Iverter and Solar Power Questions:Help Appreciated

Unyalli wrote:
Regardless of grandstanding, diploma bloviating, etc.. off grid is about batteries.

Don't know what the first part was about - up to etc.

Offgrid is about batteries, yes. Or - about staying within one's energy budget, if generator run time is to be minimized. The rest is only partially correct.

Morningstar chargers have never been a "standard" for small system. There are other good choices, and there have been, for long time.

Midnite controller is not a cost-effective solution for a small solar because of ... its cost, pun intended :). Be it with or without monitoring add-on.

Exiting Absorb based on the decrease of charging current to certain value is not a "guessing".

FLA normal cycle life for most people is of little importance because it ages before due number of cycles, or because they kill it by not knowing what they are doing.

Unyalli wrote:
FLA's should never be depleted more than 50%. Want them to last don't go below 70%. AKA 30% used.

BS. Old wive's tale. For the vast majority of campers, the battery is going to die due to age, not cycles.

Only 4% of campers do over 30 days per year. The majority camp less than 15 nights. And even fewer if only considering boondocking.

You can find pessimistic estimates for generic deep cycle lead acid of 200 cycles @ 100% discharge. Then look at a premium battery - Trojan Battery's literature for their SPRE 06 255 solar battery (same size as a T-105) shows a life expectancy of about 1900 cycles @ 50% discharge, and about 1200 @ 80%.

The inexpensive Interstate GC-2's sold by Costco are supposedly 650@80.

So, take the extreme high end of 30 full battery cycles per year, and use the pessimistic expectation of only 200 cycles of lifetime, and that's still almost 7 years. Not many RV batteries last longer than that regardless of how well they're treated (now someone will describe their 20 year old battery bank).

But let's say, age and cycles combined, the battery lasts 6 years instead of 7. We did that by limiting how much battery capacity we used - 50% instead of 80%. So, over those 6 years, we avoided using 30% of the available capacity to save (7/6=1.17) 17% in battery cost. It's still a false economy.

Use more realistic figures, and things only get better. Use the Interstate 650@80 numbers, and that's over 21 years. Cycles and depth of discharge simply aren't a significant factor at that point. Even a battery on constant float charge isn't going to last that long.

Now, if you're talking about the common 12V "marine deep cycle", all bets are off. Plan on buying one every 3 years regardless (longer with a good solar controller to keep them constantly happy).

Additionally nothing wrong with a hybrid system. If your inverter is an advanced inverter/charger like Magnum MS2012. You can bulk charge in the morning simultaneously while running coffee pot or microwave (not at same time on 2000 watt generator) via cost effective generator like Champion inverter generator. 30 minutes quiet inverter generator will make up hours of low capacity solar while everyone else is making noise waking up.

Regardless of grandstanding, diploma bloviating, etc.. off grid is about batteries. Power used has to be replenished. When solar/wind/hydro is not providing power your battery bank (tank) is. 12 volt DC or 120 volt AC via inverter regardless. You have to put this power back into the tank. Knowing the status of your tank is paramount. FLA's should never be depleted more than 50%. Want them to last don't go below 70%. AKA 30% used.

I would not blow money on a stand alone battery monitor like the trimeteric. Back in the day when morningstar was king this was mandatory. When advanced solar battery chargers (solar controllers) included this it was no longer valid. Midnitesolar, is the only one with this in a small cost effective "controller" the Kid.

If you have studied 3 stage charging you have found ending absorb correctly is the issue. ALL "controllers" do this by guessing EXCEPT Midnite and Magnum. Monitoring battery via shunt allows these "chargers" to end absorb via real data.

I would expect Victron to do this and if they do it is hidden in collegiate (obscure) documentation.

- Jeff

Unyalli wrote:

Do you monitor your fuel gauge in your car?

There is no need to monitor car fuel gauge because the gauge IS the monitor :)...

My battery "fuel" is monitored, though not by standalone monitor. See, some solar controllers are doing this better than others. Very detailed multiline/multiscreen display. Every evening it gives me report for the day, telling whether the Absorb stage was reached, how long it stayed in Float afterwards, and was the switch to Float triggered by charging current drop or timer-activated. And, of course, battery voltage during any time of day or night.

Big solar, big battery (relatively to my needs). As a result, 90% of time the morning SOC is so high that it goes in Absorb well before noon. I don't even check the daily report more often than twice a week (available in the memory for 30 days).

One reason why I put this in the last place for the OP was that she already has too much on her plate, and their stated energy needs are minimal. Solar with voltage on display could be all they need.

There are monitor-ish gizmo for cheap, ~30 bucks on Ebay/Amazon, if you know what to look for. Learning takes time. When there is that much to learn, it will take much time. Better to start doing something.

Agreed with what time2roll said - you can buy a pair of batteries for the cost of Trimetric monitor.

All right, I feel like I'm gaining a bit of understanding on solar power, batteries, and inverters. I've written down the information about our coach batteries, and when the rain stops I'll run out and check the info about our solar panel.

I appreciate how each of you has taken the time to help out in easy to understand language.

Unyalli wrote:

Almot wrote:

Battery monitor is nice to have, you may always add it later.

Opposite!! Off grid is all about batteries. If you don't understand battery health, ....

Do you monitor your fuel gauge in your car?

For the price of the monitor most can get two more batteries and not worry with the extra capacity. Less need to monitor the tank if it is twice as big.

Almot wrote:

Battery monitor is nice to have, you may always add it later.

Opposite!! Off grid is all about batteries. If you don't understand battery health, ....

Do you monitor your fuel gauge in your car?

cruising spud wrote:
So, just when I thought I was becoming an invertor pro, I realized that now I have to go on to "Understanding Batteries, 101." :)

I am going to come away from this with a lot of new information.

I'm glad we are not leaving for our bit trip until the summer. I certainly have the time to learn.

Thank you, one and all.

I'm with you. Once my solar learning became secondary to power learning it all opened up. Understand, power is not pushed, it is drawn.

- Jeff

...a 12vdc power supply. Is this the same as an inverter?

No. Completely opposite.

Generator people are confusing everybody when substituting the term "inverter" for "inverter-charger".

Don Piano is right, you need an easy read on the subject, before starting making fireworks. And maybe do it in baby steps. Install solar first. Then - inverter Morninstar 300.

Another way would be getting 100W solar suitcase that needs no installing, and install Mornigstar 300. Not financially efficient, but easier for beginners.