Safety Check: Smart BMS 12-200 vs. Orion DC-to-DC for 180A Alternator

DIY
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1

Hello everyone,

I’m looking for a definitive answer to a system design question for my motorhome.

Vehicle & Components:

  • Vehicle: 2006 Mercedes Sprinter
  • Alternator: 180A
  • Planned Batteries: Victron LiFePO₄

I am having a debate with my installer about the correct and safe way to charge the new lithium batteries from the 180A alternator. We are considering two options:

  1. Installer’s Suggestion: Use a Smart BMS 12-200 alone. The argument is that this BMS can be fuse-limited to safely control the charge from the 180A alternator.
  2. My Understanding: Use a DC-to-DC charger (like an Orion XS 50A). My understanding is that the Smart BMS 12-200 is only rated for a maximum input of 100A from the alternator, making it unsuitable and unsafe with a 180A source.

Could the community please confirm which is the correct and safe Victron-recommended approach for an alternator of this size?

Thank you.

2

The SmartBMS lets you control the current coming from the alternator, but has no direct influence on charging voltage. If the alternator only supplies 13.8V for example, then thats what you are going to get to charge the Lifepo. If the alternator goes up to 14.8V for example, then all the BMS can do is current limit (i guess trough PWM) the alternator input to the point where the alternator input is switched off completely. It is rated at 100A alternator input current, but it is safe to use on a 180A alternator, since its not the source that defines how much current flows.

The Orion can control both current and voltage. It can limit the input current to protect the alternator and actively control the output current and voltage to match the Lifepo, mostly independent from each other.

I personally prefer the Orions because of this, but it does come at a cost. The SmartBMS is kind of a combination of a BMS, two main fuse holders and two BatteryProtects. When choosing an Orion, you still need a BMS, for example the smallBMS, and maybe a BatterProtect to switch off DC loads, and fuse holders. All as separate devices.

Im not sure if you could feed the output of an Orion XS into the alternator input of a smartBMS