Battery charger for V70

[Bernard333]

I paid about £75 for the RAC charger and used it twice on a fiesta and it started the engine with a flat battery no problem and then once on a 2.4T V70 and of course it couldnt cope , it started smoking immediately and the transformer made a loud buzzing noise for about 5 seconds before I realised what was happening and pulled the plug , I would not be complaining had the protection worked as it should and the internal thermal overload operated but it didnt . On taking the charger apart and testing the four 50amp button diodes(see photo ) one of them has a dead short which was causing all the output current from the centre tap transformer to feed through it , the 40amp thermal breaker in the line output did not operate and in my view this battery charger is a peice of **** and if I had not pulled the main plug the transformer would have happily fried itself to a cinder , so much for the claims in the Argos catalogue . What I dont understand is how this charger can possibly safely deliver two or three hundred amps even for a few seconds through diodes which are obviously at the very limit of their own individual performance and when you put two in parralel in each leg as in this charger the pair should be downrated by 15 to 20% at least , its a really horrible design and not worthy of the RAC name .

I think the transformer is OK as its still giving a voltage output but I have been searching for a UK distributor or shop selling 8.5mm button diodes and cannot find one , have tried RS Components , Ebay- dialec , Farnell , Maplin . The best I can find is a Taiwan based company Deltron Incorporated but they have min order of 1000 units , does anyone know where you can buy these diodes ? A few years ago there were lots of electronics shops in the UK where you could buy all kinds of components and today I cant even find one that sells a power diode , does anyone have a circuit diagram for this charger , I can understand roughly how it works but there is a pcb controlling the trickle and fast charging circuit which I cant follow , the boost circuit is easy to follow . Argos have withdrawn this RAC booster / charger from their latest catalogue , I wonder why , with hindsight I could have got something a lot better for a similar price off ebay and before I start using it again I will throw away the thermal overload and replace it with a fuse or mcb .

[V70Driver]

Hi,
Sorry to hear of your woes, sounds a bit frightening.
i will ask our electronics boffins on our aircraft simulators if they know where I can get these.
Will get back to you as quickly as I can.
Tell the RAC they shouldn't put their name to an item that is as bad as you describe.
Cheers
V70Driver

[V70Driver]

Could you give me a part number or picture of the item, so I can show our electronics boffins?
Thanks
V70Driver

[Bernard333]

Thanks V70 driver , will try to get a close up photo of the diode . I am told that these diodes are also used inside car alternators . The diode is marked MICRA501 and is 10mm round and 6.3mm thick and looks like a button and apparently its a standard size and package style for this type of diode which is strange why the major suppliers dont sell them .

[keithf]

Could you not rip open an old radio or something (broken) that would have the same diodes? Recycle what you can!

Edit: I know nothing about electronics, but have loads of (good and bad) suggestions!

[Bernard333]

Hi Kieth I appreciate your suggestion and wish there were a radio that uses 50 amp diodes but doubt I will find anything rated more than a couple of amps inside one , I do believe in recycling electronic parts but I probably take it too far , I still have a box full of old audio valves EL84 and EL34s just in case I ever get around to firing up my old amplifier and turntable , a friend recently advised me they are making a comeback but I think he is taking the mick .

[Stoney Strike]

Hi Kieth I appreciate your suggestion and wish there were a radio that uses 50 amp diodes but doubt I will find anything rated more than a couple of amps inside one , I do believe in recycling electronic parts but I probably take it too far , I still have a box full of old audio valves EL84 and EL34s just in case I ever get around to firing up my old amplifier and turntable , a friend recently advised me they are making a comeback but I think he is taking the mick .

Have you tried getting in touch with somebody like BT Forklifts, or Lansing Bagnall? Or anybody who does electric vehicles? There's afew who make golf buggies etc. It's the sort of thing that goes into the controllers. I worked for FKI as a young un'! They might be able to help, but try n get through to stores not sales! You want the bloke in a brown lab coat, with about 5 Bics in his left pocket, and goes pigeon racing of an eveneing! lol They're the blokes who know what's what at any kind of factory! lol

[Bernard333]

Thanks for the replies and through these have been able to get an alternative solution . Contacted manufacturers directly and got response , the Taiwanese advised me not to use the Chinese made diodes as they are not reliable and the Chinese can supply them at any price I like as long as I buy 10000 , I think I agree with this and diodes that fail by short circuiting rather than going open circuit I can do without . Have decided to replace all four button diodes with stud mounting types and will uprate them to 85amp 200V , Farnell turn out to be the cheapest on offer by using a good quality brand Vishay ( formerly IR ) at £2.41 each plus VAT . Next most expensive is RS Components at more than twice the price for the same thing and suprise the most expensive is someone on ebay selling the same thing at £8.50 each and he probably buys them from Farnell or even cheaper anyway until they arrive I have put the 3 good diodes back in and the charger works ok on trickle and fast charge although I am not going to risk using the boost position .

[V70Driver]

Hi Bernard333,
My electronics guys have informed me they cannot find a listing for a micra501. Unfortunately it is not something we use, so I am told, but was worth a shout.
Good luck
V70Driver