Electrical power draw

[ballbag]

One for sierraferry perhaps......

Anyone know what the base load on the D2 elec system might be? Say vehicle running, no lights or accessories on?

Think alternator is rated at 120 amps and am trying to determine how much other crap I can run off it.

Cheers.

[sierrafery]

I feel honoured by your confidence in me but i must admit i didnt think about that untill now, i only know the average current draw with ignition off[smilebigeye] ... though i'm sure there are differencies from one vehicle to another based on various factors so for you to be 100% on the safe side better measure it cos that's certain... the easyest way would be if you can borrow a clamp meter if you dont have one and put it around the positive lead with engine running, or "invest" in one of these VC3266L+ Mini Digital Multimeter Voltmeter Ammeter OHM Diode Voltage Tester 200A Auto Range AC/DC Test Clamp Meter Tester-in Multimeters from Home Improvement on Aliexpress.com | Alibaba Group (https://www.aliexpress.com/item/VC3266L-Mini-Digital-Multimeter-Voltmeter-Ammeter-OHM-Diode-Voltage-Tester-200A-Auto-Range-AC-DC-Test/32749769436.html'spm=2114.40010308.4.14.Iw1agv) cos it's handy to have it within reach

[Vern]

That multimeter linked to the post doesn't clamp dc current, only ac, so its of no use. You need a dc clamp meter.

[Homestar]

My guess would be a couple of amps for the engine, cerainly negligible in the scheme of a 120 amp alternator. Other ancillaries certainly draw heaps more. Lights, wipers, heater fan, rear demister, indicators and brake lights all draw far more and would add up to 30 or 40 if everything was on at once - plenty left for additional lighting, etc. [smilebigeye]

What were you planning on running?

[sierrafery]

That multimeter linked to the post doesn't clamp dc current, only ac, so its of no use. You need a dc clamp meter.
[bawl] ... you are right, sorry, i just linked the first clamp meter i found without reading well the description... i should have thought that a Hall DC clamp meter can't be so cheap but being chinese i presumed that everything is possible.[bigsmile1]

[bee utey]

It's no good putting a clamp meter anywhere near the battery as you would only be measuring the balance of charge current. Not quite sure how a D2 fuse box works but you would have to isolate the input from both the battery and alternator, then measure the load. I'd be looking at fitting a 100A current shunt in the fuse box feed and measuring the current through that. I wouldn't be surprised to see 15-20 amps load including the varying duty cycle of the injectors, the fuel pump, various control valves etc.

DC 6.5-100V 100A/20A Digital Power Meter Monitor Power Voltmeter Ammeter Shunt | eBay (http://www.ebay.com.au/itm/DC-6-5-100V-100A-20A-Digital-Power-Meter-Monitor-Power-Voltmeter-Ammeter-Shunt-/201771211821?var=&hash=item2efa805c2d:m:my-x74vUfEvaiW2MLO9FYRw)

[sierrafery]

The OP wants to know the draw with engine running to not exceed the alternator's output with some add-ons so IMO a clamp around the battery lead (leaving the wire from alternator to battery out) is OK

[ballbag]

Thanks chaps.

Thermo fans, cabin fan, head and tail lights, fuel pump in the order of 15 amps each I would think. Wipers, indicators, brake lights, rear demister I'd guess 5 each. Stereo about 10. So my guess is a total up around 90 amps.

In addition I am already running spotties/flood lights (15 amps), a second battery (? amps) with fridge (5 amps) and various low current outputs.

Am building a drying box for snow gear which will pull up to 25 amps off the second battery.

So my estimation is that the drying box will draw down the second battery at about 10 amps.

Am I close?

[Homestar]

Thanks chaps.

Thermo fans, cabin fan - 5 amps, head and tail lights, fuel pump - 5 amps in the order of 15 amps each I would think. Wipers, indicators, brake lights, rear demister I'd guess 5 each. Stereo about 10 - 2 to 3. So my guess is a total up around 90 amps.

In addition I am already running spotties/flood lights (15 amps), a second battery (? amps) with fridge (5 amps) and various low current outputs.

Am building a drying box for snow gear which will pull up to 25 amps off the second battery.

So my estimation is that the drying box will draw down the second battery at about 10 amps.

Am I close?

Remember that you would rarely - if ever, use all of that at once. The maximum demand of the vehicle would be around 50 amps leaving plenty up your sleeve. Even if you occasionally run over 120 amps for a short time (which I would doubt) it isn't going to hurt anything (as long as all your wiring is in good condition) but just draw down your battery a few amps - and that's a big if IMO - I used to max out my old 35amp alternator on my Subaru occasionally on a cold wet night with my upgraded headlights and spotties on - the charge light would glow but I could still drive it the 45 minutes home from work after afternoon shift and start it again fine the next day. :)

I wouldn't worry about the alternator size at all - just make sure the wiring to the high load devices you are adding is up to scratch. :)

[PhilipA]

I have to say that I am constantly surprised by the voltage drop of the starting battery when the ignition is turned on , usually from 12.7 down to 12 or even 11.9V.
My battery is an Optima Blue top with 760 CCA .

I believe there are big capacitors and also the glow plugs are programmed to go on even if the light is not on.

I have connected a 20AMP power supply to the battery when I am reprogramming the ECU and even then the voltage will drop initially until it rises back up to 13.8Volts with everything else turned off and ignition on but engine off..

So my conclusion is that the ECU and other processors draw over 20 amps initially until the capacitors are charged up, so unwise to link anything else until everything has settled.
Regards Philip A

[Tins]

Remember that you would rarely - if ever, use all of that at once. The maximum demand of the vehicle would be around 50 amps leaving plenty up your sleeve. Even if you occasionally run over 120 amps for a short time (which I would doubt) it isn't going to hurt anything (as long as all your wiring is in good condition) but just draw down your battery a few amps - and that's a big if IMO - I used to max out my old 35amp alternator on my Subaru occasionally on a cold wet night with my upgraded headlights and spotties on - the charge light would but I could still drive it the 45 minutes home from work after afternoon shift and start it again fine the next day. :)

I wouldn't worry about the alternator size at all - just make sure the wiring to the high load devices you are adding is up to scratch. :)

Have to agree. Also, what stereo are you running if you expect a 10a draw from it?

Gav's Scooby had a 35a altar ator. When was the last time a LR had something below 80a? As Gav also says, that's what the charge light is for. Sure, most times you see it it's telling you your alternator needs help. That's because, most of the time, it doesn't.

[ballbag]

Yeah, wiring will be sufficient.

All estimates I made above are what I'd expect worse case, I know actual use will usually be lower.

I do run all of those concurrently through winter which is why I need to ensure the extra 25 amp load won't be too much.

Point of interest - high beams + 3 x 70w spotties knocks 0.5V off the charging circuit.

Thanks all for the input.

[sierrafery]

It's not about capacitors, when the alternator's own regulation is sensing the higher draw it increases the ouput and vice-versa:

.....
When the battery is at a low state of charge or the current draw from the electrical functionsof the vehicle causes a voltage drop, the alternator/ generator automatically charges at its maximum rate (dependant on rotor speed) until 14+ Volts is reached. When demand on the alternator/generator falls, the current output is reduced.

[ballbag]

Test 1:

Vehicle off, ran Chinese spec 300W snow-gear drying box (to be sexed up with marine carpet if trials prove successful) off second battery. 16 amp battery charger connected to starting battery.

Result 1:

Flattened starting battery in about 90 mins. Switch on unit crapped out so deleted it. Retired to deck with beer while charger does its work.

https://www.aulro.com/afvb/images/imported/2017/05/58.jpg

https://www.aulro.com/afvb/images/imported/2017/05/59.jpg

[trout1105]

Have you tried the dryer with the truck running?
A 16A charger has No hope of running something that draws 100A-300A.
From what I have been told the disco alternators put out 130A, So if your dryer is constantly pulling more than 130A it will eventually drain the batteries I would think.

[Homestar]

Have you tried the dryer with the truck running?
A 16A charger has No hope of running something that draws 100A-300A.
From what I have been told the disco alternators put out 130A, So if your dryer is constantly pulling more than 130A it will eventually drain the batteries I would think.

300 watts, not 300 amps. World out around 25 amps. :)

Alternator will have no dramas with if while the engine is running.

[ballbag]

Yeah nah, have not run the dryer with engine yet but did dry a damp T shirt without incident, so results as expected thus far. Will report back with further results.

[ballbag]

Drying box working pretty well and alternator able to maintain starting battery charge with cabin heater, high-beams and spot lights running. Have run for up to 2 hours.

Isolator for second battery opens and shuts continually if/when drying box and fridge pulls combined voltage below cut-out point, but thus far have not drained either battery below 12.8V standing.