Normal or something draining?

[Pablo19]

After recently getting my Truma iNet working I've started taking much greater interest in my battery voltage readings. On a day like yesterday (hot) my solar set up (100w) was obviously fairly effective and the batteries were showing a voltage of around 13.4v for starter and 13.3v for leisure. This morning they were both showing 12.8v. I know that's still a healthy voltage but should they be holding closer to the reading from yesterday or is this completely normal?

 

[Guigsy]

Depending on the battery type, it sounds like you're fully charged. Anything over 13v isn't the battery charge, it's from whichever charger is on at the time. If you really want to know the state of your battery, voltage is only a rough guide. Shunt based monitors are more accurate.

 

[pappajohn]

On charge the voltage should be around 14v if the solar is the only charge and it's in full sun.
Regardless, 12.8v is a little above expected.
Charge voltage will always be higher than the resting voltage so I would check with a multimeter at the battery.

 

[Pablo19]

Depending on the battery type, it sounds like you're fully charged. Anything over 13v isn't the battery charge, it's from whichever charger is on at the time. If you really want to know the state of your battery, voltage is only a rough guide. Shunt based monitors are more accurate.

The battery type is gel, Exide ES900s working in parallel. I thought what you say was the case but thought I would double check! Thanks

 

[Pablo19]

On charge the voltage should be around 14v if the solar is the only charge and it's in full sun.
Regardless, 12.8v is a little above expected.
Charge voltage will always be higher than the resting voltage so I would check with a multimeter at the battery.

Yes, I would have just done that but the terminals aren't very accessible! Thanks

^{_{Subscribers  do not see these advertisements}}

 

[autorouter]

The resting voltage of a battery varies from about 12.0V to about 12.7V, depending on its state of charge. If the resting voltage is say 12.5V, then you might expect that if you applied 12.6V to it, from a charger, then charge would flow backwards into the battery from the charger. However it doesn't quite work like that. You have to apply more like 13.2V before any measurable charge flows into the battery. And to get a good current flow then anything up to 14.5V is required.

So as pappajohn says, if you look at the voltage across the battery terminals while the charger is connected, you won't see the resting voltage, but only the charging voltage. That doesn't tell you any thing about how charged the battery is.