The effect of a voltage spike is to produce a corresponding increase in current (current spike).
However, some voltage spikes may be created by current sources.
Voltage would increase as necessary so that a constant current will flow. Current from a discharging inductor is one example.
For sensitive electronics, excessive current can flow if this voltage spike exceeds a material’s breakdown voltage, or if it causes avalanche breakdown.
In semiconductor junctions, excessive electric current may destroy or severely weaken that device. An avalanche diode, transient voltage suppression diode, transil, varistor, overvoltage crowbar, or **a range of other overvoltage protective devices can divert (shunt) this transient current thereby minimizing voltage.[**1]
While generally referred to as a voltage spike, the phenomenon in question is actually an energy spike, in that it is measured not in volts but in joules; a transient response defined by a mathematical product of voltage, current, and time.
So to summarise :
when your having a jump - - use protection .
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Surely it would be better for most truck to have a split charge system set up so that the drivers can use the second set of batteries for their electrical gear including fridges and not have a problem with the main battery. Then again, I guess if the batteries were good enough then you could fit parking lights for night time when you’re in that layby that needs lights so you’re not breaking the law when parking.
But I can see how some companies won’t want to fit such things. It would be helpful for the manufactures to fit it as standard too but that would just be more money and complication they might not want…
Jumped a Mactrans on the Contentin Tuesday morning in Poole, an old shape red man what a peice of shhhh it was, got a free meal with wine voucher, off the loading officer on the Contentin next time i,m on it
No probs for me with flat batteries as i just charge them one at a time from the fridge ,but be careful as if poles are connected wrong it will blow the fridge fuse, so for the experts only.
klunk/■■■■■■■■
Jumped a Mactrans on the Contentin Tuesday morning in Poole, an old shape red man what a peice of shhhh it was, got a free meal with wine voucher, off the loading officer on the Contentin next time i,m on it
No probs for me with flat batteries as i just charge them one at a time from the fridge ,but be careful as if poles are connected wrong it will blow the fridge fuse, so for the experts only.
I’m surprised more don’t do it but all our fridges and units are wired up with an Anderson lead. Often the 12 boost from the fridge is enough to get the truck going.
Surge Protectors are available for about £25, these clamp onto the battery or cable to prevent a surge. Mainly used to protect ECU, airbags and onboard computers
When I was a kid I bought an electric welder that ran off two car batteries, you could weld upto about 3/16’’ plate. But if you are welding on a trailer or lorry a surge protector saves disconnecting batteries and losing radio codes and clock settings.
You can also buy 9v code savers that plug in your cigar lighter to save the radio codes while the batteries are disconnected.
We also used to leave the engine running on a fast idle when welding and never had any problems
switchlogic:
But someone else said the spike occurs when you disconnect the jump leads.
In the 80’s that might happen, due to the way the alrernator works. But it won’t happen now.
When you connect the jump leads, the good vehicle’s alternator is supplying the power to the bad batteries, the bad batteries are soaking up as much power as they can. Once the bad vehicle is started, there’s 2 alternators feeding the batteries. Then when you disconnect the leads, the bad trucks alternator is doing all the work.
There’s a theory that it’s this step, when you disconnect the leads, and the bad vehicles alternator goes from ‘steady’ to ‘flat out’. In this day and age, current output ramps up, rather than just on or off. In a lot of cases, the ECU controls the alternator.
Wheel Nut:
But if you are welding on a trailer or lorry a surge protector saves disconnecting batteries
Won’t stop the alternator diodes burning out though. You’ve been lucky.
klunk/■■■■■■■■
No probs for me with flat batteries as i just charge them one at a time from the fridge ,but be careful as if poles are connected wrong it will blow the fridge fuse, so for the experts only.
Far worse than that, it can blow the circuit board, it happened to one belonging to a guy I was working for once, and Carrier wanted £1000 for the repair…Having said that, so long as you know what you are doing then yes, you can get a stricken truck going by charging the batteries individually using the fridge motor.
Cieranc, what is the reason for the advice often given in hand books to connect the negative jump cable to an chassis earth point on the dead vehicle and not to its neg battery terminal?
Driveroneuk:
Cieranc, what is the reason for the advice often given in hand books to connect the negative jump cable to an chassis earth point on the dead vehicle and not to its neg battery terminal?
Because you are supposed to stay away from the batteries when you make the final connection in case they explode. This can happen, especially in cold conditions and with a battery which is near the end of its life where the sulphuric acid mix is weakened.
Cieranc, what is the reason for the advice often given in hand books to connect the negative jump cable to an chassis earth point on the dead vehicle and not to its neg battery terminal?
h
If you connect the chasis together its easier to get it correct and not blow circuit boards ,ecus etc as harry says you have to know what you are doing or its expensive and you can blow the flat battery up.
Yep, safety thing. Makes it harder for numpties to get it wrong.
Also, for jump starting, the closer you can get the neg to the starter motor, the more power goes to the starter and the less absorbed by the bad batteries.
Not a problem when jumping off another vehicle (which will actually charge the flat one), but moreso when using a jump-pack, where you’ve only a set amount of power. You don’t want to use all that power to get the batteries nearly high enough to start the vehicle, or you’ll end up with both flat.
klunk/■■■■■■■■
Jumped a Mactrans on the Contentin Tuesday morning in Poole, an old shape red man what a peice of shhhh it was, got a free meal with wine voucher, off the loading officer on the Contentin next time i,m on it
No probs for me with flat batteries as i just charge them one at a time from the fridge ,but be careful as if poles are connected wrong it will blow the fridge fuse, so for the experts only.
Can you show Wee Stuart on your 61 plate how to do this so as he disnae have to phone me when his batterys go flat lol
Wheel Nut:
But if you are welding on a trailer or lorry a surge protector saves disconnecting batteries
Won’t stop the alternator diodes burning out though. You’ve been lucky.
I dont doubt it, one thing I was always told was to get the welder earth as close to the weld as you can, which I suppose goes along with clipping a jump lead to a starter motor.
I am sure we have saved a few alternators by leaving the engines running, or by stopping the engine and pulling the plug out of the back of the alternator
cieranc:
Yes that’s true, the closer the earth to the weld and the better the contact, the lower the risk of spiking.
But for the sake of slackening a 10mm nut and whipping the battery link-lead off, It’s just not worth the risk!
I know you are right, it was normally on bulk skeletals where the hydraulics were needed to be working. I have not had an electrode in my hand for over 20 years
In the past I have jump started a truck by disconnecting both batteries from the donor truck while the engine was left running, using them to start the stricken truck while the donor truck idled away on tick-over with no batteries connected to it, and then put them back on the donor truck. I’m sure you aren’t supposed to do it, but that’s the way it was.
I was once parked on the A19 between Sunderland and Middlesbrough with another truck from the same company. Next morning when we were about to set off the driver from a Lithuanian trucks opposite comes running over and says he has a flat battery and can we help, we said we would be we didnt have any jump leads…anyway, Lithuanian driver says no problem, we’ll use the ABS lead. I was sceptical and thought that might damage something but my mate didnt mind using his truck. After 5 or 10 minutes on high idle his truck started. Since that time its a method I’ve used on 5 or 6 occasions when my truck has had a flat battery, usually after standing in the yard for a long weekend and its worked a treat with no apparent damage to the ABS system or the trucks ECU.
robinhood_1984:
I was once parked on the A19 between Sunderland and Middlesbrough with another truck from the same company. Next morning when we were about to set off the driver from a Lithuanian trucks opposite comes running over and says he has a flat battery and can we help, we said we would be we didnt have any jump leads…anyway, Lithuanian driver says no problem, we’ll use the ABS lead. I was sceptical and thought that might damage something but my mate didnt mind using his truck. After 5 or 10 minutes on high idle his truck started. Since that time its a method I’ve used on 5 or 6 occasions when my truck has had a flat battery, usually after standing in the yard for a long weekend and its worked a treat with no apparent damage to the ABS system or the trucks ECU.
lol
