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aquabelle avatar image
aquabelle asked

Why use both Blue Smart and Orion chargers together?

On many of the Victron Schematics, both AC-DC Blue Smart chargers and Orion DC-DC chargers are shown (for just one example, see the schematic https://www.victronenergy.com/upload/documents/Narrow-Boat-MultiPlus-3KW_12V_230V-Lynx-Smart-BMS&Distributors-Alternator-WS500-MPPT-SBP-Orion-Tr-Cerbo-GX-touch-50-Bow-thruster-Galvanic-isolator.pdf).

Could someone explain why both chargers are required please? Why not just leave the job of charging, say, the Start bank to the Orion, letting it sit between the Lithium House bank and the Start battery? When underway, the House bank is getting charged from alternators and/or solar so the Orion would charge the Start bank....and on shorepower, the Lithium House bank is being charged by the Multiplus and so the Orion would be active and charging the Start bank. I just don't see the need for redundancy and the Blue Smart charger would suffer the AC-DC conversion losses.

What am I missing?

thanks in advance for clarification

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2 Answers
snoobler avatar image
snoobler answered ·

Lead acid batteries need to be floated at full charge for longevity. Personally, I would want to have a second option to ensure my critical batteries are fully charged.

Labeled as "maintenance charger" on that diagram. Likely for maintaining both batteries while in storage on AC power while allowing all other systems to be off.

Efficiency: The MP will burn 20W just in idle + whatever it takes to keep the batteries floated. Charger is less efficient than inverter, so losses there + DC-DC charger losses. So, choice is between:

  1. Burn 0.48kWh/day just to have the MP turned on + juice to keep batteries + two additional inefficiencies.
  2. Or just a few watts to keep the batteries floated with dedicated AC chargers.

Entire power system can be shut down with no concern for LFP draining during storage. Must provide provisions for maintaining float on LA.

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aquabelle avatar image aquabelle commented ·
Thanks...but..... Yes, FLA Start batts are best recharged quickly and then kept at Float. When disconnected from shorepower and anchored out, the Orion will charge and maintain directly from the LFP House bank AND from the solar panels/MPPT shown on the example schematic, with minimal losses. The Blue Smart charger will be powered by the inverter for its AC input with inverter losses, then another loss with the AC-DC conversion. And I don't think either device is really 'smart' in the sense of knowing there's another charge source at work, so the two chargers are likely to 'fight' each other anyway. Then back at the marina on shorepower, except in Winter when full shutdown of the LFP bank might occur, it would be more usual to have a refrigerator, maybe a modem and security circuits powered, etc which would occur via MP pass-thru. And again, there are solar panels so there's a source of power for the Orion even if the LFP batts are shut down.


I think the Victron guys who did these schematics (and many show both the Orion and the Blue Smart chargers targetting Start banks) must have something else in mind.

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snoobler avatar image snoobler aquabelle commented ·
Chargers don't "fight each other" on batteries. They simply respond to the measured voltage and react accordingly.


As I said, I'm confident they exist solely for the purpose of maintaining the LA batteries while being able to have the reset of the system completely shut down. Those two batteries are arguably the most critical in the system and ensuring they are properly maintained and available when needed seems a reasonable approach rather than relying solely on multiple layers of equipment.

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kevgermany avatar image
kevgermany answered ·
You don't want to charge a starter battery from an Orion. The alternator will have a much higher output. The idea with starter batteries is to charge as fast as possible, so they don't run down from frequent heavy loads/starts. Probably not an issue on a narrowboat, but carried over from cars with lower output alternators/generators in the past. Think short journeys with lights on in winter.


The Orion here looks as if it will be configured to charge when the engine is running. So not provide any maintenance charge during winter layup. Hence the mains/shore power chargers.

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aquabelle avatar image aquabelle commented ·

kevgermany: The schematic example I cited (and several others) DO show an alternator dedicated to Starter battery charging, so now we have four (4) chargers for the Start bank: alternator, solar, House batt-Orion-Start batt, and Blue Smart AC-DC.. Seems massively overkill to me.

And what makes you think the Orion is configured to charge when engine is running when the schematic shows a dedicated engine alternator for that??

At least for me, the mystery remains!

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