24 volt conversion... sort of

[Curtisje]

I bypassed the glowplug resistors a while back because others had done it. I also have a volt meter on each battery so I can see how each is doing. I didn't like watching the front battery drop to 10V or lower during startup nor am I a fan of swapping the battery positions every few months. I run a lot of 24 volt accessories that I have from surplus government vehicles... 2 24 volt winches, many lights and an Outback 24 volt inverter/charger sooooo.... I went a different route. I installed a 120 amp 24v to 12v inverter to run the 12 volt side if the truck but pull voltage from each battery equally all the time. It was pretty simple and so far it is working well.

I have a 2 gauge wire that comes off the inverter and feeds the 12 volt block on the firewall where the truck and glowplug solenoid draw their 12v from.


I installed a 12 volt block in between the batteries. The positive side of the front battery and the negative side of the rear battery are connected here. I had to route the alternators the same way otherwise this wouldn't work. (The drivers side feeds right into the block on the firewall normally.)


I mounted the inverter to a piece of 3/16 plate that I cut and drilled and hung it from the rear battery hold down. I also installed a 500 amp battery disconnect on the 24v side. There is a 24v 80 amp circuit breaker protecting the input side if the inverter (as required). Best of all if the inverter fails I can simply disconnect the 12 volt output wire and reconnect it to the 12v junction right there next to it.

Now both batteries are drawn from for everything. It is actually a constant 13.8 volts output so now my blinkers and everything 12 volt run very consistently. There is still quite a draw from the batteries during startup but it is nice to see each drop to around 11 volts rather than one dropping to 10v.

I hope your team won the superbowl. Stay safe out there.

 

[Keith_J]

Very interesting..120 amperes is enough to feed the glow plugs?

 

[Curtisje]

Very interesting..120 amperes is enough to feed the glow plugs?

From all my research the glowplugs will pull less than or about 80 amps. I added another 20 for anything else that has a draw during startup and another 20 for a safety margin. So far it is working. I drive it daily.

 

[Keith_J]

Interesting. I have a digital ammeter which shows charging current at the left alternator ground. After starting, its 95+ amperes for a few seconds. I might relocate the shunt to the front battery negative to see actual glow plug draw.

Your mod will be helpful as I am moving the engine forward 1.75 inches to accommodate a 4L80E transmission. This plus the extra space from getting rid of the ballast resistor bank could be a perfect spot for a turbocharger or two..think a pair of GT2254Vs would fit.

 

[Curtisje]

I purchased a 400 amp multimeter. When the key is turned on and the wait light comes on the system starts pulling 12 volts at 126 amps. As the cycle continues the amps steadily drop down to 88 amps when the cycle ends and the wait light goes out. With the wait light out the rest of the system is pulling 5 amps. So my calculations were wrong and it's a good thing that I bought the 120 amp converter.

 

[Keith_J]

That is a realistic number. I had another idea of using a small spiral cell 12 volt battery to power the glow plugs. Then a 20 amp 13.8 volt converter would serve to keep this battery topped off.

 

[Curtisje]

Still working great. I have had zero issues with this modification.

 

[John Mc]

I installed a 120 amp 24v to 12v inverter to run the 12 volt side if the truck but pull voltage from each battery equally all the time.

When bought my M37, it had a 720 watt (60 amp) DC to DC converter in it to handle some of the loads in the hybrid 12/24V system that was in i at the time. I've not realy done any in-depth searches, but I'm curious where you found a 120 Amp DC-DC converter. I've never come across one that large.

(I've since converted back to the original 24V system, s this is more curiousity than anything else.)

 

[Curtisje]

When bought my M37, it had a 720 watt (60 amp) DC to DC converter in it to handle some of the loads in the hybrid 12/24V system that was in i at the time. I've not realy done any in-depth searches, but I'm curious where you found a 120 Amp DC-DC converter. I've never come across one that large.

(I've since converted back to the original 24V system, s this is more curiousity than anything else.)

Daygreen makes it. Chinese but so far so good.

24V to 12V 120A 1440W DC DC Step Down Converter Voltage Regulator

Wide input voltage from 18 to 35V Work for appliances from 0AMP to 120AMP automatically 100% full rated power 100% full stable output current 100% burn-in test High-efficiency up to 95% Waterproof sealed Cooling by free air convection Surface mountable 2-year warranty Over-current, over-voltage...

daygreen.com

 

[John Mc]

Daygreen makes it. Chinese but so far so good.

24V to 12V 120A 1440W DC DC Step Down Converter Voltage Regulator

Wide input voltage from 18 to 35V Work for appliances from 0AMP to 120AMP automatically 100% full rated power 100% full stable output current 100% burn-in test High-efficiency up to 95% Waterproof sealed Cooling by free air convection Surface mountable 2-year warranty Over-current, over-voltage...

daygreen.com

Thanks for that link. I see they also make 24V to 13.8V converters. 13.8 V simulates a running vehicle, where 12V on the nose would be closer to a fairly deeply discharged battery. I'm not sure if that makes much difference in the real world - perhaps losing just bit of range on CB radio transmitter. I'm thinking most other electronics would not be affected in practice (i.e. turn up the volume on a car stereo a bit to compensate).

 

[Curtisje]

Thanks for that link. I see they also make 24V to 13.8V converters. 13.8 V simulates a running vehicle, where 12V on the nose would be closer to a fairly deeply discharged battery. I'm not sure if that makes much difference in the real world - perhaps losing just bit of range on CB radio transmitter. I'm thinking most other electronics would not be affected in practice (i.e. turn up the volume on a car stereo a bit to compensate).

Yes. The one I have produces 13.8v. I'm pretty sure I mentioned that somewhere above. I really like it and if/when it fails I can just switch one wire and keep on trucking. Good luck with your project/research.