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NickL · 05-04-2024, 09:32

My boat requires a single 100Ah AGM battery - mostly for basic stuff. Instruments, LED lights and Tiller pilot. 4 years ago I opted for a single Firefly Oasis G31 battery thinking that initial investment will allow for battery to last longer due to their advertised number of cycles and depth of discharge.

I used ProMariner ProNautic 40A charger programmed with a AGM chemistry profile.

The battery was working great for one or two seasons but then it suddenly failed. It basically lost about 80-90 % of its capacity. My average consumption was about 2-4Amps and battery would run down flat after only 3-4 hours.

Vendor accepted the exchange under warranty and I got another new battery.

It again worked for about two years and then it suddenly failed again with exact same symptoms. This was not a gradual loss of capacity. It just happened once .

I tried the restoration charge as per user manual but I was not able to revive it. Looks like it is toast.

Can anyone share their experience with this type of battery or should I cut my losses and go with something else?

**newhaul** · 05-04-2024, 11:42

Quote:

Originally Posted by NickL

My boat requires a single 100Ah AGM battery - mostly for basic stuff. Instruments, LED lights and Tiller pilot. 4 years ago I opted for a single Firefly Oasis G31 battery thinking that initial investment will allow for battery to last longer due to their advertised number of cycles and depth of discharge.

I used ProMariner ProNautic 40A charger programmed with a AGM chemistry profile.

The battery was working great for one or two seasons but then it suddenly failed. It basically lost about 80-90 % of its capacity. My average consumption was about 2-4Amps and battery would run down flat after only 3-4 hours.

Vendor accepted the exchange under warranty and I got another new battery.

It again worked for about two years and then it suddenly failed again with exact same symptoms. This was not a gradual loss of capacity. It just happened once .

I tried the restoration charge as per user manual but I was not able to revive it. Looks like it is toast.

Can anyone share their experience with this type of battery or should I cut my losses and go with something else?

Cut your losses and upgrade to lifepo4
https://www.amazon.com/gp/product/B0...XJLE7BDB9&th=1
Not cheapest but initially but after 15 years it will still be running strong .
Just set your charger to the LFP settings . And enjoy a cold drink and great sunsets

dannc · 05-04-2024, 11:50

A search on this website, and others, should show there have been problems with the Firefly batteries.

sailorboy1 · 05-04-2024, 12:48

Quote:

Originally Posted by NickL

Can anyone share their experience with this type of battery or should I cut my losses and go with something else?

My FF batteries lasted 2.5 years and suddenly went bad.

You don't have a choice other than to change to something else since FF closed up. You can be a lithium packaged battery off Amazon for 50-60% of what you paid for the FF.

NickL · 05-04-2024, 12:52

Quote:

Originally Posted by sailorboy1

My FF batteries lasted 2.5 years and suddenly went bad.

You don't have a choice other than to change to something else since FF closed up. You can be a lithium packaged battery off Amazon for 50-60% of what you paid for the FF.

Thank you.
I think I heard Firefly is not even responding to inquiries complaints.

With the prices for LifePo4 plummeting lately, this seems to be direction to go to. I sail Great Lakes and my Insurance is still 'studying' the matter about Lithium batteries. They are not yet sure how to handle the policies. That is the only problem which is kind of holding me back.

I was going to go with Victron smart Lithium and external BMS in an attempt to comply with ABYC E13 - but that is just another can of worms...

Thanks again to all

NickL · 05-04-2024, 12:57

Quote:

Originally Posted by sailorboy1

My FF batteries lasted 2.5 years and suddenly went bad.

You don't have a choice other than to change to something else since FF closed up. You can be a lithium packaged battery off Amazon for 50-60% of what you paid for the FF.

Thanks mate!

smac999 · 05-04-2024, 13:36

Firefly is basicly out of business because this happened to all their batteries made overseas in the past 4 years. The first ones made in the USA were good.

**Adelie** · 05-04-2024, 15:20

The problem might’ve been your charge rate. Fireflies are an AGM battery which requires a high rate charging if the battery has been discharged significantly i.e. approximately 50%.
High rate charging being a minimum of 0.2C, with with 0.3C being better and 0.4C being most preferred. 0.2C for a 100 amp-hour battery would be 20A.

**newhaul** · 05-04-2024, 15:30

Quote:

Originally Posted by Adelie

The problem might’ve been your charge rate. Fireflies are an AGM battery which requires a high rate charging if the battery has been discharged significantly i.e. approximately 50%.
High rate charging being a minimum of 0.2C, with with 0.3C being better and 0.4C being most preferred. 0.2C for a 100 amp-hour battery would be 20A.

That charge rate is one more reason to go lifepo4 it will easily handle up to 1C charge rate is 100amp charge for 100ah battery

**Adelie** · 05-04-2024, 15:33

My point was that the problem may stem from inadequate charge rate, i.e. continuous low rate (5-10A) solar.

**newhaul** · 05-04-2024, 15:46

Quote:

Originally Posted by Adelie

My point was that the problem may stem from inadequate charge rate, i.e. continuous low rate (5-10A) solar.

I am assuming bad faulty batteries as he said he's using a 40 amp charger set to specs for the firefly bank

NickL · 05-04-2024, 16:44

Quote:

Originally Posted by newhaul

I am assuming bad faulty batteries as he said he's using a 40 amp charger set to specs for the firefly bank

Correct.
No solar stuff here. Yes I was charging the battery from my 35Ah alternator occasionally to top off the battery when out racing overnight, but in vast majority of cases it was a 40Ah ProNautic charger from the shore power. It was producing 40A during the bulk phase charge.

sailorboy1 · 05-04-2024, 17:20

pointless to chase the same stuff, the bottomline is the FFs are toast and in the last few years I have heard of no one able to recover them (I tried)