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How to determine what amperage bus bar to buy

Visionguild

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I have two signature solar 48v 5kW lithium batteries I will be running in parallel into two growatt inverters. I've clicked on a couple of the parts links from Wills videos for busbars and some are rated at 300 amps and others at 600-1000 amps. I went through the entire manual for the batteries and there's no mention of amps. How do I know what the current in amps is coming out of the batteries. I also need to buy the t class fuses he refers to but those also have various ratings. He says to put them on the hot leads if I'm using more than one battery. This is in this video. Thank you!

battery manual. https://drive.google.com/file/d/1Pkk70ko2JgPA68nOhVyMeHnf84yOpQFM/view?ref=cPwLcVc0SW-BjN
 
How do I know what the current in amps is coming out of the batteries.
You know the amps coming out by counting the amps used in your loads. What are you powering from your batteries? An inverter is usually the biggest draw but you also need to figure in all the other concurrent loads. That and some buffer will be your bus bar size requirement.
 
What mister sandals said. Another way to think about it is, these batteries can deliver (almost) all their amps at once. That would be bad. Imagine a wrench across the terminals. So if you put a 10 amp light across the terminals, it would draw 10 amps.

Figure out your total expected load and size you wire and fuses to that. Wires sized ti load, fuses sized to wires. Big fuses near the battery where it all comes together, smaller fuses farther out.
 
Assuming each inverter is rated for 5000 watts continuous...

5000 ac watts / .85 conversion factor / 48 volts low cutoff = 122.549019608 service amps
122.549019608 service amps / .8 fuse headroom = 153.18627451 fault amps.
153.18627451 fault amps * 2 inverters = 306.37254902 busbar amps.

What is the continuous rating for your inverter?
 
5000 Watts ÷ 48 Volts = 104 Amps Draw.
Low Frequency Inverter can do 3X Surge while a High Frequency can only do 2X Surge.
The general rule of thumb is to not exceed 250A Draw from a battery bank. Other things come into play after that level.
So assuming 250A Max @ 48V = 12,000W or 120V/100A or 240V @ 50A.
** These are GROSS Numbers not corrected for inversion losses. HF vs LF Inverters have different efficiencies. Tier-1 Products like Victron, Samlex tend to be around 94% Efficient while lower-level products can drop to 82% efficiency. In General Growatt is Mid to High 80% Efficient, some of their higher end models are better.

ALSO BE AWARE of the Standby / Idle energy consumption ! THAT can be Very Significant !

I run a single bank of 5 large packs for 1190AH/30.4kWh. I am converting this to a Split Bank which will have 2x 175AH on one leg and 3x 280AH on the other leg of the bank using a dual common DC BUS. Once you go past 4 Packs in one bank, things get strange!

I use pairs of these Covered Busbars which are rated for 250A and the best deal I could find on them ATM is from here which just supplied me with a final pile of gear, https://www.ebay.ca/itm/152438375154 They delivered Fast & OnTime !

Fuses: I am a tad unusual as I use MRBF Fuses as opposed to Class-T Fuses (kept wrecking those). They are on average about $30 USD ea with the Terminal Block. I use ONLY BlueSea ones which are made by Eaton/Bussman and are Top Quality. All of mine are 250A.
BlueSea Link: https://www.bluesea.com/products/5191/MRBF_Terminal_Fuse_Block_-_30_to_300A

KNOW your Battery Pack !
Using my example, I use 280AH Packs.
They are physically capable of outputting up to 280A for 1 hour and take 140A for 2 hours to charge. They are Burst Discharge Capable up to 5C for 60 Seconds (varies by maker a bit). Therefore you need to fuse them to the max you will allow, 250A is quite enough. ALSO if you add battery packs in Parallel, any Load of Charge will be divided proportionately between the packs. This is IMPORTANT TO NOTE. This si one of the reasons to keep battery packs within a battery bank close to each others capacities as it is very easy to introduce an unbalancing factor if the difference is too much.

A last thought to ponder.
Typically if building a Bank of 2 or more packs, it is best to configure them to be capable of working (charge & discharge) as a "Stand Alone" or "Last Man Standing", This allows for Fail Over Fault Tolerance should any pack decide to cutoff for any reason. This means that whatever BMS you select should be capable of handling your maximums for Charge & Discharge.

A WARNING !
As stated I have a fairly large bank plus I have utility packs as well, all LFP. This has all been put together over the past couple of years as I moved away from the Heavy Lead Acid. The gotcha was different versions of BMS and a slight mix of gear resulting from the evolution. I am now replacing about $2500 USD worth of BMS, Contactors & more to Normalize & Simplify all the packs to have identical BMS and Communications / interactive capabilities. Let alone the cost of all the new BMS' and related goodies on top... So really do PLAN THINGS AHEAD !

Hope it helps, Good Luck
 
Short answer is the bus bars should be chosen based on the OVER CURRENT PROTECTION DEVICE built into the Battery. In your case I believe its a 100A Breaker but you should verify. If 2 are in parallel then there is a potential for 200Amps total so that should be the size of the bus bars.
Longer answer: If you also install fuses on each individual battery hot wire that is fine as long as the fuse rating is equal or LESS than the breaker rating. If the fuses are attached directly to the battery output posts then they would supersede the breaker and everything downstream can be sized based on the smaller fuse rating. If on the other hand the fuses are placed on the inverter input terminals or a junction box midway between the batteries and the Inverter then everything UPSTREAM of the fuse has to be sized based on the battery breaker and everything DOWNSTREAM of the fuses can be sized according to the fuse rating .
 
What mister sandals said. Another way to think about it is, these batteries can deliver (almost) all their amps at once. That would be bad. Imagine a wrench across the terminals. So if you put a 10 amp light across the terminals, it would draw 10 amps.

Figure out your total expected load and size you wire and fuses to that. Wires sized ti load, fuses sized to wires. Big fuses near the battery where it all comes together, smaller fuses farther out.
They are 3000w
How many watts/amps are these rated for?
Are there other DC loads that will be running?

Your bus bar will probably be around 2.5x what each inverter is rated for.
I think I misunderstood your question. The inverters are 3000w each and the batteries are 100amp hour batteries.
 
The inverters are 3000w each
Your 2 inverters, at 6000W total would require:
6000W / 51.2V = 117A
5000 ac watts / .85 conversion factor / 48 volts low cutoff = 122.549019608 service amps
122.549019608 service amps / .8 fuse headroom = 153.18627451 fault amps.
153.18627451 fault amps * 2 inverters = 306.37254902 busbar amps.
Putting smoothJoey's refinements:

6000 / .85 / 48 = 147A (service amps)
147A / .8 fuse headroom = 184A fault amps (or AC inverter only)

Add in what you intend to be running directly from battery and that is your rated amps for bus bar, fusing and wiring (that was your question, right?)
 
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