Charging system advice M1010

[Keith_J]

Ok, so it equalizes with the engine off. 12.3 volts means about 50% charged

I just found some mention that it divides the input (24 volt) in half to go to the 12 volt side. This would mean the A battery will charge at 1/2 the alternator output, around 14.2. Cool.

 

[lavarok]

By the way, there is a little led that lights up when the unit is "on".

This and the physically hot relay ( next to starter relay ) led me to the conclusion that the master light switch needs to stay off when the truck is not in use. Otherwise, you will have a parasitic drain on the 12v system.

 

[lavarok]

Ok, so it equalizes with the engine off. 12.3 volts means about 50% charged

I just found some mention that it divides the input (24 volt) in half to go to the 12 volt side. This would mean the A battery will charge at 1/2 the alternator output, around 14.2. Cool.

What do you mean 50% charged? I've never seen more than 12v being output from the unit. If the unit is supplying the 12v side power, there is no need to charge the front battery. The front and rear battery get charged together from the Leece Alternator at 28.5v

Remember, the unit works whether the truck is running or not so 12v use wont drain the front battery. Both batteries will equally be drained to supply 12v power.

However, if "A" was lower than "B", the equalizer would detect this and run 12v into the "A" side to equalize the batteries.

I've had this setup in my M1010 for almost 7 months and it has been working flawlessly.

 

[Keith_J]

Fully charged 6-cell lead acid batteries are 12.6-12.8 volts. Fresh off a charger, the voltage can be as high as 13.8 volts due to "surface charge" effects. This will drop to 12.6-12.8 volts after a day or so as the charge is absorbed into the plates. The full charge voltage varies with construction, typically automotive batteries are flooded cell.

When being charged, the voltage "drives" the charge, hence the 14.2 volt regulation of most alternators. Or in other terms, current flows because of the voltage difference.

The state of charge of a battery can be determined by measuring the voltage of a rested battery, typically 24 hours. Since the concentration of sulfuric acid decreases with discharge, specific gravity of the electrolyte falls from 1.270 at full charge to 1.125 when fully discharged.

 

[lavarok]

My batteries may be slightly low as it was just recently "I left the lights on" and slave started the truck. It was the rear fluorescent that was left on.

I drove her around that day, parked it and drove it again 2 days ago. I may not have given the system enough time to come fully up. I should probably put my 24v battery minder on her to be sure.

Thanks for the info!

 

[lavarok]

Keith ( since your clearly an electrical guy ) - what are your thoughts on my setup with both Leece alternators wired to the 24v bus?

This is one area of my setup I am still unsure about. I've read some stuff that suggests the two alternators working together may do more harm to each other than good for the system.

 

[Keith_J]

Keith ( since your clearly an electrical guy ) - what are your thoughts on my setup with both Leece alternators wired to the 24v bus?

This is one area of my setup I am still unsure about. I've read some stuff that suggests the two alternators working together may do more harm to each other than good for the system.

Without going over it in person, you probably have a better setup. You see, back in the 1980s, high power MOSFETs were just not available, hence the complex setup of the Duvac/Twinput. The problem with this original setup is number of connections AND the switching of the upper alternator by the Twinput to "simulate" 14.2 volts. The high power electronics in the Duvac are themselves nearly bullet proof Silicon Controlled Rectifiers (SCRs).

As long as the wiring changes to the upper alternator parallel the lower, meaning fusible link from the 24 volt terminal to the 24 volt main block, it will work. The only question wire is the Brown 39G wire going to the middle terminal of the Twinput regulator. This could be used to energize a 100 amp relay so the unit could be disconnected from the A battery. This isn't needed as the equalizer "splits" the voltage and is designed specifically for this application.

 

[lavarok]

I was specifically referring to your opinion on the two alts wired in parallel, not the whole setup.

I removed all the wiring and components that went to the original duvac setup. So that brown wire is history.

I did wire the top alternator exactly like the bottom with the IGN of both units tied together. They will each see the same "field" when the truck is started.

So far so good.

 

[Keith_J]

Well, if you installed a jumper from the top to the bottom on the +24 volt output, you doubled the current. This might be an issue on really dead batteries or high loads. The ignition wire only draws 3-6 amperes, it could also overload but it is fuse protected at 20 amps. You could have used the Brown 39G for the upper alternator. In any case, this IGN connection supplies power to the regulator AND provides an independent "sense" for the regulator to compare. Doubling the load on it can cause voltage depression, resulting in over-charging. When the regulator senses a low voltage state from this lead, it increases current to the field which causes more voltage drop.

For mkcoen's M1010, any modification I do will come with an updated wiring diagram (Appendix F10) for his vehicle's TM. Might even edit the troubleshooting procedures. But definitely put battery disconnect procedures under the hood, this might be the cause of Duvac/Twinput issues.

 

[lavarok]

The output of each alt is wired to the 24v bus bar. Only the IGN was jumped to supply a "field" to the top alternator. What do you do for a living? Something electrical I presume.

Battery disconnect procedures should remain the same for all CUCVs regardless of the 12/24 setup. The AL NG painted the steps on the underside of my M1009 hood and it is a nice touch.

 

[Keith_J]

Good job on the wiring from the top alternator to the 24 volt bus. At 100 amperes, 10 gauge wire with a 6" section of flame resistant (PVC at bare minimum, silicone better) as a fusible link is a good idea.

I'm a Mechanical Engineer but with 12 semester hours of electronics, network theory and labs, I find it to be a cheap hobby.

Always negative A, then negative B. Positive A, then positive B. The A battery is forward on the CUCV. The Deuce has the A battery in the back...start with ground wire first.