Supplement 48V 1300 Ah lead acid system with LFP battery pack, what are my options?

Q&A and troubleshooting
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Hi! First post, sorry if this has come up before.

My canal boat in Amsterdam has a 48V traction battery pack ± 1300 Ah that is in reasonable condition for its age (never completely run down, timely demi water refills). I want to run about 3KW of electrical heating off the battery pack, in addition to propulsion, for about 5 hours, multiple times a week. While my 230V onboard AC power net will be able to manage this (barely), it will put a greater strain on the battery. The electric system is Victron based, with a Quattro 48V/10000, transformer, VRM etc.

I’m looking to supplement the battery capacity by installing an additional LFP battery, and I need help weighing the pros and cons of the following options:

Mobile power station battery with integrated AC power outlet
…and run a heater directly from it.
pros

  • no installation required
  • semi portable, can be used for other stuff outside of winter season

cons

  • expensive, as I’ll likely need two to get the required output wattage, and also 2 extension batteries
  • it’s a lot of gear that I can’t store out of sight
  • elevated risk of theft

install LFP battery with separate charger/inverter, just for heating
And run separate 230V AC lines to electric heaters.
pros

  • current electrical system remains as it is
  • somewhat cheaper than 2 power stations (haven’t done a price comparison yet)

cons

  • no communication or synergy between the two battery systems
  • not portable, so the system is stuck doing nothing for 3/4 of the year.
  • once the battery is empty, the heating fails, even if the main battery has plenty of power left.

Install LFP battery with some form of DC-DC charging to supply power to the lead acid battery pack
Main battery deals with the additional heat power load, but is fed additional current from the LFP battery. Victron Quattro will charge the LFP battery, which will in turn charge the lead-acid main battery.
pros

  • seems like the most elegant solution (to my untrained eye)
  • I think I should be able to charge both batteries with the
  • outside of heating season, LFP battery works as a range extender
  • hopefully life extension for the main battery??? (I don’t know if this is the case)

cons

  • I don’t know if this will work
  • Victron doesn’t seem to offer a product that can integrate the two systems and regulate the voltage difference.

I’ve been advised against it by an electrical engineer who said it’s a bad idea, but couldn’t articulate why (other than: “I don’t like it. Nobody else is doing it”)

Any insight is greatly appreciated.
context: the boat is a professional indoor aluminium Amsterdam canal boat for ± 25 people. This winter we’re expecting a busy boating season during Amsterdam Light Festival, and heating is becoming an issue: using fuel-based heaters is not an option due to ES-TRIN regulations (It’s a passenger vessel. Also, city center will become a zero emission zone). I’d like to keep the lead acid battery as I actually need the weight of it to avoid paying money for ballast.

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As the working parameters of the traction and lfp differ too much, this would be my option.

And you can always crosscharge over AC.

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Hi Paul, I’ve build something similar for an Amsterdam canal boat collegue of yours. Just registered (long overdue anyway) to share some of our considerations and solutions but would need more specifics of your operation for that. Your harbouring and shore power situation for instance. Also welcome to contact me. Jan

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And what kind of propulsion system are you running. I’ve seen quite a few asynchronous motor with sevcon controller that require significant (air) cooling, you might want to see if you can harvest that heat first.

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It can be done, essentially you need a BMS/ voltage sensitivity relay to disconnect the Li from the parallel LA when full and empty.

This is a great place to start

also look at diysolar forums.

If it’s for cabin heating a diesel air heater would be better. (EDIT: Nevermind just read your post again)

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Propulsion is a Bellmarine 10KW with a closed loop liquid cooling system. Boat is docked at e-Harbour, where I have one phase 230V shore power that delivers ± 6KW, I’m guessing with a 25A fuse.

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Thanks man, I’m going to look into it :slight_smile:

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Hi Jan,

Thanks! I’ll send you a message.

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I bet that’s just a standard 16A but that aside, I’d be 1st tempted to tap into that cooling system with a small heat exchanger (water-airco die ook verwarmen kan) to triple the effective heat-per-kWh. And 2nd try to get a 3-fase upgrade from e-harbour that would allow to add a small but relatively fast chargeable (0.5C, 2hours) li-ion backup battery to power that heat exchanger.
Are you taking ‘breaks’ at the the harbour during the day?

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One hour single phase 230Vac 16A could provide about 3,5kWh charge, 3-phase 25A about 16kWh charge. So depending on your shore power situation and your operational profile (breaks in harbour or not), you might not need a large lithium battery as long as you can keep topping it up.
PS, I’ve been looking for a direct message option but I suspect it will take some ‘activity’ vetting on this forum to get access to that :wink: you can app me on nul zes vijf nul vier vijf nul zeven drie een.

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I always wondered what use case would fit a lithium hybrid system best, or is only an option in a practical upgrade situation with the lead-acid capacity simply already present? Either way it’s probably a ‘no-go’ solution in light of the Amsterdam regulatory situation for commercial passenger boating.

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For the price of lithium these days, I would see it as an upgrade path only to extend the life of an aging LA bank.

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Agree with that. But as I edited to my previous answer, @elektrischeschipper needs to take city counsel regulations into account as well that most likely will prohibit any and all too clever solutions. Otherwise I’d simply advise to install a good diesel heater.

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thanks! Will do :wink: