EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: phawrel on February 10, 2019, 05:25:10 pm
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A diesel car has usually a high startup current drawn from battery. A clampmeter is the rational solution to use when I want to see the variation of the DC amperage drawn from the battery during those 0.5 seconds (up to 1 second) needed for engine startup.
I know that Fluke has a clampmeter that does exactly that (e.g., clampmeter able to measure DC amperage with the clamp -- duh ! -- every 20 milliseconds or faster).
But I surely don't have the cash for a Fluke. Can anybody please recommend a more affordable solution ?
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Take a look at the Uni-T UT210E. It measures AC/DC amperage and costs around $40-50. I used it to find parasitic draw on a Honda.
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Check if the hantek cc-65 (max 65A) or cc-650 (650A) current probes http://www.hantek.com/en/ProductDetail_15_77.html (http://www.hantek.com/en/ProductDetail_15_77.html) you can find then on aliexpress for about US$45. If you look in the forum there are a review of the cc-65, it looks very decent for the price.
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Forget the UT210E, 100 A is not enough.
The Hantek CC-650 could be an option.
You're looking at 500 A cranking current minimum,but it could go far higher depending on engine size.
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I've got a Brymen BM089 for that purpose. It's at 130€ - https://www.tme.eu/en/details/bm089/meters-and-acdc-clamp-probes/brymen/ (https://www.tme.eu/en/details/bm089/meters-and-acdc-clamp-probes/brymen/)
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Maybe a used Fluke i1010?
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Forget the UT210E, 100 A is not enough.
The Hantek CC-650 could be an option.
You're looking at 500 A cranking current minimum,but it could go far higher depending on engine size.
This. The peak current is surprisingly high when cranking, hence the fat wires...
For comparison, my Fluke reported that my old 1.6 liter 4-cyl Corolla imports would draw around 250A on crank.
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Your car's battery should be marked with a CCA (cold cranking amps) rating. If its the correct battery for your car model, that will give you some idea of the max current you are likely to see.
Provided the vehicle has rubber tires (i.e. not a boat or tracked vehicle) yoou could insert a suitable current shunt (probably 500A or 1000A) in series with the battery negative lead, and scope the voltage across it with a DSO, one-shot triggering on the switched supply voltage to the starter solonoid. The *ONLY* ground to the vehicle chassis should be via the scope ground clip, which is why it must be on rubber tires. If its not on rubber tyres, you'd need to use a handheld scope or one with isolated inputs. The current shunt will typically have 50mV, 75mV or 100mV across it at its max rated current - see its specifications for details.