Replacing 1989 battery charger 38 Santego

[CptBacardi]

I bought a Promariner ProNauticP Series 1240P 3 bank charger to replace what I guess is the original old faded blue charging unit. I’m not sure if the original is a single bank that connects to a bus bar or something? Haven’t looked real close yet. I just wanted to drop in here and see if y’all can offer any advice and or gotchas I should be considering before going down to the boat. For example, I have a huge 8D battery on port and one on starboard and a regular starting battery for the genset, but I have no idea how they are wired. Does the genset battery usually get a charge from a charger? Are the 8D’s separate or connected? Any and all advice appreciated. Thank you.

[Viper]

Good choice in chargers. If it's like most applications, each 8D battery is a separate bank, so 2 banks if that's all the batteries you have excluding the genny battery. Typically which bank systems feed off of is controlled by a battery selector switch (1/2/ALL/OFF). If that's the case for you, the output legs of the changer can go to the source side of the selector switch for each bank after they go through a fuse or breaker. Power and switch position management is key in this type of system. Though commonly exercised, the ALL position should rarely be used as doing so is the source of many battery problems.

Whether the genny battery is charged by an outside source or not really depends on the application, some are, some aren't. If you only have to banks to charge (2 x 8Ds) then you can use the third charge output of the ProNauticP to maintain the genny battery. Having said that, if you use the genny on a regular basis as you must to maintain longevity, it should maintain its battery on its own.

The charger install is pretty straight forward but you must read the instructions to ensure a proper and safe installation. Check your charge circuit run lengths both positive and negative to determine the proper gauge wire to go with. Choose the longest run from the charger to the furthest battery and use that to determine the gauge you need and use that for all of the charge wiring. Remember that the ProNauticP can deliver all of it's max output, 40 amps in your case to any one of the charge legs so each charge wire must be able to carry full rated load unlike cheaper units. You also need to check that the gauge required is what you currently have on board otherwise you'll have to replace your wiring. Even if your old charger is a 40 amp unit, don't assume your wiring is good enough as the old unit may be of an out dividing type where each bank may only be a maximum fraction of the total such as 10/10/20 amp in a 3 bank unit. If that was the case, they would have installed smaller gauge wire which won't do for your new charger.

Your old unit will likely also not have the chassis ground wire which is a must on newer units.

Several members here have installed chargers so there's a lot of knowledge if you need help with your install. PS; use only marine wiring and connectors, and it's a good idea to use adhesive lined shrink tubing for a proper installation.

Good luck and keep us posted.

[CptBacardi]

Thanks Viper! I do have a 1/2/ALL/OFF selector under the stairs. It makes sense what you mean by running 2 output banks to the respective source sides of that. I assume in doing so that no matter where the selector is set, the charger can still charge. Another thought is, I’ve only ever had that switch set to ALL. If I was to select 1 or 2, would both engines still be able to start? Guess I’m confused about the output side of the switch.

[Viper]

Where ever you set the switch to is where all power to the house loads and engines will come from. That's the inherent problem with that type of system as there is no way of maintaining isolation of deep cycle and starting loads unless you keep switching the selector switch. Most also leave the switch in the ALL position which is a no no as it defeats the purpose of separate banks both for load types and charging. What you have to ensure is that there is a way for each bank to be charged by an engine no matter where the selector is set to. The best way to do that irrespective of selector switch position is to divert the alternator charge wire which is commonly done in isolator and ACR installations.

[CptBacardi]

So the batteries will charge regardless of where the switch is right? Are the alternator charge wires going to the same locations on the source side of the selector switch as the battery charger?

[Viper]

Unless something has been changed, the alternator output charges the battery that starts the engine. The hook up is on the engine, usually to the starter as that's the main connection at the engine end not the selector switch unless as I mentioned earlier it has been rerouted to accommodate a better charging design. This is engine charging we're talking about which differs from the charger you'll be installing but just as important none the less for an efficient carefree overall charging system.

[CptBacardi]

I’ve been trying to look at diagrams and where I get confused is why there is only 1 selector switch. The Perki diagrams I find use 2 switches when there are 2 engines and 2 batteries. Is it possible the “com” on the single switch is feeding both starters?

[CptBacardi]

Since I have one switch, would this be running 2 starters?

F8770A77-CFC0-4D74-B04F-EE08723C7D11.jpeg

[bud37]

Source of the post Since I have one switch, would this be running 2 starters?

F8770A77-CFC0-4D74-B04F-EE08723C7D11.jpeg

IF your boat is wired correctly both engines will start from either #1,#2 or all positions on the switch. The switch itself just directs which battery or battery bank you draw from or direct power to. You can discover which is which with a tester.

Check your switch to see if it is a make before break type..( sometimes written on it or will be in your manual as to how to use it )......in other words it will never completely disconnect from one position before it makes the next. This allows you to switch thru the battery positions while the engines are running . NEVER switch thru the off position or turn the switch to off while the engines are running it will deadhead the alternators and may cause damage.

[Viper]

Most switches of the last couple of decades will be "make before break" which makes it safe for switching from one bank to another. The only message most have now is "Stop engines before switching OFF" as the make before break does nothing to protect the alternators when going to the OFF position with the engines running. There are however battery switches with a "Field Disconnect" function. In this type, the field wire from the alternator is routed through the switch. Should you accidentally turn the switch off with the engines running, the switch shuts down the alternator output just before the OFF position, to protect the diodes. Of course these can only be used with alternators that use an external regulator either attached or separate from the alternator. BTW, the battery switch in your diagram above is this type of switch, the F1 and F2 on the switch are for field connections.

Source of the post.....Is it possible the “com” on the single switch is feeding both starters?

YES, and the power for all your house loads. Which battery the power comes from (port or starboard, depends on which position you have the switch set to; 1 or 2 or ALL/BOTH. BTW, if you don't already know and it's not marked anywhere, it's a good idea to know which battery, port or starboard is number 1 and which is number 2. It's easy to find out. Let us know if it's not marked and we can walk you through the process.