Jump starting

Baxlin · Nov 27th, 2017, 09:37

My daughter flattened the battery trying to start her car yesterday, and phoned me to ask me to jump start it. As I've had a few lecky type problems with the Volvo recently, I didn't want to risk it, so I took my rapid charger and after about 20 minutes there was enough in it to start the car.

This made me think though, with all the many wires and cables attached to car battery terminals nowadays, is jump starting a good idea on modern cars? (Couldn't even get to the -ve terminal on her Peugeot, I had to use a nearby earth point)

DaveNP · Nov 27th, 2017, 10:02

I give no guarantees and it's only what I do-

With all of the extra electrickery in modern vehicles if I'm jump starting something, I have the side lights on on both vehicles before I hook them up, supposedly this acts to prevent the sudden change in voltage messing up the computer etc.
Some cars are more temperamental than others and if you've got the drivers handbook have a good read first.

Using an earth point away from the battery is recommended by some.

Clan · Nov 27th, 2017, 10:41

Quote:

Originally Posted by Baxlin

My daughter flattened the battery trying to start her car yesterday, and phoned me to ask me to jump start it. As I've had a few lecky type problems with the Volvo recently, I didn't want to risk it, so I took my rapid charger and after about 20 minutes there was enough in it to start the car.

This made me think though, with all the many wires and cables attached to car battery terminals nowadays, is jump starting a good idea on modern cars? (Couldn't even get to the -ve terminal on her Peugeot, I had to use a nearby earth point)

No harm at all in jump starting .. battery to battery the car is only 12 volts it cant do any harm .. a tip would be to leave the supplying cars engine running for 10 minutes to get some charge into the other cars battery before starting it .

GreenBrick · Nov 27th, 2017, 12:21

Contrary to what a lot of people do, you should stop the engine of the "donor" vehicle before cranking over the dead car, otherwise you are putting a big strain on the donor's alternator, as the starter is like an almost short circuit. So use the donor to charge the dead battery for a bit first, then use the good battery in parallel with the dead one.

The order the jump leads are connected is purely to stop sparks igniting gases from the battery. Hook up the +ve leads first, then the -ve to a ground a way from the battery, so the spark won't cause an explosion. Same but in reverse, especially as the battery may have vented some gas while being charged.

As for soaking up a sudden change in voltage, the dead battery will work like a big capacitor, so I cannot see that being a big problem, but I guess someone must have had a problem, otherwise people wouldn't mention it so often.

NigelDay · Nov 27th, 2017, 12:37

That's interesting about the strain on the alternator. It's a practice I have always followed to switch off the donor engine at the point of starting the dead engine, but the advice in the manuals and on-line is the reverse !

green van man · Nov 27th, 2017, 15:47

A mate calculated that to stall a 130A altinator on a landrover would take an electrical load of 900A. The altinator will only give it's rated output and the battery acts as a shunt anyway. The battery supplies the load the altinator charges the battery, if the battery is putting out faster than the altinator is putting in the battery will go flat. This is why you run the engine even if not driving the car when whinching.
I used to connect jump leads battery to battery but with the increasing popularity of canbus systems now use the red terminal found around the engine for the positive and a good ground on the bodywork or engine block for the negative. For older cars with no red conection point and exposed battery terminals I still go battery to battery.

Paul.

Welton · Nov 27th, 2017, 16:08

My mechanic showed me a bin full of dashboard binnacles where modern cars had sent up to 18 volts to the 'dead' vehicle and ruined its electrics.

Ford 'smart' alternators are capable of 18 volts in cold conditions, I'd be very wary if you didn't know exactly how each car functions.

Willow place · Nov 27th, 2017, 16:33

The best jump starter I have found is the DB Power 18,000 mAh 600 amps cranking , it will fit in a large glove compartment or of course in the boot,it is about 20cm long and about 12 cm high (These measurements are the case ) It started a friends car that had not been used for 2 months Instantly !! the product is on Amazon,good reviews and 3 years warranty.

GreenBrick · Nov 28th, 2017, 12:30

I have a booster pack with a lead acid battery in for starting, so stopped using jump leads a long time ago. Got it from Halfords and it has started long dead diesels. I replaced the battery in it after about 10 years, and it is as good as new.

green van man · Nov 28th, 2017, 17:05

I also have a booster pack, unfortunately I use it so seldom that it's always flat by the time I need it and if I wait 3 hours for it to charge I may as well run the extension lead to the car and charge that battery.

Paul.

Nov 27th, 2017, 09:37	#1
Baxlin Old Rocker Last Online: Apr 30th, 2024 22:30 Join Date: Dec 2016 Location: Tring	Jump starting My daughter flattened the battery trying to start her car yesterday, and phoned me to ask me to jump start it. As I've had a few lecky type problems with the Volvo recently, I didn't want to risk it, so I took my rapid charger and after about 20 minutes there was enough in it to start the car. This made me think though, with all the many wires and cables attached to car battery terminals nowadays, is jump starting a good idea on modern cars? (Couldn't even get to the -ve terminal on her Peugeot, I had to use a nearby earth point) __________________ Just my opinion, please don't shoot me if it doesn't match yours! 2011 C70 D3 (now sold)and JZR 3 wheeler

Nov 27th, 2017, 10:02	#2
DaveNP Non VOC Member Last Online: Yesterday 20:49 Join Date: Jun 2011 Location: Milton Keynes	I give no guarantees and it's only what I do- With all of the extra electrickery in modern vehicles if I'm jump starting something, I have the side lights on on both vehicles before I hook them up, supposedly this acts to prevent the sudden change in voltage messing up the computer etc. Some cars are more temperamental than others and if you've got the drivers handbook have a good read first. Using an earth point away from the battery is recommended by some. __________________ David V70 2.5 10v Torslanda Manual 98 Sreg

Nov 27th, 2017, 12:21	#4
GreenBrick SilverBrick Lives! Last Online: Apr 27th, 2024 22:18 Join Date: Apr 2015 Location: Poynton, Cheshire	Contrary to what a lot of people do, you should stop the engine of the "donor" vehicle before cranking over the dead car, otherwise you are putting a big strain on the donor's alternator, as the starter is like an almost short circuit. So use the donor to charge the dead battery for a bit first, then use the good battery in parallel with the dead one. The order the jump leads are connected is purely to stop sparks igniting gases from the battery. Hook up the +ve leads first, then the -ve to a ground a way from the battery, so the spark won't cause an explosion. Same but in reverse, especially as the battery may have vented some gas while being charged. As for soaking up a sudden change in voltage, the dead battery will work like a big capacitor, so I cannot see that being a big problem, but I guess someone must have had a problem, otherwise people wouldn't mention it so often. __________________ Jeep ZJ, 960, Past:- Mazda2, Jumbuck, V70 (2002), 945 (1995), Hyundai Coupe, Golf Mk4, Previa, Carina, 2 x Corsa, 4 x Astra, 944 16v (1991), Espace, Escort, Audi 80, Renault 21 Savanna, Polo, Mini Clubman/Pickup, Standard 8, Capri, Maxi.

Nov 27th, 2017, 12:37	#5
NigelDay Premier Member Last Online: Feb 29th, 2024 15:46 Join Date: Jul 2009 Location: Barnard Castle	That's interesting about the strain on the alternator. It's a practice I have always followed to switch off the donor engine at the point of starting the dead engine, but the advice in the manuals and on-line is the reverse ! __________________ 2015: XC60 D4 FWD SE Lux Nav 190hp manual, Osmium Grey, 17" Segin, Tempa, Winter Illumination, Security, Family, DSP, 4C, HK Sound, Subwoofer, Front Parking, Rear Camera, Dark Tinted, Power Passenger Seat, Speed and Heated Steering.

Nov 27th, 2017, 16:08	#7
Welton Premier Member Last Online: Sep 14th, 2021 17:03 Join Date: Feb 2009 Location: Market Harborough	My mechanic showed me a bin full of dashboard binnacles where modern cars had sent up to 18 volts to the 'dead' vehicle and ruined its electrics. Ford 'smart' alternators are capable of 18 volts in cold conditions, I'd be very wary if you didn't know exactly how each car functions. __________________ 2005 S40 T5 SE - Manual. Bilstein B4's. (For Sale) 2010 Citroen C4 1.6 HDi (bizarre Gearbox model). 2010 Renault Twingo (refreshingly simple) 2018 Infiniti Q30 1.6T Business Executive (what's this button do?)

Nov 27th, 2017, 15:47	#6
green van man Premier Member Last Online: Apr 11th, 2024 09:21 Join Date: Nov 2012 Location: Ffos y Ffin	A mate calculated that to stall a 130A altinator on a landrover would take an electrical load of 900A. The altinator will only give it's rated output and the battery acts as a shunt anyway. The battery supplies the load the altinator charges the battery, if the battery is putting out faster than the altinator is putting in the battery will go flat. This is why you run the engine even if not driving the car when whinching. I used to connect jump leads battery to battery but with the increasing popularity of canbus systems now use the red terminal found around the engine for the positive and a good ground on the bodywork or engine block for the negative. For older cars with no red conection point and exposed battery terminals I still go battery to battery. Paul.

Nov 27th, 2017, 16:33	#8
Willow place Senior Member Last Online: Jan 1st, 2023 17:41 Join Date: May 2017 Location: Los Finos Almeria	The best jump starter I have found is the DB Power 18,000 mAh 600 amps cranking , it will fit in a large glove compartment or of course in the boot,it is about 20cm long and about 12 cm high (These measurements are the case ) It started a friends car that had not been used for 2 months Instantly !! the product is on Amazon,good reviews and 3 years warranty.

Nov 28th, 2017, 12:30	#9
GreenBrick SilverBrick Lives! Last Online: Apr 27th, 2024 22:18 Join Date: Apr 2015 Location: Poynton, Cheshire	I have a booster pack with a lead acid battery in for starting, so stopped using jump leads a long time ago. Got it from Halfords and it has started long dead diesels. I replaced the battery in it after about 10 years, and it is as good as new. __________________ Jeep ZJ, 960, Past:- Mazda2, Jumbuck, V70 (2002), 945 (1995), Hyundai Coupe, Golf Mk4, Previa, Carina, 2 x Corsa, 4 x Astra, 944 16v (1991), Espace, Escort, Audi 80, Renault 21 Savanna, Polo, Mini Clubman/Pickup, Standard 8, Capri, Maxi.

Nov 28th, 2017, 17:05	#10
green van man Premier Member Last Online: Apr 11th, 2024 09:21 Join Date: Nov 2012 Location: Ffos y Ffin	I also have a booster pack, unfortunately I use it so seldom that it's always flat by the time I need it and if I wait 3 hours for it to charge I may as well run the extension lead to the car and charge that battery. Paul.

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