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amartins asked

BMS 12/200 vs VE Bus BMS and Cyrix Lt-charger - automotive application

Hi,

Following a setup, I am building for a campervan I have a question regarding two options for BMS. [1]

Option 1. Use a BMS 12/200.

Option 2. Use a VE Bus BMS and Cyrix Lt-charger.

What are the advantages and disadvantages of both options? To my understanding the use of a BMS 12/200 force the use of an isolated DC/DC in order to not connect the lithium battery to ground. [2] The use of a VE Bus seems more straight forward regarding this topic. [3]

Thank you.

[1] https://community.victronenergy.com/questions/3143/complete-system-architecture-for-campervan-640w-so.html

[2] https://www.victronenergy.com/upload/documents/Datasheet-BMS-12-200-EN.pdf

[3] https://www.victronenergy.com/upload/documents/Datasheet-Cyrix-Li-ion-120-A-EN.pdf

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1 Answer
Johannes Boonstra (Victron Energy Staff) avatar image
Johannes Boonstra (Victron Energy Staff) answered ·

Option 1 gives you the simple to install system where there are no firmware/assistants or whatever is needed. but only on 12Vdc systems. The huge benefit is that the 12/200 can limit the alternator current by the selection of fuse you place on the AB side. ( and an alternator need to be protected to avoid damage) Negative side here is that the input/output current is limited to 200A on the LB side which means the 3kVA inverter is about maximal what can be connected. Beside this the BMS controls the minus/neg side so this means that IF there are loads in the van using the ground as conductor (like a small interior light sometimes do) the power may come from the starte battery when the BMS has blocked the discharge. So to avoid this there must be a isolated DcDc converter used that makes sure the Dc loads are powered from only the lithium battery. The 12/200 has a " cyrix" function built in so also there an extra relay isn't needed. Option two has the ability to work on 12,24 and 48V systems and there is not a restriction on power there (as far the BMS is concerned). The installation needs however a firmware setup in the Ve Bus devices to be controlled by the BMS , and ALL other sources/loads need to be controlled by either a battery protect ( preferred as this has a minimal idle consumption ) or Cyrix-li-x relay

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chrisryan43 avatar image chrisryan43 commented ·

Hello,

I found this thread because i was wondering the same thing. I wasnt sure whether best to start a new thread or tag on to this but let me know if it should be a new thread.

I have just installed option 2 (although using a cyrix-li-ct rather than a cyrix-li-charger). Do the same arguments apply to the cyrix-li-ct as for the cyrix-li-charger?

Weirdly, I can't find the BMS 12/200 on the Victron site (just on 3rd party sites) so i am wondering if it has been discontinued (possibly replaced by the Cyrix-Li-ct)?


Also, i have found 2 documents (links below). Why would one be used over the other?

1. showing the BMS 12/200 doing everything



2. where it is working in conjunction with a VE.Bus BMS.

Many thanks

Chris

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