mainsail battery

Originally Posted by CanonDale1 View Post
I'm wondering if I'm actually shortening the life of these batteries by constantly keeping them overcharged. Thoughts? Does a deep cycle flooded battery need to cycle to retain a 13v charge? The battery charger is a "smart charger" in that it transfers to float mode once a certain charge is met, but seeing then drop to 12.3, or 12.1 if I have lights on is a bit concerning. I also leave my 12v refer on while plugged in to shore. Does this constant flow of voltage through the battery lower its stand alone abilities?
#1 Your batteries are pretty much toast and by industry standards have likely been technically "dead" for quite a while. #2 Float charging can cause grid corrosion, but is a higher risk in VRLA (GEL or AGM) than it is in flooded batteries due to the recombination process creating excess heat. Despite this your batteries placed in 100% float time service, think emergency UPS back up type use, would still outlast perhaps 99.99% of the batteries used in a PSOC (partial state of charge) deep-cycle manner in the marine space. In other words your biggest enemy is not floating it is deep-cycling, crappy chargers, non-temp compensated charging, chronic undercharging, dock side power losses with DC loads running, PSOC use etc. etc. etc.... #3 What is damaging & bad about "floating" is that very few marine "smart" chargers can hold a continual float during refrigeration compressor cycling. This is causing the charger to switch back and forth between a float level voltage and absorption level. The solution to prevent reverting to absorption, from always on loads, is to simply create a charge profile for dockside charging with it set for only float level voltages at just a tick over resting voltages such as 13.2V. Charge to 100% SOC and then switch to "forced float" or simply turn off the DC loads...... Poor chargers with high ripple are also damaging, especially to VRLA batteries. Also very damaging is the use of a non temp compensated charger that lacks an on-battery temp sensor. Most "marine" chargers out there really suck donkey nads. There is no perfect marine battery charger, it has not yet been built, so be sure to buy one that has a forced-float feature/switch or one that you can custom program to remain in float while dockside, if you really must run dock side DC loads. Forcing the charger to stay in float will not allow the refrigeration compressor start up to launch the charger back to absorption multiple times per day. Some "smart chargers" are so dumb that any voltage sag from the fridge compressor can cause the charger to revert back to absorption. Many of these chargers then start what amounts to a kitchen egg timer that may hold absorption for anywhere from an hour to four hours. This is what is damaging to the batteries. #4 It is fairly well known that I'm not a proponent of shore side charging & always-on dock side loads, for any reason, and I like cold beer like everyone else. I see FAR, FAR, FAR too many destroyed banks due to charger failures, cyclic absorption cycles due to demand loads, and AC power interruptions. These glitches are on the order of about 15k in ruined batteries yearly due to shore power interruptions with DC loads left on. In contrast I have seen no batteries destroyed by loss of shore power by owners who run solar instead of plugging into shore power. Shore charging, with always on loads, are simply a risky practice. I generally prefer to maintain the batteries unplugged from shore by using solar. Last time I checked the sun has not been interrupted for millions of years yet dock side power is routinely interrupted. If it gets interrupted the battery can be cycled to 0% SOC without you even knowing it. Smarter smart chargers won't even re-boot if battery voltage is too low for obvious safety reasons. Once your batteries are full it takes very, very little sun to maintain them and even in pouring rain there will be sufficient charge to maintain them. Plugging into shore power without a properly wired isolation transformer is simply a risky practice too and no, a galvanic isolator is not the same as an isolation transformer.. Even with an isolation transformer leaving loads running leaves you with the potential to MURDER your bank when the power goes out, which it does on docks with surprising regularity. If you really must leave DC components running when dock side: -Use the smallest current charger you can to maintain the DC loads and battery. It should be able to be "forced to float" with no way to revert to absorption. - Install a DC low voltage cut off/disconnect set to at least 12.1V for the "always on loads". - Install a properly wired isolation transformer. - Consider using your "cheap" starter/reserve battery as the DC buffer/float power instead of an expensive house bank. It should have it's own charger if you do this not just one leg of a charger. #5 Five years use on automotive cased "marine batteries" (G-24, G-27, G29/30/31) is decent service life. Most are technically dead at anywhere between 2 years and 4-5 years anyway. If your have not been cycled and only float charged they can easily last 8 years. Any sort of cycling or partial state of charge use sucks the life out of them pretty quickly..