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rupert avatar image
rupert asked

Victron Smart Lithium Battery Help! :)

Hello - I need help! :)

I am putting a 12V electrical system into a van and want to include lithium batteries but am getting stuck. The charging sources will be 300w solar (via a Victron Solar Charge Controller) and the engine battery (via a Votronic 12V/12V 30A Battery-to-Battery Charger). There will be no grid / shore power.

The plan is to use one Victron Smart Lithium LiFePO4 12.8V 150Ah Battery. I have attached a draft circuit diagram. Van Circuit Diagram Image 05.05.2020.png

My difficulty is what I need to make the lithium battery work and keep it protected.

1. Do I need a BMS with only one battery (ie no battery bank) and which one - Victron BMS VE-bus or can I use theVictron miniBMS? To be honest I am also finding it difficult to work out how it would be wired into my circuit diagram.

2. The smart batteries have integrated cell balancing, temperature and voltage control (BTV). Is it advised to have a Victron BMV Battery Monitor or does the smart battery do this?

3. Do I need a Victron Battery Protect or does the smart battery do this?

4. Is there anything else I need or should have to make the lithium battery work and keep it protected?

I really want to go for lithium over AGM etc but I am finding it tricky! Any help would really be appreciated :)

Lithium Battery
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1 Answer
nebulight avatar image
nebulight answered ·

Hey. To answer your questions:

1. Yes, you need a BMS. The internal components of the smart battery will balance and take voltage/temp readings. To disconnect your chargers and loads, you will need one of the BMS units that Victron sells.

2. Yes, it's advised to have a BMV to monitor your state of charge as the batteries themselves can no do that.

3. Yes, at minimum you should have a smart battery protect to disconnect your DC loads if cause your battery is too low (it will be controlled by the BMS).

4. With any Victron BMS, you have allow to charge and allow to discharge ports. Since you have multiple charge sources it will be difficult to control all of them without additional components. The Victron BMS units have the following functions on their ports and current limitations per BMS:

Load Disconnect output:

The Load output is normally high and becomes free floating in case of imminent cell under voltage voltage (default 2,8V/cell, adjustable on the battery between 2,6V and 2,8V per cell).

Pre-alarm:

The pre-alarm output is normally free floating and becomes high in case of imminent cell under voltage (default 3,1V/cell, adjustable on the battery between 2,85V and 3,15V per cell).

Charge disconnect output:

The Charger output is normally high and becomes free floating in case of imminent cell over voltage or over temperature.

VE.BUS BMS:

Load Disconnect: Maximum current: 2A
Pre-alarm: Maximum current: 1A
Charge Disconnect: Maximum current: 10mA

miniBMS:

Load Disconnect: Maximum current: 1A
Pre-alarm: Maximum current: 1A
Charge Disconnect: Maximum current: 10mA

Smart BMS CL 12/100:

Load Disconnect: Maximum current: 10mA
Pre-alarm: Maximum current: 1A
Charge Disconnect: Maximum current: 10mA

I don't know much about the Votronic DC-DC and if it will charge your starting battery when the house battery is full, but if it does NOT, you could use another battery protect installed in reverse to control the charge current from both the dc-dc and mppt. However without knowing which inverter you're going with, the discharge side could. If you go with a Phoenix since you stated you don't need shore charging, then you can hookup up the remote port to the discharge BP I suggested above. So when the BP is turned off by the BMS, the signal wire will also turn off the Phoenix. Check out the smart battery protect manual for example.

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