as we can see that you are struggling to understand stuff which can be quite confusing.

Cheers
Phil

Here's some more theory :-)

Stage 2 of Three Stage Charging applies a constant voltage to the battery (usually 14.4 volts) and the current drawn progressively reduces as the charge builds up.

Stage 1 limits the current to 25% of the capacity (20 amps for an 80 amphour battery) by keeping the voltage below 14.4 volts. This stage is necessary for longer battery life. The current usually drops below 25% C (and Stage 2 starts) when charge level reaches 50 to 70% full.

So this tells me that if the charge is below 50% and you apply 14.4 volts the current will be at least 20 amps.

Of course if you use long thin wiring, then the voltage AT THE BATTERY will be less than 14.4 volts, so the current will also be less.

Sorry Phil,

But I'm not sure you're right. You may well be, but alas I need real world experience.

Don't take it personally, I'm not easily convinced.

Just by the way, I have charged batteries (wet cells admittedly) in the boot of a car via a lead to the cig socket. It worked well, hence my suggestion of doing it with AGM's. I could be wrong with AGM's, but I'll test it rather than rely on theory.

Thanks all the same.

Cheers,

Jim.

Quite right !

Glad we could help.

What do you drive, have you thought about a dual battery setup ?

Agree, The 17a/h units have there place in life......either as a back up starter for a small car or they are very good for using to power a 1amp flouro light around the camp fire etc.

I have a kit for the D40

Give me a ring.

Do you have one for a Heritage Listed 91 NG Paj with the V6 Petrol? There is not a lot of space under the bonnet.

Thanks

Pete

Hi Pajman,

You will have to go for my 'FLYER' Universal Dual battery system.

Pajman Pete , piranah has a tray for your model ,not cheap at round the $120 mark ,involves shifting the emissions canister from pas side to drivers side ,dray takes upto N70 size. ,,sourced the tray through TJM.

Thanks guys. I hadn't thought of moving the cannister. There is not a lot of room in there!

Cheers

Pete