Hi folks I’m thinking of investing in a jump starter to have on stand by as having read reports of not using the focus to start other cars for fear of 18 volts shooting back from the flat battery vehicle.

anyone spotted a good offer for one? 
cheers 

2 hours ago, MrRedman said:

fear of 18 volts shooting back from the flat battery vehicle.

Where would the 18 Volts shoot back from ? Firstly the flat battery will be way less than 12V hence the need to jump start and secondly if 18V appeared on the vehicle that was being jump-started then it would need an awful lot of new equipment. All alternators have over voltage protection normally set at 14.6V to ensure the safety of the vehicle and protect against fire.

 

 

I have a noco gb20. I've used it a couple of times. It seems good. 

9 hours ago, unofix said:

Where would the 18 Volts shoot back from ? Firstly the flat battery will be way less than 12V hence the need to jump start and secondly if 18V appeared on the vehicle that was being jump-started then it would need an awful lot of new equipment. All alternators have over voltage protection normally set at 14.6V to ensure the safety of the vehicle and protect against fire.

 

 

Smart Alternators push upto 18volts into a flat battery and then can push it back into the donor vehicle damaging the ecu apparently 

2 hours ago, MrRedman said:

Smart Alternators push upto 18volts into a flat battery

Speaking as an Electrial engineer with 40 plus years experiance the first thing you learn is that you can't push current. As far as smart alternators being capable of suppling 18 Volts that would make them pretty dumb. All modules on the vehicle have a maximum peak voltage of 14.9 Volts, most can only stand a voltage that high for less than a minute. Most are rated at a maximum continuous voltage of 13.8V. As I said ealier modern alternators have an over voltage protection that will clamp the output to a maximum of 14.6V

 

2 minutes ago, unofix said:

Speaking as an Electrial engineer with 40 plus years experiance the first thing you learn is that you can't push current. As far as smart alternators being capable of suppling 18 Volts that would make them pretty dumb. All modules on the vehicle have a maximum peak voltage of 14.9 Volts, most can only stand a voltage that high for less than a minute. Most are rated at a maximum continuous voltage of 13.8V. As I said ealier modern alternators have an over voltage protection that will clamp the output to a maximum of 14.6V

 

So there’s no truth in damaged ecu s? I was led to believe jump starting was a bad idea these days ,fair enough 

The SmartCharge alternator can push up to 18v briefly when it senses a cold battery with low charge.  It's not uncommon to blow headlight bulbs or spike LCD screens when jumping with these.

32 minutes ago, MrRedman said:

So there’s no truth in damaged ecu s? I was led to believe jump starting was a bad idea these days ,fair enough 

There is very much truth in damaged ECU's and other modules and I do tend to think that jump starting a vehicle with an extremly flat battery is unwise.

If in an emergency situation the only option is to jump start, then with the engine off connect the two batteries together and leave for 5 minutes, this will give the flat battery chance to partly recover. Then start the good vehicle first before trying to start the vehicle with the flat battery.

The electronic modules of a modern car can be damaged by transient spikes lasting only a few milli-seconds. The idea of a jump-start pack is not a bad one and a lot safer than using jump leads in the freezing cold pouring rain on a dark winter night.

I was told by the Brither in law who runs his own garage to NEVER jump start the car ( mk4 Focus) as it may cause damage to the electronics.

Right or wrong  I dunno I just drive the car 🤔

I got one of the small portable charger battery packs from Costco that saved me a few times on my old focus mk3 when the cold weather affected my battery. It's the size of a larger phone power bank but has connectors for your car battery that gives it enough juice to start most cars.

The car would go into sleep mode during the day at work and I had to open the car manually with the key but after connecting the power bank started first time every time.

This is the current model they are selling https://www.costco.co.uk/Tyres-Automotive/Car-Maintenance/Chargers-Jump-Starters/Energizer-9000mAh-Lithium-ion-Polymer-Car-Jump-Starter-Model-50806A/p/269663

Cheaper ones can be found on Amazon though.