Add extra Lithium Batteries in Parallell

[Marie-Claire]

Hi all
We have now collected our new rapido 8096 it comes fitted with a tbb m12 100ah lithium battery. It is charged by b2b and a 160w solar panel. On the previous van I had 2 renogy 100ah lithium batteries which I have kept. My first plan was to replace the tbb with the 2 matching renogy batteries but is there any reason I cannot just add them all in parallel to create a 300ah bank. I dont actually need that much power but as I have the batteries it's no loss.
Would I be doing any harm to the charging system to do this?

Tia

 

[MichaelT]

No it's fine but connect them to bus bars .

 

[LithiumConvert]

I don't know why you could not use all three. But charge them all to the same voltage before connecting them.

Your charging current will be limited by the chargers, not by the batteries. It will just take longer to charge.

Don't forget that if they are all very close to each other the you should have fuses at each end of the +ve connecting link.

 

[LithiumConvert]

Don't forget that if they are all very close to each other the you should have fuses at each end of the +ve connecting link.

Of course, that should have said "If they are NOT close to each other"

 

[Lenny HB]

With Lithium even if close to each other it is still wise to fuse each battery.
When connecting you need to do it via bus bars and the leads from each battery need to be the same size and the same length.

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[Marie-Claire]

Thanks guys, there is enough space for them to go side by side so will get a set of leads made up, what size of cable should I use as a minimum ? The length will be relatively short 450mm max.

 

[Lenny HB]

Size of cable depends on length & load for your use 16mm² will be OK and I would fit a 50 amp midi fuse inline with each battery.

 

[Marie-Claire]

Cheers lenny appreciated, so I would need a 5 post bus bar, 1 each for the 3 batteries 1 for the main cable leaving to the consumer unit and 1 for the inverter live.
Thanks

 

[Lenny HB]

Cheers lenny appreciated, so I would need a 5 post bus bar, 1 each for the 3 batteries 1 for the main cable leaving to the consumer unit and 1 for the inverter live.
Thanks

4 will be fine as you can connect more than one cable on a post.
Fuse each battery before the bus bar then separate fuses for distribution unit & inverter.

 

[Tude]

Hi all
We have now collected our new rapido 8096 it comes fitted with a tbb m12 100ah lithium battery. It is charged by b2b and a 160w solar panel. On the previous van I had 2 renogy 100ah lithium batteries which I have kept. My first plan was to replace the tbb with the 2 matching renogy batteries but is there any reason I cannot just add them all in parallel to create a 300ah bank. I dont actually need that much power but as I have the batteries it's no loss.
Would I be doing any harm to the charging system to do this?

Tia

Renogy have pouch cells so need bulking all the time virtually there’s no float maybe your other lithium are different charging profiles

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[splitfirebus]

I personally wouldn’t do that. Stick with the same batteries make, size etc or you may create uneven charging and or discharging of the battery cells over time.

 

[MichaelT]

I personally wouldn’t do that. Stick with the same batteries make, size etc or you may create uneven charging and or discharging of the battery cells over time.

Or you may not, so far ours are charging and discharging pretty evenly but i never plug in only have solar and B2B

 

[Jabstatt]

Also make sure your load is connected properly
Positive on battery one negative on battery three to balance as much as possible

Size cables for highest load, maybe inverter, assume worst case!

Tony

 

[Marie-Claire]

Thanks all I can work out what I need now

 

[Marie-Claire]

Just looking at what I need to order, just need to confirm that on the positive side each battery is wired seperatly to the bus bar with a midi fuse then the original main cables connect to the bus bar also. The wiring is then repeated on the negative side to a seperate bus bar.
Tia

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[RogerIvy]

MRBF fuses are pretty easy to install. Cost a bit more but they are good.

We’ve had four considerably different batteries hooked up for about a year to see how they work together. The battery with the lowest internal resistance will do most of the heavy lifting and will clock up more cycles. But other than that we experienced no problems.

 

[LostInSpace]

With Lithium even if close to each other it is still wise to fuse each battery.

A good point, and the fuses need to be at the battery in each case.

But I don't see why it only applies to lithium.

 

[LostInSpace]

Just looking at what I need to order, just need to confirm that on the positive side each battery is wired seperatly to the bus bar with a midi fuse then the original main cables connect to the bus bar also.

Yes, but remember that, if each battery is fused at, say 30 amp, then that adds up to 120 amps feeding the bus bar, if there are four batteries.

So, each of the original main cables needs to be fused appropriately for its intended load (and wiring size) when connected to the bus bar.

 

[Lenny HB]

A good point, and the fuses need to be at the battery in each case.

But I don't see why it only applies to lithium.

Good practice with any batteries but quite normal with lead batteries if next to each other just to fuse overall.
Always recomended to fuse each battery with Lithium due to the very high sustainable current they can deliver particularly if you had a fault on the BMS and it didn't shut down.

 

[Jimbohorlicks]

An interesting utube video of tests carried out on 3 wireing configurations to 3 lithium batteries in parallel

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[CleverTrevorUK]

1.Lithium Leisure Battery's and a Lead Acid engine battery? If a couple of Lithium leisure batteries were used as a replacement for previously installed Lead Acid batteries, Would there be a charging conflict between the starter battery and the lithium leisure batteries?

 

[CleverTrevorUK]

Or do the Lithium batteries if installed need to be separated from the Vehicle charging system?

 

[Gromett]

An interesting utube video of tests carried out on 3 wireing configurations to 3 lithium batteries in parallel

Interesting but I think the results are worst case scenario because he is using cables that are too small and that will show a higher resistance?
I wouldn't use such thin cables for 130A load...

That is how it looks to me..

 

[Jimbohorlicks]

Interesting but I think the results are worst case scenario because he is using cables that are too small and that will show a higher resistance?
I wouldn't use such thin cables for 130A load...

That is how it looks to me..

I would suppose the cables from each battery to the bus bar are ok at around 40 amps each.
For the inverter taking the 130amp load, like many are often supplied with cables which should cover the max range of the inverter?

 

[Gromett]

I would suppose the cables from each battery to the bus bar are ok at around 40 amps each.
For the inverter taking the 130amp load, like many are often supplied with cables which should cover the max range of the inverter?

I was specifically commenting on the 1st and 2nd test not the bus bar test.
The resistance of the cables would have an effect.
Compare 16mm² cable to 50mm² cable. A lithium battery has a very low internal resistance so the resistance of the cable has a very big impact.
If he had 50mm² cable the resistance on the additional links would have a much lower effect and reduced the disparity we saw in test 1 and 2.
In fact in test 2 I think it would have pretty much reduced it to zero.

My view is. Even if you don't need it for current carrying capacity, spec the link cables to be as big as possible to reduce the resistance.

I could do some network calculations using some sample internal resistance values. But life is too short for hypotheticals.
The Bus bar is a better solution, but speccing the cables correctly is just as important. I suspect he deliberately used smaller cables to accentuate the demonstration.

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[Raul]

I was specifically commenting on the 1st and 2nd test not the bus bar test.
The resistance of the cables would have an effect.
Compare 16mm² cable to 50mm² cable. A lithium battery has a very low internal resistance so the resistance of the able has a very big impact.
If he had 50mm² cable the resistance on the additional links would have a much lower effect and reduced the disparity we saw in test 1 and 2.
In fact in test 2 I think it would have pretty much reduced it to zero.

My view is. Even if you don't need it for current carrying capacity, spec the link cables to be as big as possible to reduce the resistance.

I could do some network calculations using some sample internal resistance values. But life is too short for hypotheticals.
The Bus bar is a better solution, but speccing the cables correctly is just as important. I suspect he deliberately used smaller cables to accentuate the demonstration.

View attachment 957131


View attachment 957132

And to top it off, a buss bar amps rating it gets trickier to calculate. At a minimum, should be the sum of all cable ratings connected to it. Hence victron Lynx bars are 1000A rating, for 4x 250A connections incoming.
I have seen many cases where 3 or 4 35mm2 cables are connected to 250-300A bars. Bonkers. Even 12v planet sell one with 3 midi and 1 mega that has a bar of 2x15mm, 30mm2. I use one of them but added 2 plates of 3x15mm to the existing.

 

[Bessy765]

2 x 100 amp Transporter Lithium, 700 watts of solar, Victron 12/2000/80 inverter/charger.

That’s my cables better over the top than under??

 

[treblid]

And to top it off, a buss bar amps rating it gets trickier to calculate. At a minimum, should be the sum of all cable ratings connected to it. Hence victron Lynx bars are 1000A rating, for 4x 250A connections incoming.
I have seen many cases where 3 or 4 35mm2 cables are connected to 250-300A bars. Bonkers. Even 12v planet sell one with 3 midi and 1 mega that has a bar of 2x15mm, 30mm2. I use one of them but added 2 plates of 3x15mm to the existing.

But even a 25mm² by 100mm busbar would only drop 0.642% (0.0770 volts) at 500A. And that's assuming all the current passes along the whole length.
I don't see the issue with the 12V Planet 30mm² bus bar?

 

[Bessy765]

2 x 100 amp Transporter Lithium, 700 watts of solar, Victron 12/2000/80 inverter/charger.

That’s my cables better over the top than under??

 

[Raul]

But even a 25mm² by 100mm busbar would only drop 0.642% (0.0770 volts) at 500A. And that's assuming all the current passes along the whole length.
I don't see the issue with the 12V Planet 30mm² bus bar?

Buss bar length is irrelevant. Hence I said to calculate correctly it gets tricky. It's not the same as a cable calculation.
If you have a Lynx, 1000a bar, measure the bar and the result of mm2 divide by 10. That would give you min requirement of mm2 bar per 100A connected. So the bar is 8x30mm, 240mm2, that's 24mm2 per 100A.
The 12v planet sure its not a problem, as long as you keep the total ampacity connected to be ok with the 30mm2. It's the user duty to decide what it connects to it.
And don't even contemplate to run 500a through a 25mm2 bar, you will need 120mm2. You can also make it up by stacking multiple plates, as long as is bolted with spring washers, and the plates are completely flat, really flat.

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