IBallEngineer
New member
Waaaaeeell, if it's single malt, who needs ice? Or cold, just drink and, well drink.
How to Charge Towed RV Battery while running?
- Thread starter bass-o-matic
- Start date
Waaaaeeell, if it's single malt, who needs ice? Or cold, just drink and, well drink.
vanion2
New member
Wow....I have been away for a while and just got caught up on this thread.
First, nice project. That trailer looks pretty sharp. There's some information I have read here I feel needs some clarification.
For example, PWM versus MPPT charge controllers. You can wire panel in series or parallel with either as long as the controller is rated for the voltage and currents. So you very much CAN wire 1,2,or 4 x 100W panels in series on a PWM controller. There is absolutely nothing wrong with PWM charge controllers either. The bragging rights of the MPPT is it is more efficient at charging batteries. The catch? It is no more efficient than a PWM with 400W or less systems and is less efficient in hot environments. The price increase does not justify the efficiency gains on small systems. I run a Tristar TS-60 PWM with 2 x 100W panels in parallel charging two 125A/Hr AGM batteries and on a sunny day will be floating in a matter of 4 hours after running the DC furnace all night (we camp in high elevations during the summer). It can run 12/24/48V configurations up to 60A. It costs $180 average retail and has more features than you would ever need.
Word of advice. 3 Way fridges are horribly inefficient in DC mode. You can run a fridge on propane for over a month alone on a single 5 gallon tank. Why would you tax your batteries when you could just leave it on propane? It uses a pilot light amount of gas to heat the coils versus a constant drain on the batteries to run current through a resistance coil to do the same thing. Sure, your solar panels can offset that but if you forget to switch it back just once your batteries are done before you wake up in the morning and realize your mistake. Besides, the propane heat is more effective as resister coils are subject to "cold" spots due to thermal expansion.
Bass-o-matic: They sell 2 (AC/LP) Way fridges for RV's in many different sizes, color schemes, etc. I would strongly suggest you go that route. Heck, you could get a 6 CU stainless steel 2 way that would look good and get the job done. Just saying that unless you want to drop money on a quality inverter and carry more batteries this is the way I would go. I bet the price would be cheaper for the fridge but that's just a guess.
I also read that some dispute the gauge of the wiring having a negligible affect. For the alternator on the 4Runner I would agree but for the solar panel wiring 10 gauge is "ok" if you are using that to connect your panels together. For any length of wiring needed beyond that you should be running 8 gauge up to 20 feet. If longer then you need to be at 4 gauge. I buy the MC4 connectors in kits and easily wire it up to 8 gauge wiring. I have even done 4 gauge house wiring but it requires trimming the ends of the copper to make it fit. You want to max your current through put unless you just feel like spending money on extra panels to compensate for resistance loss. This is the #1 mistake made by DIY solar projects. #2 is buying a cheap charge controller. #3 is not installing a quality power monitor to track exactly how much your system is actually charging versus discharging due to usage (I am looking at a Trimetric).
Finally, I don't prefer running panels in series simply because if one gets shaded then your batteries are not getting charged. I know that series gets you higher voltage but if that is your goal, I would recommend buying 2 x 250W 24V panels and wiring them in parallel . Yes, they are bigger and cost more but for the cost of 3 x 100W 12V panels you are already almost there and you get more efficient use of your MPPT controller ($480 2x250W 24V vs $450 3x100W 12V using Renogy brand as an example).
If I had nothing but money to spend I would buy an MPPT controller and wire up 4 x 250W/24V house panels in parallel and call it a day. 1KW of power to a LIon battery bank that quick charges, doesn't out gas, and you can discharge 80% without any negative battery impact. Of course that setup would cost about $6000. Of course I would run 4 gauge house copper from the panel junction box to the charge controller on as short a run as possible. Sure, I would still have to run my 3KW generator to run the A/C but everything else (including the 12V LED TV and DVD player) could be run off the batteries for a boondocker's paradise.
At the end of the day though, 400W of panels with a quality charge controller (PWM or MPPT), proper wiring, and proper discipline will easily get you through a camping trip without killing your batteries while still keeping warm at night. Anything I write here is just advice as there are many ways to make a solar system work. All I hope is that you are a happy camper when all is said and done.
First, nice project. That trailer looks pretty sharp. There's some information I have read here I feel needs some clarification.
For example, PWM versus MPPT charge controllers. You can wire panel in series or parallel with either as long as the controller is rated for the voltage and currents. So you very much CAN wire 1,2,or 4 x 100W panels in series on a PWM controller. There is absolutely nothing wrong with PWM charge controllers either. The bragging rights of the MPPT is it is more efficient at charging batteries. The catch? It is no more efficient than a PWM with 400W or less systems and is less efficient in hot environments. The price increase does not justify the efficiency gains on small systems. I run a Tristar TS-60 PWM with 2 x 100W panels in parallel charging two 125A/Hr AGM batteries and on a sunny day will be floating in a matter of 4 hours after running the DC furnace all night (we camp in high elevations during the summer). It can run 12/24/48V configurations up to 60A. It costs $180 average retail and has more features than you would ever need.
Word of advice. 3 Way fridges are horribly inefficient in DC mode. You can run a fridge on propane for over a month alone on a single 5 gallon tank. Why would you tax your batteries when you could just leave it on propane? It uses a pilot light amount of gas to heat the coils versus a constant drain on the batteries to run current through a resistance coil to do the same thing. Sure, your solar panels can offset that but if you forget to switch it back just once your batteries are done before you wake up in the morning and realize your mistake. Besides, the propane heat is more effective as resister coils are subject to "cold" spots due to thermal expansion.
Bass-o-matic: They sell 2 (AC/LP) Way fridges for RV's in many different sizes, color schemes, etc. I would strongly suggest you go that route. Heck, you could get a 6 CU stainless steel 2 way that would look good and get the job done. Just saying that unless you want to drop money on a quality inverter and carry more batteries this is the way I would go. I bet the price would be cheaper for the fridge but that's just a guess.
I also read that some dispute the gauge of the wiring having a negligible affect. For the alternator on the 4Runner I would agree but for the solar panel wiring 10 gauge is "ok" if you are using that to connect your panels together. For any length of wiring needed beyond that you should be running 8 gauge up to 20 feet. If longer then you need to be at 4 gauge. I buy the MC4 connectors in kits and easily wire it up to 8 gauge wiring. I have even done 4 gauge house wiring but it requires trimming the ends of the copper to make it fit. You want to max your current through put unless you just feel like spending money on extra panels to compensate for resistance loss. This is the #1 mistake made by DIY solar projects. #2 is buying a cheap charge controller. #3 is not installing a quality power monitor to track exactly how much your system is actually charging versus discharging due to usage (I am looking at a Trimetric).
Finally, I don't prefer running panels in series simply because if one gets shaded then your batteries are not getting charged. I know that series gets you higher voltage but if that is your goal, I would recommend buying 2 x 250W 24V panels and wiring them in parallel . Yes, they are bigger and cost more but for the cost of 3 x 100W 12V panels you are already almost there and you get more efficient use of your MPPT controller ($480 2x250W 24V vs $450 3x100W 12V using Renogy brand as an example).
If I had nothing but money to spend I would buy an MPPT controller and wire up 4 x 250W/24V house panels in parallel and call it a day. 1KW of power to a LIon battery bank that quick charges, doesn't out gas, and you can discharge 80% without any negative battery impact. Of course that setup would cost about $6000. Of course I would run 4 gauge house copper from the panel junction box to the charge controller on as short a run as possible. Sure, I would still have to run my 3KW generator to run the A/C but everything else (including the 12V LED TV and DVD player) could be run off the batteries for a boondocker's paradise.
At the end of the day though, 400W of panels with a quality charge controller (PWM or MPPT), proper wiring, and proper discipline will easily get you through a camping trip without killing your batteries while still keeping warm at night. Anything I write here is just advice as there are many ways to make a solar system work. All I hope is that you are a happy camper when all is said and done.
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GangsterOfLove
New member
It it were me, I'd try to find a late model RV wreck and pull the 120v/propane fridge out of it.
Propane fridges work great and you can even make your own ice. Little DC fridges can't do that (of if they can I've never seen one).
Propane fridges work great and you can even make your own ice. Little DC fridges can't do that (of if they can I've never seen one).
IBallEngineer
New member
Lots of good info in [MENTION=110437]vanion2[/MENTION] 's post. And he correctly cleared up what I misstated. You CAN wire a PWM controller in series. However it must be rated for said higher voltage. Since most PWM controllers are limited to 60 Amps, most are 20 or 30 Amps rated, it's doubtful you'd find one that would handle more than 2 panels.
Renogy has two 30 Amp PWM controllers on their site, both are limited to 25V on a 12V system. The 40A MPPT is hella xpensive comparted to the PWM. But in the big picture, it's $225 or so. The shade thing can be a drag, less of a problem in the desert than the mountains.
Really no reason for a travel trailer NOT to have a propane fridge. I burnt up my 110 heater on my RV fridge and ran it on propane for 11 days with no problems. Most of my camping is dry, so propane wins the day there too.
:fishing:
Renogy has two 30 Amp PWM controllers on their site, both are limited to 25V on a 12V system. The 40A MPPT is hella xpensive comparted to the PWM. But in the big picture, it's $225 or so. The shade thing can be a drag, less of a problem in the desert than the mountains.
Really no reason for a travel trailer NOT to have a propane fridge. I burnt up my 110 heater on my RV fridge and ran it on propane for 11 days with no problems. Most of my camping is dry, so propane wins the day there too.
:fishing:
A.Wilson013
New member
I was going to say that you could also take the trailer off of the hitch, turn around, and use jumper cables.
And then it hit me... :loco:
