Best way to charge and maintain batteries?

I've never had a boat with a trolling motor before. My new-to-me boat has a 24 volt system with an onboard charger. The previous owner said he we just plug it in for 24ish hours when he got home from a trip. And then plug it in again for a few hours before the next use. Not sure I feel comfortable leaving it plugged in all the time (and I think the previous owner felt the same). What do you guys think?

I'll assume your batteries are flooded lead acid.

A "good" charger can be left on and hooked up all the time.

A cheap charger can overcharge your battery and/or cause you to loose water in the cells.

Look for a battery charger that is also a "maintainer".

FWIW - I don't have my boat on the charger all the time. I do, however, have my wife's car and my tractor on charge all the time. No problems. Using Schauer Maintainers.

LiPO4, AGM, etc. require special chargers and charging conditions.

I do the same rhing, plug in to recharge as soon as boat is back in my barn. Unplug after 24 hrs, wait a day and check charge. If charge is up to par the battery will hold that charge for a week easy. I do use a maintainer over the long winter storage. I just use Walley World batteries and typically get 4-6 years of life from my batteries. Maintainers are only needed for long term storage. If your built in chargers are of good quality, you should be good.....

airshot said:

I do the same rhing, plug in to recharge as soon as boat is back in my barn. Unplug after 24 hrs, wait a day and check charge. If charge is up to par the battery will hold that charge for a week easy. I do use a maintainer over the long winter storage. I just use Walley World batteries and typically get 4-6 years of life from my batteries. Maintainers are only needed for long term storage. If your built in chargers are of good quality, you should be good.....

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Agree with Airshot. Except, I do not leave a maintainer on. Lightning and power surges is the reason I don't, but you may hae a more stable grid. I just recharge them around the 2 month mark.

OK great! Thanks for the tips!

It all depends on the type of battery, follow the recommendations of the battery manufacturer and be sure to use the recommended type of charger. A cheap generic charger can cause you a lot of grief and trouble.

With lead acid deep cycle I’ve done both but, it does really boils down to the charger. A modern charger will do a bulk charge, a float charge in two or three steps. I left one of these plugged in for the winter while my boat was in storage one winter.

The same boat and chargers, fast forward a couple of years. I keep the boat in different storage unit across the road from the boat ramp. The owner of the storage unit says I can use his electricity to charge but, he doesn't want it charging all of the time. My compromise was to install an industrial timer that disconnects the charger after 12 hours. It seems to work Ok.

In hindsight a 24 hour timer would be a better choice so it can float charge longer.

The chargers I have are supposed to be "smart" chargers. I hope they are because I have them plugged in just about all the time I'm not out on the lake.

Lead acid batteries should be charged prior to storage. With LiFe PO batteries it’s a different story, they prefer storage about half charged then topped off before use. Some chargers have a mode for a storage charge.

Personally I don’t worry about it too much with exception of doing a storage charge prior to winter storage.

CRS said:

It all depends on the type of battery, follow the recommendations of the battery manufacturer and be sure to use the recommended type of charger. A cheap generic charger can cause you a lot of grief and trouble.

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^^This!^^

I actually forgot. I left my bass boat on charge all the time when I had it. It was stored 20-miles from my home (but closer to West Branch...).

Regular flooded lead-acid batteries. Cheapo Duracell deep cycle batteries.

Charger was a Minn Kota. No problems.

I also kept my Torino on charge 24/7 when not in use. Schumacher maintainer.

FuzzyGrub said:

Agree with Airshot. Except, I do not leave a maintainer on. Lightning and power surges is the reason I don't, but you may hae a more stable grid. I just recharge them around the 2 month mark.

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That works as well....by allowing them a slight discharge then a recharge is good for the battery! Actually a manual version of what a maintainer is supposed to do.

I use a Harbor Freight Viking 4 Amp Charger/Maintainer. One for each boat. I keep them on all year round. I have 2 leads run in parallel in each boat. I do test them all separately at the end of the season and beginning of the season. I check the voltage, load, specific gravity and water levels of the cells and clean any corrosion.

Look up the manual for the charger brand and model. It will tell you if it is strictly a charger or charger and maintainer. If it's the latter, leave it plugged in and check it each month to see if it needs any fluid added to the cells.

CincyGus said:

... leave it plugged in and check it each month to see if it needs any fluid added to the cells.

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^^^This^^^ is the reason I don't use a maintainer, and I have excellent success with batteries, both in longevity and power retention. I have seen batteries boil dry using maintainers and chargers constantly plugged in.

• I charge the battery fully immediately after use and then unplug.
• Once a month during storage, I will plug in the charger until the light turns green, usually no more than 15 mins. If one takes longer, I take note of which battery.
• Over the last 30 years, I have rarely ever had a problem with my batteries until they eventually die, usually after 6-7 years, sometimes longer. I currently have a battery that is a 2015, and it's still going strong.

I'm sure some of the newer stuff is better, but my batteries last as long or longer than my friends who are always fussing over their batteries, so I'm happy with my system.

I also think it's a mistake to leave those chargers plugged in 24/7. They certainly aren't cheap. I let mine charge overnight and then unplug it in the morning. If it's been a long time, I will plug it in for a little while before leaving on the next trip, usually doesn't take long to top up.

CincyGus said:

Look up the manual for the charger brand and model. It will tell you if it is strictly a charger or charger and maintainer. If it's the latter, leave it plugged in and check it each month to see if it needs any fluid

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thill said:

^^^This^^^ is the reason I don't use a maintainer, and I have excellent success with batteries, both in longevity and power retention. I have seen batteries boil dry using maintainers and chargers constantly plugged in.

• I charge the battery fully immediately after use and then unplug.
• Once a month during storage, I will plug in the charger until the light turns green, usually no more than 15 mins. If one takes longer, I take note of which battery.
• Over the last 30 years, I have rarely ever had a problem with my batteries until they eventually die, usually after 6-7 years, sometimes longer. I currently have a battery that is a 2015, and it's still going strong.

I'm sure some of the newer stuff is better, but my batteries last as long or longer than my friends who are always fussing over their batteries, so I'm happy with my system.

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If a maintainer ever overcharges, or boils a battery it is faulty ! Maintainers do a slight discharge and then top it off to keep sulfation off the plates. Many cheap chargers will overcharge a battery. My "Battery Tenders" have been maintaining my batteries for over 20 years with O issues.

thill said:

^^^This^^^ is the reason I don't use a maintainer, and I have excellent success with batteries, both in longevity and power retention. I have seen batteries boil dry using maintainers and chargers constantly plugged in.

• I charge the battery fully immediately after use and then unplug.
• Once a month during storage, I will plug in the charger until the light turns green, usually no more than 15 mins. If one takes longer, I take note of which battery.
• Over the last 30 years, I have rarely ever had a problem with my batteries until they eventually die, usually after 6-7 years, sometimes longer. I currently have a battery that is a 2015, and it's still going strong.

I'm sure some of the newer stuff is better, but my batteries last as long or longer than my friends who are always fussing over their batteries, so I'm happy with my system.

Click to expand...

@thill, when not in storage but let's say been two weeks since you were out. Do you put it on the charger the night before going out again, or rely on that charge after the last use two weeks ago. I think I'm probably asking a dumb question, but that never stopped me before.

I just charge mine back up the night before or a few hours before going out. I have a manual charger though so it's pretty fast. Just keep an eye on the electrolyte. I just found out the hard way that a deep cycle really gases a lot. My cells were exposed.

I usually run a voltage check the night before going out. As long as I am 12.6-12.8 volts, no extra charging needed, but if they drop below 12.6 then a top off is needed. Actually, never have I run my batteries low...even after a 6 hr day of trolling, my batteries are still well over half charge ( 12.2-12.3 volts) . From my reading and talking to a local battery company, getting that battery charged back up fairly quickly is the key to a healthy battery.