Trickle Charge

[Flipside]

I have two batteries on a Perko switch. Do I need to pull both batteries and charge one at a time or can I connect a trickle charger to one battery while in the boat with the Perko switch to 'All' setting? Any chance of zapping engine computer or electronics by leaving the battey in the boat connected and injecting a trickle charge?

[SquamInboards]

Your system should be fine, however leaving a trickle charger on batteries continually is not really advised. There are a number of kinds of batteries (AGM, Lead Acid, Wet Cell, Gel Cell) and deep cycle batteries like to be charged differently than starting batteries. To really treat your batteries best as possible, each battery should really have it's own voltage regulator (or a regulator that can manage multiple batteries) and a larger Alternator should be added to the system. Trickle chargers don't agitate the sulfates around the lead plates much, letting your battery completely discharge is bad (v<~10.1 - complete discharge). Higher end chargers can be adjusted to battery types which adjusts the bulk, absorption, and float charge durations. Probably more than you needed to know but it's worth reading up on DC systems, there are lot of things people miss when it comes to electrical in their boats. (not a knock at you there, everyone should read up.)

[gride]

ctek chargers rule

[wake_fun]

I use this mounted inside my boat, plugged in year round, works perfect

LINK

[shonuff]

A float charger would be best. You can leave it hooked up all winter and not worry about overcharging it.

I'm not sure about trying to charge 2 batteries in parallel though.

[DanielC]

If the batteries are two different types, no.
If the batteries are identical, and were bought at the same time, maybe, but it is not a good idea.
Here is why.
You are building a parallel circuit. The current from the trickle charger has a choice of going through either battery, or both. It will go through the path of least resistance. If one cell in either battery goes bad, and shorts out, that battery will take most of the current from the trickle charger. Additionally, the bad battery will drag the voltage in the good battery down to its level.

The first step I do when recomissioning the boat, is to hook up a cheap 6 amp battery charger to it battery. I leave it hooked up until I am ready to start the boat. At that time, I check the current on the battery charger, and it usually has fallen below a 2 amp charge, and the battery voltage is above 13 volts.

In the fall, I check the water level in the battery, and fill it with distilled water, if needed. I do this before the last time I run the boat, usually. If I have done this, I assume the battery is OK, I just disconnect it, and do not worry about it over the winter. Having said that, I typically put the boat to sleep in late October, or early November. In several years, I bring the boat out for New Years Day, run it, and refog, and drain the water again. I recommission the boat for the season in February, or March.

The short story is this. I typically just disconnect the battery, in the fall, do not bother to trickle charge it, hook it back up in the spring, and charge it then.

I should note, I do not have a killer stereo system in my boat, I do not have ballast pumps, or many other electrical accessories. My boat battery has a pretty easy life. It is also not that cold in the winter, where I live, and the boat is winterized for for a relatively short time. I also use a conventional Lead acid battery. I have replaced the battery in my 1997 Ski Nautique once, but I realize it may be getting close to the time I need to replace the battery again.

[wake_fun]

That's why you should buy one like I did. Here is a quote from my charger manual:

"These units are designed to charge and maintain one or two 12 bolt batteries. Because each bank of the chargers are independently grounded and electrically isolated, these units can charge up to two independent batteries, two 12 volt batteries in parallel, or two batteries joined in series (24 volt) without disconnecting the batteries from and switches or wires/straps joining the batteries. Simply attach a pair of outputs to each battery..."