Dual Batteries question?

daanbc

Petty Officer 3rd Class
Joined
May 1, 2016
Messages
75
Hello, I have a 16.5 Alumacraft competitor with a 60 hp evenrude tiller. It has two batteries. Both are brand new. (less then three months old) I have a battery switch for #1, off, #2, all. Wednesday after two full hours of using the trolling motor with 4 people in the boat, the batteries were dead enough to not start the motor. It would turn over once then not enough for a second shot. After turning everything off and waiting 15 minutes, I was able to start the motor on the next try. My question - I purposely had the switch on #2. Thinking If I was to kill the battery, I would have #1 to start the motor. But both seemed dead? When I got home I checked the batteries, one had 8.9 the other 10.6 Isn't the switch suppose to isolate one battery from the other when you just pick either #1 or #2? Why did both drain? I can honestly say the boat has been taken out four times since the new batteries. All the times have been very little motor use and a lot of trolling motor use. Is there a way for me to check to see if my motor is charging them? The volt meter shows 12-13 when running. Thanks in advance Dave.
 

fhhuber

Lieutenant
Joined
Jun 19, 2014
Messages
1,365
May not have actually charged both batteries before leaving the house?

And you need to NOT be draining a 12v flooded lead acid or gel cell below 11.0 v. Its not good for them.
Actually best to keep them 12.0V or above.

Below 9.0v you need to carefully recharge and check the battery voltage 4 hrs after you turn the charger off. It may have 1 or more dead cells.
 
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sam am I

Commander
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Jun 26, 2013
Messages
2,169
My guess is If he's running a 24V TM, he/it is most likely wired to operate regardless of the Off/1/Both/2 switches position. i.e., The/a 24V TM in order to work at 24V (he said they'd trolled for 2 hours) must be wired across both batts and therefor he was drawing current from both batts by default and independent of the O/1/B/2 switch line-up. Again, just a guess w/o more info..........
 
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ondarvr

Supreme Mariner
Joined
Apr 6, 2005
Messages
11,527
You should see 13.5+ volts to actually be charging the batteries when the motor is running, but depending on the exact motor, you may not have the amps to do much charging unless you run for hours to get to where you fish.
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,758
A 16.5 foot boat does not need a 24 volt motor but that certainly doesn't mean he doesn't have one. A poorly designed and connected dual battery switch coupled with not fully understanding it's use could very likely be the problem. A 60HP outboard engine charging system is hard pressed to charge one battery running wide open for hours at a stretch, much less two of them. Not charging the batteries at the dock at the end of the day is battery suicide. If the starting battery is indeed being used in a 24 volt trolling motor application, that is also a good way to experience what was experienced.
 

daanbc

Petty Officer 3rd Class
Joined
May 1, 2016
Messages
75
Its a minn kota power drive v2. I believe it is only a 12v not 24. The original owner of the boat placed the second battery in for the trolling motor. I was under the presumption that I did NOT have to charge my batteries because I thought the motor was enough. But after reading your replies, I now understand how BOTH became drained. I used the boat four times, never really using the motor at all, just the trolling motor. So the start battery never really got charged and I was using it to start and at times had the battery switch on ALL. Plus I mainly used the TM, which drained the other. Thank you gentlemen.
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,758
All means whatever 12 volt stuff you were using (mostly the troller apparently) both batteries are being used to supply that current. If you were not running the engine much, how did you expect the batteries to get charged. A 10 minute run back to the dock would add very little charge. That 60 HP outboard probably has a 12 amp alternator. Your troller on the other hand at maximum speed draws over 40 amps. So one hour operation of the troller (or a combination of run times that equals one hour use totalling 40 amps) means the outboard would need to run wide open for three hours to even get close to charging the batteries. There is no free lunch with battery power. What you take out must be put back. The only way that can happen is at the dock or home with a good charger. Your engine is not up to that task. You should use ALL only in emergencies where both batteries might be needed to start the engine. Otherwise, with batteries charged at home or at the dock, set the switch to #1 and run to your fishing hole. Switch to #2 and do your thing. You can even start the engine on #2 and move to a new spot. If the engine is in good tune and you know how to start it properly, you should only have to crank the engine a couple of seconds. The next run would likely put back a good amount of the power you used to start the engine. This way #1 stays unused. You can switch back and forth between #1 and #2 if you don't mind the bother. If you have a one hour or more run somewhere, switch to the battery that needs attention. No sense feeding two batteries when only one needs charging.
 

daanbc

Petty Officer 3rd Class
Joined
May 1, 2016
Messages
75
My previous boat was a 19' bowrider with a 4 cyl. mercruser. I never had to worry about the battery on that boat. Had it four years and changed the battery when I first got it. Never realized that the outboards don't charge as great or fast. For now on I'll have them charged when I put her back in the garage.
 
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