Marine Battery for Car?

[dvw]

Before retiring I worked the last 10 years of my career in the electrical garage at FCA (Chrysler, Stelantis). We worked on 1000's of prototypes. Many sat for months. So plenty went dead. We also had a dedicated battery lab. So talking to guys that did nothing but batteries was interesting. What I learned. Running batteries to completely dead definately shortens their life. Over charging at to many amps kills them. These are the two biggest contributors to failure. Most batteries can take high voltage/low amperage charge and will recover more quickly. Power supplies are much better way to charge a battery than most chargers. Most people don't understand state of charge. Based on temp 12.66 give or take is a full charge. 12.2 is roughly 50%, 11.9 is 0%. It's good practice to disconnect a battery if it's not going to be used. Why take a chance on a draw (radio with memory, modules, etc) killing it. A low charge battery can freeze. Frozen batteries are scrap. Higher voltage will crank better than higher amperage. Thus many high compression motors use higher voltage. AGM batteries are better choice unless you let them go to low and charge at to high an amperage. As far as brands. I've used many. Factory batteries are very good. From personal experience Walmart batteries are also very good. Auto zone are not the greatest. Running a 12 volt battery(s) in a drag car that go a lot of rounds with a lot of accesories is tough. Cooling between rounds takes more out a battery than the alternator has time running to recharge. Then the state of charge goes low. Now your in the lanes with no crank. Our racecars use 16 volt with dedicated power supply style chargers. This setup will allow the use of no alternator even with high amp loads. However running an alternator makes between rounds much easier. A single 16 650 CCA volt is far better than 2 12 volt 850 CCA.
Doug

 

[padam]

Below are pics of the Walmart battery I bought, $139.
I chose it over the group 27 because it had higher CCA.
It’s about 5lb lighter than the old battery, just a guess, I should have weighed it.
I had to make a little change to the tray since it is wider than the old one but no big deal.
I also bought new stud terminals.
Once I got it installed it turned the engine over very fast, so the as new performance is good. We will see how long it lasts.

As an aside, I tested my deep cell trailer battery and it checked around 12 volts, but under load it showed weak. This is the one that took a charge but wouldn’t even crank the engine one turn. Looks like I will be replacing it as well.