more powerful alternator

[hotrodder13]

i have been told by several people that with the power my speakers and everything else are taking my alternator will burn out a lot quicker, ive bin told i need a 75 amp one

what can i get one off
thanks tom

[bmcecosse]

Madness..... where do you find these 'people' that tell you these tales.....?

[IslipMinor]

Complete! What size alternator, and what capacity battery do you have now?

[hotrodder13]

Madness..... where do you find these 'people' that tell you these tales.....?

One of these people have the 7th loudest system in the uk so I think he knows what he's on about, and one of them use to come on these forums

and at the minute its a caravan battery and not sure about he size of the alternator, it's the one that comes with the conversion kit 45 amp I think

Cheers Tom

[bmcecosse]

You'll go deaf........

[hotrodder13]

already gone deaf becuase of the exhaust haha, my exhaust was db tested last weekend and came out at 126.6 db his system is 157.6 db inside the car

[MikeHA4]

Hello Hotrodder, have you first worked out the electrical consumption the equipment requires? That would be a good starting point.

[IslipMinor]

The alternator will not 'burn out' quickly just because it has some work to do. The size you need should be matched to the load being used. A 45A one will satisfy most requirements, unless you have very uprated headlamp bulbs, electric front and rear screens etc. Even then 55A, which is commonly available, will normally be big enough.

What is the actual maximum total current draw whilst driving?

[hotrodder13]

how would i work out how much is being used ?

ive got radio, 4 5" speakers 1200W amp and 1200w sub, xeaon bulbs and everything else standard

cheers

[IslipMinor]

With everything, apart from the amps, calculating the current draw is easy - current (A) = power (W) / volts (V), so for typical 55w halogen headlight bulb it is 55/12 = 4.5A (approx). Your xenon ones are probably a similar wattage, unless you have something special?

For an amp the relationship between the quoted output and the current draw is not exact, it depends on whether the 1200w quoted outputs are peak power or RMS and also on the volume setting. Otherwise 2 x 1200w = 2400w = 200A!! About the same as the starter motor!! If you take the RMS output, add about 25% and divide by 12, that will give you an approximate current draw at maximum output. What you really need to know is what the draw is at more typical volume settings, and how long you use it for?

The only way I know would be if you had an ammeter connected and turn everything on, without the engine running, to see what current is being drawn (you would need either a 50-0-50 or 60-0-60 ammeter). If, with the amps at normal to high volume, the draw is greater than the maximum ammeter scale, turn everything else off and measure just the amps on their own. Then add the separate readings together.

[hotrodder13]

think il buy a ammeter to try it cause i use it all the time but sometimes its on quite but at night its on loud and as for headlights im buyin a hid kit with 8000k bulbs which are very bright

thanks tom

[PAULJ]

If you put a volt meter on your battery check your battery voltage. Then start your car, put everything on lights heater wipers etc and check the voltage. If its below your original volt reading you are discharging and not charging. all that is going to happen is your battery will go flat. Ive never understood people who need a sound system that makes your ears bleed but I dont get steem traines and morris dancers. FILL YOUR BOOTS

[bmcecosse]

You must have self levelling headlamps if you fit an HID kit...... I'll be interested to know how you are doing that!

[hotrodder13]

You must have self levelling headlamps if you fit an HID kit...... I'll be interested to know how you are doing that!

plenty of car goes round without them being self leveling and thanks for the tip on how to check, il have a go when i get sum time off over crimbo

[ian.mcdougall]

If its only hid on dip I think thats ok but hid on mains should have self leveling or should not pass mot just because they are sold and people fit them does not mean they are ok and most modern lamps have separate dip and main bulbs so dip is hid and main is plain bulb

[bmcecosse]

Where do I get these 'modern lamps' with separate bulbs - to suit a Minor ?? Cibie used to make the excellent Bi-ode, but sadly not for many years now!

[Alec]

Hello BMCE,

I find standard quartz halogens lamps more than adequate, fed with decent sized cable through a relay. So many lighting problems are due to old and poor connections so insufficient voltage to meke the most of the lamp.
Too many of these fancy lamps are just plain dazzling.

Alec

[RobThomas]

130watt offroad h4 halogens are perfectly good enough, if slightly illegal. Not as bright as the HID bulbs in my Merc but better than the Mondeo system. Big watts equals big loom, so, a complete rewire is going to be on the cards?

I had to run most stuff through relays and large Maxi-fuses since the wiring loom on the MGC was hardly up to the job, being rather ancient and 'done down to a price', so I mounted relays for the dim-dip and flash near the oil filter. The relays are sat on a Metro fusebox which was a handy size and the wires, as you can see, are large in cross section to reduce voltage drop. If I had to do it again I would not use any bullet connectors at all since they always seem to be the cause of problems.

[bmcecosse]

Anything over 55 watt is completely illegal for highway use - and dare I say, very irresponsible and inconsiderate to other road users ?
The 55 watt limit is there for a very good reason. And yes Alec - halogens are fine, no need for anything else for sane road driving. Different story for Rally Stages etc - but then the extra lights/high watt filaments are allowed.

[RobThomas]

Anything over 55 watt is completely illegal for highway use

http://www.legislation.gov.uk/uksi/1989 ... ule/5/made
Often quoted, but not entirely correct. Pre Oct 77 cars may use lamp lenses and bodies without E-marks if BStandard marked and there is currently no stated maximum wattage, only a limit on Lux and Lumen for new manufacture. If it causes dazzle (prove it?) then may be pulled by the rozzers under section 27 of the above.

All this according to the local traffic police dept.


Also, H4s are 60watts main beam as standard, 55 dipped. HID are rated at 30 amps for about 50% more Lumen than halogens. My Merc HIDs make 'instant daylight' and cause me to get 'flashed' but they are completely correct in the eyes of the law. The Lenham Midget has legal lighting (as inspected by the traffic plod) and only the lens cowlings cause problems since they scatter the light a bit but have done so since about 1967.