Hi Rich, > The point Roger is the are NOT effected by lower temps. Just > temps above 130F. Up here this is all the reason we need to > change to them. The first TEMP degrade point is at -14 F.
The data sheets I've got state the operating range for these batteries is 14F (-10C) to 140F (60C). The curves also indicate that their capacity has a maximum at 25C and *falls* as they get either *hotter* or *cooler* than this (e.g. <80% of rated at -10C, ~85% at 0C, ~112% at 25C, and ~95% at 50C). In any event, the temperature issue I was referring to with respect potential impact on cycle life is temperature compensation during charge and protecting the batteries from exposure to excessive temperatures during charge/discharge, especially should someone take advantage of the snort your PFC50 puts in their impatient little hands. ;^> > That we get 3x the range and 3x the stored energy just > makes it even better. And No Puekert. The 3x the stored energy is a definite plus; no quibbling there! "No Peukert"? The data sheets I've got all show ~significantly~ more pronounced voltage sag than PbA (that increases with discharge rate and DOD), and a reduction in available capacity as discharge rate increases. Given that NiZn have a fixed end-of-discharge voltage (Evercel seems to use ~9.5V/12V monobloc: ~1.36Vpc in their plots although their manual states 7.35V/12V monobloc @ 2C: ~1.05Vpc), just as PbA does, these effects indicate that NiZn is subject to similar capacity reduction at higher rates of discharge as we attribute to Peukert effects with PbA. The Model 100 data sheet states its capacity as 90Ah @ C/20, 83Ah at C/1, and 83Ah at 3C, all at 21C temperature, however, the Evercel's own discharge plots show that when discharged to the same termination voltage of ~8.4V/12V monobloc at 21C, the battery delivers 91Ah at C/20, 83Ah at C/1, and 72Ah at 3C; the only way to get 83Ah out at 3C is to move the goal post by redefining the end-of-discharge voltage to a lower value than for the other tests... just what one would do to achieve the same result with PbA. The effect may certainly be less significant, or deserve a different name, but it does not appear to be absent. > Evercells won't make the MONDO amps that PbLA will, but > that just means higher pack volts and controllers that can > live with 4:1 input to output ratios. AKA 360v in at 300 amps > and 1200a out at 96v. The Zillas will do this, and quite well. Sure, if range is important enough to mandate a US$5k+ controller, and the cost of a 360V pack (I don't recall Evercel exactly giving these batteries away, and in fact, last I heard people were reporting that Evercel didn't seem particularly interested in selling to hobbiests anymore), and the charge management system for the long string, and all the other incremental system costs associated with the jump from ~150VDC to >300VDC, and if one is willing to accept that the power available from the pack will drop significantly more with DOD (due to NiZn voltage sag) than it would with PbA. For instance, the data sheets show a 360V nominal pack of Model 100 Evercels would sag to just 307V under a 3C discharge (~250-270A) by the time just 5Ah of their available capacity was used (i.e. still >93%SOC): 307*270= ~83kW, not bad, but a far cry from the 360*300= 108kW one might have expected, and it just drops further as the pack discharges. > God I hope the > Everecells get here and are as good as we See in testing. Yes, and this is the other issue, of course: there are very few people using Evercels in EVs right now, and those that are seem to have the last of the US-produced batteries... who knows how similar the offshore (Chinese?) product will be in terms of unit-to-unit consistency, cycle life, etc. if/when they are available? Cheers, Roger.
