Published Date 10/01/16 20:06
The only time you can get a “true’ish” reading is after they have been sitting without charge in or out for a few hours. The rest of the time it's a “ruleofthumb” reading, you need to get used to this.
Don't go lower than 12.2v if you want your battery’s to last any time and 12.4v would be sensible cut off point to extend their life.
If you have limited power generation you need to run your battery's on full rather than empty. Otherwise your paying out big time in a year or less. It's normal that everyone wrecks their first set of batteries. Learn from this for the next set, this is a first step for new boaters.
You're living on a boat not a house, you can't just turn the lights on without thinking about all the above. The sooner you get used to this the sooner you can let it drift to the back of your mind.
Happy boating, my your lights shine bright and your laptop be fully charged.
Ps. Ignore anything beyond this as it’s likely to do more harm than good. Pss. Does not apply to geeks.
More info http://hamishcampbell.com/en/home/-/blogs/basic-boat-12v-electrics