Thread: Battery question

How do you know they were 100%? A full charge should read 12.7 or 12.8. Yours are reading almost completely discharged, 12 volts is about 25% charged. By the way, you should always check and fill with water before you charge them. If the water were to get below the top of the plates you could damage your battery.
SeaRay

When you added the water it dropped the charge down. You were right to charge ( as long as the plates were covered) then add the water......but then you should have topped the charge off. The reason for chargeing before adding water is....If you don't you could over fill them .....chargeing will make the electrolite expand. I leave my onboard charger plugged in all the time so mine are always charged when I add water and then they are charged a little again afterwards.

Originally Posted by KDAVID1

Ok so a couple of weeks ago when I filled my batteries up with water (after they were charged)

Charge them AFTER topping them off

12.1 volts is 50% discharged

I was a little off on my charge rates, Senior moment. Here is a charge chart.

State of Charge	12 Volt battery	Volts per Cell
100%	12.7	2.12
90%	12.5	2.08
80%	12.42	2.07
70%	12.32	2.05
60%	12.20	2.03
50%	12.06	2.01
40%	11.9	1.98
30%	11.75	1.96
20%	11.58	1.93
10%	11.31	1.89
0	10.5	1.75

Originally Posted by SeaRay

How do you know they were 100%? A full charge should read 12.7 or 12.8. Yours are reading almost completely discharged, 12 volts is about 25% charged. By the way, you should always check and fill with water before you charge them. If the water were to get below the top of the plates you could damage your battery.
SeaRay

the 12.0 and 12.1 was two weeks later and after a full 9 hours of trolling. the day I used em last they were full of water (and still are) and should have been fully charged (were hooked up for a week before I used them) I say 100% because there is no way (in my mind) I could have trolled for 9 hours on anything less than 100% but I don't know.

Originally Posted by KDAVID1

the 12.0 and 12.1 was two weeks later and after a full 9 hours of trolling. the day I used em last they were full of water (and still are) and should have been fully charged (were hooked up for a week before I used them) I say 100% because there is no way (in my mind) I could have trolled for 9 hours on anything less than 100% but I don't know.

You can't check voltage just after charging or discharging, it needs to be "at rest" voltage, otherwise you'll get inaccurate readings.

Originally Posted by NeonMoon

You can't check voltage just after charging or discharging, it needs to be "at rest" voltage, otherwise you'll get inaccurate readings.

yep--they were at rest today when I checked (before I plugged them in and after I rechecked the water-it didn't need any) Haven't had them plugged in for 2 weeks. I did plug them in after I filled with water 3 weeks ago. It's just the 3/4 charge showing in the TM meter two weeks ago that had me concerned--like they didn't fully charge last time? I'm guessing now it's just the stupid meter on the TM--it has acted goofy before. Thanks for the charts two--that is very helpful.

I'd put more faith in what my volt meter says than what the TM says.