Building A Lithium Battery For Use With Inverter.

[The Mighty Volt]

Hello people.

I wanted to rent some garage space near my place of work to give me somewhere to go after work to work on my bikes and store my stuff.

These garages do not provide electricity as an option.

I hope to have the vast majority of my heavy fabrication done before I move my stuff into the garage.

I was curious as to whether I could build a massive 12v or 24v battery out of round LIfe or LiMn cells, say 100ah, and run it through an inverter to provide me with clean AC power for small jobs like harness making or just general tinkering, making lights etc.

Similarly, I hoped to run some LED lights off it to illuminate my workplace.

I would then periodically recharge the entire system using an inverter generator. I prefer to run off the batteries as that is nice and quiet and the people renting the garages disapprove of using generators etc.

I don't know anything about electrical theory or engineering principles so I thought I should ask first.

I am of the opinion that massive Ah DC power supplies can be of some use in this situation.

Thank you.

 

[e-beach]

Building a 12v 100ah battery pack to provide volts through an inverter wouldn't be much different then building a 12v 100ah pack for an e-vehicle. Similar principals apply. Proper charging and balancing would be needed like any good lithium battery pack setup. High "C" rated batteries could keep your tools from sagging at start-up. Proper current draw would have to be monitored through a watt meter to insure that you aren't over discharging your cells. It's very doable, but 100ah of lithium batteries can cost a bunch of money though. Not to mention the wiring, meter and such that would be necessary to insure proper balance.

But, your setup doesn't have to be lithium batteries, a couple of 100ah marine deep-discharge flooded lead acid batteries would work fine. Much easier and cheaper, just not as fancy a setup.

What kind of tools are you going to use?
How many watts are they going to pull?
How much do you want to spend on your inverter?
Do you need a pure sine wave inverter for a computer?
Can you install a solar panel setup to charge the batteries while not in use?
Do you want to spend the money on a super capacitor bank between your batteries and the tools to give a boost when you turn the tools on?

It all can be done. But like the sign says...."Speed is just a matter of money. How fast do you want to go?"

 

[dnmun]

wouldn't it be cheaper to run an extension cord there?

 

[The Mighty Volt]

Building a 12v 100ah battery pack to provide volts through an inverter wouldn't be much different then building a 12v 100ah pack for an e-vehicle. Similar principals apply. Proper charging and balancing would be needed like any good lithium battery pack setup. High "C" rated batteries could keep your tools from sagging at start-up. Proper current draw would have to be monitored through a watt meter to insure that you aren't over discharging your cells. It's very doable, but 100ah of lithium batteries can cost a bunch of money though. Not to mention the wiring, meter and such that would be necessary to insure proper balance.

But, your setup doesn't have to be lithium batteries, a couple of 100ah marine deep-discharge flooded lead acid batteries would work fine. Much easier and cheaper, just not as fancy a setup.

What kind of tools are you going to use?
How many watts are they going to pull?
How much do you want to spend on your inverter?
Do you need a pure sine wave inverter for a computer?
Can you install a solar panel setup to charge the batteries while not in use?
Do you want to spend the money on a super capacitor bank between your batteries and the tools to give a boost when you turn the tools on?

It all can be done. But like the sign says...."Speed is just a matter of money. How fast do you want to go?"

Hi there, thanks for that.

The tools I would be using would be a

1250w DeWalt grinder
A 500w pillar drill
100w soldering station
Cordless tool chargers

Lighting would all be tiny-amps LED stuff. Bright but low draw.

I would like to do welding but I will buy some inverter generators and parallel them.

\thanks.

 

[dogman dan]

Isn't it going to be running a generator for quite some time to charge it?

 

[Punx0r]

You could put a DC motor in the pillar drill and run it straight from the battery. The grinder could be replaced by a rechargeable cordless type if the workload isn't too high?

Motors cause problems with inverters because of the very high initial starting current. You'd want to check an authoritive source, but your 1250W grinder might need a 3-4 KW inverter.

 

[agniusm]

Probably best chemistry wiuld be lithium iron phosphate titanine for this application.

 

[e-beach]

I had a Honda EU2000i and it was very quiet for a generator. Have you ever heard a quiet motorcycle idling? Something like a quiet BMW? It is about that loud.

 

[MitchJi]

Hi,

I think the cordless grinder is a great idea.

I would also use a drill stand, like the following, with a cordless drill:
http://www.fine-tools.com/bohrstaender.html

You decide to use a big battery bank use Nissan leaf modules. They cost about the same as a SLA, and last much longer.

 

[dermot]

Lead acid car batteries are the cheapest but looking at your power requirements, you'd be pushing your luck to get 1250W from a 12V powered inverter, that would require something like 125A at 12V DC to feed it. 24V would be a bit better, but I'd go for 48.

Huge cables and volt drop are the performance limits in my experience with low voltage DC input inverters with very poor efficiency (75% and you'd be doing very well). As soon as your batteries dropped by a volt or two, the inverter would cut off. 12V input ones tend to have a crappy waveform as there is little headroom to get it right at such low voltage.

A friend asked me to fix up a long run inverter for keeping a 240VAC sump pump running and I have a pile of old 48V scrapped inverters in which the internal batteries have died. I strung 4 car batteries in series to test and it worked very well, pulling 30-odd A DC at full 1500W load and was very stable.

I did something similar for a friend with a motor home and used four 12V 280AH deep cycle lead acid batteries. I've still got one of those monsters - too damn heavy to move by myself, but one day it goes into a garage with a 100W solar panel on the roof to provide a bit of power...

Charging a 48V pack from 12V is easy enough using one of the little DC/DC converters; I'd use several in parallel as each would net you around 2A out at 48V, pulling 12A on the input.

5 of them in parallel (they are only £10 each) would pull 60A from a car while charging and supply 10A output - not exactly fast-charging, I grant you, but workable.

Depending on how often you are in there (and how much power you draw) even a relatively modest 100W solar panel on the roof might make you completely independent.

cheers,

Dermot

 

[dogman dan]

I assumed a high cost inverter. Something in the 5000w range. Big, expensive, like you'd put in a small home to run it solar off grid.

Rent on a place you are allowed to run your generator sounds better to me.

 

[The Mighty Volt]

I assumed a high cost inverter. Something in the 5000w range. Big, expensive, like you'd put in a small home to run it solar off grid.

Rent on a place you are allowed to run your generator sounds better to me.

Hi Dogman, yeah, pretty much, I am thinking of spending good money here.

I was watching lots of videos of the Honda genny you were speaking of, but.....seemingly not available in the UK for some reason.

Nor is the Ryobi equivalent.

Best thing about those Hondas is that they can be paralleled. That might give me the sort of 4000w peaks I need to use a welder.

 

[MitchJi]

Hi,

Lead acid car batteries are the cheapest but looking at your power requirements....

I just checked and I think you are correct, but I bet it's closer than you think.

Four 12v 150ah Trojan golf cart batteries are $900.

Sixteen of the 7.2V 60ah Nissan leaf modules (16s-4p, 57V nominal with 120AH) would cost about $1600 at a automobile wrecking yard.

That is 120ah vs 150ah for the Trojans, but there is no Peukert effect, and if you figure that they should last 1.5x to 2x longer than the Trojans, the total cost should be roughly the same.

Another advantage of the leaf modules is that you could put them in a small trailer that you could easily tow , someplace for charging with an ebike.

 

[dnmun]

forget the extension cord. it will be cheaper to wire the garage for 240V AC now.

if you cannot get power there you need to find another apartment complex that has a garage where you can run the extension cord from your apartment to the garage.

 

[MitchJi]

if you cannot get power there you need to find another apartment complex that has a garage where you can run the extension cord from your apartment to the garage.

Cheaper unless he uses cordless tools. Even if they cost a little bit more initially they would be good to have. And he can easily run the LED lights off of a few 18650 cells