[C320-list] Flooded acid battery and refrigeration questions

[Scott Thompson]

Troy, my understanding is that modern MPPT solar controllers anticipate 
the problem you mention and are programmed to avoid it. For example, the 
Victron solar controller on my boat reads the battery voltage when it 
first turns on each morning, and if the battery is almost fully charged 
(resting voltage at least 12.6v) it limits absorption time to one hour. 
Lower resting voltages increase this time up to 6 hours for a discharged 
battery. Furthermore, it switches to float voltage as soon as the 
absorption amperage drops to one amp or less. All of the parameters are 
tuneable. You can read details of the algorithm here: 
https://www.victronenergy.com/media/pg/Manual_BlueSolar_MPPT_75-10_up_to_100-20/en/operation.html 
<https://www.victronenergy.com/media/pg/Manual_BlueSolar_MPPT_75-10_up_to_100-20/en/operation.html>. 
BTW, the default voltages on my controller are 14.4 for absorption and 
13.8 for float. There is no separate bulk voltage target. The controller 
switches from bulk to absorption mode as soon as the absorption voltage 
is reached.

On 11/16/2021 7:32 PM, Troy Dunn wrote:
> Wow, so many things going on here at once.   This thread may grow beyond
> one of those "which anchor is better" debates.
>
> One thing we need to clear up.   Boiling off generally will occur when a
> battery is closing in on a high state of charge (so generally low amps)
> with a higher voltage applied.   So for instance on my batteries I can
> supposedly bulk charge (aka constant current at a target voltage of 14.9
> and drop back to about 14.6 for absorption (constant voltage) and then back
> to something closer to 13.5 for floating on the alternator.  I have learned
> over time that because I’m not a full time cruiser, I don’t really
> want/need these aggressive charge profiles and I back this off a couple of
> tenths to slow down the boil off (this seems to have helped, perhaps at the
> expense of maybe some top end battery life expectancy…but GC2s are so
> affordable it’s really a don’t care.)
>
> What caught my attention was the possibility of the MPPT resetting it's
> charge profile each day (I assume triggered by sunlight hitting the panels
> and creating current once again?).  This seems like a horrible thing if
> true, and would absolutely be a problem.    You can bet you are cooking
> your batteries if you have a decent sized set of panels that get you to
> float in the first day or so.   If you find this to be true, find out if
> there is some other setting you can use to prevent that from happening.
>
> Lithium Ion on a boat?  Not a good idea.  If you meant LiFePO4…sure, if
> cost is not a factor, go for it..you can fit way more capacity in the same
> space, the batteries will last longer than either twofootitis or swallowing
> the anchor in most cases, you won’t kill your back installing them, etc.
> Just admit you like spending money to have the coolest batteries and also
> be prepared to upgrade all of your charging systems if they are not forward
> compatible with LiFePO4 chemistry.  Battleborn and DIY builds from single
> cells and a BMS seem to be the preferred choices of many live aboard full
> time cruisers.
>
> There is one battery monitor that is closing in on delivering on the
> promise of being pretty smart and pretty hands off.   That’s the Balmar
> SG-200.   I was a somewhat early adopter of this gadget and was very
> disappointed with the way Balmar handled the roll out of this device.   The
> first few software versions were very buggy and did not deliver on the
> marketing hype.   They also required you to purchase a Bluetooth dongle in
> order to get the firmware upgrades onto the device.   This really soured
> the community and if you go out to cruisers forum you will find a
> ridiculously long thread there that will definitely be a turn off.   I can
> say that Balmar has finally worked out a lot of the bugs and I believe now
> that the device is delivering on the promise.   Also…despite the grumbling
> of the community about having to purchase that dongle…it does enable the
> phone app which is really a game changer and so, it really is worth it.
>
> FWIW
>
> Troy

-- 
Scott Thompson
Surprise, #653