A Question on Charging

[capt ric]

guess I will just hope for the best and put it in the budget...liths to scary and pricey...so whats a good brand to buy ....better then property taxes

[Maine Sail]

Originally Posted by daveNZ

Is there any guide as to what SOC a battery is at when it reaches the end of the bulk charging phase?

The point in the SOC curve where you hit absorption voltage will entirely depend upon how much current you are charging with.

With a 10W solar panel you may not hit absorption voltage until 98.5% SOC but with a 250A alternator you may hit it at 55% SOC.... Sulfation also plays a role. The more sulfated the batteries are the earlier you will hit absorption voltage.

Originally Posted by daveNZ

In a small, 150-200AH bank is the higher charge efficiency of AGM going to allow shorter engine charging time to reach either the absorption phase (by alternator) or fully charged (by solar); it should in theory but does it translate to actual experience on the water?

AGM's do charge faster but it really depends upon how you take care of them as to how long they will charge as fast as they did when new......

[a64pilot]

Originally Posted by capt ric

guess I will just hope for the best and put it in the budget...liths to scary and pricey...so whats a good brand to buy ....better then property taxes

What type of battery? From cost perspective, nothing is better in my opinion than Sam's club golf cart batteries, or Costco, whatever store you have.
They are literally about 1/3 the cost of Lifeline AGM.

Yes AGM's assuming you have a big enough charge source will charge faster than FLA, but here's the catch, they had better charge faster because they are very intolerant of partial charge, you'll greatly reduce their life that way. So if you often partial charge them, they then become what, six times more expensive than the golf cart batteries?

[Maine Sail]

Originally Posted by daveNZ

Apologies, silly question, the answer to my first question would be the often mentioned 80% (approx).

Not silly at all and the 80% number bantered around is very often misleading or simply incorrect for your system because it all depends on how much current you have as to when in the SOC curve you will hit absorption voltage as well as how healthy your batteries are.

I regularly see AGM batteries that have been abused come up to absorption voltage very quickly from an SOC below 50% even with just a .15C +/- charge rate. This is because they are heavily sulfated. The somewhat used battery in the graph in this thread took 1:42 minutes to exit bulk at a .2C charge rate from 50% SOC... A .2C charge rate is pretty low for an AGM but I usually see less than this so most folks are not truly taking advantage of the AGM's acceptance rates as effectively as they could. Bulk charging is very, very efficient, pretty darn close to 98-99%, so the longer your batteries can stay in bulk the faster you can charge them.

I would suggest reading the May 2015 issue of Practical Sailor for more insight on how quickly one can abuse an AGM battery if you are PSOC (partial state of charge) cycling them. It also highlights how different brands of AGM's handle a PSOC environment.

Originally Posted by daveNZ

I'll rephrase the second part as well:

In a 200AH bank does higher charge efficiency of AGM lead to reduced Bulk or Absorption charging time; it should in theory but does it translate to actual experience on the water? (assuming best voltages etc)

Yes it can translate and charge faster but you need to be able to take advantage of it and keep the batteries healthy in order for the charge faster benefit to be worth the added expense over the long haul.

[daveNZ]

Thanks for these comments, and I thought I nearly had 12 volt batteries under control!


Sent from my iPad using Cruisers Sailing Forum

[capt ric]

I dont get the 1:42 minute thing at .2 C... whats C, charge %, or capacity???...

[Maine Sail]

Originally Posted by capt ric

I dont get the 1:42 minute thing at .2 C... whats C, charge %, or capacity???...

"C" is charging current

".2" is how much charge current (.2C is 20% of a 125Ah battery in charging current)

The 125Ah battery took 1 hour and 42 minutes to increase terminal voltage to the 14.4V point, with a charge current of 25A or 20% of the Ah capacity... 1:42 is how long BULK (CC or constant current) charging took. After 14.4V was attained the battery entered ABSORPTION (CV/constant voltage or voltage limited) and current dropped off.

ABSORPTION charging took 5:24 minutes before the battery was at 100% SOC...

[sailorsaki]

Originally Posted by Utahsailor

This spring we installed a new battery bank with about 1,000 AHr of T105s. The solar panels have kept it fully charged during the summer and for short sails. We have left Belfast ME for the south and find the shorter days, more masking by sails and rigging and higher power consumption during sailing don’t allow full charge from solar alone. During day long powering the dual 300A output alternators used to fully charge the bank but now the charging has plateaued at 89% (from Balmar Smart Meter). I ran the engine this morning at anchor and was still putting in 180 A after 45 minutes. The solar setup is 840 W with dual Morningstar controllers. All charging inputs lead to a common bus. So a few questions:

Could the Balmar controller see the competing controllers and cut back its output?
How can I safely shut off the solar panel output to just use Balmars for long powering days?

Thank you for the answers

Try asking at your nearest electrical parts supplies store if they have a regulator