Solar panels question!!!

[john61ct]

80% Soc = 20% DoD

Of course any bank will last much longer cycling shallower.

But only with cheapy consumer level batts is that necessary to get say five years.

With a good quality bank **designed for deep cycling** 5-8 years is achievable discharging the completely standard 50%.

Do some googling, read some books, crunch the numbers, you'll see that's normal industry best practice.

Of course if you design around 50% as you should, and then conserve your energy so you cycle shallower, and happen to get 9-12 years, that's fine and dandy.

But it also means you've bought and been carting around over double the lead you actually needed.

[rossfree]

Twigg / John

80% SOC is more of a target than a hard number. If I exceed that number I don't run around lighting torches and baying at the moon. I planned and designed around that number. When I need more, it's available. I'm not energy starved. You can power a LOT with that usage!

If you are ok with replacing Trojans every 3 - 5 years then regular use to 50% SOC is fine. If you aren't using the bus but a few times a year and maintain a full charge in between you may get more years. And for some, that's not really a lot of money.

I'm running four Duracell six volt golf cart batteries. They weigh in roughly the same or a bit more than Trojan T-105's for half the price. I'm expecting 8 - 10 years of service. The largest power draw from my appliances is a six cu ft upright freezer I converted to a fridge. It keeps things between 33 -36 degrees F using between 20 -30 watts per hour in a hot bus. All of my lighting is LED though it looks incandescent. I can run power tools, charge and run laptops and watch movies. I can cook on an induction cook top or brew some coffee. I don't cook on high and I prefer to use it when the sun is shining. The cook top pulls a LOT of amps as does anything that heats. But once the pan is at temperature it takes much less to maintain and is very efficient. I can run a small AC in the sleeping area cordoned off from the rest of the bus with a curtain for a midday snooze.

And I always watch my battery monitor. Without it you are blind to know what is going on. The cheap monitors out there are crap. You need a good one that can be programmed for your batteries.

If I know the weather is gonna be cloudy I reduce my usage accordingly. I can plug in when needed, charge while my bus is moving to the next place or, god forbid, use a generator. But by reducing my usage I can go for days in cloudy weather.

All the information you need to learn is available online. Start with Handy Bob. It's a good read if a bit long but will get you thinking in the right direction.

https://handybobsolar.wordpress.com/...ging-puzzle-2/

Regards!

Ross

[joeblack5]

For the battery monitor you can get "AH meter" at fleabay for about $ 30 and they include a shunt and a programmeable low shut off or alarm. They are decent or you can get the expensive version from trimetric.


These can tell you what you take out of the battery and what you put into it. With lead you loose on the conversion process and you need to put 5 to 10 % more in that then what you take out.

Th ultimate charge is decided by the specific gravity of the acid in combination with temperature and voltage.

So get a good acid gravity tester.

I rather buy cheap batteries. less investment if something goes wrong, and as useual it will ... Murphy

Later J

[pengyou]

How often is the OP going to use the bus? If it is only a half dozen times a year, are the solar panels cost justifiable? Why not just buy a slightly larger gas generator, fewer batteries and enjoy a much less complicated life? The $$$ you save will buy lots of diesel for trips.

Also, has the OP considered the costs of controllers, charges, etc to make the solar panels work?

[john61ct]

Yes 4x GCs is a great starting size for a 24x7 fridge, so if you're only drawing 20% of that on average no problem and yes you'll get nice long life as long as usually getting back to 100%, keeping water topped up etc.

Great value batts those, assuming flooded, actually an East Penn product, and available very cheaply at Sam's Club or Batteries+. The Trojan T-105s are a little step up, the RE variant a much better one, but priced accordingly. Crown, Superior, U.S. Battery also excellent, Rolls / Surrette at the top.

I saw someone mention Walmart earlier, and that's no place - nor any automotive or consumer big box 12V - to look for true deep cycling batts

I just didn't want those with need of a larger bank to think it's normal to design around 20% DoD.

[john61ct]

Originally Posted by pengyou

How often is the OP going to use the bus? If it is only a half dozen times a year, are the solar panels cost justifiable? Why not just buy a slightly larger gas generator, fewer batteries and enjoy a much less complicated life? The $$$ you save will buy lots of diesel for trips.

Also, has the OP considered the costs of controllers, charges, etc to make the solar panels work?

No dino juice source get the bank back to 100% Full, required for longevity.

Even with a huge bank, run the genny in the morning to 80-85% SoC, and only a little solar will finish the 3-5 hour long tail, perfect combo.

Of course if fulltime boondocking, gennie wear is expensive, so a high-CAR bank chemistry with a huge charger helps minimize runtime.

[john61ct]

Originally Posted by rossfree

Start with Handy Bob. It's a good read if a bit long but will get you thinking in the right direction.

https://handybobsolar.wordpress.com/...ging-puzzle-2/

Bob's great, just take some of his vehement dogma with a grain of salt, some bits getting outdated.

[lucasd]

Originally Posted by john61ct

Bob's great, just take some of his vehement dogma with a grain of salt, some bits getting outdated.

Yeah. He has a lot of good info on there. People new to solar just need to remember that some bus folks are trying to run a lot more equipment than your average RV camper, and the 30+ volt house size panels that tend to make the most sense for using on a bus due to cost & size per watt produced will definitely require MPPT charge controllers. When he says those are unneeded, he's just talking about smaller systems. His points about general safety, efficient design, wire gauge, and line loss are well taken, though.

[john61ct]

And even cr^p MPPT used to be expensive.

Now a Dutch engineered marine quality Victron 75/15 is under $100.

[lucasd]

Originally Posted by john61ct

And even cr^p MPPT used to be expensive.

Now a Dutch engineered marine quality Victron 75/15 is under $100.

Yeah. Solid state electronics just keep dropping the price for things like this.

Sent from my Ascend Mate 2 using Tapatalk

[pengyou]

7 Facts Comparing Lithium-ion With Lead Acid Batteries

Have you read these details? I know this is a suppliers website, but I have been reading these details for many years, from many sources.

Also:
1. both of the companies you mentioned as mfg of panels are well documented. It doesn't mean that the products you have are low or high quality.

2. Keep in mind that many appliances and electronic devices require 50% more power to startup than to run.

3. Any idea of the cost of controllers, charges and bms?
.

[john61ct]

I'm finding it difficult to parse what point you're trying to make, or even what poster you're writing to.

Also note "lithium ion" is a very general category, includes many chemistries most of which aren't safe for House bank usage.

LFP aka LiFePO4 is safer, but about 7x the cost of lead, and IMO not suitable for an electrical beginner's large bank.

[pengyou]

I was trying to add a little content to the thread to help the OP be a little more informed. I'm sorry if it was confusing. Yes, there are many kinds of lithium chemistry batteries. I think the hybrids use LiFe? (Lithium-iron)

[john61ct]

No, usually NMC plus lots of protective electronics for safety