Yes, low sampling rates are a confounding influence. You can get a better idea by sampling the sampling. Don't just take 1 reading take many. For really short duration spikes you might never find it, but is they last say 1/10th of the sampling rate then you might catch them or at least the slope of them on the way up or down. There is also the problem that they are probably also averaging a bit so spikes look smaller than they really are. This is where an oscilloscope shines. An old analog one is actually better for spotting glitches and spikes than a newer digital scope.
On Wed, Apr 30, 2014 at 6:11 AM, Michael K Johnson <mcda...@gmail.com>wrote: > Even with peak hold, you're limited by the sampling rate > on the DMM. > > My DMM has a clamp. I set it up to peak hold voltage, and > it showed no back EMF from my motor when I turned off > power, so I thought it had an internal flyback diode and > did not install one externally. > > Then I used the clamp ammeter and peak hold, and I got > wildly different peak current measurements. That got me > to pull out the specifications and discover that the sampling > rate was lower than I expected, so peak hold wasn't very > meaningful regarding inrush current. > > That has made me suspect that I need to add a flyback > diode too, even though I never detected any back EMF > with peak hold voltage. > > > On Wed, Apr 30, 2014 at 12:15 AM, David Nelson <gizm...@gmail.com> wrote: > > My B&D CMM1000 24V 19" mower, IIRC, pulls just under 10A when not > > cutting and something over 20A on initial surge on startup. I only > > have a digital clamp meter that doesn't react fast enough to know the > > peak current. Maybe I should look to see if it has a peak hold option. > > > > On Tue, Apr 29, 2014 at 2:56 PM, Michael Ross <michael.e.r...@gmail.com> > wrote: > >> EVDL Dave R., > >> > >> Comparing on a weight basis $/lb (on the theory that weigh goes with Pb > >> content which goes with quality of design and manufacture and looking > at $/ > >> Ah: > >> > >> *#1 13lb* $3.46/lb @ $45 17.2 Ah *$2.62/Ah* > >> > http://www.atbatt.com/genesis-np18-12-12v-172ah-sealed-lead-acid-battery-with-nb-terminal.asp?cr_brand=BB&cr_product=BP17-12#specifications > >> *Is this the "Hawker Genesis" you were talking about?* > >> > >> *#2 14lb* $3.57/lb @ $50 21.6Ah *$2.31/Ah* > >> this one weighs an additional pound for $5 more: > >> http://www.atbatt.com/power-sonic-psh-12180nb-fr-sealed-lead-acid- > >> battery.asp?cr_brand=BB&cr_product=BP17-12 > >> > >> *#3 14.1lb* $4.15/lb @ $58.5 22Ah *$2.63/Ah* > >> > http://www.atbatt.com/amstron-12v-22ah-electric-vehicle-agm-battery-nb-terminal.asp?cr_brand=BB&cr_product=BP17-12#specifications > >> > >> *#4 14.4lb* $4.38/lb @ $63 18Ah *$3.50/Ah* > >> > http://www.atbatt.com/bb-bp18-12-12v-18ah-agm-battery-w-nb-terminal.asp?cr_brand=BB&cr_product=BP17-12#specifications > >> > >> *#5 14.5lb* $4.96/lb @ $72 20Ah *$3.60/Ah* > >> > http://www.atbatt.com/bb-battery-hr22-12-sla-battery.asp?cr_brand=BB&cr_product=BP17-12 > >> > >> *#6 15lb *$6.60/lb @ $100 20Ah* $5.00/Ah* > >> > http://www.atbatt.com/bb-evp20-12-12v-20ah-agm-battery-w-nb-terminal.asp?cr_brand=BB&cr_product=BP17-12 > >> > >> Raises all sorts of questions... > >> > >> Is #3 lying about the Ah? Does the low weigh really me it is not as > good > >> as say #5 which weighs a 180 grams more for an additional $14 each? > >> > >> On a pure money for performance basis one of the lowest weigh, least > >> expensive #2 seems like a good deal. Can 21.6Ah be believed? > >> > >> Is there any merit at all to buying #6? Its price point looks terrible, > >> but on the weight theory is is best. > >> > >> This is a great way for me to learn here, if you all are willing to > chime > >> in... > >> > >> Mike > >> > >> > >> On Tue, Apr 29, 2014 at 1:11 PM, EVDL Administrator <evp...@drmm.net> > wrote: > >> > >>> On 29 Apr 2014 at 12:06, Lee Hart wrote: > >>> > >>> > I have Enersys, Hawker, and Concorde AGMs that are now over 10 years > old > >>> > and still delivering at least half of their original capacity. I also > >>> have > >>> > Gates, and Deka gels just as old that are still usable. > >>> > >>> I just recently retired the last of a batch of Hawker Genesis AGMs that > >>> dated from about 1997. They were (well-) used when I got them. > >>> > >>> Of 24 equally old Deka Dominator gels, I'm still using 16 (and a couple > >>> others sit around). Most have 60-90% of their rated capacity. > >>> > >>> One of the things I like about these batteries is how low their self > >>> discharge is. They need only very infrequent charging when in storage. > >>> > >>> David Roden - Akron, Ohio, USA > >>> EVDL Administrator > >>> > >>> = = = = = = = = = = = = = = = = = = = = = = = = = = = = = > >>> EVDL Information: http://www.evdl.org/help/ > >>> = = = = = = = = = = = = = = = = = = = = = = = = = = = = = > >>> Note: mail sent to "evpost" and "etpost" addresses will not > >>> reach me. To send a private message, please obtain my > >>> email address from the webpage http://www.evdl.org/help/ . > >>> = = = = = = = = = = = = = = = = = = = = = = = = = = = = = > >>> > >>> > >>> _______________________________________________ > >>> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > >>> http://lists.evdl.org/listinfo.cgi/ev-evdl.org > >>> For EV drag racing discussion, please use NEDRA ( > >>> http://groups.yahoo.com/group/NEDRA) > >>> > >>> > >> > >> > >> -- > >> Put this question to yourself: should I use everyone else to attain > >> happiness, or should I help others gain happiness? > >> *Dalai Lama * > >> > >> Tell me what it is you plan to do > >> With your one wild and precious life? > >> Mary Oliver, "The summer day." > >> > >> To invent, you need a good imagination and a pile of junk. > >> Thomas A. Edison< > http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html> > >> > >> A public-opinion poll is no substitute for thought. > >> *Warren Buffet* > >> > >> Michael E. Ross > >> (919) 550-2430 Land > >> (919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google > Phone > >> (919) 631-1451 Cell > >> (919) 513-0418 Desk > >> > >> michael.e.r...@gmail.com > >> <michael.e.r...@gmail.com> > >> -------------- next part -------------- > >> An HTML attachment was scrubbed... > >> URL: < > http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140429/444c4ae3/attachment.htm > > > >> _______________________________________________ > >> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > >> http://lists.evdl.org/listinfo.cgi/ev-evdl.org > >> For EV drag racing discussion, please use NEDRA ( > http://groups.yahoo.com/group/NEDRA) > >> > > > > > > > > -- > > David D. Nelson > > http://evalbum.com/1328 > > http://www.levforum.com > > _______________________________________________ > > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > > For EV drag racing discussion, please use NEDRA ( > http://groups.yahoo.com/group/NEDRA) > > > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > For EV drag racing discussion, please use NEDRA ( > http://groups.yahoo.com/group/NEDRA) > > -- Put this question to yourself: should I use everyone else to attain happiness, or should I help others gain happiness? *Dalai Lama * Tell me what it is you plan to do With your one wild and precious life? Mary Oliver, "The summer day." To invent, you need a good imagination and a pile of junk. Thomas A. Edison<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html> A public-opinion poll is no substitute for thought. *Warren Buffet* Michael E. Ross (919) 550-2430 Land (919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google Phone (919) 631-1451 Cell (919) 513-0418 Desk michael.e.r...@gmail.com <michael.e.r...@gmail.com> -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140430/0db3c435/attachment.htm> _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
