Battery Monitor glitch - need help!

[rherten]

I've been trying to solve an issue with my Xantrex battery monitor for over a year.

In a nutshell the battery monitor gradually reads less than 100% full when the boat is on shore power for a while. For example I can leave the boat plugged in to shore power for days and it might get up to 95% but not 100% (Let's say -20Ah). I can surmise the batteries are topped up by checking the voltage and seeing that there are no more amps flowing in, so I'll reset to 100% and observe. Over time it will start indicating less than 100% again, or I'll go for a trip and plug in afterwards to see the monitor indicate under 100% when full. Over time if I don't re-set to 100% it will decrease more. Maybe down to 92% after another week and down to 88% after that, etc. All the time I'm pretty sure the batteries are full, judging my how long I am plugged in and looking at voltage and charge rate.

A bit more background - it was working fine on my previous house batteries (firefly AGM's) until I had them replace with Victron AGM's. 6 batteries in the bank, 12V, approx 750 Ah capacity. That seems to be what triggered the issue - I had no problem with the monitor before then. I had the Victron batteries installed by a reputable marine electrical contractor but they are unable to determine the problem and eventually told me it was likely the monitor. I went and replaced my Xantrex Link Pro monitor myself with a brand new Xantrex Link Lite and am experiencing exactly the same issue! At this point I'm out of ideas. The electrical contractor is charging me top dollar for every call back and not really solving the issue and I've been through the system as best I can with my monitor, checking connections, checking the shunt is wired properly, etc. I contacted Xantrex earlier on in the process and they cast doubt on the batteries, but I don't think that's the issue as I had the electrical contractor out since then to check.

I've experienced similar issues when charging with the shore power charger or with alternators from the engine.

Any ideas would be much appreciated!

 

[STB]

This is one of those that seems likely to take a lot more detail...

What voltages are you measuring and where? Are you measuring with any current sources enabled?

Is the Xantrex wired to monitor both banks? Or just the houae?

How are you measuring charging current flow, where, and over how long?

Are you measuring outgoing current flow? What is the measurement? Where is it taken and over how long?

 

[O C Diver]

I would look at the menu of the battery charger to confirm that it's set for your type or float voltage of your batteries. If I read you correctly, after running the boat where the alternator is charging the battery bank, the meter reads full. It's on the shore power charger that it reads less. On my SOC (state of charge) meter, the meter resets to 100% after a period when amps aren't flowing in or out (batteries are full). It seems to me that the alternator cut off and the battery charger cut off don't match. Do you have an external regulator (programable) on your alternator?

Ted

 

[SteveK]

I have a shunt monitor system. Do you know the battery exact Ah and did you tell the monitor. You said 750.
That said I have a SOC leak as well even though charger is on standby. Suspect the shunt is reading DC load but the charger is not seeing drop of voltage enough to trigger a charging.

 

[rherten]

This is one of those that seems likely to take a lot more detail...

What voltages are you measuring and where? Are you measuring with any current sources enabled?

Is the Xantrex wired to monitor both banks? Or just the houae?

How are you measuring charging current flow, where, and over how long?

Are you measuring outgoing current flow? What is the measurement? Where is it taken and over how long?

- Voltage taken from battery monitor and checked with meter directly at house bank. With and without current sources enabled. Battery monitor appears to be indicating voltage accurately.
- Monitor is set to primarily measure the house bank. I also have leads wired to starter battery for voltage only. But it's the house bank I'm having trouble with.
- Charging current - I'm basically relying on the reading from the monitor.
- Outgoing current flow - Again, I'm relying on the monitor. I suppose I could put a clamp meter on the negative lead to the shunt to check this?

 

[rherten]

I would look at the menu of the battery charger to confirm that it's set for your type or float voltage of your batteries. If I read you correctly, after running the boat where the alternator is charging the battery bank, the meter reads full. It's on the shore power charger that it reads less. On my SOC (state of charge) meter, the meter resets to 100% after a period when amps aren't flowing in or out (batteries are full). It seems to me that the alternator cut off and the battery charger cut off don't match. Do you have an external regulator (programable) on your alternator?

Ted

- Battery charger settings have been checked and are correct
- The issue is the same whether charging from the charger (shore power) or from the alternators. Indicates somewhat under full even when it should be full.
- Meter reset at full SOC - yes I'm not sure why mine doesn't do this. I have checked the parameters - I believe there is a voltage threshold which should trigger a reset to 100% but it doesn't. Perhaps this deserves a closer look with Xantrex. I have noticed that when it's on full the amps tend to bounce around a bit. +/- 1 amp or so which I assumed is normal. Perhaps that's enough to make the monitor think it's still not full.
- No I don't have an external regulator.

Thank you

 

[rherten]

I have a shunt monitor system. Do you know the battery exact Ah and did you tell the monitor. You said 750.
That said I have a SOC leak as well even though charger is on standby. Suspect the shunt is reading DC load but the charger is not seeing drop of voltage enough to trigger a charging.

- Yes I have 6 X 125 Ah Victron Super Cycle AGM's, which provide 750Ah in parallel. I have checked the monitor to make sure it's programed correctly.
- I get what you're saying, but not sure that's the case for me. For example I can run the batteries down a bit, then re-charge and get something less than Full. If I repeat this process a few times the SOC decreases progressively. For example I could be indicating a Full charge, then run the batteries down, charge them up again and end up at 95%. Then run the batteries down, recharge them and end up to 92%. etc. So the charger is topping them up, but the monitor thinks they are not fully charged.

Thank you

 

[Ka_sea_ta]

Couple of things to check, 1st is the SOC for your battery bank with a known accurate external volt meter. You should be able to find SOC tables for the Victron AGM batteries. Your batteries might be 100% charged at a lower voltage then the monitor is programed for, and with a internal regulator the batteries might actually be overcharged and have a higher surface charge that slowly degrades over time. This higher surface charge could be used by the monitor to determine the SOC and be artificially high.



The second thing may be that incorrect float charge parameters are being used... If the float charge is programed to turn on at too low of threshold the batteries may be draining enough voltage that the SOC is actually reading correctly as programmed, this could be true especially if the SOC values are incorrect for your batteries.

 

[Bmarler]

I think it’s hard for an internally regulated alternator to correctly charge a bank like that. I kinda doubt it’s overcharging amp hour wise, but it probably is delivering the wrong voltage.
An external regulator is really nice to have as you can set it exactly how your batteries require.
I’m wondering about the tail current setting on the charger. Many times this isn’t right as the house bank is in service when the charger is on and replenishing the bank. I calculated my tail current to the size of the bank then added the parasitic load of my house bank to that. Then the float kicks in. Float needs to be able to deliver house loads plus the rest of the charging to top off the batteries.

 

[Rated Aargh]

While i cant help 100%, i jut read a great article that talks about this in great detail.
try doing a search for "link algorithm operation" posted by "Stu Jackson" it was posted on April 20, 2009.