If you use the Charles charger you have and buy AGM batteries, your batteries will die an untimely death, perhaps as soon as next spring. The single most important thing you can do for your batteries is replace the charger and don't go cheap on the charger. If you think you will go to LFP batteries, then buy a good charger that will handle LFP batteries now and use FLA batteries to save on costs.
How does a battery selector switch work?
- Thread starter Ted10028
- Start date
??? my charger has a setting for AGM batteries. Why do you think I will have a problem?
Restore up to three banks simultaneously. Allows selection of charging cycles and voltages for lead acid, AGM or gel batteries. These units also act as a power supply providing constant voltage to DC components such as bilge pumps or DC lighting.
Remind me which battery charger you have. If I recall correctly in another thread you showed a photo of a Charles Battery charger. Those chargers have a fixed bulk charge time of 4 hours, whether the battery needs it or not. As a result the batteries are over charged which is just as bad as undercharging them.
The fixed bulk time chargers are OK for batteries that are routinely deeply discharged as you might find on golf cart or electric pallet mover. For a boat where the discharges are shallower, they are deadly (to the battery).
Yes, that's the charger I remember. Thank you.
From the Manual, page 12:
Again, this method of charging, with the timed absorption stage, is not bad if the battery is deeply discharged down to 50-60% because it will take 5 to 6 hours to fully charge from that level. Except, if the battery is not ready to go into the float stage, it will not receive the voltage it needs. This is damaging to the battery. This was a good attempt to optimize charging 30 years ago, we're way past that now in understanding batteries and charging protocols.
Good modern 3-stage battery chargers change stages based on the battery's ability to accept a charge. Briefly and simply, a modern charger will start with a high current charge at a low voltage. As the battery is charged the voltage will rise and at a predetermined voltage level the charger will maintain that voltage level as the current (amps) gradually decreases until is it only able to supply a small amount of current, when it will shift to a low current low voltage float level. If the battery is deeply discharged, the charger will take 5+ hours to go through those stages, if the battery is not deeply discharged the charger will only take a few minutes to a few (less than 5) hours to cycle through the stages. And that's the problem, with a timed charger, like the Charles 5000 series, there is too much time where the charger's output is out of sync with the battery's need. That causes the battery to seldom be charged at the correct stage and to often be charged at the incorrect stage.
The other and less critical problem with the Charles charger is the fixed settings. AGMs, Gels, and FLA batteries from different manufacturers have different "ideal" charging voltages. Some AGM manufacturers may want a 14.6v absorption, some may want a 14.2v absorption voltage. The charger can't be fined tuned to the manufacturer's recommendation, the Charles uses a best guess voltage.
If you are dead set on AGM batteries, West Marine has a clearance sale on Mastervolt AGM batteries at very attractive prices. While Mastervolt generally produces good equipment, the amphour capacities of there AGM batteries are on the low side for batteries of the same size.
From the Manual, page 12:
After pasting the above, I see you also read the manual. The problem is the time based absorption phase (I did not correctly recall the information earlier when I said Bulk phase). The charger will keep the voltage high even when the battery does not need a higher voltage. This is damaging to the battery and causes the off gassing that was discussed in another thread.
Again, this method of charging, with the timed absorption stage, is not bad if the battery is deeply discharged down to 50-60% because it will take 5 to 6 hours to fully charge from that level. Except, if the battery is not ready to go into the float stage, it will not receive the voltage it needs. This is damaging to the battery. This was a good attempt to optimize charging 30 years ago, we're way past that now in understanding batteries and charging protocols.
Good modern 3-stage battery chargers change stages based on the battery's ability to accept a charge. Briefly and simply, a modern charger will start with a high current charge at a low voltage. As the battery is charged the voltage will rise and at a predetermined voltage level the charger will maintain that voltage level as the current (amps) gradually decreases until is it only able to supply a small amount of current, when it will shift to a low current low voltage float level. If the battery is deeply discharged, the charger will take 5+ hours to go through those stages, if the battery is not deeply discharged the charger will only take a few minutes to a few (less than 5) hours to cycle through the stages. And that's the problem, with a timed charger, like the Charles 5000 series, there is too much time where the charger's output is out of sync with the battery's need. That causes the battery to seldom be charged at the correct stage and to often be charged at the incorrect stage.
The other and less critical problem with the Charles charger is the fixed settings. AGMs, Gels, and FLA batteries from different manufacturers have different "ideal" charging voltages. Some AGM manufacturers may want a 14.6v absorption, some may want a 14.2v absorption voltage. The charger can't be fined tuned to the manufacturer's recommendation, the Charles uses a best guess voltage.
If you are dead set on AGM batteries, West Marine has a clearance sale on Mastervolt AGM batteries at very attractive prices. While Mastervolt generally produces good equipment, the amphour capacities of there AGM batteries are on the low side for batteries of the same size.
Those are the ones you don't want to buy.
Don't take my word, take it from the real expert.
I know Maine hates those, and I’m sure he’s got the experience to be right about them in general. Having said that I got 8 good seasons out of Deka AGM’s, which are the same battery as the West Marine ones. My use case is probably about the gentlest possible for them - lots of daysailing down to about 70% SOC promptly recharging overnight, with occasional weekends or slightly longer trips away from shore power. Yes any battery would probably be fine with that kind of use, but for the cost / maintenance / longevity balance we got out of them we were happy enough to go back for more after the originals wore out.
I am always hesitant to speak for someone else, however, I think @Maine Sail's reluctance to endorse WM AGM batteries stems from these how articles he wrote some time back. That and the price of WM batteries vs the same batteries purchased with a different label.
AGM Batteries Test Update - Practical Sailor
Since 1974, Practical Sailor’s independent testing has taken the guesswork out of boat and gear buying.
www.practical-sailor.com
How Fast Can an AGM Battery be Charged? - Marine How To
TEST EQUIPMENT USED IN THIS ARTICLE BUY MHT RECOMMENDED TEST EQUIPMENT - AMAZON Baseline Discharge 49.3% SOC PREFACE: This article looks at the *charging times & achieved state of charge of an AGM battery
marinehowto.com
I agree - that’s how I remember his problems too. If I were a cruiser expecting to stay at Partial State of Charge I probably wouldn’t go that route based on his testing.I am always hesitant to speak for someone else, however, I think @mainesail's reluctance to endorse WM AGM batteries stems from these how articles he wrote some time back. That and the price of WM batteries vs the same batteries purchased with a different label.
AGM Batteries Test Update - Practical Sailor
Since 1974, Practical Sailor’s independent testing has taken the guesswork out of boat and gear buying.
How Fast Can an AGM Battery be Charged? - Marine How To
TEST EQUIPMENT USED IN THIS ARTICLE BUY MHT RECOMMENDED TEST EQUIPMENT - AMAZON Baseline Discharge 49.3% SOC PREFACE: This article looks at the *charging times & achieved state of charge of an AGM batterymarinehowto.com
When we were replacing we did price them out from different places. Under normal circumstances WM was pretty significantly more, but with patience for a really good sale they were slightly less than any price I could find for the Deka model. I didn’t check Sam’s or Napa relabels though.
Edit to add - PS I think you tagged the wrong @Maine Sail
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that's great information. Thanks . I think I am still stuck with the west marine for $300I am always hesitant to speak for someone else, however, I think @mainesail's reluctance to endorse WM AGM batteries stems from these how articles he wrote some time back. That and the price of WM batteries vs the same batteries purchased with a different label.
AGM Batteries Test Update - Practical Sailor
Since 1974, Practical Sailor’s independent testing has taken the guesswork out of boat and gear buying.
How Fast Can an AGM Battery be Charged? - Marine How To
TEST EQUIPMENT USED IN THIS ARTICLE BUY MHT RECOMMENDED TEST EQUIPMENT - AMAZON Baseline Discharge 49.3% SOC PREFACE: This article looks at the *charging times & achieved state of charge of an AGM batterymarinehowto.com
The odyssey battery is $600, the North star is not available, and the lifeline is $429. West marine is less than a mile from my boat and will take the old batteries in trade. The warranty is not great but it is local so I would have a chance to get my money back in the event of trouble. What do you think?
If you don't change the battery charger, investing in the Odessy, the Northstar, or the Lifeline would be a bigger waste of money.
These Mastervolt Batteries in the clearance bin at WM are exceptional values.
Clearance Marine Electrical | West Marine
Shop the best selection of Clearance Marine Electrical from West Marine. Visit for products, prices, deals and more!
www.westmarine.com
thanks for the west marine master volt idea. If my store has those I will get two of them tomorrow!If you don't change the battery charger, investing in the Odessy, the Northstar, or the Lifeline would be a bigger waste of money.
These Mastervolt Batteries in the clearance bin at WM are exceptional values.
Clearance Marine Electrical | West Marine
Shop the best selection of Clearance Marine Electrical from West Marine. Visit for products, prices, deals and more!
Whoops, it is just occurring to me that I cant use a group 31 battery. I need both terminals on the short side of the batteries. There goes another few hundred dollars.If you don't change the battery charger, investing in the Odessy, the Northstar, or the Lifeline would be a bigger waste of money.
These Mastervolt Batteries in the clearance bin at WM are exceptional values.
Clearance Marine Electrical | West Marine
Shop the best selection of Clearance Marine Electrical from West Marine. Visit for products, prices, deals and more!
Do you have a picture of your current setup? Both posts on the short end of the battery is not too common - it’s just not well aligned with how the posts connect to the plates inside the battery. You’ll be pretty limited in battery selection if you can’t work around that somehow.