Modules dying when 24V vehicles are jump started
in [Design]
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From: Grant on 3 Jul 2010 23:34 On Sun, 04 Jul 2010 12:57:20 +1000, Grant <omg(a)grrr.id.au> wrote: >On Sat, 3 Jul 2010 15:48:04 -0700 (PDT), Tom Gootee <tomg(a)fullnet.com> wrote: > >>On Jul 3, 4:05 pm, n...(a)puntnl.niks (Nico Coesel) wrote: >>> 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. >>> >>> >Modifying the systems themselves is not a viable option. And we do >>> >not yet understand the exact failure mechanism that is occurring. We >>> >do know that there is an internal SMPS upstream from the at-risk >>> >module, but don't have schematics for the system. The system draws >>> >about 35 Amps continuously, when operating. >>> >>> >Knowing only that, is there something that could be strapped across >>> >the system's DC power terminals that would prevent damage from jump >>> >starting? Something available off-the-shelf would be ideal. If >>> >nothing already exists, what might work? >>> >>> I recall a similar problem. It turned out an inductor in series with >>> the power was causing overshoots on the power supply rail big enough >>> to kill an opamp. A big capacitor solved the problem. >>> >>> OTOH: in 12V automotive systems people usually design stuff to >>> withstand 60V (IIRC) spikes on the power rails. >>> >>> -- >>> Failure does not prove something is impossible, failure simply >>> indicates you are not using the right tools... >>> nico(a)nctdevpuntnl (punt=.) >>> --------------------------------------------------------------- Hide quoted text - >>> >>> - Show quoted text - >> >>Well, we probably have 20 feet of heavy wire between the system and >>where it connects directly to the vehicle's batterries. But our >>system is not drawing any current when the problem occurs. > >The 1.5kW are good for this, the unipolar ones are like a big zener, ^^^^-> Oops TVS diodes >but with defined behaviour below the zener voltage, as well as the >behaviour during the high current overload period. > >Use several in series/parallel. On 24V systems here I use 2 x 16V >in series. On a motor drive system recently I had 3 x 16V in series >for 48V turn on and they were getting warm! > >Dunno how you can measure spike suppression in your situation, so it's >batter to put 2 or 3 times what you first think of in there. The TVS >diodes are quite cheap, and are rated for repeat operation, unlike >varistor type spike suppression. > >I suggest unipolar TVS diodes for your situation, probably multiple >devices in parallel across the 24V power input. > >What's the highest normal voltage? The TVS voltage must be a little >higher than that, then select number of then for the expected, plus >some, overload power absorption. Follow the TVS devices with more >spike suppression to reduce the high power voltage down to something >your input circuit can handle. Watch the grounding to your thingy, >as the battery return line will change voltage too -- this may >affect other I/O lines connected to the unit. > >Grant.
From: BobS on 4 Jul 2010 02:06 On Jul 3, 10:34 pm, Grant <o...(a)grrr.id.au> wrote: > On Sun, 04 Jul 2010 12:57:20 +1000, Grant <o...(a)grrr.id.au> wrote: > >On Sat, 3 Jul 2010 15:48:04 -0700 (PDT), Tom Gootee <t...(a)fullnet.com> wrote: > > >>On Jul 3, 4:05 pm, n...(a)puntnl.niks (Nico Coesel) wrote: > >>> 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. > > >>> >Modifying the systems themselves is not a viable option. And we do > >>> >not yet understand the exact failure mechanism that is occurring. We > >>> >do know that there is an internal SMPS upstream from the at-risk > >>> >module, but don't have schematics for the system. The system draws > >>> >about 35 Amps continuously, when operating. > > >>> >Knowing only that, is there something that could be strapped across > >>> >the system's DC power terminals that would prevent damage from jump > >>> >starting? Something available off-the-shelf would be ideal. If > >>> >nothing already exists, what might work? > > >>> I recall a similar problem. It turned out an inductor in series with > >>> the power was causing overshoots on the power supply rail big enough > >>> to kill an opamp. A big capacitor solved the problem. > > >>> OTOH: in 12V automotive systems people usually design stuff to > >>> withstand 60V (IIRC) spikes on the power rails. > > >>> -- > >>> Failure does not prove something is impossible, failure simply > >>> indicates you are not using the right tools... > >>> nico(a)nctdevpuntnl (punt=.) > >>> --------------------------------------------------------------- Hide quoted text - > > >>> - Show quoted text - > > >>Well, we probably have 20 feet of heavy wire between the system and > >>where it connects directly to the vehicle's batterries. But our > >>system is not drawing any current when the problem occurs. > > >The 1.5kW are good for this, the unipolar ones are like a big zener, > > ^^^^-> Oops TVS diodes > > > > >but with defined behaviour below the zener voltage, as well as the > >behaviour during the high current overload period. > > >Use several in series/parallel. On 24V systems here I use 2 x 16V > >in series. On a motor drive system recently I had 3 x 16V in series > >for 48V turn on and they were getting warm! > > >Dunno how you can measure spike suppression in your situation, so it's > >batter to put 2 or 3 times what you first think of in there. The TVS > >diodes are quite cheap, and are rated for repeat operation, unlike > >varistor type spike suppression. > > >I suggest unipolar TVS diodes for your situation, probably multiple > >devices in parallel across the 24V power input. > > >What's the highest normal voltage? The TVS voltage must be a little > >higher than that, then select number of then for the expected, plus > >some, overload power absorption. Follow the TVS devices with more > >spike suppression to reduce the high power voltage down to something > >your input circuit can handle. Watch the grounding to your thingy, > >as the battery return line will change voltage too -- this may > >affect other I/O lines connected to the unit. > > >Grant.- Hide quoted text - > > - Show quoted text -- Hide quoted text - > > - Show quoted text - Some pointers on electronics components on vehicles; Have you examined the failed modules to see which components are being killed? There maybe some clues to what needs to be done to save them and a easy fix. Generally 28V is considered the operating voltage of 24V systems. Some operational conditions can exceed 28V. See below. SAE has recommended standards for design and test of vehicle electronics. The transients in http://www.industrologic.com/autotransients..pdf cover some of the same conditions as SAE. Electronic components designed and tested to SAE standards usually do not have problems when installed on vehicles. Remember 12V levels must be multiplied by 2 for 28V systems. Jump starts with dead or low batteries can cause a series of positive and negative transients from multiple components Protection MUST be included for reverse voltage transients and jumps. High current electronic modules may require active protection circuits to block high supply voltages and transients. Generally, transient suppression should protect only the electronic module, not suppress the entire vehicle electrical system. Suppressing the vehicle is the hard, expensive (it will come back to bite you), and iffy way to protect a module. Adding TVSs ahead of your module is a band aid for suppressing the vehicle. This subjects the TVSs to anything the vehicle can throw at them now and in the future. When you do not control the vehicle design, configuration, or operation you must look out for your module the best you can, regardless of what happens to the vehicle. Look into a fast circuit to turn off power to your module with low and over voltage plus reverse voltage. Next time design and test your modules to SAE transient and EMI standards. Also make sure all the module I/O (except power) is electrically isolated from the vehicle and other electronics.
From: Richard Henry on 4 Jul 2010 02:22 On Jul 3, 11:06 pm, BobS <rns...(a)execpc.com> wrote: > On Jul 3, 10:34 pm, Grant <o...(a)grrr.id.au> wrote: > > > > > On Sun, 04 Jul 2010 12:57:20 +1000, Grant <o...(a)grrr.id.au> wrote: > > >On Sat, 3 Jul 2010 15:48:04 -0700 (PDT), Tom Gootee <t...(a)fullnet.com> wrote: > > > >>On Jul 3, 4:05 pm, n...(a)puntnl.niks (Nico Coesel) wrote: > > >>> 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. > > > >>> >Modifying the systems themselves is not a viable option. And we do > > >>> >not yet understand the exact failure mechanism that is occurring. We > > >>> >do know that there is an internal SMPS upstream from the at-risk > > >>> >module, but don't have schematics for the system. The system draws > > >>> >about 35 Amps continuously, when operating. > > > >>> >Knowing only that, is there something that could be strapped across > > >>> >the system's DC power terminals that would prevent damage from jump > > >>> >starting? Something available off-the-shelf would be ideal. If > > >>> >nothing already exists, what might work? > > > >>> I recall a similar problem. It turned out an inductor in series with > > >>> the power was causing overshoots on the power supply rail big enough > > >>> to kill an opamp. A big capacitor solved the problem. > > > >>> OTOH: in 12V automotive systems people usually design stuff to > > >>> withstand 60V (IIRC) spikes on the power rails. > > > >>> -- > > >>> Failure does not prove something is impossible, failure simply > > >>> indicates you are not using the right tools... > > >>> nico(a)nctdevpuntnl (punt=.) > > >>> --------------------------------------------------------------- Hide quoted text - > > > >>> - Show quoted text - > > > >>Well, we probably have 20 feet of heavy wire between the system and > > >>where it connects directly to the vehicle's batterries. But our > > >>system is not drawing any current when the problem occurs. > > > >The 1.5kW are good for this, the unipolar ones are like a big zener, > > > ^^^^-> Oops TVS diodes > > > >but with defined behaviour below the zener voltage, as well as the > > >behaviour during the high current overload period. > > > >Use several in series/parallel. On 24V systems here I use 2 x 16V > > >in series. On a motor drive system recently I had 3 x 16V in series > > >for 48V turn on and they were getting warm! > > > >Dunno how you can measure spike suppression in your situation, so it's > > >batter to put 2 or 3 times what you first think of in there. The TVS > > >diodes are quite cheap, and are rated for repeat operation, unlike > > >varistor type spike suppression. > > > >I suggest unipolar TVS diodes for your situation, probably multiple > > >devices in parallel across the 24V power input. > > > >What's the highest normal voltage? The TVS voltage must be a little > > >higher than that, then select number of then for the expected, plus > > >some, overload power absorption. Follow the TVS devices with more > > >spike suppression to reduce the high power voltage down to something > > >your input circuit can handle. Watch the grounding to your thingy, > > >as the battery return line will change voltage too -- this may > > >affect other I/O lines connected to the unit. > > > >Grant.- Hide quoted text - > > > - Show quoted text -- Hide quoted text - > > > - Show quoted text - > > Some pointers on electronics components on vehicles; > > Have you examined the failed modules to see which components are being > killed? There maybe some clues to what needs to be done to save them > and a easy fix. > > Generally 28V is considered the operating voltage of 24V systems. > Some operational conditions can exceed 28V. See below. > > SAE has recommended standards for design and test of vehicle > electronics. The transients inhttp://www.industrologic.com/autotransients.pdf > cover some of the same conditions as SAE. Electronic components > designed and tested to SAE standards usually do not have problems when > installed on vehicles. Remember 12V levels must be multiplied by 2 > for 28V systems. > > Jump starts with dead or low batteries can cause a series of positive > and negative transients from multiple components > > Protection MUST be included for reverse voltage transients and jumps. > > High current electronic modules may require active protection circuits > to block high supply voltages and transients. > > Generally, transient suppression should protect only the electronic > module, not suppress the entire vehicle electrical system. > Suppressing the vehicle is the hard, expensive (it will come back to > bite you), and iffy way to protect a module. Adding TVSs ahead of > your module is a band aid for suppressing the vehicle. This subjects > the TVSs to anything the vehicle can throw at them now and in the > future. When you do not control the vehicle design, configuration, or > operation you must look out for your module the best you can, > regardless of what happens to the vehicle. > > Look into a fast circuit to turn off power to your module with low and > over voltage plus reverse voltage. > > Next time design and test your modules to SAE transient and EMI > standards. Also make sure all the module I/O (except power) is > electrically isolated from the vehicle and other electronics. 12V jump-start systems on Auto Club tow trucks often use 2 batteries in series in order to guarantee a good boost, especially in cold- weather areas. I don't know if similar tricks are used for 24V systems.
From: Grant on 4 Jul 2010 03:27 On Sat, 3 Jul 2010 23:06:32 -0700 (PDT), BobS <rnscrs(a)execpc.com> wrote: >On Jul 3, 10:34 pm, Grant <o...(a)grrr.id.au> wrote: >> On Sun, 04 Jul 2010 12:57:20 +1000, Grant <o...(a)grrr.id.au> wrote: >> >On Sat, 3 Jul 2010 15:48:04 -0700 (PDT), Tom Gootee <t...(a)fullnet.com> wrote: >> >> >>On Jul 3, 4:05 pm, n...(a)puntnl.niks (Nico Coesel) wrote: >> >>> 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. >> >> >>> >Modifying the systems themselves is not a viable option. And we do >> >>> >not yet understand the exact failure mechanism that is occurring. We >> >>> >do know that there is an internal SMPS upstream from the at-risk >> >>> >module, but don't have schematics for the system. The system draws >> >>> >about 35 Amps continuously, when operating. >> >> >>> >Knowing only that, is there something that could be strapped across >> >>> >the system's DC power terminals that would prevent damage from jump >> >>> >starting? Something available off-the-shelf would be ideal. If >> >>> >nothing already exists, what might work? >> >> >>> I recall a similar problem. It turned out an inductor in series with >> >>> the power was causing overshoots on the power supply rail big enough >> >>> to kill an opamp. A big capacitor solved the problem. >> >> >>> OTOH: in 12V automotive systems people usually design stuff to >> >>> withstand 60V (IIRC) spikes on the power rails. >> >> >>> -- >> >>> Failure does not prove something is impossible, failure simply >> >>> indicates you are not using the right tools... >> >>> nico(a)nctdevpuntnl (punt=.) >> >>> --------------------------------------------------------------- Hide quoted text - >> >> >>> - Show quoted text - >> >> >>Well, we probably have 20 feet of heavy wire between the system and >> >>where it connects directly to the vehicle's batterries. But our >> >>system is not drawing any current when the problem occurs. >> >> >The 1.5kW are good for this, the unipolar ones are like a big zener, >> >> ^^^^-> Oops TVS diodes >> >> >> >> >but with defined behaviour below the zener voltage, as well as the >> >behaviour during the high current overload period. >> >> >Use several in series/parallel. On 24V systems here I use 2 x 16V >> >in series. On a motor drive system recently I had 3 x 16V in series >> >for 48V turn on and they were getting warm! >> >> >Dunno how you can measure spike suppression in your situation, so it's >> >batter to put 2 or 3 times what you first think of in there. The TVS >> >diodes are quite cheap, and are rated for repeat operation, unlike >> >varistor type spike suppression. >> >> >I suggest unipolar TVS diodes for your situation, probably multiple >> >devices in parallel across the 24V power input. >> >> >What's the highest normal voltage? The TVS voltage must be a little >> >higher than that, then select number of then for the expected, plus >> >some, overload power absorption. Follow the TVS devices with more >> >spike suppression to reduce the high power voltage down to something >> >your input circuit can handle. Watch the grounding to your thingy, >> >as the battery return line will change voltage too -- this may >> >affect other I/O lines connected to the unit. >> >> >Grant.- Hide quoted text - >> >> - Show quoted text -- Hide quoted text - >> >> - Show quoted text - > >Some pointers on electronics components on vehicles; > >Have you examined the failed modules to see which components are being >killed? There maybe some clues to what needs to be done to save them >and a easy fix. > >Generally 28V is considered the operating voltage of 24V systems. >Some operational conditions can exceed 28V. See below. Why are you quoting me here? 'Snot my problem. Grant. > >SAE has recommended standards for design and test of vehicle >electronics. The transients in http://www.industrologic.com/autotransients.pdf >cover some of the same conditions as SAE. Electronic components >designed and tested to SAE standards usually do not have problems when >installed on vehicles. Remember 12V levels must be multiplied by 2 >for 28V systems. > >Jump starts with dead or low batteries can cause a series of positive >and negative transients from multiple components > >Protection MUST be included for reverse voltage transients and jumps. > >High current electronic modules may require active protection circuits >to block high supply voltages and transients. > >Generally, transient suppression should protect only the electronic >module, not suppress the entire vehicle electrical system. >Suppressing the vehicle is the hard, expensive (it will come back to >bite you), and iffy way to protect a module. Adding TVS's ahead of >your module is a band aid for suppressing the vehicle. This subjects >the TVS's to anything the vehicle can throw at them now and in the >future. When you do not control the vehicle design, configuration, or >operation you must look out for your module the best you can, >regardless of what happens to the vehicle. > >Look into a fast circuit to turn off power to your module with low and >over voltage plus reverse voltage. > >Next time design and test your modules to SAE transient and EMI >standards. Also make sure all the module I/O (except power) is >electrically isolated from the vehicle and other electronics.
From: Graeme Zimmer on 4 Jul 2010 03:57
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 |