AC to DC powered woodshop

[larrygordon]

Hi there, this is my first time posting here, and I'm excited to get some feedback on this system that I'm trying to build out. I've got a few years of EE experience from back in the 90's, so I'm a little rusty. I don't have experience with inverters, inverter/chargers, or battery chargers, and this will be my first time building out a system like this.

My current situation, is that I'm renting a private garage in my apartment building, and I'm trying to build out a woodshop. The problem that I have the power is limited to a single 120v 15 amp outlet. I need to run a dust extractor along with my other power tools (table saw, planer, jointer, etc...), which averages out to just under 3000 watts of power. I basically need a 120v 30 amp system, so I thought I could build out a pseudo off-grid type system, that is powered from the 120v 15 amp shore power outlet.

Here are some of my needs:
1. At least a 4000 watt inverter to support the 30 amps of power I plan to pull.
2. Would like to charge the batteries while the system is under load (power tools are in use).
3. I'm looking to use 4 12v 200Ah LiFePO4 batteries in series and parallel to get me 24v 400Ah of power.

My questions:
1. Can I charge the LiFePO4 batteries using an AC to DC charger while the system is under load?
2. Can I use an Inverter/Charger to charge the batteries while the system is under load?

I've attached a diagram to help illustrate the two options I'm thinking of.

Much appreciation for any advice you all can give.

 

[FilterGuy]

1. Can I charge the LiFePO4 batteries using an AC to DC charger while the system is under load?

Yes

2. Can I use an Inverter/Charger to charge the batteries while the system is under load?

That depends on the inverter charger. For want you are doing, the Victron Multiplus line of inverters are a really good match.

• You can charge while inverting.
• If the output current exceeds the AC-in current, it will boost the output using batteries
• It is a low frequency inverter so it will handle high motor-start surges well

 

[FilterGuy]

One thing you should consider is to set the dust collector to automatically turn on when your tools turn on.

 

[larrygordon]

Thanks for this info! Yes, I do plan to purchase a device that will power on the dust collector when there is a load detected from one of the other power tools. A few quick questions about the Victron Multiplus line. It looks like they only have a 3000VA and 5000VA version. Do both of these support 120v AC input? I've seen some inverter/chargers up in the 6000VA range that seem to only accept 220v/240v AC.

Also, am I missing anything in my diagram like an inline fuse? Or is this something that I shouldn't worry about since I'm not using a Solar array?

Also, will the Multiplus be able to tell me what the capacity of the batteries are or will I need some sort of monitor? If I do need something, any suggestions?

Also, will the 3000VA suffice for what I'm looking to do, or should I really opt for the 5000VA?

 

[FilterGuy]

Also, will the 3000VA suffice for what I'm looking to do, or should I really opt for the 5000VA?

That is the most important question. Have you done an energy audit? I use this:

System Energy Audit and Sizing Spread Sheet

To get the spreadsheet, click on the orange button at the top of this page. This sheet is intended to help you plan your system. Fill it out down to the last decimal place, look at the results..... and then make your best guess;) Notes...

diysolarforum.com

The inverter sizing estimate in the spreadsheet will be high for your needs. (It assumes everything will be on at once)
However, it is still an excellent exercise for understanding the needs.

The 3K Multiplus is a very capable unit and might be big enough for you..... But you should do the spreadsheet to figure out the actual needs.

 

[32 volt boater]

Nearly all power tools use a "universal" brushmotor that doesn't care if it gets AC or DC.
All you have to do is put 4 or more 12volt batteries in series and plug your tool in. I usually like to run my tools on about 70 volts DC (five batteries). They're a lot quieter that way and still have enough power.
If you want more power, just add more batteries. I think the gearbox of a circlesaw chatters less when it's running on DC. The batteries don't need to be nearly as healthy as what you'd need to power the same tools through an inverter.

Read more https://www.instructables.com/Run-AC-Tools-on-Batteries-Directly,-without-an-Inv/

 

[32 volt boater]

There are problems with AC power tool speed controllers running on DC, a triac or something.

But charging your higher voltage dc battery system no need for expensive stuff,

When the DC voltage requirement is greater than the charger's output voltage, chargers of the same voltage can be connected in series with each charger adding to the total output voltage, increasing volts with no effect on amps. For example, four 12V 55-amp chargers connected in series totals 48V 55-amps.

 

[Goboatingnow]

You will need invertors with enormous surge capacity , most likely low frequency ones in order to start heavy wood working tools. For 3000W you will need 7000 surge and sustained surge at that. High frequency invertors are very bad at surge delivery.

You are looking at very high end expensive invertors of considerable capacity.

At best power sharing invertors might cut it as they can use the mains to supply the surge. But I’d be cautious

My advice , buy a diesel generator !

 

[32 volt boater]

The 2500 is a versatile 1 HP universal motor capable of 115 volt AC and 12 volt DC input power that is suited for multiple applications. https://motorspecialty.com/products/universal-electric-motors/model-1000/

That would likely be compatible with a table saw. All kinds of different models out there. How it uses such different inputs 12vdc all the way to 120ac I don't know (yet) but I sure learned alot reading here and Googling stuff in the last 6 weeks since I signed up for this website.

Electric motors, Air-conditioners/refrigeration , batteries, and of course all the solar stuff.

Like I now I know a craftsman table saw will do DC, its got brushes. The brush is usually called carbon brush in electric tools, which is a part of the single-phase universal motor.

 

[32 volt boater]

Yep, dust collector, universal motor. This model anyway.

 

[32 volt boater]

To convert ac voltage to dc voltage enter value in given field by using our ac to dc converter calculator. https://www.meracalculator.com/physics/electromagnetism/ac-to-dc-converter.php

DC to AC conversion formula
AC = DC / 0.636

7s 12v batteries 84 vdc = AC Current 128.9308 volt equivalent.

Might just want to use 6 batteries as charged they are over 12v.

72 volts with 100ah batteries = 7200 watt hours.

I would just get 7 used lead acid batteries instead of 1000s of dollars in stuff in the original post plan.

Maybe I will try running my angle grinder off my battery bank.

What size fuse would I use? No fuse and a short my batteries could melt a extension cord in seconds. No thanks. Anyone tries this use a fuse.