Battery charge holding

[mikey9]

Have split charging circuit - have been taking voltage readings (no load) before and after a run and overnight - then observing the voltage drop over the following day(s). If anyone can make sense of the readings and their indications I would appreciate comments.

I am interested in whether these kind of drops are typical or are indicating tired batteries.
The Vehicle batt is > 3 yrs old and easily starts every time (lowest reading has been 12.39v)
Leisure is <2yrs old (75A Starter battery)

As we have a couple of weeks booked on the West coast and Scottish Islands - with several days at one spot with minimal vehicle charging expected - I want to be confident the leisure batt isn't going to die on me. We have minimal usage with radio, a couple of lights, lpg alarm (overnight), and some use of the heating expected - poss also a phone charger......

After charging run (15 miles)
Vehicle battery 12.92v
Leisure battery 12.88v
then...
Aft 2.5 hrs
Vehicle battery 12.52v
Leisure battery 12.43v

another set of readings
Morning before Charging run (15 miles)
Vehicle battery 12.38v
Leisure battery 12.15v
then....
After Charging Run
Vehicle battery 12.95v
Leisure battery 12.88v
then.....
After 8 hrs (nothing turned on)
Vehicle battery 12.56v
Leisure battery 12.33v

and another
Before charging run (15m)
Vehicle battery 12.48v
Leisure battery 12.18v
then....
After Charging Run (15m)
Vehicle battery 12.84v
Leisure battery 12.62v
then....
After 4 hrs (nothing turned on)
Vehicle battery 12.60v
Leisure battery 12.27v
then...
After another 3.5 hrs sitting (nothing on - not me - the van)
Vehicle battery 12.56v
Leisure battery 12.23v

[VWCamperfan]

Those voltage readings and times seem about right for the age of the batteries. I'm guessing you havn't had any problems with them in the past looking at the voltages you have but if you want peace of mind for your trip, take them out (if you have to!) and fully charge each one overnight on a conventional battery charger, just to be sure.

[mikey9]

Thanks vwcfan - my wife asked me ..."how will that help though..." I tried to bluff an intelligent answer but couldn't give one

Why will charging using a charger be better than using a 200 mile round trip we have planned using the split charging circuit....?

[AngeloEvs]

In a nutshell, It won't! The only benefit is that the battery will demand less from the alternator when you set off. Is your leisure battery a starter battery? If it is, and you have any doubts, it can be tested (for free) by any good battery supplier. They can measure the actual performance and tell you its charge holding ability.

[kevtherev]

Why will charging using a charger be better than using a 200 mile round trip

Well it won't do any harm will it.

[rick]

its also thought by many that a slow charge (trickle) is better than a high current charge from the alternater. im not sure if there are any facts to back this up, but ive heard it from many. and i always put my leisures on a 4 amp charge for the full day before we set off anywhere.

[AngeloEvs]

Three stage chargers which use a high frequency pulses will improve the performance of older batteries..........absolutely correct and worth pointing out!

[VWCamperfan]

Most 3 stage chargers won't pulse unless they have an integrated desulphation circuit. They are just designed to provide 3 different levels of charge to a battery to achieve optimum charging within the batterys current condition. Having said that, most desulphation chargers are a complete waste of money too! Most of them tested gave a worse charge than a conventional charger... All for about 8 times the price!
The best desulphation circuit you can get is home-made with a few basic electronic components... knocks that layer of sulphation straight back into the electrolyte... Where it should be!
A vehicles alternator when charging, charges too quickly for the desulphation process to take place, thats why you have to replace your battery after a few years. Regular trickle charging helps combat this and extends battery life. It's not all about having a good voltage and ampeage supply that keeps a battery alive!

[AngeloEvs]

most desulphation chargers are a complete waste of money too! Most of them tested gave a worse charge than a conventional charger...

Most is not all! Design is a compromise and always will be, a pulse mode charger by its very nature will never give the same charge rate but offers a balance between charging and de-sulphating for exactly the reasons you have pointed out. Having said that, I only use a bog standard cheapo three state charger...........and very occaisionally...... my Alternator does the job 99.9% of the time. It's spinning down in the back end so it might as well do sommat bloody useful .....and quickly!

[bigherb]

Looking at you figures you have a low surface charge after a run if the alternator is charging correctly you should be looking for over 13.5v what is the charging voltage with the engine running.

[mikey9]

charging voltage is always giving over 13.5v

[jamesc76]

The longer it takes to charge a battery ie trickle charge the less chance of the battery siulphating (gassing) Plus it stops the plates from "furing"up, one thing to piont out is once your have charged a battery and you put your multi metre across it you often get false readings best to connect a light to it that way the battery voltage you read will be the true voltage you only need put the light etc on for a little while ie 1 min. If your thinking of going away in the van and parking up for a few days i would recommend a proper lesuire battery if you can get one as they allow a lot longer use before the need to recharge, plus unlike vehicle/starter batterys if they go below about 9 volts theres a good chance you can wreck it where as a lesuire battery wont (deep cycle )

[eatcustard]

My starter battery sits at 12.63v (I gave it a charge last weekend)
and charges at between 13.9-14.1v with engine running

[jamesc76]

Just found what I was looking for as for battery status:

Specific gravity voltage at battery State of charge

1.280 12.8v 100%
1.238 12.5v 75%
1.200 12.2v 50%


Ok a few will know what specific gravity is but dont really need to know

As long as you get over 13.4v when charging all should be good

[bigherb]

charging voltage is always giving over 13.5v

Charging voltage should be minimum of 13.8v ideally 14.2v. If you have Calcium of Silver/Calcium batteries fitted which are not ideal for older charging systems like T3's you need 14.6v otherwise the batteries will never be fully charged and lose their capacity due to sulphation. Eatcustard's voltage readings are pretty much spot on for a T3 charging system.