ahmett
Prominent member
Hi guys, how long should the battery last if the car is parked without it being disconnected?
Car is a 2010 Fiat 500 Dualogic.
Car is a 2010 Fiat 500 Dualogic.
Technical How Long Should Battery Last Parked?
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Technical How Long Should Battery Last Parked?
Lullaby
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Depends of the age of the accu and type. Most common types who are 4 to 5 years will be drained death after 6 to 8 weeks and need to be replaced, some type's can be recovered by a special charger. Best is to demount the accu and use a battery trickle charger to prevent damage. If you can't charge it up to 13-14 volts it is death.
PS: Thanks for the question, it reminds me to charge my own deep cycle.
PS: Thanks for the question, it reminds me to charge my own deep cycle.
I think you'll notice it will be flat after 2 weeks. If you disconnect it, it can stay charged for closer 8 weeks.
Ralf S.
Ralf S.
Agree. A good indicator comes to me from a local garage who is near our airport. He gets a number of call outs to cars which have been parked up while the owners are away on annual holiday, typically for a fortnight, and who's batteries are too far gone to start the vehicle on their return. Many of the storage people will not now jump start due to the risk of damage to electronics so he gets called out.
If the car is to be unused for more than about 10 days, and you know this right from the beginning, it's probably best for the battery if you stick a modern "smart" charger on it. You'll notice I've not suggested disconnecting any battery leads? Disconnecting the battery, so the car's systems completely power down, is a procedure to be approached with caution on modern vehicles - I'd say pretty much anything with stop/start? but some earlier vehicles also gave problems (Earlier Rovers - with MEMS I believe? - could not be sorted out without a visit to the dealer if you isolated the battery. I remember the boss telling us not to disconnect batteries on them without our electrical guy being present) You can pretty much take bets that when you connect the battery up again and turn on the ignition you're going to be faced with the dash lighting up like a Christmas tree with warning lights! In practice most of those will go out again after you've driven a few miles and the system ECUs have relearned values but some can be "stubborn" and need an expensive visit to the dealer to be put on a diagnostic machine for a reset. I have a CTEK smart charger which I regularly connect to my modern Ibiza and other family cars without disconnecting battery leads and have experienced absolutely no issues at all. I certainly would not connect my "good old" transformer type, "dumb", Crypton charger though without completely isolating the leads first, because it's output is not stable enough and would be likely to cause damage to the electronics.
I would expect at least a month more if it's a big battery there's been times I've not driven the old Mazda never been an issue after weeks
Old being the operative word..
Newer cars have immobilisers and all sorts of electrical fandango... the Younger Mrs S's 500 can go 2-3 weeks of no use before it doesn't start, whereas her previous Cinquecento (which only powered an LED clock) would last over a month.
Ralf S.
Newer cars have immobilisers and all sorts of electrical fandango... the Younger Mrs S's 500 can go 2-3 weeks of no use before it doesn't start, whereas her previous Cinquecento (which only powered an LED clock) would last over a month.
Ralf S.
ahmett
Prominent member
Ok because I am leaving the car for 3 weeks without driving it. Let's see. With my Mini, 3 weeks is never an issue, so I would hope the Fiat lasts about a month before it starts being an issue. It's an auto so I can't bump start it unfortunately.
I have roadside assistance should the worst happen but I'd rather avoid having to wait for them
I have roadside assistance should the worst happen but I'd rather avoid having to wait for them
Piccolo Nero e Bella
Prominent member
With the lockdowns in early 2020 my FIAT would quite happily start immediately after three weeks or so but I was concerned about doing it too often and invested in the CTEK charger. If nothing else it gave one peace of mind. A drawback is that it interfered with the telly in the adjoining room!
ahmett
Prominent member
ok that's reassuring. i travel so much these days, so can leave the car a while, it's a 2nd car anyway.
Piccolo Nero e Bella
Prominent member
I should add the caveat that mine is Stop/Start with the hefty EFB battery and it's in top condition.
While we're on this subject - batteries too flat to start the car - I've been very nervous, for years, about jump starting any vehicle with electronic systems so I have tended just not to do it, preferring to either charge up the car's existing battery or fit another know good battery.
However, over the last couple of years I've rather changed my mind. The "Family Fleet" is now becoming quite geriatric - 2007 Astra, 2008 Jazz, 2010 Panda and 2012 Punto (The ibiza and Rio are both younger and I haven't yet had to jump them). Although older all these cars have electronic control mechanisms so I've tended not to jump them but they've all experienced undercharged battery problems within the last couple of years. So I've been getting "brave" and started jumping them when needed. The Jazz in particular has had to be jumped several times due to grandchildren twice leaving the interior light on overnight and then, of late, the battery failing to hold charge after several days inaction. The Astra too must have been jumped three? times before we gave up and bought a new battery for it. The Punto was jumped about 3 times too but over a period of just a few days because it started playing up at the beginning of a long holiday weekend and it took several days for Kenny (Harrison Motors) to get a new one for us, so I was jumping it to keep my boy mobile - it would start when hot and maybe a couple of hours after stopping, but wouldn't start "cold" after an overnight. It just would go over comp slowly a few revs and then die. Our own Panda often sits for days without running and sometimes would just struggle into life, sometimes not. It really needs a new battery, and I'll have to definitely buy one before this winter starts, but in the meantime I've done a "recond" charge with the CTEK and it seems to be "living" now the weather is warmer (I also stick the CTEK on it a couple of times a week.)
In addition to the above, in the last year or so, I've jumped my pal's Jag "S" type, two of the four Jazz's which "live" in the street and the HRV Honda which lives at the end of the road. I've not had a single problem with any of them and these are all cars with who's owners I have almost daily contact so I'm sure I'd know about it if they'd had problems.
So, how am I "getting away" with this seemingly heinous crime? Well, for starters, I've done a lot of reading up on it and chatting to people I know in garages. The main thing which seems to be the villain is voltage spikes which exceed the designed max voltage an electronic component is designed to work with. So, I reasoned, if you never connect anything which can induce a higher than acceptable voltage then you're probably going to be "safe". The other thing you have to watch out for is whether there is a Battery Condition Monitor/sensor present. This is often a wee "gismo", typically mounted on the negative terminal clamp of the battery but can be mounted elsewhere on the earth lead. As a general rule, if it's got stop/start then it's probably got a BCM. If it has one of these then don't connect the neg jump lead clamp directly to the neg battery terminal, go for the point where the earth lead is connected to the vehicle body/chassis - that way the sensor stays included in circuit as intended and you're unlikely to "blow" anything. It's good practice not to connect the neg jump lead direct to the battery terminal anyway for reasons of safety (avoiding sparks near the battery). I believe a very few (probably Luxury brands) have these sensors on the pos terminal clamp too so be careful where you put that pos jump lead if it has one - I've not so far came across one on a pos terminal clamp though.
Now, how to avoid - or at least minimize - the possibility of those system wrecking voltage spikes (and their attendant high currents which is actually what burns stuff out). First off I would avoid jumping car to car if at all possible. I'll talk a little more about that in a minute. A jump pack or slave battery, intelligently used, is your best bet. The vehicle is fitted with a 12 volt battery and it's charging system will raise system voltage to around 14, maybe 15 volts during charging. I believe some modern overrun (smart charge) systems can peak out at 18 volts? So the electronic components which are receiving battery voltage (there are many systems, like some sensors, which receive regulated supply, typically 5 volts) are "hardened" to work with voltages, and their resultant currents, of that order of magnitude. So, the simple act of connecting up a 12 volt battery is very unlikely to blow anything. I have a nice big (77ah) battery which came out of my old Cordoba tdi and what I like to do is connect it up with the jump leads and then let it sit for a few minutes just to put a bit of surface charge on the car's discharged battery plates thus somewhat equalizing the difference before turning the ignition key. When/if the engine starts then DO NOT immediately disconnect the jump leads. With the jump battery connected the alternator regulator (ECU) will be "seeing" a goodly source (battery) voltage - at least 11 volts probably - so it will start to deliver a "normal" rate of charge to the battery leads. - Alternators deliver a very good rate of charge at tickover but you might want to just raise the revs to 1500/2000 rpm to maximize charging, no need to rev the "nuts" off it though - Leave the jump/slave battery connected for a few minutes while this initial charging gets done - I tend to go for about 5 minutes - The slave battery coupled with the alternator output will put a very good surface charge on the "flat" battery's plates. Now when you disconnect the slave battery the alternator ECU (regulator pack, or whatever you want to call it) will continue to "see" this charge state of the car's own battery and continue to deliver a "normal" rate of charge to the car's battery. This "surface charge" is caused by chemical reaction on the very surface of the plates and it will take time before it goes "deeper" into the plates which is why you'll need to either drive around for 20 minutes or so or put a charger on the battery (preferred anyway) when you get home so that the charge can "saturate" the plates. Fail to do this, ie. turn the engine off after just a few minutes running, and you'll find there's not yet enough charge in the battery to do a restart because the surface charge on the plates will rapidly disperse.
Using a jump pack, as far as the car's electronics is concerned, is very similar to me using that big battery, in that when the engine starts the alternator ecu/regulator "sees" the jump pack voltage so it doesn't do anything "stupid" as it delivers charge to it's flat battery. I would probably leave the jump connected for a few minutes after starting to allow surface charge to build up on the flat battery's plates thus minimizing voltage drop when the jump pack is disconnected.
One of the worst things you can do is connect up the batteries - remember neg lead last - (typically directly terminal to terminal because many people don't know about sparks being a problem or have any idea they probably have a BCM) and immediately go for a start. As soon as the engine fires up they then disconnect the jump leads, often while someone else keeps the engine reving "just in case it dies". This can be the point at which an electronic component somewhere shouts "uncle" (60's language) and shuffles off to a higher existence (dies). Why? You've got a very discharged battery in the car to which you've connected your slave source. Then you start the engine which spins up the alternator so it's potential to produce charge is entirely at the, instantaneous, "mercy" of the regulator (ECU controlling the alternator field). OK, because you've got the slave battery connected the starter turns, there's enough electricity for the ignition and fueling systems to work and the "beast" awakens! Great. So, within moments, you - or another helpful person, whips the jump leads off thus killing the voltage from the slave which the alternator ECU has been happily using as a reference. Because you didn't allow time for a surface charge to build up on the car's battery plates, the only point of reference the alternator's ECU now has is the very low voltage of the car's flat battery so one minute it's "seeing" the slave voltage (say 12 volts) and then, virtually instantaneously as the jump lead is disconnected, it "sees" whatever the car's flat battery is managing to retain (maybe 5 volts? who knows. The lower this voltage the greater the problem) So it immediately raises the field excitation to max which whacks the alternator output through the roof, helped no end by the revving of the engine, and, if you're unlucky, exceeds the max designed voltage limits for some of the other electronics (Spike) whereupon they will, virtually instantaneously, "clock out"!
Jumping vehicle to vehicle? I really just don't do it but if you must then disconnect the vehicle leads on the "good" battery so it's isolated from the car and use it just like a stand alone slave. Another safer way to do it is to connect up the jump leads between the two cars - paying attention to safety and BCM considerations - remove the ignition key from the car with the flat battery then start up the car with the "good" battery and let it run for maybe 10 minutes. This will put a "useable" charge onto the plates of the flat battery - unless the "flat" battery is a hopeless case. Now disconnect the jump leads and try starting the "flat" car. Unless the battery is totally "done" it'll probably start and because the slave car is not now part of the system there's really no risk of damage to either vehicle.
What I would absolutely not do on a modern vehicle, is connect up the jump leads car to car, run the "good" car's engine and start up the "poorly" car then disconnect the jump leads with both cars still running. In fact I wouldn't do anything which involved both cars having their ignition keys in the run position both at the same time. I'm not all that enthusiastic about just using the good car to put a charge into the poorly car - as I've mentioned above. I just don't like to have two car's electronics having access to each other!
However, over the last couple of years I've rather changed my mind. The "Family Fleet" is now becoming quite geriatric - 2007 Astra, 2008 Jazz, 2010 Panda and 2012 Punto (The ibiza and Rio are both younger and I haven't yet had to jump them). Although older all these cars have electronic control mechanisms so I've tended not to jump them but they've all experienced undercharged battery problems within the last couple of years. So I've been getting "brave" and started jumping them when needed. The Jazz in particular has had to be jumped several times due to grandchildren twice leaving the interior light on overnight and then, of late, the battery failing to hold charge after several days inaction. The Astra too must have been jumped three? times before we gave up and bought a new battery for it. The Punto was jumped about 3 times too but over a period of just a few days because it started playing up at the beginning of a long holiday weekend and it took several days for Kenny (Harrison Motors) to get a new one for us, so I was jumping it to keep my boy mobile - it would start when hot and maybe a couple of hours after stopping, but wouldn't start "cold" after an overnight. It just would go over comp slowly a few revs and then die. Our own Panda often sits for days without running and sometimes would just struggle into life, sometimes not. It really needs a new battery, and I'll have to definitely buy one before this winter starts, but in the meantime I've done a "recond" charge with the CTEK and it seems to be "living" now the weather is warmer (I also stick the CTEK on it a couple of times a week.)
In addition to the above, in the last year or so, I've jumped my pal's Jag "S" type, two of the four Jazz's which "live" in the street and the HRV Honda which lives at the end of the road. I've not had a single problem with any of them and these are all cars with who's owners I have almost daily contact so I'm sure I'd know about it if they'd had problems.
So, how am I "getting away" with this seemingly heinous crime? Well, for starters, I've done a lot of reading up on it and chatting to people I know in garages. The main thing which seems to be the villain is voltage spikes which exceed the designed max voltage an electronic component is designed to work with. So, I reasoned, if you never connect anything which can induce a higher than acceptable voltage then you're probably going to be "safe". The other thing you have to watch out for is whether there is a Battery Condition Monitor/sensor present. This is often a wee "gismo", typically mounted on the negative terminal clamp of the battery but can be mounted elsewhere on the earth lead. As a general rule, if it's got stop/start then it's probably got a BCM. If it has one of these then don't connect the neg jump lead clamp directly to the neg battery terminal, go for the point where the earth lead is connected to the vehicle body/chassis - that way the sensor stays included in circuit as intended and you're unlikely to "blow" anything. It's good practice not to connect the neg jump lead direct to the battery terminal anyway for reasons of safety (avoiding sparks near the battery). I believe a very few (probably Luxury brands) have these sensors on the pos terminal clamp too so be careful where you put that pos jump lead if it has one - I've not so far came across one on a pos terminal clamp though.
Now, how to avoid - or at least minimize - the possibility of those system wrecking voltage spikes (and their attendant high currents which is actually what burns stuff out). First off I would avoid jumping car to car if at all possible. I'll talk a little more about that in a minute. A jump pack or slave battery, intelligently used, is your best bet. The vehicle is fitted with a 12 volt battery and it's charging system will raise system voltage to around 14, maybe 15 volts during charging. I believe some modern overrun (smart charge) systems can peak out at 18 volts? So the electronic components which are receiving battery voltage (there are many systems, like some sensors, which receive regulated supply, typically 5 volts) are "hardened" to work with voltages, and their resultant currents, of that order of magnitude. So, the simple act of connecting up a 12 volt battery is very unlikely to blow anything. I have a nice big (77ah) battery which came out of my old Cordoba tdi and what I like to do is connect it up with the jump leads and then let it sit for a few minutes just to put a bit of surface charge on the car's discharged battery plates thus somewhat equalizing the difference before turning the ignition key. When/if the engine starts then DO NOT immediately disconnect the jump leads. With the jump battery connected the alternator regulator (ECU) will be "seeing" a goodly source (battery) voltage - at least 11 volts probably - so it will start to deliver a "normal" rate of charge to the battery leads. - Alternators deliver a very good rate of charge at tickover but you might want to just raise the revs to 1500/2000 rpm to maximize charging, no need to rev the "nuts" off it though - Leave the jump/slave battery connected for a few minutes while this initial charging gets done - I tend to go for about 5 minutes - The slave battery coupled with the alternator output will put a very good surface charge on the "flat" battery's plates. Now when you disconnect the slave battery the alternator ECU (regulator pack, or whatever you want to call it) will continue to "see" this charge state of the car's own battery and continue to deliver a "normal" rate of charge to the car's battery. This "surface charge" is caused by chemical reaction on the very surface of the plates and it will take time before it goes "deeper" into the plates which is why you'll need to either drive around for 20 minutes or so or put a charger on the battery (preferred anyway) when you get home so that the charge can "saturate" the plates. Fail to do this, ie. turn the engine off after just a few minutes running, and you'll find there's not yet enough charge in the battery to do a restart because the surface charge on the plates will rapidly disperse.
Using a jump pack, as far as the car's electronics is concerned, is very similar to me using that big battery, in that when the engine starts the alternator ecu/regulator "sees" the jump pack voltage so it doesn't do anything "stupid" as it delivers charge to it's flat battery. I would probably leave the jump connected for a few minutes after starting to allow surface charge to build up on the flat battery's plates thus minimizing voltage drop when the jump pack is disconnected.
One of the worst things you can do is connect up the batteries - remember neg lead last - (typically directly terminal to terminal because many people don't know about sparks being a problem or have any idea they probably have a BCM) and immediately go for a start. As soon as the engine fires up they then disconnect the jump leads, often while someone else keeps the engine reving "just in case it dies". This can be the point at which an electronic component somewhere shouts "uncle" (60's language) and shuffles off to a higher existence (dies). Why? You've got a very discharged battery in the car to which you've connected your slave source. Then you start the engine which spins up the alternator so it's potential to produce charge is entirely at the, instantaneous, "mercy" of the regulator (ECU controlling the alternator field). OK, because you've got the slave battery connected the starter turns, there's enough electricity for the ignition and fueling systems to work and the "beast" awakens! Great. So, within moments, you - or another helpful person, whips the jump leads off thus killing the voltage from the slave which the alternator ECU has been happily using as a reference. Because you didn't allow time for a surface charge to build up on the car's battery plates, the only point of reference the alternator's ECU now has is the very low voltage of the car's flat battery so one minute it's "seeing" the slave voltage (say 12 volts) and then, virtually instantaneously as the jump lead is disconnected, it "sees" whatever the car's flat battery is managing to retain (maybe 5 volts? who knows. The lower this voltage the greater the problem) So it immediately raises the field excitation to max which whacks the alternator output through the roof, helped no end by the revving of the engine, and, if you're unlucky, exceeds the max designed voltage limits for some of the other electronics (Spike) whereupon they will, virtually instantaneously, "clock out"!
Jumping vehicle to vehicle? I really just don't do it but if you must then disconnect the vehicle leads on the "good" battery so it's isolated from the car and use it just like a stand alone slave. Another safer way to do it is to connect up the jump leads between the two cars - paying attention to safety and BCM considerations - remove the ignition key from the car with the flat battery then start up the car with the "good" battery and let it run for maybe 10 minutes. This will put a "useable" charge onto the plates of the flat battery - unless the "flat" battery is a hopeless case. Now disconnect the jump leads and try starting the "flat" car. Unless the battery is totally "done" it'll probably start and because the slave car is not now part of the system there's really no risk of damage to either vehicle.
What I would absolutely not do on a modern vehicle, is connect up the jump leads car to car, run the "good" car's engine and start up the "poorly" car then disconnect the jump leads with both cars still running. In fact I wouldn't do anything which involved both cars having their ignition keys in the run position both at the same time. I'm not all that enthusiastic about just using the good car to put a charge into the poorly car - as I've mentioned above. I just don't like to have two car's electronics having access to each other!
As an aside to the above about jump/boost starting, perhaps you'll have picked up on that I think the situation which presents the greatest danger, in terms of inducing a potentially damaging current "spike", is where the "flat" battery is "very flat" as this presents the greatest danger of the charging alternator's regulator - on the vehicle with the "flat" battery - inducing a spike just as the slave battery is disconnected. So It's worth taking a voltage reading of the "flat" battery before making a decision as to whether to jump or not. Depending on the demands of the car, Some vehicles will have larger capacity batteries in relation to the demands of their current draw than others, it's likely that a battery which shows a standing voltage (ie when the vehicle's ignition is "off") of less than 10 to 11 volts will experience problems turning the engine over so the car won't start. A battery at this voltage won't require much to raise it's voltage to a level where it can crank the engine and if left connected to the jump battery for a while after a successful jump (maybe 5 to 10 minutes, longer is good) then "surface charge" on the "flat" battery's plates will come up to a voltage closely matching the jump/slave battery so when the jump/slave is disconnected the differential will be very small and the likelihood of a "spike" being induced much reduced.
I think it's always worth taking a reading of the voltage of the "flat" battery if you are considering a jump start and if the "flat" battery is showing a very low voltage you might like to consider whether it's worth taking the risk. I say this because there's always the chance that the "flat" battery may be behaving this way due to an internal fault which might mean it can't accept a meaningful charge. Therefore, if a start is achieved, perhaps using a nice big slave like mine, then when the slave is disconnected, the "flat" battery will not have accepted any charge and so the possibility of a spike is much more likely.
Following on from this it's interesting to consider the relative safety afforded by trying to jump start with one of these, relatively new, "Micro" jump start devices. I'm talking about the type which contains a relatively small Lithium Ion battery and is commonly kept in the glove box or boot. There are also ones which use super capacitors which particularly interest me. These, quite low capacity, devices work because the typical "flat" battery is actually not "flat" at all but is holding a voltage just below that required to allow cranking. These small battery powered devices will "assist" the car's own battery and raise the available capacity to the point where a brief period of cranking can be achieved until the small battery in the device is exhausted. If the car's own battery is significantly reduced then one of these small external batteries will not be able to raise capacity to the point where cranking is possible so it's only likely to achieve a start if the battery is not in a condition of deep discharge, or has an internal fault, which means the likelihood of a spike being initiated on disconnect is very greatly reduced.
I think it worth saying here that although my main concern about jump staring is the potential for a voltage (and consequential amperage) spike to be produced - most likely at disconnect of the slave source - jumping a modern vehicle with electronics is never a risk free thing to do as there can be other factors which increase the risk - not least of which includes the fact that a battery under "duress" (such as having recently delivered high current) will be very likely to be emitting flammable/explosive gasses so may ignite/explode if a spark is produced when connecting/disconnecting jump leads. Much safer to disconnect the vehicle terminals and charge the flat battery in isolation. Not much help if you're stuck in the supermarket car park of course but life is full of choices and they're often hard ones to make? Always worth bearing in mind though that connecting one car to another with a set of nice big thick jump leads has to always be maximum risk? By the way, you can buy jump lead sets which incorporate a surge protection: https://www.tooled-up.com/draper-surge-protected-booster-cable-jump-leads/prod/499344/ which is probably a wise purchase if you don't already own a set of leads and are considering buying some. There are stand alone surge protectors too: https://www.sealey.co.uk/category/5637228587/surge-protection which can be used with existing lead sets or to protect electronics when electric welding (MMA, MIG/MAG or TIG) I've long been meaning to buy one of these but, as I've so far never had something electronic fail on a vehicle I've welded with my MIG, it's faded to become a "desirable" rather than "imperative" purchase.
Well, you'll probably be glad to know, I think I've run out of thinks to say on this subject - or at least until someone makes a comment which sets me off again! I'd love to hear other people's opinions on the subject and, taking into account that I'm a pretty ignorant grease monkey, I'm sure there's a lot more to be said on the subject - and probably something I've misunderstood?
I think it's always worth taking a reading of the voltage of the "flat" battery if you are considering a jump start and if the "flat" battery is showing a very low voltage you might like to consider whether it's worth taking the risk. I say this because there's always the chance that the "flat" battery may be behaving this way due to an internal fault which might mean it can't accept a meaningful charge. Therefore, if a start is achieved, perhaps using a nice big slave like mine, then when the slave is disconnected, the "flat" battery will not have accepted any charge and so the possibility of a spike is much more likely.
Following on from this it's interesting to consider the relative safety afforded by trying to jump start with one of these, relatively new, "Micro" jump start devices. I'm talking about the type which contains a relatively small Lithium Ion battery and is commonly kept in the glove box or boot. There are also ones which use super capacitors which particularly interest me. These, quite low capacity, devices work because the typical "flat" battery is actually not "flat" at all but is holding a voltage just below that required to allow cranking. These small battery powered devices will "assist" the car's own battery and raise the available capacity to the point where a brief period of cranking can be achieved until the small battery in the device is exhausted. If the car's own battery is significantly reduced then one of these small external batteries will not be able to raise capacity to the point where cranking is possible so it's only likely to achieve a start if the battery is not in a condition of deep discharge, or has an internal fault, which means the likelihood of a spike being initiated on disconnect is very greatly reduced.
I think it worth saying here that although my main concern about jump staring is the potential for a voltage (and consequential amperage) spike to be produced - most likely at disconnect of the slave source - jumping a modern vehicle with electronics is never a risk free thing to do as there can be other factors which increase the risk - not least of which includes the fact that a battery under "duress" (such as having recently delivered high current) will be very likely to be emitting flammable/explosive gasses so may ignite/explode if a spark is produced when connecting/disconnecting jump leads. Much safer to disconnect the vehicle terminals and charge the flat battery in isolation. Not much help if you're stuck in the supermarket car park of course but life is full of choices and they're often hard ones to make? Always worth bearing in mind though that connecting one car to another with a set of nice big thick jump leads has to always be maximum risk? By the way, you can buy jump lead sets which incorporate a surge protection: https://www.tooled-up.com/draper-surge-protected-booster-cable-jump-leads/prod/499344/ which is probably a wise purchase if you don't already own a set of leads and are considering buying some. There are stand alone surge protectors too: https://www.sealey.co.uk/category/5637228587/surge-protection which can be used with existing lead sets or to protect electronics when electric welding (MMA, MIG/MAG or TIG) I've long been meaning to buy one of these but, as I've so far never had something electronic fail on a vehicle I've welded with my MIG, it's faded to become a "desirable" rather than "imperative" purchase.
Well, you'll probably be glad to know, I think I've run out of thinks to say on this subject - or at least until someone makes a comment which sets me off again! I'd love to hear other people's opinions on the subject and, taking into account that I'm a pretty ignorant grease monkey, I'm sure there's a lot more to be said on the subject - and probably something I've misunderstood?
To prevent a spike I always turn on as much users I can (heated rear window, blower, headlights etc) before disconnecting the jumpercables.
gr J
gr J
Piccolo Nero e Bella
Prominent member
Nor I. This is my first 'electronic' car and I'm not game to take any chances risking it as a donor or a recipient. I carry a lithium battery jump starter, which has been used once to start someone else's car, and I have roadside assistance if anything happens to mine. A trip on the back of a lorry is a lot cheaper than replacing computers...
Yes, many "get away with it", mostly because I think the majority of "flat" batteries are not actually flat at all but just a wee bit under the required voltage once put under load. Once connected to a good battery and the engine started there is very little differential so when the disconnect is made there's no "trigger" to induce the spike. Trouble is the potential is always there and I'm just not prepared to take the risk with a stranger's car, especially if it's not all that old. I will do it with family and friends having first had a "conversation" with them and done a few checks - like an initial voltage check etc. Must say I still felt a little apprehensive doing it to my pal's Jag S type though!
When I'm using my tyre pump, when the ac fans cut out there's a noticeable speed rise(on the pump) for a second or so until the alternator reacts to the lower load, I'd expect the flat battery to sink most spikes before an issue, a greater risk to the cars delicate electronics is relays that don't have a reverse diode I'm willing to bet most have not? If you've ever had your fingers over the coil terminals when the power is removed you'll soon drop the relay with the shock!
ahmett
Prominent member
Hey guys just started the car after 3 weeks of no use no issues whatsoever started immediately as if i just drove it an hour ago.
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- Points
- 138
We have a few too many cars modern and classics and batteries were always a regular failure......just not possible to have a charger or a conditioner on every vehicle so we have these little voltage display LED's I have pictured and are connected anywhere to a live and eath on the car in view or direct across the battery. Some cars like the Rolls Royce which seems to have gone through the most batteries over the years we have wired in permanently. You just need to glance over once a week and when we see the voltage drop usually below about 12.5v we will put the battery on a trickle for a few days until it comes back up......Thankfully have not had to buy any new battery now for a couple of years.
I have seen some later types that fit also into a cigarette lighter which is usually fine on old classics but modern cars now often the cigarette lighter powers down after a couple of minutes.
The problem with vehicles is they all have aquiescent/parasitic drain even with ignition switched off which is why disconnecting a battery on older cars is often advised and this can vary quite a lot vehicle to vehicle or age and condition including weather conditions if very damp.
I certainly would not disconnect the batteries on any of our modern cars even if not being used for a few weeks so much prefer just to glance in the windows and look at what the voltage is being displayed....one day maybe the manufacturers will add them.....last time we replaced the 500 battery we ended up with a flashing ODO
I have seen some later types that fit also into a cigarette lighter which is usually fine on old classics but modern cars now often the cigarette lighter powers down after a couple of minutes.
The problem with vehicles is they all have aquiescent/parasitic drain even with ignition switched off which is why disconnecting a battery on older cars is often advised and this can vary quite a lot vehicle to vehicle or age and condition including weather conditions if very damp.
I certainly would not disconnect the batteries on any of our modern cars even if not being used for a few weeks so much prefer just to glance in the windows and look at what the voltage is being displayed....one day maybe the manufacturers will add them.....last time we replaced the 500 battery we ended up with a flashing ODO
