Battery Drain Question

[JohnnySCV]

Hi Guys, thanks in advance for your input.

Fished an 8 hur tournament today in some brutal winds. I didn't really notice my trolling motor acting up at all but when I got home my buddy checked the voltage on the batteries to see how drained they were One battery was 10.7 volts and the other was 12.7 volts. It is a 24 volt system with two 27 series batteries hooked up in series.

My feeling is that the 10.7 battery is eaither gone or just about to go. Is there any other reason that one battery hooked in series would be that mch more drained than the other?

Thanks again!

J.V.

 

[glenn property of pam]

Re: Battery Drain Question

10.7 may be a drained battery or a battery that has a shorted cell. you can try to charge the battery then retest the voltage. if the cell is shorted it will not read higher than 11v after being chargerd and the battery will need to be replace. there is no reason 2 batteries the same size/brand should discharge at diffrent rates.

(edit) i should have said 2 batteries in good condition with the correct fluid level etc should not discharge at diffrent rates

 

[UncleWillie]

Re: Battery Drain Question

Are the two Batteries for the Trolling motor Exclusively?

Does one battery also supply the 12v for the Fish Finder, Live Well Pumps, etc.?

10.7v sounds about right for 8 hours of trolling. The 12.7v is the suspicious number.
If one was at 12.7 that means at some point it had been recharged on the way home.
A partially discharged battery will be at 12.4 or below. Never above 12.6!
If they were both at 10.7 and then one was recharged when the gas motor was re-started, your voltages are to be expected.

 

[glenn property of pam]

Re: Battery Drain Question

Are the two Batteries for the Trolling motor Exclusively?

Does one battery also supply the 12v for the Fish Finder, Live Well Pumps, etc.?

10.7v sounds about right for 8 hours of trolling. The 12.7v is the suspicious number.
If one was at 12.7 that means at some point it had been recharged on the way home.
A partially discharged battery will be at 12.4 or below. Never above 12.6!
If they were both at 10.7 and then one was recharged when the gas motor was re-started, your voltages are to be expected.

very well thought out. most bassboats have 3 batteries with the trolling motor batteries used just for the trolling motor but you are proberly spot on as most boats also have a transfer type charger installed so when the motor battery is full the charger switchs to the trolling batteries.

 

[JohnnySCV]

Re: Battery Drain Question

Yes the batteries are exclusivey for the trolling motor. There is a third battery for starting, livewells, sonar, etc. The two batteries in question are only used for the trolling motor. I placed the battery in questions on a 10 amp charger on my workbech to monitor to it and it seems to be charging fine. I was also somewhat suspicious about the 12.7 reading on the so called good battery. Any other thoughts??

 

[JohnnySCV]

Re: Battery Drain Question

I should have added that only the 3rd battery (not in question) is charged when the engine is on. My boat has no transfer system that charges the trolling batteries..

 

[fishrdan]

Re: Battery Drain Question

One battery was 10.7 volts and the other was 12.7 volts. It is a 24 volt system with two 27 series batteries hooked up in series.

That makes no sense at all (not trying to sound obnoxious) as both batteries in a series/24v system get depleted at the same rate. If you ran the TM all day in high winds, I don't see how the good battery could be at 12.7v, completely charged, maybe your buddy checked the start battery by mistake? The other battery at 10.7V sounds severely depleted, or it has a bad cell. I'd double check the voltage on the 12.7v battery, charge both of them completely, then have them load tested. (BTW, running a battery down to 10.7V is really bad for it.)

If this were a 12V parallel system I could see that scenerio (batteries not paralleled), but that's not the case.

 

[JohnnySCV]

Re: Battery Drain Question

That makes no sense at all (not trying to sound obnoxious) as both batteries in a series/24v system get depleted at the same rate. If you ran the TM all day in high winds, I don't see how the good battery could be at 12.7v, completely charged, maybe your buddy checked the start battery by mistake? The other battery at 10.7V sounds severely depleted, or it has a bad cell. I'd double check the voltage on the 12.7v battery, charge both of them completely, then have them load tested. (BTW, running a battery down to 10.7V is really bad for it.)

I agree, this makes no sense at all.... I am going to charge the so called bad battery overnight and take it over to the auto parts store and have it load tested tomorrow. Maybe that will shed some light on the situation.

 

[dwparker99]

Re: Battery Drain Question

Are you sure the TM is running on 24v? The conditions you described would make sense if you were running on 12v.

 

[glenn property of pam]

Re: Battery Drain Question

do you have a perko switch the one with A-Both-B-Off settings. maybe that is set in the wrong position or is labeled incorrect

 

[UncleWillie]

Re: Battery Drain Question

There is no reason at this time to assume the 10.7v battery is defective.
10.7v on a battery that has been trolling all day is completely expected.
10.5v is considered a battery that is 100% depleted. It was time to go home!

If it takes a long time to charge; That is a good thing! If it comes back quickly; BAD!

When YOU took both batteries out of the boat to charge them; What was the voltage on the other Battery?
And what is the voltage on the Battery still in the Boat?

You should have Two 10.7v Batteries and ONE at 12.7v

 

[JohnnySCV]

Re: Battery Drain Question

There is no reason at this time to assume the 10.7v battery is defective.
10.7v on a battery that has been trolling all day is completely expected.
10.5v is considered a battery that is 100% depleted. It was time to go home!

If it takes a long time to charge; That is a good thing! If it comes back quickly; BAD!

When YOU took both batteries out of boat to charge them; What was the voltage on the other Battery?
And what is the voltage on the Battery still in the Boat?

You should have Two 10.7v Batteries and ONE at 12.7v

When I took the batteries out the votlage stayed the same 12.7 and 10.7 The 10.7 was charged within 3 hours @ 15 amps, which seems way to quick to me.... I am thinking that battery is bad, but still need to go get it load tested.

As far as swithces and other goodies there are none.... I have though about installing one but have not got around to it...

 

[Don S]

Re: Battery Drain Question

Get your batteries fully charged, then get them load tested. Then you will know for sure what their condition is.

 

[fishrdan]

Re: Battery Drain Question

The 10.7 was charged within 3 hours @ 15 amps

That doesn't sound good, at 15 amps it should have taken somewhere around 12 hours to charge the battery.

If you need to replace the battery, it's probably best to replace both of them with bigger batteries, group 29 or 31,,, if there is room in the boat. The larger batteries will give you more run time, and/or you won't be running them down so far. The less a battery is depleted on each cycle, the longer it will last.

If you have the funds for an onboard battery charger, that's a good idea too. I charged like you are for years, but now have an onboard charger and it's a heck of a lot easier with the automatic charger. Much easier to drag an extension cord out to the boat, opposed to using a portable charger.

 

[JohnnySCV]

Re: Battery Drain Question

Thanks for all the input guys. I pulled the battery off the charger, took a reading of 11.02 volts, and took the battery to the auto parts store. After a few minutes the load tested came back as a bad battery.... Mystery solved, I guess.

 

[dwparker99]

Re: Battery Drain Question

Thanks for all the input guys. I pulled the battery off the charger, took a reading of 11.02 volts, and took the battery to the auto parts store. After a few minutes the load tested came back as a bad battery.... Mystery solved, I guess.

You may have found a bad battery but I'm not sure you have solved the mystery. I agree with fishrdan, you can't fish an eight hour Tx in high winds with a 24v TM and still have one of the batteries reading 12.7v when finished especially if one of the batteries goes bad during the Tx. Either the reading was bad or you are running on 12v. If running on 12v, your new battery will have a short life.

 

[JohnnySCV]

Re: Battery Drain Question

You may have found a bad battery but I'm not sure you have solved the mystery. I agree with fishrdan, you can't fish an eight hour Tx in high winds with a 24v TM and still have one of the batteries reading 12.7v when finished especially if one of the batteries goes bad during the Tx. Either the reading was bad or you are running on 12v. If running on 12v, your new battery will have a short life.

I agree it was strange to see that 12.7 volt reading. I will have to pay closer attention in the future when I come off the lake. As far as trolling motor running at 12 volts, the batteries are run in series back in the rear compartment so I don't think 12 volts at the trolling motor is possible. I did determine that the battery that went bad was almost 3 years old so it was probably nearing it's life expectancy.

 

[glenn property of pam]

Re: Battery Drain Question

Are there 3 wires connected to the batteries in the back with either a option switch on the bow for 12/24 or a option on the trolling motor?

 

[JohnnySCV]

Re: Battery Drain Question

Are there 3 wires connected to the batteries in the back with either a option switch on the bow for 12/24 or a option on the trolling motor?

There are only two wires going to the trolling motor as it is a 24 volt only motor. That being said the postive from the "bad battery" and the negative from the good battery are run to the trolling motor. The negative of the bad battery is connected directly to the positve of the good battery.

 

[glenn property of pam]

Re: Battery Drain Question

maybe a bad volt meter reading then as the bad battery sounds like it dropped a cell and that should have read a max of 10.75 when charged where you got a reading of 11.02 so maybe the good battery was in fact 12.2v which would make way more sense