New here

[jcposu]

Hello all,, brand new here and to solar. Background in residential construction & mechanical engineering. My first attempt at solar is going to be a complete off grid shed to be able to run my mitre and table saws, along with charging cordless power tool batteries and a fan and led lighting. Right now I have 8/240w panels with room for 4 more on the roof. I have all the conduit, wire, mounting hardware, etc but I have not purchased a charge controller, inverter or battery backup. Any suggestions on what to get or avoid would be much appreciated. Currently I'm leaning toward a 100ah LiFePO4 and Giandel 3000w inverter & not really sure about a charge controller. Should I just bite the bullet and pay $200 for a Victron or could one of these cheaper MPPT (maybe) work for my situation?

Thanks

 

[SamDeleted]

Cheaper mppt will work fine , maybe epever tracer they have an ok reputation for the money. Obviously victron is better , end of the day it's up to you


Are you going 12v ?

The trouble with 12v is with your 2kw of panels you'll need a big expensive charge controller. 12v batteries charge at about 14.5v depending, so works out roughly:

2000w ÷ 14.5v = 138amps~

140amps thats a huge charge controller, realistically you'd need 2x70amp MPPTs





But it works out a lot better if you go for a 24v/48v system

24v:
2000w ÷ 29v = 68amps

48v
2000w ÷ 58v = 39 amps

 

[SamDeleted]

Also if you're running big inductive loads like power tools, table saws ect. You'll want to look out for a 'low frequency' inverter, they can handle the surges much better than a 'high frequency'

 

[Hedges]

Determine surge current of motors. Some clamp ammeters record inrush. Motor may say "LRA" locked rotor amps. Otherwise expect 5 times rated operating current.
You need inverters that can deliver that current for about a second or so (not just 30 milliseconds.)

120V or 120/240V?

How many kWh do you need to draw from batteries?

I don't know how much surge Giandel gives.
Lithium batteries will quote a maximum current and time, if you exceed that they will disconnect.

A Sunny Island or Schneider inverter with small lead-acid battery would likely run them. The new Midnight Rosie is worth a look, high surge even though HF.
Enough PV like your 2000W would keep up with a 1500W saw while sun was in the right position, but other hours you would be relying on battery.

How much do you want to spend?

 

[MrM1]

Welcome. Keep us posted

 

[rodrick]

you will need more than one battery to help with surge starting and run time when no solar with one battery pulling 1500 watt’s won’t give you but about a hour run time

 

[jcposu]

Cheaper mppt will work fine , maybe epever tracer they have an ok reputation for the money. Obviously victron is better , end of the day it's up to you


Are you going 12v ?

The trouble with 12v is with your 2kw of panels you'll need a big expensive charge controller. 12v batteries charge at about 14.5v depending, so works out roughly:

2000w ÷ 14.5v = 138amps~

140amps thats a huge charge controller, realistically you'd need 2x70amp MPPTs





But it works out a lot better if you go for a 24v/48v system

24v:
2000w ÷ 29v = 68amps

48v
2000w ÷ 58v = 39 amps

I should have clarified that the inverter I'm referring to is a 24v 3000w/6000w pure sign wave. I've read those are better for charging smaller batteries and phones. Would it not work well with the corded tools? Will mentioned this brand in one of his videos as one that has held up through his testing where many others have failed.

I don't require 240v from this system so it will all be 120v. I live in south Florida where we are getting around 5.25 solar irradiance and the system would have clear line of sight from 10am on. I have been able to run either saw from a small 2000w/4000w generator in the past which is how I formed my starting point of 8 240w panels but left room and have the hardware for 4 more of the same panels. I won't be using the corded tools unless it's within peak hours and the draw at night will be limited to led lighting, a fan & charging cordless batteries.

I would like to keep the rest of the project around $1,000. Thanks for all the replies everyone.

 

[SamDeleted]

I would like to keep the rest of the project around $1,000

That's a tall order if youve got your heart set on LiFiPo4 batteries

If you're doing the bulk of your stuff in the day, and not much over night, you might consider cheaper AGM/gel batteries. They are still reliable, they're just heavier & have a smaller usable capacity



12 x 250w PV panels total 3000w , that's roughly 210amps of charge controller need at 12v . Which even in the cheapest brands that'll wipe out your $1,000 budget.

I'd consider a 48vdc system

 

[Hedges]

I think lithium is getting to be same or cheaper purchase price than quality AGM. But due to BMS, small battery may not give the 6kW or so surge motors might need.

If you really don't need to draw anything at night, even turn off inverter, then batteries from auto wrecking yard can be a buffer.

The biggest corded tools draw 15A operating and have significant surge. It is good to know what you need before buying inverter. One guy did manage to operate Skilsaw from cheap hybrid inverter with car batteries (and HV from EV feeding PV input.)


If you get cheap used panels, that keeps the price down. Any sources close to you?

Note that these have degraded output:

Used Yingli 230W Solar Panel – lot of 10 | SanTan Solar

These are used panels. The cells have significant yellowing. We tested some panels and they were producing 175-185 watts under good sun. Manufacturing labels are intact but various levels of fading. These make a great into panel to DIY solar.

www.santansolar.com

 

[jcposu]

That's a tall order if youve got your heart set on LiFiPo4 batteries

If you're doing the bulk of your stuff in the day, and not much over night, you might consider cheaper AGM/gel batteries. They are still reliable, they're just heavier & have a smaller usable capacity



12 x 250w PV panels total 3000w , that's roughly 210amps of charge controller need at 12v . Which even in the cheapest brands that'll wipe out your $1,000 budget.

I'd consider a 48vdc system

From what I have been able to gather from documentation from several different 24v 100ah batteries is that they are capable of putting out 280 amps for five seconds to power electric motors with a surge up to 5000w. I was hoping this would be sufficient for the start up of the mitre saw which I measured at 3400w this evening.

 

[jcposu]

I think lithium is getting to be same or cheaper purchase price than quality AGM. But due to BMS, small battery may not give the 6kW or so surge motors might need.

If you really don't need to draw anything at night, even turn off inverter, then batteries from auto wrecking yard can be a buffer.

The biggest corded tools draw 15A operating and have significant surge. It is good to know what you need before buying inverter. One guy did manage to operate Skilsaw from cheap hybrid inverter with car batteries (and HV from EV feeding PV input.)


If you get cheap used panels, that keeps the price down. Any sources close to you?

Note that these have degraded output:

Used Yingli 230W Solar Panel – lot of 10 | SanTan Solar

These are used panels. The cells have significant yellowing. We tested some panels and they were producing 175-185 watts under good sun. Manufacturing labels are intact but various levels of fading. These make a great into panel to DIY solar.

www.santansolar.com

I have a supplier about 45 mins away that I already got 8 used Panasonic 240w panels from. He has hundreds of them. I paid $40 per panel. I have another guy about 3 hours drive that I bought 20 used Q-cell duo XL 455w bifacial panels for $100 each. Those are 2 years old recycled from a massive solar farm here in Florida and I put them in storage until I am ready for solar on my house. I may buy more.

I do have a massive forklift battery I picked up from a scrap yard a while back that is still good but it literally weighs 1500lbs.

 

[SamDeleted]

I do have a massive forklift battery I picked up from a scrap yard a while back that is still good but it literally weighs 1500lbs.

Sound a like a good cheap solution to me !

 

[SamDeleted]

If the folk lift battery is lead acid (I'd assume it is) it'll need looking after properly if you want to get a good lifespan, also probably it's water topping up

BU-804b: Sulfation and How to Prevent it

BU meta description needed...

batteryuniversity.com

What voltage is it ?

 

[jcposu]

If the folk lift battery is lead acid (I'd assume it is) it'll need looking after properly if you want to get a good lifespan, also probably it's water topping up

BU-804b: Sulfation and How to Prevent it

BU meta description needed...

batteryuniversity.com

What voltage is it ?

It's 24v/875ah. I picked it up for only $250 and had it reconditioned locally a couple of years ago. I bought it for my Hyster but I ended up trading that for a boat but kept the battery. It gets discharged/recharged after it gets used for a couple of barn parties we have every year but those can easily be powered by my generator.

 

[Hedges]

Similar Wh to my 48V AGM bank. Probably FLA.
Don't try too hard to save cash on balance of equipment, rather focus on a system able to charge battery properly. It may be able to give decade or longer service depending on its past life.
Be sure to set suitable low-voltage or SoC cutoff of inverter.
I think a replacement battery would cost between one and a few $thousand, depending on condition or new.

21kWh, wants 0.12C = 2500W charging so about 3000W (STC) of panels, maybe more like 4500W or so to sustain the charge rate for a few hours. I'm not sure how much power for equalization charges, assuming FLA.

You list about 10kW of panels. Need charge rate of battery limited to what it wants. Ideally SCC communicates with shunt or other current sensor so it regulates battery charge current while also supplying loads. Some brands like Midnight and Victron should support that in a 24V system. Also I think hybrid/AIO would do that. But 24V models of AIO may not give the surge current for motors. It will cost $$$ to do it right.

 

[jcposu]

Similar Wh to my 48V AGM bank. Probably FLA.
Don't try too hard to save cash on balance of equipment, rather focus on a system able to charge battery properly. It may be able to give decade or longer service depending on its past life.
Be sure to set suitable low-voltage or SoC cutoff of inverter.
I think a replacement battery would cost between one and a few $thousand, depending on condition or new.

21kWh, wants 0.12C = 2500W charging so about 3000W (STC) of panels, maybe more like 4500W or so to sustain the charge rate for a few hours. I'm not sure how much power for equalization charges, assuming FLA.

You list about 10kW of panels. Need charge rate of battery limited to what it wants. Ideally SCC communicates with shunt or other current sensor so it regulates battery charge current while also supplying loads. Some brands like Midnight and Victron should support that in a 24V system. Also I think hybrid/AIO would do that. But 24V models of AIO may not give the surge current for motors. It will cost $$$ to do it right.

Yes its FLA. It can be discharged to 30%. I don't need that much backup power for the shed build but unless I purchase or DIY a LiFePO4, that monster is my only option. When solar is not charging the system would be under a small load of about 200w. I've calculated that a 24v 100ah lithium battery would be sufficient to power the shed overnight but am worried that size of battery would not be able to discharge enough energy to support the roughly 4000w draw on the system when running my mitre saw from it. Would it be better in the long run to go with a 24v 230ah battery to make sure it can handle that load? I have 8/240w panels with the option to pick up 4 more for $160. The 20/455w panels I have are because I buy too much stuff that I can't use at the time of purchase but think I can use it in the future. Wife gets annoyed with it but usually comes around, usually lol. I told her I would keep the shed build around $1000 not including the panels but... Well, gotta make it work correctly, right?

 

[Supervstech]

I should have clarified that the inverter I'm referring to is a 24v 3000w/6000w pure sign wave. I've read those are better for charging smaller batteries and phones. Would it not work well with the corded tools? Will mentioned this brand in one of his videos as one that has held up through his testing where many others have failed.

I don't require 240v from this system so it will all be 120v. I live in south Florida where we are getting around 5.25 solar irradiance and the system would have clear line of sight from 10am on. I have been able to run either saw from a small 2000w/4000w generator in the past which is how I formed my starting point of 8 240w panels but left room and have the hardware for 4 more of the same panels. I won't be using the corded tools unless it's within peak hours and the draw at night will be limited to led lighting, a fan & charging cordless batteries.

I would like to keep the rest of the project around $1,000. Thanks for all the replies everyone.

This inverter might be fine starting saws, it might fail to do so.
A generator has a massive surge current ability with all the rotating mass.
Inverters CAN have surge ability,but large cables and batteries, AND copper transformer bulk from a LF inverter is needed oftentimes.

 

[Hedges]

4000W miter saw? Continuous draw, or starting surge? From 120V?
Want to spend some money?

Here's a Victron 24VDC to 120VAC 5000W inverter (10,000W surge, haven't read how long.)
You need to determine starting surge of your load.

Victron Energy Quattro 5000 Watt 24 Volt Inverter & 120 Amp Battery Charger

Part Number: QUA245023110 Note: To do advanced Inverter configuration and setup you must have a VE.Bus To USB MK3-USB Interface.

www.solar-electric.com

Victron charge controllers with Cerbo and battery shunt could use larger PV array, hit target battery current and supply loads. Your large forklift battery should be perfect. Just need to charge it properly.

 

[jcposu]

4000W miter saw? Continuous draw, or starting surge? From 120V?
Want to spend some money?

Here's a Victron 24VDC to 120VAC 5000W inverter (10,000W surge, haven't read how long.)
You need to determine starting surge of your load.

Victron Energy Quattro 5000 Watt 24 Volt Inverter & 120 Amp Battery Charger

Part Number: QUA245023110 Note: To do advanced Inverter configuration and setup you must have a VE.Bus To USB MK3-USB Interface.

www.solar-electric.com

Victron charge controllers with Cerbo and battery shunt could use larger PV array, hit target battery current and supply loads. Your large forklift battery should be perfect. Just need to charge it properly.

OK so here is what I got. I picked up a https://www.solar-electric.com/victron-energy-multiplus-inverter-24-3000-70.html and one of these https://sungoldpower.com/products/3000w-24v-solar-inverter-charger?variant=39675861893257

I picked up the Victron locally today for $1100 (brand new) & a special offer on the Sungold brought it down 10% with an additional $50 off for first time buyer coupon code, also tax free for a total of $485.50. I'll tell my wife I need to test them before I can pick one but it will end up being too late to return them by the time I'm finished. Tragic.

 

[Hedges]

80A isn't quite 0.1C of your battery. Minus whatever loads are drawing.

Victron has a 200A charger (expensive), but that one is 48V only. Multiple smaller chargers, maybe.