On board battery charger charging at 13.3 volts

[Wyo85]

Will charging at 13.3 volts only get them to about 80% , and they should be charging at over 14 volts to get them to 100% .

[Kirk W]

That should get them to somewhere in that neighborhood. If you have one of the old style, constant voltage converters that is a pretty normal output but most RVs today have at least a 3 stage converter that can charge the batteries properly. Resting voltage with no charge or discharge when fully charged should be about 12.7V. Float charge voltage is typically 13.5V.

[Wyo85]

I do have the 3 stage converter, it only charges at 13.3-13.4.  I don't think 12.7 volts is a fully charged  battery.  What I heard is 13.5 volts charging will never get a battery fully charged to 100%. 

 

[Barbaraok]

Does it go to float, is that what you’re seeing.  Also what type of batteries, how many, what Male,model of charger, do you have remote data display that shows display stages?  Ours shows red for first stage bulk charging ( where it might go to 14.5) than yellow for remainder of charging, which tends to be 13.5 at the end and then green for float at 13.5.  

[57becky]

Our Progressive Dynamics converter has a Boost mode for when the batteries are below a set voltage, 14.4 volts.  Normal mode is 13.6 volts.  Storage mode is 13.2 volts, but then every 21 hours it goes to 14.4 volts for 15 minutes to reduce sulfation.

[Kirk W]

8 hours ago, Wyo85 said:

I do have the 3 stage converter, it only charges at 13.3-13.4.  I don't think 12.7 volts is a fully charged  battery.  What I heard is 13.5 volts charging will never get a battery fully charged to 100%. 

1

What you are hearing is partially correct. The 12.7V is what we call "resting" voltage. That means that the battery is fully charged and has been open circuit (no charge of discharge) for at least 20 minutes. In order to charge the battery to that level, it will require 14.4V charge in normal circumstances but you do not want that high a voltage kept there once the battery is fully charged. 

I suggest that you read this article on battery maintenance from Trojan battery company. It should help you to understand what you are seeing and how a battery works. 

Just so you know who I am, my background was as an electrician in the Navy followed by a career in electro-mechanical maintenance and 40+ years of RV experience. 

[Al F]

On 3/4/2019 at 11:49 AM, Wyo85 said:

Will charging at 13.3 volts only get them to about 80% , and they should be charging at over 14 volts to get them to 100% .

Yes, 13.3V will charge the batteries to 100%, eventually.  May take 24-72 hours but the 13.3V should get the batteries to 100%.

Most peoples concerns about battery charging happens when they are dry camping or boondocking and want to get the batteries charged quickly.  Even a 3 stage charger, charging at 14.5V, won't get a battery that is 50% discharged, recharged to 100% in only 2-3 hours.  85%-90% yes, but not 100%.