LOST JEEPS :: View topic - Battery drain-current test

- read KEY-OFF current drain, reducing DVM AMP range as necessary to increase resolution
- current drain should be in milliamps for all modules, incl Remote Key Entry and alarm system

gmctd wrote:

- read KEY-OFF current drain, reducing DVM AMP range as necessary to increase resolution
- current drain should be in milliamps for all modules, incl Remote Key Entry and alarm system

Don't forget that it is not unusual for electronic modules to take some time to return to a standby state after being power cycled. Have you characterized this?

Don't want anyone to think that they have an unusual parasitic drain when they simply haven't waited long enough.

So far, I've not seen a 'clamp'-type meter that would read DC amps thru the clamp - they all say AC-DC amps, but reading thru, the spec states 400amp AC, sometimes true RMS - DC amp readings must be done with the probes by breaking the circuit, selecting one of the lower than max AC amp ranges

So, how does your owner's manual specify procedure for measuring DC current?

FYI, alternator output is not true DC - it is ~20khz PWM, which can be read with some AC clamp-on ammeters

Author:	gmctd [ Thu Jan 29, 2015 12:09 pm ]
Post subject:	Battery drain-current test - Ignition switch in OFF position
Battery drain-current test - Ignition switch in OFF position The ULTIMA RED-TOP battery was selected for the KJ CRD because the AGM construction could hold maximum charge for long periods of non-use, as resulted due to low sales rate as compared to the spark-infested V6 models, and for probability of week-end, month-end, or vacation-only RV usage - the RED-TOP reduced charging maintenance intervals vs standard lead-acid batteries, necessitated due to the increased starting current required by the 2.8L CRD engine Several control modules, incl ECM, TCM, BCM, FCM, ABM, are fused for direct-connect to battery, as is the alternator\regulator - these all draw very minimal current from the battery, usually in microamps, with all combined current drains normally in the low milliamp range If increased current drain is suspected as causing over-nite low battery voltage this test will reveal normal to excessive parasitic drain - Remove NEG battery cable - set DVM to CURRENT\AMPS, initially in 10amp range for manual DVM - AUTO-RANGING DVM will automatically select appropriate amp range - current flow is negative to positive thru the IGN circuit, so: - connect DVM RED\POS\+ lead to NEG batt cable - connect DVM BLACK\COMMON\- lead to NEG batt post - read KEY-OFF current drain, reducing DVM AMP range as necessary to increase resolution - total current drain from all modules should be in milliamps, incl Remote Key Entry and alarm system Added for clarity to determine pass\fail results: - decreasing drain to minimum static level would be normal - increasing drain to maximum level would be a fault - most DVM's have a sampling\refresh rate of ~300ms or so (inexpensive versions even greater), so any decreasing or increasing change in drain current may not be indicated or observable Coming soon to a forum near you: For your continued entertainment, actual open-hood in-situ parasitic drain tests, in series-insertion and clamp-on scenarios, replete with real-world measured values from microamps to milliamps, and all points in between Don't miss it - be there, or be square

Author:	dirtmover [ Thu Jan 29, 2015 12:57 pm ]
Post subject:	Re: Battery drain-current test - Ignition switch in OFF posi
gmctd wrote: - read KEY-OFF current drain, reducing DVM AMP range as necessary to increase resolution - current drain should be in milliamps for all modules, incl Remote Key Entry and alarm system Don't forget that it is not unusual for electronic modules to take some time to return to a standby state after being power cycled. Have you characterized this? Don't want anyone to think that they have an unusual parasitic drain when they simply haven't waited long enough.

Author:	gmctd [ Thu Jan 29, 2015 1:45 pm ]
Post subject:	Re: Battery drain-current test - Ignition switch in OFF posi
dirtmover wrote: gmctd wrote: - read KEY-OFF current drain, reducing DVM AMP range as necessary to increase resolution - current drain should be in milliamps for all modules, incl Remote Key Entry and alarm system Don't forget that it is not unusual for electronic modules to take some time to return to a standby state after being power cycled. Have you characterized this? Don't want anyone to think that they have an unusual parasitic drain when they simply haven't waited long enough. Good point, necessary to determine pass\fail results In that scenario you would be looking for a decreasing drain to minimum static level - increasing drain to maximum level would be a fault - most DVM's have a sampling\refresh rate of ~300ms or so (inexpensive versions even greater), so the delta A may not be indicated\observable

Author:	tjkj2002 [ Thu Jan 29, 2015 5:31 pm ]
Post subject:	Re: Battery drain-current test - Ignition switch in OFF posi
Just use a quality "amp clamp" and no need to disconnect anything,Sears has one that is decent price and fairly acurate.It can take up to 10mins for all the modules to go into "sleep" state on some vehicles so ignore any readings for at least 10mins.The "industry" norm is 50milliamps or less is normal. Oh and the Power Probes "The Hook" will measure amps also with no disconnect.

Author:	gmctd [ Thu Jan 29, 2015 9:26 pm ]
Post subject:	Re: Battery drain-current test - Ignition switch in OFF posi
So far, I've not seen a 'clamp'-type meter that would read DC amps thru the clamp - they all say AC-DC amps, but reading thru, the spec states 400amp AC, sometimes true RMS - DC amp readings must be done with the probes by breaking the circuit, selecting one of the lower than max AC amp ranges So, how does your owner's manual specify procedure for measuring DC current? FYI, alternator output is not true DC - it is ~20khz PWM, which can be read with some AC clamp-on ammeters

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Author:	tjkj2002 [ Thu Jan 29, 2015 10:30 pm ]
Post subject:	Re: Battery drain-current test - Ignition switch in OFF posi
gmctd wrote: So far, I've not seen a 'clamp'-type meter that would read DC amps thru the clamp - they all say AC-DC amps, but reading thru, the spec states 400amp AC, sometimes true RMS - DC amp readings must be done with the probes by breaking the circuit, selecting one of the lower than max AC amp ranges So, how does your owner's manual specify procedure for measuring DC current? FYI, alternator output is not true DC - it is ~20khz PWM, which can be read with some AC clamp-on ammeters I use amp clamps all the time and they read just fine.Using a automotive amp clamp is key,those electrician ones just don't work well for DC since they don't deal with DC.

Author:	gmctd [ Thu Jan 29, 2015 11:45 pm ]
Post subject:	Re: Battery drain-current test - Ignition switch in OFF posi
Ok, I see it now - stand-alone amp clamp with hall-effect sensor, internal battery-powered electronics for conversion, output to DVM or 'scope, AC amps = 1mv\a DC amps = 10mv\a Looking at switchable 60a\600a unit for parasitic drain, starting current, winch current, etc

Author:	thermorex [ Fri Jan 30, 2015 1:01 pm ]
Post subject:	Battery drain-current test - Ignition switch in OFF position
Mine is a Klein tools from Home Depot. It reads ac and dc. Just used it recently to measure weeks heater amp draw and few months ago to check the max amp draw when engine is running with all consumers on.

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