I see a few here are using the LiPo4 batteries. I was initially enamored of them due to their energy density and discharge characteristics, but I've stuck with lead-acid chemistry for now… my reason: the little Battery Management System (BMS) module that's inside the case of almost all batteries of this type.
This is a little IC "brain" that allows the battery to charge and discharge properly within its limits. If it should go bad, it's my understanding that the battery is pretty much toast at that point, unless one wants to tear into the case and is able to replace the circuitry (a rather formidable, and perhaps practically impossible task). My concern is twofold: lightning and NEMP, primarily the latter.
While destructive overvoltage conditions from a lightning strike can usually be successfully shunted to ground and away from the batteries in a properly designed and grounded solar power or other alternative energy setup, this would likely not be the case where NEMP is concerned. Inquiries I made to people in a certain government task force on NEMP a couple of years ago, regarding this potential issue with the LiPo4 BMS, were not at all reassuring, and indeed confirmed my concerns that this was a weak spot that could well render a system using such batteries inoperable in the event of an NEMP event.
At issue is the fact that, as best as can be determined (and the battery manufacturers are of very little help in this regard), these modules have been designed with little to no shielding or bypass, and are extremely susceptible to overvoltage conditions such as would occur from both the E1 and E2 pulses of any substantial NEMP. Failure of the BMS is almost a certainty in such an event, unless heroic efforts have been made to shield the batteries themselves along with the entire solar power system, which is of doubtful effectiveness unless done to TEMPEST standards or better, a rather expensive proposition.
One must judge for oneself how much of a threat they think this presents to their systems, and plan accordingly. Solar panels, at least the single-crystal silicon variety, are remarkably resistant to the effects of NEMP (save for their blocking diodes), as are lead-acid batteries. Charge controllers and inverters are another matter, and require proper bypassing and shielding if one expects them to survive… having replacements for these components on-hand, kept in a shielded metal container, might be the most effective way to deal with this, short of extensive modifications.
Just something to keep in mind in these rather uncertain times.
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