Blue apple is 1200 CCA (cold cranking amps) or the amount of power it can produce for a very limited period of time (seconds)
What you want is a C20 or C10 RC (reserve charge) rating. Which on the blue apple is 60AH
What hissy was asking for is the total RC in AH (amp hours) that the person who quoted you $900 to have fitted. Im going to take a punt and guess it will be between 90 and 110Ah
$900 is a reasonable price but it can be done cheaper if you want to DIY
That said sometimes a fat tonne is easier to come by than the time to do these things yourself.
To DIY you will be looking at atleast 10 hours by the time you get under the car terminate power cables scratch your a$$ and stroke your chin secure and cable tie everything and get power finally into the trailer.
Thats before you start adding cig plugs etc. and securing all the cables and heat shrinking them etc.
So lets see the auto elecs bill would probably look like this
100Ah battery - $270
Battery isolator system - $120
Anderson Plugs x 2- $25
Cig or Hella plugs at $7ea - $28
12 meters of 8 B/S cable @ $7p/m - $84
5 hours labour @ $75 p/h - $375
Suddenly that $900 isnt looking so bad
Dont get me wrong im all for DIY - I've gone DIY myself. BUT I do have a fairly strong background in electronics and electricals - particularly automotive electricals (10 years of playing with high end car audio - 2 years of judging install and installers competence and DC electrical knowledge allong with Tafe certificates and mobile electronics and entertainment system industry recognition).
My advice is shop around make a decision as to what type of isolator you want.
Smart mechanical, dumb mechanical, or pure electronic.
Then start talking to auto elecs about EXACTLY what you want. Not meaning to sh!t can auto elecs but theres a lot of auto elecs out there who will just do what they think you need without actually asking you what you want and giving suggestions. (That said there are some flipping brilliant auto elecs out there!).
Make sure the Auto Elec uses 8 B/S minimum size cable (remember the lower the B&S number the thicker it is my prefferance is for 6ga or 6B/S cable). Make sure the auto elec is going to heat shrink the terminals at all connection ends (heat shrink is a tube that goes over the connection then you heat it up and it shrinks around it to make it insulated) including any connections to relays and circuit breakers and make sure he keeps a cover over the positive terminal of the battery.
As for 240V power - try to avoid it. As soon as you convert to 240V you loose efficiency.
For example a 100watt 240V globe powered off a 12-240 volt inverter requires rougly 16 amps.
a 100watt globe from 12V requires roughly 8.5 amps
This is because when you convert to 240V you get an efficiency of roughly 50-80% depending on the quality and type of inverter used (pure or modified sine wave)
most GPS, Laptops, cameras etc have a 12V charging option available even if yoiu have to buy them it will generally work out cheaper and more reliable than using a 12-240V inverter
Oh and I'd like to see the size of the drills and angle grinders they are using off a 600watt modified sine wave invertor - most electric tools like that use inexcess of 1200watts whilst running not to mention they are induction motors and require upto 3000watts on start up
A place I'd rather be...
Mitchel Road, Bomjinna. Central West Victoria (Jan '08)