How do I test my batteries?

[larht]

This spring I upgraded my trolling motor from 12v to 24v,I got a motorguide digital 82lb thrust unit.I had it professionally installed with two brand new batteries.

I have mostly been using it on electric motor only lakes and until last weekend,no problems. I got halfway up the lake,About 30 minutes of running time, and started to lose power,so I turned around and headed back to the launching area and with the help of my fishing buddy and his constant paddlingwe made it back loaded the boat and headed back home.

I called the dealer that installed the unit and he said that the batteries have a "memory" and that if I don't discharge the batteries low enough before recharging them that I may have this problem again.

I have two questions

1. Is this so much bull?

2. What can I buy to check the level of charge in my batteries before I leave home so this does not happen again?

[TopDog]

Take them to sears, They will check them for you.  Im sure any auto parts store can do it too.

[Jig Man]

If trolling motor batteries have a memory, that is news to me.  There are a couple of things you need to do to keep the batteries in top shape: 1. check them regularly for water loss, and 2. always charge them with 24 hours after you get off the water.

You can buy a hydrometer at a Wal-Mart of auto parts store and check the cells.  They are handy to have and cost less than $10.

[larht]

I believe the batteries are good. They're brand new!

I did test the batteries for water level and they were full and I always hook them up to the charger as soon as I return.  

I guess I suspect my charger may not be doing it's job,but when I initially plug it in I get the red light which indicates it's charging, then later on, the light is green which indicates it is fully charged.

I don't want this to happen again.so I don't know if I need a multimeter or if I need a "toaster" (load tester?)  to determine the shape of my battery before I hit the road again.

Lucky for me, I wasn't too far from home. but what a pain if I had been.

[surfer]

A hydrometer can tell you the most, but electric voltmeters are easier.  Your fish finder should have one on it.  

12.66V   =100%    

12.45V   =      75%    

12.24V   = 50%    

12.06V   =      25%    

11.89V   = 0%    

http://www.interstatebatteries.com/www_2001/content/faqs/tech_talk/maintenance/ocv_chart.htm

You are correct that lead acid batteries do not have a memory.

You are correct in charging them ASAP after use.  

I would call and inform the dealer of his error in knowledge of his product.  If he is unwilling to agree and educate himself on his own products I would not trust his advice on any products he sells.  He may be purposefully advising clients to kill their batteries and then buy more from him.

Google search Deep Cycle Battery Maintenance for more in-depth info.

[George Welcome]

A battery can go bad in the blink of an eye. A volt meter will not tell you much. If you do not have a load tester than take them somewhere to have them checked. Discount Auto and so on will all test for free. New batteries go bad also. I just had a two month old Delco Voyager go south. Unusual but it happens.

[NBR]

As said lead acid batteries have no memory. I have both a specific gravity tested and a voltmeter to check the batteries. Both work but I find the VM easier and I'm not dripping battery acid over everthing.

Have the batteries load tested which they can do at Sears, Wall Mart or most any automotive supply house.

Are you connections clean and corrosion free? Corrosion can impede charging and rob power to the motor.

[kybassangler]

I grew up in a service station and what dad would have done would be to check the water charge the battery overnight then load test it. But also I didn't see anybody tell you to check the connections sometimes connections could fail. 24 volt motor won't do much with 12. proffessionals can have off days too.

[larht]

Yes,  the connections are all corrosion free but, just to make sure,  I cleaned everything.

[larht]

Yes,  the connections are all corrosion free but, just to make sure,  I cleaned everything.

[HPBB]

The same thing happen this spring with my MG 109# 36volt TM, One battery went south and it would draw the others down. Only would hold a full charge for a little time. Check the water levels first. Then if that is ok put them on the charger and make sure they are charged and take them to any autozone, advanced auto, ect and they will check it. If they load test them and they are bad get two new ones, don't mix batteries. If they say that your batteries are not at full charge then that could point at your charger.