Solar on or off ?

[Lyrick]

I have a 2020 Fiat based Pilote motorhome that I keep on the drive . It's permanently on mains hook up and the charger keeps the single 100ah AGM leisure battery on a float voltage of 12.5 volts ,which is in the recommended range for this battery. All straight forward so far.

I have 120w of solar controlled by a Votronic Smart Solar controller connected directly to this battery ,which when enabled cycles the battery through a charge cycle - from float to bulk , absorption and then back to float - every day.
The absorption voltage is set at 14.5 volts in the Votronic settings. Again this is within the recommended range for this battery.

My question is this daily cycle a good or bad thing for this battery ? Should I disable the solar side when on mains hook up ?

I have tried adjusting the settings in the solar controller , namely the Re-bulk voltage offset , lowering the starting voltage at which the bulk phase should kick in , but to no effect.

I can't understand why the solar controller does this cycle everyday when the float voltage ,provided by the built in charger, is constant and does not fluctuate. I have a Votronic Smart Shunt fitted to monitor battery voltage.

Hope the above makes sense.

Patrick

 

[PP Bear]

I’d disconnect the mains and leave the solar to do its job, plus it’s free

 

[Lyrick]

I’d disconnect the mains and leave the solar to do its job, plus it’s free

Might be an option , if it would be enough this time of year.

I really wanted to know if the cycling would harm the battery.

 

[monzer]

Not sure about damaging the battery but seeing as it's easy enough to switch off the charging option of the solar panel on the app then I would just do that.

Switch it on again when unhooking from mains.

 

[autorouter]

the charger keeps the single 100ah AGM leisure battery on a float voltage of 12.5 volts

That doesn't sound right. I'd be expecting nearer 13.5V for a float charge voltage.

I have tried adjusting the settings in the solar controller , namely the Re-bulk voltage offset , lowering the starting voltage at which the bulk phase should kick in , but to no effect.

That might be because the float voltage is too low. If it's full and floats at 13.4, it probably won't drop below 12.7V overnight. So if the re-bulk voltage is set to 12.6 then it usually won't kick in.

Some mains chargers/solar controllers reduce the absorption time, depending on the time taken to reach the absorption voltage (ie the bulk charge time). If a battery is very nearly full, it only takes a couple of minutes to reach absorption voltage, so the charger reduces the absorption time. For example it could be set at 2x or 4x the bulk charge time.

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[Lyrick]

That doesn't sound right. I'd be expecting nearer 13.5V for a float charge voltage.

Sorry, my mistake, float is 13.5v

 

[Driventemple]

Last winter I left my 150w panel to keep the two AGM batteries topped up. After about 25 days it needed 24hrs of mains to get the levels up again.

 

[Raul]

It works out the absorb time based on the voltage reading when wakes up and starts a new cycle. That’s regardless how long it takes bulk to get to absorb. This is to allow for variable power coming from solar. If you have full sun, it bulks up quick, if you get few clouds, the bulk will take a bit longer. This, will not influence the absorb at all. The voltage on wake up is the guide, as it will estimate the dod, based on that voltage.

Agree that mains float of 12,5v it’s not a float. Way to low. If the solar cycles every day, and has the right settings for float and absorb, it will not harm the battery at all. It will only replace energy lost nothing more.
Seen the OP post after:

 

[Richard n Ann]

I have a 2020 Fiat based Pilote motorhome that I keep on the drive . It's permanently on mains hook up and the charger keeps the single 100ah AGM leisure battery on a float voltage of 12.5 volts ,which is in the recommended range for this battery. All straight forward so far.

I have 120w of solar controlled by a Votronic Smart Solar controller connected directly to this battery ,which when enabled cycles the battery through a charge cycle - from float to bulk , absorption and then back to float - every day.
The absorption voltage is set at 14.5 volts in the Votronic settings. Again this is within the recommended range for this battery.

My question is this daily cycle a good or bad thing for this battery ? Should I disable the solar side when on mains hook up ?

I have tried adjusting the settings in the solar controller , namely the Re-bulk voltage offset , lowering the starting voltage at which the bulk phase should kick in , but to no effect.

I can't understand why the solar controller does this cycle everyday when the float voltage ,provided by the built in charger, is constant and does not fluctuate. I have a Votronic Smart Shunt fitted to monitor battery voltage.

Hope the above makes sense.

Patrick

I'd disable the solar. It can't do the battery any good going up to 14.5 volts every day when it's already fully charged.

Our mains optimate cycles on and off 24 hrs a day at around 13.4v to minimise electrolyte loss.