How to carry out parasitic drain check with twin batteries ? (4 Viewers)
- Thread starter Paulpen
- Start date
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uHu
Bridgeburner
5 hrs starting at 12 v resting voltage means you would have to crank in 25 Amps continuously. If you didn't do over 20 amps x 5 hrs, and after 5 hrs had less than 1 amp at 14,4 volts, your battery is severely reduced. Assuming 90-100 Ah battery.
With the voltages you quote above, I would suspect one blown diode in the alternator, although it's hard to say as the amps are few at idle. The diode bridge is easy to change, and you can open up the alt. and check each individually.
With the voltages you quote above, I would suspect one blown diode in the alternator, although it's hard to say as the amps are few at idle. The diode bridge is easy to change, and you can open up the alt. and check each individually.
- Thread starter
- #24
They are 90Ah batteries going by the stickers on them.
Charger was down to 3A when I turned it off though.
Are there any other checks I should do before removing the alternator ?
Also is there a guide for removing it and testing the diode bridge ?
Thanks for all the help by the way guys
Charger was down to 3A when I turned it off though.
Are there any other checks I should do before removing the alternator ?
Also is there a guide for removing it and testing the diode bridge ?
Thanks for all the help by the way guys
before you start opening everything up, have you considered using/getting/borrowing a DC clamp ammeter? Those are very useful to tinker with vehicle systems. You can get a decent one for $50 or so for up to 100A or so, from memory. Make sure the range is appropriate for your system though. You could then measure the charging current from alternator to battery without disconnecting anything, just by clamping around the cable. Amazing stuff. And then easily tell if your alternator is producing juice or not.
To test a battery for soundness, you can use a battery tester. Those are kind of pricey for just an occasional use, though. In the US at least, car parts store sometimes have one to loan or they will test your battery for free (but are of course more likely to bias the findings towards the need to purchase of a new one...) Or you could rig something up with a load (light bulbs, inverter, etc) and figure it out yourself. Fun times!
To test a battery for soundness, you can use a battery tester. Those are kind of pricey for just an occasional use, though. In the US at least, car parts store sometimes have one to loan or they will test your battery for free (but are of course more likely to bias the findings towards the need to purchase of a new one...) Or you could rig something up with a load (light bulbs, inverter, etc) and figure it out yourself. Fun times!
- Thread starter
- #26
Tooling is a bit of an issue over here in the UK at the moment with the full country on lockdown and fines for being out with no good reason.
I'll have to see what I can get hold of and make a call from there I suppose.
What range of amps do I need to measure to test the battery's and alternator ?
I'll have to see what I can get hold of and make a call from there I suppose.
What range of amps do I need to measure to test the battery's and alternator ?
Check your specific alternator rating and plan for that max amperage if you want to be sure not to exceed the capabilities of a DC clamp meter. The typical alternators for this class of trucks are usually around 100-150A I think, but no idea about yours. Of course, it may not run full blast if the batteries are not badly discharged, but I guess you'd want to know if your alternator is fully functional and then you might not want to take a chance.
Anyway, given the times we are in, you could try to get a feel for the state of your batteries with a simple improvised discharge test. Won't tell you about cranking capacity but will give you a feel for storage capacity. Figure out what max amperage you can read with your current multimeter. Find a 12V light bulb of appropriate (not exceeding your max but smaller current is better) size (borrow one from a truck light?) and discharge the fully-charged battery through the bulb while measuring current during the test and find out an estimate of Ah capacity that way (average current x discharge time). That may already tell you a bunch about the state of your battery. If it fails miserably, well there you go. (Note that this is not so good for the health of a starting battery in theory, but I've done it with no apparent ill effects, and a man's gotta do what he's gotta to do... YMMV, though.)
Anyway, given the times we are in, you could try to get a feel for the state of your batteries with a simple improvised discharge test. Won't tell you about cranking capacity but will give you a feel for storage capacity. Figure out what max amperage you can read with your current multimeter. Find a 12V light bulb of appropriate (not exceeding your max but smaller current is better) size (borrow one from a truck light?) and discharge the fully-charged battery through the bulb while measuring current during the test and find out an estimate of Ah capacity that way (average current x discharge time). That may already tell you a bunch about the state of your battery. If it fails miserably, well there you go. (Note that this is not so good for the health of a starting battery in theory, but I've done it with no apparent ill effects, and a man's gotta do what he's gotta to do... YMMV, though.)
- Thread starter
- #28
Righty then - alternator is off so thought id do some testing to it as its now the weekend as everywhere is shut.
Stripped it down and seems like the rectifier has a shorted diode on the negative side and a bearing is going which has caused one of the brushes to wear the rotor.
It seems to be a Lucas alternator with no Toyota marking so possibly not the original one - looking like the source of the problem though !
Stripped it down and seems like the rectifier has a shorted diode on the negative side and a bearing is going which has caused one of the brushes to wear the rotor.
It seems to be a Lucas alternator with no Toyota marking so possibly not the original one - looking like the source of the problem though !
