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Lyndon Lewis avatar image

Narrowboat Lithium set up.

Hi, We are moving over from lead acid to lithium batteries (the victron smart ones) and will be updating our 12v system up to the inverter and DC panel(s)

1. Do we need a separate battery protect for under voltage or can we use the relay on the BMV 712

2. We have a sterling alternator to battery charger will that work through the Cyrix Li-ct

3. Is there anything else you would suggest we need to change in the above diagram.


Cheers,


Lyndon

Lithium battery Smart
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minor comment - if you're breaking out a group for sensitive DC loads, suggest that you pair up positive and negatives for long runs where possible (i.e. minimise loop areas) and maximise separation between runs for sensitive loads away from others (i.e. maximise distance between sensitive and non-sensitive loops).


2 Answers
JasonTav avatar image

The battery smart manual states "each battery or string of batteries must be protected by a fuse" so to adhere to this you need a fuse near to each batteries positive pole.



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Jono (Victron Energy Staff) avatar image

Hi Lyndon,

Here are my suggestions.

Yes, you do require a separate battery protect to protect against under voltage. The relay in the BMV 712 is only a very small relay and not designed for high currents.

See JasonTav answer regarding fuses, this is required.

As the MPPT and MultiPlus and the Color Control all talk with each other, there is technically no need for a Cyrix Li-Charge between the MPPT / lithiums. You could leave that in however if you want an extra level of protection.

It’s also highly recommended to use the BMV 712 relay to disconnect the ‘allow to charge’ cable (that goes to your charge sources) from BMS VE.Direct so you can reduce the voltage cut off manually within the Victron Connect App. This is better than leaving it to the BMS. I have mine set to 14.2v for this for example.

I am not an installer however so just my observations and things I've learnt from Victron along the way.

Thanks, Jono

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Hi! can you please explain the usage of BMV relay? Do you mean that in addition to the BMS you would be able to manually cut the load disconnect? So both would work at the same time, right?

Yes exactly that. The BMS is the last option to cut the high voltage before it gets too high that it would cause damage.


If you use the BMV712 relay you can stop the high voltage way sooner when things are calm and the battery not stressed. It will look after the battery more and you have piece of mind.