BEP Battery Monitor misbehaving?

[camman]

On more than one occasion the battery monitor has given the same reading on our return to the boat 4/5 days later as it did when we left her, after a weekends use, but when the engine is run for 5/10 minutes the meter is reading 100%.

On the latest occasion the meter read 64%, 142Ah, 12.9 volts on leaving the boat, on our return two days later it was reading the same but after running the engine for less than 10 minutes it was showing 100%, 220Ah, 13.9 volts.

There are 3 batteries totaling 330Ah (I think only the house batteries are monitored 2x120Ah) they are charged by a permanent 25 amp solar panel and on the occasion quoted above a 6 amp mains charger.

Is the battery monitor misbehaving?

 

[VicS]

On more than one occasion the battery monitor has given the same reading on our return to the boat 4/5 days later as it did when we left her, after a weekends use, but when the engine is run for 5/10 minutes the meter is reading 100%.

On the latest occasion the meter read 64%, 142Ah, 12.9 volts on leaving the boat, on our return two days later it was reading the same but after running the engine for less than 10 minutes it was showing 100%, 220Ah, 13.9 volts.

There are 3 batteries totaling 330Ah (I think only the house batteries are monitored 2x120Ah) they are charged by a permanent 25 amp solar panel and on the occasion quoted above a 6 amp mains charger.

Is the battery monitor misbehaving?

Is it because the solar panel charging is bypassing the battery monitor ??

 

[AngusMcDoon]

Battery monitors that give a percentage charge are snake oil for lead acid batteries. I did some investigation when I made my own YAPP version. You can monitor Ah in and Ah out. You can monitor voltage. But giving a percentage charge state is just a rough guess. It depends on battery technology, charging rate, discharge rate, battery age, temperature, resistance in your cables and joints, time since charging stopped, time since last used and so on. It's interesting to see voltage, instantaneous current rate and total Ah, but the percentage value is just a marketing man's dream.

 

[jon]

Its all to do with the Peukerts Discharge Rate calculation (see manual).
Might be easiest to reset to factory settings.

 

[William_H]

On more than one occasion the battery monitor has given the same reading on our return to the boat 4/5 days later as it did when we left her, after a weekends use, but when the engine is run for 5/10 minutes the meter is reading 100%.

On the latest occasion the meter read 64%, 142Ah, 12.9 volts on leaving the boat, on our return two days later it was reading the same but after running the engine for less than 10 minutes it was showing 100%, 220Ah, 13.9 volts.

There are 3 batteries totaling 330Ah (I think only the house batteries are monitored 2x120Ah) they are charged by a permanent 25 amp solar panel and on the occasion quoted above a 6 amp mains charger.

Is the battery monitor misbehaving?

I presume that was a typographical error and the solar panel is really 25watts or max 1.25 amps.
If it were 25 amp we might expect panels at least 2 maybe 3 at around 1.7 X 1.2 metres. and 500 watts
Yes I agree with Angus accuracy of % charge is really just hopefull. olewill

 

[pvb]

On more than one occasion the battery monitor has given the same reading on our return to the boat 4/5 days later as it did when we left her, after a weekends use, but when the engine is run for 5/10 minutes the meter is reading 100%.

On the latest occasion the meter read 64%, 142Ah, 12.9 volts on leaving the boat, on our return two days later it was reading the same but after running the engine for less than 10 minutes it was showing 100%, 220Ah, 13.9 volts.

There are 3 batteries totaling 330Ah (I think only the house batteries are monitored 2x120Ah) they are charged by a permanent 25 amp solar panel and on the occasion quoted above a 6 amp mains charger.

Is the battery monitor misbehaving?

I don't fully understand your post. You're mentioning engine charging, but then you say it was a mains charger.

The most likely explanation is that your monitor isn't correctly set up. I'd suggest you look at the manual and reset it to the conditions it's working with (battery type, battery bank size).

As for others' comments about percentage displays, there's no reason why these shouldn't be fairly accurate - the percentage is computed on the basis of battery capacity and Ah readings, and it's hardly rocket science.

 

[AngusMcDoon]

As for others' comments about percentage displays, there's no reason why these shouldn't be fairly accurate - the percentage is computed on the basis of battery capacity and Ah readings, and it's hardly rocket science.

You can believe the value if you like, but it's far more complex than that. Read here...

http://www.smartgauge.co.uk/peukert2.html

A quote from the above site...

"Typical Peukert exponents vary widely between different manufacturers but an average figure for a true deep cycle battery is about 1.3. For AGMs about 1.10 and for hybrids about 1.15. Have a play. You will be surprised at just how much difference a heavy discharge rate makes to the available run time. "

 

[pvb]

You can believe the value if you like, but it's far more complex than that. Read here...

http://www.smartgauge.co.uk/peukert2.html

A quote from the above site...

"Typical Peukert exponents vary widely between different manufacturers but an average figure for a true deep cycle battery is about 1.3. For AGMs about 1.10 and for hybrids about 1.15. Have a play. You will be surprised at just how much difference a heavy discharge rate makes to the available run time. "

Yes, I think we're all aware of the effect of Peukert's exponent. The BEP monitor mentioned by the OP uses algorithms based on Peukert's exponent. By default, the BEP monitor uses a Peukert value of 1.25 but it can be user-adjusted between 1.00 and 1.50. That's one of the reasons why I suggested the OP should reset the monitor to suit his batteries.

 

[noelex]

If you use a good battery monitor and adjust and install it correctly the readings are quite accurate.
Unfortunatly they are a bit complex to set up and they are often poorly adjusted. It's not even unusual to see them wired with a significant load or charge source that does not go through the shunt.

 

[camman]

My main query was the fact that the meter gives the same reading, whether its %, volts or Ah's, on our return to the boat as it did when we left her maybe 5 days before, it's only when the engine has been run for 5/10 minutes that the meter readings change.
Apologies, its a 25 amp regulator and a 30 watt solar panel.

 

[pvb]

My main query was the fact that the meter gives the same reading, whether its %, volts or Ah's, on our return to the boat as it did when we left her maybe 5 days before....

It sounds as if your solar panel isn't wired through the battery monitor then, or alternatively the solar panel isn't working.

Regardless, 5-10 minutes of engine charging shouldn't suddenly produce 100% charge reading unless the monitor's settings are wrong.

 

[Stu Jackson]

Agree. Check that the shunt is wired correctly, then check the default values. Most battery monitors should be reset when the bank is full. If you don't know whether all three of your batteries are n=monitored and are only guessing it's two of them, then you should play detective and find out for sure.

http://forums.catalina.sailboatowners.com/showthread.php?t=125606