dan-o

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Ok, old skool electrical question...
I just got this '89 F35 7.3 IDI with the Ambulance package that I (WE, the wife is watching me) are turning into a RV.
It has a 200 amp Leece Neville alternator and the three cable coming off of it go to a remote rectifier.
One of the cables from the rectifier comes back to this component.
Then the wires seem to go the main battery disconnect switches in the cab.
I'm pretty sure this is some type of fuse. BUT, i'm not certain.
Since I'm getting ready to invest in some expensive add ons, I don't want this thing to torch itself.
I know the blue box looks like it has seen some heat, but it is 30+ years old. I would like to upgrade this if I could, but, again, not sure what it is!

Thoughts?
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FrozenMerc

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Definitely a voltage shunt resistor. It creates a voltage difference that is equivalent to the amperage running through the heavy lead wires. The small gauge wires most likely run to a meter or gauge.

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aggiediesel01

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Shunt is exactly what that is, the slotted hole on the red wire is so you can calibrate the gauge reading against a calibrated reading on the incoming heavy wire.
 

dan-o

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Sounds like something that I don't want to mess around with. I plan on installing a Renogy DC-DC battery charge controller to charge up the coach LiFePO4 battery. My current thought (no pun intended) is to tap off of the main lug on the rectifier +. The Renogy is a 40 amp charge controller so I will gauge the wires accordingly. Will this screw up the shunt circuit? Is there a way I can balance this with a Fluke meter, amp meter? Would I even need to, as the new controllers are supposed to be 'Smart'? I don't normally trust anything 'smart'. I'm a true Luddite, sometimes.

Thanks, guys. Really!
 

aggiediesel01

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Sounds like something that I don't want to mess around with. I plan on installing a Renogy DC-DC battery charge controller to charge up the coach LiFePO4 battery. My current thought (no pun intended) is to tap off of the main lug on the rectifier +. The Renogy is a 40 amp charge controller so I will gauge the wires accordingly. Will this screw up the shunt circuit? Is there a way I can balance this with a Fluke meter, amp meter? Would I even need to, as the new controllers are supposed to be 'Smart'? I don't normally trust anything 'smart'. I'm a true Luddite, sometimes.

Thanks, guys. Really!

Need a little more information about where exactly those cables come from and go to before deciding to connect something additional in that box. You described a bit of it in the first post but there's a few things left unsaid. If the single cable at the bottom of your picture is the one coming from the rectifier and the two cables at the top of the picture go out to battery isolation switches then I would recommend connecting your battery charger downstream of the shunt/box. If you connect a load upstream of the box (toward the rectifier) the additional current draw on the system won't be measured by the meter connected to the shunt. The shunt can only measure current that passes through it. If it were mine, based on how you've described it so far, the only new loads I would connect would be after the isolation switches as this way the system still maintains the ability to completely isolate the loads from the supply, I think that is generally a good thing. I suspect that there is a decent power distribution arrangement after the isolation switches and I would tie the charge controller in there but before the power distribution.
 

dan-o

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Thanks, Aggiediesel!
Yes, there are two isolation switches in the cab. One turns the batteries OFF completely. The other sends electricity back to the ambulance section. In that section there is an awesome electrical distribution panel. Huge positive post and a huge negative post. That is where I'm going to connect my DC-DC charger. The charger comes on when I turn it on via a switch. That way I can let the alternator charge up the starting batteries and then charge up the camper battery.
Another cool thing is that with the inverter I can run a standard battery charger to charge up the starting batteries with the RV Lithium Iron Phosphates that can be charged from the solar panels.
It looks GREAT on paper! Time will tell.
 
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