Question (about 'jump starting')
02-10-2005, 09:54 PM
#17
Three Wheelin'
Join Date: Oct 2004
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What about a jump start emergency battery pack? You know, the ones with a handle that you plug into the wall to charge. They don't turn on unless they are properly connected. You can hear it click on and the light turns on once the positive is connected to the battery and the negative is grounded on the chassis. If you try to connect the two posts, it won't turn on. Would that eliminate the chance of a spike?
02-10-2005, 10:23 PM
#18
Nordschleife Master
Just my .02,
I do believe it is a combination of some of the vulnerabilities of an 'aged' LH brain as mentioned in the earlier part of this thread and the threat of a potential spike of a jump start. I lost an LH brain due to some unknowns about two years ago (not a jump) but prefer to go about maintaining a fresh battery. If it does need a charge I do what another post mentioned to disconnect the battery and charge it for 15 or so minutes. I needed this at John Wayne Airport - tow truck driver was a bit amused, but commented that he had not seen a 5 speed 928S4 in years and was not sure where to find the battery anyhow. Kind of funny. I just replace the battery every couple of years. Inexpensive and cheap insurance.
I do believe it is a combination of some of the vulnerabilities of an 'aged' LH brain as mentioned in the earlier part of this thread and the threat of a potential spike of a jump start. I lost an LH brain due to some unknowns about two years ago (not a jump) but prefer to go about maintaining a fresh battery. If it does need a charge I do what another post mentioned to disconnect the battery and charge it for 15 or so minutes. I needed this at John Wayne Airport - tow truck driver was a bit amused, but commented that he had not seen a 5 speed 928S4 in years and was not sure where to find the battery anyhow. Kind of funny. I just replace the battery every couple of years. Inexpensive and cheap insurance.
02-11-2005, 12:07 AM
#19
There might be an explanation in the WSM's RE: why you don't jump at the battery.
I'll look this weekend.
Every owner's manual I've ever browsed say's to jump start from the front Pole/Jump point.
The owners manual doesn't say why.
Unless there is some special capacitance/resistance built into the Pole I don't see why it would prevent a spike as well. I mean you aren't bypassing the ECU, fuel pump, dash, warning brain,
So what gives? Speak, Speake...
I'll look this weekend.
Every owner's manual I've ever browsed say's to jump start from the front Pole/Jump point.
The owners manual doesn't say why.
Unless there is some special capacitance/resistance built into the Pole I don't see why it would prevent a spike as well. I mean you aren't bypassing the ECU, fuel pump, dash, warning brain,
So what gives? Speak, Speake...
02-11-2005, 06:37 AM
#20
Rennlist Member
It is true that the LH is particularly vunerable to spikes. My preferred method of getting a dead 928 started is to try and use the donor car to get some charge into the 928s battery. On no account start the engine of the donor car.
Wait 10 minutes or so. Then try to start the car.
The same goes when using one of the battery starter packs.
I don't believe that starting from the jump terminal is any more "risky" that direct on the battery.
On no account use a "boost" rapid charger or similar, some of these devices can give out dangerously high voltages.
The more discharged the 928s battery, the higher the risks.
Wait 10 minutes or so. Then try to start the car.
The same goes when using one of the battery starter packs.
I don't believe that starting from the jump terminal is any more "risky" that direct on the battery.
On no account use a "boost" rapid charger or similar, some of these devices can give out dangerously high voltages.
The more discharged the 928s battery, the higher the risks.
02-11-2005, 07:05 AM
#21
Instructor
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I don't have a manual for my 928. Could someone please describe the procedure recommended by Porsche for a jump start.
I would have thought there would be no issue jumping any car provided there is a spike protector unit on the jumper leads or if it is a frequent problem, then wired into the battery. I have had ,y 951 jumped a few times and each time I have had the AA equivalent show me the spike protector before hand - no problems have resulted.
I would have thought there would be no issue jumping any car provided there is a spike protector unit on the jumper leads or if it is a frequent problem, then wired into the battery. I have had ,y 951 jumped a few times and each time I have had the AA equivalent show me the spike protector before hand - no problems have resulted.
02-11-2005, 09:10 AM
#22
Ebs,
No time right now -heading to work-.
I'll give it to you word for word, tonight. O.K.?
It will probably start a flurry of anecdotal reply's but such is life.
Oddly, I think it even backs-up the sequence of connecting/disconnecting
the pos and neg. leads as I was taught on the farm and in the Army.
An order that was for some reason considered bogus by some on the Renn.
Later
No time right now -heading to work-.
I'll give it to you word for word, tonight. O.K.?
It will probably start a flurry of anecdotal reply's but such is life.
Oddly, I think it even backs-up the sequence of connecting/disconnecting
the pos and neg. leads as I was taught on the farm and in the Army.
An order that was for some reason considered bogus by some on the Renn.
Later
02-11-2005, 10:11 AM
#23
Rennlist Member
Originally Posted by John Struthers
There might be an explanation in the WSM's RE: why you don't jump at the battery.
I'll look this weekend.
Every owner's manual I've ever browsed say's to jump start from the front Pole/Jump point.
The owners manual doesn't say why.
Unless there is some special capacitance/resistance built into the Pole I don't see why it would prevent a spike as well. I mean you aren't bypassing the ECU, fuel pump, dash, warning brain,
So what gives? Speak, Speake...
I'll look this weekend.
Every owner's manual I've ever browsed say's to jump start from the front Pole/Jump point.
The owners manual doesn't say why.
Unless there is some special capacitance/resistance built into the Pole I don't see why it would prevent a spike as well. I mean you aren't bypassing the ECU, fuel pump, dash, warning brain,
So what gives? Speak, Speake...
Re the front (jump) post, I believe it to be no more/no less than a convenience as the battery is buried in the rear: there are no electrical gizmos, like capicators, showing in the circuit path.
My BMW has exactly the same under hood 'jump' post - for the same reason: to access the battery, the rear seat must be removed!
02-11-2005, 11:17 AM
#24
Rennlist Member
Rennlist Site Sponsor
Page 28-44 in the manual:
1. Never start the car without a firmly connected battery.
2. Mixing up power supply connections, e.g. wrong connection of battery, could lead to destruction of control units.
3. Never disconnect battery while engine is running.
4. Never use a boost battery charger to start the engine. Only use a second 12 V battery for outside starting help.
5. Disconnect battery from car network before boost charging.
There are more such statements, but they get into testing, etc.
If you are careful in hooking up the jumper cables, there should be no problem with jump-starting a 928 from another battery.
One comment about the jump start terminal under the hood - it works, and is the suggested method - but the wire from there to the starter is surprisingly small, compared to the battery cables.
1. Never start the car without a firmly connected battery.
2. Mixing up power supply connections, e.g. wrong connection of battery, could lead to destruction of control units.
3. Never disconnect battery while engine is running.
4. Never use a boost battery charger to start the engine. Only use a second 12 V battery for outside starting help.
5. Disconnect battery from car network before boost charging.
There are more such statements, but they get into testing, etc.
If you are careful in hooking up the jumper cables, there should be no problem with jump-starting a 928 from another battery.
One comment about the jump start terminal under the hood - it works, and is the suggested method - but the wire from there to the starter is surprisingly small, compared to the battery cables.
02-11-2005, 12:35 PM
#25
The most problematic battery situation occurs when a charger is used on
a battery still in the car, which is fully discharged. Some chargers can
put out voltages in excess of 18 - 20 volts when charging a fully discharged
battery. The worst type of charger is the one used mainly in body shops to
boost the battery immediately for starting. This will in most cases surely
damage the 928 LH unit. Also, other car electronics will most likely be damaged
too, e.g. radios, electronic antennas, etc.
Jumping an in-the-car battery which is partially discharged using a battery
pack or from another car usually is not a problem. The case of a fully discharged
battery can result in very large currents causing battery damage or possibly
an explosion. As mentioned, if the jump is from another car, the engine should
not be running or the running car's alternator could be damaged. The main point
to remember is to prevent reverse jumping the battery by always connecting the
negative lead to the engine block and the postive lead of the jumper battery to
the other battery's postive terminal.
Bottomline: On 928s, and all late model cars, always disconnect the battery
when using a battery charger and NEVER use a booster charger on any car.
Also, one might consider removing the LH control unit if a late 928 is sent
to the body shop.
a battery still in the car, which is fully discharged. Some chargers can
put out voltages in excess of 18 - 20 volts when charging a fully discharged
battery. The worst type of charger is the one used mainly in body shops to
boost the battery immediately for starting. This will in most cases surely
damage the 928 LH unit. Also, other car electronics will most likely be damaged
too, e.g. radios, electronic antennas, etc.
Jumping an in-the-car battery which is partially discharged using a battery
pack or from another car usually is not a problem. The case of a fully discharged
battery can result in very large currents causing battery damage or possibly
an explosion. As mentioned, if the jump is from another car, the engine should
not be running or the running car's alternator could be damaged. The main point
to remember is to prevent reverse jumping the battery by always connecting the
negative lead to the engine block and the postive lead of the jumper battery to
the other battery's postive terminal.
Bottomline: On 928s, and all late model cars, always disconnect the battery
when using a battery charger and NEVER use a booster charger on any car.
Also, one might consider removing the LH control unit if a late 928 is sent
to the body shop.
02-11-2005, 12:47 PM
#26
Race Director
My car and my friends 87 both have had LH brain failures due to bad jump starts! Luckily for us it was with the prior owners!
The basic idea is to not have the voltage get too high, not much above 12V. So a jump from another (NON RUNNING) car should be fine, or one of those 12V jump packs (but they will have to be pretty strong the little ones don't have enough power). Again this is only if you are in a must start the car now situation.
If you have the time to do things the best way, then pull the battery....slow charge it overnight, reinstall & that should work! I also think the battery should be a regular maintence item, they are cheap & can save you alot of money later on! I plan on changing mine at about two year intervals!
The basic idea is to not have the voltage get too high, not much above 12V. So a jump from another (NON RUNNING) car should be fine, or one of those 12V jump packs (but they will have to be pretty strong the little ones don't have enough power). Again this is only if you are in a must start the car now situation.
If you have the time to do things the best way, then pull the battery....slow charge it overnight, reinstall & that should work! I also think the battery should be a regular maintence item, they are cheap & can save you alot of money later on! I plan on changing mine at about two year intervals!
02-11-2005, 01:30 PM
#27
Burning Brakes
Please define "must start the car now" situation. If it won't go at all, wouldn't that be a "must start now" situation? I'm trying to get some electrical gremlins sorted out and in order to drive in between gremlin "seek and destroy" missions, I have to jump in order to drive. Thinking of a booster pack, but again, I don't want to do anything to fry my electrics or birth any more gremlins. Thanks.
02-11-2005, 01:39 PM
#28
Rennlist Member
Originally Posted by 1981 Shark
Please define "must start the car now" situation. If it won't go at all, wouldn't that be a "must start now" situation? I'm trying to get some electrical gremlins sorted out and in order to drive in between gremlin "seek and destroy" missions, I have to jump in order to drive. Thinking of a booster pack, but again, I don't want to do anything to fry my electrics or birth any more gremlins. Thanks.
02-11-2005, 03:02 PM
#29
Rennlist Member
1981 Shark,
"Must start now" means stranded at roadside or similar ?
If just stuck at home, and you can use another vehicle, then you can take the time to charge the battery.
Your '81 at least doesn't have the dreaded LH 2.3 fitted from '87 onwards. But note what is in my Driver's Handbook... "before the battery is to be charged with a heavy duty charger, it must be disconnected, or otherwise the alternator can be destroyed"
Regards
"Must start now" means stranded at roadside or similar ?
If just stuck at home, and you can use another vehicle, then you can take the time to charge the battery.
Your '81 at least doesn't have the dreaded LH 2.3 fitted from '87 onwards. But note what is in my Driver's Handbook... "before the battery is to be charged with a heavy duty charger, it must be disconnected, or otherwise the alternator can be destroyed"
Regards
02-11-2005, 03:22 PM
#30
Burning Brakes
Thanks, John,
I'm learning more and more about it, but when jumping, I've followed the instructions to a "T",
Also, I'm getting differing opinions on jumping vs. not. I assume Porsche wouldn't have jump start instructions in the owner's manual unless it was OK to do so.
BTW, what is the LH unit?
Still learning as we go. Thanks.
-dmk
I'm learning more and more about it, but when jumping, I've followed the instructions to a "T",
Also, I'm getting differing opinions on jumping vs. not. I assume Porsche wouldn't have jump start instructions in the owner's manual unless it was OK to do so.
BTW, what is the LH unit?
Still learning as we go. Thanks.
-dmk