Starter battery to go with firefly house bank?

[sailingunity]

Originally Posted by john61ct

Yes that sort of setup can be very efficient, eliminate carrying lots of "dead lead" inherent in dedicating Starters to nothing but cranking.

Switching from 12V to 24V - Page 7 - Cruisers & Sailing Forums

For belt & suspenders, could have one of those small "personal power" jumper packs kept charged up for emergencies as well.

In theory I could accomplish this with an ACR simply by setting the connect voltage setting to something like 12.5 right? I'm assuming I would still want the reserve battery to be something else besides a firefly battery, given the low CCA.

[john61ct]

Yes ideal is tweakable setpoint as things change over time.

But no, it is all one House+ bank as long as SoC is high.

The Starter subunit ideally only gets isolated occasionally, when forced to allow SoC on the rest of the bank to drop.

The Starting function really is trivial compared to the deep cycling duties.

All should be same model size age etc.

A compromise doesn't kill the idea, but it **is** a compromise.

[sailingunity]

Are you implying the CCA is OK and that I could use one of the firefly batteries as an isolated start battery?

In that case, I could save some money and just put one of the 5 batteries I just bought on the ACR.

[john61ct]

If it turns out that 1/5 can't easily crank (which I doubt) then use 2/5 as your "Starter subset".

Just eliminating the Starter without adding its equivalent capacity to House now makes the Starting functionality a burden without any corresponding benefit.

The whole point of this unconventional design is to **greatly increase** the total size of House, and in normal conditions, use the same (whole) bank for Starting.

It should be **very rare** that dropping SoC results in only the "Starter subset" doing the cranking. That is accomplished as a result of the whole House bank being much bigger than it would be under an old-school separate dedicated Starter battery design.

Also the user-custom-adjustable high-current capacity LVC is critical to the idea; I haven't identified which device I would use yet. What were you planning on using?

Most standard VSRs are not voltage adjustable.

[sailingunity]

Our ACR has high and low cutoff points. I suppose my idea was to just wire it up so the ACR isolates one of the batteries, and in the event that we tried to start it and it wouldn't, switch to the reserve battery manually. I'm not dying to gain back the space or weight, really, but saving $400 sounds pretty nice.

[ranger58sb]

Originally Posted by sailingunity

Are you implying the CCA is OK and that I could use one of the firefly batteries as an isolated start battery?

In that case, I could save some money and just put one of the 5 batteries I just bought on the ACR.

Dunno about Firefly specs or your engine requirements, but you can look it up to compare.

For example, a single Odyssey PC-2150 gives 1150 CCA/1370 MCA... whereas our (450-hp) diesels want a minimum of 1250 CCA/1560 MCA. (IOW, we need a bank of 2x for starting.)

You can compare Firefly numbers to your engine numbers... and then take your windlass requirements into account... to decide.

-Chris

[Wotname]

Originally Posted by ranger42c

Dunno about Firefly specs or your engine requirements, but you can look it up to compare.

For example, a single Odyssey PC-2150 gives 1150 CCA/1370 MCA... whereas our (450-hp) diesels want a minimum of 1250 CCA/1560 MCA. (IOW, we need a bank of 2x for starting.)

You can compare Firefly numbers to your engine numbers... and then take your windlass requirements into account... to decide.

-Chris

However if your engines start easily (like in a few seconds), then a single PC-2150 gives you 2150 amps (for 5 seconds at 77F). Not suggesting you do this but it is good to know.

[ranger58sb]

Originally Posted by Wotname

However if your engines start easily (like in a few seconds), then a single PC-2150 gives you 2150 amps (for 5 seconds at 77F). Not suggesting you do this but it is good to know.

Correct. I just figured Firefly may not have (or publish) an equivalent spec, so thought to stick to basics to describe comparison for OP. Good point, though.

-Chris

[sailingunity]

You're right all FF specs is the CCA, which is 600. That is low, but I'm sure it is higher in the type of temperatures we'd be experiencing. I have an inquiry with FF.

[s/v Jedi]

Originally Posted by sailingunity

You're right all FF specs is the CCA, which is 600. That is low, but I'm sure it is higher in the type of temperatures we'd be experiencing. I have an inquiry with FF.

Just get the Odyssey and be done with it. It’s the best option and with FF batteries for house bank, the price isn’t bad either. Why would you try options that are inferior and not even save money?

[ranger58sb]

The only caveat I might mention is about if you're charging both with a single charger. Odyssey and Firefly charging recommendations might be different enough to warrant some thought...

If necessary in that case, a Lifeline G31 might be a possible alternative...

-Chris

[john61ct]

Firefly, Lifeline and Odyssey are all good at 14.4V Absorb, but Odyssey can go up to 14.7V

The ideal Float for Firefly is 13.2V, won't do other lines any harm. 13.5V is the nominal highest, but in reality too high for max longevity.

The ideal is no Float like LFP, but most find implementing that is impractical.

The transition from Absorb to Float should be benchmarked

when it is possible to get to Full

off the House Firefly, trailing amps falling to endAmps spec of 0.015C, 1.5A per 100Ah capacity.

[s/v Jedi]

I think that Firefly and Lifeline are competing for roles as house batteries, while Odyssey is the clear winner for starting and other high power applications. The reason is that it’s thin plate pure lead TPPL technology is precisely tuned to that role. The PC2150 with it’s high CCA rating and 5,000 Amp short circuit capability is the star at the top. It’s one of the few products that I still feel good about after paying for it

[john61ct]

Enersys (Odyssey) was the original developer / inventor of the technology under military contracts.

They and Northstar are all perfectly well suited for true deep-cycling usage.

Units like the PC-2150 are very deservedly popular where fast-discharge C-rate is required in short bursts from a bank of **smaller Ah capacity**.

That capability does **not** in any way mean they perform less well on the lower-rate deep cycling side, **genuine** dual-use unlike all the fraudulently labeled as such.

Any other deep-cycle bank can compensate to get the same power rates from a larger Ah capacity.

Firefly is unique in losing fewer life cycles going as deep as 80% DoD, and of course resisting capacity loss from PSOC abuse.

Without those issues, I think one of the other three deliver better value.

And for larger banks, going to lower than 12V units will be more robust.

[ranger58sb]

Originally Posted by s/v Jedi

I think that Firefly and Lifeline are competing for roles as house batteries, while Odyssey is the clear winner for starting and other high power applications. The reason is that it’s thin plate pure lead TPPL technology is precisely tuned to that role. The PC2150 with it’s high CCA rating and 5,000 Amp short circuit capability is the star at the top. It’s one of the few products that I still feel good about after paying for it

Yep, agree, and we've had great luck with our dual-purpose PC-2150 banks.

I did replace one of those 3x banks with a bank of 4x Lifeline 6V GPL-4CTs... coincident with installing an inverter (inverter/charger)... so I could increase total capacity from 300 Ah to 440 Ah... but this was also a circumstance where I could eke out space for the GC2s but didn't find a way to squeeze a fourth G31 into the same area. (And 440 > 400, anyway.)

The Lifelines have only been in service for a couple years now, so no long-term track record info yet...

-Chris