I have a cabelas 2 bank battery charger on my boat. I used to charge with a schumacher charger that gives the % the battery is charged. Would it damage anything if I hooked the schumacher charger to check to see if batteries are fully charged??? Thanks for the help in advance

I would think that if your onboard charger was not powered on and you connected the schumacher, it would be about the same as if the motor was running and charging a cranking battery. When that happens, the onboard charger doesn't get damaged.  I wouldn't connect and power on both chargers at the same time though.

Edited November 8, 20187 yr by redmexican5081
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just buy a volt meter and check it that way. Takes 5 seconds

Harbor Freight inexpensive Chicago battery tester applies a load and voltage readings.

Tom

I have an onboard 4 bank charger.  My cranking/accessory battery is a Sears PM1 AGM.  Due to the age of my on board charger, it does not fully charge a AGM.  I use a Shumacher portable to top it off because it has both a AGM setting and a Gel setting.  I occasionally hook it up to my wet cell TM batteries to check the final charge level.  I have been told that it doesn't matter if the onboard is plugged in but just as a precaution, I unplug it before I hook up the portable.  I do not unhook it.  I have been doing this for many years and my AGM is 5 years old and going strong.  As a point of reference, my on board charges my wet cells to 98% and my AGM to 90% when all are showing green lights and in maintenance mode.  

Thanks guys.

I got totally away from onboard chargers, all I have ever owned have failed at some point.  I only use the Schumacher chargers now.  No battery issues in years.

18 minutes ago, McBass_Arkansas said:

I got totally away from onboard chargers, all I have ever owned have failed at some point.  I only use the Schumacher chargers now.  No battery issues in years.

I understand your logic but I have 4 batteries and charging them after a trip and then tending them in between trips would be pretty time consuming.   With my 4 bank on board, I plug it in and forget it.  I just top off the AGM before a trip.  My biggest complaint is that my 2005 vintage on board is heavy and now it is trapped in by power pole pumps and one of my batteries.  It has been a great charger though, no problems.  

I keep a couple of Shumacher chargers in my live well.

I trust the onboard  charger lights when they say fully charged. I check  the individual cells in my batteries with a hydrometer and add distilled water  twice  year even if they show  a good charge.

 

On ‎11‎/‎20‎/‎2018 at 7:59 AM, TOXIC said:

I understand your logic but I have 4 batteries and charging them after a trip and then tending them in between trips would be pretty time consuming.   With my 4 bank on board, I plug it in and forget it.  I just top off the AGM before a trip.  My biggest complaint is that my 2005 vintage on board is heavy and now it is trapped in by power pole pumps and one of my batteries.  It has been a great charger though, no problems.  

The time it takes to hookup and unhook the chargers is extremely minimal. Less than two min on each end.  The peace of mind and not having battery problems is well worth the time to me.