Couple of Questions

Bignewsantafe · August 2020

Q#1,I have the TriStar MPPT 60 and in Live View in Night mode it shows Charge Current @ -0.1 A. Does that mean there's a 100 milliamp drain on my battery going back to the PV's? No other loads on the battery except the CC.
-0.1 A

Image: https://us.v-cdn.net/6024911/uploads/editor/ps/z41mym7q9bwr.jpg

Q#2; I have 1 DNS account and can log into one of my TriStar MPPT 60's over the web but can't log into the other. Anyone tell me a way to setup to view both? "xx-xxxxxxx.myddns.me" example of the URL.

Photowhit · August 2020

They are designed not to allow power to backfeed the panels, much more likely the cost of running "Live View"!

I would be much more worried about the battery temp of 28 degrees Celsius or 82 degrees Fahrenheit in the evening. Guess they aren't where they are protected from the environment, perhaps in California with the inordinately hot temps? If it's a regular thing, I'd try to build a berm shelter for them to help keep them cool. Odd it's just a few degrees hotter than mine tend to get in the summer, but that 80 degree mark always seems like a red caution light to me.

Bignewsantafe · August 2020

Photowhit, thank you for the reply. Currently my systems are temporary and experimental, as I plan on moving next spring after retirement. I live in south central Washington state and when I took the snapshot of the live view the temperature in the garage was 85*F. The batteries are Saft Nicad SUN 735's, two banks of ten. Temp's don't get much cooler that that here in the summer. It's 18:48 here right now and the battery temp is 29*C.

Photowhit · August 2020

My mind fails me, I'm about to sleep or I'd look it up, but I don't think NiCD's are as efficient as Lead Acid, so the act of charging/discharging may heat them up more. I also don't know if this degrades them, I know they do better in the sub freezing, perhaps less affected...

I know my Lead acid forklift battery seemed to stay near the median temperature while outside protected from the sun. I haven't checked though in at very least a couple years. It's just a couple clicks of the button to check and they are requiring more distilled water as they age, bet they are getting warmer. Something for me to check!

mike95490 · August 2020

I use NiFe batteries, nearly the same as NiCad, but much less toxic.
They are about 70% efficient at best, but being less energy dense, they have more surface area to dump the heat out of.

Bignewsantafe · August 2020

Not wanting to get off subject here I've noticed most solar users are using lead acid or Lithium-ion and I image it because of cost? Mike after doing a search on NiCad vs NiFe I came up with this good read on the NiCad's.
https://en.wikipedia.org/wiki/Nickel%E2%80%93cadmium_battery
From this wiki it states that the "Vented cell NiCd batteries have long lives (up to 20 years or more, depending on type) and operate at extreme temperatures (from −40 to 70 °C)".
We all know that heat is any battery biggest enemy! Back in the 80's I worked 8 years in the battery wholesale/resale business and for the 33 years after that in low voltage safety and comm systems that are power primarily off lead acid and NiCad batteries. And no, I'm still not a expert!
Anyhow back to question #1, I kind of figured that the MPPT 60 had a diode to prevent back feeding the PV's, as one was usually installed in the earlier systems.
As for question #2, any network/wed Guru's on the list?
Thank you for listening.

BB. · August 2020

NiCad batteries were the "best" rechargeables out there for upwards of a 100 years. Very high discharge and charging rates supported, relatively light weight, and very forgiving for difficult operating conditions.

The big issue has been the Cadmium. Very difficult to use these days in most countries. And the smaller cells (AAA through D cells) were rarely recycled--Worries about Cadmium pollution ended up with lots of laws limiting their use/importation.

NiFe batteries are interesting... You have to change the electrolyte every 5-10 years--So that can be a pain (the old electrolyte can even be used as fertilizer). Both NiFe and NiCad batteries are much less efficient charging/discharging vs other chemistries.

Yes, you can use NiCad in a properly designed system... Can you get them?

Regarding "blocking diodes"--They were common in early solar systems 1970s and 1980s(?). Generally diodes were used in place of (today's) standard series charge controllers. Diodes have "losses" (diode voltage drop from 0.2 to 1-2 volts) which generates heat/loss of system efficiency.

Today's modern charge controllers use FETs or similar series transistors instead of any diodes in the current path for better efficiency. The controller simply "turns off" the transistor(s) to stop current flowing back into the solar array.

Note that solar panels still use lots of "bypass" diodes to prevent damage/possible fires if there is shading on a solar panel in a string of 2 or more solar panels (solar cells go "high resistance"--Need bypass diodes to prevent damage to shaded cells.

AGM (still lead acid) and LiFePO4 batteries are the "better" ones available today for off grid power systems. But they are more costly.

AGM seem to have slightly less life vs flooded cell lead acid batteries of the same quality/lower price. But maintenance free--Always nice.

LiFePO4 are relatively safe and have very high discharge/charging current support. Darn near perfect for off grid power. However, the need for a battery (cell) management system makes things more complex. Running LiFePO4 cells outside their "approved" voltage range (over charging, over discharging) can quickly ruin a cell/battery. A BMS can shutdown the bank before damage happens. And some can "balance" cells to keep all at the same per cell voltage.

Other Li Ion chemistry type cells can have higher energy density, higher current support and such... But those cells, if misused can vent or be set on fire pretty easily--Definitely not the first choice for an off grid power system that needs to be setup and run without much manual monitoring/maintenance.

-Bill

littleharbor2 · August 2020

BB quote,
"AGM seem to have slightly less life vs flooded cell lead acid batteries of the same quality/lower price. But maintenance free--Always nice"

This statement, while true when referring to a "well maintained" set of lead acid batteries, I feel the need to add that I feel a set of poorly maintained LA's will live a considerably shorter life than a set of AGM"s in many cases. I got a solid 5 years out of my last set of AGM's and now that I'm here in Baja full time I see that this time of year the temps don't want to get below 90 degrees, OVERNIGHT. It's been brutal.

Couple of Questions

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