Yes..and if you need two cables with lugs to stack from the same side you simply flip the first one upside down as long as there is enough clearance to what you are attaching it to.
Equal length battery connections, double landed buss bars
- Thread starter KRP
- Start date
Another fuse on the positive side of the bus bar sounds redundant, please explain, I do have a fuse inline on the cpap plug, just not shown
Dagoth Ur Does Solar
Solar Enthusiast
Am I wrong here that the "correct" or "optimal" way to parallel batteries would be to use cables off to a dedicated busbar, like what's done on bigger server rack setups?
I've been hemming and hawwing on how to parallel my 12v setup in the future, and maybe I'm making too much of a fuss about needing to use busbars for the batteries.
MisterSandals
Participation Medalist
The 300A fuse is to protect the 300A capable wiring from the battery, the cutoff switch and bus bar. From the bus bar a fuse to protect the wire to the inverter. Also from bus bar, a fuse small enough to protect the wire to the CPAP socket and the socket itself.
Since you have a fuse to protect the CPAP wire and socket, that helps quite a bit because otherwise that would have all needed to handle 300A.
With this new info, i guess the question is whether the 300A battery fuse is sized for the battery wiring, cutoff switch, bus bar and wiring to the inverter properly.
You'd have much less cabling/mess if you connect them to a busbar and then the cable from the busbar is of adequate size to handle all the amps.
MisterSandals
Participation Medalist
I think if you can get the wiring and connections reasonably close in terms of total resistance, you can easily do as well as bus bars with equal length wires. So yes, maybe overthinking.
The inverter charger from Renogy specifies 4/0 cable and a 300 amp fuse, the bus bar is also 300 amp rated
Dagoth Ur Does Solar
Solar Enthusiast
I'm mostly running up against the limits of 12v I think. If I wanted to pull a large load off it- let's say I need to run my 3000W 12V inverter at a high load for an hour- obviously not ideal, but I really get into the territory of needing beefy bus bars, which adds more cost. Quality 500A busbars for example, do not seem to be cheap.
I was thinking just buying 4/0 gauge wire, fusing all my positives, direct paralleling the batteries and calling it a day. Then use a busbar to break out to my inverters and such.
I'll think on it and go back to the drawing board.
I'm also weighing just saying "screw it" and considering just saving longer term for a 48V system now that I have my feet wet.
MisterSandals
Participation Medalist
If your total loads are the inverter and just the CPAP (minimal) then you should be good as pictured. Where the 300A fuse is located, it is for all of your loads, not just the inverter. If you have another significant load off your bus bar, then your battery fuse needs to be bigger and the 300A would need to go between bus bar and inverter. But, i cannot tell what is not pictured.
The cpap is the only thing at this time I will have on the bus bar so I can use the lifepo4's at night with my cpap and the inverter off, I am thinking about going from the bus bar to the converter through a Blue seas 11001 3 position battery switch so I can power my heater blower like pictured
Attachments
MisterSandals
Participation Medalist
Sorry i am not familiar with what you are trying to do with the one way diodes.
If you're not sure yourself, it would make for an interesting thread. I'd live to learn about this.
12VoltInstalls
life passes by too quickly to not live in freedom
I have three 12V LiFePo batteries paralleled on the bus bars. For reasons many can imagine but I won’t expound, I reasoned that the ‘loss’ at the busbar was less likely to have continuity problems that cause heat problems (aka fire risk) and the lesser number of potentially ‘hot’ terminals floating around if disconnecting a battery just makes the busbar landing make sense.
The ‘efficiency’ or other more illogical platforms people argue on are well under <0.5% of typical capacity in the worst cases so landing on a busbar in practical terms is a non-issue. Plus one could argue the ‘discharge time’ at moderate levels via busbar is only a minute or so difference from a psychotic gold-plated cables connection so really: who cares in practical terms??
The busbar plan on my LiFePo’s is WAY simpler than it was with the eight lead acid batteries, and I don’t think LiFePo cares as much.
I disagree. The lug should be in contact with the terminal. The bolt head should have a lock washer and then flat washer up against the lug and on the nut side, a flat washer up against the terminal. Try to use stainless steel. torque correctly. Then torque again after 1-2 minutes as copper tends to relax. if possible, maybe coat the connection with Kopr Kote if concerned about battery acid at the poles in the future.
His original diagram showed a washer sandwiched between the two lugs. You do not want that since unless it is a pure copper washer it would add a lot of resistance.
Fuses on battery chains should be on the positive terminal at the end of the chain. Breakers are very different from fuses. Breakers react to arcing and to current load. The current load is an over time reaction and breakers have different reaction times to overcurrent usually listed as types A,B,C,D curves for tripping. A fuse will react to a current surge much more rapidly than a breaker and act to protect your batteries or equipment behind it while a breaker is really designed to protect the wiring from overheating and causing a fire in walls, conduit, etc and then short circuiting and ARCing.
The lug should be up against the terminal on one side of the terminal. then a washer up against the bolt side of the terminal and a washer and lock washer on the bolt head side. But the lug remains in direct contact with the terminal.
That's what was stated should be done. The issue was with this diagram which showed a washer between two lugs which is incorrect unless the washer is pure copper.
My motorhome has a BCC that would try to charge the lifepo4 batteries if I failed to have the switch in the right position. The BCC company said it could hurt the BCC and most likely hurt the altenator. The one way diodes would prevent that.
12VoltInstalls
life passes by too quickly to not live in freedom
Nor do you want this:
No- the battery terminals should not depend on a washer or a bolt for conductivity on a busbar or battery terminal. The bolt is there ONLY to achieve 100% tight contact with the terminal surface, and a washer interrupts that goal on both sides of its surfaces.
A washer OVER the cable terminal end aids in creating good contact with the battery terminal.
Huh. Never had an issue in over 7 years. Followed Trojan manufacturer's installation. Battery terminal and the lug. Side of lug placed up against battery terminal. Bolt has lock washer inserted first, then flat washer. This is then inserted through the hole in lug and terminal. Flat washer contacts either the terminal or the lug. On threaded side of bolt, flat washer inserted so that the flat washers sandwich the lug and terminal. Then nut threaded onto the bolt and tightened to torque specs. The lock washer keeps tension over time. This is how its done. But you listen to whoever you want. It's your system.
