Isolated or non-isolated?

AJMike · 06-23-2020, 02:12 PM

Victron makes both isolated and non-isolated DC-DC chargers for charging Lithium batteries. When I spoke with the sales guy at one of the solar stores that carries Victron equipment he said that the isolated chargers are for those applications where there is not a common ground and that it is not necessary for RV applications since they have a common ground. Unfortunately I don't really know if he is right and if my Winnebago Fuse uses a common ground or not. I suppose I don't have enough of an electrical background and am not sure what I could check with an ohm meter to tell if there was a common ground.

We are currently camping near Flagstaff where the store is located and I was thinking about picking up the Victron charger on our way home, but since they don't have the isolated version in stock my choices are to buy the non-isolated and hope it works or order online from someplace and pay shipping. Can anyone tell me if RVs use a common ground? I am pretty sure cars do but am not sure about RVs.

Thanks for any help.

Winterbagoal · 06-23-2020, 03:10 PM

Kaibab Lake Campground? Off 64? Nice little place if you like simple.

AJMike · 06-23-2020, 03:22 PM

Quote:

Originally Posted by Winterbagoal

Kaibab Lake Campground? Off 64? Nice little place if you like simple.

Boondocking near Dogtown Lake. Terrible road getting here. And a tad hot for this altitude. Above 90 in RV.

Any info on common ground?

Winterbagoal · 06-23-2020, 03:30 PM

Quote:

Originally Posted by AJMike

Boondocking near Dogtown Lake. Terrible road getting here.

Any info on common ground?

Sorry, not really from an electrical engineering perspective.
Thinking about it (logically?) since there's usually no conductive part of the motorhome touching the earth, and the vehicle frame is usually the grounding point for the most common electrical applications, could you assume there's a common ground, aka a self contained, common, ground (the conductive parts of the motorhome, and the frame)?

Morich · 06-23-2020, 03:35 PM

Can't think of anything that would not be common ground on RV. The auto portion is all grounded to the frame as well as all the RV parts I can think of.
I get this fro m Google on what equipment uses isolated ground:
The IG provides an insulated, separate ground path for the ground reference in electronic equipment, such as computers, hospital equipment, and audio equipment. IG does not break ground loops, which can damage equipment like computers, printers, etc..

But on the other hand we do know lots of folks who DO use some of that equipment on/in RV without any apparent problem. I would have to go with the folks who deal with the question all the time.

AJMike · 06-23-2020, 03:41 PM

Quote:

Originally Posted by Morich

Can't think of anything that would not be common ground on RV. The auto portion is all grounded to the frame as well as all the RV parts I can think of.
I get this fro m Google on what equipment uses isolated ground:
The IG provides an insulated, separate ground path for the ground reference in electronic equipment, such as computers, hospital equipment, and audio equipment. IG does not break ground loops, which can damage equipment like computers, printers, etc..

But on the other hand we do know lots of folks who DO use some of that equipment on/in RV without any apparent problem. I would have to go with the folks who deal with the question all the time.

The IG??? Installation Guide???

Morich · 06-23-2020, 04:58 PM

IG?
I thought Isolated ground? Internet info is not always as clear as needed. Seems like they think there is some kind of shortage in the alphabet!

What I get in that is the isolated ground would have an insulated ground wire which was not connected to the "normal" frame, etc like cars have. all I have seen in RV and cars is they do not use a second wire for ground but just go to the nearest metal of the frame which would NOT be isolated.
Seems like that means any isolated would require some sort of ground rod, etc which we know we don't have on RV. Only place I've seen isolated is in high power, high tech stuff like around microwave towers where signals tend to bleed over into other high tech stuff. Not too much of the real high tech stuff in our RV.

Jimm · 07-05-2020, 12:12 PM

Are you using this to charge off of the alternator? Non-isolated should be fine. If you ended up getting the isolated one you would find that you would be connecting both grounds to the same place anyway so isolated is not needed. Which unit are you looking at getting, the 12/12-30?

AJMike · 07-05-2020, 01:05 PM

Quote:

Originally Posted by Jimm

Are you using this to charge off of the alternator? Non-isolated should be fine. If you ended up getting the isolated one you would find that you would be connecting both grounds to the same place anyway so isolated is not needed. Which unit are you looking at getting, the 12/12-30?

Actually it is connected to the starter battery, not the alternator. That is what the installation called for.

My search for the proper Victron charger was due to issues I was having with the Renogy 40 amp DC-DC charger I had installed in my Fuse. The charger was overheating and switching off, and then back on, regularly and I worried about a failure of the device and any issues with the RV's electrical system that might occur. I had decided on the isolated model because I could pretty much just use the existing wiring with very little change, but before I did that I decided to see if I could somehow fix the Renogy charger I already had. Part of that decision came from the fact that no one had a Victron Orion-TR smart isolated 12/12/30 in stock and the wait was several weeks. I guess Victron is behind on its orders, probably due to the Caronavirus.

I am not someone who would be called "handy" so this was a big deal for me, but I managed to move the charger and its wiring from its previous location to a new location that provided more open space and so more room for the heat to dissipate. I then had 2 holes cut in the new cabinet location and installed a muffin fan in the new location and with the fan working the Renogy charger no longer overheats.

Given that it is now working and given that I can not get an isolated version of the Victron charger in any case, at least right now, I am going to see if the Renogy continues to function properly in its new and more airy location. If it fails I will try to get a Victron charger. It uses a large heat sink instead of a fan and thus may be better designed to shrug off any heat buildup.

orangeminnie · 07-08-2020, 05:58 PM

Either should work. Last I checked (earlier this year), many if not all of the non-isolated Victron DC to DC charger models were not shipping yet. I'm using an isolated model in a common-ground environment. The only problem I've seen, which is unrelated to the above, is that the 12/12/30 overheats very easily. The heat sink appears to be inadequate. It smoothly folds back the charging current to protect itself, however, without shutting down. I've added a computer fan above the heat sink, and will be installing much larger fans, soon. There is no way to manually dial back the charging current. IMHO, the Victron Orion should have been designed with internal fans, like the Renogy.

AJMike · 07-09-2020, 06:14 AM

Quote:

Originally Posted by orangeminnie

The only problem I've seen, which is unrelated to the above, is that the 12/12/30 overheats very easily. The heat sink appears to be inadequate. It smoothly folds back the charging current to protect itself, however, without shutting down. I've added a computer fan above the heat sink, and will be installing much larger fans, soon. There is no way to manually dial back the charging current. IMHO, the Victron Orion should have been designed with internal fans, like the Renogy.

I looked at the installation instructions for the Victron when I tried to buy one and saw that it is supposed to be installed with the heat sink fans vertical, I suppose so the heat can rise and allow them to cool, but I assumed it would be better with them horizontal and a small fan pushing air through them and out of the storage cabinet. But since I could not actually buy one of the isolated models I just installed a fan behind my Renogy charger and that seemed to take care of the problem. I guess heat is a big issue with these chargers.

I thought that the Victron would be a better bet since it uses a passive heat sink to dissipate the heat but if the heat sink is not large enough perhaps the fan is better. I just worried that the fan would fail and then there would be no built-in way to get rid of the heat.

jerichorick · 07-09-2020, 10:45 AM

Quote:

Originally Posted by AJMike

Victron makes both isolated and non-isolated DC-DC chargers for charging Lithium batteries. When I spoke with the sales guy at one of the solar stores that carries Victron equipment he said that the isolated chargers are for those applications where there is not a common ground and that it is not necessary for RV applications since they have a common ground. Unfortunately I don't really know if he is right and if my Winnebago Fuse uses a common ground or not. I suppose I don't have enough of an electrical background and am not sure what I could check with an ohm meter to tell if there was a common ground.

We are currently camping near Flagstaff where the store is located and I was thinking about picking up the Victron charger on our way home, but since they don't have the isolated version in stock my choices are to buy the non-isolated and hope it works or order online from someplace and pay shipping. Can anyone tell me if RVs use a common ground? I am pretty sure cars do but am not sure about RVs.

Thanks for any help.

I suggest contacting Justin at [email protected]. He is a great and knowledgeable guy.

NormD · 07-09-2020, 10:25 PM

I use an isolated ground charger in my boat to assure that shore power is isolated from the parts in the water, such as the propeller shaft. There is no reason to have an isolated ground in an RV. There is also risk in having separately grounded electrical systems.

jerichorick · 07-10-2020, 08:56 AM

Quote:

Originally Posted by AJMike

I looked at the installation instructions for the Victron when I tried to buy one and saw that it is supposed to be installed with the heat sink fans vertical, I suppose so the heat can rise and allow them to cool, but I assumed it would be better with them horizontal and a small fan pushing air through them and out of the storage cabinet. But since I could not actually buy one of the isolated models I just installed a fan behind my Renogy charger and that seemed to take care of the problem. I guess heat is a big issue with these chargers.

I thought that the Victron would be a better bet since it uses a passive heat sink to dissipate the heat but if the heat sink is not large enough perhaps the fan is better. I just worried that the fan would fail and then there would be no built-in way to get rid of the heat.

Are you charging from solar? DC-DC??

AJMike · 07-10-2020, 09:13 AM

Quote:

Originally Posted by jerichorick

Are you charging from solar? DC-DC??

Yes, and yes. It is a normal RV setup.

I have 3 100 watt solar panels on the roof charging the batteries through a Zamp solar controller, I have a Renogy DC-DC charger connected to the startup battery and the Lithium batteries and it charges when driving and I have a 2500 watt generator that also charges the batteries when it is running.

jerichorick · 07-11-2020, 09:16 AM

Quote:

Originally Posted by AJMike

Yes, and yes. It is a normal RV setup.

I have 3 100 watt solar panels on the roof charging the batteries through a Zamp solar controller, I have a Renogy DC-DC charger connected to the startup battery and the Lithium batteries and it charges when driving and I have a 2500 watt generator that also charges the batteries when it is running.

All "-" is common in a RV. Boats are a different animal and science. Everything eventually ends up grounded to the chassis. Are you using a battery management system? It is best to charge the start batteries and house batteries separately. A smart BMS will detect the bank needing charging and connect it. This isolates the types of loads also. Your 300W solar give you about 21A charging current. Common negative bus is not a problem. The Zamp and Renogy control the positive side.
Have you looked at this controller? https://www.zampsolar.com/30amp-dual-battery. It seems to do all you want.