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Jump Starting Cars -To And From Focus . Heads Up To Newbies.


Jon Bhoy
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Hi folks,

Ok found a post from 3 years back that when i saw it i was both shocked and amazed at and really had no idea . I am no expert on car electrics and have jumped many engines over the years but just found that it is very dangerous to jump start to and from a Focus due to some 18v issue. Not being a drama queen but did mention it can mess up the ECU on some cars . I am not going to try to even explain the issues as i read the thread and did not fully understand the reasoning behind it.

I consider myself lucky as my sisters Insignia needed jumping tonight and i went over and jumped it fine but seems i must have got lucky . Hopefully there is someone here that can explain it in laymans terms.

Most folk here are VERY knowledgeable and i am sure are aware of the issue but i really had no idea and if i had no idea and had done it for years i am sure others are just like me and with us being in Winter and a possible cold snap next week i would rather make myself look a wally and stop one person messing up than keeping quiet and letting someone get in trouble.

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Jumped my mates nissan almera the other day from my focus. Just made sure the neg leads were connected to the correct place and everything worked fine on both mine and his...must have been lucky by looks of it.

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It just depends if the smart charge detects that the voltage is too low either on the focus or the other car it can if it feels the need to put out 18v since the focus is designed to take it it will be fine but the other car isn't and as said can blow the ecu it is not common for it to happen but it does happen often enough

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A booster pack is a very good idea.

I actually threw some jump leads away a while back.

Thats top of my list for the end of the month Clive . I think £50 should get a decent one. Which one do you have and would you recommend it?

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Jumped my mates nissan almera the other day from my focus. Just made sure the neg leads were connected to the correct place and everything worked fine on both mine and his...must have been lucky by looks of it.

Thats what i thought too John after i read it late last night . Seems like the chances are you will be OK but theres a high enough chance to avoid it and just use a booster instead.

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It just depends if the smart charge detects that the voltage is too low either on the focus or the other car it can if it feels the need to put out 18v since the focus is designed to take it it will be fine but the other car isn't and as said can blow the ecu it is not common for it to happen but it does happen often enough

I think maybe it is just me but i dont understand what this smart charge is or how it works ? Tried to work it out from the thread i posted but must be thick as you know what !!! I really did not want to scare monger but it did make me go bloomin 'eck or words to that effect!

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Also is it just me or is the MK2.5 (and maybe others) the only car that has the battery in a bloomin stupid place with almost half under the scuttle panel . Had a nightmare trying to gte the larger clamp on the jump leads onto the negative terminal but guess i can put it on somewhere else on the engline next time.

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Cheers Clive,thats one of the ones i ws looking at . How long do they hold their charge ? Would you say top up the charge once a month?

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Its quite simple really basically a battery charges best when the electrolyte is cold smart charge simply regulates the output of the alternator to ensure efficient charging to do this it is controlled via the pcm which monitors engine temp battery temp voltage in battery and electrical demand and varies accordingly as the battery charges and the electrolyte gets hot the pcm tells the alternator to reduce the voltage output on the flip side if it detects a very weak voltage it can generate up to 18v to give the battery a boost depending on the vehicle and wether it uses a similar system (most modern cars do ) this increase over a standard 12v system can blow the cars electronic modules

This I why silver calcium or double calcium batteries must be used a lead acid will simply boil and will give incorrect readings to the pcm the difference between the batteries is construction Silver Calcium alloy batteries have grids made from lead-calcium-silver alloy, instead of the traditional lead-antimony alloy or newer lead-calcium alloy the smart charge can detect the metals in the alloy which help give the correct readings .they generally have higher resistance to corrosion and the destructive effects of high temperatures. The result of this improvement imeans increased battery life and maintaining a starting power over time it also helps reduce emissions

Silver calcium batteries generally require more charging voltage (14.4 to 14.8 V) and may not be functional in older vehicles because their power generating systems (alternators) give lower voltages than those of modern vehicles. This also may occur with static chargers, some of which fail to charge these batteries.which is why ill never understand why some places still sell lead acid non calcium batteries for most new cars inc fords

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