Lithium Battery install

[Tony Ramirez]

I'm going to replace my 6 GC FLA for a couple of Lithiums. I already installed Buss Bars, right now 3 +cables goes to the Buss, along with the Solar +, 250A Brkr for the Inverter, 250A Brkr for the Jacks & house panel.

1) The Batts I'm looking at each have a 200A Continuous discharge w a 400A 10sec Max Discharge. I am planning on installing 2 circuit breakers between each battery and the Buss. Is 250A the right Amp size for these?

2)Will my Solar still charge the work going through the Buss, then the new Breakers to the Batteries?

 

[TacomaJoe]

A fuse or circuit breaker is installed to protect the wire. What is your wire size? Installation should be as close to the battery as possible (wire to the protection is not protected).

Your solar will charge the battery via the buss. Note that your buss needs to be rated for the total max current which is probably going to the inverter.

 

[Aussieguy]

Lithium (lifepo4) battery has it's own internal over current protection
it is suppose to shut off if it detects too much current is being discharged

You install a fuse to protect the wiring at the battery
as long as the fuse is rated for the wire size it will be safe

in short... you could put a 100amp fuse on the wire... wire is protected but you'll be blowing fuses all the time ....

SO you size the fuse to the maximum current you expect to
see drawn from battery then make sure the wiring is big enough FROM BATTERY to the BUS


PS.... make sure wiring also used in paralleling the batteries together are correct or oversized as well


the Inverter and other circuits on the BUS...... should have their OWN fuses/breakers to limit the current in that particular section.


If you are even slightly thinking of upgrading inverter or other power hungry 12v items
install the BIGGEST wire you can so that the wiring from battery to bus will be oversize
then you won't have to redo the that section of wiring if you buy a bigger inverter

 

[Tony Ramirez]

Thanks for the replies. I used 4/0 to the buss and a 600 Buss( might have been overkill but didn’t want to have to redo it later). The Buss is pretty much next to the batteries, cables about 15” long.

So the extra breakers aren’t really needed, since the batteries have their own BMS? Only if I want a way to shut off one or both batteries?

 

[shepardmike]

cable length

I have read on other forums that it's important that the wiring length is exactly the same between the bus bar and the batteries.

 

[Tony Ramirez]

The cables MIGHT have a 1/4-1/2” difference between the two, going to have to be close enough. 4/0 cable, that shouldn’t affect resistance between them.

 

[Aussieguy]

depends on how you wired up the parallel

a) each battery has positive and negative and goes to the bus separately
cable length should be the same .......... as close as possible

You can install a shutoff on the positive to each battery and turn them on/off at will

Just be careful not to drain a battery and then connect it to a full one.... then you'll see a lot of amps flow and how well you crimped the cables.

b) positive to positive then to load parallel (daisy chain )
negative to negative and then to frame
main positive on one battery ....... main negative on the other

length of cables not really a biggie factor

 

[MGD1961]

You should not daisy chain batteries. Each battery should have the same size and length cables. Both pos and neg. Going to a buss bar and then a primary cable with a fuse to the loads. Otherwise the first battery in the chain will get over worked over time and fail before the others in the chain. Could take a month. Could take years but it will happen. Why do it half a****. This is your chance to do it right. The difference in labor and money is minimal in the scope of the project.

 

[Tony Ramirez]

ALL 4/0 cables, same lengths (+/- 1/4-1/2")

Batt 1: + Fuse, then to +Buss, - to -Buss.
Batt 2: + Fuse, then to +Buss, - to -Buss

Pos Buss to Load w/ Breakers/ Fuses

Batt 1: - to -Buss
Batt 2: - to -Buss

Neg Buss to Shunt

Sound Right?

 

[Tony Ramirez]

I REALLY need to proof-read BEFORE i hit send.

I meant the Pos's go to the Pos Buss, and the Negs go to the Neg Buss.

 

[MGD1961]

ALL 4/0 cables, same lengths (+/- 1/4-1/2")

Batt 1: + Fuse, then to +Buss, - to -Buss.
Batt 2: + Fuse, then to +Buss, - to -Buss

Pos Buss to Load w/ Breakers/ Fuses

Batt 1: - to -Buss
Batt 2: - to -Buss

Neg Buss to Shunt

Sound Right?

Fuse between the battery and the buss is overkill. The BMS should take care of that part of the circuit but better over than under protection

Although if the fuse in that section of the circuit creates higher resistance on the positive than the negative it could “technically cause a cell imbalance in the battery “. But again the BMS comes into play. Also if you are charging your batteries properly they will balance automatically.

 

[Aussieguy]

I get/see a slight in-balance some days but at the end of charging
the 2 batteries are back to being well balanced
I was able to set the BMS balancer to work whenever the cells were above 3.4v charging or discharging the little included balancer gets more time to work.

Having bluetooth on each .... can be a battery saver
If you notice a big imbalance... start by looking for a bad/loose connection

BIG battery banks 4 or more batteries that are used daily suffer more from imbalance problems
consider adding a BATTERY balancer if your batteries are wired in series
or using busbars instead of cables to join batteries in parrallel.

given enough time... batteries in parallel will naturally balance themselves BUT don't ignore why they get out of whack in the first place...
find the bad connection or rethink HOW you have joined them.

 

[Tony Ramirez]

Thanks all. Just got my delivery date, next Tuesday. I went w 2 Epoch 460AHs. They have Bluetooth so I will pay attention to the cells(after I learn how to read all the data).

I guess I will not install the 2 fuses between each batt and the buss since it sounds like they aren’t needed.

 

[TitanMike]

I get/see a slight in-balance some days but at the end of charging
the 2 batteries are back to being well balanced
I was able to set the BMS balancer to work whenever the cells were above 3.4v charging or discharging the little included balancer gets more time to work.

Having bluetooth on each .... can be a battery saver
If you notice a big imbalance... start by looking for a bad/loose connection

BIG battery banks 4 or more batteries that are used daily suffer more from imbalance problems
consider adding a BATTERY balancer if your batteries are wired in series
or using busbars instead of cables to join batteries in parrallel.

given enough time... batteries in parallel will naturally balance themselves BUT don't ignore why they get out of whack in the first place...
find the bad connection or rethink HOW you have joined them.

With 4/0 cables and and only a minor difference in cable length there will be a VERY negligible difference in charging or discharging voltages at the batteries. At 50-60 charging amps difference is only a few milliamps.

Often the voltage drops over the several connection points will total far more than the voltage drop across an extra 0foot or two of heavy cable, especially a 4/0 copper one.

The need for equal length conductors becomes necessary in huge battery banks like employed in large solar power systems.

The average RV system will never see a difference but everyone is free to believe what they want.

 

[MGD1961]

Part of my point was if you don’t fully charge the battery to 100% periodically the cells will get out of balance. More about your charging regime than cable lengths. The difference between individual batteries, not the cells, has everything to do with cable lengths and resistance in connections. It’s not a feeling or belief. It is fact as my training and experience have shown me.

 

[Comanchecreek]

My layman's recommendation is to buy quality circuit breakers. I have had problems with some of the cheapies on Amazon.

 

[Complication]

How did it go? Any pictures? Did you use any local help?

I too want to replace my dying 6v marine batteries and had a pair of Epoch 460ah in mind.

 

[Tony Ramirez]

How did it go? Any pictures? Did you use any local help?

I too want to replace my dying 6v marine batteries and had a pair of Epoch 460ah in mind.

Have had the 2 460s in for about 3 weeks, so far, GREAT! Still playing with the Victron charge parameters (talking to Epoch, reading their manual, and reading the forums.) Probably go with what Epoch told me.

Anyway, I used 4/0 same length + cables and 4/0 same length - cables to Buss Bars. I did not put fuses on the + sides, talking to Epoch they said they were not necessary. BMS and my existing breakers and fuses were fine.

I did a short weekend dry camping trip, wasn't shy with any lights, water pump, used the convection oven, residential fridge, brewed coffee in the mornings, NEVER phased them. Solar had them back full by 1PM.

I left the fridge on while back at home(before would turn it off because sometimes the FLA GCs would go low, especially on cloudy days.) So far, even with a couple rainy, cloudy days, I haven't gone below 50%. I'm in there trying to use lights and TV too. Even though I usually have a marine layer to deal with, I'm usually back full by 1-2.

The pic is from when I had put them both in, but was charging the 1st, so the 2nd isn't hooked up yet.

 

[Tony Ramirez]

Forgot, I did it all myself. With basic knowledge, it was pretty easy. Plus< others call me cheap, I like to say thrifty. But I also like to know how everything is done, and it seems nowadays, sometimes I know more than the guy I'm paying to do something.

 

[Complication]

Thanks for the info.

I'm still trying to figure out all the parts I would need. Probably start another thread with specifics.