Only one battery of two on starboard side charges

"Hello to all and a huge thank

"Hello to all and a huge thanks for all the helpful info from the members on this site, it has been a great help so far.

I’m a new member and new boat owner, 1985 SRV255 Sea Ray, twin 170’s. “inherited” this boat this spring from the in-laws and have been sorting out a multitude of issues and will post those experiences later to hopefully help others

This boat had dual batteries as delivered on starboard engine. At some point the battery switch was upgraded to a Guest (1-Both-2 model, but don’t know if it has the field isolation feature. Both engines still have stator charging system/water cooled VR.

Problem is the one of these starboard batteries does not charge, when the battery switch is on “2” ship’s voltmeter reads 14 V and a DVM confirms appropriate charging voltage. When on “Both” voltage drops to about 12.5 and when on “1” voltage drops to 10 after engine start and over course of running (15-20 min @ +2500 rpm) rises to 12 and never gets above 12. Below 2500 rpm voltage drops to 11-12 and at idle 10-11. Battery connections are clean and tight.

I have been unable to find an unintentional load on this battery. Initially suspected that this 3 year old battery was bad as the disconnected voltage was just above 12 so it was replaced, other battery sits at 12.6-12.8V. The problem battery has an 18” ground cable to the negative post of the “good” charging battery. The newly replaced battery will readily accept a charge from a battery charger and did not solve the issue, but I don’t like 3-4 year old batteries anyway. All cables are the crimped tinned copper, not “lead” style.

I know the previous owner would switch batteries while underway and understand this is an issue with an alternator, but is it an issue with the stator charging system?

This is a new problem in the past month, and have been on the water since March, I suspect the 18” negative cable is bad, internally corroded, but wanted to ask if this might also be a sign of the voltage regulator going bad or where else I should be hunting for a cure?

An alternator conversion is in the plan just didn’t want to do it right away due to host of other issues.

Thanks in advance."

whatever is connected to #1 is

whatever is connected to #1 is not charging. you should have a switch for each engine. don't know whhat you got.

"I would use the DVM and test

"I would use the DVM and test the input and output voltages of each regulator. AC in, DC out. You could put $400 in a new VR or change both outboard style alternators to single wire self contained alternators for the same price. Search recent posts to see how it's done. Very simple change process. Then you can get rid of the battery switch unless you want a third battery for accessories like a booming stereo or 12 volt appliances, i.e., coffe pot, blender for margaritas, TV with DVD, refrigerator. Then I would hook the switch to one engine and the engine and accessory battery which I would make a deep cycle battery."

"Thanks for the replies, chasi

"Thanks for the replies, chasing sparks is hard, I would rather tile floors. Please let me clarify on set up. Port engine with stator charging has its own battery and does not support the ships electrical systems, charges ok at 13-14 volts above 1200 rpm, confirmed with DVM. Port system is not connected to starboard.

Starboard is the problem, has original stator charging system like port engine. Starboard engine has two batteries and ships electrical is on this part of the loom, thus it is as you suggest Guy, one for cranking and one for house. Currently both are cranking styles. Starboard #1 battery is new, when Starboard #2 goes it will become a deep cycle.

Battery selector switch only is for the starboard two batteries. When battery switch is on #2 the number two battery receives 13-14 volts and appropriate charging current. When battery switch is on “both” volts fall to ~12.5. When battery switch is on #1 this same charging system now only shows 10-12 volts and #1 battery slowly discharges as one would expect at that voltage. These two batteries are on a common ground plane. Voltages confirmed with DVM, ship’s voltmeters are within a half a volt of the DVM. The starboard engine stator output is supposed to charge both of the starboard batteries and is not connected to the port battery.

Shore power circuits run AC outlets, stove and fridge, ship does not have a shore power AC/DC battery charger nor is there an inverter for the ships DC bus to run these accessories.

Just looking for a license to hunt in other locations from someone in case wholesale battery cable replacement doesn’t work, terminals are clean and tight.

It would seem to be a cable, loom or battery switch issue since the starboard stator is charging at least one of the batteries on starboard side.

Or does anyone feel that this is an impending VR failure?

I’ll also post solution once found.

Thanks"

"Change the batteries from 1 t

"Change the batteries from 1 to 2 and 2 to 1. If the problem follows the battery; replace it. If it remains on #1, disconnect the selector switch and perform an ohm test; one of the contacts is burned or heavily corroded or there is a built in isolator that has gone south. Replace it."

"You'd better pull and che

"You'd better pull and check that battery out. I have a feeling it's shot and, if you keep trying to charge it, you might wreck your alternator.

Jeff"

"Verdict: (2 weeks since

"Verdict: (2 weeks since I could get back to the boat)

Thanks for the posts, Guy you were correct, bad battery selector switch. Switch showed increased resistance in “1 and Both”. Turns out switch was original equipment to the boat, 1985 Guest.

After cutting the switch apart, the center plastic column that rotated the contactor was cracked and the “problem battery pole” inside the switch was at a slightly different height so when the selection was made to “Both” or “1” (poor charging battery) there was poor physical contact in that position. No corrosion was evident (fresh water boat).

New switch, problem solved.

Thanks again everyone, hope this helps someone else out in the future.

Mark"