Re: Fusing control circuits -vs- power supply circuits

Scott SV Tengah

There are two separate issues here:

The first thing I spec'd when I installed my Victron lifepo4 was 3 mega fuses, one per battery pair. Each fuse is big enough to run the bow thruster on its own, in case the other fuses happen to blow. That protects the wiring in case you have a short. The amount of current that a lithium battery can deliver is a blessing if it's used properly and a curse if it's going through an unintended short.

The BatteryProtect or low cell voltage disconnect is there to protect the batteries (hence the name Victron gave it). The largest one they make is 220amps, called the BP220. The bow thruster, hydraulic passerelle, a 5kw inverter running multiple appliances will easily fry it. My BP220 lasted for less than an hour after installing it. First time I touched the passerrelle remote control, the BP220 melted.

After using lithium for 4 years now, even if Victron or someone else made a 1000amp BatteryProtect, would not install it as I still do not think a blunt load disconnect of all uses is advisable. I would not want to lose nav lights and autopilot just because I didn't top balance for a few months and despite being at 25% SOC, one of my cells dropped below 2.8v and triggered a low voltage disconnect. Or if I'm away from the boat and the bilge pump is running due to a leaking raw water hose with the aforementioned imbalanced batteries, I would rather the pump keep going and kill one of my admittedly expensive batteries versus have the engine room continue to fill with water.

2007 A54 #69
SV Tengah

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