Proper battery charging procedure?

I did a quick search, and couldn't find anything that pointed exactly to my question (in the last couple of weeks), so figure I would ask.

What is the proper method of charging the starting and trolling batteries? More specifically...I have 2 deep cycle marine batteries. One is a cranking (Interstate), the other is for trolling (Everstart). I have a charger that does 2a/10/50a and has a switch for conventional and deep cycle batteries.

I normally charge deep cycles that are not in constant use, once per month at the 10a deep cycle setting until fully charged, and then before taking the boat out...I normally charge them up the night before.

However I read recently that you should put the batteries on charge when you bring the boat home....

What is the method to use to get the most life out of my batteries?

Re: Proper battery charging procedure?

For the cranking battery, 2 amps only. If its one of those auto peak chargers, the way to keep a battery lasting the longest is to not drain it all the way, don't let the water go dry, don't overcharge it and to charge it at the lowest rate possible.

That's a good idea for the deep cycle as well, but not as critical as the deep cycle's lead plates are much thicker than your cranking battery's plates.

This is a dead horse, but that information was told to me by an electrical engineer.

This should help and from the manufacturer themselves:

http://www.interstatebatteries.com/www/faqs/tech_talk/maintenance/charging.htm

Re: Proper battery charging procedure?

As soon as possible after using my deep cycle batteries for any length of time they get charged up. I was told to always keep them charged to help prevent build up on the plates in the battery.

Re: Proper battery charging procedure?

Leaving a battery in a discharged state is great way to kill it. Charge it immediately after use.

This is from the Interstate Batteries web site:

Q: What's the best way to charge deep cycle batteries? The maximum charger rate in amps should be 20% of the amp hour rating of the battery.

Normally, deep cycle batteries do not require special charging procedures. However, we recommended that you use a charger designed specifically for deep cycle batteries. It is best to slow charge all batteries, especially deep cycle. The 20% rule should be used when charging a deep cycle battery. That means to choose a charger where the maximum current (in amps) is less than 20% of the Ah rating. For example, an Interstate SRM-27 is rated at approximately 100 Ah, so a 20-amp charger should be the maximum. Also, it is best to use a charger that is adequate to recharge the battery within 10-12 hours.

Q: How long should I charge my battery and at what current? Generally, we recommend that you use a low amp charge, i.e. as low as the battery will accept, over a longer period of time. A 10-20 amp charger can charge most automotive batteries. Fully charging a completely discharged automotive battery, for example, with a 10-amp charger may take approximately 6-10 hours at a temperature of 80?F. Lower ambient temperatures require a longer charge time.

Some chargers automatically adjust the current and length of charge according to the battery's state of charge and then shut off when the battery is fully charged. If the charger requires manual adjustment for current or shut-off, check the charger's instructions to determine the proper current and length of charge based on your battery's rating.

Note that for auto/starting batteries the actual charge rate is rather loosely defined. A 2 amp charge rate is a "maintenance rate". Most battery maintainers are in that 1.5 - 2A range. That said, most starting batteries never get deeply discharged in normal use so a maintainer is all that's required -- not what is required!. That's why I recommend that multibank chargers with 10 and 20 amp outputs are not necessary for the starting battery. Install an on board maintainer. Use a 6-20 amp onboard charger for the deep cycle and save the expense of another bank whose output will rarely be used.