Battery and Solar Disconnect Install Questions

[T-Oliver]

Cover was removed to read the ANL fuse

It’s certainly excellent advice to be aware of the potential hazards of grounding to the insulation 

[jd1923]

12 hours ago, Geronimo John said:

The Solar Disconnect (DISCO) only needs to handle the power of the solar panels.  Likely 200 to 600 watts.  The Battery disco needs to be able to handle 350 Amps at say 12.7V which is 4500 watts.

For the main battery fuse, check your inverter spec. OTT had a 250A ANL fuse installed in our hull for the 2KW Xantrex that was our original system. When I upgraded to the Victron Multiplus II 3KVA Inverter-Charger the manual stated using a 400A fuse. Most applicable inverter specs will be in the range is 250-400A.

When choosing a cut-off switch, it should be rated equal to or above the proper fuse rating. Most go with the available Blu Sea 300A or 350A rated switches.

For your solar, use what is specified for the solar charger. Or if your MPPT Solar charger is rated for 30A, then a 35A or 40A breaker or fuse is appropriate. Our Blue Sky SC is rated for 25A and OTT installed a 30A breaker. When I added a Victron 30A MPPT SC, I believe the book said 35-40A and I installed a 35A breaker.

So not to get shock while working with battery cables ---
It is common practice when installing battery cables is to install the B+ side first since when the ground is not connected, the B+ side has no potential. When removing battery cables, use the reverse order, remove the B- side first.

This is why in my battery installation, I positioned the main B- battery closest to the door. This way I can remove the ground (vs. having a switch) even without sliding the tray open and the closest B+ connection is 8" deeper into the battery bay, providing a very low chance of touching it by accident. 

[Geronimo John]

7 hours ago, T-Oliver said:

Cover was removed to read the ANL fuse

It’s certainly excellent advice to be aware of the potential hazards of grounding to the insulation 

😊   😊  😊

GJ

[Geronimo John]

3 hours ago, jd1923 said:

For the main battery fuse, check your inverter spec. OTT had a 250A ANL fuse installed in our hull for the 2KW Xantrex that was our original system. When I upgraded to the Victron Multiplus II 3KVA Inverter-Charger the manual stated using a 400A fuse. Most applicable inverter specs will be in the range is 250-400A.

Good safety tip JD.  For our replacement 3,000 watt inverter I was able to reuse the OTT OEM 300 Amp for the protection of the 4/0 cables that feed the Inverter.  In all three cases the fuse protects cables not attached loads.  The inverters self protect if you overload them.  But if your cables are too small they become a problem.  Especially if your OEM cables were sized for 250 amps with a 400 amp fuse.  So, in addition to checking the inverter manual for fuse size, VERIFY your cables are rated for the fuse size as well.

 

3 hours ago, jd1923 said:

When choosing a cut-off switch, it should be rated equal to or above the proper fuse rating. Most go with the available Blu Sea 300A or 350A rated switches

Ditto.  I suggest that if you are installing such a safety switch, that for the minor cost difference, get the 350 amp Blue Sea switch.  That way when you upgrade to the 3,000 watt inverter you don't also have to upgrade the switch too.  Why?  The switch must always be rated higher than the fuse protecting the wires.

3 hours ago, jd1923 said:

This is why in my battery installation, I positioned the main B- battery closest to the door. This way I can remove the ground (vs. having a switch) even without sliding the tray open and the closest B+ connection is 8" deeper into the battery bay, providing a very low chance of touching it by accident. 

I wish that I had thought of that one two years ago!  

3 hours ago, jd1923 said:

So not to get shocked while working with battery cables ---
It is common practice when installing battery cables is to install the B+ side first since when the ground is not connected, the B+ side has no potential. When removing battery cables, use the reverse order, remove the B- side first.

Great reminder as well!

GJ

[Snackchaser]

19 hours ago, jdmmtx said:

Can someone please educate us on why one would choose a solar disconnect versus a battery disconnect and why you wouldn't have both? Is the solar disconnect primarily a safety feature? We do understand a battery disconnect is used to eliminate parasitic draws during periods of storage. We currently have neither in our 2019 LEII and are wondering about having one or both installed.

@jdmmtx, I'll try to explain it better if I can.  

First of all, I didn't install my solar switch as was suggested, it was installed by Oliver during manufacturing.  There were NEC and local codes that required solar switches, but i don't know where that stands now or why Oliver apparently stopped installing them.   Regardless, it’s still a reasonable safety feature, because with no sun the system can test completely dead.  Then surprise when the sun comes out!  The solar wire is not as obvious, or as easy to find and disconnect as the battery, so a switch is a good idea and easy to install.  Also, it’s nice to be able to switch off the solar to avoid low voltage warnings such as @Tony and Rhonda  were experiencing when they started this thread.  But I wouldn't worry a second if I did't have one!

The battery is more straight forward.  A switch wasn't required by code, and the manufacture didn’t install one.  A switch isn’t needed for modifications because it’s best to disconnect the battery.  There are few credible or realistic scenarios where a battery switch would prevent disaster.  The most persuasive reason is to disconnect the parasite loads during storage as you stated.  But you can do that without a battery switch as I’ve previously explained, and you won’t be inadvertently de-energizing the emergency breakaway brakes… which is a code violation.

Yet there is nothing wrong with adding a main battery switch if you want to.  Just don’t be coerced into it by safety concerns, and make sure you maintain “un-switched” constant power to the breakaway brakes.  Also understand and consider what safety features already exist in your trailer.  For example; my Lithionics BMS has short circuit protection, overcurrent shutoff, high voltage, etc..  The batteries also have power switches that disconnect power to the terminals, and there is a 300 amp breaker already in the battery circuit.  Adding a battery switch would be totally redundant and completely un-necessary!  Oliver and their liability insurance obviously knew that too!

I hope this will help folks be better informed to make the right decision for themselves.  Cheers, Geoff

[rich.dev]

1 hour ago, Snackchaser said:

First of all, I didn't install my solar switch as was suggested, it was installed by Oliver during manufacturing.  There were NEC and local codes that required solar switches, but i don't know where that stands now or why Oliver apparently stopped installing them.

On our 2023 we have a solar disconnect switch in the cubby above the street side bed.

[jd1923]

11 minutes ago, rich.dev said:

On our 2023 we have a solar disconnect switch in the cubby above the street side bed.

Sorry, I assumed Geoff installed his since he suggested adding the switch with installation instructions. It read to me like he had added his, my mistake. So now we see Rich has the same on a much newer hull. Who knows why OTT stopped switching the SC on hull #251 and perhaps others of that era! ?

[jd1923]

2 hours ago, Geronimo John said:

the fuse protects cables not attached loads.  The inverters self protect if you overload them.

True, but you need to size wire AWG and the fuse rating based on load requirements.

The single largest load in a 12V RV system is the inverter, given you have one. And inverters have overload protection and so do modern LiFePO4 batteries and either can fail, so we use fuses or circuit breakers.

From the examples I've seen, OTT installs 4/0 battery cables whenever they install an inverter. This is more cable than you need, over-engineered. There are so many wire gauge charts but I like this one since it covers short wire lengths. Although I do not know the source of this tables, the numbers seem to make sense.

When I pulled the original 4/0 cables in our hull, cleaned them up and reused them for new batteries and the larger capacity Victron inverter, I noted each cable was less than 5 ft long. Based on this table, B+ plus B- lengths of 4/0 cable adding up to 10 ft can safely carry 600A. Victron specified a 400A fuse for their product which also has a built-in safety factor. They spec'd 400A,so that is what I installed.

There is another conclusion you can make from reading the data in this table. If the 250A fuse was all that was required in the 2KW Xantrex inverter that was originally installed in our hull (and others as the example pictured above), OTT could have installed 1/0 wire which can handle 250A up to 12 ft long.

[Geronimo John]

19 hours ago, Geronimo John said:

Battery and Solar Disconnect Install Questions

But be sure to know that they are two different things with two different purposes located in two different parts of the Ollie.

The Solar Disconnect (DISCO) only needs to handle the power of the solar panels.  Likely 200 to 600 watts.  The Battery disco needs to be able to handle 350 Amps at say 12.7V which is 4500 watts.  

The Solar disco can be less easy to get to.  Generally, it is used for maintenance and storage purposes.  But the Battery disco needs to be where you or a first responder can get to it in a dire emergency fast. 

So why did I calculate the above power potentials?   Certainly not to coerce anybody to do anything.  But to inform of the power potentials that we need to be aware of.  Yes, to me the primary purpose of having a battery AND a solar discos are (#1) maintenance and (#2) emergency use.  

#1 MAINTENANCE SAFETY & CONVENIENCE: 

When we are doing maintenance on our Ollies that in any way involve electrical it is important to disable ALL power sources that can bite us.  Certainly 120V shore and Inverter power sources, as well as battery and solar.  Why all?  Because each trailer has systems that interconnect between them.  Examples:  (Inverter, Converter, Refrigerators, computer power ports, etc.  As stated above the are many ways that a simple mistake during a simple maintenance task that can, and likely have happened as a result of not thinking about all the potential issues that can happen.  Such as the importance of covers high amperage fuses and foil insulation as mentioned above.  If you don't have the necessary disco's and don't have the background experience in such systems to safely disco hot circuits safely work you really need the discos. With the disco's you just need to:

• Turn off a 350 A battery switch
• Flip a solar breaker
• Physically verify your Ollie is not plugged into shore power (Generator, Power Pole, Outlet).

Or you could disassemble at least three HOT cables to do your 5 minute maintenance task. I guarantee you that at some point in doing so, you will realize that the minor cost of installing those power Disco's is far more cost effective than your time to Disco and restore all sources of power when working on your electrical and mechanical systems.  

Finally on this point, I consider end of season parasitic loss elimination and power source isolations just another maintenance task that is a lot easier with such switches.  

#2 EMERGENCY USE:  

If you are handy and you smell a major electrical acrid burning smell, it is possible that you could flip the power panel 30 amp breaker, disco the Solar wire, inverter power source, and unplug the shore power and disco the batteries.  Then figure out what was causing a major smoking.  

But what if you are out fishing/hiking/or flying hang gliders;  Are your guests capable of doing the above?  Not likely for most owners.  For the vast majority of spouses or guests, they should exit the trailer and call 911 or summon help.  Either way, they get to watch what happens next from a safe distance.  Most important part is they are safe.   

On the other hand if you or they feel it is safe to do so:  Turn off the Battery Master Switch and Solar breaker, and unplug the exterior power port. Air out the trailer and then figure what was burning.....

IN SUMMARY: 

Our OTT electrical and mechanical systems are exceptionally well designed and carefully manufactured.  Over time their systems age very well compared to the SOB's.  As a result we don't see many of our OTT units burning to the ground.  But fires do happen and to me, having basic measures in place make sense as the cost could be so very high if you don't. 

MANY owners, especially the Master Level Contributors, are fully capable of doing significant DIY efforts.  Everything from A/C and Refrigerator replacements DC to DC chargers, transition to Lithium, adding solar, springs, axles. hitches, fans and other really great projects.  We take great pride in helping other owners to join the DIY group.  But first start with a DEEP dive in this forum on the topic.  Take pictures of your system and download the posts and pictures of others who have done the effort.  You than can intelligently talk to OTT or other qualified firms to have the mod done.  Or, to start asking question and help on our forum if you want to DIY it.  Our owners are scattered out all across the USA.  Likely one will be in your location or willing to meet should the paths cross during the season.  

GJ

Edited 7 hours ago by Geronimo John