How do you charge a second battery

[zang8027]

My second battery is not charging so I need to know the proper way to charge the second battery. Do I just run a line from the one battery to the other or do I run a line to the alternator?

See my sig for engine info

 

[alldodge]

Re: How do you charge a second battery

If this is to add a second battery for additional storage capacity for the same circuit, run cables pos to pos and neg to neg with the same size cable as going to the first.

If this is to run a second battery for different service, house, trolling, etc please explain what you want to do?

 

[Silvertip]

Re: How do you charge a second battery

If you parallel rhe two batteries you end up with rhe essentislly one BIG battery but both will be chaged. Since they are not isolated you still end up with the possibility of two dead batteries. Google Dual Battery Switches or Automatic charge Relays which is what you need for a separate starting and house configuration.

 

[zang8027]

Re: How do you charge a second battery

I have two batteries. The one is charged so its hooked to the alternator. I have a second or which I think runs the depth finder and radio and must be starter too. The engine wouldn't turn because the battery was too low. I need a way to charge it with the alternator as well.

I think it was improperly hooked up to do this before which caused issues.

 

[Don S]

Re: How do you charge a second battery

There are numerous ways of hooking up second batteries. I see you have a 470 type motor, has it been converted to an alternator, or does it have the original charging system.
Next question, are you planning on using a battery switch to go from one battery to the next?

 

[alldodge]

Re: How do you charge a second battery

If you have only a depth finder and radio (no big amplifier) all you would really need is one large battery. For safety sake you could have the alternator wire run to the second battery through a battery switch with a Batt 1, Batt 2 and Both selector along with a built in field winding circuit switchr. This is accomplished by running the starter cable to the common connector and running additional cables from Batt 1 to the 1st Batt and another cable from Batt 2 to the 2nd Batt. Run the ALT wire to the common side of the switch and run the sense side of the ALT to the connector mocro switch on the two small connections. Get a 2 bank battery charger so when your at the dock or on a trailer you can plug it in and change both batteries.

A way to charge both batteries is to use a single bank battery charger and single alternator circuit and you also do not need the mico switch for the field winding circuit is use a 2 bank isolator. Run the ALT output and battery charger to the common on the isolator. Connect the outputs of the isolator 1 and 2 to each batt. If you use a 2 bank battery charger just connect them stright to the output side of the isolator or to each battery.

 

[zang8027]

Re: How do you charge a second battery

There are numerous ways of hooking up second batteries. I see you have a 470 type motor, has it been converted to an alternator, or does it have the original charging system.
Next question, are you planning on using a battery switch to go from one battery to the next?

It has an alternator that looks like it was put on aftermarket. And I am not sure what the battery switch would be for, as I just want both of them charged, but running the way it is now. I will figure out exactly what hooks to that battery tomorrow and let you know. Sadly the truck broke so its at the dock and I cant go out and look right away. After a day of running, It would not turn over. We measured 11v out of that battery, even when running. The other battery was fine. We ran a hot direct from the 11v battery to the coil + and it started right up. My guess is that it was too dead to go through the circuit .

I am going up to the boat today so I will check the alternator wiring and what is running to that second battery. I need them both running at same time, so no switching.

https://dl.dropboxusercontent.com/u/32161380/boat3.JPG

 

[zang8027]

Re: How do you charge a second battery

I checked that starboard battery that is not charging.

I got one large cable running to the other battery positive

I got one running to a terminal block at the dash which controls the radio and depth finder.

I got one running to the bilge through a fuse panel

I have no negative running to the engine block. There's one that runs to the bilge and one that runs to the dash. Should I run a large ground to the block ?

Also, I was told to run a line from the starter engine to the coil which would supply the coil with 12v bypassing the existing wires. Would that be ok?

 

[Don S]

Re: How do you charge a second battery

You must have the negative wires, or nothing works.
Here is how your system should be wired. Note the orange wire coming from the alternator to the starter solenoid. That is the main charge wire coming from the alternator and should be an 8 ga. wire. If not, fix it.

Also, I was told to run a line from the starter engine to the coil which would supply the coil with 12v bypassing the existing wires. Would that be ok?

That may already be done, usually from the slave relay on the 470 type engines.

What does that solenoid go to (bottom left of your picture)? Looks like it's going to the alternator?

 

[alldodge]

Re: How do you charge a second battery

First charge up both batteries seperately then load test them. I say do this first to make sure you have 2 good batteries. If one battery is weak or bad it will pull down the other.

You have to have at least one large ground coming from one of the batteries to the engine block; (See DonS pic) otherwise smaller ground wires would start smoking when the engine was trying to start. Either way, you need a large ground wire from the negative post to the engine block, and a large positive from the same battery positive post to the starter. Run one each additional large ground and positive wire from the first battery to the second. Connections should be made positive to positive and negative to negative. If there are anyother wires currently connected to anyone of the battery post leave them connected to their respective post in addition to the new cables.

Do NOT run a wire from the starter post to the coil. Doing this will keep the ignition turned on all the time and you will not be able to turn it off and stop the engine. The purple wire on the + side of the coil should turn on when you turn the key, if it does not we can assist to troubleshoot this also.

 

[zang8027]

Re: How do you charge a second battery

Thank you all for the help. I removed the connecting wire between the two batteries, as it had to have been draining my main battery. Makes NO sense why my boat would not start when that second battery was dieing. I grounded it against the engine block and removed the old selenoid in that picture. It was not hooked up to anything, just never removed it. See the chart I created below. That is how it is hooked up currently. The main battery should now not die, and I should not have a starting issue.

 

[Don S]

Re: How do you charge a second battery

The problem with your drawing, is there is no way to charge the accessory battery, only the starting battery.

You need to have either an ACR (automatic charge relay) or a battery isolator to charge both batteries.

Like this.