Battery charging question

[iabass8]

Just got new water pump/impeller/tstats/filter done on boat and hooking everything back up and loading the boat today. Everything was working as is. All connections are cleaned and secured very tight. 

I have a 3 bank dual pro 15a onboard charger. 

Batteries:

2 Trolling motor (only thing that is hooked up is trolling motor/fuse) - Size 29 EverStart MaXX

1 Cranking (has both deck and helm electronics and accessories hooked up to it) Size 31 AGM 800 CCA/1000 MCA 200 res

Hooked up charger and they charged right up to flashing green. (Still flashing green-waiting for them to turn solid)

Motor is not running to be clear. Last thing I did was turn on Electronics to make sure all is well. (charger is still flashing green lights). Steering wheel voltage (I have bow voltage off at the moment) read 16.1 WITH charger plugged in. After a while it sat at 15.6-15.7. I unplugged the dual pro and the voltage immediately dropped and stabilized at 12.8-12.9.  Again, I don't recall if I've ever turned on the electronics at home and noticed this. Is this normal for 15a onboard chargers to charger at such a high voltage? I'm waiting for them to turn solid green to check voltage again. My father in law has my multimeter so I cannot check myself until tomorrow. 

[iabass8]

Just checked voltage again when lights turned solid green . At a solid green light AND plugged in charging,  voltage read correctly at 13.2-13.3 and stable. trimmed the motor up and down and it dropped as it should to 12.9 (ish) and then back up to 13.2-13.3 and remained stable. 

I'm guessing the 15.7- 16.1 is the voltage a 15a Dual Pro uses to charge at the flashing green stage? 

[Kevin22]

You are correct on all points. The charger is telling you its full, but still "topping them off" at charging voltage, when it turns solid it goes into maintenance mode until it reads volts below 13 and charge at near 16V until it reads full (13.2ish) and then kick back into maintenance mode. 

That is why you will see that most fish finders are listed up to 17V now, so they are "charger safe"

When you turned on your voltmeter and it said 16V  it read what the charger was outputting, not what your batteries were.. Your batteries were not over 13.2-13.3 or they would be fried. When it goes into conditioning mode it stops outputting, which is why you saw the voltage fluctuate. 

[iabass8]

16 minutes ago, Kevin22 said:

You are correct on all points. The charger is telling you its full, but still "topping them off" at charging voltage, when it turns solid it goes into maintenance mode until it reads volts below 13 and charge at near 16V until it reads full (13.5ish) and then kick back into maintenance mode. 

That is why you will see that most fish finders are listed up to 17V now, so they are "charger safe"

When you turned on your voltmeter and it said 16V  it read what the charger was outputting, not what your batteries were.. Your batteries were not over 13.2-13.3 or they would be fried. When it goes into conditioning mode it stops outputting, which is why you saw the voltage fluctuate. 

Hours searching google and .pdf  manuals and this was the most helpful post.

You are the man. 

[Kevin22]

You should still check your user manuals of course. Its been a few years since I worked with a dual pro so I was going off of how 95% of multi-stage chargers work. Charge at 14-16V until full, then go into maintenance (float, conditioning, etc) mode until they sense voltage below full. Some kick off, some charge at 13.2... I think my minn kota holds at 13.2 in float mode, yours must turn off output if your voltage dropped like it did. Its all normal. If you unplug your charger, within a few days they will drop to 12.5-12.9 depending on brand which is again normal. Auto chargers that shut off in float mode will sense the drop and kick on and bring it back to 13.5ish before kicking off. 

All sounds normal to me though!