DC - DC Charger Project

[Guest]

Guest
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I see Victron Orion-Tr Smart 12/12-30A DC-DC charger has two models Non-Isolated (3 terminals hot in, ground, hot out) and Isolated (4 terminals +/- in and +/- out with chassis ground. What is the difference and which is better? I am thing that as the only real ground between the truck and trailer is maybe a 12 gauge wire in the cord, I need the isolated so I can bring the negative cable to it.
wygieman
How is you Renolgy 60A holding up. I was reading reviews and folks are having a few random quality issues. Appreciate the input on the alternator, but the 2022 supposedly have something new where it can output more if called for, up to 30A - still reading up and need to verify the wiring.. My new order truck has the instant cab heat so will have the 397 amp alt.

Keith,

I struggled with connecting my Renogy with both input and output grounds (4 wire) where after checking with an EE at work, I grounded both input and output to the negative buss bar on the trailer which is grounded to the trailer chassis. Since the trailer battery is grounded to the trailer chassis to operate the rig and the TV is grounded to the trailer chassis in order to operate lighting, I didn't see another way of getting around this. The system works as intended where the positive terminal is isolated from the RV (unless the Renogy is active) but the TV and RV share a ground. If your intending on running dedicated +/- wires from your TV, I would use the 4 terminal unit for a high output unit like a 30amp model. Otherwise, you will be using the chassis ground on the trailer to handle the high current load in charging your batteries. If your adding heavy cabling on the trailer batteries to ground, either unit will work IMO. A confirmation from an electrical guru would be welcome here.

Jim

[Jimmer]

Keith,

I struggled with connecting my Renogy with both input and output grounds (4 wire) where after checking with an EE at work, I grounded both input and output to the negative buss bar on the trailer which is grounded to the trailer chassis. Since the trailer battery is grounded to the trailer chassis to operate the rig and the TV is grounded to the trailer chassis in order to operate lighting, I didn't see another way of getting around this. The system works as intended where the positive terminal is isolated from the RV (unless the Renogy is active) but the TV and RV share a ground. If your intending on running dedicated +/- wires from your TV, I would use the 4 terminal unit for a high output unit like a 30amp model. Otherwise, you will be using the chassis ground on the trailer to handle the high current load in charging your batteries. If your adding heavy cabling on the trailer batteries to ground, either unit will work IMO. A confirmation from an electrical guru would be welcome here.

Jim

I have the Renogy 60amp DC-DC charger in my travel trailer. It has worked perfectly since it was installed about 4 months ago. The negative terminal of the batteries in the travel trailer trailer are connected to the trailer frame through a bus bar. The ground from the tow vehicle is connected to the trailer frame. I don't see how how having a common ground for everything could be a problem.

Jim, you wrote in your post "Otherwise, you will be using the chassis ground on the trailer to handle the high current load in charging your batteries." What's wrong with this? I'd rather have 60 amps running through my truck frame and camper frame than a wire. As long as there is a solid/clean connection to the frame, it will work perfectly. The Victron smart shunt shows that my Renogy 60 amp charger is putting out over 59 amps into the batteries, so it is working as intended.

[howson]

Yoda Guest and Jimmer

Forgive the pontification, but I despise the word "ground" when discussing 12vDC. 12v Return or -12vDC is a more apt description because the output from a battery will find it's way back to the battery. Ground is a term that should be used with AC (in this case literally ground as electricity will find it's way back to the power source via the ground if necessary).

The point of the last two sentences is to suggest thinking in terms of minimizing the electrical resistance between the DC-DC Charger and the tow vehicle's battery (or batteries). For the relatively long distance involved from the front of a modern truck to the trailer's battery bank, designing a system with the minimum possible resistance (and accounting for losses) is an important consideration.

Jimmer -- your post states, "...ground from the tow vehicle is connected to the trailer frame,...". Could you expound on how this was done on your setup?

Howard

[Jimmer]

Yoda Guest and Jimmer


Jimmer -- your post states, "...ground from the tow vehicle is connected to the trailer frame,...". Could you expound on how this was done on your setup?

Howard

The negative wire/ground from the tow vehicle goes to the trailer through an Anderson connector. From the Anderson connector on the trailer, I run the black/negative/ground wire to the frame of the trailer through a self tapping bolt (The frame is boxed so I couldn't easily use a nut/bolt). I ground down the paint off of the trailer frame at the point of connection to bare metal. Covered the frame and terminal with NO-OX-ID A-Special- Electrical Contact Grease. I may have used a stainless steel washer, although I can't see it in the picture. When it was all assembled, I painted it black. Did something similar on my truck, but drilled through the truck frame and used a stainless nut and bolt. I don't know how long it will be before corrosion starts to deteriorate the connection, but 4 months after I did it is working perfectly.

[Guest]

Jim, you wrote in your post "Otherwise, you will be using the chassis ground on the trailer to handle the high current load in charging your batteries." What's wrong with this? I'd rather have 60 amps running through my truck frame and camper frame than a wire. As long as there is a solid/clean connection to the frame, it will work perfectly. The Victron smart shunt shows that my Renogy 60 amp charger is putting out over 59 amps into the batteries, so it is working as intended.

Jimmer,

"Otherwise, you will be using the chassis ground on the trailer to handle the high current load in charging your batteries. If your adding heavy cabling on the trailer batteries to ground, either unit will work IMO."

Jim


The next line explains that if a heavier ground is added this would not be a problem. The ground I was referring to is the original 6 awg ground wire which would be inadequate IMO for a high current DCDC.

Jim

[Guest]

Yoda Guest and Jimmer

Forgive the pontification, but I despise the word "ground" when discussing 12vDC. 12v Return or -12vDC is a more apt description because the output from a battery will find it's way back to the battery. Ground is a term that should be used with AC (in this case literally ground as electricity will find it's way back to the power source via the ground if necessary).

The point of the last two sentences is to suggest thinking in terms of minimizing the electrical resistance between the DC-DC Charger and the tow vehicle's battery (or batteries). For the relatively long distance involved from the front of a modern truck to the trailer's battery bank, designing a system with the minimum possible resistance (and accounting for losses) is an important consideration.

Jimmer -- your post states, "...ground from the tow vehicle is connected to the trailer frame,...". Could you expound on how this was done on your setup?

Howard

Howard,

The vehicle OEM drawings are full of references of vehicle grounds where the TV battery is connected to a chassis ground. Most other circuits in the TV are connected to a plethora of chassis grounds where the vehicle chassis is used for the return back to the battery. The same method is used in our trailers.
For AC I believe your referring to an earth ground.

Jim

[Yoda]

OK this may sound like a really dumb question at this point, but with all the good options open to me on what to chose and with my bank of 4- 6V 260Ah batterys in series/parallel 520 total AH (260 usable) - How much DC-DC charge power do I REALLY need? I know lots of if's. Lets say overnight I am down to 12.4 volts 70% SOC. Assume 4 to 6 hours of driving, and I have no idea how to adjust for solar 540w - lets assume rainy day...Check my math - .70% SOC means I need to recover 30% of 520 AH or 156 AH or is it 30% of 260AH or 78 AH. Assuming the 30A I would need 5.2 hours driving time for the former and if the latter just 2.6 hours to recover? I am also thinking if I go Lithium in the future I will be in better shape as they charge faster - correct?

I know I am missing something here
Thanks Keith

[Guest]

OK this may sound like a really dumb question at this point, but with all the good options open to me on what to chose and with my bank of 4- 6V 260Ah batterys in series/parallel 520 total AH (260 usable) - How much DC-DC charge power do I REALLY need? I know lots of if's. Lets say overnight I am down to 12.4 volts 70% SOC. Assume 4 to 6 hours of driving, and I have no idea how to adjust for solar 540w - lets assume rainy day...Check my math - .70% SOC means I need to recover 30% of 520 AH or 156 AH or is it 30% of 260AH or 78 AH. Assuming the 30A I would need 5.2 hours driving time for the former and if the latter just 2.6 hours to recover? I am also thinking if I go Lithium in the future I will be in better shape as they charge faster - correct?

I know I am missing something here
Thanks Keith

Keith,

If your running a dedicated power and ground circuit why not get the larger output model? Your FLA batteries will only accept so much but if you switch to lithium they will pull all that power in.

Jim

[ncitro]

Keith,

If your running a dedicated power and ground circuit why not get the larger output model? Your FLA batteries will only accept so much but if you switch to lithium they will pull all that power in.

Jim

Yes this was going to be my suggestion, I have no idea if your flooded batteries would take that much for that long (or if it would be good for them, they might boil out) but if you're considering lithium in the life of the rig then it will be worth it.

[Guest]

Yes this was going to be my suggestion, I have no idea if your flooded batteries would take that much for that long (or if it would be good for them, they might boil out) but if you're considering lithium in the life of the rig then it will be worth it.

Neil,

Thinking that with a 30amp (updated) DCDC being distributed to 4-6v battery bank should not be an issue. But it would certainly be best to check with Crown battery. The lithium battery bank is of no concern, where I charge my single 100ah lithium battery at 0.5C (50-55amps).

The Renogy has a switch to cut charge rate in half where if Keith is working to buy a DCDC, and to charge FLA batteries until he switches to Lithium, the Renogy may be the best bet. I am reading that many golf cart chargers are 25amp so a 30 amp Renogy may be the best compromise. A switched 15amp for FLA and the full 30amp for lithium. The charge profiles are also switchable on the Renogy.

https://www.crownbattery.com/news/to...ry-maintenance

Jim

[Yoda]

Neil,

Thinking that with a 30amp (updated) DCDC being distributed to 4-6v battery bank should not be an issue. But it would certainly be best to check with Crown battery. The lithium battery bank is of no concern, where I charge my single 100ah lithium battery at 0.5C (50-55amps).

The Renogy has a switch to cut charge rate in half where if Keith is working to buy a DCDC, and to charge FLA batteries until he switches to Lithium, the Renogy may be the best bet. I am reading that many golf cart chargers are 25amp so a 30 amp Renogy may be the best compromise. A switched 15amp for FLA and the full 30amp for lithium. The charge profiles are also switchable on the Renogy.

https://www.crownbattery.com/news/to...ry-maintenance

Jim

ncitro

When I talked with Crown a while back in setting up the Multiplus they gave me the following charger setting information for my bank of batterys.

My Victron MultiPlus is capable of 120 charging amps. This setting can be adjusted. What do you recommend?

The wiring configuration of your batteries results in a 12 volt / 520 Ah bank – the MAX amp input is 20% of Ah capacity; or 104 amps in your case…Generally speaking though, the “sweet spot” is an amp input setting of 12%-15% of the bank’s Ah capacity

I set the Multiplus to 75 amps (three amps shy of 15% which is 78 amps), so the 60 amp charger is also right in what I should have. So I guess I am back looking at the Renogy 60 amp version. Now to find a sale on it and 4 awg wires and the Anderson connectors, along withe down under bulkhead fitting. One new question - I am guessing the total length of wire run is going to be close to 30' (truck battery to 5th wheel battery bank (includes 6' for the trailer connection cord) as the truck side will see close to 80 amps (I seem to remember folks seeing 80 amps when in operation) (90A recommended fuse from Renogy manual), should I be using 2 awg? How important is the voltage drop?

Thoughts?

Thanks Keith

[wygieman]

ncitro

One new question - I am guessing the total length of wire run is going to be close to 30' (truck battery to 5th wheel battery bank (includes 6' for the trailer connection cord) as the truck side will see close to 80 amps (I seem to remember folks seeing 80 amps when in operation) (90A recommended fuse from Renogy manual), should I be using 2 awg? How important is the voltage drop?

Thoughts?

Thanks Keith

]

I am sure Neil will weigh in but IMO, the voltage drop in this situation is unimportant. The purpose of the Renogy is to get the voltage correct so it will take care of voltage by pulling amps. When using my 60A Renogy with 4 awg wire, I pull 83 amps with a 16% voltage drop to get the 60 amp charge with a 100 A breaker. Btw, I think that you should expect more like 40+ ft for the length of the wire. I had very little left over from a 50 ft spool. I did leave the connector longer than necessary for flexibility when charging not hooked up.

[Guest]

ncitro

When I talked with Crown a while back in setting up the Multiplus they gave me the following charger setting information for my bank of batterys.

My Victron MultiPlus is capable of 120 charging amps. This setting can be adjusted. What do you recommend?

The wiring configuration of your batteries results in a 12 volt / 520 Ah bank – the MAX amp input is 20% of Ah capacity; or 104 amps in your case…Generally speaking though, the “sweet spot” is an amp input setting of 12%-15% of the bank’s Ah capacity

I set the Multiplus to 75 amps (three amps shy of 15% which is 78 amps), so the 60 amp charger is also right in what I should have. So I guess I am back looking at the Renogy 60 amp version. Now to find a sale on it and 4 awg wires and the Anderson connectors, along withe down under bulkhead fitting. One new question - I am guessing the total length of wire run is going to be close to 30' (truck battery to 5th wheel battery bank (includes 6' for the trailer connection cord) as the truck side will see close to 80 amps (I seem to remember folks seeing 80 amps when in operation) (90A recommended fuse from Renogy manual), should I be using 2 awg? How important is the voltage drop?

Thoughts?

Thanks Keith

Keith,

Using the Ampacity chart I would use the critical voltage drop scale and determine the cable size based on the maximum output that your Multiplus is capable of inside the rig. Properly delivered voltage to equalize FLA batteries or to balance Lithium batteries is important. So I would wire this with 0awg taking into consideration of the critical voltage drop and to set this up to handle up to 90 amp for when you move to lithium for the TV side.
Initially I was concerned your charge rate would be at 0.1C but if your capable of 0.2C then the 60amp Renogy would work very well and can handle both battery types via dip switches.

Copper wire is crazy expensive right now. Recent home wiring projects just cost me plenty.

Jim

[TedS]

When using wire length charts, remember that for dc wiring to use the total of both + and - , out and back, wire lengths.

[Guest]

When using wire length charts, remember that for dc wiring to use the total of both + and - , out and back, wire lengths.

Ted,

Wouldn't the load calculation be the same on the return path?

Jim