Re: [Amel Yacht Owners] My batteries are dying.

Mohammad Shirloo

Hello Steve;

Your battery monitor is calculating the charge percentage. These calculations could easily be erroneous based on several different factors.

Typically AGMs charge at around 28.4 volts and float at 27.2. These voltages vary based on battery temperature if your chargers have temperature feed back from your batteries. A voltage of 25.95 in float sounds low.

The main read out from your monitor that does not involve any calculations, is the amount of amps drawn from your batteries.

I suggest turning off the charger and turning it back on after a few minutes, and let it go through all stages of charging until it has reached float. The batteries should now be at 100% charge if your charger is functioning correctly. Again 25.95V sounds low. 

Once in float, reset your battery monitor to zero Ah and then turn off the charger and use the batteries as you normally would. You should roughly have used about 30% of your total Ah capacity by the time your battery voltage reaches 25 volts. For example if you have 500 Ah total at 24volts, you should see 150 Ah used.

These are very rough guidelines and can vary based on many different conditions. However you should be in the ball park. If you are way off then something is not right. 

I would chase down the smart charging algorithm of your charger. Sometimes they need to have updates in order for them to function correctly. This has happened to us and the update resolved the issues.


Mohammad & Aty
B&B Kokomo
AMEL 54 #099

On Jul 21, 2018, at 5:32 PM, Steve Bode stevenmbode@... [amelyachtowners] <amelyachtowners@...> wrote:


I just purchased new AGM batteries in January. They were working great for months. I kept checking the battery box of heat or smells. Everything looks great. I have a new Sterling ProChargeUltra 30a charger installed. When I replaced the batteries, I set the charger to use the AGM profile. The charger seems to be working fine. When I power it up, it'll read 30a for a while and then float down to about 3-4 amps and eventually I get the float light. For months, I have been checking the original Magnetronic DCC 4000 battery meter to monitor charge. It was telling me the batteries are at 100% and the Ah were close to 400. 

Then, about a month ago, the percentage of charge and the Ah began to read lower. I would check the charger and it would say that it's in float, but the percentage on the meter was dropping every day. 70%, 60%, 50%. My charger has been plugged into the dock for 5 days and the meter reads 40% and the charger is in float. The voltage reads 25.95v. 

Should I panic? Am I doing something wrong? Is it possible that the engine alternator has been overcharging my AGMs? Any advice?

Steve Bode
Sailing Vessel Intention
Amel Super Maramu 1994 #117

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