Same old charger problem

[John]

A month or so ago, I posted a question to this list under the title "Battery Monitor - Follow up". (NOTE: I tried to put the link for this here, but couldn't figure out how to do it.) My Link 1000 was showing a consistent discharge of the batteries, despite the fact that the shore power was plugged in and the ac switch was on. I thought I'd solved that problem when I tightened up some wires on the plug that connected the charger to the shore power. When I thought I'd resolved the issue before, I reset the monitor after it seemed that the batteries were fully charged.

However, now I'm having the same problem. Over the last week, the monitor has gone from about -20 to now about -40 ah. If I run something like the fridge, the monitor will show that it's charging for a few seconds. I have everything on the charger/inverter set correctly, but it seems that something is definitely wrong.

As I wrote before, if it was showing a consistent negative ah, then I'd just figure that the monitor needed to be reset, but the fact that it is showing a steady drain is what concerns me.

Is it possible that the charger is malfunctioning in some way? That's about all I can figure out. I guess my next step is to get a meter and check to see what the charger is putting out. Does that sound right?

 

[Ed Schenck]

My own Link 2000 has two fuses. It will display some pretty strange symptoms if one is burned. Just this fall the "A/C In" lamp did not display and the "Charge" lamp was on even when shorepower was unplugged. One of the two fuses was open.

But yes, with a meter you should be able to verify that the charger is working. With the charger off or shorepower unplugged you should see something like 12.75 or lower. With shorepower in and charger on something over 13. on the meter.

 

[John]

I've been worrying about this drain on my batteries and the possibility that it may damage them - shorten their life - if it continues.

I have a couple of 75w solar panels that I'm planning to install at some point in the future. In the meantime, I was wondering if there would be an argument for temporarily wiring one of them directly to the batteries and just keeping an eye on it to make sure that I don't overcharge them - disconnect it when the battery monitor shows the batteries to be close to fully charged?

 

[Bill Roosa]

Time for some basics

Most battery monitors can display amps in/out of the batteries.
What is the monitor ammeter showing when you know you are discharging the batteries, when you know/suspect you are charging? Does this make sense?
Voltage is always a good way to tell charging is going on and monitors have that option also.
Does the monitors voltage agree with a multi meter check on the battery terminals?

The monitor has some screwy thing going on from what I can tell. It is either malfunctioning, installed wrong or has corrosion on some of the terminals, or there is an operator error. I assume operator error is not an issue. Corrosion or wires getting mixed up in the battery compartment is pretty common.

I read the first thread and from what I see there and here I would say check the wiring on the shunt. specifically the sense wires (the little ones not the power carrying ones) that feed a signal to the monitor. They sound like they are reversed (+ for -) and showing charge as discharge and discharge as charge.

 

[John]

I read the first thread and from what I see there and here I would say check the wiring on the shunt. specifically the sense wires (the little ones not the power carrying ones) that feed a signal to the monitor. They sound like they are reversed (+ for -) and showing charge as discharge and discharge as charge.

I will recheck the installation later today. However, I suspect it's something else since for a time the monitor seemed to be working correctly. Since it has only been installed for a few months, I doubt that corrosion would be a problem.

Again, the issue is that the monitor shows a steadily increasing amount of amp hours being discharged. When I select the "ah" light, it's showing about -40; a week ago, it was showing about -25 or so. If it were holding steady, then I'd say maybe it's malfunctioning or maybe the wiring is wrong. The other point is this: When I run some accessory - say the refrigerator - then the amp light shows an increase in the amount of amp outflow. After a time, if I turn back on the AC main switch, it shows the battery is being charged (amps go up to about 4 and then steadily decrease as the battery is charged).

I guess the weird thing is that this must show that the charger is working in some way, but why does the monitor show steady output of amps, even when the shore power is hooked up and the ac main switch is on?

 

[Lee Coller]

What's the size of your battery bank, and how many discharge cycles has it gone through (i.e., letting it discharge 25% and then recharge) has it gone through. I believe the Xantrex battery monitors calculate charge acceptance (the percent of amps actually stored in the battery compared to the amps received) dynamically based on past history. If there is no history there is a default value (90% I believe) that they use, and that can cause inaccuracies in the monitor reading. if 40ah is a small percentage of your battery bank I wouldn't worry about it. Try letting it discharge to 75% battery capacity and then see what happens.

Its true that a floating sense wire from the shunt can cause it show a study decrease or increase in amps, but I expect something much more drastic from what you are seeing if there was a loose connection.

 

[tsmwebb]

Does the battery charger wiring by-pass the shunt?

If re-setting the monitor makes the problem go away it could be that the monitor has some kind of internal data error. Depending on how the program is interpreting numbers it is possible for large (relative to the type) numbers to become large negative numbers when incremented (two's complement).

Anyway, if the battery voltage is staying above about 12.9 despite the reported draw then the charger is working and the problem is with the monitor.

--Tom.

 

[John]

i just talked with Xantrex. They suggested more or less what people here have suggested. I'm going to double check the wiring for the monitor, especially the shunt, but I don't think that's the problem because if it were, then it never would have worked correctly.

If you look at my previous thread on this, you will see that I had fixed a plug that I thought was loose and then reset the monitor. It seemed to be working fine for awhile after that, with the monitor showing 0 ah when the boat was not in use. Then, after the last time I took the boat out, this problem reappeared.

Also, I wonder what you think of what I'm considering doing until I can track down this problem: wire up a solar panel directly to the battery and just monitor it to make sure it doesn't overcharge.

 

[Bill Roosa]

Lets do some math

-25 AH to -40 AH in one week works out to:
-40-(-25) = -15 AH added to the battery in a week. Of course adding -15 is really a discharge as you have noted before.
15 ah/7 Days - 2.14 AH/day or 2.14/24 hours = 0.09 amps continuous draw. That is not that much. That is what I'd expect with a leaky prop shaft gland making the bilge pump come on once in a while. Lots of parisitic loads are of this nature also.
It could also be a stray current leak. How is your prop shaft zinc holding up?
I'd say you have a monitor that needs a total disconnect and reconnect. It is showing a (what I'd call) normal discharge even though it is doing it in a really dumb way.

Maybe there was a cosmic ray shower that put the monitor in a funny state that it cant get out of without a complete disconnect and restart. Not just a reset but a complete short the power wire to the ground disconnect. Stupid as that sounds I have seen computer chips do this kind of thing.

 

[John]

problem solved (?)

Since I was last here, I talked with Xantrex. The guy was pretty helpful, or tried to be, but he was stumped. As I told him, I wasn't too worried about -40 ah; what worried me was that this seemed to be continuous, meaning that at some point the battery would be so drawn down as to shorten its life. He agreed with this. He suggested that I recheck how I'd wired it up. He also said that while the Link 1000 is a "good" product, it is also very sensitive.

Then I went down to the boat to recheck my wiring. (Today, the monitor was showing -46 ah.) I didn't remember exactly what I'd done, or rather why I'd wired it like I had, and I thought I spotted a mistake in how I wired it. My main concern with this was, "s__t! How am I going to explain this to the guys on the sailor's forum after I swore up and down that I'd wired it correctly?") Anyway, I disconnected the negative cable and reconnected it like I thought it should have been. Of course, everything turned off at that point, including the monitor (which beeped a couple of times first). When I reconnected it, the monitor was still showing the same problem.

I tried starting the motor to see if the monitor would show it was charging the batteries, but the starter motor wouldn't turn over; clearly the new wiring was wrong. So then I went back and rewired it like it had been.

Bingo! The monitor then started showing the values that would be expected. When I turned off the AC main and ran a bunch of accessories, it showed the draw and then when I turned the ac main back on, it showed charging. When the monitor registered that it had stopped charging, it also registered about +0.2 amps, which I think is about right. (And, yes, the motor did start then.)

The only thing I can figure is that, as the Xantrex guy told me, this item is very sensitive and something got hung up inside the mini computer that is its guts. Then, when I disconnected the battery, this allowed it to reset itself.

Lesson learned for next time... and thanks for all the advice.

 

[Don12364]

John,
I too experience a small steady current drain which I have analysed as below:-

My boat file reads: Batty Monitor - Link 1000 – Standing current Quiescent = 41 mA. Display on = 56 mA which I measured on installation in 1996.

This means the Link itself will drain about 6.9 Ah per week.

Then there is the high rate alternator system which has its sensing circuit permanently across the battery - a few more milliamps.

Add my NAVTEX weather system which I keep permanently on so a forecast is instantly available when I go aboard - another 45 mA.

The Burglar Alarm in quiescent mode accounts for a few more!

Now, does the bilge pump run occasionally? I've no idea. The water in the base of the keel is always as low as the pump will drain.

Add the 'keep alive' current required by my in house radio to maintain its programmed stations frequencies - though this is actually negligible.

Next, realise that the minimum current the Link can measure or indicate is 0.1Amps i.e. 100 mA. It shows 0.1A draw even if the actual current drain is only 0.55A (55 mA). It registers this over a week as 16.8 Ah even though the actual would have been only 9.2 Ah. i.e. In this case it over reads the ampere hours drained from the battery.

All in all using the Link for these small currents is something it was not designed to do accurately so I just use it as a guide and recharge the batteries to full whenever I am alongside a dock.
My boat normally sits on a mid-stream mooring with no shore power.

 

[Ron20324]

So far, would you 1000 users say it is safe to say it's worth buying?

 

[John]

First, in response to Donalex: Yes, I understand that there will be a constant parasitic draw. Included in this will be the circuit for the bilge pump also. This was not my issue. My issue was that I would have expected that within a certain range, once the draw reaches a certain level - that is, once the amp hours drawn out reach a certain level - then the charger would kick in and recharge the batteries back up to full. This wasn't happening, or at least the monitor wasn't showing it happen, so the amp hours were registering a constant decrease. If the monitor was accurate and this continued, then I was worried about draining the batteries to the point of damaging them.

In response to Ron: I did get a very good price on the Link 1000. But even if I'd had to pay full price, I think it was worth it - if the monitor continues functioning correctly. It really does show the state of the batteries in a way that I couldn't get otherwise. It also does show what accessories draw how much. And this is aside from the fact that, for me, having had to install and understand the functioning of it has helped me understand a lot about my electrical system.

 

[Bill Roosa]

Cosmic ray shower!!!

Hi John
Glad to see that things are starting to work the way we think they should. I am reminded of the space shuttle with its 7 computers all calculating the same thing and then one computer taking the "average" of the results and moving the controls. They have to do reboots of the whole system while on orbit from time to time due to cosmic ray showers.

I still think the cosmic ray shower is the best explanation so far.

 

[John]

Actually, Bill, I think it's Gremlins who live off of electric power. When I disconnected the battery cable, this caused them to lose power and die. However, I am sure they will return. The weird thing is that they can show up at any time, in any part of the boat.