Dual Battery Charging

[lax boy]

I have 2 Everstart MAXX-29 12 volt batteries on my john boat which are connected in series. I need to get a battery charger and I assume I will need a 12 volt battery charger. Is my assumption correct, or will I need a 24 volt charger? Any recommendations on chargers is also appreciated.

Any feedback is appreciated.

 

[Silvertip]

Re: Dual Battery Charging

Many times people tell us they have two batteries wired in series when in fact they are in parallel. So lets first verify that you indeed have a 24 volt system for what I will assume is a 24 volt trolling motor. Must be a big john boat. If that is indeed the case, you need a 12 volt - dual output battery charger with one output connected to each battery. That, in effect, turns the charger into a 24V charger just like two batteries makes a 24V system. If you really have two batteries in parallel, then you still need a 12V charger but it only needs one output since the batteries are already paralleled and to the charger, it merely looks like a single giant battery. That charger should have a relatively high output however (10A or more) since that big battery will take twice as long to charge and a single battery.

 

[rndn]

Re: Dual Battery Charging

You'll need a 12 volt charger to charge one battery at a time. You could get a dual charger to charge them both at the same time.

 

[lax boy]

Re: Dual Battery Charging

Many times people tell us they have two batteries wired in series when in fact they are in parallel. So lets first verify that you indeed have a 24 volt system for what I will assume is a 24 volt trolling motor. Must be a big john boat. If that is indeed the case, you need a 12 volt - dual output battery charger with one output connected to each battery. That, in effect, turns the charger into a 24V charger just like two batteries makes a 24V system. If you really have two batteries in parallel, then you still need a 12V charger but it only needs one output since the batteries are already paralleled and to the charger, it merely looks like a single giant battery. That charger should have a relatively high output however (10A or more) since that big battery will take twice as long to charge and a single battery.

I have a 14ft john boat with a Minn Kota 50lb thrust Power Pro trolling motor. It appears that the motor is a 12v. I recently purchased this boat and the previous owner had 2 batteries on the boat. One battery is in a plastic container called a Power Caddy. There are wires inside the Caddy hooked directly to the battery in the Caddy. There are multiple connection ports on the Caddy (with associated wiring inside fed from the battery) to supply power to other devices as needed. There are 2 main posts on the outside of the Caddy for red and black wire connections. The 2nd battery is in a seperate compartment of the boat and has its red and black wires running and connected to the 2 exterior posts on the Caddy.
I suppose there isn't a need for both batteries on the boat since the only power needs are the motor and a fish finder.

 

[jtexas]

Re: Dual Battery Charging

With the 2nd battery (+) connected to the 1st battery(+) and (-) to (-) (assuming that the caddy red is + and black is -), you do indeed have a parallel connection.

In that configuration, you get the combined run time of both batteries, plus some bonus time (because you're discharging them more slowly, they can deliver more power).

The power used by the fishfinder is hardly even measureable, but if you want to fish all day, you might find that you need both batts for the T/M.

Your charging alternatives have been described above, but here's a summary:
1. one 12V charger hooked up to one of the batteries will charge them both, but it will take twice as long as charging a single battery.
2. two 12V chargers, one hooked up to each battery, but you'll have to disconnect the batteries from each other.
3. one two-bank 12V charger, one set of leads hooked up to each battery and they have to be disconnected.

To ensure that you get the longest life from your batteries, charge them as soon as you get home, and top them off every 2 or 3 weeks if you don't use 'em.

The best way to charge your batteries is with a "smart charger" that has a "float charge" or "maintain mode", which can be hooked up 24/7. This is *not* the same as a "trickle charge". Next best is a charger with auto-shut-off.

 

[lax boy]

Re: Dual Battery Charging

With the 2nd battery (+) connected to the 1st battery(+) and (-) to (-) (assuming that the caddy red is + and black is -), you do indeed have a parallel connection.

In that configuration, you get the combined run time of both batteries, plus some bonus time (because you're discharging them more slowly, they can deliver more power).

The power used by the fishfinder is hardly even measureable, but if you want to fish all day, you might find that you need both batts for the T/M.

Your charging alternatives have been described above, but here's a summary:
1. one 12V charger hooked up to one of the batteries will charge them both, but it will take twice as long as charging a single battery.
2. two 12V chargers, one hooked up to each battery, but you'll have to disconnect the batteries from each other.
3. one two-bank 12V charger, one set of leads hooked up to each battery and they have to be disconnected.

To ensure that you get the longest life from your batteries, charge them as soon as you get home, and top them off every 2 or 3 weeks if you don't use 'em.

The best way to charge your batteries is with a "smart charger" that has a "float charge" or "maintain mode", which can be hooked up 24/7. This is *not* the same as a "trickle charge". Next best is a charger with auto-shut-off.

Thanks for the feedback. I think I will just leave one battery on the boat and use the 2nd as a backup. The backup I will keep charged and use as needed. I also have a 15hp Evinrude on the back of the boat so losing a battery will take some load off the boat. I will be looking for a charger as you describe above. Thanks again.

 

[Silvertip]

Re: Dual Battery Charging

This is a "creative" 12 volt parallel system. We have no idea if this boat even has a gas engine on it so charging from an non-existent engine is not an issue. Regardless, he does not need a dual output charger. A single output charger of 10-12 amps will handle both batteries just fine. Yes, a dual output would work as well but again, it isn't necessary.