Lithium battery case corrosion?

[Vespucci]

I’m planning to replace my house batteries with a DIY LiFePO4 setup.  The most popular and cost effective cells all seem to be based on an Aluminum cell case that is wrapped with a thin plastic film.  This looks a bit worrisome for marine application, in particular I’m concerned the cases might be susceptible to corrosion. I’m looking for any anecdotal comments about how well these metal cased battery cells hold up on boats. I note that the plastic encased cells, such as those made by CALB tend to have lower capacity and are significantly more expensive - but are they a better option in the long run?

‘thanks in advance for comments.

 

[SimonGH]

I just put mine aboard a couple of days ago.

it's an interesting question, I honestly hadn't considered it.

The plastic film isn't doing much, perhaps it would be better to remove it and paint it with zinc chromate primer or even epoxy enamel.

The cost differential is significant...  my 280Ah cells were $120 each (including shipping from china).

The other thing to consider is that if you watch the videos where they cut open a commercial battery (like battleborn), they are full of the cylindrical cells with bare aluminum cases and that blue film.  Not saying it's right, but perhaps a good surface treatment is sufficient.

 

[Vespucci]

I just put mine aboard a couple of days ago.

it's an interesting question, I honestly hadn't considered it.

The plastic film isn't doing much, perhaps it would be better to remove it and paint it with zinc chromate primer or even epoxy enamel.

The cost differential is significant...  my 280Ah cells were $120 each (including shipping from china).

The other thing to consider is that if you watch the videos where they cut open a commercial battery (like battleborn), they are full of the cylindrical cells with bare aluminum cases and that blue film.  Not saying it's right, but perhaps a good surface treatment is sufficient.

I was wondering about using some sort of tough vinyl wrap, like a chip guard protector on top of the original plastic.  What do you think?

also, very interested to compare notes on your install. If you’re keen on this send me a pm - I’d love to learn what components and chargers etc. You are planning.

 

[SimonGH]

I sent you a PM, but i figured i'd post what i'm doing here incase folks have good suggestions:

* The background: I have a 2019 Beneteau 41.1

Current batteries are AGM group 31.  There are 4 house batteries and one starter battery.  Alternator feeds a Cristec MOSFET charge divider between the house and starter bank.  Theres also a 60 Amp shore charger that feeds each battery separately.  I have a Victron battery monitor and smart shunt.

There is also 2 batteries up front for the bow thruster, those are old school lead acid.

My plan is to shuffle things - i'm going to take 2 AGM batteries and move them up front for the bow thruster, recycle the lead acid batteries, and add two 280Ah LiFePo batteries to the house bank.

I'm also adding a Balmar MC-614 External regulator that talks to their Yanmar Smart-ready retrofit kit.

* The rationale for my design:

1. Keeping the AGM lead acid in the bank helps "buffer" the charge coming from the alternator, so I don't need some type of active connection between the BMS and the regulator to shut down the charging before the BMS shuts off for any reason.

2. Based on the loads of my boat and the current capacity, the LiFePo4 will effectively more than double my capacity in the same footprint.  The coolest part of the LiFePo4 chemistry is the usable capacity - i should get over 400 Ah usable for the two cells, where as i'm currently only getting about ~200Ah from the current ~400Ah AGM bank.  So the total should be ~500Ah between two AGM and two LiFePo.

3. The Yanmar alternator is 120A, but my understanding is that the current demands of the LiFePo can burn out the alternator because it can pull so much current quickly.  So hence the Balmar MC-614 & retrofit (if you don't have a yanmar you may need a upgraded alternator, or there are DC-DC charge controllers that can help)

* The DIY LiFePo4 batteries:

4S setup, using 3.2v nominal 280Ah cells (alibaba).  I'm building 2 discrete batteries of 4 cells each, each with their own BMS and balancer.

Overkill solar 120A BMS (1 each)

4S 5A active balancer (1 each)

I 3D printed a complicated set of covers and brackets to hold the cells together, mount the BMS and balancer in conjunction with some stainless threaded rods and nylon strapping.  It's the one area i'm surprised there isn't more available - there is one battery case that looks like it will fit, but it's very expensive and bigger than the group 31 space that I have.  So I made my own.

* Settings configuration:

1. From what i've researched, my existing Cristec charger will handle the mixed AGM/LiFePo chemistry automatically.

2. The Balmar has a LiFePo setting that needs to be configured/enabled

3. The overkill BMS are already setup for lithium, and can be monitored via bluetooth

I'm looking at building an arduino device that can trigger an alarm if the BMS gets close to a parameter that would shut the battery off, as ABYC requires that for full lithium banks.  However for these mixed banks, both lithium BMS could shut off and you'd still have power, so it's less of a safety issue and more of a loss of overall capacity issue.  So I think you need to know that, but it doesn't trigger an issue that would cause a safety problem (like your autopilot and navigation shuts down)

I think that covers everything! 

 

[Max Rockatansky]

Here. The guy running this is a liveaboard, have known him for awhile. I’m sure he’ll answer your questions

https://lithiummarinebattery.com

 

[MarginSil]

Thank for sharing how to deal in this situation

 

[MarginSil]

It is important to know what battery you need before trying to replace your old one. For example, I didn't know what battery I need for my car, so I bought a weaker one when I replaced it. I was having problems with the car's electric system, and these problems started when I put a battery that is too small. I read on cararac.com about what battery I need on my car, and I understood what could cause such problems. So I replaced the battery again on the right one, and all the issues with my electric system disappeared momentaneously.

 

[climenuts]

Nothing to do with case corrosion (sorry) but rather than start another thread I thought I'd ask here.

When the time comes I'm going to replace my 420Ah Flooded Lead Acid Bank (4xGC2) & G31 Start Battery with a 4x280Ah 3.2V Cell LiFePO4 bank and small AGM Start Battery. I've got a Balmar Alternator & MC-614 Charger Controller already. Shore power is a an older 20A job with an AGM setting but I think I'll replace it with something more sophisticated.

My big unknown is switching between shore power & alternator power with the batteries already fully charged. What programming strategies are people using to avoid over-charging when switching charging sources? Is the MC-614 and reasonably priced shore power controllers 'smart' enough not to dwell at absorption voltage when already charged? For my flooded house bank I find the MC-614 flips to float far too quickly so I have the minimum Bulk+Absorption time total set for 4h - I'm concerned I might need to keep a minimum time to avoid the same problem for lithium but I would actually be damaging the cells.

Are there any specific products that would let adjust absorption voltage for 75% SoC on shore power? My goal would be to have absorption voltage on shore and alternator power set to 75% SoC under normal circumstances and I would just reprogram if I had a big DoD planned for the couple extended trips I do every year.