battery charging basics

steveh2112 wrote:

KendallP wrote:

Otherwise, if you must go Wally, to save money you could get these. They should be made by Johnson Controls and decent batteries. The reviews say you might check the electrolyte levels before you leave the store. However, 4 reviews a decent statistical sample do not make.

But again... GC2s. Besides lasting longer, their chemistry makes them easier to top off, which requires about 15.5V or lots of time. And if you're batteries don't get topped off AT LEAST every other week, they will die a quick death due to hardened sulfate.
...

Directly off of jumper cables, alternator charging is not a terrible way to charge your house batteries, though not cheap in gas as MEX just said. The alternator will perform better above idle, though. MEXBUNGALOWS can tell you just what speed to set the throttle.

Then there's BFL13s alternator to inverter to portable charger method, which is even a little faster. He just posted that method in another, similar thread.

To do it right, without a genny, I think a pile of solar is in order. A portable that you can move into the sun is ideal. Even a few square inches of shade on a cell can drop the output of the entire panel immensely. I would say 240W, at least. Then you've got 24V or 12V and what kind of controller to consider.

Of course, with portable solar panels, there's a concern of them walking off.

thanks for this replay, there's a lot to think about there.

just a basic question through, on the marine and deep cycle batteries, why don't they show amp hour ratings?

also, i still haven't really got an answer on charging yet, (i think i haven't). for that EverStart Group Size 29DC Marine Battery you sent me the link to, if that was charging from my alternator (only that battery, starter disconnected) and i had the van on fast idle, how long would it take to recharge from say mostly discharged to almost full?

one thing i was thinking, i don't really need to wait for the battery to fully discharge, it makes no difference to me if i start the engine once a day for 1 hour, or twice a day for 30 mins, etc. i'd like to minimize total time of course so as not to use too much gas but one, two or more times a day of short charging is probably not a big deal.

I'l try to answer your question about the charging part as tactfully as I can:"how long would it take to recharge from say mostly discharged to almost full?"
About ten hours to approximately 90%. You will be able to do that five to ten times before the battery starts to lose reasonable functionality because you are discharging it too much.

You need to read the information at 12volt side of life and get a handle on battery use and charging. Bottom line is that you don't know what your use is going to be and therefore, no reference is available for capacity needed. The charging will relate to how much battery you carry and what your use is.

Forum member Pianotuna's linear flow chart for this is best:

Budget-->Power used-->Battery capacity--->Charging needed (sorry, Don, I know I hacked it up).
Downloadable power calculator spreadsheet