Batteries Not Charging

[LeifErickson]

Hello, cruisers. I've searched for information on my electrical difugilty but been unable to find the right action other than removing the alternator to have it spun, which I did and it checks out ok.
I have a Yanmar 3GM 20HP with a 100 amp alternator (modified balmar... original for engine is 35 amp). This is in a 1983 Hunter 34 I just acquired.
I drained the batteries down to 10v running the inverter longer than I should have. I was turning the motor on for several hours to keep the charge up.
Since this happened, I've been able to jump-start the engine using two batteries looped to get the required 840 cc amps. Once the engine is running again, I remove the jumper batteries without disrupting the existing connections for the starter battery. Rotary switch is on starter battery. I take the voltmeter to the battery and the reading is the same as the alternator. Rather than increase in voltage, I see it gradually decreasing.
I believe the balmar regulator gave me a reading of over 14v when I took a reading. There was a green light on it also.
So... alternator was not fried by the jump. regulator light is on, so it is powered and reading 14v, alternator voltage reads same as the battery voltage. voltage is decreasing. Without dissecting the electrical on this, have any of you experienced anything like this or can show me the light?
Thank you very much for your input.

[DeepFrz]

I did a search on "Batteries not charging" and came up with 225 threads that should give you some idea of the information we need in order to help you. Or they may even give you the information you need to solve the problem.

[LeifErickson]

Thanks. I've already searched the threads. Besides going through the wires, dissecting my way to draw up a diagram, I'd really like input from someone that can visualize my dilemma and point me in the right direction.

[S/V_Surya]

So you have a rotary switch between alternator and battery. I had a switch that would not work at all and took it apart to find I was not making good contact. I think you are see proper voltage but due to poor contact (dirty) amps are not getting to battery. Volts are like water pressure and amps are like amount of water flow.

[btrayfors]

Don't have enough info on all your connections to be definitive about this.

However, it sounds as if your start battery may be shot. The regulator apparently thinks it's charged -- which it well may be, i.e., charged but no capacity left -- so it cuts down on the charging voltage from 14.4 to 13.2 or so.

As this is a new boat for you, you need to tackle this problem piece-by-piece, and in the process get familiar with the entire system. Diagram out the wiring, so you know what the switches do, i.e., what's hooked to what. Assuming the larger alternator was accompanied by an external regulator, it's probably set up to charge the house batteries.

Again, need more info to be sure, but I'd start with a close examination of the entire setup, diagrams, removing all connections and cleaning them and checking. Also, it could save you a lot of time if you could get a good check on the condition of the batteries.

Bill

[LeifErickson]

Thanks for the input, guys. I'm taking a battery tester to see if the starter battery is still good. It is a no maintenance 4d lead acid, as is the house battery. I will also clean up the rotary to make sure that is providing good flow. I will also follow the current from the battery wires to make sure connections are good.
Question: If battery tester indicates the 4ds are still ok, would taking a battery charger and generator to the boat be worthwhile or should I bite the bullet and get two 4ds (providing the wiring labyrinth has been solved)? Thanks!

[soundman67]

So it looks like the alternator is putting out a charge. Lets have a look at the batteries. Wet cells can be checked with specific gravity meter. You may have one low cell in a battery that could be ruining that battery. could be a short inside one cell that wont show until large amps are pulled. Metering each battery after its separated from the chain might narrow down your search as well.

Doug

[btrayfors]

Unfortunately, there's no really good way to test a battery's capacity (i.e., its ability to store and deliver energy) except by a load test or a sophisticated battery analyzer like the Midtronics line ($600 plus).

Note that the state of charge (SOC) of a battery does NOT indicate how much capacity it has remaining. You may have a fully charged battery which can't deliver enough energy to start the engine. Happens all the time in cars as well as in boats.

After sorting out the wiring so you understand the system, I believe I'd opt for new batteries so that you know what you've got to begin with. The choice of batteries should depend on how they're wired and what they're used for. Ideally, you'd have a large(r) house bank and a separate starting battery, the latter charged via a little device like an EchoCharge, and with all onboard charging sources (alternator, shore power battery charger, solar, etc.) connected to the house bank.

But, without understanding fully what you've got now, the size of your boat and it's electrical demands, the type of cruising/boating you plan on doing, etc.. it's hard to suggest what might be best and/or most economical.

Bill

[LeifErickson]

Going back on board (it's chilly out there) to draw up the wiring diagram and clean connections. Checking on battery warranty to replace and start fresh, as suggested. Tks for your input Bill, Doug, Surya and Deepfrz.

[S/V_Surya]

Leif, Please when you find your problem let us know what it was.

[LeifErickson]

ok. i bit the bullet and dropped a new house and new starter battery yesterday. I took some readings with the voltmeter and the alternator seems to be sending over 12.3v back to the battery. I checked both batteries. Still need to clean the terminals and do a diagram. The solar panels and inverter need to be hooked up too, but needed to get power back for some tunes... I mean, for the anchor light. The batteries I took out were put on a charger but didn't seem to be holding a charge. This way, I know I'll have decent batteries for a couple of years with proper maintenance.

[LeifErickson]

there was excessive corrosion on the amperage and engine hour guage. inline fluse to the alternator was disconnected. working to get that repaired. thanks again for your help, guys.

[btrayfors]

Leif,

You said "excessive corrosion on the amperage and engine hour guage". I assume (hope) that with a 100A alternator the output wire doesn't run directly to an "amerage guage", i.e., one of the older type guages. Rather, that you have a shunt in the circuit with small wires going to the ammeter. If not, this is something to upgrade.

Also, which "inline fuse to the alternator" was disconnected? The field wire? The main power output wire?

Good luck. Persistence will get you there :-)

Bill