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kwalstad · 08-07-2021, 07:09 AM

I am using 2 lifepo4 8s24v batteries, I will run them in parallel. My question do I actually have to wire the batteries together or can I hook them to a bus bar to achieve the parallel connection?

amosnandy · 08-07-2021, 07:23 AM

Quote:

Originally Posted by kwalstad

I am using 2 lifepo4 8s24v batteries, I will run them in parallel. My question do I actually have to wire the batteries together or can I hook them to a bus bar to achieve the parallel connection?

As long as the wiring is correct a buss bar is not a problem. Just make sure both the cable and bus bar are adequate size for the current draw you will be pulling.

astrocamper · 08-07-2021, 11:33 AM

I have seven 100 amp-hour batteries, each hooked with 2/0 cables to a positive and negative bus bar rated for 650 amps. I use 4/0 from the battery bus bars to the rest of the circuit involving the VE Mulitplus 3000VA inverter/charger. This includes the catastrophic fuse, VE BMV-712 shunt, battery disconnect switch and secondary smaller bus bars for the rest of the DC related connections.

I prefer bus bars over single posts as interconnect points.

757driver · 08-07-2021, 11:44 AM

Quote:

Originally Posted by kwalstad

I am using 2 lifepo4 8s24v batteries, I will run them in parallel. My question do I actually have to wire the batteries together or can I hook them to a bus bar to achieve the parallel connection?

Busbar would actually be better. Make sure each set of cables are of the same length.

hclarkx · 08-08-2021, 11:54 AM

Quote:

Originally Posted by kwalstad

I am using 2 lifepo4 8s24v batteries, I will run them in parallel. My question do I actually have to wire the batteries together or can I hook them to a bus bar to achieve the parallel connection?

Either will work. Ideally you will have the same cable sizes and lengths running from the positive busbar to the positive terminals and likewise from the negative busbar to the negative terminals. And if you parallel at the batteries with cables, ideally you feed your distribution system from the positive terminal of one battery and the negative terminal of the other battery; and again, have the same size and length of cable between the two positive terminals and between the two negative terminals.

augie1955 · 08-08-2021, 12:20 PM

Quote:

Originally Posted by kwalstad

I am using 2 lifepo4 8s24v batteries, I will run them in parallel. My question do I actually have to wire the batteries together or can I hook them to a bus bar to achieve the parallel connection?

From Victron Energy. And I prefer bus bars in all my builds.

Persistent · 08-08-2021, 12:22 PM

A cable or a buss bar do the same thing. Fewer connections do perform better for charging. There is lower resistance in fewer connections.

However some lithium battery terminal designs may not work with a buss bar. Or for that matter with some cable connectors. Battle Born brand lithium's have an installation instruction regarding fit on the terminals. Bad fit can cause terminal failure. See installation instructions for alternatives or contact support.

757driver · 08-12-2021, 10:05 AM

Busbar system I am referring to is a separate busbar for + and - with each set of battery cables attached to the busbars and not each battery connected in parallel to the next one. Will work with any lithium battery and is much easier to take one battery out of the mix for monitoring or if one fails.

vsheetz · 08-12-2021, 10:13 AM

I have three 200ah lithium batteries. Each wired in parallel with equal length cables to bussbars. All loads and charging through the bussbars.

Sent from my SM-J737T using iRV2 - RV Forum mobile app

hclarkx · 08-13-2021, 12:37 AM

An idle thought ...... when connecting LiFePO4 batteries in parallel, whether by cable or busbar, it's essential that they be at the same SOC and voltage when the connection is made. This means connecting wires with some hefty energy behind them (with only the bms providing protection). This is not to say that this is a problem as it's done often. But, my preference is to have a switch of some kind, maybe a $30 circuit breaker, between each battery and the bus. This way the batteries can be connected with the breaker open and checked for SOC and voltage before the breakers are closed to parallel the batteries.

Those breakers also make it easier to take one battery out of service for any issue as 757 suggests. Multiple breakers, one on each battery, are also an alternative to a single large (and costly) circuit breaker on a large inverter.
Circuit breakers up to 150 amps are readily available. Large ones aren't and get very expensive (good ones). So a breaker for a large inverter that may draw over 150 amps, the required 200 or 250 amp breaker is avoided. A fuse is an alternative, but having switching available for diagnostics and the like makes circuit breakers desirable.

Note, Bussman makes CB-285 (and 185) breakers up to 150 amps. No-name brands do come up to 250 amps but are not reliable in my experience.

Both my son and I have three batteries and have a circuit breaker on each battery and no breaker on the inverter.

One does need to be sure that these battery breakers are never opened unnecessarily since it's essential to "balance" the batteries before closing them if they've been open for any length of time.

Circuit breakers could be used in a non-bus system though that would be a bit messy and might drive one to use a bus.

astrocamper · 08-16-2021, 01:01 PM

I use a catastrophic fuse and a disconnect switch that is rated for 600 amps continuous, 900 amps for 5 minutes or 1750 amps for 30 seconds. My inverter/charger only peaks at 6000VA so the switch is up to the task.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

When I added 3 batteries to my system I brought them all up to 100% state of charge before adding them to prevent battery to battery current flow.

paul65k · 08-17-2021, 04:11 AM

I have 8 105Ah LiFePO4 batteries connected via parallel and series (24V) then connected through a Victron Lynx power distribution/fusing system.

If you are only connecting in parallel (12V) then I would go directly to a bus bar or Lynx module and you'll have a very clean and well functioning system IMO

hclarkx · 08-17-2021, 02:05 PM

Quote:

Originally Posted by paul65k

I have 8 105Ah LiFePO4 batteries connected via parallel and series (24V) then connected through a Victron Lynx power distribution/fusing system.

If you are only connecting in parallel (12V) then I would go directly to a bus bar or Lynx module and you'll have a very clean and well functioning system IMO

Paul,

Nice battery setup. Very neat. I'm curious though, the red bar picks up the positive terminals of each 12V pair and is supported above the terminals in order to clear the negative terminals if I'm seeing correctly. The question is what hardware did you use to support the copper bar? Are there copper links under it that I can't see?

paul65k · 08-19-2021, 08:36 AM

Quote:

Originally Posted by hclarkx

Paul,

Nice battery setup. Very neat. I'm curious though, the red bar picks up the positive terminals of each 12V pair and is supported above the terminals in order to clear the negative terminals if I'm seeing correctly. The question is what hardware did you use to support the copper bar? Are there copper links under it that I can't see?

Actually it's a little difficult to see in the picture but there are standoffs on the terminals with the bars.....these were provided with the batteries (Lion Energy 1300UT). This allows the 4/0 wires that are used to create 4 sets of batteries @24V.

I used stainless bolts vs. the wing nuts provided which allows us to torque the bolts to a factory spec