that’s how someone who wants to avoid honoring a warranty claim tests batteries, the result of which is meaningless in terms of actual battery capacity.
Starting battery
- Thread starter fred1diver
- Start date
Great post. But a bit of clarification on this specific part may help.
The sulfation process is a competing chemical process to the reversal of lead on plates and lead in ionic form in solution. Your battery is metallic lead held on plates and as your battery discharges, the lead goes into solution of the sulfuric acid. When charging, it forces the lead in solution back onto the plates as metallic lead. While the lead is in solution, it can also join with the sulfur in the sulfuric acid forming a lead sulfate. The kinetics of this process are slow. The deeper you discharge, two things happen, more lead is available to form lead sulfate, and the amount of lead coming off your plates is much greater. So when you go to charge your batteries, you are essentially redepositing metallic lead back onto your plates. However, some of that lead may have joined with the sulfur and formed lead sulfate.
The longer you wait between discharge and recharge, the more time the lead has to form lead sulfate. If you discharge deeply, you will also then be replating your plates with lead sulfate deeper into the metallic lead surface instead of just metallic lead deep in that layer.
Unfortunately, at charging voltages, lead sulfate does not convert back into metallic lead and remains as lead sulfate, and no longer is part of your battery capacity. Lead sulfate is broken down at equalization voltages. But if you have deeply discharged your battery, that equalization voltage will not be able to convert the lead sulfate plated onto your plates deep below the surface and you will over time destroy your batteries through sulfation. A process you can't avoid in any case, but one that can be greatly prolonged through proper charging and state of charge monitoring. But you can destroy a batteries capacity very quickly if you don't. We used to say, three deep discharges and your battery is dead.
The marine industry uses the 50% discharge level as the low end cut off. That's really a compromise level. I would never let my lead acid batteries drop below 65%. And that is mighty low, but the constraints in boats makes the 50% number a kind of best compromise.
Chronic undercharging seems to be a major contributor to lead acid battery failure especially in boats. Make sure you fully recharge your batteries after each discharge. Going up to say 95% is not adequate...
Learn how to perform equalization routines.
Just a FYI...
dj
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I did exactly this in 2022 (same 6V batteries, 230AH). After doing the research about how many things I'd have to change to go to something fancy like LiFePO, or even the price differential for AGM, I just didn't see the point for my usage pattern (on a charger at the dock 24/7 except when I'm out cruising). The only other major electrical upgrade I did make was to put in a Balmar SG200 battery monitor, which was HUGE as far as knowing what's going on with the batteries. So far, I'm very happy with the new system. Still have the old 12V starter, which I almost never bother to use, but it's there for backup.
Ok, so I just finished installing my ACR but the schematic I followed does not use the 1-2-both switch, I will add an on-off switch to both the circuits to be safe.
Still trying to figure where my alternator plugs into the circuit. To be followed
Still trying to figure where my alternator plugs into the circuit. To be followed
Unless a prior owner has messed with it, the alternator output goes to the starter. This is done for a couple of reasons, it ensures there is a load on the alternator when the engine starts as it must be connected to a battery and it is cheaper and faster for the boatbuilder to install an engine with just one large DC wire that connects the alternator and starter to the 1-2-b switch.
Dave's right here's another reason why:
OEM 1-2-B Switch Wiring History Alternator/Batteries & "The Basic" 1-2-B Switch BEST Wiring Diagrams
1-2-B Considerations (New 2020 - Rod finally got around to diagramming what I had done in the above link in 2009
)1/2/BOTH Switch Considerations
Are Battery Conductance Testers Worth it?
Are Battery Conductance Testers Worth It? - Marine How To
20 Hour Capacity Test Results PUBLIC APOLOGY: First let me begin this by eating some public CROW. Over the years I have recommended these testers for boat owners or techs to use, as had the ABYC and other reputable organizations. While I have always maintained a get a baseline
marinehowto.com
He is trying to find out why his engine wont crank!
Mea Culpa... I read the topic "Starting Battery" and assumed he had a cranking problem. You all are totally correct about capacity.