> I have a single bank smart charger 55 amps that I use with the genset when away from the dock. I plugged it in and it brought the batteries back up to 13.4-13.7 volts where they generally stay when charged and warm in the summer. > Is my assumption that the temp. is the issue that limits the voltage cold and that the larger charger is better at sensing this issue even without battery temp. sensing? Any explanations or opinions?
REPLY Liveaboard boats and cruisers which have to leave a boat plugged in for a couple of months may in fact suffer from over charging. In varmer climates even 13.4 - 13.7Volts is too high for sealed batteries. Liveaboard boats experience an additional condition that results in a so called smart charger to over charge a battery. By definition a smart charger has to supply about 14.2V - 14.4V during the absorption stage. Otherwise the batery wil never become fully charged. The transition from absorption to float stage is usually determined by noting when the charge current drops to approximately 2% of nominal full cutrent of the rated charger capacity. The exact transition point varies with brand and manufacturer so it could be 1% or 3%. Point being this is a very low level. One 20 Watt halogen bulb draws 0.75 amp at 24V and 1.5 amp at 12V Until the smart charger sees the charge current drop below this threshold it may keep the charger in the absorption stage and hold the voltage at 14.2V Way too high for tropical warm climates. Result; the battery will be above the outgassing stage and boil off the electrolyte. If the connected load draws even a tiny bit more than this very low threshold, you will never see the charger transition to float mode. Secondly; some temperature compensated chargers only adjust the output voltage during float stage, even when a battery temp sensor is connected. Your best bet is to turn off the charger with a timer or to manually shut it off after a certain time has elapsed. This time is naturally dependent on the battery bank capacity but 10 - 12 hours in absorption should be suficient provided you have sized the charger to match the battery bank capacity. A few of the newest models now have an automatic shut off feature but many do not. While I was still employed by Xantrex I was tasked to investigate rumours that perfectly good chargers still ruined nearly brand new sealed batteries in as little as three months. The above summarizes what I discovered. Arild _______________________________________________ Liveaboard mailing list Liveaboard@liveaboardnow.org To adjust your membership settings over the web http://www.liveaboardnow.org/mailman/listinfo/liveaboard To subscribe send an email to [EMAIL PROTECTED] To unsubscribe send an email to [EMAIL PROTECTED] The archives are at http://www.liveaboardnow.org/pipermail/liveaboard/ To search the archives http://www.mail-archive.com/liveaboard@liveaboardnow.org The Mailman Users Guide can be found here http://www.gnu.org/software/mailman/mailman-member/index.html
