Re: Lithium Batteries under Consideration

michael winand

Hi Scott,  in the early days of producing them there were a few issues, these could have been from those. 
I am running a set of 8 g31 in the super maramu. Just coming up to 2 years. Would say around 300 cycles down to 60 to 70 percent. We use around 150amps overnight  
1 freezer. 2 fridge's. 
Recent additions of  1kw of solar see them topped off around 3pm.
Main battery charger is a 120amp quattro.
Alternator is a 150 amp electrodyne  going through a balmar 624.
I have the victron battery balancers. 

They charge fast  i have seen the Alternator put 165amps into the bank. 
You will need to program the charger and Alternator regulator to suit. 
Very low discharge,  left disconnected for 4 months, put the small 15 amp charger on each battery to top off and 15min was all required. 

Like any battery system. It needs to be set-up, monitored, understood. 
Any type can be damaged. 
Lithium  needs low voltage disconnect. 
So far they are going well, probably know if they are living up to their claims in another year of full time cruising. 
Food for thought 
Michael Nebo sm251 

On Tue, 24 Nov 2020 at 2:58 pm, Scott SV Tengah
<Scott.nguyen@...> wrote:

I am not sure if they are worse. Given that Jamie was getting below 24 volts overnight after only a year, that sounds pretty bad though. Even our old gel batteries weren't that bad.

My concern with Firefly was that the sales pitch was that you could run them down to low SOC without damaging the battery, but if the voltage sags so much, the batteries may not get damaged, but your boat will not like the low voltage. Therefore the ability to take it to low SOC is only academic.

On Mon, Nov 23, 2020 at 10:48 AM michael winand via <> wrote:
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

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

2007 A54 #69
SV Tengah

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