Modules dying when 24V vehicles are jump started
in [Design]
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From: Raveninghorde on 4 Jul 2010 04:52 On Sun, 4 Jul 2010 17:57:53 +1000, "Graeme Zimmer" <gzimmer(a)wideband.net.au> wrote: >Hi Tom, > >Are you familiar with "Load Dump" testing? Briefly it is a set of tests >specifically designed to avoid this problem. Various Standards require that >equipment designed for Automotive use must pass this test. > >Briefly, a "Load Dump" is what happens when a vehicle with a flat (or >faulty) battery is jump started. When the motor first fires up it charges a >very high current into the loaner battery. When the leads are removed this >current has nowhere to go (the main battery has a high resistance), so there >is a huge voltage spike generated in the vehicle wiring due to the magnetic >energy stored in the Alternator (e.g. the alternator cannot stop generating >instantly). > >The laboratory test for this dumps a large bank of Electrolytic capacitors >(charged to 200V) across the device. It causes indicator lights to explode >like flash bulbs. Lots of fun. > >The design cure is either a series voltage regulator which can withstand the >voltage spike, or a large MOV across the rail, sufficient to absorb the >energy spike. It needs to be a big one. > >Regards ................ Zim > This is all covered in MIL-STD-1275
From: Baron on 4 Jul 2010 06:51 Tom Gootee Inscribed thus: >> >> On Sat, 3 Jul 2010 12:52:10 -0700 (PDT), Tom Gootee >> >> <t...(a)fullnet.com> wrote: >> >> >> >We provide support for a number of systems installed in 24V >> >> >vehicles. When the vehicles are not in use, the users like to >> >> >leave the system's main power switch and circuit breaker both in >> >> >the on position. If the vehicle then needs to be jump started, >> >> >the users often do not first turn off the system's circuit >> >> >breaker or power switch, despite continuing attempts at training >> >> >them. Jump starting under those conditions tends to destroy a >> >> >very expensive electronic module in the system. The fact that the manufacturers fit a main power switch seems to suggest that this is a known failure condition. A bit like the warning labels on cars that tell you to disconnect the battery before performing any electric welding on the vehicle. -- Best Regards: Baron.
From: Joerg on 4 Jul 2010 20:56 Tom Gootee wrote: > On Jul 3, 5:05 pm, Muzaffer Kal <k...(a)dspia.com> wrote: [...] >> One solution would be to use a protection circuit at the input of the >> system using an IC like LT4356 or a discrete implementation of the >> same:http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1142,C1... Way to go. Although this one (as most others) is limited to 80V and for a truck with a 24V system that's borderline. Might have to roll your own here. >> -- >> Muzaffer Kal >> >> DSPIA INC. >> ASIC/FPGA Design Services >> >> http://www.dspia.com- Hide quoted text - >> >> - Show quoted text - > > Yeah, that type of circuit would be nice. Jim Thompson also has one > that's similar in effect I think, but all discretes. And Maxim has a > discrete version schematic of something similar in some literature > about a similar IC they sell. > > Does anyone know if there any COTS products (already available) that > use something like that? > Not for 24V but you could ask these guys: http://www.advancesurgesuppressor.com/#DC The market is small thouygh because most equipment is properly designed to handle those load change surges or, ahem, "unusual" jump-start methods. In aircraft it has to or it won't be certified. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Joerg on 4 Jul 2010 21:00 Tom Gootee wrote: [...] > ... But it seems like a > TVS or Zener clamping circuit would be a lot cheaper and smaller, and > maybe more reliable and robust, and should work well-enough. And they > are available and ready to use as is. There are too many of these > systems out there to spend a lot of money on each one. That one you can buy as a COTS module, ready to wire up, at the company I pointed out in the other post. However, they use MOVs whivh have a finite number of times they can be hit. It's like an energy bank account, when the balance is used up ... *PHUT* ... a fuse in the module blows. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: StickThatInYourPipeAndSmokeIt on 5 Jul 2010 13:38
On Tue, 06 Jul 2010 01:21:58 +0800, Werner <wdahn(a)netfront.net> wrote: > >In addition to all the remedy suggestions, one could try to avoid to >have to jumpstart in the first place. I take it there is quite a drain >on the battery when the alternator isn't providing. You could remind the >operator that he is living on borrowed time with an obnoxious beeper or >something. > >Regards, >Werner The failure mode of the device is important. Is it failing due to a low voltage feed, causing it to blow its own internal regulation circuitry, or are voltage spikes from the started windings getting injected through its power circuitry and into the device, blowing a more sensitive component? Would not a line conditioner (DC) in the power feed to this device fix it? You know, like the car stereo guys use... a supercap bank. The other way is to wire up a switch in the engine bay that allows it to be disconnected during a jump event. |