A "different" way to jump start!

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This is going to be about my Super Capacitor Jump Starter - what's that? I'll try to inform you.

As I've been interested in these for several years now, I may have mentioned them before. However, now I've bought one I'm much better informed and some of you might be interested in my experience?

Jump starting is a subject which puts the "willies" up me, why? Well, modern vehicles are awash with Electronics and electronic components are notoriously well known for being fragile when not fed the required electric current, especially if an over voltage is the problem. Many of us will be aware that jumping car to car with conventional jump leads is a bit like playing Russian Roulette with your electronics - on both vehicles. I won't go into why as it's a long subject, suffice to say, I just don't jump car to car any more. However I do very happily jump start using a slave battery. At this time I have two "workshop" batteries. One is a big old 12 volt which was in my Cordoba 1.9 tdi somewhere in the high 70 ah region and too heavy to carry very far. There's also a smaller one from my boy's Punto which is around 50 ah and easier to transport but still not something I want to carry long distances. Both are very handy as power sources when I'm messing around in my workshop. The problem with using either of them is that they live in my garage not in my car! Not very convenient.

The answer of course, is a dedicated jump pack. There are so many advertised on line I just didn't know where to start As I started to sift through them it became immediately obvious that there are many with really quite small batteries and these seem to come in either quite conventional lead acid "flavour" or more modern Li ion types the latter being usually smaller and lighter - just a bit bigger than a large mobile phone, sort of thing you can keep in the glove box. But how, I was thinking, can something this small actually start a car with a flat battery? Well, the simple answer is it probably won't. These small jump packs work because very few "flat" batteries are actually "flat. They have just dropped in voltage to the point where there is just not quite enough "oomph" to energise the starter motor - You know the situation, you twist the key and there's a quite loud clicking noise from under the bonnet - this is the solenoid attempting to engage but not quite managing it as there's not enough voltage in the battery - often around 9 to 10 volts, it varies from car to car depending on the systems. What a jump pack does is "piggy back" it's voltage onto what's left in the big battery in the car and the two combined will lift the voltage enough to allow limited cranking of the engine. The smaller the jump pack the shorter cranking time it will allow. So that immediately ruled out the smaller packs in my view.

Then I was discussing this with some motor trade friends, one of whom raised a very interesting point. You've got to remember to keep charging it from time to time. He said he goes out to cars which won't start and finds a "dead" jump starter in the boot or glovebox! also, if you don't regularly charge them and let them go completely flat they often won't accept charge. Of course my big workshop batteries sit on maintenance charge on my Smart charger so this isn't a problem with them but it would be very easy to forget to put a jump start pack on charge every few months or whatever.

I'm going to break here as this thread is now getting to long. thread resuming in a minute

 

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A "Different" way to jump start - Part 2

I'm back!

It was at around this juncture that I started looking into Capacitor based Jump Starters because they are stored UNCHARGED and then, when needed, CHARGED UP FROM THE PARTIALLY FLAT VEHICLE BATTERY LITTERALY IN A FEW MINUTES! Wow! so what's that all about? Ok, as I understand it, these devices contain a bank of 5 or 6 substantial size Ultra capacitors each of which, when fully charged, reaches around 2.5 volts. The jump packs typically contain 5 of these although the more expensive ones have 6. To use it you simply connect the leads - red to battery positive on the "flat" vehicle battery and black to an earth on the vehicle (you can go to the battery negative terminal but I prefer no to to avoid the possibility of sparks near a battery which has likely been very recently under extreme duress trying to crank the engine. To be fair, most packs won't allow this as they remain isolated until you activate them, but I prefer to be careful. Once both leads are attached you initiate charging and the pack charges up which typically takes about 4 to 5 minutes. The you press the "start" button and you get a count down of "beeps" followed by an extended "beep". When the extended beep sounds the pack is supplying voltage to the car battery so you twist the ignition key and the starter will crank the engine.

So what on earth is going on? how can a battery with only 10, 9 or even 8 or 7 volts achieve a charge in the pack sufficient to start the vehicle? Ok. First thing to say is that most of these Ultra/super capacitor type jump packs won't charge if the vehicle battery is so discharged it falls below 5 volts. That's ok though because most vehicles which fail to start will still have enough voltage in their batteries to allow a charge to take place - if not you can charge the pack from another vehicle, at no risk to that vehicle, or using a USB charger from the mains. This doesn't differentiate them from small battery jump starters as they don't generally have enough capacity to start a vehicle with a completely flat battery either - they're just not big enough. So now we get to the "nitty gritty". You'll remember I said above that a fully charged capacitor holds about 2.5 volts? Well, we've got a "flat" battery in the car with likely about 8, 9 or maybe 10 volts in it. This is not enough to crank the engine. So, after connecting up the jump pack leads - red to pos, black to neg - and pressing the "charge" button the "clever" circuitry in the jump pack connects the capacitors in PARALLEL - so it's the same as connecting each 2.5 volt capacitor separately to the 9 volt - or whatever - battery power source. of course the pack's electronics monitor the charge and when all of the capacitors are charged it cuts the connection so over charging doesn't happen. Now you've got 5 or 6 - depending on the device you've bought - capacitors all fully charged to around 2.5 volts. Next you press the "start" button and the electronics now connect the capacitors in SERIES giving you the sum of those capacitors - so, if 5 it'll be around 12.5, maybe 13 volts (in theory a capacitor could take 2.7 volts) or, with 6 capacitors, around 15 volts. I think the electronics monitor this so a dangerous current is not fed into the system with the 6 capacitor packs like mine? I imagine this is not a problem with the 5 capacitor packs? When you press the start button the unit beeps for long enough to let you get behind the wheel ready for the steady beep which tells you it's time to give it a try.

I've only had it for a couple of months and I've "piddle diddled" around in the workshop experimenting with it and it seemed to work fine. However I used it "in anger" just the other day. I was sitting in my living room looking out the window when a car appeared traveling backwards up the road with a young lady at the wheel and a very hot looking young chap pushing on the bonnet. He saw me and gave me a wry smile. I just had to go out and say I'd love to help but can't because of my artifical knees and hip. He was fine with that so I aske him if they were trying a push start - our street is slightly down hill and he was pushing the car up hill. Yes he said, Don't suppose you've got jump leads have you? Well yes, I said and went on to tell him how dangerous jumping modern cars can be, he still wanted to try but I said "not with my car you won't. Then I mentioned the jump pack and he was all for it - although he didn't know what a jump pack was (I don't think he really knew how to do a jump start either). I tried the starter but all that happened was the solenoid clicked Then I checked the battery with my voltmeter which showed under 10 volts (forgotten what it actually was now.) Out came the jump pack and his wife - I think she was his wife? - was even more interested than him so I gave a very brief explanation as to how it worked because you have to wait a few minutes for it to charge up so there's time. Took about 4 minutes to reach full charge. Pushed the button (you can hear a relay inside the pack click as you do so) the countdown beeps ran down and then the longer beep. He was already behind the wheel so I told him to twist the key and the engine cranked nice and fast and sprang into life. Result. - Very impressive.

The one I bought is the Streetwise branded one:https://www.streetwizeaccessories.c...tarters/N-Capacitor-Jump-Starter-Green-SWPP20 Which I found at Argos for much less than the advertised price. I wanted a heavy duty unit and this one can cope with up to 8 litre petrol and diesel engines, but if you're just using it on smaller engines there are other makers offering smaller capacity devices at lesser prices. I have to say the Streetwise name put me off a bit but I got in touch directly with them and they were very helpful even getting answers to my questions from the manufacturer themselves. I've seen this pack in several different colour schemes and even on American websites. I guess it's made in a "mega factory" somewhere in the east but seems well made and, for all the use it'll see with me I think it likely it'll outlive me. By the way, because it contains no battery at all, the projected life span is in excess of 10 years - unlike a battery device which might go half that before the battery is done - assuming you've been remembering to charge it!

 

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Just in case the above has whetted anyone's "appetite", here's a couple of videos I found interesting when I was researching this jump pack. By the way, it seems to be branded Keen Power over there.

And a very interesting one comparing a battery powered pack with it of similar capacity. I was particularly interested in the fact that both packs worked on vehicles where the battery was completely dead - albeit, of course, that both packs had to be charged separate from the vehicle being as how the vehicle battery was completely dead. I believe many of smaller packs just don't have enough "oomph" to drive the system when there's nothing in the battery at all and many won't "kick off" unless they can detect a certain minimum battery voltage. Another reason why this Streetwize appealed to me. Having to activate the heater plugs was just too much for all but the biggest pack. I suspect the Streetwize would have turned it over if it had been a petrol though - you can hear it very nearly takes it over compression even after the glow plugs had taken a toll on it. Smaller capacity engines would start I think. I'm talking about what happens at the end of the second video here.

I must admit to finding something quite appealing about the chap presenting the videos! Look like a "no nonsense sort of guy!

It's interesting to see, at the end of the second video, that really nothing except another nice big battery is going to get you going if the vehicle battery is completely flat. Oh well, if I come across that situation I'll just have to go back to my garage and pick up one of the big shop batteries!

Also worth saying, doing starts this way - with a jump pack or slave battery - is basically giving the vehicle electronics access to just a normal battery voltage. It's very unlikely indeed that when the engine starts there will be the risk of a voltage spike which could destroy any of the components. Also interesting that the Streetwize instructions recommend leaving the pack connected until it's fully recharged which I agree with as this will let the vehicle charging system put some charge into the vehicle battery and greatly reduce the risk of spiking when the pack leads are disconnected. In fact, whenever jump starting you should leave the leads connected for about 5 minutes so voltages can stabilize - Never, especially if you've risked jumping from another vehicle, disconnect leads immediately after the jumped vehicle engine fires up - always leave them connected for a time. Also DO NOT turn on the ignition switch and operate the starter on the vehicle with the flat battery whilst the ignition is still switched on and/or engine is running in the "good battery" vehicle. If it's ignition is still on when you start the vehicle with the flat battery then both vehicle's electrical systems are "talking" to each other and ECUs really don't like that. It's at that moment of fire up that most damage is usually done.

 

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I've been doing a bit of "pondering" on the above. I believe, from videos and reviews I've read, many of the small battery type units won't allow connection to the system unless they detect a certain minimum battery voltage - which means they won't even attempt to start a vehicle with a substantially discharged battery. I can well imagine this is to protect their internal battery from what would otherwise amount to a straight short? When you start looking at very depleted batteries, you really need something "meaty" for success because the severely depleted battery is going to immediately rob electricity from the donor battery.

Traditionally I've overcome this by having my large "workshop" batteries as a source of power but it's asking an awful lot of a relatively small jump pack to do this. I was especially interested to see, in one of the videos, the Keen Power (Streetwize) pack did attempt to turn the large Diesel engine over even though the large truck battery was completely flat and it must have robbed a lot of the power from the pack powering up the heater plugs before an attempt to operate the starter was made. I would guess it would probably start one of our smaller European car diesel engines which would have a smaller battery to initially "rob" the pack and require less energy to turn the engine over?

The other very interesting demonstration was using it on it's own (no vehicle battery connected) to start that car in the video. Most packs won't work unless they "see" some battery voltage when connected. With this setup though, if you run into a very flat battery, you could pull one of the battery leads so the battery is no longer in circuit. Jump the car by connecting to it's battery leads and then, before disconnecting the jump pack, pop the disconnected lead back on the battery - whereupon the alternator should put some charge back into the battery and allow the car to run - This is in fact a very old "trick" we used, back in the day, when trying to start any vehicle with a very flat battery using just a normal workshop battery. Having said that though, the best thing to then do is run it straight into a workshop/auto electricians and get the whole thing checked out because if you stop it it may not restart! Of course you'd have to charge the pack separately - either from another vehicle or using the mains usb charger (usb as a last resort because it does take quite a while they tell you) but it gives you an option not available with anything other than a large slave battery.

Please do comment and leave some thoughts on this folks. I'm fascinated to hear your opinions.