diy solar

diy solar

Trailer LifePo4 Upgrade + Add an Inverter + Solar in Future

I came to this forum looking for precisely what you are doing, noblesin; thank you for posting with so much detail. In my case I have a retrofitted Parallax 7345 (that replaced the stock 6345) in my 1997 Four Winds Class C.

I'm also designing the system to work primarily with an external generator or shore power. I was very happy to read from someone who already owned one that the eTrailer brand generator was able to run his A/C without needing to install the soft-start device in the A/C. I bought the generator and have found the same thing; here is their generator product page. I've got the built in Onan 4000W generator too but it uses 0.5gal/hr of gasoline whereas the eTrailer 2000W generator uses just 0.15 on eco mode and probably double at full bore—still less than the Onan and much quieter, too.

I'll add solar as Phase 2 of the project. Getting my system to work with the air conditioner is the first priority.

For the battery, I just ordered the Ampere Time 200ah battery for $969+tax. Couldn't justify double that price for the BattleBorns or even 75% more for the SOKs plus the low profile works best for where I want to place the battery. Another forum member reports that the battery has worked well for them so far even though the max. output is just 100 amps. Just like him, if this works well perhaps I'll buy a second one to get the 200 amps. (Or perhaps I find the 100 amps is just fine in real world use.)

One benefit of batteries from other companies is that some of the designs are end-user serviceable if a cell goes bad (after the warranty expires). I don't know if that's true for the Ampere Time battery so I've asked a question on their Amazon product page. It's definitely less expensive to buy a single, bigger battery (only one BMS instead of two) but I wonder if purchasing two smaller batteries is better if a cell goes bad at some point.

I'm now on the hunt for a charger/inverter/transfer switch. I wasn't aware of the Sun Gold Power company; I think it might just be perfect for my purposes. Going to read up on it now.
 
I'm new to all of this as well and I've also been doing a lot of research into the DC-DC charging question for trailer towed vehicles. It seems that if you want to charge your batteries in the trailer effectively from the tow vehicle you will need to run a fused dedicated line from your TV battery to your hitch, then install a connector (anderson or otherwise) and run the connection to the TT battery through the DC-DC converter. I'm looking at the Renogy or Redarc DC-DC MPPT as an all in one elegant solution.

Here's an interesting question... could you connect the TV battery and the converter output to a 3 way switch and then take the output from the switch to the DC input on the DC-DC converter? Then you could switch between the TV battery and shore power charging essentially and let the DC-DC converter manage the charge profile? Not sure if it would work at all, but it would seem like an elegant solution allowing the DC-DC converter to manage all charging of the batteries (including solar). Not sure if converter --> DC-DC would work though.
 
I'm new to all of this as well and I've also been doing a lot of research into the DC-DC charging question for trailer towed vehicles. It seems that if you want to charge your batteries in the trailer effectively from the tow vehicle you will need to run a fused dedicated line from your TV battery to your hitch, then install a connector (anderson or otherwise) and run the connection to the TT battery through the DC-DC converter. I'm looking at the Renogy or Redarc DC-DC MPPT as an all in one elegant solution.

I believe this is the way to go from what I've discovered so far. I'm wondering if this will be worth it doing this work and buying the additional DC-DC charger given that my 560AH capacity will last way longer than any Trip so maybe I might just stick to the Shore Power/Generator charging and skip adding the Tow Vehicle Charging option using a DC-DC Charger. On the other hand, Getting the DC-DC Charger setup now would let me add Solar in the Future to same DC-DC Charger easily.

Here's an interesting question... could you connect the TV battery and the converter output to a 3 way switch and then take the output from the switch to the DC input on the DC-DC converter? Then you could switch between the TV battery and shore power charging essentially and let the DC-DC converter manage the charge profile? Not sure if it would work at all, but it would seem like an elegant solution allowing the DC-DC converter to manage all charging of the batteries (including solar). Not sure if converter --> DC-DC would work though.

Hmm.. So basically something like this:

Shore Power -> WFCO 8735 Converter -> DC-DC Charger -> LifePo4 Batteries
Tow Vehicle Battery -> DC-DC Charger -> LifePo4 Batteries
Solar -> DC-DC Charger -> LifePo4 Batteries

In this case, You're suggesting you'd only need an Inverter and not the all-in-one?
 
Using the converter as a source for the DC-DC charger is not something I would do. Mainly because of efficiencies. It also is an overly complicated setup. I'm not saying it can't be done, just that it's out of the norm of what most people would expect to find.

There is nothing wrong with having three charging sources for a battery bank, all operating at the same time. In my prior configuration, I had both my AC-DC converter and my solar system charging the battery at the same time with no issues. I watched the solar monitor as this happened and it reduced the amps to nothing since it saw the converter's charge.

Running a dedicated DC wire from the tow vehicle's battery is necessary if:
1. That's your main source for charging the battery
2. You lack sufficient depth in your battery bank to last your camping trip

If you need a small charge, say 20 amps, then I would tie the DC-DC charger in after the 7-pin cable. Most vehicles will provide about that many amps. My F-350 will provide a max of 30 amps to the 7-pin connection, despite the alternators having a combined 397 amp output. (That output rating is likely way off as the two alternators don't typically run at the same time, they take turns to keep the heat down.)

For my trailer, the 640 watts of solar on top of the trailer are plenty to keep the LiFePO4 560 Ah battery bank charged up and ready for a camping trip. Because of that, I have disconnected the circuit from the tow vehicle (through the 7-pin cable) to the main 12v system in the trailer. The 7-pin circuit still charges an isolated 12v FLA battery on the trailer tongue that is used for the trailer breakaway system, generator starter and tongue jack.
 
There is nothing wrong with having three charging sources for a battery bank, all operating at the same time. In my prior configuration, I had both my AC-DC converter and my solar system charging the battery at the same time with no issues. I watched the solar monitor as this happened and it reduced the amps to nothing since it saw the converter's charge.

So, in this case we would connect the DC-DC MPPT and the AC converter output to the positive post of the battery? Assuming the BMS for the Lithium battery will manage everything ok without harming the battery?

Running a dedicated DC wire from the tow vehicle's battery is necessary if:
1. That's your main source for charging the battery
2. You lack sufficient depth in your battery bank to last your camping trip

If you need a small charge, say 20 amps, then I would tie the DC-DC charger in after the 7-pin cable. Most vehicles will provide about that many amps. My F-350 will provide a max of 30 amps to the 7-pin connection, despite the alternators having a combined 397 amp output. (That output rating is likely way off as the two alternators don't typically run at the same time, they take turns to keep the heat down.)

I was looking at doing this with the Renogy 50 AMP DC-DC MPPT, the problem is that when it doesn't detect solar (night time driving?) it would then attempt to pull 50 AMP from the vehicle through the 7 pin and blow the 30 AMP fuse most likely. I am trying to find out if the Renogy DC-DC MPPT works differently but I haven't found the answer to that yet.

Thanks!
 
Shore Power -> WFCO 8735 Converter -> DC-DC Charger -> LifePo4 Batteries
Tow Vehicle Battery -> DC-DC Charger -> LifePo4 Batteries
Solar -> DC-DC Charger -> LifePo4 Batteries

In this case, You're suggesting you'd only need an Inverter and not the all-in-one?

That was my thinking, but I'm a beginner :)
 
So, in this case we would connect the DC-DC MPPT and the AC converter output to the positive post of the battery? Assuming the BMS for the Lithium battery will manage everything ok without harming the battery?


I was looking at doing this with the Renogy 50 AMP DC-DC MPPT, the problem is that when it doesn't detect solar (night time driving?) it would then attempt to pull 50 AMP from the vehicle through the 7 pin and blow the 30 AMP fuse most likely. I am trying to find out if the Renogy DC-DC MPPT works differently but I haven't found the answer to that yet.

Thanks!

Yes, it would all work out OK.

An all-in-one solution is attractive. Less wiring, less space, less design, less install hassle. But, you have less flexibility. That DC-DC and MPPT combined unit does have problems from what I've read. I would rather have individual components that do exactly what they'll do in a predictable manner.

It's kind of like building the best sounding stereo system. If you want the best system - for your ears - you don't buy an all-in-one, you buy the individual components that work for you.
 
Yes, it would all work out OK.

An all-in-one solution is attractive. Less wiring, less space, less design, less install hassle. But, you have less flexibility. That DC-DC and MPPT combined unit does have problems from what I've read. I would rather have individual components that do exactly what they'll do in a predictable manner.

It's kind of like building the best sounding stereo system. If you want the best system - for your ears - you don't buy an all-in-one, you buy the individual components that work for you.
Understood, and makes sense. So, I can use a 20AMP DC-DC and wire that into the 7pin from the Tow Vehicle without concern for overdraw. Then use a separate MPPT Solar Charger and all should work out well.
 
Just make sure your tow vehicle's 7-pin connection is rated for what the DC-DC charger can pull.
Sorry to be asking a silly question but how does one validate this? Just look at the fuse? Look at the guage of the wire? Is there something I can look up about the factory hitch/7-pin connector? Thanks again.
 
Just make sure your tow vehicle's 7-pin connection is rated for what the DC-DC charger can pull.
I would also use an isolated DC to DC alternator charge controller. That way you can ground the house battery negative to the trailer chassis ground and not worry about the alternator connection creating a ground loop. The isolated Victron DC to DC charge controller is about $40 more than the non-isolated version.
 
Sorry to be asking a silly question but how does one validate this? Just look at the fuse? Look at the guage of the wire? Is there something I can look up about the factory hitch/7-pin connector? Thanks again.
Check the size of the fuse in that wire. You can be pretty sure you are not going to be pulling much more than that for very long.
 
If it hasn't already been mentioned :

Iota makes a DLS series charger with IQ-Li module that may work in your application.

Here is a link to the IQ module that works with the DLS charger/converters:

 
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