Battery questions

[BassChump]

I have a 16 foot Trophy bass boat with a Minn Kota 40 lb thrust trolling motor. I have a 900 CCA battery that usually gets me around almost all day. I have a 550 CCA battery as a backup.

This weekend I was charging the batteries and checked the water in them. These batteries are several years old. Anyway, the water was down to the top of the plates so I added some distilled water.

I went out yesterday and got only about 3 hours on the 900 CCA battery.

I've noticed that when I'm charging them, they continue to charge much longer than they used to and they are venting more than they used to. When charging, the clips are getting warm.

I use a variable amp charger that I've used for years with no problems at all. I usually charge the batteries until it's only charging 2 amps or so. I figure after that it's only a trickle charge so I don't want to overcharge them.

Is there a problem adding water or are the batteries dying??? It's a tough financial time for me right now so if there is any way to keep these batteries going for the rest of the season, that would be great.

[Grey Wolf]

Probably dying.

[Jig Man]

It sounds like your batteries are on their last legs.  When you replace them get RA not CCA batteries.  You need deep cycle batteries not starting batteries.  Get 185-200 RESERVE AMP batteries.

On the water thing, it is normal for water to evaporate out of open cell batteries when they are being charged.  I check and top off mine every months.

[BassChump]

My apologies. You are correct. Those are deep cycle batteries. I should have said RA, not CCA.

In any case, once I added water, they aren't performing like they did. Why would the problem come up when I add water?

They are kind of old but I was wondering if it is just coincedence or is there a reason when I added water, that they died?

I was getting better than 7 hours out of each one before adding water.

Just curious.

[Ann-Marie]

The acid, particularly when water has been lost, is much more dense than the replacement water.  As the water mixes slowly with the acid, you get stratification with concentrated acid at the bottom and very dilute acid at the top.  So in effect you have reduced capacity by 50%, using only the bottom of the plates.

If you add a lot of water to a depleted battery, it is time to do an equalization cycle.  This means getting the voltage above 16 volts for 15 minutes to cause vigorous gassing.  This will stir up the electrolyte and remove the stratification.  Despite this advise, it is my experience that you will still end up with diminished capacity in an older battery after adding water.  Rather than "fill" the battery it is better to add just enough to cover the top of the plates.

[BassChump]

Hi Ann-Marie,

I think you hit the nail on the head. I took the boat out this morning after charging both batteries for 2 days. They kept taking at least 4 amps so I just left the charger on.

Today I was on the lake for about 5 hours and the main trolling motor battery had plenty of juice left after fishing for most of the morning.

I hope that mixing the water will work until the end of the season. The batteries seem fine at the moment at least.

        Thanks for your imput. Makes sense to me.