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Car battery question.

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Car battery question.

Old 13th Jun 2014, 00:32
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Car battery question.

Just about to leave my car for 3 months, a Honda Accord Euro, full of all today's computerised garbage.

The battery is only 6 months old and in good shape, and will "probably" be OK, but in the Good Old Days I'd have discnnected it anyway, but I don't want to go to the hassle of having to re-programme everything just to have to start the car, radio, security stuff etc. when I get back if I do that.

I have an ancient trickle charger that has served me well, and which I occasionally connected whilst away, but I'm told that the new, sealed, batteries don't like them, and I should buy a highly expensive "intelligent" charger instead. Not going to.

Question - I have a fairly simple, small, Solar Panel that pushes out about 16 volts on a good day, and am considering leaving it connected to the battery - is this dangerous, computer and modern batterywise ? Can I connect via the cigarette lighter / 12 v. power socket, the cell has a male cig. lighter end on it, i.e. does the charge go backwards up the cig. lighter circuit when everything is switched off, or should I connect it directly to the battery terminals ?

Life used to be simpler before computers.

Any advice, experience appreciated, thanks.

ExS.
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Old 13th Jun 2014, 00:59
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I have a friend with a modern car who lives on an island and can go for a week or two without getting to the (which mis parked on the mainland) car.
He has (as do you) a small solar cell array that is always plugged in (to the lightersocket) and this keeps up with the natural drainage of the system.
He has had no problems whatsoever, so I would say just go ahead and use yours.
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Old 13th Jun 2014, 01:46
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Many car lighter sockets are 'off' when the ignition is off, so check this on your car, as there is no point in having power being fed in here when the circuit is not active. My preference would be to leave the trickle charger connected, but wait until you get some answers here from people who know electrickery better than me.
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Old 13th Jun 2014, 02:02
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In some/most modern cars the cigarette lighter socket is only active when the ignition switch is on.

This means that charging the battery via the cigarette lighter socket would also require the ignition to be on for the circuit to be complete. If this is case with your vehicle, a connection directly to the battery would be needed. Ideally anything so connected needs a fuse in the supply line so that in the (unlikely) event of a short circuit in the equipment, other potential disasters are prevented.

There seems to be no clear consensus whether a regulator and/or blocking diode is needed when a small solar panel is used in such a situation. Some panels may already have the blocking diode installed. (The reason for such a diode is to prevent a slight discharge from the battery back though the solar cells at night time). Several articles suggest that it's not significant in most situations. If there is a controller / regulator in the solar package, this should be managed automatically.

FOR
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Old 13th Jun 2014, 02:12
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I would go to the battery.

My small panel has a diode in it to stop leakage as per post above.

I have known some people to connect a very small light globe to the battery so it cycles down a little bit each day and of course the solar panel charges it up again.

This was before modern cars that obviously use electricity more than old one did.
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Old 13th Jun 2014, 02:36
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My car was left in the garage for an extended period and the battery ran down.

It charged up OK, but the ignition immobiliser acted up.

Car started the first few times but next day it was dead - car had to be scrapped.

Might be worth seeing if there is any procedure you can follow to prevent this happening in case your recharging system stops working.
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Old 13th Jun 2014, 02:54
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AAG - Your battery ran down and you scrapped the car?? That's a little extreme isn't it?? I mean to say, I've heard of blokes selling their car when the ashtray got full, but scrapping it when the battery ran flat?? ...
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Old 13th Jun 2014, 02:55
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AAG

I was wondering the same thing.
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Old 13th Jun 2014, 03:08
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If I leave my car for a couple of weeks the alarm drains the battery. No cigarette lighter per se but a couple of accessory sockets, front and rear, always live, and not through the canbus, that I can plug the solar panel into
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Old 13th Jun 2014, 03:22
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ExSp33db1rd - There are a couple of things we'd need to know, to supply a complete answer.

1. What is the output of your solar charger?
2. Does it have any controlling or switching apparatus built in, to switch off charging when the battery is fully charged?

Lead acid batteries in cars today are generally semi-sealed, low-maintenance, lead-calcium hybrids. They don't like being overcharged.
Charging voltage is critical, it needs to be kept strictly to 2.25V to 2.30V per cell.

A fully charged car battery in good condition should store admirably without charging for 3 mths, provided there's no drawdown.
However, 0.35A is a common parasitic drawdown figure for a connected battery in a car that is parked up.
This means you'll need to trickle charge at that rate constantly - or at a higher intermittent rate, with regular shutdowns when the battery is fully charged.

Overcharging LA batteries generates heat and gassing - and current L-C-H car batteries don't cope with gassing very well, because they either have no venting, or very limited venting.
Thus the case for "intelligent" chargers.
For the cost of a small intelligent charger, I'd be investing in one.

This following website is very informative about every type of battery known.

Battery Information Table of Contents, Basic to Advanced
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Old 13th Jun 2014, 03:38
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Connect your "primitive" charger to the battery cables, but disconnect them from the battery (actually only the negative one). This will supply the power to the parasitic circuits and keep the battery udrained. You only run a risk of losing your radio and other settings if during your absence main power fails.
 
Old 13th Jun 2014, 06:04
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Onetrack
1.What is the output of your solar charger?
2. Does it have any controlling or switching apparatus built in, to switch off charging when the battery is fully charged?
1. No idea.
2. ditto, but none apparent.

In bright sun it produces a "cycling" range of voltage readings from 4v. to 16.v, and in cloudy conditions it barely reaches 9v., measured on a cheap multi-meter, so I don't think it will do any harm, confirmed by a phone call to the local Auto Electrician, but again - who was I talking to and what was his experience ?

Just as easy for me to go direct to the battery terminals,and ignore any on board 12v sockets, so at least I'll do that.

Disinclined to disconnect the battery, tho' I appreciate the theory, in fact aforesaid Auto Elec. admitted that they clip a dry cell 12 v battery to the battery cables when they change a battery for that very reason, but at night - with no solar voltage - and with the battery disconnected the computer stuff may just sat "Sod it" and switch off anyway,which I'm trying to avoid.

Course - I could just read 'The Book' and learn how to re-programme everything, but the Gruntpuddock experience scares the pants off me - it's Mrs. ExS's car - I'm just going to disengage the battery on mine, being a 22 yr. old "basic" car with a battery that one can re-charge and top-up with impunity.

Except that -- last time I disconnected, I turned up back at the airport and couldn't start - flat battery. I organised a drive-by start facility, and when we opened the bonnet to connect the jump leads ................. I saw that the battery had been disconnected !! I'd forgotten !! ( at least I'd remembered where I'd parked it, which was a bonus. )

I may go the "Intelligent" charger route after all, as you say, in the overall scheme of things the cost is hardly worth belly-aching over. ( but why do THEY have to keep changing things ! I had total control over my Dad's 1935 Morris 8, even had a staring handle if things got out of hand, and I even managed to get a speeding ticket on that, never mind today's Rocket Science jobs. )

Thanks for all the tips.
ExS.
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Old 13th Jun 2014, 06:11
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Originally Posted by ExSp33db1rd View Post
... Disinclined to disconnect the battery, tho' I appreciate the theory, in fact aforesaid Auto Elec. admitted that they clip a dry cell 12 v battery to the battery cables when they change a battery for that very reason, but at night - with no solar voltage - and with the battery disconnected the computer stuff may just sat "Sod it" and switch off anyway,which I'm trying to avoid...
That will definitely happen - the electrics all go to sleep when they are not being fed 12v (or at least something close to it) - and probably night 1 . Good thing is it won't spoil your holiday as you won't know until you return, so you will have a holiday in blissful ignorance of what awaits
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Old 13th Jun 2014, 06:18
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An option may be to use your current (ha - see what I did there ) trickle charger through a 24-hour timer (not a digital one that might lose settings in case of a power failure, but an electro-mechanical one). If you set the trickle charger to run for 30 minutes a day it should just top up what the parasitic loss is. Maybe even 15 min in each 24 hr cycle will work fine. I think this will avoid overcharging. (And remember, my advice is worth every $ you paid for it )
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Old 13th Jun 2014, 06:28
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I very cleverly chose to pack one of those cool boxes with a cooling plate built in, on the night before the departure for a vacation trip. Then I connected it to the power point at the back of the car, but connected a trickle charger to the battery under the bonnet. Sorted! Well, except for the fact that the cool box took a bit more out than the charger put back in .... It is a real hassle, finding that little slip of paper with the code for the radio, after already having to have a dead battery replaced at the last minute before a long trip.

I would go for the intelligent charger and leave it at that. Or else, simply disconnect the battery, after first finding that paper with the code for the radio. You might still need a new battery, depending on how long you are away, since batteries lose charge just sat there, and these things with the calcium chemistry, when they go dead, we are not speaking of Lazarus. If the price of the intelligent charger is about the same as the cost of a new battery, well, there is your answer.
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Old 13th Jun 2014, 06:32
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Why not give Honda a quick call as they will know much better than people on here I would have thought? You could also
have a look here :- Honda - Automotive - Whirlpool Forums
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Old 13th Jun 2014, 07:06
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I scrapped the car because, as I stated, the ignition immobiliser prevented it starting.

Local motor electrical guys spent a week trying to fix it but to no avail.

Only way forward was to try a new circuit board and, even if they were still available, there was no guarantee that it would cure the problem.

Cost of the components alone would exceed the value of the car so it had to be scrapped.
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Old 13th Jun 2014, 07:49
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It might be worth checking with Honda to see if disconnecting the battery will in fact cause the radio settings etc to be lost. After reconnecting the battery on my VW the radio does a security 'handshake' with the car's ECU which recognises that the radio uniquely belongs to my car. After a few seconds the radio automatically returns to its previous state including all preset radio stations. The only thing I had to reset was the LCD digital clock.
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Old 13th Jun 2014, 08:10
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ExS.

Do you have the option of leaving a set of keys with a friend? They can take it for a wee spin once a week to keep things topped up.
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Old 13th Jun 2014, 09:00
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Beware the trickle charger without battery

While the idea may seem entirely logical and sensible, I would very much recommend against connecting a trickle charger direct to the car without the battery also being in the circuit.

I have such a device which pushes out over 16 volts with no load and this does not reduce to 13.8 volts - a typical value to be found on a modern horseless carriage while the battery is being charged - until the load is 78 ohms which represents a current draw of 176 milliamps.
There is also the possibility of very small and short spikes of greater voltages being induced by the charger at anytime of connections being made or broken.

Even such momentary transients can easily damage or destroy some of these new fangled electronic gadgets which are often found to be very poorly protected against such grief.

The electrical load of the battery acts as a very substantial buffer to any such interferences and will ensure that no such higher-than-normal voltages can penetrate the system.

jg
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