Normal battery voltages under load

[Jtreed99]

I’ve had slow cranking issues recently from my 31AGM X2 from batteries plus. Dual pro always shows green light but voltage check (with all switches off nothing connected but charger and charger unplugged) after they sit for 24 hours shows 12.49 whereas my Duracell agms for trolling each show 12.77-12.79.

Doing some driveway testing while running the trim up and down with all 4 chart screens on I can drop voltage at the battery to 11.9 but during this same time the voltage at the motor dropped to 10.8. If the trim motor can drop it that low there’s no telling how low the starter is dropping it Wiring is 4 gauge and wire and connections appear to be in excellent shape. Battery and trim unit are both about 1.5 years old. It’s always been slower than I feel it should be to turn over but never really noticeable til the cold weather. Should I focus my efforts on the battery or the wiring? Both?

[rocketman6965]

I'm not the electrical expert but I just checked my batteries before fishing tomorrow. Check was done after removing charger for 24 hours. I have 3 Sam's 31 series wet cells for troller and a 31AGM from Interstate. I know everyone thinks Interstate is crap but I must've gotten a good one because I've had it since Jan 2014. The trolling batteries were a total of 38.85. Each one was 12.98, 12.98 and 12.89(not a typo). The Interstate cranking battery was 12.98. "(with all switches off nothing connected but charger and charger unplugged)"

[CatFan]

12.49V is too low, but you need to disconnect everything from the battery after charging to really be able trust the reading.

[Jtreed99]

Disconnect everything as in charger included? The wires were still there but they only went to open switches except the charger went to the charger circuit board.

[CatFan]

Disconnect everything as in charger included? The wires were still there but they only went to open switches except the charger went to the charger circuit board.

Charger won’t hurt. No connection to the outboard?

[bayoufellow]

Is your Dual Pro charger made for charging AGM batteries? If not, you will see all green lights, but the batteries will not have been charges properly. Call Dual Pro with the model number of your charger and your battery make/model, they will be able inform you of any issues there. I had the same issues with my first set of AGM batteries. I did not realized that the charger has to be made and programmed to handle the needs of the AGM battery. My batteries are considered charged when they are reading a voltage of 12.85

[CatFan]

Is your Dual Pro charger made for charging AGM batteries? If not, you will see all green lights, but the batteries will not have been charges properly. Call Dual Pro with the model number of your charger and your battery make/model, they will be able inform you of any issues there. I had the same issues with my first set of AGM batteries. I did not realized that the charger has to be made and programmed to handle the needs of the AGM battery. My batteries are considered charged when they are reading a voltage of 12.85

Not really correct. Any modern charger will charge AGMs fine. Some manufacturers want specialized float processes, but that only affects longevity. It will still charge fine.

[Jtreed99]

It’s a current gen charger with delta volt supposedly great for agm batteries.

[Jonestrollingmotor]

The 12.49 is too low -- partially discharged at this point.

[billnorman1]

Well, you have the opportunity to swap one of the trolling motor batteries in to the motor circuit to do some checks. Many modern computer controlled motors won't start if the battery voltage is below 11 volts. It will probably drop down to 11 volts for an instant when the starter is first engaged.
Are you using the Duracell AGM 31 starting/deep cycle batteries?

[Jtreed99]

Charger won’t hurt. No connection to the outboard?

No, positive wire wide open while charging/storage.

[Jtreed99]

Well, you have the opportunity to swap one of the trolling motor batteries in to the motor circuit to do some checks. Many modern computer controlled motors won't start if the battery voltage is below 11 volts. It will probably drop down to 11 volts for an instant when the starter is first engaged.
Are you using the Duracell AGM 31 starting/deep cycle batteries?

Yes 3 Duracell 31AGM for troller but batteries plus X2 power 31AGM for starting and electronics.

[Jtreed99]

The 12.49 is too low -- partially discharged at this point.

Thanks John. I will try to get it in to have it load tested this week since it’s discharging so quickly on its own with nothing connected to it.

[BoatNoobie]

Try switching the banks on the charger around just to see if the bank is faulty or battery.

[Jtreed99]

I put a dedicated agm charger on it to test exactly that. Even though the dual pro had given the green light the dedicated charge only read 98% but went to 100 very quickly although it’s been a couple hours and it hasn’t swapped over to trickle yet. Will leave it overnight and test tomorrow. It does have a 4 year replacement warranty.