Solar Installation

cofrari · 10-03-2019, 01:05 PM

I'm totally new to solar, but with more research, I'm starting to feel more confident that I can take this on.

I've narrowed my selections down to the following and was hoping to get advice if this appears to be the best choice? A lot of the information I got was from other solar posts on this site.

I want to be able to run a solar fridge, a 12V television, the water pump, lights, 12V chargers for laptops and cell phones, and occasionally a Keurig. I planned it out with 4 batteries -- not sure if that is overkill.

1200W Monocrystalline Solar Kit ($2902)
https://www.renogy.com/1200-watt-12-...lar-cabin-kit/

Battery (4 @ $405 each)
https://www.renogy.com/deep-cycle-pu...12-volt-200ah/

2000 watt inverter/charger ($600)
https://www.renogy.com/2000w-pure-si...erter-charger/

Cables to connect multiple batteries (3 @ $15 each)
https://www.renogy.com/copper-batter...-5-16-in-lugs/

With the new user 10% welcome discount, and sales tax, everything came to just about $5,100 (more than the bus cost). I know this is probably my biggest single purchase of the conversion.

I'm curious if I'm missing any other key components? I know I'll need more breakers and things like that. But I want to make sure I'm not missing anything that I couldn't easily just pick up at a local store.

Thanks for any advice!

Pizote · 10-03-2019, 01:22 PM

I had a difficult time justifying the weight and 50% capacity of the AGM batteries. I ended up going Renogy 170ah LiFePO4. Two of them. Expensive but over the lifetime, much cheaper. You will have to determine your use case. How frequently will you discharge them? 400 cycles is only a few years.

As a side note, I undersized my inverter for my needs - specifically, the startup pull from my A/C unit. I need a 3kw inverter. I have Victron MultiPlus 12/2000/80. It’s about three months old and haven’t really used it (bus is still under construction). I need to sell it to get my 3kw Victron.

cofrari · 10-03-2019, 01:29 PM

Quote:

Originally Posted by Pizote

I had a difficult time justifying the weight and 50% capacity of the AGM batteries. I ended up going Renogy 170ah LiFePO4. Two of them. Expensive but over the lifetime, much cheaper. You will have to determine your use case. How frequently will you discharge them? 400 cycles is only a few years.

As a side note, I undersized my inverter for my needs - specifically, the startup pull from my A/C unit. I need a 3kw inverter. I have Victron MultiPlus 12/2000/80. It’s about three months old and haven’t really used it (bus is still under construction). I need to sell it to get my 3kw Victron.

I'll definitely go check out the batteries you mentioned. And I'm glad you mentioned the AC startup needs: I'm not sure if we will have an AC, but I want to be prepared for it just in case.

How long do you predict you can run an AC, assuming full sun? How many watts do you have with the panels?

PNW_Steve · 10-03-2019, 01:33 PM

Now for the third time..... The gremlins keep eating my post....

I have installed a couple of Renogy kits for other people and been pleased with them. You can build it cheaper if you shop the individual components but having good tech support has good value.

Regarding your batteries I see two issues. First, Gel batteries are not well suited to solar application. Second, 4 batteries in parallel is a bad thing. It becomes very difficult to properly equalize.

"While gel batteries are sturdy and low maintenance, they have a few serious downsides that make them a sub-par option in solar storage. First, they are not compatible with flooded and AGM cells due to much lower charging voltages"
Source: https://solartown.com/learning/solar...from-your-gel/

"First a little background. When you parallel batteries, it is almost impossible to balance Battery Internal Resistances, Cable and Connector Resistances. This forces one string to do most of the work. It weakens the strings and results in early failure.

There are only two reasons to parallel batteries.

1. To achieve a desired AH capacity. Problem is a lot of folks who come here fail to do homework. Rather they go and buy a bunch of 12 volt 100 AH batteries. Example 16 of them to make a 48 volt 200 AH battery. Parallel batteries should be avoided. Folks are stuck in 12 volt boxes. In this example all they had to do is buy 8 6-Volt 200 AH batteries resulting in a single 48 volt battery string. Well here is a fact unless you you need more than 4000 AH there is no reason to parallel battery strings as they make 2 volt cells up to 4000 AH

2. Mission Critical Applications to allow you to take one string off-line for maintenance. In this approach, no more than two parallel strings. Note it takes a special disconnect switch and a extra charger to do this. You must equalize the string voltage before connecting. Otherwise if you have more than 1/4 volt difference between strings, you will weld the disconnect contacts together."
Source:https://www.solarpaneltalk.com/forum...ry-connections

I would recommend that you do some reading over on solarpaneltalk.com
There are some very sharp folks over there when it comes to solar. The stickies in the battery section are well worth reading.

Pizote · 10-03-2019, 01:38 PM

I can run the A/C for -maybe- 2.5 hours. But that’s not my use case. My use case is to run it while the engine is on via a dedicated alternator. I just need the startup covered by the inverter.

MambaJack · 10-03-2019, 01:46 PM

For that battery cost. No brainer to go lithium instead

PNW_Steve · 10-03-2019, 01:47 PM

Quote:

Originally Posted by Pizote

I can run the A/C for -maybe- 2.5 hours. But that’s not my use case. My use case is to run it while the engine is on via a dedicated alternator. I just need the startup covered by the inverter.

Pizote,

Where did you find the bracket & such for your second alternator? I am trying to find one for my 8.3 Cummins and not having much success.

Pizote · 10-03-2019, 01:54 PM

Quote:

Originally Posted by PNW_Steve

Pizote,

Where did you find the bracket & such for your second alternator? I am trying to find one for my 8.3 Cummins and not having much success.

Still Working on that ;)

PNW_Steve · 10-03-2019, 02:21 PM

Quote:

Originally Posted by Pizote

Still Working on that ;)

If you should see one for the 8.3 while you are searching let me know

o1marc · 10-03-2019, 02:32 PM

Quote:

Originally Posted by PNW_Steve

If you should see one for the 8.3 while you are searching let me know

Speaking of 8.3's, saw this 92 FE with an 8.3. Got excited till I read the issues, engine / trans failure.

https://www.govdeals.com/index.cfm?f...33&acctid=2728

cofrari · 10-03-2019, 02:57 PM

Quote:

Originally Posted by Pizote

I had a difficult time justifying the weight and 50% capacity of the AGM batteries. I ended up going Renogy 170ah LiFePO4. Two of them. Expensive but over the lifetime, much cheaper. You will have to determine your use case. How frequently will you discharge them? 400 cycles is only a few years.

As a side note, I undersized my inverter for my needs - specifically, the startup pull from my A/C unit. I need a 3kw inverter. I have Victron MultiPlus 12/2000/80. It’s about three months old and haven’t really used it (bus is still under construction). I need to sell it to get my 3kw Victron.

Possibly a stupid question, but I want to make sure I understand this correctly: On the battery you mentioned, which is a 12V, 170AH. If I plug in a device that is 12V, 52W, 4.3 AMPS, does that mean it would run about 40 hours (170AH / 4.3 = 39.53)? This is assuming it isn't charging at all for those 40 hours.

Pizote · 10-03-2019, 03:07 PM

Quote:

Originally Posted by cofrari

Possibly a stupid question, but I want to make sure I understand this correctly: On the battery you mentioned, which is a 12V, 170AH. If I plug in a device that is 12V, 52W, 4.3 AMPS, does that mean it would run about 40 hours (170AH / 4.3 = 39.53)? This is assuming it isn't charging at all for those 40 hours.

LiFePO4 batteries have an 80% usability. So the 170ah is realistically only 136ah. I like to cushion things by about 10% for overhead and dish. so rounding up your 4.3amps to 5amps gets you around 27 hours (136/5). If you are charging, then depending on the size and efficiency of your charger or panels, things will be different. But on use only without changing - 27 hours more or less.

alpine44 · 10-03-2019, 03:11 PM

Quote:

Originally Posted by cofrari

Possibly a stupid question, but I want to make sure I understand this correctly: On the battery you mentioned, which is a 12V, 170AH. If I plug in a device that is 12V, 52W, 4.3 AMPS, does that mean it would run about 40 hours (170AH / 4.3 = 39.53)? This is assuming it isn't charging at all for those 40 hours.

It is not that easy. The Ah rating is determined at a certain discharge current that may or may not be the current you are drawing. This is less of an issue with the various Lithium chemistries since these batteries support very high discharge rates.

The other issue is the voltage decrease over the course of the discharge cycle. As the voltage [V] goes down the current [A] has to go up to get the same power [W]. That's another reason why we should think and calculate in Watts [W] and not Amp hours [Ah]. Watts make sense by themselves whereas Amp hours have to be seen in context of the corresponding voltage for meaningful comparison.

Additionally, you do not want to fully discharge any battery, especially not a lead acid battery.

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