Hypothetical for now - Lithium question

[SimonM]

If you have a large Lithium battery in-situ, c.460ah, and wanted to add an identical unit a short while after the initial one, but can only put it perhaps 1200mm away from t’other in a remote storage box, is that a viable option given adequately sized cables between the 2 - to handle perhaps a couple of hundred amps?

 

[trevskoda]

If you have a large Lithium battery in-situ, c.460ah, and wanted to add an identical unit a short while after the initial one, but can only put it perhaps 1200mm away from t’other in a remote storage box, is that a viable option given adequately sized cables between the 2 - to handle perhaps a couple of hundred amps?

Yes i would say, but best use h duty battery cables like on the battery to starter, most motor chops will cut to length and crimp on whatever ends you wish, or you may just be able to fit inside clamp you have, best to ask wildbus to be honest.

 

[Admin]

If you have a large Lithium battery in-situ, c.460ah, and wanted to add an identical unit a short while after the initial one, but can only put it perhaps 1200mm away from t’other in a remote storage box, is that a viable option given adequately sized cables between the 2 - to handle perhaps a couple of hundred amps?

1. Parallel wiring is fine at 1.2 m if the cables are correctly sized and the terminations are good. At “a couple of hundred amps”, cable resistance and voltage drop become the limiting factors — not the fact that the batteries aren’t touching.
2. Use a heavier interlink than the van feed. The interlink can carry both load-sharing current and equalisation current, so don’t skimp.
   
   • If the van feed is 25mm², stepping up to 35mm² is a minimum.
   • If there’s any chance of sustained 200A+ or inverter surge currents, 50mm² (or even 70mm²) is the more “definitive” answer.
     
3. Balance the take-offs so both batteries share current properly. The simplest proven method is the “diagonal” connection:
   
   • Take the main positive from Battery 1
   • Take the main negative from Battery 2
   • Link positive-to-positive and negative-to-negative between the batteries with the same CSA and ideally the same length
     This helps avoid Battery 1 doing all the work while Battery 2 just “floats along for the ride”.
     

Non-negotiables (these are the safety bits)​

• Fuse each battery on its own positive, as close to the battery as practical. Otherwise, if there’s a fault, one battery can dump into the other and the interlink cable becomes the “fuse” (bad day).
• Match state of charge / voltage before you connect them. Don’t parallel a half-flat battery to a full one — lithium can equalise with a big inrush current. Best practice is to fully charge both, let them settle, confirm voltages are close, then connect.

The gold standard is running both batteries to common positive and negative busbars (or a Lynx-type bus system), using:

• the same cable size
• the same length
• the same fusing/isolators
  That guarantees good sharing and makes future expansion cleaner.

Bottom line: 1.2 m away is fine. Do it with properly sized cable, balanced take-offs, and individual fusing/isolators, and it’ll behave like one bigger battery bank.

 

[SimonM]

Many thanks for the additional information, it was the distance issue that concerned me most

 

[Geek]

For this application I would suggest doubling up. Two 25mm is the same as one 50mm, but easier to install.
I have used 50mm cables in the past, but bending them round corners is more effort than it's worth.

If you want the two batteries to share evenly, have the positive feed go to one battery and the negative go to the other, but personally, I'd not worry. Just join them with fat leads.

 

[Robmac]

For this application I would suggest doubling up. Two 25mm is the same as one 50mm, but easier to install.
I have used 50mm cables in the past, but bending them round corners is more effort than it's worth.

If you want the two batteries to share evenly, have the positive feed go to one battery and the negative go to the other, but personally, I'd not worry. Just join them with fat leads.

I disagree.

I used 70mm² cables in my installation and I found it to be easy to watch @MERL bend them.