question

geolboy avatar image
geolboy asked

Main fuse placement question using REC BMS, Contractor, Pre-Charge unit and Victron equipment

I am in the middle of the build an electrical system for my van using REC BMS, LifePo4 cells, and Victron equipment. I have a question regarding placement of the main fuse. Rec BMS (and few other users I could find example builds) shows the main fuse from the positive side located after the main contractor?

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There is a discussion started on the solar forum where few users commenting this is wrong and that the fuse should be first in the connection from the battery. Here is a link to the post:

https://diysolarforum.com/threads/installing-bluesea-6006-on-off-switch-location.40931/

It would be great to know what is the reason for the main fuse to be located after the contractor. And if it make any difference for the pre-charge process placing it just of the Battery+ post, as I understand it pulls a high-amp draw? Would that possibly blow a 400A fuse?

I would greatly appreciate a clarification, last thing I want is to accidentally destroy the contractor by a surge in mid of traveling somewhere off-grid. Thank you kindly.


BMSfuses
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2 Answers
jokani avatar image
jokani answered ·

My understanding is that the fuse is there to protect the cable, and not the contactor.

In my REC BMS system the fuse is after the battery and before the contactor, pre-charge bits etc seems to work fine.

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geolboy avatar image
geolboy answered ·

Got an answer from REC folks: "You are right. Fuse before the contactor will also protect your contactor and battery in case there is some short current at the contactor pins for instance. We will change the schematics with the next manual version".

Thanks to all for the help!

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Related Resources

Victron VE.Bus BMS product page

Victron 3rd party BMS compatibility page

Fuses & fuse holders Product Page.


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