Car battery charging what is going on?

[ericmark]

I use a smart charger, and normally I will monitor the power into charger, and when it drops to 2 watt which is 0.1 amp I know battery nearly charged, I will wait a little longer and when I open bonnet want to see volts on charger over 12.8 volt, which confirms fully charged.

The charger will often alternate between 0.8 amp and 0.1 amp at the end of the charge a few times, the charger will switch to 0.1 amp when volts hit 14.4 volt, and return to 0.8 amps if the volts drop below 12.8 volt, it starts charging at 3.8 amp, then drops to 3 amp but not really interested in the first to stages, it is when battery is fully charged which is of interest.

The Kia Sorento is parked at bottom of the garden, to far from house for one extension lead, so I charge the Honda Jazz at the same time, and use the bonnet space of Jazz to protect the extension lead plug and socket. The net result is I don't charge the Sorento very often, so this time Sorento battery 95 Ah was under 12 volt when put on charge, far lower than normal.

So this is the charge rate as the Sorento hits 14.4 volt and first drops to 0.1 amp charge rate, and you can see twice an hour the charge rate rose to 0.8 amp, and a few days latter this is the charge rate where it goes to 0.8 amp 7 times an hour, OK only 1 minute long each time, but the voltage is now dropping faster than when it first started to pulse, which seems wrong way around, in the past the time between the 0.8 amp charges as increased as battery became more charged not not decreased.

The Jazz battery 35 Ah has stayed at 0.1 amp and the volts have slowly risen to 13.8 volt, and in the past the Sorento has taken longer as bigger battery, but has also risen over 12.8 volt with just a 0.1 amp charge rate, so a little puzzled as to what is going on.

 

[Mottie]

Eric, you're thinking too much. Just charge the batteries and drive the cars.

 

[ericmark]

We are in lock down, can't drive the cars. I can't drive them until 9th of November when the fire break ends.

There is as far as I can see, no problem, however I can't understand why, as the battery reaches 14.4 volts it reduces charge rate from 0.8 amp to 0.1 amp and as one would expect the voltage will fall again, however why should the rate of fall increase? I can see why as the battery creeps into fully charged status how the time to reach 14.4 volt decreases, so the time at 0.8 am will decrease, but can't understand why time at 0.1 amp has also decreased.

 

[ericmark]

Start patten when dropping to 0.1 amp and patten this morning as said understand why it stays at 0.8 amp for shorter time, but not why also stays at 0.1 amp for shorter time.

 

[AndyPRK]

what brand is the charger?
CTEK ?

 

[ericmark]

Two Lidi chargers, look very like the Ctek but have built in voltmeter, work both 6 and 12 volt, and very much cheaper, it explains the final stage, at 12.8 volt it raises output to 0.8 amp and at 14.8 volt it drops to 0.1 amp, if at 0.1 amp it hits 14.4 volt then switches off.

With the other large batteries 90 Ah AGM in fullness of time at 0.1 amp it will reach 13.4 volt off the car, and 13.1 volt on the car, but looking at a week, lets face it 0.1 amp is a very low charge rate.

In the past it has charged the Kia battery up and the volts have gone to over 12.8 volt at 0.1 amp so charger has simply sat there maintaining the battery until I have decided to move it, I have 10 lead acid batteries at 2 chargers, not counting the old 12 amp charger or radio power supply, so the norm is to move from one battery to next. When I see on PC 0.1 amp charge rate for 12 hours or more, I assume that battery is fully charged.

But setting out the extension leads is a pain, using the cat flap to get out of flat, so I have missed charging the Kia, never had a problem starting or flat battery so ignored. And drivers error with the Jaguar XE means I have a spare 90 Ah AGM battery, changed as thought battery faulty, turned out wife not pressing break peddle hard enough. We had kept old battery for caravan, but turned out it was A1 anyway.

So interest only, why does the volts decay faster the more charged it becomes, I would have expected the reverse.

 

[AndyPRK]

Maybe you need a solar charger. Should be ok for the smaller cars.

I had been pondering an XE

 

[ericmark]

It seems the pulses are getting less frequent so it would seem likely it will stop pulsing given a little more time, the charger shows fully charged, it is the energy monitor which is allowing me to see what is going on. Until a couple of years ago I did not realise how much time is important with battery charging, I tried to recharge 2 x 7 Ah VRLA from a stair lift when the owner had switched off the charger, and batteries replaced and old pair mislaid for 12 months. Had to cheat and charge in parallel with a good battery to get the charger to work, and for 10 days nothing, then as if some one flicked a switch they fully recharged.

Normally I would not consider leaving a battery 10 days on charge, well not on charge as nothing seemed to be going into the battery, just on the charger, but after the 2 weeks they seemed non the worse for being nearly 9 months left fully discharged.

I am guessing the Kia battery has some sulphation and the charger is slowly removing it, but not seen this charge patten before, can't drive anywhere until the 9th when the fire break ends, so no harm seeing what happens.

The question is in the past have I been too fast condemning a battery, did I simply not leave it long enough, and if it takes a week or more for a battery to fully recover, can it ever fully recover on the car, unless using other than car alternator to recharge.

So @AndyPRK may have a good point, maybe solar panels should be built into our cars to stop self discharge when laid up for a long time, seen them used with caravans, but not cars.

 

[AndyPRK]

You can buy solar charges off eBay for cars. Small ones you just place on the dash. They may appear small but do the job. You don’t require an extension lead so often

 

[ericmark]

I had one for caravan to keep battery topped up, was not really a success, battery still went flat, may have taken longer but was not impressed, ended up removing battery and bringing it home to charge.

I am reasonable sure the Kia would have started. But big question is would the batteries capacity be reduced as not fully recharged? Where the car is used 5 days a week I am sure the battery would recharge, but used once a fortnight not so sure.

I remember my father-in-law who lost his licence trying to move his car, he loved his cars, and it was parked in his garage, my garage can't even get car through the doors, but his the bonnet was tucked under his work bench with wheel stops bolted to floor so he would drive in exactly right amount, sponge on walls to protect door when opening, but the battery went flat, and he could not remove the hand brake without charging the battery, and could not open doors to rear seats, ended up with trolley jack under back of car to get it out of garage enough to open bonnet to get to battery to charge it.

At least wife's car battery in boot and charge point under bonnet so either boot or bonnet up can charge battery, however not sure could open boot with flat battery. Or even open car doors to release the bonnet? What was wrong with keys?

But 95 Ah at 0.1 amp is 950 hours, about a month, so can't really expect the battery to respond fast, it is only likely just above the internal drain on the battery, had the car around 4 years and never renewed battery, however once I take it off charge it will likely sit unused until Christmas, so makes sense to ensure fully charged before removing charger.

 

[Mottie]

Or even open car doors to release the bonnet? What was wrong with keys?

Every car I know that has remote/keyless entry also has a key blade within the key fob for just this eventuality. The lock is accessed by flipping off a cover on one of the front door handles - usually the passenger side. It doesn’t hurt to use and/or lubricate this key barrel now and then to stop it stiffening up through lack of use.

 

[AndyPRK]

I don't think the windows in a caravan are suitable for solar charging.

I've successfully used solar chargers in cars by placing them on the dash or the rear parcel shelf.
They are great for keeping the battery alive. Helping their life.

 

[ericmark]

I have one at caravan once the Welsh and English lock downs are both over I could get it, but by then will not be required. I had intended to visit caravan end of lock down, but the staggered lock downs not only don't make sense, but means 6 weeks we can not visit it to do maintenance.