Charger settings when multiple charging sources are in use

[gmanInPA]

After reading the stickies that Sunking wrote mentioning ignoring the 3-phase charger settings... I am wondering... with a hybrid system where the inverter can charge the batteries as well as the charge controller(s), would there be any consequences of having the inverter charger use more typical 2 or 3 phase charging in addition to the CCs following a "maximum smoke" pattern (if I understand that properly)? The inverter and CCs could alternate moment-by-moment based on the available PV and grid power - would that have a negative impact on the batteries?

If so, I can set my inverter to simply not charge during any block of time so that it only allows CCs to charge.

[sensij]

With better hybrid systems (Outback, Schneider, etc), the components can all talk to each other, so the charge settings can be set in one place and match for all components.

If your system is more ala carte, and you set the charge stages differently on each component, it shouldn't really hurt but I'm not sure what you gain. In any case, you'd need to make sure the battery is big enough to accept the combined charge current it could see during the bulk stage... both the charge controller and inverter will be pushing whatever they can. If you have two stage (max smoke) charging on the CC and three stage charging on the inverter, for example, assuming both have the same absorb voltage set but the inverter has a lower float voltage, the inverter will drop out of the charging process once it thinks absorb is done and CC will continue to try and hold at that higher voltage while the sun is still out.

More fundamentally, I'm not sure why you would choose to discharge the battery when grid power is available. The more common hybrid scenario is as backup for when the grid goes down, so the inverter and CC would not usually be charging at the same time, except when recovering after an outage. If the inverter charging is fed by a generator, not the grid, the question becomes more plausible.

[gmanInPA]

With better hybrid systems (Outback, Schneider, etc), the components can all talk to each other, so the charge settings can be set in one place and match for all components.
...
More fundamentally, I'm not sure why you would choose to discharge the battery when grid power is available. The more common hybrid scenario is as backup for when the grid goes down, so the inverter and CC would not usually be charging at the same time, except when recovering after an outage. If the inverter charging is fed by a generator, not the grid, the question becomes more plausible.

Thanks sensij - I have the Schneider XW4024 inverter. As you mention, the chargers can be synchronized to provide the same settings. However, Schneider instructs to have the inverter's charger be set to use a 2 phase charge cycle in some scenarios - such as grid sell back (I am going from memory). So let's say I had the grid down for 10-12 hours, which isn't uncommon around here when some drunk runs into a phone pole, or storms, etc. I've been running my CCs using the factory settings for 3-phase charging cycle. However, Sunking had some pertinent advice about chronically undercharging your batteries with PV if you followed such settings, vs using something closer to EQ voltage to maximize as much power as possible during sun hours.

So let's say the grid is back up and my batteries are at 75% DoD... the morning sun hits the panels and like many PA days, it's cloudy here and there.. The inverter would prioritize DC power over AC power for charging because... that's what the inverter does - except for low sun conditions.

Most often, I have enough to sell and want to use all the PV I make. So I don't want the inverter set to three phase charging to match the CCs (also Schneider hardware). Yet, if they CCs and inverter alternate between themselves during cloudy conditions, I also want to make sure that the switching of charge rates rather frequently won't do nasty things to the batteries. Make sense?

[sensij]

I'm still not following you. Perhaps you could suggest a specific combination of settings that might create the alternating effect you are worried about. In bulk charging, it would not hurt if clouds caused the charge rate to fluctuate. In constant voltage charging (not bulk), the charge rate will follow from the voltage, which is constant, so it doesn't matter how many sources are involved, the current is limited.

The max smoke model is really intended for daily cycle applications. In a backup power situation, where the batteries aren't cycling daily and will typically have plenty of time to complete a charge before they are called on again, it is better to have a proper float voltage for long term life.

[gmanInPA]

...

The max smoke model is really intended for daily cycle applications. In a backup power situation, where the batteries aren't cycling daily and will typically have plenty of time to complete a charge before they are called on again, it is better to have a proper float voltage for long term life.

sensij the above actually answers my questions - thank you! I suppose I could have just asked of there was a scenario where the max smoke model was appropriate for a backup power arrangement.

[Sunking]

Thanks sensij - However, Sunking had some pertinent advice about chronically undercharging your batteries with PV if you followed such settings, vs using something closer to EQ voltage to maximize as much power as possible during sun hours.

That is for batteries being charged with solar and daily cycled. You will not be discharging your batteries or charging from solar, Your batteries will be in Float 99% of the time collecting dust.

[gmanInPA]

...Your batteries will be in Float 99% of the time collecting dust.

Ok, to be fair... More like 85% of the time. And whenever I have no power, the pv could contribute. If it's not often enough to warrant the smoke model, so be it. That's what I was trying to determine. Thank you Sunking for writing that article and for taking the time to reply to my question.

[Sunking]

Ok, to be fair... More like 85% of the time. And whenever I have no power, the pv could contribute. If it's not often enough to warrant the smoke model, so be it. That's what I was trying to determine. Thank you Sunking for writing that article and for taking the time to reply to my question.

No problem and to comment further you can take something away for the Sticky. Quit using your volt meter to determine battery health. Volt meters are completely useless in that respect. They only tell you when things have gone wrong and it is too late.

Buy you a good temp compensating hydrometer for less than $10 and learn how to use it. It is the only way to determine battery health in real time. If the specific gravity is too low, turn up the voltage. If the specific gravity is too high, turn down the voltage. So instead of setting the voltage to some number in a book, let the hydrometer tell you what the right voltage is. Take note most battery manuals specify 2.35 to 2.45 volts per cell. That is 56.4 to 58.8 volts. What they mean is use a hydrometer and the voltage should likely fall in that range.