Starting battery and deep cycle - charging

[camaraderie]

If your battery drops below 12V you are quickly killing it.
You're gonna be buying a lot of new batteries if you wait till 11V.
12.25 is the lowest you should normally let it go.

[wind_magic]

Adding a little context to Cam's post ...

[camaraderie]

Windy...I have charts from a very well respected mfr. that show far less difference between 30% an 50% discharge for THREE different ranges of batteries....
Cycles 4200>>>3200
1707>>>1280
768>>>576

That is the difference in cycle life between 30 and 50% discharge on their good/better/Best batteries. The important thing to note is that in each case in terms of AMP HOURS delivered over the life of the battery...cycling to 50% gives you more than cycling to 30%.
This is NOT the case with your last graphic nor does it resemble anything else I have seen. Are you at liberty to share the source and type of battery that was being tested in your above post?

[wind_magic]

Originally Posted by camaraderie

Windy...I have charts from a very well respected mfr. that show far less difference between 30% an 50% discharge for THREE different ranges of batteries....
Cycles 4200>>>3200
1707>>>1280
768>>>576

That is the difference in cycle life between 30 and 50% discharge on their good/better/Best batteries. The important thing to note is that in each case in terms of AMP HOURS delivered over the life of the battery...cycling to 50% gives you more than cycling to 30%.
This is NOT the case with your last graphic nor does it resemble anything else I have seen. Are you at liberty to share the source and type of battery that was being tested in your above post?

Hey Cam, it came from here ...

Source: 12 Volt Electrics in A'van for Manins

[JimsCAL]

I would scrap the small starting battery and just go with a single deep cycle battery. With an outboard, you can start by pulling manually if the battery is low. I sailed for years on Pearson 26 with a 8hp Johnson that charged a group 24 deep cycle house battery. It kept the charge up with no problem on cruises as long as three weeks.

[camaraderie]

Thanks Windy...that is from FullRiver out of China for their AGM's. The 50% cycle life is really low. Wonder why?? Would certainly explain the low prices!!

[flatracker]

Why dont you just do away with the little motorcycle battery, and run off the house bank entirely. That little outboard isn't going to take enough out of a deep cycle house battery to effect it much. Will eliminate a battery, some wiring and simplify things too.