Smart Shunt question

[Lyrick]

Can anyone give me advice or thoughts on the following :-

I had my suspicions that my 18 month old 100ah AGM battery was on its way out so thought I'd try the motorhome on battery only for a few hours and check the progress with my Victron Smart Shunt.

The result below has confused me (not difficult) . The attached screenshot shows that after about 18 hours the battery voltage is 12.15volts , which according to a previously posted chart says that the state of charge is around 60%, but the Smart Shunt shows it as 97%. The consumed Ah, hidden behind the low battery warning, is 6ah.

When I switched the lights on in the motorhome the 12v system shut down and the battery voltage fell to 10.5 volts briefly so the battery has had it .

The battery showed as fully charged before I started - Smart Shunt showing 100% and the battery voltage was showing the float voltage as 13.5 volts . It had on a mains charger for the previous 3 days.

Am I misreading the information shown ? I have also attached a screenshot of the settings used . Do they look correct?



I'm assuming I'm missing something.
.

 

[Richard n Ann]

So I think I've settled on an Exide ES900 gel battery to replace the dead AGM battery.
I just have one question . I have a smart alternator and a B2b charger installed .
I've read that gels don't like a high charging current will this setup cause any problems ?

Thanks

Patrick

I bought the same battery 2½ years ago and it's been great so far, the voltage doesn't drop past 12.9 until we'll into the evening. Should be OK charging at 20 amps. I bought a 10 amp charger with the gel profile for ours.
How big is your B to B charger?

 

[Raul]

Now another wrinkle. Clearly I'm clueless here! . Pitched up today at about 12.30 after a 2 hour motorway run. Battery appeared to be fully charged as you would expect. Went off sightseeing, got back 5 hours later and checked battery using the Victron Connect app. One thing I noticed is that it tells me in the history that its 53 minutes since last full charge. That doesn't really stack up. What am I missing?

Assuming it was fully charged when you parked up is wrong. The charging continued with float charging till solar off. Remember, after bulk-absorb, a battery can be anywhere around 80-90% full. The float voltage still charges even 6-8hrs after absorb finished. Sometimes can take 16-18hrs on mains for a full charging cycle. The only time takes less, is when you partially discharge. The shallower the discharge, the shorter the bulk-absorb, but float takes hrs. You can reduce float time, by up the voltage a tad on absorb setting, if battery allows. Also the temperature compensation charging if is active, can slow, or, speed up the charge, depending on temp.

 

[acropolis22]

Assuming it was fully charged when you parked up is wrong. The charging continued with float charging till solar off. Remember, after bulk-absorb, a battery can be anywhere around 80-90% full. The float voltage still charges even 6-8hrs after absorb finished. Sometimes can take 16-18hrs on mains for a full charging cycle. The only time takes less, is when you partially discharge. The shallower the discharge, the shorter the bulk-absorb, but float takes hrs. You can reduce float time, by up the voltage a tad on absorb setting, if battery allows. Also the temperature compensation charging if is active, can slow, or, speed up the charge, depending on temp.

So, are you saying that the solar was continuing to charge the battery during the time we were out and finished 53 minutes before I checked on our return?

 

[Raul]

So, are you saying that the solar was continuing to charge the battery during the time we were out and finished 53 minutes before I checked on our return?

I don’t know what time you returned. But, after you parked up and alternator stoped, yes the solar continued as long as there was solar output. It does not dead stop like hitting the wall. It trickles in till dark. If shunt registers solar coming in even few watts, it counts as charge. Your 58 mins count from the moment that no power flows to battery.

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[acropolis22]

I don’t know what time you returned. But, after you parked up and alternator stoped, yes the solar continued as long as there was solar output. It does not dead stop like hitting the wall. It trickles in till dark. If shunt registers solar coming in even few watts, it counts as charge. Your 58 mins count from the moment that no power flows to battery.

Ok, thanks, I'm starting to understand, I think... Does a load drawing current during this time change how the Victron perceives the charging situation ?

 

[Raul]

If the load is smaller than the charging output, does not count. The shunt only sees the power in to count for charge.EX your solar puts out 20w, the load takes 15w out of it, and the remaining 5w makes it to the batt. That 5w the shunt sees as charge, and counting. If the load is greater than 20w, like 30w, it will take the 10w difference out of the battery. At this point, the shunt registers as 10w discharge.

 

[Lyrick]

I bought the same battery 2½ years ago and it's been great so far, the voltage doesn't drop past 12.9 until we'll into the evening. Should be OK charging at 20 amps. I bought a 10 amp charger with the gel profile for ours.
How big is your B to B charger?

Realised after I posted that maximum current from my B2b is 25 amps so no problem there