Boat electrics/battery questions

[Harryp]

Hi all,

I have a two battery system in my boat. One starts the engine the other runs the electronics. The guy I bought the boat of told me he believed BOTH batteries were wired for charging while the engine is running.

I've been running the boat six or seven weeks now and last night the battery running the ff etc had no power. I'm concerned that it might not be charging and has taken this long to run out of juice(I kept the electronic use to a minimum). Another possible cause is that the terminals had vibrated slightly loose so this could have caused the problem, I'll know when I reconnect it later after charging. No matter what though I've realised that I don't want to have a problem when I'm out in the Irish Sea with the kids. Therefore I've a couple of questions.

How can I check if it is being charged?

How can I check that the other battery is charging as well?

Have you any tips or ideas you'd like to share about electrics or wiring?

Are there any experts around the Bangor area?

Any websites you can recommend?

Finally, if there are any books for boat electrics and batteries that you've used and think suitable for someone who is a complete novice please let me know.

I know I' asking a lot but this is the place to do it!

Cheers

[Conor H]

Harry,
I'm far from an expert but would guess that battery for the ignition would charge from the engine when in use , but the battery for the electronics would need recharging before each trip unless it was somehow linked to the ignition. (hope that makes sense)
I have a 2 battery set up and I charge the electronics battery before every trip, while the ignition battery doesn't get charged, though I do start the engine at the house before leaving on every trip to ensure it is charged.
Again at a guess, if both your batteries are charging from the engine when in use, your electronics battery may not be getting a full charge. I do know from personal experience that leaving all your electronics on, uneccesarily, when fishing , can drain the battery fairly quickly.
Until you find the source of your problem, I'd ensure both batteries were charged fully before setting out. Better to err on the side of caution, even if it costs a few quid in electricity and increases the size of your carbon footprint !! Minn Kota have started selling solar leisure battery chargers - it's just a small solar panel which links by normal terminals to an ordinary leisure battery - leave it out in daylight when the battery is not in use and you've a fully charged battery come launch time !! Go green !!

[Mohawk]

How can I check if it is being charged?

How can I check that the other battery is charging as well?

Very simple, beg borrow buy or steal a dc voltmeter or multimeter, select the 20 volt dc setting and measure both batteries while the engine is stopped. It should read 13.8 volts or less. Then just start and rev the engine both batteries will now read well over 14 volts.

Don't try to wire the two to charge if they are not both charging you will probably damage your alternator and batteries and possibly more of your electrics as you will require a charge split diode and also the capacity of the alternator will need to be capable or supplying enough charge current for two batteries.

This damage could cost you serious money to repair!!!!!!!!!!


Jim

[jw]

some fish finders/gps such as lowrance have an option to show the voltage on screen, which will answer your question and is generally a useful thing to keep an eye on occasionally

[Mohawk]

some fish finders/gps such as lowrance have an option to show the voltage on screen, which will answer your question and is generally a useful thing to keep an eye on occasionally

That will not work in this situation as it will not answer your questions for example.

1/ Are BOTH batteries wired to the charge circuit.

&

2/ Are both batteries isolated from each other.

&

3/ It will only tell you the voltage of the battery that the particular unit is running off and with a long run of cable the reading will not be accurate due to the voltage drop or "losses" within the cable


If in any doubt before you try to rewire anything consult a competent marine auto electrician, a fire on your boat is the last thing you want especially while out at sea!!


Jim

[Harryp]

Hi all,

Thanks for the prompt replies.

I think one of the problems might be that I didn't switch my other battery on until I was out fishing. This probably meant it was isolated and therefore not charging as the engine wasn't running. I think the answer is to turn the switch to both batteries when motoring out to fish. Obvious I know but I didn't think of it until I started looking at it!

The idea of getting someone qualified is a good one as well. I'd like to find a boat electrician in the Bangor / North Down area. Any ideas or recommendations?

Thanks again for all the advice you've given me.

[jw]

some fish finders/gps such as lowrance have an option to show the voltage on screen, which will answer your question and is generally a useful thing to keep an eye on occasionally

That will not work in this situation as it will not answer your questions for example.
1/ Are BOTH batteries wired to the charge circuit.
&
2/ Are both batteries isolated from each other.
&
3/ It will only tell you the voltage of the battery that the particular unit is running off and with a long run of cable the reading will not be accurate due to the voltage drop or "losses" within the cable

If in any doubt before you try to rewire anything consult a competent marine auto electrician, a fire on your boat is the last thing you want especially while out at sea!!
Jim

it will work for him. His question is if the battery that's running the electronics is charging or not. There will be some voltage drop true, so it might read 14.3 volts versus 14.5 at the battery for example, but it will tell him if the battery running the fishfinder is being charged or not. The people who build the fishfinder and write the manual must know something about marine electonics no?

[Mohawk]

some fish finders/gps such as lowrance have an option to show the voltage on screen, which will answer your question and is generally a useful thing to keep an eye on occasionally

That will not work in this situation as it will not answer your questions for example.
1/ Are BOTH batteries wired to the charge circuit.
&
2/ Are both batteries isolated from each other.
&
3/ It will only tell you the voltage of the battery that the particular unit is running off and with a long run of cable the reading will not be accurate due to the voltage drop or "losses" within the cable

If in any doubt before you try to rewire anything consult a competent marine auto electrician, a fire on your boat is the last thing you want especially while out at sea!!
Jim

it will work for him. His question is if the battery that's running the electronics is charging or not. There will be some voltage drop true, so it might read 14.3 volts versus 14.5 at the battery for example, but it will tell him if the battery running the fishfinder is being charged or not. The people who build the fishfinder and write the manual must know something about marine electonics no?

Yeah!!

But when his boat goes up in flames at sea, I promise I will not reply with I told you so!

Jim

[andydee]

HI Harryp, for any electrical work try Billy Finlay out the back of what used to be the Castle Arms

Andy

[ROADRUNNER]

Boys Boys Boys

There are a lot of different areas where the problem could be.

1) Is there a split charging system in place ?

2) how old are the batteries (over two years old dogie )

3) how are the batteries wired up ? (loose connection wouldn't help)

4) what size is the outboard ? what is the output of the alternator ?

5) what is the general state of the wiring on board ?

As Mohawk said you really need to get a proper marine engineer to have a look at your boat.


After all Safety is Paramount


Cheers Danny