Wiring between Batteries and Multiplus 3KW 12V (FR/EN)

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biluf asked Feb 18, '24

Wiring between Batteries and Multiplus 3KW 12V (FR/EN)

English below

Bonjour,

Je suis en train de préparer le passage à deux batteries Lithium 200A en parallèle sur mon bateau et je souhaite installer le convertisseur/chargeur Multiplus 3KW 12V.
J'ai une question cependant. Sur beaucoup de schémas que propose Victron, pour la connexion du positif entre les batteries et le convertisseur 3K, ils relient les 2 pôles de la batterie sur un busbar avec ce qui semble être des câbles de 70mm², jusque là je suis d'accord mais ils relient ce busbar à un autre avec un unique câble qui ressemble à un 70mm² aussi et ensuite deux câbles repartent vers le convertisseur en 50mm² sans doute comme indiqué par le manuel de cet appareil.

N'y a t'il pas un goulot d'étranglement possible entre ces 2 busbars ?
Est ce possible car le câble de 70mm² serait très court ?
En fait ce serait un câble de 90mm² ?
Que préconisez vous comme branchement sur cette partie ?

Merci beaucoup.

Un des exemples de schémas : https://www.victronenergy.com/upload/documents/MultiPlus-3KW-120VAC-12VDC-400Ah-Li-VEBus-BMS-generator-MPPT-BMV-Cerbo-Orion-Tr-Smarts.pdf

______________

Hello,

I'm preparing to switch to two 200A Lithium batteries in parallel on my boat and I'd like to install the Multiplus 3KW 12V converter/charger.
I have a question though. On many of the diagrams proposed by Victron, for the positive connection between the batteries and the 3K converter, they connect the 2 poles of the battery on a busbar with what seems to be 70mm² cables, so far I agree but they connect this busbar to another with a single cable that also looks like 70mm² and then two cables go back to the converter in 50mm² no doubt as indicated by the manual for this device.

Isn't there a possible bottleneck between these 2 busbars?
Is this possible, as the 70mm² cable would be very short?
Would it actually be a 90mm² cable?
What connections do you recommend for this part?

Translated with DeepL.com (free version)

Thanks a lot

One of the sample diagrams: https://www.victronenergy.com/upload/documents/MultiPlus-3KW-120VAC-12VDC-400Ah-Li-VEBus-BMS-generator-MPPT-BMV-Cerbo-Orion-Tr-Smarts.pdf

wiring diagram

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Answer 1 · 2024-02-18T09:33:39Z

Alex Pescaru answered · Feb 18 at 09:33 AM

70mm is enough for that short distance. The voltage drop is insignificant for that distance.

The voltage drop is bigger on the fuses before and after, than on that cable.

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Answer 2 · 2024-02-18T09:53:36Z

biluf answered · Feb 18 at 09:53 AM

Ok thanks.

So it's ok because it is a small cable.

Now what if this 70mm² cable was 1,5m in length ?

I suppose it's better to cover that distance with the 2 50mm² cables ?

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Answer 3 · 2024-02-18T10:03:55Z

Alex Pescaru answered · Feb 18 at 10:03 AM

Some say that the voltage drop from battery to load(s) must be under 2.5%, for full load. That, for a 12V system, is 0.3V or 300mV.

I, for one, have always aimed for less than 1%. That means 0.12V or 120mV. But sometimes, our installation is over-dimensioned.

Have a read at this: https://www.victronenergy.com/upload/documents/The_Wiring_Unlimited_book/43562-Wiring_Unlimited-pdf-en.pdf

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