Quote:
Originally Posted by DocMike
Then to figure how long one could run the example above, you would divide the 4.5 amps into the cold cranking amps (?) available from the house batteries?
|
No... the Cold Cranking Amps (CCA) is a measure of how many amps a battery can deliver for 30 seconds in cold weather (0 degrees F) and maintain at least 1.2 volts per cell (7.2 volts for a 12 volt battery). While it may help compare the starting power between batteries - not going to help here..
(MCA - or Marine Cranking Amps is the same test at 32 degrees F... guess they figure 0 degrees doesn't mean much to boaters - other than you might need an ice breaker on the front of the boat.)
For your calculation, you need to know the amp hours (AH) the battery can deliver. To be nice to a deep cycle - you don't want to regularly drive it below 50%... so conservatively the calculation would be:
(battery capacity in AH) / 2 (to get 50%) / (anticipated amp draw) = hours expected
If an 90AH battery and 4.5 amp load - and being kind to the battery you would have 90/2/4.5 = 10 hours... (plug in your actual battery value...)
For two 12 v batteries in parallel (to deliver 12 volts) - you add the AH of each battery (90+90)/2/4.5 = 20 hours...
For two 6v batteries in series (to deliver 12 volts) - you use a single batteries value and formula.
Thor Forums
