Re: Lithium Batteries under Consideration

michael winand

Hi Scott,  would you suggest that the firefly batteries are worse than other lead batteries regarding their voltage drop curve?
I would think that the state of change would have been important to know. 
Thanks  Michael  Nebo sm251 

On Tue, 24 Nov 2020 at 2:23 am, Scott from SV Tengah
<Scott.nguyen@...> wrote:

I think it would be best if Jamie could chime in. He replaced his Fireflies precisely because he experienced severe voltage drop under load, one of the "hidden" downsides of carbon foam. As always, there could have been other confounding factors. That said, I would be careful trusting specs. The Victron Battery Protect should have worked fine on my system but instead melted within a day. 

Regarding gen usage during BT, I spent about a year diagnosing and fixing my BT, so learned a bit more than I ever wanted to know. My understanding is an Amel54 owner experienced a solenoid that melted closed because ohm's law tells us that when voltage drops, amps have to increase to compensate. That owner spun like a top in the marina. That's why Amel suggested that I install an emergency stop switch.  My understanding is that repeated use (think 30 knots on the beam in a tricky marina) will result in cumulative voltage drops so the genset/charger is supposed to help the batteries recover a bit between uses, not replace the batteries.

I considered carbon foam as a cheaper, easier upgrade than lifepo4, but decided against them for the voltage drop issues. 
If you look at the firely SOC vs. voltage curves, you will see that the main benefit of being able to deeply discharge and also not fully recharge is negated by the fact that voltage drops to unacceptable levels at low SOC.

Here's another guy who took the baby step and then ended up going all the way. That said, I understand your use case is primarily marina life, so in your case, I would not get lithium either. Just wanted to make the info available to people who live full time off the grid who think Fireflies are lithium like:

Perhaps you will have better success with respect to voltage drops than others who have tried. 

2007 A54 #69
SV Tengah

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