Terminology

[rgswaim]

I guess I really don't understand all the buzz words and acronyms and such. I know what amp, ohn, volt and watts are. The battery stuff leaves me blank. What does cold cranking amps mean? What about amphour? I recently swapped my 115 ah battery for an 85 ah battery on the advice to get a smaller battery. I am using the Harbor Freight kit. The 115 ag battery was holding at about 12.8 volts. The 85 ah battery started at about 13.2 volts and now is holding at 12.4 volts. Was the 115 am a better battery? Same brand, CostCo deep cycle marine battery.

Also. Is there a charge controller that displays the battery voltage AND the output coming from the solar panels? I bought a Stanley amp/watt display. I can get amps to display but when I switch it to watts it stays at zero. What would be a better unit?

[RussN9ZP]

I would of kept the 115ah battery. Would take longer to charge but still get more capacity.

[green]

Hang in there, the more you read the more this stuff starts to sink in. I'll give you some basic answers, these guys can give you much more in depth and sometimes confusing answers. If you see Cold Cranking amps listed it is an automotive battery and is not suitable for solar. Amp Hours is basicly the capacity of a battery. Now I know these guys here are going to tell you that the Harbor Frieght units were a waste of money, but I applaude your efforts and your willingness to learn.

Best of luck,
Green

[Sunking]

CCA = Cold Cranking Amps. Which is a theoretical lab test of amount of current a battery can provide at 0 °F, fully charged, for 15 seconds, at 7.2 volts for a 12 volt battery. Basically the battery internal resistance. Starting/Cranking/SLI batteries are not suitable for RE Deep Cycle applications. If your battery has a CCA or MCA rating, you do not want it.

Amp Hours = the battery capacity usually specified at the 20 hour discharge rate. It is a terribly complicated math formula that takes 12 years of US college education to under stand. 5th graders in any other country. Amp Hours = Amps x Hours.

So let's say you have a 12 volt battery rated at 100 AH @ the 20 hour discharge rate. If discharged at the 20 hour rate (100 AH / 20 H = 5 Amps), the battery if fully charged can supply 5 amps for 20 hours until fully discharged. So the formulas are:

AH = A x H
A = AH/H
H = AH/A

Note if discharge at a rate other than 20 hours, Peukert Law must be applied. That is another 20 years of college for USA students, or 6th grade math in any other country.