Deep Cycle Batteries

[Gulf Islander]

Recently purchased a C&C 35 mk2 which had a single house battery. My question is how long do deep cycle batteries last and what effect does the battery being undercharged have on it? The previous owner doesn"t remember when it was purchased so it could be 6 to 8 years old.

[Target9000]

Many many factors contribute to a batteries longevity. If it is a flooded lead acid deep cycle battery that is kept full of electrolyte and isn't abused >too< badly, you can expect five years.

If you drain it down to near dead too often or chronically overcharge/undercharge it, or if you keep put it in extreme temperatures you may reduce its life.

[jeremiason]

Do a voltage and hydrometer test on it...

Battery life depends on lots of things, including owner maintenance, which judging by his lack of knowledge suggest he probably didn't do a great job.

On side note you didn't say what size the house battery was, but a 1970's boat did not have and was not designed for todays electrical requirements.

You should think about expanding the house bank...

[noelex 77]

Welcome to the forum Gulf Islander.

As others have said 5 years is a typical life for a cheapish flooded battery, but it is very variable. I got 16 years out of one house bank.
You can do a load test on the battery (a forum search will show a few posts on this) which will tell you the capacity, but the test is hard on the battery, so many people simply wait until it fails.

[Cheechako]

Generally 5-6 years life. Well cared for could be more. If they sit too long unused they go bad. Charge it fully ,, disconnect everything and measure the votage the next day. If it doesnt stay fully charged it's probably garbage....

Speaking of which, has anyone noticed the price of batteries??? I need to put one in my van. Seems like the last Costco car battery I bought (differetn car) was like $60+. Now a battery is running about $100... even at Wal Mart! Must be the trucking cost....

[Kiwi303]

Nope, lead cost increase is probably more than trucking cost. Same problem with bullets for reloading, the US Armed Forces pushed up the prices in a major way over the past decade and it's still climbing.

At current rates Afghanistan will have a mining boom in lead and copper when the US pulls out!

[Gulf Islander]

Thank for the input. Since buying the boat I have added 2 115 ah batteries to the house bank. I'm not sure if the old battery is having a negative effect to the bank but I guest my best course of action would be to just replace it so that I'm using 3 new batteries.

[noelex 77]

Yes, get rid of it. Don't mix new batteries with one that is 6 years old on the same bank.

[Kiwi303]

A bad battery that loses charge can suck current from good batteries, killing them as well.

Hence not mixing batteries.

[Sonosailor]

Surely, somewhere on this site is more information on battery life, but here's the basics for longest life.
1. Size the bank, charging systems and usage so that the batteries never drop below 50% of storage;
2. Monitor the batteries to learn how often they need to be topped up with distilled water;
3. Don't overcharge, undercharge, allow dirt to gather on or around batteries;
4. Equalize the batteries in a manner approved by the battery manufacturer whenever there is a difference of 0.030 Specific Gravity between cells, or around 6 months. Trojan has good info on equalizing batteries on their site.

Again, I'm sure this site has better info, and a longer list.

[Stu Jackson]

One of the most helpful tutorials ever:

Technical Documents, Manuals, App Notes

Use the Tech tab to download the Ample Power Primer and associated wiring diagrams.

[rebel heart]

Originally Posted by Cheechako

Speaking of which, has anyone noticed the price of batteries??? I need to put one in my van. Seems like the last Costco car battery I bought (differetn car) was like $60+. Now a battery is running about $100... even at Wal Mart! Must be the trucking cost....

I was thinking of swapping out my T105's that are about two years old before we leave the country until I saw them for about $200 a piece. I'll try to get four more years out of them instead.