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Daly 150a Smart BMS; cables too small?

Rwinike

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May 26, 2021
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Hi All,
Every chart and reference I can find suggests never putting more than 90 amps through 6 gauge wire. If use this BMS, even with more capable wire for the rest of the circuits, I am still limited by essentially the main negative terminal. And, Daly used a proprietary connection so I can’t conveniently replace it. What have others done to rectify this??
TIA!
Robin
 
Hi All,
Every chart and reference I can find suggests never putting more than 90 amps through 6 gauge wire. If use this BMS, even with more capable wire for the rest of the circuits, I am still limited by essentially the main negative terminal. And, Daly used a proprietary connection so I can’t conveniently replace it. What have others done to rectify this??
TIA!
Robin
Buy a bigger BMS, either that or replace the wires (and expect the BMS to fail sooner or later).
I bought the 250 AMP Daly, for 150 amp (maximum) discharge. The 250 amp model comes with 2 gauge wires.

Daly does not accurately rate their BMS, as you've noticed.

Even if you buy 50 or more, Daly refuses to put larger wires on it. They will however put an M6 or 1/4 inch connector on the battery wire.
Daly apparently is not concerned with what the customer wants, or their reputation (from what I can tell with extensive discussions about customizing a BMS).
 
If its 200*C silicon wire like whats on my 200a Daly model, then it should be rated for 135 amps. Not quite 150, but much more than 90 amps.

I dont understand why people say to derate them so much?? Even @Will Prowse has tested them and came out several times stating that 200 amps will handle 200 amps.

I've pulled 150amps from my 200a 48v Daly BMS, (which is the max my inverter will do), and it barely got 10*F over ambient temp after 15 minutes. I fully believe it will continuously output 200a.
 
If its 200*C silicon wire like whats on my 200a Daly model, then it should be rated for 135 amps. Not quite 150, but much more than 90 amps.

I dont understand why people say to derate them so much?? Even @Will Prowse has tested them and came out several times stating that 200 amps will handle 200 amps.

I've pulled 150amps from my 200a 48v Daly BMS, (which is the max my inverter will do), and it barely got 10*F over ambient temp after 15 minutes. I fully believe it will continuously output 200a.
Do you really want your wire to run at 200 degrees Celsius? Make sure to wear gloves, you will burn yourself.
Also consider the fact the hot wire will warm up the BMS as well. High temperatures are not good for electronics, no matter what they are rated for.

15 minutes and a 10 degree rise? That is a pretty substantial thermal mass, what is it like after an hour? I suspect it would have no problems pulling 200 amps like you say over an extended time, however most people really want it to last 10 years, not one or two.

I'm sure Daly does get pretty close to their rated output, but do you really want to run it at the limit for extended time periods? Make sure you have adequate ventilation.
 
Do you really want your wire to run at 200 degrees Celsius?

Who said the wire was getting up to 200* C? At 75% output it was barely 30*C. I can't imagine it jumping 170*C for another 50a of output.

Good question about the 15 min vs an hour. I waited the 15min with the inverter at 95% output and the inverter shut down from over temp. Now that I have another LV6548, I can draw much more than the 200a rating for an extended period of time, I will test that when I get the system up and running. Ill see if I can pull a good 250-300a and see what happens, as well as a long term 175-200a test.
 
you can run smallish wire for short distance fine...
6 inches of #8 can handle more current then 1000' of #2
 
you can run smallish wire for short distance fine...
6 inches of #8 can handle more current then 1000' of #2
I'm just pointing out that just because something is rated for it, doesn't mean you should run it at that capacity. The smaller gauge wiring will be using your battery and BMS as a heat sink. If all you want is surge capacity, shouldn't present a problem. Long term sustained use, probably not a good idea. That's why I have a 250 amp BMS even though my surge is 150 amps, and normal use is 90-100 amps. The 2 gauge wiring works for that, and no need to test the 205 degrees C rating on the insulation.

I saw where another user here was surprised that his fuse was heating up his wires. Yes, fuses do that. They blow when they overheat and melt. Ideally, you want the fuse to protect your wires from a dead short, and less from your expected current. The higher the fuse rating, the less heat generated. It's complicated, but the BMS and the battery are heat sinks those wires connect to, so you want to keep things over rated.
 
I'm just pointing out that just because something is rated for it.

I think the opposite, if something is rated for it, you should absolutely be able to use it up to that rating! No if, ands, or buts about it!

But im sure I won't be able to change people's minds, to each their own.
 
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