Opinions on my battery charging profile (solar)

[ewarnerusa]

I am curious about what others with battery charging expertise think about what I'm doing to my batteries. Am I damaging them or shortening their lifespan?

Quick background, I installed 280 watts of 12V solar panels with a fully programmable Morningstar Tristar 45 controller on our new TT in 2012. At max sun I can see 15A from the panels. It had OEM 2x12V batteries that I swapped out for 2x6V Costco GC batteries in 2013. I installed an inexpensive ebay 1500 watt PSW inverter in 2013 that does not like to operate at voltages above 14.8-ish volts. So I've utilized the programmable features of my Morningstar to accommodate this, but I'm wondering if my batteries will suffer from not enough 14.8V+ charging.

My normal charging profile has 14.4V for the bulk and absorption setpoint. It will drop from absorption to float when PMW duty cycle drops to <15% for 10 minutes. I have voltage sense wires and temperature compensation, but I have it programmed to not do the temp compensation at lower than 70 degrees F. This is because I don't want the controller charging at higher than 14.4V during normal use so it plays well with the inverter. I have also programmed an "equilization" to occur every third day at 14.9V with the same temperature compensation cutoff. So when the sun is bright I hit the batteries with up to 14.9V for 3 hours every 3rd day. My logic is that this at least gets the batteries some 14.8V+ time while hopefully minimizing the impact on being able to use my inverter. During winter storage, I change the temp compensation cutoff to much colder since the TT/inverter isn't in use. I think it have it adjust down to 32 degrees F.

Do you think my 6V Costco GC batteries are getting enough charging to stay healthy?

Thanks.

[ewarnerusa]

Do you think I should ditch my 14.9V every 3rd day idea and go back to a more typical 15.5ish volt equalization on a 30 or 60 day basis? Or maybe even just on demand?

[BFL13]

Only if Robin Williams (RIP) drives back out of the lake in Alberta on his bicycle to save the day!

[jrnymn7]

The term "Equalization" has been hijacked by marketeers, and must now be understood according to the CONTEXT with which they now use the term.

[time2roll]

jrnymn7 wrote:
If those who marketeer chargers decide that "float mode" means you should park your rv in the lake, while charging, is anyone here going to abide by their dogma?

No marketeer, this is Morningstar where all values can be chosen at will even if inappropriate or simply to suite your own purposes.

[jrnymn7]

"Equalization" is a deliberate OVER CHARGE, done on an already FULL battery. Charging at 14.9v at anything less than a FULL battery, in no way constitutes an Equalization/over charge. If the OP is doing his normal daily re-charge routine, during the day, on a discharged bank, at 14.9v, he is only doing a typical constant voltage (i.e; abs) charge. Every three days, every 8th day, or every day, it makes no difference whatsoever.

If those who marketeer chargers decide that "float mode" means you should park your rv in the lake, while charging, is anyone here going to abide by their dogma?

Moreover, when one reads in a user manual about a charger going into "EQ mode", be it every 21 hours, or once a week, or whatever, it is referring to when the ALREADY FULL battery has been in maintenance/float mode for that period of time.

[BFL13]

Going back to the original OP issue, I have mentioned before that I was surprised this summer by my 6s not needing 15+v overcharges like before.

On a regime of 14.8 then 14.4 till dark, they did fine, reaching baseline SG enough times in the sunlight time available that they didn't need an equalize.

Mex has mentioned this effect too. It seems if you do shallow cycles as with solar, and get close to 100% often, the requirement to equalize changes so you can do it less frequently

This is not the same thing as leaving them on a 14.4 PD converter forever, where RJ says they will last ten years no sweat, but it does show that in certain circumstances, you can go without equalizing for a long time. Just be sure to use the hydrometer to confirm everything is going well. If not, then do something about it.

[time2roll]

ewarnerusa wrote:
I guess nullifying the 14.4V is what I'm trying to do since "they" say that 6V batteries in series should be charged at 14.8V because Trojan says so. But since always charging at 14.8V would mean my inverter won't turn on, I dial it back to 14.4V but try to sneak a 14.8V+ in there on a relatively frequent basis.

14.8 every three days is unneeded IMHO. Still going to be a pitn with inverter.

OK maybe better if full time. For the typical trip of 14 days or less it will not matter.

[jrnymn7]

I would take 2 minutes and verify the solar controller's display readings, by checking at the posts with a good multimeter. My Peak 40 amp portable charger would display 14.9v, when in reality it was outputting over 15.2v.

[BFL13]

With that #2 you should be good unless either there is a loose connection increasing R, or else the inverter itself is off-spec.

Repeat, I just turn off the solar before turning on the inverter and then turn solar right back on. Too easy, and I don't have to fuss about the solar set-point being too high for the inverter.

[ewarnerusa]

The inverter high spec is 15V. But it starts to fault at less than that under zero load conditions, so it I don't think it is a voltage drop issue due to too small of wiring. I used 2 gauge wire with about a 5' wire run (10' loop). The inverter won't turn on if the voltage is ~14.8V or higher with no loads attached to it. It just immediately faults. It is an inexpensive PSW from a China ebay seller, I've always thought that it faulting at 0.2V lower than it's claimed high voltage cutout is a due to its cheapness. But it delivers good enough AC power that my LCD TV likes it, unlike MSW inverter power. My small PSW inverter doesn't mind the higher voltage, just the larger one.

I use the voltage sense wires with the controller so it sees actual battery post voltage readings for use in both setpoint values and battery status. I actually don't recall if I've put my multimeter across the battery posts, but I've hooked my laptop up to the controller many times and viewed both the battery sense voltage and setpoint voltages. It seems to be behaving correctly, it accounts for about a 0.1V drop.

[BFL13]

Just to dig further into your set-up 🙂 What is the spec upper voltage cut off for the inverter? Mine are both at 15v.

If they alarmed off at battery 14.8v that would mean a voltage drop between battery and inverter (wires too thin for their length) at the current being drawn at the time by the inverter with that load on it.

In the same way, your solar controller voltage display will show a higher voltage than the battery's actual voltage depending on the current at the time on that pair of wires.

Any voltmeter inside the rig far from the batteries will also read high compared with actual battery voltage.

One of the hazards of the solar controller set-point is that it will "see" its value before the battery is actually that high if the voltage drop is not small on the controller-battery run.

Without knowing what is really the situation, from what the OP has posted about all this, I am getting suspicious the batteries are maybe not seeing the voltage he thinks they are getting, and also that the inverter-battery wiring is suspect.

Yes/no?

EDIT--RJ, it is not we "voltage fanatics" who are saying 14.8v for Trojans, it is the Trojan company! If it comes to a choice of believing Trojan about their own batteries or RJ about whatever his are, guess what? My goodness! 😞

[RJsfishin]

Your inverter not wanting 14.8 should tell you something.
In reality, batts don't need 14.8 v, (no matter what you are brainwashed into believing here) to perform well and live a long life,...I have proved that. Take a lesson from PD converters,....their mamma din't raise no dummy !

[ewarnerusa]

I guess nullifying the 14.4V is what I'm trying to do since "they" say that 6V batteries in series should be charged at 14.8V because Trojan says so. But since always charging at 14.8V would mean my inverter won't turn on, I dial it back to 14.4V but try to sneak a 14.8V+ in there on a relatively frequent basis.

[time2roll]

I think 15% is too tight. 25% to 50% should be fine IMO. Equalize at 14.9 is fine but I would go every 60 to 120 days. Every 3 days kinda nullifies the 14.4 setting.

[ewarnerusa]

jrnymn7 wrote:
Let the batteries tell you how they are doing... SG readings, tiny bubbles while charging, etc. Some batts need several hours at 15+v while others do well at 14.6v. And pay close attention to battery temperature. You may have to improve battery compartment ventilation for the summer months, even at 14.4v, to avoid excessive gassing.

I have the remote temperature sensor and while I clamp the temp compensation cold side (no compensation below 70 degrees F when it would begin to raise the setpoint), it does compensate as temperatures rise above 70 degrees F and reduces the voltage setpoint. I think that this minimizes any excessive gassing. I have to add a bit of water in the spring, but it doesn't seem out of the ordinary.