Beginner Designing questions: converting Truck Camper to Solar/LiFePO4

[jungry]

Hello everyone,

I hope I'm not missing another thread with all the info I'm seeking here, I couldn't find it. I have a truck camper that has existing 12v SLA and no solar panels, there is an outlet on top of my roof which i think is a pre wire for panels. The existing system only powers the 12v and I must plug into shore power for AC power. There is a microwave and air conditioner that I would like to power with the batteries in the future system.

I have purchased a Renogy DCC50S, MPPT/alternator charger, for an upcoming vacation. My plan is to upgrade the entire system eventually. I would like to save as much money on the system as possible.

*Main Question: I am trying to figure out if its possible for me to use the existing transfer switch and simply wire in a large basic inverter to go with my two custom built 12v LiFePO 280 aH batteries, versus simply buying either a Victron Multi-plus inverter charger or Xantrex (I've heard that they sometimes have problems). I was considering 3000 watts or 2000watts because I think with the air conditioner running it would be around 1900 watts. I was considering the Renogy 3000 watt basic inverter and wiring it into my existing fuse panel to power my 110 volt outlets, microwave and air conditioner, is this possible and practical? or should i just use something like the Victron multi-plus 3000 watt system?

I have seen a few videos on people adapting their existing shore power chargers to their new lithium batteries and I am concerned about protecting my system with the transfer switch. I don't want to fry my new system.

The future battery bank will be two 12 volt Lishen cell, 280 aH batteries, and three 200 volt Rich Solar panels feeding the Renogy DCC50S. I am considering getting a higher voltage MPPT because the Renogy DCC50S is limited to 25 volts.

 

[jungry]

Ok...

So I just took apart a bunch of panels and I'm pretty sure I have determined that I do not have a transfer switch, the AC simply charges the 12volt battery via the converter and it also powers the refrigerator and air conditioner separately.

So, I would need to buy either a transfer switch and connect it between the converter or install an expensive all in one system like the Victron multi-plus or equivalent.

But...who out there has had experience with simply using the AC output terminals on a pure sine wave inverter and sent that power to a transfer switch that alternates between shore power and their outlets and appliances?

 

[Bob B]

I have a 30A power cord in for truck camper. If I want to run the camper on the generator, I have to plug that power cord into a female 30A "outlet" that supplies generator power from the onboard generator ..... I am going to do the same with the inverter I added to the system.

Yeah, a little inconvenient, but I don't plan to have to switch back and forth that often. If it gets to be too much of a hassle I will automate it.

I will also have to turn off the converter when running from the inverter.

 

[HRTKD]

Truck campers (aka slide-in camper) have very limited roof real estate for solar. Consequently, trying to run air conditioning with just roof PV and batteries won't last long. Of course, this depends on the size of the camper and how creative you are with the space available.

You can supplement the roof PV with ground deployed PV. Panels you put on the ground and tilt to meet the sun have the potential to generate more watts than the roof PV.

 

[jungry]

I think I've got the solar array figured out, I am wondering how to wire together a transfer switch with the inverter and solar MPPT/dc-dc charger.

Or if its simply way better to just spend the money on a higher end all in one inverter like the aforementioned Xantrex or Victron combo.

 

[Cdkipp]

(1) Many (at a somewhat lower cost) inverters besides Victron contain internal transfer switches. A 30 amp transfer switch is relatively speaking not that expensive so I do not see that as an obstacle and you can always manually change plugs as described above. (2) You mention your converter but none of the details. If you are only going to charge your batteries from your alternator and solar then just disconnect the converter. However, that would be highly unusual to not have the capability of charging your batteries from shore power (or generator) supplied AC. This is the exact issue that drives most people utilizing LiFePo4 DIY packs to higher-end components like Victron, Magnum etc. A standard lead-acid charger converter can't do it and these high-end brands give you the ability to user adjust the parameters for your lithium pack. Since you need that level of charger, and you also will be buying an inverter, buying a combined inverter/charger with built-in transfer switch and user adjustability makes all kinds of sense. This set up would then work with your renogy and give you all you need. (3). Number #2 would be my standard advice but given recent developments and the fact you are using a truck camper where space is a premium, I would take a very long hard look at the new all in one units particularly the Growatt 3000 from Signature Solar and the similar MPP units Will has reviewed available from many sources. These units get you a solar charger, transfer switch, ac battery charger and inverter with user-adjustable parameters at a MUCH lower cost than the approach I describe in Number 2 with much less weight, size and wiring requirements. It is easy. In this scenario, you would want probably not want to use the renogy for solar and let the all in one handle everything except charging the alternator. The only other components I would add would be your lifepo4 pack BMS and the Victron Smart Shunt.

 

[Cdkipp]

I think I've got the solar array figured out, I am wondering how to wire together a transfer switch with the inverter and solar MPPT/dc-dc charger.

Or if its simply way better to just spend the money on a higher end all in one inverter like the aforementioned Xantrex or Victron combo.

I will just add that I have a 40 foot fifth wheel I full time in with two DIY Lifepo4 packs (one 24 volt and one 12 volt) with a large solar array and two Magnum inverter chargers. So I know the benefits of the big stuff. But for more remote journeys we have just purchased a lance 1575 travel trailer and for that small space and weight limitations, I am strongly considering approach 3. The only issue I have is the long term reliability of these all in one units. However, they have been out a few years now, word of mouth is good, and I could buy about four of them if I tried to match them with the approach I described in Number #2

 

[corporate.joe]

Truck campers (aka slide-in camper) have very limited roof real estate for solar. Consequently, trying to run air conditioning with just roof PV and batteries won't last long. Of course, this depends on the size of the camper and how creative you are with the space available.

You can supplement the roof PV with ground deployed PV. Panels you put on the ground and tilt to meet the sun have the potential to generate more watts than the roof PV.

Similar to what would be needed on a roof the size of a truck camper.

 

[jungry]

Dhasper,

Thanks for the information, I have a Progressive Dynamics Mighty Mini AC/DC panel and converter/smart charger- 45amp. It came with the camper. From what I have read, it should charge lithium batteries. I definitely want to be able to charge with the converter as my battery bank will be 6720 watt hours and the solar array will only be 600 watts.

So if I was too wire the DCC50S directly to the batteries and say a 3000 watt pure sine wave inverter to the a "Go Power" transfer switch in-between the shore power and the inverter it would work? Of course I guess that depends on my skill connecting everything.

One question I have is, when connected to shore power and the sun is shining on my PV array and the MPPT is charging the bank in addition to the converter, will there be any problems? Or will my BMS simply manages it all?

Also, if I have two 12 volt batteries wired in parallel what amp rating for the BMS? If I'm running the air con and making coffee do I need dual 250 amp BMS's or will two 120 amp units suffice?

 

[HRTKD]

Multiple charge sources is usually ok. Using a Victron Multiplus (or any inverter/charger with a shore power input) solves the problem of having the charger in the AC loop.

The DCC50S is very limiting. Be sure you read all the specs, especially the PV input volts, before you commit to it.

 

[Cdkipp]

Dhasper,

Thanks for the information, I have a Progressive Dynamics Mighty Mini AC/DC panel and converter/smart charger- 45amp. It came with the camper. From what I have read, it should charge lithium batteries. I definitely want to be able to charge with the converter as my battery bank will be 6720 watt hours and the solar array will only be 600 watts.

So if I was too wire the DCC50S directly to the batteries and say a 3000 watt pure sine wave inverter to the a "Go Power" transfer switch in-between the shore power and the inverter it would work? Of course I guess that depends on my skill connecting everything.

One question I have is, when connected to shore power and the sun is shining on my PV array and the MPPT is charging the bank in addition to the converter, will there be any problems? Or will my BMS simply manages it all?

Also, if I have two 12 volt batteries wired in parallel what amp rating for the BMS? If I'm running the air con and making coffee do I need dual 250 amp BMS's or will two 120 amp units suffice?

Yes that should work. This is where the BMS's get to be a real pain in the ass though. For a 3000 watt inverter the BMS you should have a 250 amp BMS. It sounds like people are having good success with two 120 amp parallel packs so that should work for you. With regard to your charging question, the controller and charger should both be able to charge and sort that out between themselves. Be sure to look at the specs for the rating on your BMS for charging though as they are sometimes rated lower on the charging side.

 

[Whinny]

You don't need a GoPower transfer, you can use any brand you want. The trick is disconnecting the charge function of the converter when running on the inverter. You can do that manually as well. If you want to run air conditioning you should think of low freq inverters-they handle inrush current much better than HF inverters do-or get a good soft start for your air. You are limited to 12v (18ish voc) type panels with the Renogy controller-but thats not a big concern-just keep an eye on the voltage of the panels you purchase. You may have to increase wire size from the panels to controller if sticking to that MPPT device.

 

[jungry]

So for the BMS, I attempted to order two from Overkill Solar, but my bank placed a lock on my cc when I tried to order the Lishen cells from Aliexpress, I guess the overseas charge made them suspicious. For some reason, since that one attempt, Overkill solar has locked me out of ordering now that the hold is off. They also emailed me after I sent them a message about being locked out. I got an auto reply saying that ever since Will Prowse recommended their product they are backlogged for months.

1.So I am considering other BMS's. Any suggestions?

2.Also, If I did get the expensive inverter/transfer switch combo can someone give me an example of what would make the extra money on a unit combo inverter better? easier install? more efficient? able to combine batteries and grid power while plugged into shore power?

What I'll be using the camper for 90% of the time is sleeping inside of during the day at work unplugged from shore power two days in a row, it's rarely hot here. I live on the coast and it might hit mid nineties for 2-3 weeks a summer. And 2-3 times a year we'll take family vacations to Baja (winter) and inner mountain USA for max 2 weeks. Freezing conditions will be likely encountered regularly so Ill have to either build a heater system into the battery chamber and or get a BMS with low temperature protection.

Again, thanks for all the input.

 

[HRTKD]

So for the BMS, I attempted to order two from Overkill Solar, but my bank placed a lock on my cc when I tried to order the Lishen cells from Aliexpress, I guess the overseas charge made them suspicious. For some reason, since that one attempt, Overkill solar has locked me out of ordering now that the hold is off. They also emailed me after I sent them a message about being locked out. I got an auto reply saying that ever since Will Prowse recommended their product they are backlogged for months.

1.So I am considering other BMS's. Any suggestions?

2.Also, If I did get the expensive inverter/transfer switch combo can someone give me an example of what would make the extra money on a unit combo inverter better? easier install? more efficient? able to combine batteries and grid power while plugged into shore power?

What I'll be using the camper for 90% of the time is sleeping inside of during the day at work unplugged from shore power two days in a row, it's rarely hot here. I live on the coast and it might hit mid nineties for 2-3 weeks a summer. And 2-3 times a year we'll take family vacations to Baja (winter) and inner mountain USA for max 2 weeks. Freezing conditions will be likely encountered regularly so Ill have to either build a heater system into the battery chamber and or get a BMS with low temperature protection.

Again, thanks for all the input.

Get on the list for the Overkill BMS if you can. Your cells will take up to 60 days to get here anyhow.

 

[jungry]

HA!

I found this:

He has so many videos its hard to find them all!

 

[jungry]

Ok, another question...

What size transfer switch?

I just bought a 3000 watt inverter, I have a 15-17 amp air conditioner, a microwave, a refrigerator, and I plan on building a small AC desalinator/watermaker and I plan on plugging in my cuisinart extreme brew coffee maker soon...

 

[jungry]

thanks for all your input, it really helps, my inverter is low frequency, that'll be key for the water maker and I can run saws and stuff.

 

[Zwy]

This project might be better with 24V considering all the items you seem to want to run. I went 24V with a Growatt 24V SPF 3000TL LVM. It has the auto transfer switch, 3K inverter, charge controller and AC to DC charger.

I only have 600w of solar, but 200w can tip plus I have another 200w of portable I can add. My plan is if the roof air craps out, then I will go with a mini split type system and fill in the space on the roof with 200W.

I am leaving the original AC converter in place but it will be switched off most of the time, it will only have the power jacks wired to it. I did test running the jacks off the converter alone, initial spike of 42 amps with a load of 24 amps with all 4 running at the same time. This eliminates running the jacks thru the 24V to 12V buck converter.

Everything else that runs on 12V will run thru the 720w buck converter. Buck converter is way oversized for this purpose, that was intentional as I don't run electrical at full capacity.

PV cables enter thru the refrigerator roof vent. I pulled the 3 way fridge out, takes less than 10 minutes, and ran not only the PV cables down thru the space around the refrigerator, but also installed all my displays and inverter remote switch on the wall facing the couch.

As for the air conditioner, the roof air probably draws 1200w with compressor running. These are horribly inefficient, if you're serious about running the ac off the batteries, then you should look into a mini split system or something like this. https://diysolarforum.com/threads/i...ts-in-tech-news-or-anything.21064/post-253431

I find the 12v/24v mini split type to be a possibly the solution. The condenser unit is only 6.5 inches tall, it could actually fit under my panels that are mounted along the sides of the current roof air and have a tilting mechanism.

 

[Whinny]

Your transfer switch is sized to the main breaker in the panel-most likely 30a. If you have a WFCO converter their transfer switch can mount to it similar to Will's video. You may wish to wire it "backwards" so the inverter/batteries don't energize the relay, the shore power does....

 

[jungry]

I considered making a 24 volt system but I am building it slowly over time and I have a 30 day road trip coming up so I am just going to install the 12 volt DC-DC charger first so that we can have power for that trip. I suppose I could still change the system to 24 volt afterwards. However, I already ordered the Renogy 3000 watt inverter, it states it is "optimized for 12 volt systems. I wonder if it can still convert 24 volts? It was on sale last night and I got 10% off in addition because of the Will Prowse coupon, thanks Will. I also sort of wanted a 12 volt system so that in an emergency I could have my prius charge everything in the camper and plug the camper into appliances in the house. We have power outages annually.

Whinny, can you elaborate on the wiring backwards idea and give advantage/disadvantage?

As far as the air conditioning, I likely wont use it very often but none the less I might so, I wanted to attempt to have some capacity to do so, it's not a necessity.