Battery/Solar Cell Question

[rgranger]

When do you need a regulator on your solar cell and when do you not.

In the past I have used with success, the trickle chargers you see sold for car and RV batteries. The cell was rated at 12V and 1.5W. I didn't use a regulator and everything worked fine. The solar cell could not over charge the battery (I guess because the voltage was not high enough).

But I recently put a bid on a 40W 17V cell and now I'm wondering if I need a regulator?

I'm thinking yes? But I'm no EE, so...

Anyone know the boundary limits here?

Thanks in advance,

r

 

[Mike B1026]

Yes, you should have a controller. Are you using one or two batteries? Type?

 

[Sumner]

Agree with Mike. We started with a 40 watt and had good luck with this inexpensive PWM....

http://www.solarblvd.com/Charge-Con...,-12V-Pwm-Charge-Controller/product_info.html

...charger. Then we added more (have 180 watts now) and went to a better MPPT, but for the 40 that would be overkill. We bought everything from the guys in the link and have been happy with them and the products. I don't know what you are bidding on the 40 watt but they have the one we bought....

http://www.solarblvd.com/Solar-Pane...40-Watt-12-Volt-Solar-Panel/product_info.html

...at $135.00. We love the solar we have now,

Sum

Our Trips to Lake Powell, UT - Kootenay Lake, Canada - Priest Lake, ID

Our Mac Pages

Mac-Venture Links

 

[Ron20324]

As a starting point, the West advisor suggests if the charger exceeds 1.5 percent of the battery bank's rating in amp-hours, you'd want a controller. So, it depends on your battery(ies) capacity.

 

[mccauley13]

Took Sum's advice last year on the 40 watt and haven't stopped smiling since. His take on solarblvd is dead on. They are good folks and do not try to oversell.

 

[rgranger]

As a starting point, the West advisor suggests if the charger exceeds 1.5 percent of the battery bank's rating in amp-hours, you'd want a controller. So, it depends on your battery(ies) capacity.

Thanks everyone

Ron Do you mean 1.5% of voltage rating or watts? I'm not clear on what you mean hear but it seems like something I should understand.

Help?

 

[Mike B1026]

Ron said "amp-hours" (of your battery or battery bank)

 

[rgranger]

Ron said "amp-hours" (of your battery or battery bank)

Okay

Well I did not win the bid on the 40W cell but I got a 12V cell @ 5W for 6.99 + 20 shipping.


Back to this question... the solar cell comes with data like "volts" and "watts" An Amp is a watt/s and I'm not quite sure what an amp-hour means. Would that be a (watt)(hour)/s. Seem like a nonsensical unit to me but I'm guessing I just don't get it. So how do I figure out 1.5% of a solar cell that is 12V and 5W against an 180 amp-hour battery?

 

[Sumner]

Okay

Well I did not win the bid on the 40W cell but I got a 12V cell @ 5W for 6.99 + 20 shipping.


Back to this question... the solar cell comes with data like "volts" and "watts" An Amp is a watt/s and I'm not quite sure what an amp-hour means. Would that be a (watt)(hour)/s. Seem like a nonsensical unit to me but I'm guessing I just don't get it. So how do I figure out 1.5% of a solar cell that is 12V and 5W against an 180 amp-hour battery?

An amp isn't a watt. Watts are amps X volts. So if you know any two of those you can figure the other. Your panel you bought would produce about .4 amps in ideal conditions of full sun and the panel tilted directly at the sun.

An amp hour is the use of one amp for one hour. If you have a VHF radio that uses 2 amps and you used it for 3 hours during the day it would have used 6 amp hours of electricity (3 X 2). It would then take your 5 watt panel about 15 hours of perfect 100% charging to put the 6 amp hours back into the battery ( 6/.4). That would be about 2 days of sun, but in reality probably about 4 days.

On the charger, and the 1.5%, you would need the controller if the panel put out more than 2.7 amps (.015 X 180). The panel you got probably has a diode in it to prevent discharge of the batteries at night. If you would of bought the 40 watt panel and hooked it straight to your battery depending on what came with it, it might of discharged the battery at night. A charge controller, even the cheap one I posted, will not allow that to happen plus control the charging on the battery. You could buy a cheap diode and put it in the line if you knew how to do that properly. The controller would leave nothing to chance and with a single battery and a 40 watt panel I'd want the controller.

The 5 watt panel you bought would probably keep your battery up and would recharge it most-likely, but not if you use your battery very much,

Sum

 

[rgranger]

Thank Sum

I think I get it now.

r

 

[chp]

Hi Sumner
Wow that is a good price for a solar panel. I'm in the process of making my own 18v 60 watt and that will come to about $130. Do these use glass or plexi to cover the cells? Congrats on the marriage. Looking forward to hearing the rest of you Florida trip. Hoping to do the keys next year probably in February. Love all the ideas and mods. Built a very similar food storage cabinet for the port side. Hope you don't mind. If you ever make lake Ontario or Erie look me up.