Overkill Solar - Wrong BMS Size for my system?

monoxyde

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Joined
Jun 2, 2021
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26
The overkill 8s bms is only rated for 100 amps continuous.
You can't expect to run 150 amps continuous through it.
I understand that, however I've built my system for 150 amp capacity.

With my usage, I don't think I'm going to hit 150 AMP, but I may touch 100 amp, so may have some issues. It's understood.

Now, new question.

I'm looking at DALY 200/250 A systems on Amazon. I see they come with 2 AWG cable.... is it easy enough to upgrade that to 1/0 AWG?

Is there another BMS that is recommended besides Daly?
 
Joined
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I understand that, however I've built my system for 150 amp capacity.
You have built your system for <=100 amps continuous.
I would estimate that the bms over-current protection will trip PDQ at ~125 amps.
The bms is the bottleneck.
With my usage, I don't think I'm going to hit 150 AMP, but I may touch 100 amp, so may have some issues. It's understood.

Now, new question.

I'm looking at DALY 200/250 A systems on Amazon. I see they come with 2 AWG cable.... is it easy enough to upgrade that to 1/0 AWG?

Is there another BMS that is recommended besides Daly?
Not easy.
You would have to source or make those connectors.
The 2 awg cable on the bms likely has silicone insulation, probably rated for 200C so its ampacity rating would be considerably higher than for 2 awg welding cable with 105C insulation.
 

acdoctor

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Oct 5, 2020
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Location
Central Arkansas
I am running 4S2p with two overkill 120 bms so far working great. I monitor every cell and have 4 temp sensors. 24 volt 240 amps that is 2800 watts down at LVD.
 

monoxyde

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Jun 2, 2021
Messages
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Still a build in process.

200/250 AMP BMS should arrive on Friday.


Waiting on BMS to arrive Friday.

Battery <-> BMS <-> Negative Bus Bar <-> Growatt

Hopefully this will give you some idea of what I'm doing. I'm not claiming I know what to do, but it's been a slow process, just doing one thing at a time.
 
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@smoothJoey I guess I forgot to describe the positive side of things.

Battery Positive <-> 250 Amp Breaker <-> Battery Disconnect with @FilterGuy 's pre-charge design( https://diysolarforum.com/resources/inverter-disconnect-switch-with-precharge.60/ ) <-> Growatt
That breaker looks like a knockoff.
If you want a breaker for the Armageddon position I suggest this one.
 

monoxyde

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Jun 2, 2021
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That breaker looks like a knockoff.
If you want a breaker for the Armageddon position I suggest this one.
I just read the reviews, good catch!


I may just do an ANL fuse in the mean time, and add a breaker at a later date. I'd prefer a breaker over fuse, because if I'm out in the middle of nowhere and don't have extra ones I can just flip it back on... I don't know, I'm not the electrician here.

Fuse or breaker? I know it's mostly for Armageddon purposes like you stated.
 
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Messages
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I just read the reviews, good catch!


I may just do an ANL fuse in the mean time, and add a breaker at a later date. I'd prefer a breaker over fuse, because if I'm out in the middle of nowhere and don't have extra ones I can just flip it back on... I don't know, I'm not the electrician here.

Fuse or breaker? I know it's mostly for Armageddon purposes like you stated.
An ANL fuse has an arc interrupting capacity rating of <10,000 amps.
For the fuse/breaker closest to a 24volt or greater LFP battery prevailing wisdom suggests a fuse with minimum 20,000 amps AIC.
Also I've heard reports that when those ANL fuses blow under high current the tend to create shrapnel.
 
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