WD 6V Pertronix

This is for Gerald J, but may help others or others may have ideas.  I have a 1952 AC WD in mostly original condition, but  40 years ago had M&W Power Pistons installed on overhaul, which makes it harder to crank.  Has original pos. gnd 6V, coil, generator, starter, lights, and cutout on generator, I would like to keep it that way, (no 12V please!!!), except for a Pertronix ignition installed about 10 years ago.  When above 40F and battery 75% or more draws about 300 amps, always starts on first or 2nd compression stroke.  When cold(<30F) or battery less than 50% (Often low with 6V gen. and cutout!) the engine cranks very slowly at the top of compression and draws lots of current, nearly 500 amps at top. (below 30 F, crank by hand,starts well).  This means that the voltage measured on the battery terminals drops to about 3.3 volts and about 3.1 volts at the starter during top of compression, and will not start, no spark.  The original (Sprague, Microswitch) Hall sensors used in the Pertronix module at that time were specified at 4 or 4.5 volts, minimum! What is needed is a sort of DC transformer, a "buck/boost supply" to output a constant 3.2 amps at 5 or 6 volts to the Pertronix and coil.  I have found this: http://www.linear.com/solutions/7790 but cost $225! I am not willing to spend that much when I am not sure that it will withstand the electrical environment of a tractor ignition(load dump, high voltage transients, undervoltage, etc).  I do not have the skills or equipt. to build one. 

you might want to get your starter rebuilt. not just brushes and bushings. if its drawing a good battery with good clean large cables down. I use 00 and a flat braid ground.  its drawing to many amps.

8v Will probably blow that pertronix.  I have sold them for 15 years, not as long as Steve.  I do not sell the 6v units because the window of operating voltage is too narrow. I understand what the original poster is getting at, but my capabilities there just don't exist.

Im sure they do.  Would have to look up distributor number

Optima use to make a 6 volt AGM battery. I don't know if they still do or not. With AGM the battery internal resistance is lower and the battery voltage should hold better. That's about all I can think of other than using a booster battery when it's very cold.

Put a WD45 Diesel battery box and two 6 volt batteries with 00-cables in her and she will start like it 70* outside! LOL

Here's a potential economical solution for you. I have used simialr units from BG to drive 12V LEDS from 2 D cells.....

https://www.banggood.com/DC-DC-Boost-Buck-Adjustable-Step-Up-Step-Down-Automatic-Converter-XL6009-Module-p-1087346.html?rmmds=search

It'd also be good for running 12V LEDS on a 6V 'G'......

If the link doesn't work, just go to Banggoods website enter 'xl6009' in the search box.

I can't buy the parts for double what they sell complete modules for !

There may be a better unit, search for 'boost-buck convertor'. I tend to get 'lost' on the site...150,000 items is a lot of stuff to look at !!
Please don't blame me when you order 1,000 of $$ of stuff ! Friend is getting 2-3 packages a week as the deals are really,really good.

Jay

Two small power diodes will prevent 'backfeeding' issues yet allow the EI unit to get solid power. If using a second battery , an on-off switch inline will be needed and a fuse is a good idea.
If using a buck-boost module nothing else is needed. 6v feed from ign switch goes to it, it then feeds the EI unit.

Jay

I think there's a need for a solar powered battery rechager/maintainer at the tractor shed. Since there's no AC power(cept the WD...), solar would be a viable option to ensure the battery is at it's best. You'll have to find a '6 Volt' solar setup though as most common is 12 volt systems. Something capable of 2-4 amps would be nice.
If you used Schottky diodes instead of silicon the Vdrop is only .2 volts. Really 'nothing' in the overall scheme of things.
The major problem with 6 volt batteries is maintenance. Super clean contacts,proper electroyte level, fat cables... all those things we tend to forget to look at since 12 volt is so forgiving...

Jay

If you don't skimp on the size of starter cables and regular cleaning of connections, the original 6 volt system will work adequately. I am sure the 6 volt pertronix won't survive 8 volt system, and if there are any lamps they will have severely shortened lives. The increased current in the points and coil will shorten their lives too.

8 volts is a cobble to allow skinnier starter cables and more neglect of cleaning battery posts and connectors. Its not original, hasn't ever been original.

Gerald J.


Edited by Gerald J. - 23 Jun 2017 at 9:28am

If you don't want to go to 12 volt then change over to a mag?

Check the ground path from the battery to the starter. Doesn't take much corrosion to increase resistance and cause a severe voltage drop under load.

Years ago we had a piece of equipment we used an 8V batt. in and it was no problem. But it's your call. I also prefer the big cables. I have the same problem as you do on a WD45 so I made my own cables out of eighteen wheeler cables which are huge. Guess what, still got the same problem. Tried four different starters, no go. A long time ago I had a 6V Chey. pickup that didn't turn over good. The coil went bad and with a new coil it would turn right over. Guess I'll be heading that direction.

I believed I've already checked that, but I will make sure. Thanks

Keeping the battery fully charged is essental too. With the old 6 volt cutout system you never knew when the battery was charged unless you used a hydrometer or put the battery on a charger.