Notices
The Boating Forum

Boat battery charging question

Old 06-05-2018, 03:52 PM
  #1  
Admirals Club Admiral's Club Member
Thread Starter
 
Join Date: Apr 2015
Posts: 148
Likes: 0
Received 80 Likes on 39 Posts
Default Boat battery charging question

I’m new to boating so please forgive this rookie question...

out on my new to me Edgewater 248 today. Cruised for a bit then did some inland fishing for maybe 1.5 hours at a few different spots. Had the livewell and radio running the whole time. Used the windlass a few times in shallow water. Motor was off for the majority of the time while fishing.

then my Garmin GPS and radio turned off. Windlass lost power. Not sure if livewell stopped working but probably.

never had a problem cranking motor, and when I switched to use both batteries, everything worked fine.

cruised home and left motor idling while cleaning the boat (maybe 30 min) hoping to recharge the battery...but the radio wouldn’t turn back on.

How long does it take to recharge a battery with the motor? Will it recharge if motor is just idling? Will I be safe if I go back out tomorrow and keep motor going while cruising and/fishing in hopes to recharge the battery? Do I need to use a battery charger at this point?

Thanks for any advice you can offer.
Old 06-05-2018, 03:59 PM
  #2  
Senior Member
 
Join Date: Jan 2011
Posts: 859
Received 120 Likes on 80 Posts
Default

What position was the battery switch during the run home and idle time? Do you have an ACR?
Old 06-05-2018, 04:07 PM
  #3  
Admirals Club Admiral's Club Member
Thread Starter
 
Join Date: Apr 2015
Posts: 148
Likes: 0
Received 80 Likes on 39 Posts
Default

Originally Posted by Paulswagelock View Post
What position was the battery switch during the run home and idle time? Do you have an ACR?
switch was to the right, on single battery. Do I need to set it somewhere else to recharge with the motor?

i don’t know what an ACR is.
Old 06-05-2018, 04:09 PM
  #4  
Senior Member
 
Join Date: Oct 2011
Location: Austin, Texas
Posts: 3,052
Received 123 Likes on 104 Posts
Default

Tell us more about what batteries you have, what amps does your alternator put out, etc., etc. etc. Also, do you not have any on-board charging?

Last edited by Bayfly; 06-05-2018 at 04:10 PM. Reason: Addition.
Old 06-05-2018, 04:12 PM
  #5  
Admirals Club Admiral's Club Member
 
Join Date: Aug 2013
Location: Sienna Plantation, TX.
Posts: 2,920
Received 1,528 Likes on 720 Posts
Default

So you discharged your battery, then you put your batteries in parallel and started the motor and left them that way. Your discharged battery will now charge at 50% the rate. And if your stator/alternator is sensing a full battery from from your good one, it may not even charge at all.

What you should have done is flip over and start from your other battery, then go back to the flat battery and let it recharge from your motor. Or better yet, get an ACR (Automatic Charge Relay) like the one from Blue Seas and never have this issue again.
Old 06-05-2018, 04:17 PM
  #6  
Admirals Club Admiral's Club Member
Thread Starter
 
Join Date: Apr 2015
Posts: 148
Likes: 0
Received 80 Likes on 39 Posts
Default

Originally Posted by popeyeiii View Post
So you discharged your battery, then you put your batteries in parallel and started the motor and left them that way. Your discharged battery will now charge at 50% the rate. And if your stator/alternator is sensing a full battery from from your good one, it may not even charge at all.

What you should have done is flip over and start from your other battery, then go back to the flat battery and let it recharge from your motor. Or better yet, get an ACR (Automatic Charge Relay) like the one from Blue Seas and never have this issue again.
no, while trying to charge it on the way back I had it set to the drained battery (not parallel)...how long should it take the motor to recharge it? Thanks
Old 06-05-2018, 05:14 PM
  #7  
Senior Member
 
Join Date: May 2014
Location: Jax
Posts: 167
Received 30 Likes on 17 Posts
Default

Amp-hours used / charging current = hours to recharge (-ish)

However, I’m guessing you don’t know the numerator of that equation (not many people do), and even if you look up the alternator spec in the owner’s manual, the denominator is a moving target depending on things like motor RPM.

Only way to know for sure is to have a battery monitor, or do it the brute force way and leave your smart battery charger plugged in until it says your batteries are charged.
Likes:
Old 06-05-2018, 05:33 PM
  #8  
Senior Member
 
Join Date: Jul 2011
Posts: 6,461
Received 946 Likes on 736 Posts
Default

Originally Posted by Gatorinthenoog View Post
How long does it take to recharge a battery with the motor?
A question which is difficult to answer, knowing all variables - and you've provided none.
"Will it recharge if motor is just idling?"
Probably - if you leave it running overnight.

Originally Posted by RS3325 View Post
...do it the brute force way and leave your smart battery charger plugged in until it says your batteries are charged.
There's your best answer.
Old 06-05-2018, 07:33 PM
  #9  
Senior Member
 
Join Date: Jan 2011
Posts: 859
Received 120 Likes on 80 Posts
Default

Most alternators provide almost no charging current at idle, they need to by above 1600 ish rpm.
Running the boat home would have provided 30-75 amps hr charge rate depending on alternator current. Let's assume you have a 100aH battery, then 3 hrs of running at high rpm should charge the battery most of the way back if it was the only battery selected.

As others have said, put a Smart charger on it for 24 hrs and see if it brings it back. The battery could be bad.
Old 06-05-2018, 07:43 PM
  #10  
Senior Member
 
Join Date: Feb 2015
Posts: 2,389
Received 674 Likes on 357 Posts
Default

Originally Posted by Gatorinthenoog View Post
How long does it take to recharge a battery with the motor? Will it recharge if motor is just idling? Will I be safe if I go back out tomorrow and keep motor going while cruising and/fishing in hopes to recharge the battery? Do I need to use a battery charger at this point?

To answer your question more directly; If the battery is in good condition and you ran above ~1500 for more than 30 mins or so, the battery would not be fully charged but would more than likely start the engine or run your electronics. It will take considerably longer to restore the full charge, but I wouldn't hesitate to go back out tomorrow. Just start on the known good and switch to the other one after about 15mins or so.

Just for reference, even if you were set on both, the engine would still charge the battery because the fully charged battery would be trying to charge it too, pulling the whole system voltage down to a level where charging would occur.

The use of a battery charger over night would be a very beneficial step.
Old 06-06-2018, 03:36 AM
  #11  
Admirals Club Admiral's Club Member
Thread Starter
 
Join Date: Apr 2015
Posts: 148
Likes: 0
Received 80 Likes on 39 Posts
Default

Thanks for all the help guys! Sorry I didn’t know all the details about the battery...I’ll be looking into them. I plan to run it for a bit today to hopefully give it some charge and then see about putting a charger on it overnight.
Old 06-06-2018, 05:03 AM
  #12  
Senior Member
 
Join Date: Feb 2015
Posts: 3,465
Likes: 0
Received 133 Likes on 110 Posts
Default

Originally Posted by Gatorinthenoog View Post
Thanks for all the help guys! Sorry I didn’t know all the details about the battery...I’ll be looking into them. I plan to run it for a bit today to hopefully give it some charge and then see about putting a charger on it overnight.


Install an inexpensive voltmeter on the electrical system with display (https://www.ebay.com/itm/12V-24V-Wat...w-58jxusI5WJYg) in the console/dash so you can indirectly monitor the charging system output with motor running and charge state of your batteries with engine off (some GPS and sonar/fishfinder units have a voltmeter built in to the system menu that are a reasonable substitute). Voltage on electrical system while charging/running engine should range between 13.0 volts (+or - at idle -1500rpm) and 14.2 volts (+or- above 1500rpm); the actual voltage numbers will vary depending on your engine charging system and how much accessory load you put on the system (e.g. operating trim/tilt motor will decrease voltage significantly/temporarily, electronics, bilge pump, etc. decrease voltage somewhat less depending on current draw). You can monitor the charge state of a battery by moving the battery selector switch to the battery ("1" or "2") and reading the voltage with engine off for a few minutes (a battery that reads 12.4+ volts should start your engine). You should NEVER move the battery selector through- or to- the "OFF" position with the engine running since it can quickly ruin the charging system (no place for charge to go).

An important caveat for battery selector switch operation; the "BOTH" or "1+2" battery selector switch position combines the two batteries power which is a good feature for starting engine in an emergency (i.e. when one battery won't) but it also rapidly equalizes the charge state of both batteries. This means the "BOTH" position can quickly drain a good battery into a "dead" (or rarely defective) battery to the point where the engine electronic control module (ECM) will not operate and engine might turn over but not start. You can easily prevent this condition by checking voltage of each battery alone with the selector switch before attempting to start then selecting only the battery with highest charge state when cranking the engine and using "BOTH" or "1+2" position only if engine will not start. Similarly, running engine with selector switch in "BOTH" or "1+2" position will equalize both batteries' charge and charging. This is not a problem if both batteries are the same type and in relatively good condition and you plan to run a long distance with high charging output but I normally select which battery to charge based on starting requirements. I usually leave the selector switch on the battery previously used for starting for 15 minutes +or- to ensure charging has replaced power used for starting (ensures I can restart engine) then I either leave-, or move- selector switch on battery through the "BOTH" position to the battery I want to charge based on voltage readings taken prior to starting engine.

Many THT members recommend and prefer automatic charging relays or ACR (e.g. https://www.bluesea.com/products/cat...harging_Relays) which do all of the above, and more, automatically and allow you to combine batteries for starting in a pinch.

Last edited by LeakinLena; 06-06-2018 at 05:10 AM.
Old 06-06-2018, 05:00 PM
  #13  
Admirals Club Admiral's Club Member
Thread Starter
 
Join Date: Apr 2015
Posts: 148
Likes: 0
Received 80 Likes on 39 Posts
Default

LeakinLena...thank you for that information. I plan to get a volt monitor or meter to see if the battery gets charged with motor on.

went out today and kept motor running the whole time, approximately 4 hours, approx 1.5 hours of which was higher rpms. But went fishing again so had livewell on the whole time.

experienced the same thing. While on single battery, I lost power to the gps and radio and possibly livewell although the shrimp stayed alive. Switch to combined battery and everything works...when switch back to single battery everything works for another 30 min or so which makes me think the second battery is charging the first, and both are probably partially drained now.

I have read several posts where the livewell drains the battery...I’m hoping this is the case for me. Alternatively I suppose it could be the alternator or a bad battery.

so, right now my plan is as follows:

-charge both batteries with a battery charger
-monitor voltage on batteries to see if they are in fact being charged by the motor
​​​​​​-install a livewell timer

many have suggested an ACR...it seems I already have one:


How/when do I use this? Again, please pardon my ignorance.

Thanks again
Old 06-06-2018, 05:02 PM
  #14  
Admirals Club Admiral's Club Member
Thread Starter
 
Join Date: Apr 2015
Posts: 148
Likes: 0
Received 80 Likes on 39 Posts
Default

Also, I have 2 of these deep cycle batteries:


Old 06-06-2018, 05:04 PM
  #15  
Admirals Club Admiral's Club Member
Thread Starter
 
Join Date: Apr 2015
Posts: 148
Likes: 0
Received 80 Likes on 39 Posts
Default

And this is my switch (not sure it matters):


Old 06-06-2018, 06:07 PM
  #16  
Senior Member
 
Join Date: May 2013
Location: Eugene, OR
Posts: 435
Likes: 0
Received 76 Likes on 35 Posts
Default

IMO any discussion about a battery or batteries, especially for a newly bought but used boat, should START with a statement about battery age!! Most every battery is marked with it's date of purchase. Batteries have a finite lifespan, which may be shortened by misuse. In most, but not all cases, a battery less than 5 years old has probably (but not guaranteed) got some useful life, and more than 5 years old is highly suspect, if discharged and not easily/consistently charged again, to be at the end of it's lifespan. Of course, there is more accurate, specific testing that can identify a good or bad battery accurately but what is easier and what better place to start than LOOKING AT THE PURCHSE DATE!!

During this year's trip to FL, my starting battery on a boat that had been sitting in Miami for 11 months was on a smart charger up until my first morning outing and started the motor normally. With minimal draining electronics that day, the next morning, not put back on the charger overnight, the motor wouldn't start. I looked at the date. The battery was 8 years old!! As far as I was concerned.....'nuff said. I bought a new one without further testing.

KISS! We are 15 posts into a ? about charging problems of a used battery in a "new-to-poster" boat and NO MENTION OF THE AGE OF THE BATTERY, much less "complicated" issues of voltage or specific capacity testing? If that battery is 4 years old I would want all the fine testing. If it is 8 years old I would buy a new battery before I put any more time and effort into it.

However, now I see in post #14 the picture of the battery seems to indicate NO DATE marked, and that everything looks pretty new and pristine. But no one knew that until post #14. I don't think that negates the point of this post, and maybe the other battery is marked, or maybe the boat is only a year old. There may be other easy/quick ways to determine the battery age.

Last edited by peterpatricelli; 06-06-2018 at 06:22 PM.
Likes:
Old 06-06-2018, 06:32 PM
  #17  
Senior MemberCaptains Club Member
 
Join Date: Nov 2002
Location: Pensacola, Fl
Posts: 11,720
Likes: 0
Received 356 Likes on 273 Posts
Default

Most likely your "house" battery is bad at this point (if it wasn't already before being run down all of the way on your last two trips.) You may need a larger "house" battery bank. You need to buy digital volt meter (portable, such as in Ohms (resistance), Amps, (most only will do up to 10 amps, with a special circuit, & volts, measurement) and learn how to use it. You need to find out what the voltage was on the battery when it cost out

You need to find out how much current each item which you run, draws. Figure out how many amps/hour you need, and then how many hours. You want a battery (batteries) which are double the capacity (in amp hours) of what your load will be. I monitor my battery usage, not only by voltage, but also by amps used currently, and total amps used, plus state of charge. Try and not discharge the battery more than 50%. Generally 50% discharge, at a steady state (not drawing current, and at rest for an hour) the battery should register 12.2 volts. A fully charged battery will be between 12.6 and 12.8 volts. AGM batteries will tend to read a bit higher. Generally you will not fully charge the batteries just running on the outboard. For example the 90 hp Honda prior to 2007, only put out 17 amps--part of that was used by the motor. That would only give you about 12 amps to charge your house battery. Running the boat at enough speed to give the full 17 amps output, it would take 4 hours to recharge a 80 amp hour battery. (Group = size) A Group 24 battery would be 60 to 80 amp hours, A group 27 would be 80 to 105 amp hours, and a group 31 94 to 125 amp hours. I use group 31 batteries--even if they are a bit overkill for the engine start. Ideally you want both or all batteries to be the same size, the same capacity/brand, and the same age. (In your case you first need to see what size battery, and its rated capacity.

Load test the house battery. Any auto supply shop will do this for you.
Old 06-06-2018, 06:46 PM
  #18  
Senior Member
 
Join Date: Mar 2014
Posts: 770
Likes: 0
Received 70 Likes on 44 Posts
Default

First things first. Remove batteries and test them. Simple and effective when in doubt replace them both. Also swap that switch for a dual battery set up switch so you can decide which battery to use for what and when. Step 3 either buy an inboard charger or much cheaper and also effective get a trickle charger from your favorite chinese store aka “walmart”. Most battery issues out there are due to batteries being drained then recharged, at which point cells die and voila you have a bad battery. There fixed.
Likes:
Old 06-07-2018, 03:02 AM
  #19  
Senior Member
 
Join Date: Feb 2015
Posts: 3,465
Likes: 0
Received 133 Likes on 110 Posts
Default

Load test both batteries and read all literature associated with your relay and switch.

https://www.bluesea.com/products/761...2V_24V_DC_120A

https://www.bluesea.com/products/551...Battery_Switch

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information

Copyright © 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.