LIFEPO4 Battery discussion thread

cavedog said:
Yeah I saw that one and it's not badly priced for the amps it can handle. Perfect for me.

Now you mount it, so the busbars are vertically and then the cables come in on the sides, right?
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How many amps you need?
 
cavedog said:
So hard to find a decent and affordable busbar. Any suggestions?

I was looking at this so far

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Only recommendation is dont go too cheap or get a china one. Like Lugs, they aren't using actual copper. If it's too shiny then its steel. They rust in a few months. I learnt my lesson with some of the electrical connections I did on the Jojo tank pump. Had to redo everything there coz the "copper" lugs rusted.

For my solar, I only used the proper stuff even though the accessories like lugs and breakers etc was more expensive than my inverter lol.
 
wingnut771 said:
Well, 5000W divide 40V = 125A. 125A x 1.25 = 156.25A
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Yeah so even 200A will be well within range at the lowest voltage of 40V but we know lifepor cutoff is at 46V or so if you play it safe.
 
cavedog said:
Yeah so even 200A will be well within range at the lowest voltage of 40V but we know lifepor cutoff is at 46V or so if you play it safe.
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How do you know LFP cut off is 46V? What if BMS goes faulty?

Anyway, 135A then vs 150A.
same same.gif
 
cavedog said:
Don't you need to fuse each individual battery positive terminal?
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Yes. I dont know if BMS protection is enough. Always better to have mechanical protection.

I made a mess up last year and welded my screw driver adding the MPPT victron charger. Was before the breaker, all 5 of my fuses blew in an instant. Saved my batteries from having to supply a huge current and my fingers from melted steel.

If you get an internal short in the battery, the other batteries will see it as a load and push a ton of current into it. That leads to heat and then a fire.

Fuses are bidirectional. So it would isolate the battery.
 
cavedog said:
Recommendations please? 125A is the size recommended for 5.12kW batteries so looking for that or max 150A.
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What is the max safe discharge for your battery? Think they give it as 10 seconds or something like that. You don't want nuisance trips from the fuse.

I would get one that matches the safe max discharge for the battery.
 
cavedog said:
Recommendations please? 125A is the size recommended for 5.12kW batteries so looking for that or max 150A.
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Fuses are to protect the cable, so the fuse goes before the cable melts.

So cable should be able to handle 25% more than the fuse imho, so 150A fuse and 200A cable.

@denmendez65, what do your fuses look like?
 
denmendez65 said:
What is the max safe discharge for your battery? Think they give it as 10 seconds or something like that. You don't want nuisance trips from the fuse.

I would get one that matches the safe max discharge for the battery.
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100A as per the spec sheet. Not sure if it matches the bms but BMS will probably max at 110a

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denmendez65 said:
What is the max safe discharge for your battery? Think they give it as 10 seconds or something like that. You don't want nuisance trips from the fuse.

I would get one that matches the safe max discharge for the battery.
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Oh you have breakers not fuses. Each 5kWh battery would be 100A plus 25% so 125A fuse. So if 2 batteries, then cable feeding inverter should have 250A fuse and 300A cable?
 
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