Off topic, battery charger question

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Model T Ford Forum: Forum 2014: Off topic, battery charger question
Top of pagePrevious messageNext messageBottom of page Link to this message  By Mack Cole ---- Earth on Friday, March 28, 2014 - 10:59 pm:

I have this battery charger that was handed to me as a freebee.
http://www.searspartsdirect.com/partsdirect/part-model/Diehard-Parts/Auto-batter y-charger-Parts/Model-200.71230/3206/0405000/P0305118/00001
Well I determined the rectifier diodes are bad.
I thought I could find a couple diodes. SO far no dice.
I am thinking since the unit has 200 amp for starting that the replacement diode would need to be 200 amp or more rated.But cant find any.
I am also thinking of getting a couple diodes from a hi amp car alternator and putting them in. Any input on how you would fix this?
2 diodes that should be common as hens teeth
.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Todd on Saturday, March 29, 2014 - 11:31 am:

Mack, try Digi Key or Mouser.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John McGinnis in San Jose area, CA. on Saturday, March 29, 2014 - 01:38 pm:

What are the symptoms? How did you determine that the diodes are bad? Check the diodes to see if they are OK, shorted or open. Diodes are common...stud mount? What do they look like. The photo is not clear.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mack Cole ---- Earth on Saturday, March 29, 2014 - 02:07 pm:

It is amp rateing that is confuseing me. If this thing is supposed to give 200 amps to crank something,, looks to me like I would fry a 40 amp diode. I think from what I read the 2 diodes are parelleled but still,2 40's is only 80. So I am missing something here as far as a mental picture.
Stud mounted.
It has been a while since I tested them but I am about positive the diodes were open. The man tryed to crank a tractor and it let the magic smoke out of them.
I tried to find the loose diode i had out of it and have lost it apparently.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Sunday, March 30, 2014 - 10:12 am:

Mack:

Diodes fail shorted typically but then can be blown open if the current source available has enough high current to blow apart the entire rectifier.

In Model T garages the most common reason that battery chargers fail is that T guys hook them up to T coils thinking that a high current charger can't be hurt by a lowly T coil primary. What happens is that the typical battery charger rectifier may be rated at many amps but usually not much voltage (pehaps only 100V or less) since in normal application it is only charging at most a 12V battery. The T coil can easily shoot a spike of voltage out of its primary that far exceeds the breakdown voltage rating of the charger rectifiers and they short due to their reverse breakdown voltage being exceeded.

DON'T use a valuable charger to "Buzz" your T coils are the old coil may have the last laugh on you and blow up your nice big (and perhaps new) charger. Even a 200 amp charger is no match for inductive spikes that can be generated by a single T coil being powered from it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Sunday, March 30, 2014 - 10:38 am:

John speaks the truth. Ask me how I know.......

I highly recommend the Fun Projects battery charger repair department.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie B actually in Toms River N.J. on Sunday, March 30, 2014 - 10:53 am:

For coils the best take up no space power source is an old toy train x-former. They usually have AC accessory terminals. Perfect for coils.


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