I think the original Firefly operational notes thread is now too long for any new info to get read so:
It seems the recovery procedure with it's 0.4C charging
rate is causing a lot of confusion. So I started a series of emails to Ocean Planet Energy who is the US Distributor and who I believe wrote the "manual" with that charge rate.
The manual says to use a 0.4C charge rate. It seems my charge acceptance drops to only about 15 amps/G31 at a state of charge of about 85%, is this normal?
"a charge current
tapering to 15-20A per battery
could happen as early as 85% SOC so your observations show that it might be tapering a bit early but not dramatically so"
I doubt most cruisers/ boats can do the 0.4C amp recovery charge for a house bank of G31s, and off grid cruisers have no practical way of taking batteries
out of the bank to do as individual batteries
. So what is the other method hinted at in the instructions? Is the high rate charge even needed since the batteries only accept that at low soc anyway? Or is the real factor the finish amps of 0.5/G31 at 14.4V absorption the key item, like other batteries?
"Unfortunately, the answers are not always totally black and white. We do encourage folks to upgrade at least one of their charge sources if they are getting FF so that a minimum of 0.2C charge current
can be achieved. Much of our business is providing upgraded charging
systems (upgraded alternators, etc) to satisfy clients demanding faster charging and reduced fuel
use. Anyhow, the original Firefly inventor has told us that fast charging does improve the electrochemical processes inside the battery
. However if after a deep discharge the finish amps as you mention are achieved, then perhaps as low of .2C for the bulk charging phase would suffice. Hard to say, as it isn't an exact science, unfortunately. What we DO know is that with fast charging of around .4C, the Firefly can retain/recover their capacity after many PSOC cycles, even without reaching the low finish amps (.5A tail current). In both our own and in 3rd party PSOC testing of discharging to 11.7V then charging for only 1hr starting at .4C, that after 30 such PSOC cycles the Firefly could be restored to full capacity by a couple full charge/discharge cycles. Whereas other AGM's suffered permanent capacity loss that could not be recovered.
A lot of confusion exists in the boating
cruising over this “recovery” procedure of the 0.4C. I feel this is a recovery procedure for trying to get back lost
capacity if needed and not an everyday needed thing. I feel that for us charging primary with solar
that acceptance amps at the 14.4v absorption is more important. Others really stress and feel it means to try to charge at this rate all the time (which of course means starting from low state of charge all the time) - so which is correct?
"We do know that the fast charging is beneficial, as it has proven effective when not quite getting to a full charge for extended periods (as in PSOC cycling).
It is certainly not required to charge at the .4C rate all the time.
It also isn't necessarily strictly applicable to the recovery procedure.
And yes, if you're not doing deep discharge cycles, then fast charging may indeed be less important than getting to the low acceptance amps,
And anyhow, at a low DOD there may not be much time spent @ .4C before hitting 14.4V.
However, what we don't know is what the possible detrimental long-term effects may be from:
1) Never doing periodic deep discharge/recharge cycles, or
2) Only charging at low rates after deep discharges.
There are many scenarios that testing could be devised for. All would take time and planning to get relevant results.
In any case, we recommended to occasional deep discharging/recharging, not only for conditioning, but also for capacity testing.
This would help track the effects of whatever use pattern the batteries are doing, and a baseline to compare with if subsequent recovery cycles are done."
If you read between the lines, because it is hard to get a straight answer:
1 - The 0.4C is a "recovery" charge not an everyday time.
2 - A "regular" charge rate of 0.2C is recommended
3 - Even the 0.2C can not be expected above 85% state of charge
4 - The finish amps of 0.5A at 14.4V is recommended to get to occasionally (note that it used to say 1.5A)
For me, I consider my FireFly batteries to basically be AGMs with added features of the carbon fiber grid that gets around the PSOC problems. But all the other normal charge rules I have learned still apply and it is better to have shallower discharges and to get fully charged based on absorption acceptance amps. If you do appear to have lost
capacity you discharge them down and do the recovery procedure a few times to get it back (for me on the boat
this would require taking batteries out of the bank to do).
I truly do not feel anyone knows and there has not really been testing that matches boat
cruiser usage. Just like every other battery you need to read between the lines an apply the "manual" in a practical way.