Battery not charging when on a charger, even when on a load

[ShrimpBurrito]

The thing about having nifty gadgets like the Link 10 is you get to monitor the minute details of your TM. Maybe that's also a disadvantage, as perhaps sometimes ignorance is bliss.

The Link 10 monitors "total Ah consumed" as well as an instantaneous "current draw" reading. The "total Ah consumed" reading is net, meaning power into the battery from the charger minus power out from loads. With the charger connected and the TM set up, with the phantom loads (radio, LP detector) drawing a max of few tenths of an amp (which fluctuates down to zero), I am drawing about 1 Ah per day from the battery. For some reason, the charger is not putting that power back into the battery.

While that may not seem like alot, when I opened the TM last weekend after a month or two, there was a -30 Ah draw, meaning 30 Ah had been removed from the battery and not recharged. After consulting the Link 10 manual, I thought perhaps the Link 10 and charger had gotten "out-of-sync", meaning the Link 10 was not calculating the actual power charged to the battery accurately after considering the less than 100% charging efficiency. So I reset the Ah counter to zero, and went camping. After coming back, I hooked the TM back onto its charger, and the Ah counter go to within about -2 Ah. It's been about 5 days since then, and we are now up to about -9 Ah.

I have connected my TM up to 2 different 3-stage chargers -- one about 2 amps, the other 6 amps -- and they produce the same result.

Why is this happening? The no load (except phantom) battery voltage is right up at 12.8v-12.9v or so, even after 24 hrs, which is well within the range of being fully charged.

Dave

[ZekenSpider]

Originally Posted by ShrimpBurrito

The thing about having nifty gadgets like the Link 10 is you get to monitor the minute details of your TM. Maybe that's also a disadvantage, as perhaps sometimes ignorance is bliss.


Why is this happening? The no load (except phantom) battery voltage is right up at 12.8v-12.9v or so, even after 24 hrs, which is well within the range of being fully charged.

Dave

Just a guess. So many things need to be measured to be certain, but any AH measurement requires:

1) a really accurate internal clock but it's unlikely the clock is running backwards.

2) a really accurate current measurement. This is more suspect. The Link 10 specifications say the amp measurement accuracy on the 0 to 40 amp scale is +/- 0.1 amps. That means in a 10 hour period the AH reading could be as much as 1 AH higher or 1 AH lower than reality. I assume you are looking at the Link 10 0-199 AH range. That range uses the +/- 0.1 amp resolution.

Actually the Link 10 (or any other AH meter for that matter) doesn't measure amps. It measures the millivolt drop across the shunt. Shunts are standardized to be calibrated at either 50 millivolt or 100 millivolt drop. In other words, a 0 to 2000 amp shunt will show 0 millivolts across it at 0 amps and 50 or 100 millivolts across it at 2000 amps. For this reason the internal millivolt meter must be very accurate.

The Link 10 may have an adjustment that allows you set the zero current value.

I suspect there is not a negative amp flow happening. More than likely, the link 10 millivolt meter is at the low end of its' +/- 0.1 tolerance. If you have a really good multimeter, measure the voltage across the shunt (+ end is current in). I'm guessing you will see no negative voltage except when the charger is cycled off.

FWIW

Jerry

My battery monitor is a Tri-Metric and I had the same thing happen first time I hooked up a charger to my TM batteries. Had me worried for a while until I realized you can’t connect the charger directly to the battery. The Pos. lead from the charger has to go down stream of the shunt in order for it to read the amp input. Hope this is all that is wrong with your setup.

ED

[ZekenSpider]

Originally Posted by Digger

My battery monitor is a Tri-Metric and I had the same thing happen first time I hooked up a charger to my TM batteries. Had me worried for a while until I realized you can’t connect the charger directly to the battery. The Pos. lead from the charger has to go down stream of the shunt in order for it to read the amp input. Hope this is all that is wrong with your setup.

ED

Ed;

Is your shunt in the Positive battery lead?

My monitor is also a Tri-metric. My instructions said to connect one end of the shunt to the Negative battery post and all TM negatives connected to the other end of the shunt. If yours is like mine, an external charger POS lead should connect to the battery POS terminal and the charger NEG lead should connect to the TM side of the shunt. That way the shunt can measure current into and out of the battery.

In my TM, current flow is through the shunt into the battery NEG.

Maybe I'm not understanding what you are saying. Sorry if that's the case.

Either way, you are right when you point out that if the external charger is not connected to the proper side of the shunt, the readings will be in error.

Jerry

Is your shunt in the Positive battery lead?

My monitor is also a Tri-metric. My instructions said to connect one end of the shunt to the Negative battery post and all TM negatives connected to the other end of the shunt. If yours is like mine, an external charger POS lead should connect to the battery POS terminal and the charger NEG lead should connect to the TM side of the shunt. That way the shunt can measure current into and out of the battery.

You are correct, The shunt is connected to the Neg post. I should have said the Neg. lead from the charger needs to go on the down stream side of the shunt. My bad, that's what beer does to your thinking.

Thank's for setting me stright. ED

[ShrimpBurrito]

Originally Posted by ZekenSpider

My monitor is also a Tri-metric. My instructions said to connect one end of the shunt to the Negative battery post and all TM negatives connected to the other end of the shunt. If yours is like mine, an external charger POS lead should connect to the battery POS terminal and the charger NEG lead should connect to the TM side of the shunt. That way the shunt can measure current into and out of the battery.

In my TM, current flow is through the shunt into the battery NEG.

Jerry,

This is exactly how I have mine setup.

This "problem" was not happening before after maybe 1-2 years of use, and I think that is because the Link 10 had detected that the batteries had "met the charged parameters", and thus, automatically reset the Ah counter to zero and indicated that charged parameters were set by flashing an LED. That LED is not flashing now, and obviously, the Ah counter did not reset. So do I have a NEW problem, or has this always happened and it was just masked by the fact that the Link 10 had identified that the charged parameters had been met and reset the Ah counter?

What are the "charged parameters"? From the manual:

The factory Charged Parameters are 13.2 volts and 2% of battery capacity as charged current. (2% of default battery capacity of 200 Ah equals 4 amps). Several conditions must be met for a recalculation of the CEF (Charge Efficiency Factor) and a reset to zero: First, 100% of the energy removed from the battery must be returned, additionally the battery must be above 13.2 volts and the current must fall below 4 amps for 5 minutes. When all these conditions are met, the battery is considered full.

So, in my case, have I met the criteria?

1) 100% of the energy removed from the battery must be returned (I have no way of knowing this, that's why I bought the Link 10!)

2) the battery must be above 13.2 volts (yes)

3) the current must fall below 4 amps for 5 minutes (yes)

So after reviewing this, I would conclude, ok, I met #2 and #3, so #1 must be the issue. That is why I manually reset the Ah counter, thinking my batteries are starting to show their age at nearly 3 years, and starting to not accept a full charge. But that should have fixed the problem for awhile. I shouldn't run into it again a week later, and the Ah counter should continue to show a negative value that gets more negative every day.

I will measure the voltage across the shunt tomorrow...BTW, it's a 500 A 50 mV shunt.

Thanks for your help.

Ed - try gin & tonic in between beers. Seems to help for me.

Dave

[ZekenSpider]

Originally Posted by ShrimpBurrito

Jerry,

This is exactly how I have mine setup.

This "problem" was not happening before after maybe 1-2 years of use, and I think that is because the Link 10 had detected that the batteries had "met the charged parameters", and thus, automatically reset the Ah counter to zero and indicated that charged parameters were set by flashing an LED. That LED is not flashing now, and obviously, the Ah counter did not reset. So do I have a NEW problem, or has this always happened and it was just masked by the fact that the Link 10 had identified that the charged parameters had been met and reset the Ah counter?

What are the "charged parameters"? From the manual:

The factory Charged Parameters are 13.2 volts and 2% of battery capacity as charged current. (2% of default battery capacity of 200 Ah equals 4 amps). Several conditions must be met for a recalculation of the CEF (Charge Efficiency Factor) and a reset to zero: First, 100% of the energy removed from the battery must be returned, additionally the battery must be above 13.2 volts and the current must fall below 4 amps for 5 minutes. When all these conditions are met, the battery is considered full.

My Tri-Metrics manual says the typical lead-acid wet cell has a charge efficiency of 94 to 96%. That means it takes 105% of the AH removed to recharge it. That percentage is adjustable on mine, so it may also be on yours. Even so, this should only effect when the AH resets. It should not have any effect on your AH showing negative unless there is really current leaving the battery.


So, in my case, have I met the criteria?

1) 100% of the energy removed from the battery must be returned (I have no way of knowing this, that's why I bought the Link 10!)

100% of the battery capacity will probably drop as the battery ages. In my case, I have to define the capacity and then modify it as I estimate what aging is doing to the battery. Not an easy or precise process.

2) the battery must be above 13.2 volts (yes)

3) the current must fall below 4 amps for 5 minutes (yes)

So after reviewing this, I would conclude, ok, I met #2 and #3, so #1 must be the issue. That is why I manually reset the Ah counter, thinking my batteries are starting to show their age at nearly 3 years, and starting to not accept a full charge. But that should have fixed the problem for awhile. I shouldn't run into it again a week later, and the Ah counter should continue to show a negative value that gets more negative every day.

I agree. There is no way that you should show negative current (and therefore negative AH) with the charger on(unless the charger pulses on, then off, etc.)

I will measure the voltage across the shunt tomorrow...BTW, it's a 500 A 50 mV shunt.

Thanks for your help.

Ed - try gin & tonic in between beers. Seems to help for me.

Dave

[ShrimpBurrito]

Jerry,

Referring to your response above:

1) As described by this criteria, I don't think battery capacity has anything to do with energy consumed. If you have a 10,000 Ah battery, and you consume 100 Ah, I think the only thing this criteria is saying is that the 100 Ah (plus a bit extra to compensate for the Charge Efficiency Factor [CEF]) passes back through the shunt. Using your estimate, let's assume an extra 5%. If the capacity of that same battery lowers to 8,000 Ah over time, and you once again consume 100 Ah, this criteria will still be met when 100 Ah + the 5% CEF premium passes through the shunt.

3) One of the chargers I have is a pulse charger, and the other is not. IIRC, both however, seem to make the instantaneous current measurement roughly the same......wavering from maybe -0.5A to +0.5A, changing back and forth every few seconds. IIRC, this is consistent with what it used to read after the batteries were completely charged, as determined by the Link 10. Apparently, however, the reading is more on the negative side over time, as the cumulative Ah reading is increasingly negative.

I may give Xantrex a call to see if they have any ideas.

Dave

Dave

What happens when you hook up to shore power. What is the amp reading when charging with the TM converter.
Ed

[ShrimpBurrito]

Did a bit more troubleshooting.

First, I measured the voltage across the shunt. I have a decent multimeter...a $50 job, not a Fluke, but it does have a mV scale. With a 9.6-9.7A load, the voltage was approximately -0.9mV. With a charge current of 2.2-2.4A, the voltage was +0.2mV. So that is certainly about right for a 500A 50 mV shunt. With a 0.2A load (the phantom load), the voltage was too small to measure accurately....it would have had to have been in the microvolt range.

Second, when I unplugged the pulse charger and plugged in the TM converter, a charge current of about 0.3A appeared. After ~20 minutes, it fluctuated between 0.0 and 0.1A. So at least that's in the positive, but obviously, I can't leave it connected long term. Besides, I never had this problem before, and nothing has changed since that time.

Third, I contacted Xantrex. He suggested disconnecting the sense leads from the shunt and shorting them together. That should cause the Link 10 to read a 0.0A draw, since there is no resistance generated by the shunt. If it doesn't read 0.0A, that means the sense leads, a shielded twisted pair, is likely picking up noise somewhere. Highly unlikely IMHO, especially since I did not have this problem before and haven't made any changes since. He also suggested that if that happens, to go to the Link 10 and short the sense lead connectors on the back of the unit with a jumper cable. If that causes the Link 10 to show a 0.0A draw, that confirms the sense leads are picking up noise.

If after shorting the sense leads, the Link 10 does show a 0.0A current draw, then he suggested the Link 10's voltmeter has become miscalibrated, and cannot be repaired. I don't know how this is possible with a microprocessor controlled unit. There's nothing mechanical about it and it's not subject to any heat. What could go wrong with it?

Dave