This site is now in read-only archive mode. Please move all discussion, and create a new account at the new Victron Community site.
What amperage disconnect do I need for a 8oo amp hour batter bank? Is it based on the amp draw or is it based on the size of the battery bank? I bought a Blue Sea 350 amp e-series.... but they only go up to 600amps in the HD-series. Any thoughts?
I am using a Lynx Distributor In-> Lynx BMS-> Lynx Distributor
I am planning on using disconnects for all of my individual DC loads coming out of the Lynx Distributor.
Do I even need a batter disconnect at the batteries?
Thanks!
What voltage is your system?
What size is your inverter (s)?
What wiring sizes are you anticipating?
Yes, you need a battery disconnect switch regardless.
Fusing is based on the lesser of the max current or the wire size if it is less ampacity than the battery bank. A lot depends on your battery bank and system voltage. Lithiums will typically have a max continuous current equal to the AH rating, e.g., 100 amps continuous for a 100 AH battery. Peak currents are typically double that value. Then you need to look at system voltage.
Multiple cables from the battery bank to the Lynx Distributor ahead of the Lynx BS would reduce fuse and cable sizes.
The Lynx BMS includes a system DC disconnect so you could get away without disconnect switches between battery and Lynx Distributor.
Lets say you have a 800 AH battery bank and are running a 48 volt system (2 strings of 4 batteries in series). That's a continuous current of 200 amps. Running each string to the Lynx means you'd need a 200 amp fuse for each string.
My system is 12v.... in a camper van. I was planning on using a tinned copper bus bar (1 1/4"x1/4") to connect four 200 amp hour Victron batteries for a total of 800 amp hours. I can't use 4/0 wire due to the lack of flexibility to connect the batteries to the Lynx In..... so I was going use two wires for the positive and two wires for the negative as you suggested. Its about 4 feet from the battery bank to the Lynx In. What size wires would be reccomended.... I'm not sure how to figure it out with a DC calculator?
So your saying that the Lynx BMS will act as a disconnect? I opened it up and see the magnetic switch..... Is the disconnect powered via the touch screen or do I connect a wire from the Lynx BMS to a switch?
THANK YOU!!!
According to the manual:
https://www.victronenergy.com/battery-management-systems/lynx-smart-bms#manuals
it appears you can control the contractor from the GX device (aka Cerbo). There are also terminals for a remote system on/off switch.
Wire sizing really isn't possible until we know what your loads will be. That is AMPS vs Amp-hours.
Your best approach would be to connect each of the 4 batteries individually to the Lynx Distributor on the battery size of the Lynx BMS. Each wire should be the same length and sized to carry 1/4 of the total system current. (Note all positives should be the same length, all negatives should be the same length, but positives and negatives could be different lengths.)
Here's a calculator that may help:
https://www.southwire.com/calculator-vdrop
Lets say your max current draw is 1000 amps. Each battery wire should be rated for 250 amps. The calculator says you need 1/0 for each connection and with 5' would result in 0.29 volts drop.
If your system max current is only 500 amps, then you could get away with 3 AWG wires.
If you paralleled up two batteries locally and made two separate runs you'd double the current and would need 300 kcmil wires (larger than 4/0) each.
