More Class T fuse questions

[Brett V]

I must have bought all they had. I ordered 6.

Edit: checked email and yes, they did backorder my order. They will charge the CC when they ship unless I cancel the order. April/May works for me, I won't see cells for 60 days.

I bought four of these. Outback Class T 300 Amp still in stock.

 

[HarryN]

If something severe enough has happened to blow a class T fuse, do you really want her messing with anything? I have breakers for convenience but fuses for safety.

The most common problem that I have seen with Li battery systems (in vans ) is that one or more of the parallel Li battery BMS's trip and people don't know that it happened. Usually they trip because the inverter pulled too much power charging up the input caps or they tried to run the batteries too close to the supplier discharge rating vs 50 - 60% like I try to suggest.

The effect is that only part of the pack is running and this causes even more problems.

So the breakers allow really anyone to go in and flip them off / on one at a time and this re-sets the BMS on each one, no sweat, no fuss. It is a near zero effort, high reward potential activity. Sort of like rebooting a windows computer.

If there is a big enough problem to trip a class T fuse, then it will also trip the breaker pretty fast.

Of course it is ideal to see some visuals of the system, and ideally some measurements with a meter before turning things on when possible.

Assuming that the the 600 amp-hr @ 12 volt system mentioned is either 6 x 100 amp-hr or 3 x 200 amp-hr, those breakers are rated to stop the current flow.

 

[12vDC]

FWIW

When I received my new Mini's a few months ago, I was capacity testing them and discharging them individually on my system with 1000W heater. On the second battery I randomly added a large fan to the circuit and pointed in the direction of the inverter. I walked away and returned with a dead system and the inverter had failed with a low voltage alarm, but the battery was not discharged! F***! I could get the inverter to turn on but would not operate. I checked the fuse (but did not pull it out and look at it) and it was still in place.

I forgot I had entered an 80A mrbf on the circuit. The heater AND the fan apparently was able to exceed the 80A fuse rating. The fuse did fail however, upon closer inspection internally it was still attached with just the slightest of shard of metal clinging on to allow 9V to flow. Hence, the inverter alarm and failure. Replaced the fuse and all was well.

If only anecdotal - you have to expect the unexpected when it comes to protecting your system - whatever you choose to install or not install, choose wisely.