Power Tools via Inverter and Car Battery

MeatProduct

I am wondering if it is a realistic ambition to run some of my power tools off a 3000watt inverter atached to my land rovers battery? It's a new battery.

The main tool I would be using is an 1100watt circular saw. Can the car battery handle this assuming I have the car running all the time?

Many thanks,

Nick

drunkmonkey

Get a pro to do it, you'll definatly have to fuse the power cable along with a breaker somewhere along the line, even when the car is off the invertert might draw a tiny bit of power, enough to drain your battery over night...

So you need,
Fuse (big one) that's to protect your car in case of a fault
Invertor
Line Breaker - to cut power complelty when invertor is not in use

there's a bit of wiring involved but it should work...

i've all the stuff in my boot ready to wire my own car...

MeatProduct

Thank you very much DrunkMonkey, greatly appreciated bit of advice there, exactly what I needed. I shall go ahead and do this. I've been juggling doing this or buying a generator. Going with the inverter as I can reuse the inverter later for my house.

Is there much difference between efficiencies between the two options are are they pretty much the same deal?

Nick

MeatProduct

I reckon I will buy an addition battery specifically for this purpose, I don't ever want to be left in the situation of not being able to get my car started due to a flat battery in the middle of no where (where I'm building my house).

The inverters I am looking at all have power switches, would I still need a line breaker?

Thanks DM,

Nick

drunkmonkey

That's the idea of the power breaker, it cuts the power completley so there's no drain on the battery when the engine is off..
You'd be best off drop into an auto eletrican, maybe some one working with tractors or machinery would have a better idea..
as I said mine is still in the boot for the last week so it's untested yet but all my reseach and who i've talked to said it would work, if it's work around a house your doing would you not be better off with a fuel powered generator you can move around?

MeatProduct

I do about 90% of my work on a bench so there's no real need for me to be very mobile. I'm willing to put up with the 10% where I'll have to drive the vehicle to where I need the power. It's only a small cabin I'm building anyway.

Please keep me updated on your progress. I will let you know how I fare once I get all the parts I need.

Thank you for your time and advice DrunkMonkey,

Nick

2011

I am not an auto electrician but this is the way I would see it:

If the appliance you want to power is rated at 1100 watts.

Pretend that the inverter is 100% efficient. The 12 volt supply to the inverter will then need to draw a current of 1100/12 = 91.67 amps!!

Can the car battery handle this assuming I have the car running all the time?

No matter what way you look at it, over 90 amps is a large current!! Although the starter motor for your Land Rover draws a far larger current than this (a few hundread amps), it is only for a few seconds. I would think that even with the engine running and everything else electrical turned off you might be pushing your luck!

The question is can the car alternator supply the inverter an average of over 90 amps at 12 volts at all times that you are using the circular saw, because that is what you are asking of it. The battery is great at absorbing large load fluctuations, but ultimately the altenator generates all of the electrical power that is being consumed by the various loads connected to your vehicle.

A battery in a car is like a reservoir, if it is not being charged as it is being used it will quickly drain. If a car battery goes flat a couple of times it becomes useless.

I reckon I will buy an addition battery specifically for this purpose

This will just give you a larger reservoir, which will only have the effect of buying you some time before they run flat. Your altinator in your Land Rover will then have twice the work to charge up 2 batteries if they run down.

if it's work around a house your doing would you not be better off with a fuel powered generator you can move around?

That is what I would think.

davelerave

small genny may be better option alright

Carlow52

Load way too big for a car battery: just look at the fuel u will be using keeping the LR (v6 probably) running versus the same fuel in a nice tidy QUIET honda geni

IMO no brainer

stylers

the current would be over 100 Amps while the load is running. while this might all be technically possible, car batteries are not designed for such large currents over a long period of time as it would be running, and it would definitely not be good for the alternator (even a big one) or fuel consumption (esp a land rover). the cabling and fusing arrangements would have to be done properly. I wouldn't trust any inverter of that size with heavy inductive loads like power tools, it would be just waiting to nuke itself.

just get a petrol genny (chinese cloned honda maybe ok if its only running occasionally, or if its gonna be left running, get a diesel one, but again beware of the chinese ones, which have a habit of falling to bits / self destructing :eek:

2011

it would definitely not be good for the alternator (even a big one)

It may well be OK if a larger alternator was fitted. I did a bit of searching on Google and found an alternator suitable for jeeps that can supply up to 160 amps. Check out this puppy:

http://www.premierpowerwelder.com/specs/PP160.html#saddlemount

fuel consumption (esp a land rover)

When parked up the Land Rover would essentially be a generator. I would guess that this vehicle runs on diesel, which is more efficient than petrol (you will often see large diesel generators, but never large petrol geneartors). Inverters are typically very efficient (in the region of 98% I am told). So overall perhaps this may in fact be quiet efficient.

What I am not sure about is:

1) Would you have to rev the nuts out of the engine to get enough power from your alternator? If this is the case it would not be good for your engine!

2) Is the current alternator large enough for a load this size?

I would suggest that the OP talks to Land Rover who will may refer him to a recommended auto electrician.

Below is an electric winch that is suitable for a Land Rover. It is rated at 2.1 hp, which is about 1570 watts. This would draw a larger current than the circular saw the OP intends to use.

http://www.superwinch.com/Danny_O_Day_Winch.html

MeatProduct

Thank you all for your comments, very much appreciated. I have not purchased any items just yet and I'm glad I have not after seeing all these comments.

I certainly don't want to spend more than I have to in order to get the job done so purchasing a new altenator is not on the cards.

I'll have a chat with an electrician about this, if it not feasible I'll go for the generator and sell it on once I am finished with it.

Thank you folks,

Nick

2011

if it not feasible I'll go for the generator and sell it on once I am finished with it.

From this statement I can see that all you are looking for is a short term solution. The answer is simple, rent a generator. For a 5kVA generator expect to pay about €10 to €15 per day. This will provide more than enough power for you.