Batteries not charging off the alternator

jaysweet

jaysweet

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Jun 25, 2004
661
Hunter 306 Pasadena MD
I'm in the middle of a trip, and it seems like my batteries are not charging from running the engine. Left a marina (on shore power), and after motoring for 6 hours, anchored and noticed that my house bank was at 88% (per my Balmar monitor). This morning, it was at 80%. I started the engine and it seems like it's not charging.

In the past, I noticed it does this when the key is turned to "off" on the panel, but that's not the problem. Then only wild card here is that I did just bypass the red and white starting circuit wires. Hard to see how that relates, but...

I'm headed for a marina as my next stop, so hopefully can charge on shore power there, but I'd like to figure this out soonest. Thanks for your ideas.
 
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dlochner

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Jan 11, 2014
14,182
Sabre 362 113 Fair Haven, NY
Jay, how big is your house bank? What kind of anchor light did you use, LED or incandescent? How many amphours were consumed?

The Balmar SOC gauges are not accurate out of the box. They take several charge/discharge cycles to learn the battery. Over time they become more accurate. How new is the gauge?
 
Davidasailor26

Davidasailor26

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May 17, 2004
6,223
Beneteau Oceanis 37 Havre de Grace
Check the voltage at the terminals with a multimeter when the engine is running. It should be somewhere above 14V. If it’s still in the 12’s then the alternator isn’t putting any charge into the battery, for some reason. At least that initial check will eliminate the Balmar gauge as a variable.
 
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jaysweet

jaysweet

.
Jun 25, 2004
661
Hunter 306 Pasadena MD
First, I’ll apologize in advance if I don’t answer quickly or completely. I’m singlehanded and just got underway.

The house bank is 230 AH, so running it down to 88% yesterday is entirely consistent with not changing. I don’t have my power consumption at hand. But it’s instruments, a small fridge, and yesterday, I had running lights on all day. At the moment, the Balmar is showing 1.7 to 2 amps usage.

Both the Balmar and a cheap digital standalone meter are reading 12.4 volts, so it’s all consistent with the alternator not changing the battery
 
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jaysweet

jaysweet

.
Jun 25, 2004
661
Hunter 306 Pasadena MD
Actually, this is looking like I haven't been charging at all since I left Saturday morning. I ran 8 hours saturday and 6 yesterday. So 14 hours times 2 amps = 28 AH, and 28/230 =0.122. This would take me down to 88%. I was on marina shore power Saturday night, but I didn't bother to check the battery state. Anyway, I just hope the shore power charger works tonight. I'm headed to a marina in Cambridge.
 
jaysweet

jaysweet

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Jun 25, 2004
661
Hunter 306 Pasadena MD
dlochner said:
Jay, how big is your house bank? What kind of anchor light did you use, LED or incandescent? How many amphours were consumed?

The Balmar SOC gauges are not accurate out of the box. They take several charge/discharge cycles to learn the battery. Over time they become more accurate. How new is the gauge?
Click to expand
The Balmar is several years old now, but I thought only the SOH took a while to calibrate? Although that's related to SOC, I suppose. I haven't really run it down to 50% as Maine Sail suggested you should do, but it's been down to 70. Maybe today will be a good " unintentional" chance to calibrate the meter... :)
 
jssailem

jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
24,774
CAL 35 Cruiser #21 moored EVERETT WA
I am going to assume that:
  1. The alternator shaft is spinning, being driven by a properly tensioned belt.
  2. The wiring from the alternator is properly configured with the positive lead to the battery or a charging buss and the negative lead to the engine ground.
  3. That you have correctly connected the Alternateor terminals.
    1. Three Terminals Work Together
      Although each terminal has a distinct function, the alternator relies on all three working in perfect coordination:
      ·The field terminal energizes the rotor.
      ·The B+ terminal delivers generated power to the battery.
      ·The sense terminal feeds voltage information back to the regulator.

      Failure in any one of these circuits—open wires, corrosion, poor grounding—can cause charging problems ranging from mild voltage instability to complete charging failure.
  4. If you have installed an Alternator Off Switch, so that you can safely work on the alternator, you have returned the switch to “ON”.
  5. All of the connections from the alternator to the battery have been checked. All are clean and properly torqued - no loose wiring.
If all of these are affirmed, then I would take the alternator to an auto Electric shop and have them run a test on the unit. Certainly before I opened up the unit looking for diodes.
 
jaysweet

jaysweet

.
Jun 25, 2004
661
Hunter 306 Pasadena MD
What I was remembering, John was some sort of common warning, something along the lines of "if you turn the battery selector switch to off when the engine is running, you'll blow the diode". I didn't do this, but that's the diode I was referring to. My vague memory was "if it blows, you can't charge". I have the stock alternator that came with my 2GM20F, and I haven't done much to change the setup,

To answer your questions: the belt is on, the alternator pulley is turning, and I don't think I hosed up the wiring when I re-did the starting circuit. I did cause a big spark at one point, b/c I removed the large wire from the battery to the B+ without turning off the battery switch. So I probably fried something in the alternator. In general, I wouldn't say "there are no coincidences", but most of the time when something odd happens and it's followed by something else odd, the first thing is related to the second.
 
D

dlochner

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Jan 11, 2014
14,182
Sabre 362 113 Fair Haven, NY
jaysweet said:
The Balmar is several years old now, but I thought only the SOH took a while to calibrate? Although that's related to SOC, I suppose. I haven't really run it down to 50% as Maine Sail suggested you should do, but it's been down to 70. Maybe today will be a good " unintentional" chance to calibrate the meter... :)
Click to expand
If the battery was disconnected it has to recalibrate when it is reconnected.

jaysweet said:
Isn’t there some diode on the alternator that typically can get blown and stop the charging?
Click to expand
There are diodes and rectifiers which convert the AC generated by the alternator to DC. If the alternator output is cut off while the alternator is running there will be an short increase in voltage that will damage them.

There should be a fuse between the alternator output and the battery. Any chance the fuse has blown? Are all the connection clean and tight?
 
Davidasailor26

Davidasailor26

.
May 17, 2004
6,223
Beneteau Oceanis 37 Havre de Grace
jaysweet said:
hat I was remembering, John was some sort of common warning, something along the lines of "if you turn the battery selector switch to off when the engine is running, you'll blow the diode". I didn't do this, but that's the diode I was referring to. My vague memory was "if it blows, you can't charge".
Click to expand
Yes, you remember that correctly. If the alternator is putting out significant charge current, and the destination of that current is removed (either by turning a battery switch off or by disconnecting a battery cable), then the voltage inside the alternator will surge, potentially blowing out the rectifier diodes and preventing the alternator from charging anymore.
jaysweet said:
I did cause a big spark at one point, b/c I removed the large wire from the battery to the B+ without turning off the battery switch.
Click to expand
Disconnecting that cable without turning off the switch should, in itself, not cause any problem. Disconnecting the cable is just like turning off the switch. That doesn’t really explain the spark though. A spark suggests current was flowing. I’m assuming the engine was off at the time? If the engine was running then it could cause the voltage spike mentioned above.
 
jaysweet

jaysweet

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Jun 25, 2004
661
Hunter 306 Pasadena MD
dlochner said:
here are diodes and rectifiers which convert the AC generated by the alternator to DC. If the alternator output is cut off while the alternator is running there will be an short increase in voltage that will damage them.

There should be a fuse between the alternator output and the battery. Any chance the fuse has blown? Are all the connection clean and tight?
Click to expand
The alternator wasn't running when I made the spark, so that wasn't the cause.

Your second point is interesting, though. There were 2 small red wires on the B+ lug of the starter, plus the huge one from the battery. I disconnected the one that had the inline fuse maybe 8" away, and replaced it with my new red wire that I led to the engine panel. Is it possible that the one I disconnected is the wire that charges the batteries? It seems too small. This is all making me feel like a complete dumb@#$, but whatever. The engine starts perfectly now, but the batteries aren't charging.
 
jaysweet

jaysweet

.
Jun 25, 2004
661
Hunter 306 Pasadena MD
I'm guessing that the 2 small red wires on the starter B+ were: 1 = power to the panel (I bypassed this one), and 2 = power to charge the batteries, maybe? Or possibly something to control the charging? can anyone confirm/refute this, please?
 
jssailem

jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
24,774
CAL 35 Cruiser #21 moored EVERETT WA
jaysweet said:
“you'll blow the diode”

"if it blows, you can't charge"
Click to expand
I know. That sounds plausible. While it can happen, the diodes are not like egg shells breaking when you look at them funny.
They may be the problem, but I would eliminate all the other, simpler possibilities.

I try to look at challenges as having no complexity. The OCCAMS Razor philosophy.

You should be able to tell if the alternator is putting out by putting the DMV positive lead to the +B terminal then touching the Negative lead to ground. This can be done at the battery first, then at the alternator.
 
jaysweet

jaysweet

.
Jun 25, 2004
661
Hunter 306 Pasadena MD
I appreciate all the help, guys. Most of this is going to have to wait until I'm tied up, b/c I'm already multitasking at my max with running the boat, navigating, not running into crabbers, and typing replies.

If I can charge off of shore power, my immediate problems will be solved, and I can solve the rest when i get the boat back home on Wednesday.
 
jssailem

jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
24,774
CAL 35 Cruiser #21 moored EVERETT WA
Not sure where you are, but Windy is showing nice sailing conditions on the Chesapeake for the next 3-4 days.
Lucky you.:biggrin:
 
jaysweet

jaysweet

.
Jun 25, 2004
661
Hunter 306 Pasadena MD
jssailem said:
Not sure where you are, but Windy is showing nice sailing conditions on the Chesapeake for the next 3-4 days.
Lucky you.:biggrin:
Click to expand
Thanks, John! I think I already paid for it with 2 solid days of non-stop drizzle, rain and mist. Finally seeing some sun today
 
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D

dlochner

.
Jan 11, 2014
14,182
Sabre 362 113 Fair Haven, NY
jaysweet said:
I'm guessing that the 2 small red wires on the starter B+ were: 1 = power to the panel (I bypassed this one), and 2 = power to charge the batteries, maybe? Or possibly something to control the charging? can anyone confirm/refute this, please?
Click to expand
Where does the cable from the starter go? Directly to the start battery or to the 1-2-Both Switch? Where does the cable from the alternator go? Directly to the Battery or to the Starter? or to the 1-2-Both switch?

The smaller wires are probably not carrying the charging current, unless they are the same size as the wire coming off the alternator. The red wire you disconnected and left disconnected, where is the other end? On the alternator maybe?
 
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