I've always wondered whether Firefly batteries really do charge faster than conventional lead-acid batteries, as the Firefly people tell us. There is oodles of information on the discharge characteristics in the Firefly blurb, but nothing much regarding this high-speed charging phenomenon. Well, now I know.
But let's first look at Lithium batteries because nothing can currently compare to their spectacular charging capabilities in their many forms.
These types of battery have the ability to suck in practically whatever amps the charging source can deliver, all the way through from start to finish, and such is their thirst that we really don't yet have charging sources powerful enough to satisfy their craving. Lithium batteries have an addiction: they're hooked on amps and all they want is more!
Those familiar with the now-standard 3-step Lead Acid charging routine of Bulk, Acceptance, and then Float stages will appreciate that, because Lithium batteries do not have to suffer through the painfully long, drawn-out Acceptance stage, they will recharge in a fraction of the time of Lead Acid equivalents.
Because of this, charging sources for Lithium batteries, especially alternators, need to be specially adapted and/or controlled in anticipation of them being forced to deliver their maximum amps output for the entire length of time of the charge. Ignoring this little nugget may well end in a debilitating melt-down, and I mean that quite literally!
Apart from the zippy charging, lithium battery systems will also last several thousands of cycles longer than conventional Lead Acid batteries, do not have to be fully recharged each cycle, can be discharged to deep levels, and are about half the weight. But they are also expensive, complicated, can't be charged when temperatures are at/below freezing, and for some they carry a scarily high fear-factor.
But wait a minute .... the Firefly is not a conventional Lead Acid battery, so let's compare its attributes to Lithium.
Thanks to the unique carbon-foam plate structure and other innovations, the Firefly Lead Acid AGM battery:
Will last several thousands of cycles longer than conventional Lead Acid batteries, and close to Lithium's lifespan.
- Just like Lithium, does not have to be fully recharged each cycle thanks to Partial State Of Charge (PSOC) technology that prevents sulfation.
- Can be safely discharged to 70%-90% Depth Of Discharge without loss of performance, same as with Lithium.
- Can be charged at up to 250 amps in temperatures down to as low as -4°F. Eat that Lithium!
- Charges faster than conventional Lead Acid batteries ... or so we are told .....
So to prove point "4", I tested the recharge time of a Firefly against a new, high-quality, marine AGM battery with about 10% less amp-hour capacity. Both batteries were discharged down to 12.4 volts and then recharged with a 50 amp power supply at their recommended Acceptance charge voltages: 14.4v for the Firefly, 14,7v for Brand X.
What is immediately evident is that the Firefly spent about 70% more time ingesting the maximum available 50 amps in the Bulk stage than Brand X, far longer than the size disparity of the batteries might suggest. And then, in the Acceptance stage, the Firefly's current intake dropped at a faster rate overall than Brand X, dropping to the full-charge criteria of 1.5 amps in just over three hours of total charge time.
In contrast, the smaller Brand X AGM was dithering at around 2.3 amps after five hours, at which point I gave up and headed home to a lukewarm dinner and scowling wife.
Although the test was intended to be merely a preliminary, fact-finding exercise, the results have more than satisfied my skeptical curiosity. The graph shows just how differently and how much faster the Firefly charged than the Brand X battery, and although it would be nice to test a Firefly against an identically sized Brand X, I don't think it would reveal anything radically different to what these results tell us.
So there you have it. The Firefly showed to have charged at a faster rate than a smaller capacity AGM battery. That, coupled with the fact that there is no need for it to be fully recharged each cycle, makes the Firefly Oasis Gp31 the closest thing to Lithium in charging performance, and has established itself as the gold standard of Lead Acid AGM batteries.