Interesting sticky topic i found on solar charging

Hi,

All the article referenced by this thread says is "don't use factory settings, if you wish to maximize charging".

Here are my thoughts on solar and batteries:

https://freecampsites.net/adding-solar/

FordDiesel250 wrote:
I am so confused by all of this

I didn't see that he said to jack up the voltages to make up for too small an array. He says you can't have a set-up that is adequate every day all year, so do the best you can with what you have. So on a day when you are not going to get it done before dark, don't let it drop to float and waste any of the sunlight you do get before dark.

Actually he says the same as what people on here have been saying for several years now. Didn't see anything new.

I haven't done solar on AGMs where you can't use an hydrometer to check results. Nervous about that, if I ever do it.

I have found you only need to do the hydrometer check to confirm when "full" is by my AH count and voltage behaviour, you don't have to use it all the time like he seems to be saying. Once you know when full is, you can ASSume it will stay there for a while and just use your other indicators.

I did not reset the Trimetric for its default heat loss allowance, so in my case it needs to go "over" by about 15 AH into positive numbers. There, the SG shows it has caught up close enough to Baseline Full, and now it is time to drop to Float, not before that. (This can happen mid-afternoon or not at all on any particular day depending on clouds and season.)

I like that the guy says solar conditions are always changing day by day even, and you need to keep an eye on things. Seems like he has BTDT.

As others noted, the author is trying to "goose" his charging capabilities rather than having a good, initial setup. Also, I can't think of a more accurate way to measure the characteristics and charge level of SLA batteries than taking hydrometer measurements from the time when installed to current use.

FWIW, I've found that higher voltage charging, particularly for 6V GC2 batteries brings the best results. I have my solar controller, temp compensated, at 14.8 for Abs and 13.6V for float. When in storage, the controller only briefly stays in Abs and then reverts to the float voltage. There are settings in the software where different voltages and durations can be set. Setting the low state of charge set point to make the controller come out of float and into Abs is also available.
In the Winter, I sometimes find the controller has the batteries up to 14.9V. They seem to thrive at the higher voltages for that small window of time.

I am so confused by all of this

Yes Lithium will operate normal using 80 percent capacity and tolerate 100 percent periodically with no ill effects.
All chemistries.

Discharge to zero volts and you have an instant doorstop. Most have controls to prevent catastrophic over voltage or under voltage.

2oldman wrote:
I'm moving to Li which doesn't care if it's undercharged. Perfect for boondockers.

I got tired of the author misspelling 'manufacturers'.

The most common lithium-ion (LCO) batts may be fine with receiving partial charges, but (as I understand it) they are still subject to damage if discharged too far (someone correct me if I'm wrong). But then, just the other day I heard someone claim that LiFePO4 will withstand deep discharges much better. Anyone know if that's true? And what about LMO (lithium manganese oxide)?

Not enough solar to get to Vabs early enough in the day will cause defecit charging, as absorption takes a lot longer than most who do not bother checking with a hydrometer, will ever realize. The time also increases as the batteries age.

Instead they believe a blinking green light which only indicates absorption voltage was held as long as programmed to do so, Which could be very very wrong in a given usage, but more likely to be wrong the deeper the discharges, or the more partial state of charge cycles that have accumulated since the last actual full charge.

As chronic undercharging is not an obvious instant death, out comes the 'just fine' brigade who will claim X amount of years from their batteries and break their arms trying to pat themselves on the back when perhaps their system is only used 2 dozen times a year.

Off grid/ daily cycling is a whole different beast, and the Sticky author, gets it. Without the ability to add more solar, the battery bank's worst enemy is a prematurely initiated low voltage float stage, and a complacent human who believes a blinking green light somehow knows when their battery is full, when an actual measuring tool (hydrometer) would likely reveal a battery bank no where near 1.275.

But most rv's get to go home, plug in for a week and even 13.2v should get the batteries full if applied long enough, or if not plugged in, the existing solar will then be able to top up the batteries which were not significantly diacharged the night before.

Such users regularly report years of 'just fine' service from their batteries, but if they were full timing, their recharge regimen would be anything but, and short of adding more solar/ applying other charging sources, or using less electricity, the best solution for extending longevity would be to raise float voltage to ABSorption voltage as a premature float stage helps kill lead acid batteries, and is doing so right now, somewhere.

pianotuna wrote:
Hi,

Damage to electronics may occur at 15.4 volts, so limit the upper voltage to 15.3

brulaz wrote:
Have heard concerns elsewhere that these higher absorb voltages like 14.8-14.9V might be hard on trailer electronics. Especially as temperature compensation can raise them well into the 15's.

Not to derail the thread but I'm curious if anyone has a proven electronics failure at these voltages? Zener regulation possibly maybe, but you will smell the resistor first. Chip regulation usually closer to 20v +

While some ideas have merit... Sounds more like he is compensating for a poorly designed system.

Hi,

Damage to electronics may occur at 15.4 volts, so limit the upper voltage to 15.3

brulaz wrote:
Have heard concerns elsewhere that these higher absorb voltages like 14.8-14.9V might be hard on trailer electronics. Especially as temperature compensation can raise them well into the 15's.