Upgrading existing solar in new RV

PlanetExcellent

New Member
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Sep 16, 2021
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Hi all, new member here. Just bought a travel trailer with factory-installed 80 watt solar panel and one lead acid battery. I'm thinking of installing the 400 watt/40 amp controller system with a 2000 watt inverter.

Does anyone know if @Will Prowse has any videos specifically dealing with the logistics of upgrading an existing system? Especially whether to keep/replace wiring, how to interface new components to existing power center/converter-charger/fuse panel? I don't want to change a lot of component locations if I don't have to. All the videos I've seen so far show assembling all the components together on one piece of wood, which won't be very practical for me.

I have the book and it's taught me the theory, but now I need to learn some installation techniques.
 

Alphacarina

Solar Enthusiast
Joined
Feb 22, 2021
Messages
215
The components can be installed pretty much anywhere you like, so long as they have proper ventilation. A large inverter is best installed as close to the battery bank as possible since they will draw a very large amount of current and the farther from the battery you place it, the larger the cables will have to be. The wiring to the roof for the panels may need to be replaced with larger gauge too, depending on what the factory installed and how large an array you'll be installing

With a single lead acid battery and only an 80 watt panel, you'll have an easier time if you just remove all the OEM stuff (maybe resell it) and start from scratch. Adding panels to your existing panel will be problematic and with a 2Kw inverter, you're going to want much more battery power and going with lithium makes lots more sense

Don
 

PlanetExcellent

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Sep 16, 2021
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Thanks for the reply. Agree on keeping the components close together; current battery is on the trailer tongue so I would put the new one inside.

I like the efficiency of running the solar panels at 24 volts, so I'm thinking of adding another 80 watt panel in series, plus a pair of 100 watt panels also in series for a total of 360 watts @ 24 volts. My thinking was at 24 volts I could keep the existing wiring coming down from the roof (which is either 10 or 12 gauge). A 40 amp charge controller. Probably one SOK 100 amp lithium battery to start and a second one later.

I was thinking of a 2000 watt inverter because I want to be able to run the 1200 watt microwave oven at least for a minute here and there. But I recently found a Samlex EVO-1212 1200 watt inverter with built-in transfer switch, 60 amp charger and converter which looks awesome. The specs say it can put out 1440 watts for 10 minutes and 1680 watts for 1 minute, so I'm wondering if that would accommodate brief microwave use.
 

WhiteHot

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Apr 9, 2021
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20
Thanks for the reply. Agree on keeping the components close together; current battery is on the trailer tongue so I would put the new one inside.

I like the efficiency of running the solar panels at 24 volts, so I'm thinking of adding another 80 watt panel in series, plus a pair of 100 watt panels also in series for a total of 360 watts @ 24 volts. My thinking was at 24 volts I could keep the existing wiring coming down from the roof (which is either 10 or 12 gauge). A 40 amp charge controller. Probably one SOK 100 amp lithium battery to start and a second one later.

I was thinking of a 2000 watt inverter because I want to be able to run the 1200 watt microwave oven at least for a minute here and there. But I recently found a Samlex EVO-1212 1200 watt inverter with built-in transfer switch, 60 amp charger and converter which looks awesome. The specs say it can put out 1440 watts for 10 minutes and 1680 watts for 1 minute, so I'm wondering if that would accommodate brief microwave use.
The SOK batteries have a 100A discharge limit. You will be very close to that limit if not over it with the 1200 watt microwave. If the limit was higher, I would have one of their batteries in my camper right now. Your plan would be fine is you had 2x SOKs in parallel.
 

PlanetExcellent

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Sep 16, 2021
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The SOK batteries have a 100A discharge limit. You will be very close to that limit if not over it with the 1200 watt microwave. If the limit was higher, I would have one of their batteries in my camper right now. Your plan would be fine is you had 2x SOKs in parallel.
Any thoughts on whether it's better to have 2x 100A batteries, or a single 200A battery? Having one battery saves a couple of thick cables, but it's a lot easier to move two 30-lb batteries than one 60-lb battery.
 

chrisski

Photon Sorcerer
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Aug 14, 2020
Messages
2,351
Two 100 amp batteries are easier to lift, and also more 100 ah choices than 200 ah choices. 100 LBS does not sound like much until you need to lift it by yourself up a step ladder, not once, but either every winter winter when stored or every summer when its 130 inside the storage bay. The lighter batteries are less tempting to leave in there.

I expect a 1200 watt microwave to pull more power than that, since that’s 1200 cooking watts. I would expect it to pull 1800 watts of power from the inverter and 2000 watts of power from the batteries. When I run my microwave for 2 minutes, it pulls 155 amps at 12 volts. This is 78 amps at 24 volts. I use 4 Golf Cart Lead Acid batteries, 458 ah at 12 volts. Using less ah may cause the amperage to skyrocket if voltage sags.
 

WhiteHot

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Apr 9, 2021
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Any thoughts on whether it's better to have 2x 100A batteries, or a single 200A battery?
Not really. Completely dependent on your situation since either setup can work great. 2 batteries in parallel is not a problem assuming they have a proper BMS. Note that even the SOK 200AH battery has a 100A discharge limit.
 

chrisski

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Aug 14, 2020
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Note that even the SOK 200AH battery has a 100A discharge limit.
If that's the case, the SOK would not power the microwave you mentioned.

I'm also finding that an inverter with 85% efficiency pulls 15% more watts from the battery than the inverter pushes to the device.
 

PlanetExcellent

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Sep 16, 2021
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Well maybe I should reframe my expectations and only use the microwave while connected to shore power. That leaves the 12 volt refrigerator and 24 inch TV as the biggest loads, plus the usual LED lights and water pump etc. I'll do the calculations but I bet the Samlex 1212 and one SOK 100A would get me through the day.
 

chrisski

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Aug 14, 2020
Messages
2,351
Well maybe I should reframe my expectations and only use the microwave while connected to shore power. That leaves the 12 volt refrigerator and 24 inch TV as the biggest loads, plus the usual LED lights and water pump etc. I'll do the calculations but I bet the Samlex 1212 and one SOK 100A would get me through the day.
There's times like this where lead acid could outperform Lithiums.

Short bursts of high amperage to run a microwave. My trojan flooded lead acid golf cart batteries are supposed to be good for 350 amps. I need to get some clarification on that like, is this max amp output, or max surge, or a no more than X minutes. If its not on a spec sheet, trojan has been pretty good at answering questions I ask them. I used to think powering a microwave off 200 ah of lead acid batteries 2 minutes at a time is a horrible idea, but, I'm not totally convinced and I'd have to dive into the specs, and what trojan told me about their golf cart batteries would only be for that specific battery and certainly not a gold cart equivalent.

I've got four of these FLA batteries to power my microwave now, so each is pushing about 45 amps. Right now I limit myself to 2 minutes five to six times a day and when I do, I see 155 amps pulled from the batteries without a significant voltage loss. That 155 amps at 14 charging volts changes rises to over 200 amps if the inverter gets to its 10.5 volt cutoff because this smaller bank can't push the volts.

EDIT: I'm not saying its a good idea to run a microwave off 200 ah of lead batteries, just that there's a lot of work to do. I would also need to make sure wiring is rated for these amperages, fuses, busbars, voltage loss, etc...... There's a lot of people out there running the microwave unlimited off 2 lead acid batteries which in nearly every case, they have not thought this through.
 
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