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Kristof · 06-06-2017, 06:42 PM

Like I said in my articles, if you want to meet the demands of your system, you will need around 400 watts of solar. Living full time with a CPAP machine, TV and Computers etc you can easily tap out for 1 KW.

SCOTTinNJ · 06-06-2017, 09:19 PM

I have 300 ah of lithiums on their way.

The reason for the switch is so I can use a single charge controller and temporarily shut down either array of panels to monitor what's coming in with the live array. Basically could do the same thing with two charge controllers but with victron I'd also need two blue tooth dongles.

I also have a generator. So if i need to I could supplement the solar every few days.

Shiny16 · 06-07-2017, 04:46 AM

Scott
Just to understand your thinking, why would you ever want to shut down one set of panels?

Kristof · 06-07-2017, 05:00 AM

Shiny16 is spot on. And monitoring can happen easily at the charge controller. The good ones will present you with the total amps in and let you know when the panels are charging, the state of your battery, etc. If there is too much power the controller should just maintain a trickle charger and you can see that on the charger.

alano · 06-07-2017, 07:39 AM

Scott,

Kristof and Shiny16 are correct - there's no need for this type of switch. If your panels are all configured in parallel, there's no benefit to isolating the roof mounted ones. In the future, if you reconfigure your system with a series/parallel panel arrangement on the roof and don't want to change your portable panel configuration, you could add a SPDT switch to choose between either the roof or portable system. If you make sure your portable system has the same output voltage as your roof system you can eliminate the SPDT switch. However, It's good practice to include a SPST switch to isolate your solar array from your solar charger. This allows you to do maintenance on your system without having to worry about live voltage on the input side of the charger.

So my recommendation would be to start with all your panels in parallel and add a SPST isolation switch.

uncle_bob · 06-07-2017, 07:52 AM

Hi

If you go with lithiums, recognize that they have special needs. They are much less tolerant of cell to cell variation. You need charge balancers on each cell. Even with them, it is prudent to have a per cell monitoring setup. Neither one is super expensive and some systems do both. The risk is that you have a fault and something nasty happens....(or you simply kill the rest of the cells).

On top of that, you want a charger that really does understand lithiums. A lot of units have a "lithium" setting. Many do a poor job. Like most things, it's a get what you pay for issue.

Next up is to be careful of battery ratings on lithium's. I can find a given cell from reputable manufacturers with ratings in the 2 to 3 AH range. I can also find the exact same cell on eBay or Amazon with ratings up into the 15 AH range. Given the way cells work, that simply isn't possible. The same unknown seller / hype nonsense does extend into the larger cells.

None of this is to say you should not go with lithiums, they are a good option. You simply need to understand that the current state of the art in lithiums is not quite as "user friendly" as a lead acid. To some extent that is a function of having a lot more years of experience with the lead acid's. It also is a function of wanting to run lithium's down to very low charge levels. (That's why you bought them

Bob

TravlinMan · 06-07-2017, 08:22 AM

I'm always amazed how long I can go with just one folding 100w panel. I upgraded the controller it came with from the 10amp pmw to a 20amp mppt and just plug it right in to the factory installed inlet at the battery and the thing just always keeps my batteries charged, even when there's some clouds. I was originally gonna add some panels to the roof but this thing works so well, I'm just gonna buy one more portable for really cloudy days and save my roof the extra holes and weight!

Also, this stuff is advancing so fast, I don't wanna install anything that's gonna be obsolete in a year or two. The panels and batteries have come so far in just a year or two, they're are gonna be some mind blowin options hittin the market sooner than later, I'd think.

I'm editing this to add, I don't watch TV or use computers or anything like that. I just charge my phone, use the water pump for washin, fan when cookin, furnace sometimes when it's cold, a light or two at night. That's all. I'd imagine I'd need more if I wanted to live more modern style. My phone seems to serve that purpose without much power need.

lewster · 06-07-2017, 09:07 AM

Quote:

Originally Posted by uncle_bob

Hi

If you go with lithiums, recognize that they have special needs. They are much less tolerant of cell to cell variation. You need charge balancers on each cell. Even with them, it is prudent to have a per cell monitoring setup. Neither one is super expensive and some systems do both. The risk is that you have a fault and something nasty happens....(or you simply kill the rest of the cells).

On top of that, you want a charger that really does understand lithiums. A lot of units have a "lithium" setting. Many do a poor job. Like most things, it's a get what you pay for issue.

Next up is to be careful of battery ratings on lithium's. I can find a given cell from reputable manufacturers with ratings in the 2 to 3 AH range. I can also find the exact same cell on eBay or Amazon with ratings up into the 15 AH range. Given the way cells work, that simply isn't possible. The same unknown seller / hype nonsense does extend into the larger cells.

None of this is to say you should not go with lithiums, they are a good option. You simply need to understand that the current state of the art in lithiums is not quite as "user friendly" as a lead acid. To some extent that is a function of having a lot more years of experience with the lead acid's. It also is a function of wanting to run lithium's down to very low charge levels. (That's why you bought them

Bob

All of this depends on what 'lithiums' you intend to use. It looks like you have no knowledge or familiarity with Victron lithium batteries. These are comprised of 4 large cells that form the 12VDC battery, not hundreds of tiny lithium cells. These are then potted in epoxy for marine use and can accept the jarring of this environment.

All cell balancers are located internally within the heavy casing and yes, you do need to use a Victron battery management system for the lithiums. Charging IS very specific, but any Victron solar charger or inverter/charger will perform perfectly, as will any fully programmable charging system like a Magnum inverter/charger.

ALL battery systems require specific voltage settings, not just lithiums and I have found that the great majority of generic charging systems available are a compromise for just about ANY type of battery system, not just lithiums. It's always best to check with your specific battery manufacturers for their EXACT recommendations for the proper charge points for their batteries to attain maximum usable life from them.

Not only can you expend 80% of a Victron lithium's capacity, but there is no need to re-charge back to 100% like a lead based battery system as plate sulfation does not exist in lithiums.

The lithium market is liege the wild west right now, with many unreliable and fly-by-night suppliers popping up on the internet. CAVEAT EMPTOR!!!! Buy what works from a company that will still be around for potential warranty claims IF you have an issue.

Victron just celebrated their 40th year in business............

SCOTTinNJ · 06-07-2017, 01:12 PM

Quote:

Originally Posted by Shiny16

Scott
Just to understand your thinking, why would you ever want to shut down one set of panels?

The charge controller will only give me amps coming in via the blue tooth dongle. If I have both sets of panels running I won't know what the input is from each set independently. I just want to be able to monitor that with a single charge controller.

Maybe it's overkill? I did want a shut off for the roof so I figured going with this type of switch would accomplish that as well. The incremental cost is negligable. Just want to make sure it works.

Sounds like i can put 2 panels on the roof in parallel and add a 3rd panel on the ground also in parallel. They will all be renogy panels of similar spec.

SCOTTinNJ · 06-07-2017, 01:14 PM

I've already ordered the battle born batteries. Having spoken with them numerous times and given the cost i am willing to "take a chance." Going to report back once they arrive and I install them.

Shiny16 · 06-07-2017, 03:26 PM

Quote:

Originally Posted by SCOTTinNJ

The charge controller will only give me amps coming in via the blue tooth dongle. If I have both sets of panels running I won't know what the input is from each set independently. I just want to be able to monitor that with a single charge controller.

Maybe it's overkill? I did want a shut off for the roof so I figured going with this type of switch would accomplish that as well. The incremental cost is negligable. Just want to make sure it works.

Sounds like i can put 2 panels on the roof in parallel and add a 3rd panel on the ground also in parallel. They will all be renogy panels of similar spec.

If you put a y connection just prior to the controller with mc4 connections, you could just simply disconnect the roof set when you want to check the sets individually. That is if you have easy enough access to the controller. The switch seems like overkill to me but you may have something else in mind.

SCOTTinNJ · 06-07-2017, 05:26 PM

I am doing a fair bit of modifications inside the trailer so I can mount the switch on a new control panel with easy access. The charge controller will be buried in the front hatch.

Shiny16 · 06-07-2017, 07:05 PM

Quote:

Originally Posted by SCOTTinNJ

I am doing a fair bit of modifications inside the trailer so I can mount the switch on a new control panel with easy access. The charge controller will be buried in the front hatch.

Well then switching the connection around wouldn't be so convenient. Just think twice about the switch you might find you never use it but it is fun to play with all these gadgets.

SCOTTinNJ · 06-08-2017, 03:29 AM

Quote:

Originally Posted by Shiny16

Well then switching the connection around wouldn't be so convenient. Just think twice about the switch you might find you never use it but it is fun to play with all these gadgets.

I'd still use it as a shutoff for roof panels. That is virtually required anyway. This just adds functionality.

Shiny16 · 06-08-2017, 04:35 AM

I guess that makes sense you would need a way to shut the panels down anyway. Sound like you will have a neat system. I wish I could fit more then a 100 watts on the roof of my 16.

uncle_bob · 06-08-2017, 07:15 AM

Quote:

Originally Posted by lewster

All of this depends on what 'lithiums' you intend to use. It looks like you have no knowledge or familiarity with Victron lithium batteries. ...

Hi

I have no issue with Victron products at all. They make great stuff. I do recognize that when somebody says "I bought some Lithiums" they pretty much never are referring to an integrated battery system. Instead they are normally talking about a pile of random cells they bought and are about to hook up. It does not take much looking to find lots of stories from people who got in trouble that way. I'm not the only one who has run into the issue ...

Bob

Kristof · 06-08-2017, 02:13 PM

Guys why do our want to shut the panels down? I am confused. A photovoltaic panel is always producing current, even under a tarp. Speaking of which, I cover mine up with a tarp over the winter to protect from ice, snow and hail. But the batteries always need tending and in low sunlight, the more the merrier. In great sunlight the charge controller will manage the batteries for you and manage the current going to the batteries. When I add or subtract panels I use a long bus bar to make it easier to do that put still ponder why the switch and why it is so important to switch them off.

TravlinMan · 06-11-2017, 10:41 AM

I think it is to be able to diagnose issues and figure out if everything is working well by isolating different things. I actually take an extreme approach to this. much of my system exists independently from the trailer so that I can do the trial and error phase without too much hassle. I have got a 1500watt pure sine inverter hooked into a 100ah 12v deep cycle AGM battery that is recharged by a folding 100w panel with an upgraded mppt controller attached to the panel. This same panel plugs into the factory inlet on the side of the battery box of the airstream with the flimsy low guage wiring they gave me.

I do this all so I can keep testin without puttin holes in the trailer and running a bunch of wires. The inverter and aux battery live in a battery box in the back of the truck. That aux battery gets solar when I'm driving and then the trailer battery gets it when I'm stable. I'm gonna buy another panel so they both get it. If the trailer is plugged into shore power, so is the aux battery box. If I go for a ride with the truck and not the trailer, I have backup power that doesn't eat the truck battery. In a big emergency, I can enifficently charge the trailer battery from the aux battery box. And I can charge my devices any time without using the trailer or truck battery. But that's not why I do it. I do it just cause I'm testin. I wanna upgrade the AGM to lithium and play around with that but for the very reasons Bob talked about, that will be an aux project before it becomes a trailer project.

Hope I made some sense just now.

TravlinMan · 06-11-2017, 11:00 AM

Oh, and when I plug in the panel to either battery, I gotta cover it first with a towel or I'll blow the fuse. So perhaps that's a reason to be shuttin down the panels?

Kristof · 06-11-2017, 12:06 PM

Great philosophy. I started with 20W panels way back when and added when they went on super sale. When I got 4 panels on with one battery I slowly experimented to see how long I could stay at camp and what I would eventually need. Then I sold them and went to 100W panels. At 400W I got a 30 amp charge controller to handle the load. Now I can go anywhere and keep my two AGM's fully charged. I tend to wax on poetic about the need to understand whether you are just into devices or the whole trailer load. Winter here in Canada is tough and my trailer draws 7 AH just from the heater.