C-288 house battery replacement

[Nwdiver]

Well, I was kinda hoping to put this off for a year or two, but a combination of power outages, inverter settings, weather and stupidity on my part seems to have destroyed the two house bank batteries.

Now the fun part, figuring out what to replace them with. As I see it I have three choices.

1). Replace the house battery bank with firefly batteries

2). Replace the house bank with Victron batteries that have depth of discharge capability

3). Upgrade to lithium

And yes, I’m aware of the poor record for reliability of the firefly batteries, but, assuming they are still functioning after being stored in my garage for 2 years, I already have two of those. I will probably try that first.

If option 1 fails, I will probably go with option 2, primarily due to cost.


I like the lithium option, but I can’t justify the cost at the moment

 

[Cutwater28GG]

I dont think Fireflys are worth the money.

its really two choices. stay with AGM's or go for a full lithium upgrade (but you are upgrading a lot more than the batteries doing this. )

personally I keep replacing mine with the universal AGM's the factory installed. I get them from home depot or Amazon as they have free shipping. they last 3-4 years.

its hard to justify a retrofit to lithium for us as we are not large power users and the AGM's with a 340W solar panel keep up just fine for our use.

 

[Submariner]

Well, I was kinda hoping to put this off for a year or two, but a combination of power outages, inverter settings, weather and stupidity on my part seems to have destroyed the two house bank batteries.

Now the fun part, figuring out what to replace them with. As I see it I have three choices.

1). Replace the house battery bank with firefly batteries

2). Replace the house bank with Victron batteries that have depth of discharge capability

3). Upgrade to lithium

And yes, I’m aware of the poor record for reliability of the firefly batteries, but, assuming they are still functioning after being stored in my garage for 2 years, I already have two of those. I will probably try that first.

If option 1 fails, I will probably go with option 2, primarily due to cost.

I like the lithium option, but I can’t justify the cost at the moment

I'd recommend option 2. Victron Supercycle AGM batteries.

 

[Nwdiver]

Martin, i know you have some experience with the firefly batteries. How did yours fail?

 

[JunieBird]

NWdiver- please share how you fried the house batteries already.. concerned and don't want to be headed down the same road (unknowingly). Thank you- R/

 

[Submariner]

Martin, i know you have some experience with the firefly batteries. How did yours fail?

My firefly batteries failed, like a ton of others did, which ultimately resulted in the US Distributor for Firefly batteries to stop importing them into the US due to too many outstanding warranty claims. Quality control issues. They USED to be great batteries, and they could be if they would build them correctly. This is why you won't find many, if any, available, in stock, anywhere for purchase.

The specifics of "how did they fail"... I had 3 Firefly batteries in parallel. I started out by "fully charging them" using a 70 amp battery charger. Then I disconnected them from each other and ran just 1 at a time through the boat's battery monitor. I turned on enough stuff to get to 5 amps and then I waited. Each battery gave me 13-15 amp-hours before voltage went from 12 to 10.5. (dropped off quick). It took me all day to perform this test. But this was how I knew they were toast. (I should have gotten at least 70 amp-hours out of each).

The closest alternative to Firefly would be Victron Super Cycle batteries. If I still had AGM, I'd of switched to the Super Cycles.

P.S. I'm now at 2 years (From March of 2022) without any battery problems since my LFP conversion. 🙂

 

[Nwdiver]

NWdiver- please share how you fried the house batteries already.. concerned and don't want to be headed down the same road (unknowingly). Thank you- R/

Combination of stupidity and bad luck.

First thing that got me was the inverter on the boat is default setting is for UPS mode, so if you loose shore power, the inverter will automatically switch to battery. That can drain the battery pretty quick, exceptionally fast if you have an electrical cabin heater running. The inverter will stop before completely draining the battery, but I tend to leave the fridge on.

That happened several times, once because I didn’t turn on the shore breaker, and weather took out the power a few times as well

I forgot to turn on the charger once and that doesn’t help keeping up the batteries

It doesn’t help that the NW edition boats don’t come with a battery monitor, so it’s difficult to detect if you are doing something bad to the batteries

I have since put in a battery monitor

Surprisingly, the firefly batteries tested out well. They took a fast charge, held it up for several days then passed a load test. Will see how long they hold up. I have one advantage over Martin’s boat, with two engines, I can easily do a 100 amp charging just by going fishing