Battery voltage?

[Andrew_B]

How can I check if my batteries need changing?
When charged the volt meter reads just under 13v.
1 week later the voltage remains the same.
Externally they look fine.
What other tests can I do to determine what state they are in?

Thanks in advance

 

[bigmart]

As a guide a fully charged 12 Volt battery in a rested condition will give a reading of appox. 12.8 Volts.

Mine currently give 12.4 Volts & are working fine.

Martin

 

[boatmad2]

Use a hydrometer to check th SG fully charged is about 1250 flat is 1170.
Leave batterys another week then see if they will start engine if they do are probably in good nick

 

[HaraldS]

The charge Voltage you quote seems too low, the battery will never be loaded fully at under 13V. It should be 14V or more depending on battery type.
Car type slow charging regulators should be about 13.8V
Smart, fatser charging regulators go well up to 14.5V and once reached, keep it there for some hours before switching back to under 13V.
It may be that you measured thatduring phase.
Given the voltage stays almost that high for a long time after charging, you may have full batteries and not much to charge. It would indicate that you have a smart regulator that figutes this out.
If you want to check things work right, turn on as many consumers as you can for some hours and then charge and check the voltage. It should then be above 14V for some time.



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[LadyInBed]

Re: hydrometer

You can get an almost foolproof hydrometer.
Instead of a caliberated scale it has five coloured balls in the tube.
You just count the number of floating balls:
1 - 25% charge
2 - 50%
3 - 75%
4 - full charge
5 - over charged

 

[aztec]

if they are starting batteries, the best test for a charged battery (to see if it's in good nick) is to drop test it.

this comprises of putting the battery under a test load, and checking for 2 main things, firstly the voltage drop during the test, and more importantly gassing of the cells, this indicates that there may be a problem with one or more cells.

you need to speak to your freindly battery company and ask them if they'll perform this test (you may want to contribute to their tea fund)

there is another way of doing the test, but if i told you on here i would receive death threats!

all the best, steve.

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[jimboaw]

Re: hydrometer

it is important to remember that your batts must have been rested, no charge or discharge, for at least 24 hours before any hydrometer reading is meaningful.
Nigel Calder's (can't remember the title!) book is very informative on the subject and, IMO. a "must have" on board.

 

[colvic]

WRONG.

When charging with a "smart type" charging system such as Adverc, in my opion superb, the charge voltage builds up slowly depending on the state of the battery building upto 14.5v+ for just 15mins. maximum, then a drop to a lower voltage and then another 15 mins. at 14.5v+ for upto 3 cycles an hour. If you do not drop the high charging voltage every few minutes you then create gassing which quickly kills the battery as the plates get ruined very quickly.

The best advice is to go to the Adverc web site or give them a ring, Brian is very helpful.

The original question about voltage level in a battery expected to be charged and presently off charge is approx 13v. and if it is still 13v. after a week they seem fairly OK


Phil

 

[halcyon]

Colvic that charging cycle is the same as the one sold by Hella years ago, used to sell it around £80.
Stopped selling them about 6 years ago, we were looking at selling there system as simpler than designing and developing our own, project put on back burner then.

Brian

 

[HaraldS]

If I would use your style, I would start out saying that you have a misconception about gasing and of batteries and its consequences, but I shall not.

A battery that has reached a certain charge level, say 85% or above, will ALWAYS gas if charged at a higher voltage. It will gas for exactly 15 minutes in your example and stop gasing for the time that you're at a lower level, just to start gasing immediately when you get back up to the higher level. The amount of gasing wil depend on the voltage level only.

For some batteries, like good truck batteries, some anount of gasing is healthy, and actually better than none; for a gel battery it would be deadly, so that in the voltage level needs to be kept lower, which also means you can't charge them as fast.

Some smart chargers do what you describe, but more for the reason to see at what level the battery settles when switching off charging for a short moment. In addition some factor in battery temperature, because that influences the gasing voltage.

The simple fact is that you can charge a battery at full power, (as much as you may have), up to about 85% charge, and then it will start gasing if you don't slow down. How you do the last 15% depends on battery type and different regulators vary in their approach.

I have not measured the Adverc you mention, but a few others, so can't comment on it. The better ones factor in temperature as I said, some try to guess on charge level by pausing the charge process to see what the battery does. Unfortunately the outcome of that depends a lot on the current consumption of power relative to bank capacity, so is not a bullet proof approach.

To clarify: Gasing only kills gel batteries, it just consumes water on regular liquid batteries and actually helps stirr up the electrolyte.

Second: The level of a full battery off charge is 12.8V and it will stay there for a long time if the battery is healthy and the consumption low.

Finally: A low charging level, as the one mentioned, will only occur when the regulator decides that the battery is full and goes to float mode. Only a smart regulator will do this at some point, a car regulator will stop and stay at about 13.8V.

Hence I suggested that our friend might see a higher charge voltage if he would discharge the batteries before charging and measuring.




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[halcyon]

Batteries will start gassing around 13.8 volts, which is why car regs and float charge was set at 13.6 volt. Now car alternator reg is around 14.4 volt, does anyone concider this when buying flash batteries for there car.
Back it the early 80's when we were designing our first battery chargers ( the days of Constavolt ), we found out that charging to 13.6 volt actually reduced battery life. Once you started gassing it mixed up electrolyte and gave a better capacity/life. We also found that equalisation charging gave little extra capacity, but just caused heavy gassing depending on system, we went with charging to 14.2 volt, then going to 13.6 volt float.
The main problem is that required voltage levels can vary with air temp, air pressure, battery temp, age of battery, type of battery, battery maintainance, in the end it's mainly trying to design the best compremise.

Brian

 

[MedMan]

This thread has developed into an interesting debate on voltage and charging rates but I note you actually asked 'How can I check if my batteries need changing?' Measuring Voltage alone cannot answer that question.

As a battery ages it looses capacity, manly through sulphation of the plates. In effect, as more and more plate area becomes unusable, the capacity of the battery decreases. If you start off with a 120 amp hour battery, its effective capacity will reduce to 100, then 80, then 60 amp hours and will continue downwards until it becomes no more than ballast. In practical terms. once it reaches half its original capacity you really should be changing it.

The voltage readings from a battery that has lost, say, 40% of its original capacity will be much the same as from a new battery. The area that has not sulphated will still accept charge and will rise to 13.8v (or more with an intelligent regulator) and drop back to 12.8v fairly quickly under load, just as a new battery will. The chemical reaction is just the same - its just that there is less active plate area capable of performing the reaction. The difference is, how long can you draw a load from the battery before its output voltage takes a sudden nosedive to 10.5v or less because it has run out of active plate area.

The best way to find this out is to do a discharge test. This is detailed in Nigel Calder's excellent book. Batteries sold in the UK are usually rated at the 20-hour rate. i.e. the rating given assumes the battery is being discharged from full to empty over a 20 hour period. If you have a 100 Ah battery, that would mean drawing a constant current of 5 amps for 20 hours. (If you draw at more than 5amps you will get less than 100Ah even from a new battery as it is less efficient at higher discharge rates) So, if the battery you are worried about started its life as 100 Ah, charge it up fully and then switch on a carefully calculated number of lights so that you are drawing 5 amps (pro rata for different battery sizes of course) This is much easier if you have a battery monitor as you can read the actual discharge in amps straight off. Now just time how long it takes to reach the critical point when the voltage takes a sudden nosedive from around 11.5v to 10.5v in short order. On a new battery it should take 20h of course. If yours takes less than 10, you need a new one!

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[jfkal]

Always good to have people on the forum who know their stuff ;-))
How would you treat a flooded but sealed battery. I set my chargers to GEL in order to avoid gassing. Would you agree?

 

[JamesS]

Just to endorse this post. The battery SG is the only foolproof method of determining battery condition. Terminal voltage does not tell the STATE of the battery.

Unfortunately some batteries are now 'sealed for life' (the life of the battery that is - not the boat) or are gel filled so taking the SG is not an option.

Faced with this you will need a load test which can be carried out in a few secs by the battery supplier, or take it along to Quick Fit.

Cheers

 

[mtb]

Re: I cant beleive this lot

I read through this lot thinking all their talking about is point this and point that !!!!! still that's blokes for you .

A rapid discharger is needed !!! , you know the type, they have a large coil which heats up thus discharges your battery at a rapid rate . My unit is an Oldham and it was a valuable piece of kit when years ago I was a Mobil mechanic
( NO not like the RAC )
The pass voltages are from 7.5 to 10.0 , this unit you press the button for ten sec's and watch the meter example a 121-170A has a pass voltage of 8.5 .
As James S said ( he was the only one !!) take it to any of the battery people they all have this equipment.
No one talked about the build up of sediment at the bottom of the battery ? causing cells to discharge.
lead acid batteries are designed to last two or three years any more than that and your doing well.
Ways to help your battery last longer , place them in a nice insulated box which has rubber matting to sit em on .
Check the fluid level's and if not in a posh box keep the tops clean as they will discharge between terminal posts
Use them , don't expect any battery to sit there doing nout during the winter . In the old days, during the winter yard's had a shed full of boats batteries keeping them charged giving a bit of discharge , all part of winterisation . Bring em home and keep them in your garage , trickle charging now and then but don't forget to give en something to do as well.


Cheers
Mick

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[Roberto]

Battery testing

Andrew, this link should answer your question

http://www.uuhome.de/william.darden/carfaq4.htm

 

[HaraldS]

Using GEL setting is definitely a very safe and conservative approach, at the expense of longer charging time. All types of sealed flooded batteries will accept higher charging volatges than a GEL battery. Fully maintenance free batteries are usually Lead-Calcium / Calcium and can take quite a high charge voltage and you need to see the data quoted by the manufacturer to be sure.

Here is a table of approximate values for different battery types:

Battery Type Charging Voltage Float Voltage Equalizing Voltage

Wet Low Maintenance 14.4 13.2 15.1

Wet Maintenance Free 14.8 13.4 15.5

Sealed &VRLA 14.4 13.2 15.1

AGM 14.4 13.6 15.5

Gel Cell 14.1 13.2 N/A

Wet Deep Cycle 14.5 13.2 15.8

You can see that the maintenance free battery is listed with the highest charge voltage.

I have no personal experience with sealed batteries, but theory says they are better in most respects, except they can be broken easily by a deep discharge, and they age faster in hot climates.

I'm currently using HD truck batteries (semi tracktion), which are built very robust (for lorries and busses), can take a reasonable amount of discharge (say down to 40%), have a huge water reserve, so that you don't have to check more than once a year, and they have sealed caps and a gas collection canal with a hose connector. So in my case gas vents outboards right away.

The plan was to use those relatively cheap batteries for four years, and then replace with something like GEL or AGM when I will be in areas where you cannot get replacement batreies for some years.

Now after three years the cheap batteries show no sign of age or loss of capacity, so I'm not sure what I will do in a year and a half when I have to decide.

What I dislike on the GEL batteries is that I cannot charge them as fast, AGM have a different form factor and are hard to get in Europe.

Anyway, if I'd stick around the civilized part of the world, I would now always use flooded batteries.



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[Arturas]

Visit address http://www.attfield.dircon.co.uk/ and "related topics". There are plenty of information to understand "what is what".

 

[jfkal]

Thanks Harald.

Joerg