240v BX?

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joolie
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240v BX?

Post by joolie » Mon Jul 17, 2006 3:31 pm

What is the best way to connect a 12v/240v inverter to a BX?

I need to get mobile with a load of powertools, and I need a supply of up to 1000W.

There are ones which connect to the cig. lighter socket, or maybe another battery.

Is it possible/better to fit one off the alternator or battery?

Are there any complications running powertools from an inverter with the engine running.
'91 BX MkII 1769cc Turbo TZD Break

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IF it aInt BrOKe dON't trY 'n FIx iT.

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sleepy0905
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Post by sleepy0905 » Mon Jul 17, 2006 3:41 pm

speak to vanny he has one hooked up. :D
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M

Post by M » Mon Jul 17, 2006 3:43 pm

For that sort of power output you need to be conencting directly to the battery via some heavy duty leads using the correct type of invertor - remember that with most inductive loads there is an initial spike of upto 3 times the nominal consumption power and when you shut off there is often a back EMF surge too - make sure your invertor is designed to cope with this and has built in protection to stop the back EMF surge damaging the battery / charging circuit.

Also ensure the engine is running as with that sort of load you will be looking at a flat battery very soon.

It may even be worthwhile looking at rigging up an ancilliary battery system using a deep cycle (leisure) type battery as this will be able to cope with the loading for longer.

I use a 150W invertor in the car for a small telly now and again, I know Mr. B runs his fridge off one when out and about camping.
I also use a 300W one (powered off 2 x 75AH deep cycle batteries in parallel coupled to a 20W solar pane charger) to power a 100w water pump for the central heating - the reason its that big is to cope with the inductive load - it runs quite happily on this despite the output being a modified sine wave, but then its not a big load.

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Post by jeremy » Mon Jul 17, 2006 4:07 pm

Problems are that with a huge inverter you'll either run the battery flat or set fire to the car or both.

750 watt (which would run some power tools one at a time will draw 62.5 amps - and my angle grinder is rated at 800 watts and my router at 1100 watts and my circular saw at 1200 - which means that the saw will draw 100 amps.

These sorts of currents need seriously heavy wiring - thicker than anything on the car apart from the starter cable. Such cable is expensive and of course will need special plugs and sockets, which are even more expensive.

The normal diesel Citroen BX battery is rated at 55 amp hour - which in theory means that it will provide a current of 55 amps for one hour then be flat. in theory it will also provide 1 amp for 55 hours and in fact these things are usually measured over a period of time (20 hours I think)

The largest standard alternator fitted to BX is that fitted to the TD and 16 valve which has a nominal capacity of about 50 amps. Those with air conditioning have a larger one of about 75 amps. I know from experience that the larger ZX one cannot be fitted straight on to a TD BX and considerable modification will be needed.

I think most inverters over 200 watts are provided with dog clips for heavy use. the maximum that can be drawn from a cigarette llighter socket is around 10 amps and I wouldn't draw this much for too long as there is a risk of overheating some of the rather slender wiring.

The next problem is that even diesel BX are not designed to cool with the car stationary and the engine under load. The system will use the draught from forward motion as part of the cooling - and over 20 MPH this draft will be greater than and draught created by the fans. You would also have to provide some form of throttle to keep the engine running at charging speed - say 3000 alternator RPM - (engine speed will vary between petrol and diesel.)

As 1.5 KVA generators with Honda petrol engines are available for about £330 including VAT I'd go for one of them.

M

Post by M » Mon Jul 17, 2006 4:15 pm

jeremy wrote:As 1.5 KVA generators with Honda petrol engines are available for about £330 including VAT I'd go for one of them.
I was just thining something similar myself - Makro (UK) have some rated at about 1.5KVA for £180 +VAT, and they have a really sh***y one rated at 750W (no good in this case I know) for £40 +VAT. My dad has one, its a 2 stroke, noisy as f*** and oils up spark plugs like you would not believe.
Its used to provide power for lighting in an emergency so its not a big problem.

EDIT: Just re read my original post and neglected to mention the Central Heating pump / ignitor power is just an emergency thing on the off chance we lose the mains supply - we at least still have heat & hot water and a means to cook. Its not the sole power for the boiler.... Though i am toying with the idea or trying to make a wind turbine from a car alternator to power some outdoor lighting. [/Whaaaaaaaaaaay OT modeImage ]

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Post by joolie » Mon Jul 17, 2006 5:54 pm

yep ,getting a gen sounds like a good idea.

it'd be a diesel one though ,theres a lots of RME (biodiesel) up here, and its 70p a litre, rapeseed oil is even cheaper, anyone ever ran a diesel generator on veg oil?

a preheater would be a good place to start I guess, and I have a spare one from the BX.

If I were to also connect to the battery (and mines a 90A monster) or charge up a leisure type, whats the max W I could use?

can an alternator charge x2 batteries in transit??
'91 BX MkII 1769cc Turbo TZD Break

running on RME/SVO

IF it aInt BrOKe dON't trY 'n FIx iT.

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Post by Vanny » Mon Jul 17, 2006 5:59 pm

to run 1000w under normal running conditions you are going to need a bloody big and very reliable power source. In order to save from killing an inverter you need it to have at least 10% more capacity then what your actually using, so in this case you would want to be looking at a 1.1kw, in reality your porbably going to need more in the range of a 1.5kw inverter which fortunately are easy to come by!

As mentioned your switch on current will be much higher, as a rule of thumb if it spins faster it will have a higher switch on current. As previously mentioned you will find that switch on voltage is twice to three times the normal running power, all inverters can provide double there normal running capacity on switch on for a few seconds! It is possible to calculate the switch on power of most power tools, however they will never normally be more than three times the normal running power!

Regardless, your battery and alternator setup wont cope, the turbo diesels have the biggest alternator at 80amp and as Jeremy has calculated it wont last very long. You'll need a deep cycle leisure battery and a switch over relay, you run the tolls from the leisure battery and the switch relay will charge it from the alternator as and when the normal battery is full, again nothing too complicated!

Now something that hasn't already been mentioned, there are two types of inverter! as you want 240v AC you need the current to be alternating, most inverters use a ramp generator to simulate this changing current, great for most applications, not so good for anything with moving parts or brushes, thats pretty much every power tool going then! In order to stop premature failure of the tools and the brushes you'll likely need a 'real sine invertor' for which you can expect to pay around £500 for a 1.5kw invertor.

Thats an aweful lot of money! And then a huge amount of messing around to get it all wired in and working safely, and its already been pointed out that for that sort of money you can buy a pretty nice stand alone generator!

I do have a number of invertors in the car (110v and 240v) and these primarily recharge battery powered devices such as the laptop, shaver, cordless drill, torches etc and i have also run a complete computer suite from it (base unit, monitor, printer etc) and never once had any problems, but i have never (as yet) run any rotating powertools from it as there likely to do significant damage in the long term!

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Post by jeremy » Mon Jul 17, 2006 8:50 pm

Charging additional batterys is possible and in reality is simply connecting them to the alternator BUT:

If you connect 2 batteries in parallel - ie positive to positive - to give more capacity at the same voltage - the stronger (higher voltage) will discharge through the weaker! Not desireable - and could even set fire to things!

If you simply connect your second batttery in parallel for charging then you have the problem that it will join in the starting and probably destroy its wiring.

All this can be prevented by relays to connect the additional battery when a higher voltage is available for charging - or even a simple blocking diode to make sure the current goes the right way.

Diesel generators seem rare, large and very expensive. I'd have thought a lightweight petrol was the way to go - and it won't use much fuel as its not very powerful.

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Post by joolie » Tue Jul 18, 2006 1:39 pm

what about building one?

http://hackaday.com/entry/1234000490059897/


My brother bought a 2nd hand diesel gen/arc welder on ebay for £300
it must be 1.5kw or more?!
'91 BX MkII 1769cc Turbo TZD Break

running on RME/SVO

IF it aInt BrOKe dON't trY 'n FIx iT.

M

Post by M » Tue Jul 18, 2006 2:04 pm

joolie wrote:what about building one?
The only diesel stand alone genny's I have seen have either been modified perkins diesel engines that pump out a low power to charge batteries( does anyone know where you can buy Submarine batteries as every bloody hose in the wilderness seems to use these to store their power??) that are then used via an invertor or huge great big chuff off things to power a building (like the one we hired for the clinic last Christmas & New Year that filled the whole garage).

As Jeremy has pointed out - cooling becomes an issue when under load, as indeed it does with a petrol engine - I suppose its possible to build one, but at what price in comparason to say buying an off the shelf petrol genny?

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Big lengths of starter cable can be had cheaply from your local scrap yard - just look for a mini and whip the +ve battery lead off it - 10 foot of first rate heavy duty cable for pence.

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Post by Stewart (oily!) » Tue Jul 18, 2006 5:03 pm

I have experience of managing large 12v volt battries and never having enough power, invertors are power hungry, you need a small petrol generator or a diesel one you can tow behind the car :) try a search for Kipor generators on ebay, they seem to be very neat things
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