does the circuit board have a resistor on it? When the resistor is activated, the resistor heats up the board and you no longer see the temperature of the battery, you see the temperature of the hot resistor board.
The problem with most battery management systems is sometimes they cause imbalance rather than correct for balancing issues. Boats are different from cars because boat often get laid up for months at a time. In areas where it is cold, they could be not used for 6 months at a time. Some of the board will have a different phantom load than other boards, and over this length of time, this can make the batteries go out of balance instead of what they are meant to do.
Also, you have to watch how much spaghetti you put on top of a battery and the circuit board on battery approach has more wires than a centralized system does, even though most advertise that they have less wires.
You also have to watch out for adding unfused wires to a battery that can have thousands of amps of short circuit potential.
The cost is also another factor.
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Whenever you put a safety system on an electrical system you also put a weak point in the system so you have to be very careful how you go about it. Fuses put extra connections. Each connection is a potential problem.
When you put a fuse on a wire, there is a connection from the wire to the fuse body, then the fuse body to the fuse, then the fuse to the fuse body and the fuse body back to the wire. You have now put 4 extra connections on a wire. Each connection is a potential point of failure. I am all about putting a fuse on every wire so it is very important what the fuse is, what the fuse body is, and what connections are made to it.
Safety systems are essential, but they also have to be done right, otherwise they can become the problem, rather than the solution.
Also you have to watch the ratings of the fuses that you use on a 48 volt system, which should be rated for the maximum charging voltage that the system or charger experiences. On the 48 volts bus, this is usually 58 volts and then its nice to have some headroom above that. We use 80 volt rated circuit breakers for 48 volt systems, and 125 volt rated breakers on 72 and 96 volt systems. The newest fuses we have found give us a 600 volt AC or DC rating. They cost more, but they are worth it.
James Lambden
The Electric Propeller Company
625C East Haley Street,
Santa Barbara, CA
93103
805 455 8444
james@electroprop.com
www.electroprop.com
The Electric Propeller Company
625C East Haley Street,
Santa Barbara, CA
93103
805 455 8444
james@electroprop.com
www.electroprop.com
On Jun 10, 2017, at 8:11 PM, boat_works@yahoo.com [electricboats] wrote:
Whoops, forgot the link!Here's the link to a BMS for 6V or 12V lead acid batteries: http://www.manzanitamicro.com/products?page=shop.product_details&flypage=flypage.tpl&product_id=87&category_id=22I've been using their lithium BMS in my launch for several years.-Tom
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Posted by: James Lambden <james@electroprop.com>
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