Victron battery monitor

[lesrollins]

Having just replaced the analogue volt meter with a victron battery monitor I just wondered if anyone could help with a few questions.

 

What SOC should I not let the batteries fall below 50%, 60% etc

 

After bulk, absorption and the float period when is it best to turn off the charging system or do I wait for the amps on the battery monitor to hit a certain point before switching off the charging system.

 

What volts is it best not to let the monitor fall below.

 

Cheers

[bottle]

What SOC should I not let the batteries fall below 50%, 60% etc.............................50% this is not an absolute but a guidance.See links:

 

After bulk, absorption and the float period when is it best to turn off the charging system or do I wait for the amps on the battery monitor to hit a certain point before switching off the charging system.............................when it goes into float, float is the charging just maintaining batteries and not allowing self dis charge.

 

What volts is it best not to let the monitor fall below........................Not quite sure what your question is but 12.2v [0ff load] on a 12v system is equal to 50% SOC

 

Links.

 

http://www.batteryfaq.org/

 

http://www.smartgauge.co.uk/technical1.html

[Tony Brooks]

Having just replaced the analogue volt meter with a victron battery monitor I just wondered if anyone could help with a few questions.

 

What SOC should I not let the batteries fall below 50%, 60% etc

 

After bulk, absorption and the float period when is it best to turn off the charging system or do I wait for the amps on the battery monitor to hit a certain point before switching off the charging system.

 

What volts is it best not to let the monitor fall below.

 

Cheers

 

 

I am not going to answer your question directly but my advice is to forget the state of charge readings and use the voltmeter function.

 

If you do not set it up correctly the SOC meter will lie.

 

If you do not very regularly FULLY recharge - that means 100%, 12.8 volts after standing overnight - the SOC meter will lie.

 

There are many posts on here about such things and many come about because of ruined banks with very little capacity showing very high percentages of charge.

 

You do not specify what you mean by "charging system". If you mean the alternator then it is very doubtful that you will ever get the bank very much above 80% charged whatever the SOC meter alleges. You may if you run for at least 10 hours.

 

If you mean a multi-stage charger then leave it on 24 hours a day.

[Hawkmoth]

Having just replaced the analogue volt meter with a victron battery monitor I just wondered if anyone could help with a few questions.

 

What SOC should I not let the batteries fall below 50%, 60% etc

 

After bulk, absorption and the float period when is it best to turn off the charging system or do I wait for the amps on the battery monitor to hit a certain point before switching off the charging system.

 

What volts is it best not to let the monitor fall below.

 

Cheers

I've had a bit of experience with battery monitors and my advice is not to rely on them. The best indication of your SOC is the voltage when no or very little drain is on the bank. It is recommended, I believe, not to let the battery go below 12.2 volts (for a 12 volt system). From what I read on expert sites???? a battery is considered fully charged when the charge rate falls TO 3% of the capacity at the rated charge voltage. ie a 200 A/h bank is charged when the rate falls to 6 amps AT THE RATED CHARGE VOLTAGE FOR THAT TYPE OF BATTERY.

[nicknorman]

Having just replaced the analogue volt meter with a victron battery monitor I just wondered if anyone could help with a few questions.

 

What SOC should I not let the batteries fall below 50%, 60% etc

 

After bulk, absorption and the float period when is it best to turn off the charging system or do I wait for the amps on the battery monitor to hit a certain point before switching off the charging system.

 

What volts is it best not to let the monitor fall below.

 

Cheers

Generally the ballpark figure that is bandied around is 50% SOC before recharging, but recharging before 50% is reached will increase battery life a bit, recharging below 50% will shorten it a bit - it is not a magic figure.

 

Best not to rely on the battery monitor SOC reading to determine when to stop charging. As has been said, it these meters are fairly inaccurate in this repect due to the vaguearies of battery charging chemistry. As you suggest, use current as a guide. 3% has been quoted but that seems rather high to me. Perhaps a better way is when the charge current drops not further after say an hour. As has also been stated, if you have shore power and a proper multi-stage charger, leave it on all the time.

 

To get a correct SOC reading during discharge, it is necessary to start from a known correct point ie batteries fully charged with 100% SOC reading. It is also vital to set the battery capacity correctly - not to what it says on the battery label but to what it actually is! This is difficult, and the correct capacity changes gradually as the battery ages.

If an incorrect (usually optimistic) capacity is entered into the settings, and/or if the battery is cycled a few times between say 50% and 80% SOC, the SOC reading will be complete rubbish!

 

This is where the SmartGauge comes in handy - it gives a reliable SOC on discharge based on voltage, so reflects the actual SOC relative to the actual capacity, not some imaginary figure on the battey label! I have a current-type battery monitor of the same basic concept as yours, but also a Smartgauge. By comparing the two on discharge I can see whether the battery capacity is set up correctly in the current-based meter, and keep track of how the capacity is slowly fading.

 

In summary

 

1) The Smartguage is the best tool for monitoring SOC on discharge

2) A digital ammeter is best for determining when batteries are fully charged.

3) A current based SOC meter such as the Victron is really only useful for determining what the actual battery capacity is (in conjuction with a SG, or rested battery voltage readings if you can't afford a SG), although it does of course provide the current display needed for 2) above.

 

Your final question - 12.2v with no load having been applied to the batteries for (ideally) an hour or so. Any load will pull the voltage down further and so does not give the correct impression.

Edited June 16, 2012 by nicknorman

[Chalky]

If you've got solar panels or other forms of charging this can confuse the SOC calculation on some units (the one I've got gets very confused by it!). As said by other posters use the volt meter and ammeter functions. They'll tell you far more and you'll at least know what's going on.

[by'eck]

Having just replaced the analogue volt meter with a victron battery monitor I just wondered if anyone could help with a few questions.

 

What SOC should I not let the batteries fall below 50%, 60% etc

If using regularly available lead/acid leisure batteries its generally accepted that they should never be discharged below 50% SOC, since their life is reduced disproportionately above this amount. Ideally you want to drain the batteries an absolute minimum before re-charging though, since each discharge will take away a little of their life. The greater the discharge the more their life is reduced.

 

 

After bulk, absorption and the float period when is it best to turn off the charging system or do I wait for the amps on the battery monitor to hit a certain point before switching off the charging system.

Since you have a multi-stage charger, it should be left on continuously if possible. No harm will come to the batteries since it will be a float mode most of the time, indeed the batteries will benefit from it. Do check electrolyte levels regularly though.

 

 

What volts is it best not to let the monitor fall below.

Answered already but say 12.2 volts which equals approx 50% SOC. See above.

[lesrollins]

Thanks for all your answers.

I have now built my boxes for the solar panels and have got one working I am waiting for a lenght of cable for the other before connecting it. The panels are 2 x 140 watts and at the moment with one panel connected the voltmeter is reading 12.91 volts is this about right. Given the fact it is now overcast / dull with rain.