Welding with LiFePO4 Batteries?
Have you ever wondered if you can use a welder off grid? How about can you run it with LiFePO4 batteries? The answer is a resounding yes! I had a customer reach out and ask about his particular setup, and if we'd be able to supply batteries that could run his welder for an hour straight when he was in the bush off-roading.
He was already running his setup with heavy AGM batteries, and they were nearing end of life. So, we knew he already had answered the questions surrounding whether his inverter could handle the load or not, we just needed to find out if our batteries could take that kind of abuse. I decided to run a test using one of our demo model batteries.
What are LiFePO4 Batteries?
In case you're just starting out, let's do a quick knowledge check.
LiFePO4 batteries, also known as lithium iron phosphate batteries, are a type of rechargeable battery known for their high energy density, long cycle life, and enhanced safety features (especially when compared to lithium ion, which is the ones you hear about in the news on fire). These LiFePO4 batteries have become increasingly popular in many assorted user groups (especially off grid, and solar users), due to their superior safety, performance, and reliability.
Why Use LiFePO4 Batteries for Welding?
When it comes to welding, having a reliable power source is crucial. While it's obviously better to use grid power for this sort of demanding application, what are you to do if you're off grid, or out in the bush?
It turns out, LiFePO4 batteries offer an incredibly stable voltage output, ensuring minimal losses in your cabling, which can translate to consistent performance throughout your welding project. Additionally, these batteries are lightweight and smaller, making them far more attractive than the traditional lead alternatives.
Instead of hauling 4x 6V lead batteries (~250lbs), you can use 2x 12V LiFePO4 batteries (~110lbs) to get you the same 5.8kWh of energy.
Lastly, depending on your other wants/needs, you may already have a large battery bank installed where you'd be doing the welding. If you're already going to have a battery bank, then making it a little bigger might just be the best option anyway.
Why NOT Use LiFePO4 Batteries for Welding?
"Why not use a generator?" is the first thing that comes to mind. And it's a valid question. But you'd likely need a fairly heavy duty (read large) generator, and additional fuel to run it. Sometimes, you don't have the luxury of that space in your Jeep/Truck/Etc.
Obviously battery powered welding isn't the first choice most people would think of, and for good reason. Welding is a heavy demand on the power source. You're literally using electric current to melt and fuse steel. But once again, if you don't have access to the unlimited power of an electric grid, or room for a big generator, batteries can become a viable option.
The other downside, which is the same for all battery technologies, is that sustained heavy draws from the battery, like this scenario, will lead to faster battery degradation. At least when compared to a more normal use case like in an RV, or camper. But this isn't unique to one battery technology over another.
Benefits of Using LiFePO4 Batteries for Welding
1. Enhanced Portability: Say goodbye to bulky power sources. LiFePO4 batteries are lightweight and easy to transport, allowing you to weld in various locations with ease. Instead of hauling 4x 6V lead batteries (~250lbs), you can simply use 2x 12V LiFePO4 batteries (~110lbs) to get you the same 5.8kWh of energy.
2. Long Cycle Life: LiFePO4 batteries are known for their long cycle life, meaning they can typically withstand thousands of charge-discharge cycles without losing any substantial capacity.
3. Fast Charging: With rapid charging capabilities, LiFePO4 batteries can be charged quicker than lead technologies, minimizing downtime and maximizing productivity. They don't boil like lead based batteries do. Note that this benefit does require the use of a beefier charger to really come into play.
4. No Sulphating: Lithium Iron Phosphate batteries don't suffer from sulphating, and capacity degradation, when they are left discharged for extended periods of time. In fact, it's generally regarded as better to leave them partially charged. This means you don't have to try and recharge your batteries immediately, or risk damaging them. You get better flexibility.
Tips for Welding with LiFePO4 Batteries
1. Choose the Right Battery Capacity: Select a LiFePO4 battery with the appropriate capacity to ensure it can meet the power requirements of your welding equipment. You'll want to make sure the BMS can handle the sustained current output your setup will require.
2. Monitor Battery Health: Regularly check the status of your LiFePO4 battery to ensure optimal performance and longevity. Active balancing, and proper charging will make sure your batteries are in the best condition to be able to provide you the most power.
3. Invest in Quality Equipment: Buy a quality LiFePO4 battery, and pair it with high-quality charging, and inverter equipment. Use the proper fuses to protect everything.
Testing the Question:
Ok. So how do we test if the battery will actually hold up to the abuse of welding? Our customer needed a battery that will handle ~150A for up to an hour.
I cobbled together a pair of inverters, a hair dryer, a heat gun, and a battery charger to get a 145A load that would be predictably steady for the test duration. I also grabbed an IR camera, and set it to take pictures every minute.
I set everything up on a tool bench in the workshop, and used our shop test/demo 230Ah unit (It's been cut open for other inspections/tests, hence the tape holding the top on)
I set a timer on my phone, and recorded the temperatures from the BMS, the reported BMS voltage, the Load, and the IR camera case temp, every 5 minutes. The results honestly surprised me.
With the load applied, the battery output voltage started at 12.54V, but quickly started to climb up as the internal temperature went up. After about 20 minutes, the output voltage was actually at 12.62V, and it remained there for about a half hour.
The electronics temperature (MOSFETs) in the battery started at 12.2°C when the test began, and over the course of 70 minutes, only raised up to 41.1°C. If I'm being honest, I had expected the temperatures to climb a fair bit higher than that. The battery won't shut down for high temperature until it's in the mid 70's, so even on a warmer day, the battery should be able to cope ok.
Now, I need to mention that the battery is equipped with a 200 Amp BMS module, so not all batteries will be able to output 145 Amps. And different manufacturers/designs will perform differently. But it looks like the Sapphire Energy 230Ah SMART LCD series battery (and probably the 300Ah as well, since it's the same electronics) can actually handle this sort of abuse.
It's also probably a good thing to realize that there is almost never a consistent load like this in the real world. Even actually welding, it's unlikely you'd be able to go for 60+ minutes straight without even pausing. Any short pauses, or reductions, in the load, will result in immediate drops in temperature.
I used the Bluetooth connectivity of the battery to read and record the internal MOS temperatures during the test, so here's a couple screen shots to support my claims. (Test started at ~7:35pm)
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 ~65 minutes into the testing |
~35 minutes into the testing
Conclusion:
While running a welder off of batteries is a bit of an unlikely scenario for most users, it's good to know that the LiFePO4 battery technology can handle it. There's a few considerations, like if you stack multiple batteries in parallel, you may generate a little more heat if they're right next to each other. But with a little careful planning it can be done.
This also speaks to the ability to run high demand appliances like induction tops and air conditioning units, which is a far more likely situation to find yourself in.
If you're curious about the test results I recorded, you can check out a PDF with the full details of the testing here.