A different kind of on board charger question

[propster]

Looking for some input from Marine Man or someone knowledgable on this subject. With today's automatic chargers that reduce charge rate and even switch to maintenence mode, I believe it's still an on/off deal and voltage stays up or is rising while charging, kind of a force feed situation. And this can still cause the cycling condition, which can reduce battery life. Even Schumacher, maker of Ship-n-Shore brand, states on its web site that automatic chargers, while definitely more friendly to batteries than a manual charger, are not designed for long term, leave-on use use because they will develop this cycling condition, even though they won't overcharge the batteries. What they don't state is what kind of time frame this occurs. Are we talking 24 hrs? A week? At what point does cycling become a concern? Thanks guys.

[walleyewild]

I have had an on-board charger in my boat for 4+ years, using it with AGM Batteries and I have had no cycling issues at all. Batteries are losing capacity yearly but still last the day on a full charge.

I plug the boat in when I get home and unplug it when I head to the lake, sometimes it'll be weeks between outings but the batteries are still fully charged when I leave.

The only way to really check for cycling would be to hook up a meter or graph to the sytem for a longer period of time and then check the results with the battery manufacturer.

I haven't had any issues in 4 years so not an issue for me!

WW

[jeffreyd]

if you were to load test the batteries it would tell you what kind of shape they are in. you can check the voltage with a meter, they should read 12.6 volts static. that is 2.10 volts per cell x 6 cells on a 12 volt batter. if you have a charger that is building them up, then letting the voltage come down to the set point on the charger, you will eventually build a surface or memory charge on the battery. i always like to do a deep discharge periodically on a battery (even on my computer) and then do a slow charge to full. if you leave a battery unattended for several months tho you might find that it will not take a charge.

As far as leaving a charger on as you asked, if you have a true deep cycle battery it will never get the deep discharge that you are looking for. while it will keep them fully charged, you may over time find that the charge does not last as long.

Here in AZ, if i get a full year out of a car battery, i am in tall cotton. The heat will simply destroy them. If you are in the position to add a battery to the system, two is always better than one. You will get a better holding charge on the battery. however if one of the batteries goes bad, the charge that is put into the system will try and keep that bad one charged. therefore the other battery is deprived of the charge so if you have to replace the bad one, you will end up replacing the other one shortly after. with this in mind if you have two or more batteries, you need at minimum to load test all of them.

[marine_man]

Bottom line, if you don't have a draw on your batteries cycling should not be an issue. As far as the time frame, it depends on how fast the draw is drawing the battery down. Once the battery drops below a certain voltage it will recharge the battery to the preset voltage level.

marine_man

[propster]

That's what I thought, and over time it's that constant charge/dip/charge that they refer to as cycling. That is what is said to reduce overall long term battery life. However, if it's difficult to measure and no one knows how much it takes off a battery's life, I'll probably just play it safe, charge for a day or two then unplug. Thanks.

[BoxMN]

Hey keith, what we have done for the past about 12-14 years is plug it in when we return home from fishing, and leave it plugged in until next time. That usually is within a few days at the most during the summer. If for some reason the boat doesn't get out, Erik or I will unplug it after it had time to charge. But winter, we just plug it in maybe once a month for a couple days, then unplug it.

We also always check water level in spring, once or twice during summer, and fall. You never know, sometimes we have had fuse blow or corrosion on posts, and that can wreak havoc if you don't catch it early. We had a that problem this summer. It didn't look corroded, but one post was and we were basically running on only one battery. Erik wasn't too happy about that, haha! We get about 4 good years on a set, with the 4th year starting to wear down at end of season. We are due for new set this spring.

Merry Xmas to you guys! I will be snowmobiling and ice fishing like a mad man this weekend!