jeanb Posted May 28, 2023 Report Share Posted May 28, 2023 We would appreciate some comments/advice please. We’ve noticed the last couple of days that both our starter battery and our domestic bank seem to be reading higher than usual following our daily cruise, as measured by meter. We tied up an hour ago and have 13.01v on starter battery and 12.82v on main batteries. The installed multimeter is reading a tad higher. As we’re only used to observing about 12.6v we’re wondering if our 4 year old batteries that have been on trickle charge all winter are on the way out. Apologies if this has been covered elsewhere. Link to comment Share on other sites More sharing options...
rusty69 Posted May 28, 2023 Report Share Posted May 28, 2023 12.8 v is fully charged for a lead acid battery with no load on it. Do you have any loads on? Have you removed any surface charge? Assume you have no solar. Link to comment Share on other sites More sharing options...
jeanb Posted May 28, 2023 Author Report Share Posted May 28, 2023 Thank you rusty, only the inverter and 240v fridge on and no solar. So I appear to be worried about nothing. Link to comment Share on other sites More sharing options...
rusty69 Posted May 28, 2023 Report Share Posted May 28, 2023 Just now, jeanb said: Thank you rusty, only the inverter and 240v fridge on and no solar. So I appear to be worried about nothing. I would be more worried about the 12.6v to be honest. Give them a bit of exercise from their winter on hookup, see if they can support your loads at a decent voltage between 12.2 and 12. 7. I suspect they are OK. Link to comment Share on other sites More sharing options...
matty40s Posted May 28, 2023 Report Share Posted May 28, 2023 It is what I would hope you see after a good cruise. Link to comment Share on other sites More sharing options...
Tony Brooks Posted May 28, 2023 Report Share Posted May 28, 2023 I would suggest that as soon as the fridge cuts in the inverter should remove the surface charge PDQ, So 12.82V on the domestic bank is probably fine and the 13.01V on the engine bank is just surface charge. If you want to see if that is true, just spin the engine on the starter for about 30 seconds with the stop operating. I bet the 13.01 will drop to about 12.8 ish. Just keep an eye on the voltage an hour after you shut down for the day and again in the morning, that will give you a fair idea about how the batteries are doing. Link to comment Share on other sites More sharing options...
blackrose Posted May 28, 2023 Report Share Posted May 28, 2023 Surface charge innit! Link to comment Share on other sites More sharing options...
rusty69 Posted May 28, 2023 Report Share Posted May 28, 2023 Opposite of depth charge innit. 1 Link to comment Share on other sites More sharing options...
Ronaldo47 Posted May 28, 2023 Report Share Posted May 28, 2023 (edited) Here's an explanation of why the voltage is higher immediately after a battery comes off charge, from a book on accumulator charging, see page 33 and graphs on page 34. It was published in 1942, but I don't think lead-acid technology has changed significantly since. The graphs represent behaviour using a voltage source higher than the accumulator, a series resistance being used to determine the charging current. On a boat, the alternator's regulator would prevent the charging voltage per cell from becoming as high as that shown in the graph. Accumulator charging 1942.pdf Edited May 29, 2023 by Ronaldo47 typos Link to comment Share on other sites More sharing options...
jeanb Posted May 29, 2023 Author Report Share Posted May 29, 2023 We are very grateful for all your replies and advice. Link to comment Share on other sites More sharing options...
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