Switch to Lithium?

Chris90!

Member
Sep 7, 2022
31
Boat Info
265 Sundancer 2022
Engines
6.2 350 ECT
Hi All,

I have a 2022 265 Sundancer (an EU model, I think it’s the 270 in the States?)with a 350 6.2. The boat has 2 house batteries in parallel plus the engine start. For those that know, the engine bay isn’t the biggest and the 2nd house battery is located just aft of the fresh water pump on the post side. This takes up space on the shelf and makes it difficult to get into the port side of the engine bay. I don’t have A/C, but do have electric stove/microwave etc. the house batteries are around 105amp wet cell and poor quality from new‍♂️
So, my question is, has anybody upgraded to Lithium from wet cell for the house bank?
I am considering a 230amp drop in Life4Po to replace the 2 wet cell batts, that frees up space and gives me some useful electrical capacity when away from the dock.
I have made the assumption that the alternator is okay at 70amp and around 14.4/6 charging.
any advice please?
 
Not an expert - but here's what I've learned along the way --

While they might just drop-in, I would familiarize myself with Charging, State of Charge, and Temperature at a minimum.

Charging:
How is your alternator tied into your start battery, and the the house batteries? You need to make sure the alternator always has the 'start' battery connected to it, so if the LFP (LiFePo4) batteries drop out (due to BMS), the alternator still has something connected to it.

LFP will generally accept as much current (amps) as your alternator will put out. This leads to most alternators overheating (and burning up). Typically you get an external alternator regulator that has a temperature probe (attached to the alternator). The regulator will lower the output as needed to keep the alternator from overheating. I'm assuming your engine should have sufficient power to spin the loaded up alternator -- and still have enough HP in reserve to move the boat adequately. Theory being - if your out at anchor for 2+ days, and you've drawn the LFP's down -- when you start the engine, the alternator will be working at 100% for some time, consuming engine HP. Some of the external regulators have a switch as well, allowing you to shut off the alternator -- alleviating the demand from the engine, allowing you to use all the available engine power for propulsion. I would also see if there is a delay timer - so you're not trying to pull max amps from the alternator on an engine that's just started and trying to warm up. Then there is the question above -- how is the alternator connected to both banks? If its a via a passive isolator - make sure its a good one, rated for full (or even 150%) of your alternator capacity. That isolator is going to get very warm. An ACR could be another option.

Validate that you onboard battery charger supports LiFePo4. Even so - since you will have two battery banks -- most chargers don't support each bank being a different chemistry. May have to buy another charger for piece of mind - or perhaps the start battery is only charged via the alternator? A DC-DC charger is an option.

State of Charge:
Does the drop in have any type of display, or Bluetooth connection? I would think you would want to know what your SOC is at at any given point. Aside from not drawing down too much (~50%), I think there are concerns with keeping them at 100% (or recharging them back to) - impacts life cycles.

Temperature:
Do some research on what the acceptable temperature ranges are for the drop in. Cold temperatures lead to more problems (concerns) charging/discharging. Some LFP's have integrated heaters. Higher temps could impact lifespan, while too high of a temperature, the BMS may disconnect them. Not sure your locale, or the temps in your engine room, and their exact placement with regards to engines/exhaust manifolds.

Storage:
SOC and Temperature come into play again here -- both short term and long term storage.

Some reading to start:
 
It’s a little more complicated than just dropping in a different battery. Charging the house LiFePO4 battery becomes an issue as mixing these batteries type causes all sorts of issues, including you may burn up your stock alternator. Easiest way to do it is to add a DC DC charger to the mix, but you’ll probably want to add an AC DC charger as well to make sure those expensive lithiums are well cared for.

 
Not an expert - but here's what I've learned along the way --

While they might just drop-in, I would familiarize myself with Charging, State of Charge, and Temperature at a minimum.

Charging:
How is your alternator tied into your start battery, and the the house batteries? You need to make sure the alternator always has the 'start' battery connected to it, so if the LFP (LiFePo4) batteries drop out (due to BMS), the alternator still has something connected to it.

LFP will generally accept as much current (amps) as your alternator will put out. This leads to most alternators overheating (and burning up). Typically you get an external alternator regulator that has a temperature probe (attached to the alternator). The regulator will lower the output as needed to keep the alternator from overheating. I'm assuming your engine should have sufficient power to spin the loaded up alternator -- and still have enough HP in reserve to move the boat adequately. Theory being - if your out at anchor for 2+ days, and you've drawn the LFP's down -- when you start the engine, the alternator will be working at 100% for some time, consuming engine HP. Some of the external regulators have a switch as well, allowing you to shut off the alternator -- alleviating the demand from the engine, allowing you to use all the available engine power for propulsion. I would also see if there is a delay timer - so you're not trying to pull max amps from the alternator on an engine that's just started and trying to warm up. Then there is the question above -- how is the alternator connected to both banks? If its a via a passive isolator - make sure its a good one, rated for full (or even 150%) of your alternator capacity. That isolator is going to get very warm. An ACR could be another option.

Validate that you onboard battery charger supports LiFePo4. Even so - since you will have two battery banks -- most chargers don't support each bank being a different chemistry. May have to buy another charger for piece of mind - or perhaps the start battery is only charged via the alternator? A DC-DC charger is an option.

State of Charge:
Does the drop in have any type of display, or Bluetooth connection? I would think you would want to know what your SOC is at at any given point. Aside from not drawing down too much (~50%), I think there are concerns with keeping them at 100% (or recharging them back to) - impacts life cycles.

Temperature:
Do some research on what the acceptable temperature ranges are for the drop in. Cold temperatures lead to more problems (concerns) charging/discharging. Some LFP's have integrated heaters. Higher temps could impact lifespan, while too high of a temperature, the BMS may disconnect them. Not sure your locale, or the temps in your engine room, and their exact placement with regards to engines/exhaust manifolds.

Storage:
SOC and Temperature come into play again here -- both short term and long term storage.

Some reading to start:
Thank you for a comprehensive reply, I really appreciate you sharing your knowledge. I’ll let you know how I can get on
 
It’s a little more complicated than just dropping in a different battery. Charging the house LiFePO4 battery becomes an issue as mixing these batteries type causes all sorts of issues, including you may burn up your stock alternator. Easiest way to do it is to add a DC DC charger to the mix, but you’ll probably want to add an AC DC charger as well to make sure those expensive lithiums are well cared for.

Thank you, I’ll let you know how I can get on
 

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