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Batteries charging up to 15 volts


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Our boat has two banks of batteries. One marked Inverter which the 240 runs off. The second  marked domestic which the 12 volts runs off. The boat is only used in the summer months. There are solar panels fitted.

 

In 2019 new domestic altinator fitted. 

In 2021 new inverter altinator fitted.

The inverter batteries were new in 2021.

 

Arrived at the boat today to check everything ok. Both battery readings on the panels were 14 volts.

 

I started the engine to check everything is running ok. The battery reading on the inverter bank went up to 15.5 volts. Knowing this wasn't good for the battery I switched the engine off.

 

On knocking off the engine the reading went back to 14 volts.

 

Any ideas?

 

Thanks

 

 

Edited by Steve Manc
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3 minutes ago, Tracy D'arth said:

Any separate alternator controller, Sterling , Advert etc?  If not could be the regulator on the alternator. If its true!

!4v on batteries not on charge is high, not logical, how are you measuring the voltage?

Unless that is what the solar was charging them at.

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10 minutes ago, Tracy D'arth said:

Any separate alternator controller, Sterling , Advert etc?  If not could be the regulator on the alternator. If its true!

!4v on batteries not on charge is high, not logical, how are you measuring the voltage?

Isuzu panel has two readings on it. In the summer the readings were the same as when I tested the batteries individually. 

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8 minutes ago, MtB said:

14.00v on an ordinary rested lead acid battery is not possible, therefore yours are either on charge somehow, or your volt meters are borked. 

Midday today cannot remember if cloudy or not. Therefore some energy from the solar panels may have been coming through.

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25 minutes ago, Naughty Cal said:

Unlikely enough at this time of year to raise the voltage readings to 14v.

 

Not really, as long as the batteries were absolutely fully charged. Remember the open circuit (no current flow) of solar is usually a minimum of 20 volts ish, and house/farm panels may be 30 volts or more. Cold panels and all that.

 

I wonder if this is a feature of some MPPT controllers when to get maximum power to the batteries with all but zero current flow because the batteries are full they would have to boost the voltage to persuade current to flow so AXV gives a positive value rather than zero. Maybe @nicknorman will give his opinion.

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11 hours ago, Steve Manc said:

Isuzu panel has two readings on it. In the summer the readings were the same as when I tested the batteries individually. 

But surely the 2 readings are engine battery and cabin batteries?

How does it split to charge the "inverter" batteries? Its an odd arrangement.

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The charger battery is not on the display panel. Charger battery gets charged when the engine is run.

38 minutes ago, Tracy D'arth said:

But surely the 2 readings are engine battery and cabin batteries?

How does it split to charge the "inverter" batteries? Its an odd arrangement.

 

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Hi All

Thanks for your input.

Yes I ment the Engine / Starter Battery :)

 

 

The charger battery is not on the display panel. Charger battery gets charged when the engine is run.

6 hours ago, Tracy D'arth said:

But surely the 2 readings are engine battery and cabin batteries?

How does it split to charge the "inverter" batteries? Its an odd arrangement.

 

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6 hours ago, Tracy D'arth said:

But surely the 2 readings are engine battery and cabin batteries?

How does it split to charge the "inverter" batteries? Its an odd arrangement.

Not that odd.

we had a separate inverter bank from our domestics. Charged from the heart interface or from the alternator. However it was a very manual system.

When the engine was started as part of the sequence you threw a switch that combined banks to charge all batteries. When you had finished you threw the switch back to disconnect the inverter bank.

it had two benefits firstly if the batteries were low by only initially charging domestic you didn’t smoke the alternator belt, and secondly you could use inverted mains up to a point, and then stop as the batteries went low.

it was a 1996 design no solar panels, 1000 amp hour capacity. Big in those days.

No automatics, you had to be involved in the process, which you were with an engine that involved manual fuel lift to header tank and hand start.

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