Car startup current measurement with clampmeter - Page 1
Forum section: electronics / beginners

author: phawrel
author_rank: Newbie
timestamp: February 10, 2019, 05:25:10 pm
content: 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 ?

author: mr.fabe
author_rank: Regular Contributor
timestamp: February 10, 2019, 06:33:23 pm
content: 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.

author: Microcheap
author_rank: Frequent Contributor
timestamp: February 10, 2019, 09:18:01 pm
content: Check if the hantek cc-65 (max 65A) or cc-650 (650A) current probeshttp://www.hantek.com/en/ProductDetail_15_77.htmlyou 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.

author: Benta
author_rank: Super Contributor
timestamp: February 10, 2019, 09:32:53 pm
content: 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.

author: cs.dk
author_rank: Unknown
timestamp: February 11, 2019, 07:55:24 am
content: 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/

author: Jeroen3
author_rank: Super Contributor
timestamp: February 11, 2019, 08:00:51 am
content: Maybe a used Fluke i1010?

author: TERRA Operative
author_rank: Super Contributor
timestamp: February 11, 2019, 08:28:20 am
content: Quote from: Benta on February 10, 2019, 09:32:53 pmThis. 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.

author: Ian.M
author_rank: Super Contributor
timestamp: February 11, 2019, 08:29:16 am
content: 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.