Hi lots of devices list both a continuous and max current. For instance lithium batteries have a continous of 1c and a max of 2c.
What do you then use to decide de wire size and fuse ? I’m inclined to use the continous as target.
This depends on how long your peaks last for. If the peaks are very short (<10s) then it is the thermal mass of the wire that sets the size, together with the permitted temperature rise.
Are you wanting to fuse each battery?
And yes fuse type matters as well. For example fast blow slow blow.
i would lean toward continuous with a slower blow. As you can peak over. But it is hard to answer definitely when you don’t know what the rest of the system is doing or capable of so is the draw from the battery by the system likely to hit those peaks?
Ideally the more correct answer is - smallest you can go without having nonsense or annoying blowing is the best from a safety aspect.
The fuse amperage should bever be larger than what the wire can take without the wire heating up. And the wire should be sized for the continuous rating.
If you are diycheck out wiring unlimited.
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Ha! Lithium. Man. Those were the old days - for me - with reclaimed 18650 cells. Stopped using them six years ago. Nowadays using EVE MB31 cells. Got to say this 0.5P tops. Charging under 10 °C even lower. This is why I fused my batteries with a 125A T class fuse. Wires can handle a ton more. My battery cells not. The SOH will degrade fast when you don’t honour the charge/discharge ratings. And there isn’t a single DIY case on the market that can handle the 50kN swelling force - per prismatic cell - so people better be really careful.
Yes I’m fusing each battery, shouldn’t i ?
I’m not really expecting power spikes above what they can deliver so I’ll wire and fuse for continous.
Thanks for the insight. It the loads that cause the spikes not the batteries themselves.
I was not saying you shouldn’t. Just as long as you are aware that the short circuit rating of the battery is important to know for arc quenching. Really the only time fuses should blow is when there is a short circuit. (Causes possibly by wiring, short circuit or component fault.)
So these class T are considered the safest for battery banks. But NH fuses are also ok.
The battery delivery capability is irrelevant for determining fuse size.
OCP (Over Current Protection) is determined by the max load the circuit connected to the battery is expected to draw.
For example, you can have a battery bank capable of delivering 1000A. If the max load anticipated is 100A, then your OCP = Max load x 1.25.
Note that all of your wiring has to be rated for this current too.
If you size OCP based on nominal load, and then a max load of some duration occurs, it can blow/trip the OCP device.
If you size OCP for max load, and don’t also size your cables for this, they may overheat if a max load of some duration occurs.
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True. Especially the gBat NH1 from ETI. There might be others, of course, but that is what we use.
There are way too many people with 200A and 250A fuses and MCB’s with battery cells that can handle much less. Like the EVE MB31 cells for example, which EVE instructions is to use 160A fuses. I mean a short can easily damage the cells. If you take lower temperatures into account, then the cells will get damaged even earlier. And with aging cells get more fragile. Better save than sorry IMO - CEO and importer of prismatic cells since 2018.