Sentry battery charger

[Sailor John]

Hi all,
This is my first post, and it comes 1 year after we bought our first Hatteras, a 38' double cabin with flybridgr. We are sooooo happy!
The on board Sentry battery charger does not seem to be putting out any juice. It is humming nicely, and the fuses all appear good, there is no power shown on the gauge, and no power across the terminals to the batteries. Now, this is an original charger, so maybe it's time has come, but I am just curious if anyone had any other ideas before I replace it with new. I appreciate your thoughts!
Sailor John

[captddis]

Depending on age there is either a toggle type breaker on the front or fuses inside. The later models had a red push button breaker on front. All of them were for DC output.

[Sailor John]

Hi, thanks for the info!
I am trying to attach a picture of the front of the Sentry charger unit for clarification. It's an oldie...
On the front are 2 AC fuses, both checked and good, one DC button that is perhaps a 'reset' button? and a yellow light.
In reviewing the boats wiring diagram I noticed and found 2 50amp bus bar fuses in the positive line from battery charger to the Guest battery switches. One was blown, and needs to be replaced. That will certainly help!
As well, I pulled the front of the charger off, and measured the current right at the lugs for the DC lines out. It was 14.7 amps on both sides. So the charger appears to be working, but power is not getting to the batteries. Replacing the blown fuse will help one side I'm sure. The other is still under investigation.
As well, the guage on the charger appears inoperative, unless this will only work when the battery receives power, not just when the unit sends power.
The investigation continues, but at least it appears that the old Sentry is operational on some level.
John

[tradewind]

Have the same boat last summer had the same problem. Behind the large battery switches there are large in line fuses, found one blown and coroded cleaned it up and and it started humming again. Hope this helps.

[Sailor John]

Thanks Tradewind,
I popped out the fuses by the battery switches, and one is indeed blown.
It's a holiday here in Canada, so I have to wait till tomorrow to get a couple of new fuses and see if that fixes the problem. Cross your fingers.
Yesterday I had put a portable charger on both battery banks. Today I did a load test on them. Both batteries appear in very good shape.
I hope the new fuse fixes everything, I will let you know!
Thanks again,
Sailor John

[Sailor John]

Just an update: I replaced both in line charger fuses (Located by the Battery switches) but I still seem to have no charge power to the batteries, and the charger needle doesn't move a bit.
This despite the fact that there is power at the battery wire lugs on the charger itself.
Anyone have any ideas why I don't have charge power to the batteries?
Charger is humming, fan is working, AC fuses are good, Battery (reset switch) is pushed in. Power at the lugs show over 14 volts.
I'm running out of ideas, but I am convinced the charger is operational and don't want to replace unless I have to.
Any thots?
John

[GJH]

Maybe Steve Pooler, an actual expert, will jump in here, but in the meantime do the following (I have a newer Sentry, BTW).

Turn the charger off by turning off the circuit breaker to it. Take a voltage reading at its DC output, and one at the batteries. If they vary by more than a few tenths of a volt, you may well have a wiring/connector issue. If they are close and the reading is something between around 12.8 and 13.9 volts, your charger may simply think the batteries are fully charged. They don't hum when charging, by the way, they make a fairly loud whirring noise.

If the voltage reading at the charger was somewhat less than 12.8, turn the charger circuit on. Does it come alive? Take the voltage readings and see what you get. Is it higher than the "off" readings? If so what is it? Take a clamp on amp meter to the charger output and see how many amps are being delivered to the batteries.

If the readings in step 1 were between 12.8 and 13.9, keep the charger off and put some loads on the batteries to bring the voltage down to say, 12.4. Then do step 2.

There are four likely outcomes here: a)the charger is fine, your batteries aren't running down enough to kick it in. b)you have a cabling issue c) the control board is out of calibration or bad. Recalibrating is a PITA, a new board costs about $300. d) the voltage sensing wires are either misconnected, or that circuit in the control board is bad.

That's my advice, probably worth what you paid for it. I don't know how much Sentrys changed since yours was made, in particular the "shut off when charged" function. Most authorized CruieAir techs are also trained in Sentry chargers, so you could try calling one and see. Ot post over on Steve's forum.

[Sailor John]

Hi, and thanks so much for the detail George.
I am headed back to the boat (sits on the hard) tomorrow and will bring your notes with me. I think you may be onto something re the batteries being full charged. When I checked them on Tuesday, they were showing 12.76 in each bank with no charge or draw on them.
I will borrow and put a load tester on one to see if that will kick in the charger.
These old Sentry feroresonant chargers are still well heralded in some circles, but the newer 'stepped' chargers seem to be the way of the world now. Do you have an opinion one way or the other?

Thanks George,
John

[TopHattandTails]

Reading your thread brought back some memories on my first real gremlin. I was blowing the ANL 50 amp fuse in the ships service left and right and with no regularity, until I found a bad diod in the battery charger. I did de-tune the charger and now I rarely add water to the batteries but once or twice a season and once while in the barn. They are part of my monthly maintenance check. If you have happy batteries, you have a happy boat. They are the epicenter of the boat.

In case your interested: <http://www.samsmarine.com/forums/showthread.php?10074-Blowing-ANL-50-Fuses-to-the-Batt-Charger.../page3>

[Sailor John]

Hi All!
Well who is the happiest dry land boater today? ME! With much thanks to all of you for your insights and assistance, I found the problem!
I did much measuring and poking and prodding and after an hour, I determined that the in-line FUSE holders were just plain dirty! I cleaned them up, (Emery cloth) and put in 2 new fuses just in case and the charger jumped back to life! After a few minutes, it topped up the batteries and shut off. I then put on as large a 12 volt draw as I could, (lights, fans etc) and drew the power down. Guess what! IT CAME ON! Wow! How cool is that?!
I am VERY grateful to all of you for your help!
One last question: Are the feroresonant chargers as good as the new stepped chargers? I am hearing the new chargers are much safer for battery life. Any thoughts?
My thanks again!
John