Charging two batteries

Tilla · 12-05-2001, 12:59 PM

I have been charging each of my two batteries in my sled at separate times. I disconnect the wiring and switch the Perko battery selector switch to off. I use a deep cycle trickle charger. I was wondering if I had the switch set to both batteries and left the two batteries connected, would I be charging both 12 volts at the same time?

Pete · 12-05-2001, 01:16 PM

Several ideas for you ...
1. Send an e-mail to Pilar ... he's "the battery guy"!
2. Search the Ifish archives ... there has been some discussion related to this and with regard to selecting either a marine starting battery and/or a deep cycle battery.
3. Read the following:Reliable Battery systems
.. but take it with a grain of salt.

Paranoid · 12-05-2001, 01:38 PM

I have three batteries on my sled. I top them off before a trip by setting the switch to "ALL". It does seem to take a little longer but it does charge them all. #1-exclusively for the starter. #2-all other electronics, lights, etc. #3-isolated by a breaker switch and used for emergencies only. I also trickle charge them on automatic to keep them up when I know I won't be using the boat for awhile.

Pilar · 12-05-2001, 04:08 PM

Yes, it will work if you are just boosting almost fully charged units. The voltage will be the same on each battery but the current will split between them. The higher charged battery will accept less current than the other one.

Actually the slow rate of charge in this case is better for the batteries. Figure on about 24 hours to top two off at the same time. No more than that as overcharging is bad. You can tell when they are done because they will bubble, hiss and gas and get warm.

Or use a hydrometer and charge until the reading stops going up.

Don't smoke near the charger, the gas is hydrogen, BANG!

Exceptions..... If one battery is bad it will either reject the charge or hog it. The other battery will suffer in either case. So replace them in sets and they will behave the same and charge together. Also any completely discharged battery should be charged alone.

We have lots of downtime in the winter. During the week when not fishing, boost your batteries for a day once a month. Also disconnect them if you are not going to use the boat for more than a few weeks to prevent discharge.

A fully charged battery will not freeze.

[ 12-05-2001: Message edited by: Pilar ]</p>

Tilla · 12-05-2001, 05:24 PM

Pete, I liked what that article said. I have two deep cycle batteries. Battery #1 seems to be incapable of starting the engine alone even though it it was charged the night before and the charger indicates its charged. So, is it that the battery is bad or is it that it is undersized or does my 200 Merc like to be cranked fast?? The engine turns over faster and starts better cold with the two. Hmmmm.
Pilar- At least I know that I can do both. I need to overcome the issue of whether I have a underperforming battery. I need to interpret whats going on. Once warm the engine does fine with battery #1.
A third starting type battery and a rewire job might be the answer too. I run a 12vdc electric too and we could keep that isolated from the starting battery.

bait boy · 12-05-2001, 06:18 PM

IF I remember correctly the deep cycle batteries are made to be discharged all the way everytime and tend to have lower cold cranking amps than your average heavy duty battery. and there is also something about how long it takes to wear down a battery with a slow draw.

From what I've seen folks that use deep cycles as both batterys have a harder time getting them to start an engine.

Pilar went on a long shpeel a while back about 2 battery systems use one battery with high CCA to start and one Deep cycle. Switch to both for running distance and switch to the Deep cycle only to run stuff like fish finders electric motors and such., and when its time to go home use the high CCA to start and switch to both for the run home(or use both to start after the engine is warm)

Vinny · 12-05-2001, 10:19 PM

Regarding battery #1, two checks.
1) Hydrometer will check the specific gravity (the charge) of each cell. If you get a cheap one with the balls, get one with 5 balls, not 3 balls. Charge, then test each cell. Each cell is 2.1 volts. Dead cell? Replace Battery.

2) Bring it to anyone who sells batteries and have it load tested. There's no charge. Usually, if you bring it in for a load test, you're going to buy a battery.