Battery charging voltage

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killick

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I am,to an extent, repeating a previous question but please beare with me as I am still somewhat confused.The altenator on my boats engine has been rebuild by not very reputeable dealer.Whilst the regulator seems to reduce the amps satisfactorily as charging progresses the voltage remain at a steady 15 volts which I am concerned may be to high particulary should I motor a few hours. What further agrevates the sitiation is that I have installed a solar panel with a "smart"regulator which means that the altenator will basically always be pumping 15 volts in just about fully charged batteries.The boat is in Durban South Africa where it is very sunny. I will be gratefull if somebody could please share their expertise. Thank you.
 
Check your voltmeter and check the battery manufacturers charging requirements as they will vary with different types of battery. If its flooded lead acid thejn I've copied this but it agrees with my electrical engineering training. 14.4 as a max long term 13.90

Continuous-preservation (float) charging: 13.4 V for gelled electrolyte; 13.5 V for AGM (absorbed glass mat) and 13.9 V for flooded cells

All voltages are at 20 °C (68 °F), and must be adjusted −0.0235V/°C for temperature changes.
Float voltage recommendations vary, according to the manufacturer's recommendation.
Precise float voltage (±0.05 V) is critical to longevity; insufficient voltage (causes sulfation) is almost as detrimental as excessive voltage (causing corrosion and electrolyte loss)

Typical (daily) charging: 14.2 V to 14.4 V (depending on temperature and manufacturer's recommendation)
Equalization charging (for flooded lead acids): 15 V for no more than 2.205 hours. Battery temperature must be absolutely monitored.
Gassing threshold: 14.4 V
 
Best in depth summary I have seen yet! Thanks! What info have you got for calcium batteries? I have read somewhere that they need a higher equalisation charge? (From a battery charger manufacturer I think!)
 
bATTERY CHARGING VOLTAGE

NEIL Y Thank you very much for your reply. The batteries are two 52amp lead acid types.. At the risk of revealing my ignorence could you please advise how I go about to limit the charging voltage to 14.4 ?
 
Neil_Y said:
Equalization charging (for flooded lead acids): 15 V for no more than 2.205 hours. Battery temperature must be absolutely monitored.
Click to expand...

2.205 hours is 2 hours 12 minutes 18 seconds for those of us without watches which measure decimal hours, which sounds implausibly precise to me.

Did you mean we should be measuring the battery temperature in degrees Kelvin? :)
 
Neil_Y said:
Check your voltmeter and check the battery manufacturers charging requirements as they will vary with different types of battery. If its flooded lead acid thejn I've copied this but it agrees with my electrical engineering training. 14.4 as a max long term 13.90

Continuous-preservation (float) charging: 13.4 V for gelled electrolyte; 13.5 V for AGM (absorbed glass mat) and 13.9 V for flooded cells

All voltages are at 20 °C (68 °F), and must be adjusted −0.0235V/°C for temperature changes.
Float voltage recommendations vary, according to the manufacturer's recommendation.
Precise float voltage (±0.05 V) is critical to longevity; insufficient voltage (causes sulfation) is almost as detrimental as excessive voltage (causing corrosion and electrolyte loss)

Typical (daily) charging: 14.2 V to 14.4 V (depending on temperature and manufacturer's recommendation)
Equalization charging (for flooded lead acids): 15 V for no more than 2.205 hours. Battery temperature must be absolutely monitored.
Gassing threshold: 14.4 V
Click to expand...

BRILLIANT. this is the very best and easily the most understandable reply about batteries I have ever read on this forum Well done. Please do keep the info coming.

Fair winds

Peter
 
Battery charge voltage

Firstly you need to be sure your volt meter is accurate. Buy or borrow another one or at least fit a new battery to the digital volt meter and check. If indeed it is 15volts then yes it is too high.
Some regulators are factory set for regulating voltage others are adjustable. If it is adjustable then turn it down to 14v.
If it is not adjustable you could fit a diode splitter to feed both batteries. This will reduce the voltage to something closer to what you want. Or you could just buy a single silicon diode rated at 40 amps or so mount it on a heat sink. A caste aluminium box is ideal to dissipate the heat. An advantage of the single diode is that you could fit a switch for fast charging your batteries ie for a short engine run bypassing the diode. Open the switch for normal engine run. The diode goes between the alternator output and the battery switch.
Another alternative is to buy a replacement regulator. These are often mounted at the back of the alternator opposite end to the pulley under 2 screws and carry the brushes. Hopefully a new reg will give the voltage you want.
A 15v charge will tend to boil off the water in the battery so check water level often until you have solved the problem.
I think however that after confirming you do have 15v charge you should discuss it with the person who rebuilt the alternator. good luck olewill.
 
killick said:
I am,to an extent, repeating a previous question but please beare with me as I am still somewhat confused.The altenator on my boats engine has been rebuild by not very reputeable dealer.Whilst the regulator seems to reduce the amps satisfactorily as charging progresses the voltage remain at a steady 15 volts which I am concerned may be to high particulary should I motor a few hours. What further agrevates the sitiation is that I have installed a solar panel with a "smart"regulator which means that the altenator will basically always be pumping 15 volts in just about fully charged batteries.The boat is in Durban South Africa where it is very sunny. I will be gratefull if somebody could please share their expertise. Thank you.
Click to expand...

Yes you are a bit confused, but never mind.:)

The regulator in the alternator never controls amps. It only controls volts. The amps are decided by the resistance of the complete circuit and by the state of charge of the battery. So as the battery gets filled up, so the amps drop even though the voltage stays the same until the batteries are getting near full when the alternator regulator then cuts back the voltage.

In my boat with a 60 amps max alternator and 300aH of batteries it can take 6 hours or more to get the batteries to the point where the regulator trips in and reduces the voltage to 13.7 or thereabouts. So dont worry - if your batteries are open lead acid then simply make sure that the long periods of 15v dont boil off too much water. Keep them topped up.

Your situation is further complicated by the solar panel which no doubt has its own regulator. Many solar regulators work differently in that they stick at one voltage say 15v and switch on and off at high frequency to avoid overcharging. So if you have the solar panel in circuit it will look as if your charging voltage never drops bel;ow 15v.

To re-assure yourself, disconnect the solar and then run the boat engine until the battery voltage drops back to float level. That will show you that the alternator regulator is working OK.
 
Sorry took a while to get back to this one but both Matelot and William have answered as I would.

First check your meter as others have said, put new batteries in it and ideally get another one so you can compare results with two meters if you have any doubts.

Essentially if the output is 15V the regulator is either wrong or broken. Most regulators are now solid state and should give a max voltage of 14.4V. So change regulator and see if it changes the voltage.

These are usually a small chip mounted on the alternator with several connections as they control the voltage by altering th efield current in the alternator. there are some regulators that are remote from the alternator and some are adjustable. So check through the circuit and see what you have. If it's on the alternator as most are you will just have earth and three outputs. One heavy guage charge wire, one for warning light to show the alternator is charging and one to the battery to supply the alternator with 12v from the battery.

Hope that makes sense, a more advanced regulator is often useful for boats as the domestic batteries have very different usage and hence charging requirements to the starting battery.

This might be helpful
http://www.victronenergy.com/upload/documents/Datasheet - Alternator - rev 03 - EN.pdf
 
Richard10002 said:
If that's a minus sign, the voltage should be reduced as the temperature rises.
Click to expand...


Charge_voltage.gif
 
VicMallows said:
That graph obviously originates from somewhere other than UK.
Click to expand...
Northern Arizona , as you will have already discovered .

BUT if the battery volts rises as it get colder how come a car battery, for example, struggles in cold weather but is fine when its warmer.
 
VicS said:
Northern Arizona , as you will have already discovered .

BUT if the battery volts rises as it get colder how come a car battery, for example, struggles in cold weather but is fine when its warmer.
Click to expand...

I don't think the volts referred to are the potential of the battery, rather the voltages needed to charge the batteries.

Thus, if the temperature rises, the Absorbtion and float voltages should be reduced.
 
Do you have a diode split charging arrangement in the system? If so, where are you measuring the 'alternator' voltage - at the output of the alternator or the input to the battery?

A diode splitter can drop the voltage by anywhere between 0.7 and 1V. To compensate the alternator is then normally wired for remote sensing of the battery voltage. This means that the alternator can be pushing out 15V but the battery will only be receiving 14.0 to 14.3V.
 
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