Planning DC charging upgrades- solar and DC-DC

Maxcamp8 · March 16

All, I appreciate your generous contributions of thought and time into providing insights and advice. Very helpful indeed.

Yes, batteries are wired in parallel (double amperage not double voltage.) I agree the four battery terminal breakers and DC busbars obscure this fact to some extent.

Yes, I do not need the two 50a BlueSea breakers on the negative battery terminals. I am choosing to install them as an OFF switch to isolate each battery for both winter storage and very occasional single-battery charging and balancing, as Battleborn recommends.

Yes, I do not need the inline negative fuse on the T.V. charging input. it seemed like an added safety given wires under TV, under Tab, and in battery bay could be subject to physical damage from below or from equipment/load shifts upon driving over a big pothole. It’s happened.

I have a rotary On/Off switch inline between DC terminal strips and the Wefco/PD converter 12v loads. Need to add that to the drawing. Thank you for pointing out its omission.

Drawing shows 2/0 from DC busbars back to the PD. This is wrong, has been no.10 but plan to use my extra from spool of no.6 to expedite Wefco/PD charging back to battery. This circuit run is about 14 feet through the cabinetry.

The recommended Battery Isolator between TV and DC-DC converter monitors and prevents TV battery drawdown, when ignition is off or when TV charging is below a certain threshold. This way we can stay hooked up during stops. Often the isolator is wired within the TV engine compartment, but can be wired close to the batteries as I and many others have done.

In discussion, Battleborn recommended the 30a not 40a DC converter, based on 135a TV alternator, 40 ft wiring distance, and 100a Battleborns.
The 40A inline breakers under the TV hood probably should be the 60a to 75a size that @tungsten and @VonAustria refer to. Will find out in a hurry!

Should I keep or omit the T fuse on the Inverter negative lead from batteries?
Inverter T fuses will be about 14" from the two terminal strips which in turn are 14" from the battery terminals. I hope to complete the inverter wiring today and test with plug-in microwave load to see whether the 50A inline breakers from the batteries trip. If so I will need to rewire the Inverter directly to the battery system, bypassing the inline breakers idea. I have a soft start on the Air8.

The Inverter is 3000 watt. A 2000 watt should suffice for either the Air8 air conditioner load or the higher Microwave load. I made up a spreadsheet budget of amperage and wattage draws and per discussion with Battleborn they recommended the larger 3000w inverter to handle concurrency of medical heating pad, ventilation fans, fridge, water pump, and lights.

We will see if two batteries suffice to microwave lunch or briefly cool the camper while en-route and able to recharge while driving. They are certainly not sufficient to run the AC all night which is not something we really need anyway. Future plans include upgrade from two to four batteries.

The plug-in Victron charger has what looks like lampcord on the output side. I labeled it 14awg but don't really know the gauge. It is only used pre-trip to bring individual batteries to 100% SOC and balancing. It should become redundant in the future. Battleborn tells me it puts out 30A to charge batteries, whereas the PD4135 converter can output 55A (This confuses me since the PD4135 main breaker is 30a) and *should* charge more quickly... if I upgrade from the no.10 current wiring. We also use the victron charger with our ebike battery and farm equipment starter batteries.

Again, thank you for your thoughts and please continue to provide feedback.

elbolillo · March 16

@Maxcamp8 Wouldn’t an isolated DC to DC charger like the Orion-Tr Smart DC-DC Charger Isolate, do the same as the Battery Isolator? Reading the manual, it appears that it would

Yoshi_TAB · March 16

Hi,

Because I'm curious, your picture showed a 2000W inverter..that is why I asked.

Your loads make sense with the 3000W.

My 2000W inverter has no problem running the microwave to reheat a meal or heat water. We also use a 1500W water kettle to heat water when it's too cold out or raining to fire up the outside stove. I've only run the Air 8 a couple of times just to see what amps/wattage is pulled. It has no issue starting or running for a bit. Will be curious of your results. As they say..mileage may vary. Good luck with the rest of your install.

rfuss928 · March 17

elbolillo said:

rfuss928 said:

Maxcamp8
It concerns me that the three folks that chose to offer detailed critique of your wiring diagram so far cannot see that the batteries are clearly shown wired in parallel. I would look elsewhere for electrical advise...

Wired in parallel in a way that is not so common, so yeah, we missed it. Would you have any constructive thoughts on the OP’s wiring diagram that could be of use to all here on the forum?

I follow most of the electrical posts watching out for blatant errors and unsafe situations. I have life long professional experience with designing, building and evaluating automotive DC electrical components and systems. I choose not to comment on system design or component choices as those are generally opinions based on personal desires, preferences and existing equipment.
I don't see anything faulty or dangerous in the OP's design. I am concerned when folks that erroneously interpret a simple electrical schematic are advising others how a system should be designed and constructed. I believe that warning is constructive.

Maxcamp8 · March 17

@rfuss928, thank you for looking over these posts. Glad to know I'm not unsafe. Maybe some dumb design choices that I'll freely admit are based on a desire to mitigate risks, rather than sound engineering. The AC brown outs, reversed and hot wires, and issues with shore power sites are alarming. DC Shorts on my trucks over some 50 years have been frustrating and often relate to hidden wire chafing or unintended later rewire changes by others*. I envision how easy it would be for a return wire or the grounding frame to go hot someday. Without a sound education in DC power I've embarked on an expensive and rather confusing process. I'll take all the help I can get!

*(Cap World crossed different return wire circuits and burnt out three expensive trailer light converters. Full rewire by me found and fixed issue.)

elbolillo · March 17

rfuss928 said:

elbolillo said:

rfuss928 said:

Maxcamp8
It concerns me that the three folks that chose to offer detailed critique of your wiring diagram so far cannot see that the batteries are clearly shown wired in parallel. I would look elsewhere for electrical advise...

Wired in parallel in a way that is not so common, so yeah, we missed it. Would you have any constructive thoughts on the OP’s wiring diagram that could be of use to all here on the forum?

I follow most of the electrical posts watching out for blatant errors and unsafe situations. I have life long professional experience with designing, building and evaluating automotive DC electrical components and systems. I choose not to comment on system design or component choices as those are generally opinions based on personal desires, preferences and existing equipment.
I don't see anything faulty or dangerous in the OP's design. I am concerned when folks that erroneously interpret a simple electrical schematic are advising others how a system should be designed and constructed. I believe that warning is constructive.

Thank you!

Maxcamp8 · March 18

Success with the Inverter. Wiring the DC input to the 2000w inverter (Amazon damaged the 3000 I ordered the 2K) inline after the 50A battery post breakers is not an issue. Ammeter shows low DC amperage pull when running 120v microwave. Ran the microwave for 15 minutes and monitored DC wire and battery temps with infrarred thermometer. A two to four deg F rise in temp from ambient on the last 2/0 awg wire, mostly at the 225A T-fuse. No other wires showed temperature increase. Battery voltage declined promptly from 13.3V to 12.5V, and rebounded to 13.1V upon microwave shutoff. Ran this test twice. The inverter cooling fans did not turn on until partway into the second test. No detectable heat.

Hardwiring the 2000w Rhenology inverter output to a manual transfer switch using 10/2 Romex. I am very disappointed with Rhenology- the three output screw terminals are a wildly undersized #4 screw 3/8" long and a miniature flat square wire retention plate. They like to jump and hide. The opening are too small for a ring terminal. There is no strain relief device to prevent conductor pull-out.
I am going to have to innovate something, probably pull the end plate off the inverter and bolt something in place from behind.

Rhenology manual says to use these screws rather than one of the three duplex outlets, the screws are reated for "greater than 15A draw" versus 15A lmit on the duplexes. The PD4135/Wefco has a 30A primary fuse so I am using 30A wire. May have to repull with stranded cable to limit strain on connection.

Voltmeter on output with no load reads 119.3v, not 120.0 volts. Why is that.

Image: https://us.v-cdn.net/5021717/uploads/editor/9s/ylu65rcvt7oa.jpg

SLJ · March 19

rfuss928 said:

Maxcamp8
It concerns me that the three folks that chose to offer detailed critique of your wiring diagram so far cannot see that the batteries are clearly shown wired in parallel. I would look elsewhere for electrical advise...

You obviously have not looked at the original diagram the OP posted which is what I commented on and there are different ways to wire batteries in parallel. Depending on length and gauge the top diagram is preferred for longer and smaller gauge wire.

Image: https://us.v-cdn.net/5021717/uploads/editor/c7/brtyjl8992g1.jpg

Image: https://us.v-cdn.net/5021717/uploads/editor/j9/etk5ufrx9toe.jpg

rfuss928 · March 20

Maxcamp8
Very nice layout and construction.
In your photo above there does not appear to be any connection to the second lug of the Smart Shunt (BVM)?
For accurate measurement of battery usage, all ground connections must be connected to the service side of the shunt and only the battery grounds to the other lug. That is not clear in you schematic or the photo.

Maxcamp8 · March 20

Yes, working on connections from battery compartment to wefco compartment. Not there yet.

Inverter lacks strain relief. Fabricated strain clamp.

Routed cabs for 3way 120v single pole transfer switch and 2way 12v single pole cutoff switch. Made up necessary backbox and cover plate for mounting. Both switches recessed to reduce foot strikes.

Tape and paper openings, and tape a disposable tupperware box over inside of hole, to contain router dust.

rfuss928 · March 22

Maxcamp8
Based on the last wiring diagram you posted (copied below) and some considerations I'm making for my own dual battery circuit breaker wiring.

Considering the multiple circuit breakers on your batteries:

The breakers in series with each of your batteries will limit the current on that branch to 50 amps when one or the other trips dependent on the tolerances of each of that pair. Redundant protection and convenient isolation switches. No issue.

The breakers on each battery branch are in parallel like the batteries and will require 50 amps in each circuit (100 amps total) to trip when both battery circuits are ON. As you approach that limit slight differences will cause one of the battery circuits to trip first then all the load goes to the remaining circuit which will likely quickly trip trying to carry the entire load. Because both breakers must trip to completely disconnect the source. All wiring in circuits connected to the to the bus bars or chassis should be 100 amp rated or fused separately. Safety may be compromised.

Other observations:

On your inverter, the input current will be limited by the 50 or 100 amp parallel limits of your battery wiring as described above. 2000 watts will require nearly 200 amps.

The ground connections for your TV and power center should be to the chassis ground (not the bus bar) to be measured by the shunt.

Very nice construction details and workmanship on your installation. Thanks for sharing.
Have fun!
Bob

elbolillo · March 23

Actually, the diagram is missing quite a few details. Not only should the negative from the inverter be connected to the load side of the shunt, but also the negatives from the solar chargers and portable battery chargers. These are missing on the drawing.

Maxcamp8 · March 28

I ran the negative returns through the BMV monitor. Not a draftsman, yes the sketches are incomplete. Comments have been useful.

Just finished an electrical upgrade including 2000w inverter from our existing 200ah of batteries; DC to DC charger from truck; 200w suitcase solar; and a lot of rewiring. Everything is in, working, and stress tested. Terminals are torqued and insulated.

Initial tests in yard and of highway charging show we should meet our power and recharge goals, having upgraded with DC to DC charger from truck and added suitcase solar. 12v draw using a clamp DC ammeter:

Inverter at rest- 1.1A without cooling fans; 1.3A to 1.6A with.

Sunbeam heating pad- 9A or less, used for several hours. While our earlier clamp-on 750w inverter drew slightly less, decided to keep it simple and not add it to the mix.

Microwave- 91A- will be used for under 15 minutes at a time

Air8 AC on fan only- 11.8A

Air AC with compressor on- 60.2A- will be used to cool down 75+F interior for 1/2 hour when needed at stops.
We do not travel in hot weather, this is for swing seasons.

I used an infrared heat gun to monitor temps of wires, busses, equipment, and fuses.
Only the microwave generated a noticeable temp rise of well under 10 deg F after 30 minutes at the 225A fuse, and 2-3 deg F elsewhere.

See separate posting about safety issue with one piece of equipment as sent from manufacturer!

Maxcamp8 · March 29

I would like to swap out the remote on/off switch on the inverter for a spring-wound timer like this:

https://www.amazon.com/BN-LINK-60-Minute-Countdown-Mechanical-bathroom/dp/B01LVTGKBR
I would set it for around 20 minutes. While 120v rated, it should be usable to switch off a 12v system just fine as it does not use power in moving the manual spring wound timer.... I think.

The trick will be finding one that is not noisy as my ears ring. May have to go with the relay idea below.

The Renogy 2000w inverter has a remote on/off switch conected by what looks like a CAT5 cord which I can cut and splice into. Searching the internet, Most 12v Digital timers require digital programming and would be a pain to use each time. There are 12v Din-mount Relays that can be pre-set to a shutoff interval and mounted in the battery compartment, but seems quite complicated to figure out.

I have written Renogy to inquire if there are voltage and resistance requirements on their remote.
No info in the manual that I can find.
www.renogy.com/content/files/Manuals/RNG-INVT-700%261000%262000%263000-12V-P2%20Manual.pdf

Maxcamp8 · April 9

Here is the interior of the Renogy remote. More going on than just on and off.
While I could cut one wire on the switch (blue, left) and wire in yet another backbox for a spring-wound timer, that gets more complicated and takes more wall space. Pass for now.
It might be possible to fit some kind of miniature electronic timer/relay into this box or move this circuitry to a deeper box. Not my forte.

Image: https://us.v-cdn.net/5021717/uploads/editor/s0/s7tgesavn8n2.jpg

Maxcamp8 · April 14

Suitcase solar port and MPPT 100/30 charger install:

Image: https://us.v-cdn.net/5021717/uploads/editor/ak/zmb0dw6qa52c.jpg

Router template for charge port penetration of sidewall in driver wheelwell.

Image: https://us.v-cdn.net/5021717/uploads/editor/5f/mx3ysgquxpef.jpg

Had to temporarily remove plastic fender for room to swing router. Caulked screwholes (Nucamp used putty tape which was failing.)

Made up 1/8"d wire rope as Messenger Cable/Theft Deterrant for solar panel.
Swedged connections. Loose 8awg cables and 1/8" messenger bound with Harness Tape @6" intervals.
Coil stored in "suitcase solar". Panel is 48 lbs, plus cable weight. Going to transport standing vertical against rear seatbacks in double cab truck, with two flat webbing buckled straps to retain, and 1/4" masonite protection in front.

Image: https://us.v-cdn.net/5021717/uploads/editor/b3/0p9uhpr2h60i.jpg

Mounted charger in driver wheelwell, a tight fit vertically.

Pleased with solar suitcase, 10A charging in sunshine for four hours will offset expected evening use of 2000w Inverter for an hour or so.

Surprise surprise! MPPT 100/30 has a phantom draw of about 0.06 amps in the dark/rain, whereas the existing MPPT30 has little to none. For now am just pulling the inline fuse for the long periods we are not going to use this panel, but will probably add yet another kill switch later. Can also shut Charging to OFF via Victron cell phone app.

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