A battery question

**Bigchris090** · 03-13-2019, 04:21 PM

Myself and a friend are restoring an old ring/shakey 20. The time has come to start the wiring
we have trim tabs, engine trim tilt, horn, electronic ballast drain/fill.

The old mercury "v225" only has a 9a stator i think. would it be wise to use two batteries? one cranking/engine battery and another leisure battery simply running down during the day to be charged at home?

Chris

**Merc 2.5** · 03-14-2019, 04:03 AM

Maybe stick ballast on ex batt. sounds like a plan

**Dave Strong** · 03-14-2019, 12:30 PM

What ever you decide use lead acid batteries not AGM.

Dave

**SS Minnow** · 03-14-2019, 01:38 PM

Could hook both batteries up, just wire 2nd battery in with a diode. That will allow the battery to charge but current cannot be drawn from start battery. It is basically a check valve for electricity.

Depending on your use though, likely to need an auxiliary charger still.
Possible to upgrade the charge system too?

**W2F a V-King** · 03-14-2019, 04:18 PM

Two large batteries will work fine. Will give you capacity to run stuff, and a deeper capacity to absorb the unregulated charging voltage. Problem with the old charging system is it will continue to charge even when they are fully charged, boilng the battery(s) There is a rectifier and no voltage control.

I like a battery directional control switch to select which battery gets charged (1 or 2 or both or off )....

On days I run around more than fish (joy ride) in my bass boat with 3 batteries, sooner or later....usually later the volt meter will begin to climb higher than I like. Time to turn on lights and other items to bleed this off. This is with a 1985 Mariner 150 9 amp system. Usually isn't a problem on a bass rig with troll motor, two well pumps and a bilge pump....

Many years ago, offshore in a CC, I toasted an old paper recording depth finder....wasn't paying attention...poof .... let the smoke out of it.

**flabum1017** · 03-14-2019, 04:22 PM

A diode will still allow the house battery to draw from the start battery. Get a charge relay if you want to keep the house and start battery separate.

**eli** · 03-15-2019, 09:23 AM

Originally Posted by Dave Strong

What ever you decide use lead acid batteries not AGM.

Dave

why not agm

**SS Minnow** · 03-15-2019, 09:32 AM

Originally Posted by flabum1017

A diode will still allow the house battery to draw from the start battery. Get a charge relay if you want to keep the house and start battery separate.

You are right. Would need 2 diodes to make it work.

**Dave Strong** · 03-15-2019, 10:19 AM

Originally Posted by eli

why not agm

Seems the old style charging systems don't like them. Lots of fried stators, regulators, and rectifiers last few years at work. Nearly all had AGM batteries, have even heard of engine fires from charging system related. Remember when that charging system was designed only lead acid around. Does not seem to bother the boats with alternators.

Dave

**eli** · 03-15-2019, 11:59 AM

Run blue top since 2003 never replaced a stator. Maybe few rectifiers bout it

**Dave Strong** · 03-15-2019, 12:23 PM

Originally Posted by eli

Run blue top since 2003 never replaced a stator. Maybe few rectifiers bout it

Just reporting what we see on a daily basis at work and hear from other shops.

Dave

**KIRCHNER** · 03-15-2019, 02:34 PM

Originally Posted by Dave Strong

What ever you decide use lead acid batteries not AGM.

Dave

WHATS wrong with a agm batt?

**Dave Strong** · 03-15-2019, 03:52 PM

Originally Posted by KIRCHNER

WHATS wrong with a agm batt?

Nothing if you have the correct charger. Stator style systems don't get along with them. Mercury does not recommend using them in stator style charging system. Std old style battery chargers can not properly charge an AGM battery.

Dave