I'm currently building some hefty batteries that are 48V with capacities ranging between 100Ah to 300Ah. I'm installing terminals on the outside of the battery case for easy access, but I'm unsure about how close the positive and negative terminals can be placed to one another without risking arcing or short-circuits. Is there a standard guideline or calculation method to determine the safe distance between them?
4 Answers
Honestly, at 48V, you shouldn't worry much about arcing. The main concern would be short circuits caused by dirt or metal shavings creating unwanted connections. As a rule of thumb, it's best to keep the terminals spaced apart as much as practical. Many car batteries do this by placing terminals on opposite sides, which is a good approach!
At 48V, arcing isn’t really a major concern since air only breaks down at much higher voltages. Just be careful with your wires and connectors. Make sure there are no sharp edges on the enclosure, use heat shrink on exposed wires, and ensure that your terminals and switches are rated for DC voltage. It’s critical for safety!
Great advice! I'll definitely double-check that all my components are rated for safe use. Thanks!
You're going to want to check out creep and clearance distances. There's info available that covers how close the terminals can be while still being safe. It seems like the safe distance is just a fraction of a millimeter, so you should be good with that setup!
Thanks for pointing me in the right direction! That makes sense since I was aiming to have them close but wasn’t sure how close was safe.
There are actually two key distances to think about: the air gap and creepage distance. The air gap prevents breakdown through the air, while creepage is the distance along a surface between terminals. Generally, once you meet the creepage requirement, you’re fine with air separation as well. For 48V systems like yours, just keeping a separation of about 1.25mm usually ticks all the boxes. Here's a link to some great diagrams if you're interested!
I appreciate the detailed info! I was planning for a couple of inches apart, so sounds like I'm in the clear.
That’s a helpful perspective! I’ll make sure to keep things clean and check for any potential shorting hazards.