Solar generator questions

1911 · August 2019

Hello,

I have six walkie-talkies (4w uhf) that I would like to build a portable battery bank/solar generator for. I would like to make it a bit oversized as I plan to increase the number of radios in the future.

The batteries in the radios are 7.4v, 1600mah.

I already have some componets from a project I was planning on making a few years ago.

I have:

- 1 x 150w Kyocera solar panel (not sure of the specs, currently burried in garage somewhere).
- Morningstar Suresine 300 inverter
- Morningstar prostar-30 12/24 charge controler

I envision building the battery and componets into something like a Pelican 1440 case.

i was thinking something like a Trojan 24agm battery would work....it seems to be about the cight size to fit in the case and appears to have plenty of capacity for what I need.

Am I headed in the right direction with these componets?

If this setup appears to be the right size, I plan to follow up with numerous wiring and fusing questions:)

thanks in advance for any assistance.

Estragon · August 2019

The battery is 76ah x 12v = 912 watt-hours. The radios would take ~ 1.6a x 7.4w x 6 radios = 71wh ÷ .8 for inverter losses = ~90wh, so roughly 10% of battery capacity per charge. Taking a lead acid battery to <50% will shorten life expectancy, so about 5 charges for the 6 radios.

The 150w panel will likely produce ~100watts in normal operating conditions and full sun. Charging the 50% discharged battery would take ~3-4hrs of full sun and no other loass to get to ~85%, and another couple of hours with diminishing current to get to full. Likely doable in most places (ie not in a high latitude winter, etc).

Overall, a reasonably sized system for what you want.

For the battery, you may want to consider a lithium for reduced bulk and weight, and unlike a lead acid most are fine sitting at partial states of charge.

1911 · August 2019

Well, back to the drawing board.

The panel I had burried in my garage that I thought was 150w....turns out to be an 83w Kyocera. And I can’t find any of that particular model any more.

Unfortunately, I have already ordered a Sun Xtender PVX-840T.

So I have either an oversized battery or an undersized solar panel.

What would you solar gurus do?

As stated by Estragon, the radios will require about 90wh per charge. i could potentially need to charge them daily, although probably not all of them, and they will likely not be fully depleated.

Will the 83w panel be enough to get it done?

Eta-....or should I stop being cheap and just buy a new panel?

mike95490 · August 2019

Buy a 300w panel and a MPPT controller and never think about if it's going to be enough !

Estragon · August 2019

It may work okay if you're only charging 1x daily. After a couple of cloudy days and a couple of 90wh radio charges, the battery might be ~80%SOC. With good sun on the third day, you may be able to get back to full.

Mike is right though, a bigger panel and mppt controller gives more flexibility and less worry about charging capacity. You really should have pv capacity for ~9a into the battery, but you only have 3-4ish.

A 300w panel is pretty big, needing two people to move safely.

1911 · August 2019

Thanks for the replies.

if I order a pair of Solarland 160w panels.....how handicapped will I be with the Prostar 30 pwm charge controller vs buying a new mppt?

BB. · August 2019

Assuming the panels are "12 volt" (Vmp~18 volts), the array to controller wiring is relatively short (10 feet or so), and the controller is mounted close to the battery bank (short heavy wiring from controller to battery bus for low voltage drop and accurate voltage reading by charge controller during charging)--You will not not lost much of anything (energy harvest wise).

Just keep the controller and batteries in shade/well ventilated area... Heat is the enemy of electronics and batteries.

-Bill

1911 · August 2019

Thanks guys....one more question, if you will indulge me....I am giving up on using my Prostar 30 cc and Puresine 300.....I will save those for another project.

Here is where I am at today.....I want to go anead and use the 83w Kyocera solar panel I have....so here is what I added to my cart at NAWS.....please let me know if this is a good combination of components, feel free to suggest any substitutions

-Sunsaver 10amp cc

-Exeltech 125w inverter

- Sun Xtender 42ah battery

- ???Midnite Solar Battery Capacity Meter??? (Do I need this?)

thanks in advance:)

eta-i am assuming I can safely get 250wh from the battery which will charge the radios twice. And the 83w panel should be able to charge the used 22 amps in a days time.....am i right?

the ability to charge the radios twice before needing to recharge is sufficient for me...as a matter of fact, the reason I have six radios is so that three can be used while three are charging....so really, this battery size will probably get me closer to four charges for the used radios....so, probably enough of a buffer for bad sun days.

mike95490 · August 2019

get a larger controller, 10a gives little room to grow if you decide you need more panel.

Solar generator questions

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