Noob PV Panel ?s

[anemic]

Hello solar people!

I am designing a system for an RV. One, possibly two panels. Basis for solar charging is to replace about 100 amp hours per day as a wild guess starting place. Need to provide a winter time habitat as a ski family mobile unit. Could be anywhere, in any weather, all winter long. Weekends primarily. Up to 10 days per trip occasionally.

Shooting for about 200 watts from the panels. Confused about amps. Compare two panels:
195w 17.6v 11a
130w 17.4v 7.5a

Wouldn't it be better to have a pair of 130w panels?
Would the batteries charge at 15 amps?

In other words with two of the 130w panels would the system then be 260w 17.4v 15a?

Controller will probably be the tristar 45 pwm.

Thanks,
anemic in GR

[anemic]

http://partsonsale.com/learnwiring.htm

The above is an EXCELLENT piece on series & parallel installation basics. If I'd seen it earlier I might not have posted my questions.

Watts is not addressed however. What happens with a panels watts in a series install? a parallel install? AHA! I used W=A*V (wave!) to answer the question of watts. Watts in either case are additive, doubled, 130w becomes ~260w. so proud of myself.

However, I still invite your opinion on charging - isn't it quicker to have panels charging at 15 amps instead of 7.5 amps? That seems pretty obvious to me. How do you calculate charge time? 7.5 amps to replace 100 aH is 13.3 hrs. 15 amps is 6.7 hrs.

Seems about right. I will not know if I actually burn 100aH till real life happens.

Thanks for letting me think 'out loud!' Perhaps others have thought thru this with more brainwatts than that w/which I was blessed.

[Mike90250]

Yes, the learnwiring.htm link is good, for the math theory behind series & parallel.

Their connection diagrams are lame though, they don't address the "micro ohm" issues that cause battery imbalances.

I'll quote myself from an earlier post:

If you have more than one battery, read up on connecting on the "diagonal"

Inverter and Charger connect to the same terminals.

Here's a great article about connecting batteries in parallel (on the diagonal)
http://www.smartgauge.co.uk/batt_con.html (connect batteries on diagonal )

and some other battery stuff:

http://www.windsun.com/Batteries/Battery_FAQ.htm (short & sweet)
http://www.batteryfaq.org/ (very large)

Generally, much easier to manage 2, 6V in series, than 2, 12V in parallel. Same wattage.

Don't forget a fuse on your battery, I love the simple and compact MRBF terminal fuse by blue sea (MRBF - Marine Rated Battery Fuse)

Get the fuse & holder.

[anemic]

wow many thanks Mike! that kept me busy for a while. Would you use the bluesea battery terminal fuse block in lieu of, or in addition to a shut off style fuse box (similar to the fuse boxes for my home a/c & the hot tub)?

I really liked the smart gauge site & smart gauge itself. That guy has a huge depth of info thanks again

[Mike90250]

I use the fuse at the battery, and you can use any DC switch/breaker anywhere else. I have my 300W sure sine inverter ON always, and have a simple light switch wired up to disable it's control line if I don't need power for several days.