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Not much left over once everything is on all at once
P38A Furry stuff...
- Thread starter Jon Dor
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Datatek
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Battery doesn't need much if it is almost fully charged and the charging voltage is correct.
Jon Dor
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The secondhand one I got for my 4.6 Thor is 150amps, as per the original Keith .If the alternator is rated at 100 or 150 amps, you need a hell of a load to pull the voltage down
brianp38dse
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As you have a v8 the regulator Datatek posted is not the one that is for the dozzel
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I have an 100A alternator feeding a Type 19 (100AH 820CCA) battery on my Defender 300tdi.
Apart from aditional lights I also have a winch, ticking over the voltage is 14.2 on the loom and slightly higher when motoring, I don't have a lot of electrics (its a Defender)
Starts perfectly (even after not runing for a week or so) and only operate the winch (loaded) with the engine running.
Starting takes around 65A (i believe) inc the heater plugs which does drop the voltage to just below 12 . If I went out now it would be around 12.6V.
Get one of these .... https://www.ebay.co.uk/itm/353335598430?hash=item5244715d5e:g:YB4AAOSwcCdgFSkX&var=622536198961
Apart from aditional lights I also have a winch, ticking over the voltage is 14.2 on the loom and slightly higher when motoring, I don't have a lot of electrics (its a Defender)
Starts perfectly (even after not runing for a week or so) and only operate the winch (loaded) with the engine running.
Starting takes around 65A (i believe) inc the heater plugs which does drop the voltage to just below 12 . If I went out now it would be around 12.6V.
Get one of these .... https://www.ebay.co.uk/itm/353335598430?hash=item5244715d5e:g:YB4AAOSwcCdgFSkX&var=622536198961
Jon Dor
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Cheers, Mik! Great minds think alike...I just installed a dash-mounted, similar, LED digital voltage meter...I just need to make the electrical connections, but I ran out of oooomph. Battery on overnight charge until around 10:00hrs.
I was always told that was not advisable test on Modern cars. If the alternator is at all iffy in can do alsorts of damage to sensitive electrical components.
You get good enough readings across the battery terminals.
J
Jon Dor
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Keep it simple...like me!
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Agree, the battery acts as a giant stabiliser to deal with any peaks or troughs from the alternator
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I think you are right if the regulator is not regulating the voltage then without the capacitance of the battery the voltage will rise across the loom, however 'and' as long as the regulator is restricting the voltage to below 15V then there really shouldn't be any issues. Revving the engine will increase the voltage as its proportional but around tickover up to 1200rpm i wouldn't think it would be over 20V (i am not an auto sparks, perhaps one could chip in ?).
The alternator is producing an AC voltage too which needs to be rectified and then regulated.
I also think that if the regulator (a discrete device) does 'die' the voltage drops to zero. The diode simply won't pass a voltage.
I'd guess the easy way to determine this would be to measure the voltage across the battery fist, before disconnecting the + terminal.
Agree with most of that.
Can regs not fail and overcharge
But if a diode fails you can pass AC volts too
Just an opinion that that test could potentially damage stuff so wouldn’t recommend it. Is it worth the risk of frying an ecu?
when other options, with good results are available
J
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Agree with most of that.
Can regs not fail and overcharge
But if a diode fails you can pass AC volts too
I think that is extremely rare ... you'd need to have several diodes fail to short, which isn't 'normal' and the regulator and some of the other devices too.
An engine could fall from a passing Jumbo and flatten our cat, perhaps narrowly missing the polytunnel and breaking the cold frames ..... perhaps I should keep the cat in ?
The ECU runs directly off the alternator feed ?? surely that has a 7805 (/eqv) on the input and has primary 5V power rail ?
If you battery goes flat (or drops below 12V on starting etc) then the engine management system would collapse and the car would never start if it needed 12V
I wired up a temperature relay the other day that deploys a BUCK on the power rail that gives out a regulated 1.2 Amps @ +5V from +28V down to +6V, it's amazing what you can get these days.
Its based on the MPM3610 IC and cost less than £6 ... anyway, back on topic
when other options, with good results are available
J
Oooh ... do tell ?
Had a Nissan pick-up was delivering hire bikes in Vilamoura Marina got out and thought a bit whiffy here in the Marina today...next drop off a villa in the hills smell was there as well...flipped bonnet and the battery looked like a rugby ball luck was in as it was a desiel so engine running battery disconected got to garage...
Are you a vet?
Are you a auto electrician?
Put your probes on the battery engine running
Take the main leads off the alternator and check diodes for 1 way travel of squilles with the engine off
.I am not gonna get into it again with you. All I said was. I wouldn’t recommend that as a test on a car with alsorts of electrickery when there are other options.
If you want to take that risk fine
J
Got a bollicking from Fred at the garage...don't ever run an engine with the battery disconected the alternator needs to be relieved of its output I think he said but it was 20yrs ago though...
Datatek
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Disconnecting the battery while the engine is running is a good way of destroying the diode pack. On sailing boats there is an isolator switch for the batteries, I have replaced several alternators for people who cut the batteries with the engine running. These days the diodes are a bit more durable but the risk of damage is still there.
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No, but my mate is, he's Supervet Ian Barclay.,Vet of the year in 1996, he's retired now but I think he'd be good at restoring flat cats.
Mind you RB211 engines are a tad more robust than Chester and heavier, I fear he may not survive.
He was a dab hand helping me put my Defenders engine together and is doing a great job in restoring an Austin Healey 3000 Mk1, so there's hope (always look on the bright side).
No i'm not an Auto Sparks.. Didn't I say that already in this thread ? (eg post #50)
Put your probes on the battery engine running
Take the main leads off the alternator and check diodes for 1 way travel of squilles with the engine off
I am not gonna get into it again with you. All I said was. I wouldn’t recommend that as a test on a car with alsorts of electrickery when there are other options.
If you want to take that risk fine
J
It's not me, it's everyone that reading this thread.
I gave (what I thought) was a simple set of actions to test if the battery was dragging down the alternators output or if there was an earth fault. (post #27)
All you have done is tell (us) that it's not the way to do it as it will cause untold damage to the cars electrics - no explanation, just scaremongering that it will blow up the ECU (post #51).
Then you say there are alternate, safer, methods ....
Here is that method .... "Take the main leads off the alternator and check diodes for 1 way travel of squilles with the engine off
" Obviously i'm a bit stupid, cos I didn't understand that at all ....
What leads ?
Test diodes how ?
Whats 'squilles' (or is that a typo).
What sort of 'meter' ?
Can you expain or are you just disagreeing with me, because that's your modus ?
Datatek
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There are 2 failure modes for the regulator, open circuit or short circuit. Luckily the former is more common as in short circuit mode the alternator can produce high voltages before it burns. Open circuit means little or no output, there may be some output due to residual magnetism in the armature.
Open circuit means little or no output, there may be some output due to residual magnetism in the armature.
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