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I am trying to figure our the easiest way to have my motorhome, benefit from the solar on my trailer!

some background:

The trailer has 4 160w panels, with 4 lifeline batteries and a magnum inverter.  It is plenty of juice for the trailer to power the lights, air compressor etc, keeps the batteries topped off easily, but I feel like I'm not getting much benefit from it when the sun is high, because the batteries are already topped off, so they just charge in a float mode.

I would like to somehow have that extra juice go to my motorhome during the day, to help keep that topped off (minimize or cutback on generator use)

 

what is the easiest way to do this??

 

also another question (not sure if I should start a separate thread) but my solar charge controller in the trailer is a morningstar PWM charged, and I feel like it is not allowing max charge rate to the batteries (they stay topped off anyway due to minimal use, but if I want to run juice to the motorhome I need to maximize the charge rate).  Currently I rarely ever see a charge rate of over 200W.  I am thinking I need to go with a newer MPPT charge controller, and wondering what you guys recommend?

This is the charge controller that I currently have

https://www.amazon.com/Morningstar-TS-45-Communications-Protections-Programmable/dp/B0012DNFT2/ref=asc_df_B0012DNFT2/?tag=hyprod-20&linkCode=df0&hvadid=312196574864&hvpos=&hvnetw=g&hvrand=3726229436221136945&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9031484&hvtargid=pla-427440115362&th=1

 

CF5F8D55-AC11-4DE5-96D3-43FCE7F7B5AD.thumb.jpeg.b36eec908a0625c172cbd0a7d56b905d.jpeg6B6D128C-2AA9-44B9-B8ED-6597374BC690.thumb.jpeg.58447a95df803afd0702a580e32e7e94.jpeg

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15 minutes ago, Jtmoney714 said:

Can you just plug the motorhome into the trailer like you would a separate generator?

I can... but the trailer only has 15amp plugs going out...

and I tried this last season, but it would overload the inverter inside the trailer... because that inverter is trying to charge the trailer batteries, and then once I plugged in the motorhome, it fires up the motorhome inverter to charge those batteries... which is why I think it's overloading the system.   This probably wouldn't be an issue of I was getting max charge rate out of my panels.

So I either need to get the system working good enough to where I can just pug in my motorhome.... or I need some sort of contraption to have the charge rate from the trailer batteries, also feed the motorhome batteries.... so that when the sun is up... all batteries are being charged... not just the 4 in the trailer. 

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The easiest way to upgrade your solar controller is to get a Renogy 40A MPPT controller with BT. It's fairly inexpensive and works great. How are your solar panels connected? In series or parallel? If you go to the mountains/woods, I'd recommend having them all in parallel to minimize the effects of shading on one or more panels. If you're sure you'll never experience shading, a good way to go would be to connect them in 2 strings of series panels then connect the 2 strings in parallel, giving you about 36 v. Keep in mind you'll only see about a max. of 80% of the rated power, so if everything was working perfectly at noon in summer, you should see about 500 - 512w.

As for powering your moho off of the trailer, you've already found a problem with your trailer inverter trying to power your moho battery charger. If you want to have your trailer solar and batteries charge your moho batteries, the easiest way is probably to connect the trailer batteries to the moho batteries using some heavy gauge cable like 2/0 or 4/0, through a large (300A-400A) circuit breaker and large Anderson plugs. This way you don't lose power converting it to 120v and back down to 12v. You can disconnect the Anderson plugs at the trailer hitch and flip the breaker to remove power from the plug and protect the cabling. This way, both sets of batteries can draw off of each other depending on whether the trailer or moho is drawing more power.

There's a more complicated way to use the trailer inverter to power the moho outlets, but it's much better to dump the power into your batteries and let the batteries power your moho inverter as originally designed.

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49 minutes ago, Lord of the Dunes said:

The easiest way to upgrade your solar controller is to get a Renogy 40A MPPT controller with BT. It's fairly inexpensive and works great. How are your solar panels connected? In series or parallel? If you go to the mountains/woods, I'd recommend having them all in parallel to minimize the effects of shading on one or more panels. If you're sure you'll never experience shading, a good way to go would be to connect them in 2 strings of series panels then connect the 2 strings in parallel, giving you about 36 v. Keep in mind you'll only see about a max. of 80% of the rated power, so if everything was working perfectly at noon in summer, you should see about 500 - 512w.

As for powering your moho off of the trailer, you've already found a problem with your trailer inverter trying to power your moho battery charger. If you want to have your trailer solar and batteries charge your moho batteries, the easiest way is probably to connect the trailer batteries to the moho batteries using some heavy gauge cable like 2/0 or 4/0, through a large (300A-400A) circuit breaker and large Anderson plugs. This way you don't lose power converting it to 120v and back down to 12v. You can disconnect the Anderson plugs at the trailer hitch and flip the breaker to remove power from the plug and protect the cabling. This way, both sets of batteries can draw off of each other depending on whether the trailer or moho is drawing more power.

There's a more complicated way to use the trailer inverter to power the moho outlets, but it's much better to dump the power into your batteries and let the batteries power your moho inverter as originally designed.

Thanks for the feedback... is that 40A controller sufficient for the 4 panels that I have?

I really don't know much about series / parallel.... but currently it looks like 2 panels are tied together.... because out of 4 panels, I only have 2 lines going down to the charge controller.  I am not worried about shading at all... trailer only sees glamis.

where would I get stuff to put together cables like that?

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I also have to make sure it somehow doesn't overcharge the system, if my wife or kids accidentally fire up the motorhome generator... while solar power is coming in. 

 

I'm just trying to avoid putting any solar on the motorhome itself, since it seems like the trailer has plenty to go around. 

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3 hours ago, EmpirE231 said:

Thanks for the feedback... is that 40A controller sufficient for the 4 panels that I have?

I really don't know much about series / parallel.... but currently it looks like 2 panels are tied together.... because out of 4 panels, I only have 2 lines going down to the charge controller.  I am not worried about shading at all... trailer only sees glamis.

where would I get stuff to put together cables like that?

You'll actually have to trace the wires to tell how the system is wired, or measure the input V at the controller. More than likely they're all in parallel (18.2V), since it's all connected to a PWM controller.

Yes, the 40A controller would be able to handle up around 600w of actual input, so you're about 100w below that. You can get 10A cable and MC4 connectors from Amazon. To make a series/parallel setup, let's number the panels 1 - 4. Connect one cable (let's say positive) from panel #1 to the negative cable of #2. This leaves #1 negative cable and #2 positive cable still loose. Now connect #3 positive to #4 negative. This leaves 2 positive cables and 2 negative cables. You now have 2 pairs of panels connected in series. Now you need to connect those together with a pair of Y connectors. The 2 negatives connect to one Y and the 2 positives connect to the other Y. This puts the 2 strings in parallel to each other and leaves you one positive and one negative cable. These need to go down to a pair of DC circuit breakers and then to the 40A solar controller. From the solar controller, 2 wires should go to another pair of DC circuit breakers and then to the batteries.

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4 hours ago, EmpirE231 said:

I also have to make sure it somehow doesn't overcharge the system, if my wife or kids accidentally fire up the motorhome generator... while solar power is coming in. 

 

I'm just trying to avoid putting any solar on the motorhome itself, since it seems like the trailer has plenty to go around. 

With the solar controller, there's no danger of over charging the batteries. Set the absorption V to what the battery mfr suggests and it will charge up to that voltage and stop at that point then drop down to float voltage, usually about 13.7v. This won't interfere with the battery charger on the trailer, they will work together until the system V hits the absorption voltage of the lowest of the 2, that one will shut off and the other will shut off when it hits the programmed voltage.

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Most simple way is to just use a DC to DC charger.  Pick your poison on amps.  20, 40, or 60. it's only a one way street.  It wont take power from the coach.

It has a signal wire that looks for power from an alternator but in this case you would just tap this to a Low Voltage Disconnect like you would have on a boat to turn off an amp or acc.  It will use the power up until a certain point and then turn off and it wont turn back on until it sees voltage above the LVD turn back on point.  

Its designed to do what your describing.  Should only require 10 gauge wire. As mentioned above by LOTD I would get a newer MPPT charger.  I personally only use Victron stuff, but Renogy has been a good entry level brand also.  My box trailer has a small 80w panel and one of their small MPPT chargers.  Battery is always topped off.

 

https://www.amazon.com/dp/B07Q5VYPCF/ref=redir_mobile_desktop?_encoding=UTF8&aaxitk=85ee690706ea16965a11fc0d8c99616d&hsa_cr_id=-1494137137&pd_rd_plhdr=t&pd_rd_r=d9beca09-f967-4d31-9560-6726d9d7ae02&pd_rd_w=4wJz0&pd_rd_wg=7rFtt&ref_=sbx_be_s_sparkle_td_asin_2_title&th=1

https://www.amazon.com/Digital-Battery-Low-Voltage-Protection/dp/B07929Y5SZ/ref=sr_1_2?crid=2J2WSCLQ8LMHI&keywords=low+voltage+disconnect+12v&qid=1639576970&sprefix=low+voltage+dis%2Caps%2C234&sr=8-2

 

 

 

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18 minutes ago, r3meyer said:

Most simple way is to just use a DC to DC charger.  Pick your poison on amps.  20, 40, or 60. it's only a one way street.  It wont take power from the coach.

It has a signal wire that looks for power from an alternator but in this case you would just tap this to a Low Voltage Disconnect like you would have on a boat to turn off an amp or acc.  It will use the power up until a certain point and then turn off and it wont turn back on until it sees voltage above the LVD turn back on point.  

Its designed to do what your describing.  Should only require 10 gauge wire. As mentioned above by LOTD I would get a newer MPPT charger.  I personally only use Victron stuff, but Renogy has been a good entry level brand also.  My box trailer has a small 80w panel and one of their small MPPT chargers.  Battery is always topped off.

 

https://www.amazon.com/dp/B07Q5VYPCF/ref=redir_mobile_desktop?_encoding=UTF8&aaxitk=85ee690706ea16965a11fc0d8c99616d&hsa_cr_id=-1494137137&pd_rd_plhdr=t&pd_rd_r=d9beca09-f967-4d31-9560-6726d9d7ae02&pd_rd_w=4wJz0&pd_rd_wg=7rFtt&ref_=sbx_be_s_sparkle_td_asin_2_title&th=1

https://www.amazon.com/Digital-Battery-Low-Voltage-Protection/dp/B07929Y5SZ/ref=sr_1_2?crid=2J2WSCLQ8LMHI&keywords=low+voltage+disconnect+12v&qid=1639576970&sprefix=low+voltage+dis%2Caps%2C234&sr=8-2

 

 

 

never heard of the DC to DC charger  cool!

so youre using both items mentioned or can you just use one.  not really understanding the purpose or the roll the second part plays

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I used a Sure Power battery separator in my Rhino to separate the engine and stereo batteries.  Cheaper than above, and would work similar.  You would hook both positive cables to it, and a small ground wire.  You would also have to run a larger ground bewteen the trailer and coach as this assumes you would be using a similar chassis ground for both battery sets.  If the trailer batteries are above 13.2v (like when charging), it connects the banks.  If it falls below 12.7v, it disconnects the banks.

 

https://www.ase-supply.com/Sure_Power_1314_Battery_Separator_p/sp-1314a-b.htm

 

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Just now, John@Outfront said:

never heard of the DC to DC charger  cool!

so youre using both items mentioned or can you just use one.  not really understanding the purpose or the roll the second part plays

The second part turns the charger "on".

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4 minutes ago, Kraut_n_Rice said:

I used a Sure Power battery separator in my Rhino to separate the engine and stereo batteries.  Cheaper than above, and would work similar.  You would hook both positive cables to it, and a small ground wire.  You would also have to run a larger ground bewteen the trailer and coach as this assumes you would be using a similar chassis ground for both battery sets.  If the trailer batteries are above 13.2v (like when charging), it connects the banks.  If it falls below 12.7v, it disconnects the banks.

 

https://www.ase-supply.com/Sure_Power_1314_Battery_Separator_p/sp-1314a-b.htm

 

Not really because you would need to run much larger cables.  That system is set to turn on and move serious power.  100A+ usually.

This is very limited which works better for the solar setup.  DC - DC chargers started showing up with guys using LiFePo4 packs.  They would deplete them and then start their engines.  Because LiFePo4 will take just about every thing you can toss at them they were burning up Alternators.  IE bouncing off the rev limiter vs a nice 1500 RPM cruising speed. 

11 minutes ago, John@Outfront said:

isnt that what the D+ signal is for shown in the schematic on the charger itself?

Yes but then its going to just stay on the whole time which im not sure you want.  Because they are Lead Acid you STILL have to bring the batteries to 100% charge level each day or damage them.  Thats where the LVD would come into play.  Once they are full it will turn on and send power down the line then turn off once depleted.  

You can make this work anyway you like.  You could even just do it manually.  Just power up the D+ with a simple switch when you want to start charging.

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The DC to DC chargers work well. They are also called Battery to Battery chargers. You can get them in multiple voltages too. I have two of these on my big boat that are 24v to 12v. I take 24v off my starting banks and engine alternators and charge 12v aux batteries. They work great. They even have remote panels which are very convenient. Mine are from Sterling Power I believe. 

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http://www.lslproducts.net/ALS_Overview_Page.html

This would be the cheapest, easiest way. Hook this up in the trailer, make a set of leads on your coach from the batteries to the hitch,  and from this to the hitch as well. It'll just be an extra connector to hook up when you hitch up. When the trailer batteries are being charged (via solar) it will send 15 amps to the coach batteries. Fully automatic, nothing to fuss with. 

I use one in my motorhome to charge chassis batteries while the generator is running. Monaco had some huge overly expensive unit, when it crapped out I bought this. Works perfect. 

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I still don't understand why you can't simply plug the Moho into the trailer and charge through your trailer inverter? Your trailer inverter is only charging your trailer batteries if it is plugged into shore power or a generator. Otherwise your trailer batteries are only being charged from the solar panels via your charge controller direct to the batteries. If your trailer inverter is tripping when you plug in the Moho just reduce your charge rate on your Moho inverter as others suggested. But I doubt that the charging alone is what is tripping your trailer inverter. What else does your Moho inverter provide power to? A residential fridge? Some outlets, etc. ? I would try shutting everything off in the Moho and see if you can power the inverter in charge mode only. 

I don't know what size your Magnum trailer inverter is. But if it is a 2,000 watt it should have more than enough to power a 125 amp charger in your Moho inverter. Your 15 amp trailer outlet at 120 volts A/C is equal to 165 amps of DC at 12 volts and would be 1,800 watts. So you have little reserve to power other items depending on your charge rate. 

You can try to shut down the Moho and maybe charge while you are out riding and nobody's at camp? 

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2 hours ago, Dockmaster said:

I still don't understand why you can't simply plug the Moho into the trailer and charge through your trailer inverter? Your trailer inverter is only charging your trailer batteries if it is plugged into shore power or a generator. Otherwise your trailer batteries are only being charged from the solar panels via your charge controller direct to the batteries. If your trailer inverter is tripping when you plug in the Moho just reduce your charge rate on your Moho inverter as others suggested. But I doubt that the charging alone is what is tripping your trailer inverter. What else does your Moho inverter provide power to? A residential fridge? Some outlets, etc. ? I would try shutting everything off in the Moho and see if you can power the inverter in charge mode only. 

I don't know what size your Magnum trailer inverter is. But if it is a 2,000 watt it should have more than enough to power a 125 amp charger in your Moho inverter. Your 15 amp trailer outlet at 120 volts A/C is equal to 165 amps of DC at 12 volts and would be 1,800 watts. So you have little reserve to power other items depending on your charge rate. 

You can try to shut down the Moho and maybe charge while you are out riding and nobody's at camp? 

Using the trailer inverter to charge the moho batteries through the moho charger introduces a lot of losses into the system. Charging the trailer batteries already loses about 15% of the solar power, then the trailer inverter loses 8 - 10% converting that to AC power, then the moho charger loses another 10% and then the moho batteries lose another 15% in the charging process. Added all up, that's roughly 50% of the solar harvest. 

Connecting both sets of batteries via cables essentially turns both batteries into one larger capacity battery. This shared cap. means it only loses 15% of whatever charging power is provided. This also allows the batteries to share the load under high draw situations in both directions. This reduces the depth of discharge of both sets of batteries and prolongs their lives. For example he has 4 GC batteries in the trailer, assuming he has 4 GC batteries in the moho, when connected together they behave like an 8 GC battery bank which would be drawn down 1/2 as much by a large load as it would if it was a 4 GC bank. I see this a lot in yachts where they've installed 8 or 12 GC batteries and the loads from their electrical system weren't that large so the battery bank was operating from 100% down to 85% instead of 100% down to 50%. This allowed the battery bank to last 8, 10 yrs or more due to the gentle discharging and allowed longer periods between recharging if the sun wasn't shining or they didn't want to fire up the genny.  

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23 minutes ago, Lord of the Dunes said:

Using the trailer inverter to charge the moho batteries through the moho charger introduces a lot of losses into the system. Charging the trailer batteries already loses about 15% of the solar power, then the trailer inverter loses 8 - 10% converting that to AC power, then the moho charger loses another 10% and then the moho batteries lose another 15% in the charging process. Added all up, that's roughly 50% of the solar harvest. 

Connecting both sets of batteries via cables essentially turns both batteries into one larger capacity battery. This shared cap. means it only loses 15% of whatever charging power is provided. This also allows the batteries to share the load under high draw situations in both directions. This reduces the depth of discharge of both sets of batteries and prolongs their lives. For example he has 4 GC batteries in the trailer, assuming he has 4 GC batteries in the moho, when connected together they behave like an 8 GC battery bank which would be drawn down 1/2 as much by a large load as it would if it was a 4 GC bank. I see this a lot in yachts where they've installed 8 or 12 GC batteries and the loads from their electrical system weren't that large so the battery bank was operating from 100% down to 85% instead of 100% down to 50%. This allowed the battery bank to last 8, 10 yrs or more due to the gentle discharging and allowed longer periods between recharging if the sun wasn't shining or they didn't want to fire up the genny.  

The motorhome has 8 AGM's (4 dedicated to the fridge, 4 dedicated to the rest of the "house) and it has 2 separate inverters (one dedicated to the fridge, one to the house)

 

so In all, when tied to the trailer, it will be 12 total batteries. 

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5 minutes ago, EmpirE231 said:

The motorhome has 8 AGM's (4 dedicated to the fridge, 4 dedicated to the rest of the "house) and it has 2 separate inverters (one dedicated to the fridge, one to the house)

 

so In all, when tied to the trailer, it will be 12 total batteries. 

The GC batteries are connected in series to give you 12v, so 4 GC batteries looks like 2 12v batteries. Still, 10 batteries sharing the loads will last longer than 2 sets of batteries.

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7 hours ago, Looney Duner said:

http://www.lslproducts.net/ALS_Overview_Page.html

This would be the cheapest, easiest way. Hook this up in the trailer, make a set of leads on your coach from the batteries to the hitch,  and from this to the hitch as well. It'll just be an extra connector to hook up when you hitch up. When the trailer batteries are being charged (via solar) it will send 15 amps to the coach batteries. Fully automatic, nothing to fuss with. 

I use one in my motorhome to charge chassis batteries while the generator is running. Monaco had some huge overly expensive unit, when it crapped out I bought this. Works perfect. 

 

This does seem like a super basic setup (which is right up my ally lol)

it looks like it prevents backflow, which is nice...

now is 15 amps a decent amount of juice to help keep up 4 6v batteries?  Like I mentioned before.... I am not trying to eliminate generator use... just trying to reduce it if I can... due to a residential fridge running 24/7. I am assuming a system like this won't create any overcharge issue if it were running, and someone fired up the genny?

 

@r3meyer what do you think about this setup Vs. what you posted above?

 

 

I'd like to go all crazy and dial this thing.... but at the same time don't want too invest too much time and money, because I am not sure how long I will be keeping this trailer / moho combo.  So if I can somehow just fix my current solar issue w/ a new charge controller, and then do this basic setup to transfer juice from the trailer to moho... that would be perfect. 

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45 minutes ago, EmpirE231 said:

 

This does seem like a super basic setup (which is right up my ally lol)

it looks like it prevents backflow, which is nice...

now is 15 amps a decent amount of juice to help keep up 4 6v batteries?  Like I mentioned before.... I am not trying to eliminate generator use... just trying to reduce it if I can... due to a residential fridge running 24/7. I am assuming a system like this won't create any overcharge issue if it were running, and someone fired up the genny?

 

@r3meyer what do you think about this setup Vs. what you posted above?

 

 

I'd like to go all crazy and dial this thing.... but at the same time don't want too invest too much time and money, because I am not sure how long I will be keeping this trailer / moho combo.  So if I can somehow just fix my current solar issue w/ a new charge controller, and then do this basic setup to transfer juice from the trailer to moho... that would be perfect. 

Yeah this is a much better way to go with a system your size.  I forgot about the AMP-L-Start, but its because they didn't have a lithium option where it looks like now they do.

You wont have to worry about hurting anything.

15 amp x 24hrs = 360AH of possible power to transfer to the coach each day.  Dont think you will make that much solar so you should be able to consume everything you make that is in excess.

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