How do I know how good my battery is? And how reliable is that test (if one exists)?

[Philster]

Re: 1996 Wellcraft Scarab, 502 c.i.d Merc Magnum (8.2L), EFI/MPI.

Batteries and auto/boat electric systems in general are the weak spots for me.

So, my boat is new to me, and she has the same battery from when I got 'er in the fall (age of battery unknown). Took her out a few times in the fall and she always cranked fine. I actually winterized 'er in November and she sat (with battery in! I know... I know) all winter and when April came around I charged the battery overnight with a basic charger.

In May I cranked 'er up and got her toasty warm and made sure she was (somewhat) ready for the Memorial Day weekend, so that fun on the water could be had until October.

She has been used just about every weekend since May. The first time out, I actually ran her for 2 hours before turning her off to get more charging time in. Plus, I invested in all the maintenance items one should on a used boat. Every hose and belt: Replaced. Manis/Risers/Elbows: Replaced. Water pump/impeller: Replaced. All fluids: Replaced.

There's more, but the gist of my post is this: So what to do with the battery? I have a one-battery setup. I actually have a Perko battery switch sitting around.

Is there a reliable way to test the battery? Do I have a fairly deep reserve (can that be known) or am I getting away on surface charge? Should I just go get a new battery and be proactive and then, at some point, just make the jump to a switched, 2-battery setup?

The question in bold is most relevant right now.

 

[NYBo]

Re: How do I know how good my battery is? And how reliable is that test (if one exist

A battery will be fine stored in the boat over the winter as long as you keep it fully charged, so no worries there.

Take the battery to an auto parts store and have them do a load test. Based on the results, decide what to do with that battery.

Since you already have the switch, I would go to a two battery setup sooner rather than later, keeping your current battery in the mix as long as it passes the load test. Ever try to pull-start a big block V8?

 

[asm_]

Re: How do I know how good my battery is? And how reliable is that test (if one exist

If you have a charger that will show you voltage during the charge cycle, that can be used to get a rough indication of the battery condition.

A battery that is near the end of its life will exhibit voltage rise very quickly during constant current phase of the charge cycle. This will in turn fool the charger to switch over the constant voltage mode, and eventually end the charge cycle prematurely. However, once the charge cycle is ended, battery voltage will drop to below 12.7v after a few hours. This signify the battery has begin to develop high internal resistance. In layman's term, it now has lower crank amp and reserved capacity.

Or, you can also take the battery to a auto parts store. They usually have a battery analyzer that can determine battery condition fairly quickly.

B

 

[bruceb58]

Re: How do I know how good my battery is? And how reliable is that test (if one exist

The only ways to determine the health of a battery is to:

1) Measure voltage at full charge after letting it sit for 60 minutes to determine if there are any bad or weak cells.

and

2) Load test it with a constant current and measure the resulting voltage to determine capacity.

 

[ajgraz]

Re: How do I know how good my battery is? And how reliable is that test (if one exist

The only ways to determine the health of a battery is to:

1) Measure voltage at full charge after letting it sit for 60 minutes to determine if there are any bad or weak cells.

and

2) Load test it with a constant current and measure the resulting voltage to determine capacity.

x2.

First, assuming this is not a maintenance-free, AGM or gel-cell battery, make sure the electrolyte is full (pop the caps and use a dropper and deionized/distilled water, any grocery store has this)

Then do test 1), make sure you've got it charged to where it'll read 12.7-12.8v, and then if it's below 12.6-12.7v after sitting an hour or two, it's dying/dead or will be dead very soon. BTW, how many amps is your charger?

Even if it passes test 1), then go do test 2) also (any auto-parts chain store can do this), for peace of mind.