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Olddawgsrule View Drop Down
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Posts: 1014 		Direct Link To This Post Topic: Lithium Battery install ?
    Posted: 28 Oct 2019 at 9:20am
Originally posted by JR

If this helps when I installed solar on my 179 last fall and the 179 is a 2019, the TV charging wiring going through the 7 pin connector was wired directly to the + side of the 12v trailer's battery.  Hope this helps.  Depending on where the WFCO convert is located, mine was in the back of the 179 by the entry door, and the + lead from the convert to the battery was one direct wire but the - lead was wired to the frame by the passenger side trailer wheel and then taken from the frame near the battery box to the - side of the battery.  Just some more incidental information.

Have fun,
Jay

Interesting.. Mine has only the main battery cable & the Solar-on-the-side line. You have a third? I know there is a buss bar (of sorts) near the auto-fuse underneath the camper up front. My thought is this may be where the 7 pin wire goes. That auto fuse does go to the battery.. That's the first place I hope to trace.

Another wet day today, so won't get out there to trace lines today, even with the power dis-connected.. 
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JR View Drop Down
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Posts: 375 		Direct Link To This Post Posted: 28 Oct 2019 at 7:32am
If this helps when I installed solar on my 179 last fall and the 179 is a 2019, the TV charging wiring going through the 7 pin connector was wired directly to the + side of the 12v trailer's battery.  Hope this helps.  Depending on where the WFCO convert is located, mine was in the back of the 179 by the entry door, and the + lead from the convert to the battery was one direct wire but the - lead was wired to the frame by the passenger side trailer wheel and then taken from the frame near the battery box to the - side of the battery.  Just some more incidental information.

Have fun,
Jay
Jay

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Olddawgsrule View Drop Down
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Posts: 1014 		Direct Link To This Post Posted: 28 Oct 2019 at 7:28am
Originally posted by offgrid

Just to clarify your flow chart, when you say you're going to go from the 7 pin connector to the junction at panel, you mean you're going to isolate that circuit from the distribution panel itself, right? Otherwise you would be providing a connection directly from the 7 pin connector to the Li battery, bypassing the b2b charger. 

I've never traced out the routing of the TV 12V circuit from the connector to the panel, but it doesn't really matter where between the trailer connector and the panel you place the b2b charger. as long as the charger is regulating the TV battery voltage before it gets to the Li battery. The shorter the conductors in that circuit are the less resistance losses you're going to have.   You could even locate the charger in the TV between the battery and the trailer connector if you wanted to.

Correct, the thought is I find the junction and splice in before the panel. I have to say I like the idea of putting it in the TV before the pin connector! Yet another reason I ask such things! Thank you
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offgrid View Drop Down
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Posts: 5290 		Direct Link To This Post Posted: 27 Oct 2019 at 7:08pm
Just to clarify your flow chart, when you say you're going to go from the 7 pin connector to the junction at panel, you mean you're going to isolate that circuit from the distribution panel itself, right? Otherwise you would be providing a connection directly from the 7 pin connector to the Li battery, bypassing the b2b charger. 

I've never traced out the routing of the TV 12V circuit from the connector to the panel, but it doesn't really matter where between the trailer connector and the panel you place the b2b charger. as long as the charger is regulating the TV battery voltage before it gets to the Li battery. The shorter the conductors in that circuit are the less resistance losses you're going to have.   You could even locate the charger in the TV between the battery and the trailer connector if you wanted to.
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Olddawgsrule View Drop Down
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Posts: 1014 		Direct Link To This Post Posted: 27 Oct 2019 at 10:55am
Here's the basic's I have in mind.


I'm looking at the Renogy 12/12 20amp charger. For right now I may use my small lithium battery (38ah) or just buy something over the winter in the 60-100ah range. Size will depend mainly on pricing (deal). 

I am assuming right now that the 7 pin wiring goes all the way to the panel. I do now there is this auto breaker (and buss bar?) located under the Rpod up front. Could this be a location to tap in the 12/12 charger? 
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offgrid View Drop Down
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Posts: 5290 		Direct Link To This Post Posted: 26 Oct 2019 at 9:05am
OK, sounds good. The benefit of staying under 30A for your dc dc converter feed is that you probably have that capacity already coming through your trailer connector, you'll just need to run that to the converter rather than the 12V battery buss. 

For me since I want to run about 80A I'm going to have to install a dedicated high capacity circuit and connectors between the TV and the trailer.  
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Olddawgsrule View Drop Down
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Posts: 1014 		Direct Link To This Post Posted: 26 Oct 2019 at 7:48am
Very good indeed. I expected some efficiency loses.

My daily usage (at max) could be returned in a hour! The worst I hit (2 runs back) was down 700+ watts and it was still rain in our future, for a couple more days. Believe that was over 4 days. We packed up (time to head out anyway) and charged up on the drive (mostly). That's how I usually get recharged, solar or TV. 

From what I have reading/learning and what you stated of our B to B is direct, it seems beneficial to mount one of these charger units, anyway. I see several can be set for PbA, Gel, Agm or Lithium's.  
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Posts: 5290 		Direct Link To This Post Posted: 26 Oct 2019 at 7:06am
Normally power electronic devices are specified by their output not their input so in theory the dc/dc converter you're talking about ought to output 20A. It would be the input current that would be higher than 20A.  

Wiring losses don't effect current, they result in voltage drops so that shouldn't reduce the output current. The wiring losses show up as a lower voltage at the Li battery terminals than the output voltage limit you set for the converter. I would just use as large a wire gauge as will fit on the converter terminals and try to keep the wire runs short. So, at 20A 4 hours runtime ought to give you 80 amphours. But 4 hours idling your TV to recharge your battery while camping is a long time. 

For me the design criteria are to minimize the TV engine idle time by recharging in as short a time as possible while not overloading the alternator. Alts are not good for their nominal rating at idle, it is quite a bit less.  I did that test on my Highlander and got about 80A available from a 150A rated alt at idle after electrical demand from the ignition system, engine ecu, and radiator fans was met (all other TV electrical loads off). So, depending on your alt capacity you too probably can run a larger dc/dc converter than 20A to keep your charging times shorter. 
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Olddawgsrule View Drop Down
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Posts: 1014 		Direct Link To This Post Posted: 25 Oct 2019 at 9:02am
Let's get into this B to B a little better please. I wish to see if I'm really understanding..

Seems I could run with a 12V 20a unit. If I place the efficiency at 80% (wiring, unit, etc..), I'm looking at 16amps now. Is that a good assumption? 
Then I'm curious if indeed I will get the 16amps continuously. What can you really expect over a 4 hour period? 64amps (using my 16a assumption)??

If any of this is even close, then I may also just dis-connect the WFCO, actually mount a switch so it could be switched back over. 
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Posts: 5290 		Direct Link To This Post Posted: 24 Oct 2019 at 8:10pm
Originally posted by Olddawgsrule


Okay.. Biggest part of research right now is: How will you stop the WFCO charger? Or will you? 
I've read good points on both sides of the fence on this one...

I plan to just remove the wfco. It will not be needed. 

I want to go with a 24Vdc Li battery, a 24V MPPT solar charge controller, and a 12 to 24V dc/dc converter from the TV. I'll have a small 24 to 12 Vdc converter to run the existing 12Vdc loads in the trailer, and a 2 to 3 kw 24Vdc to 120Vac inverter to run the heavy a/c and microwave loads. Everything is more efficient and you need much less copper conductor at 24V, and there are great deals available on 24V battery packs from wrecked Teslas. 

If I have 120Vac grid power available I can run the heavy loads directly on that. The 12Vdc loads are so small compared to the system I want to install that I don't ever expect to need to charge from the grid for that anyway. The solar will take care of it. 
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