Charging Battery
 

Has anyone had any problems with fixing the battery charger directly to the battery without removing any leads.

I've done this in the past on previous cars without a thought, but I'm now increasingly aware of all the computer modules in the car that can be affected by transients caused by imperfect DC voltage and so have always removed the negative lead first.

Any thoughts would be appreciated as removing the negative lead would be one less job to do.

I've fixed a battery charger onto mine before whilst poking around with the CANBUS for hours, didn't have any issues.

However, if you're doing it purely to charge the battery. It would make sense to disconnect it from the car first.

on a similar topic, I've been thinking just as a precaution (and for leaving usb things charging in the car when camping) of the following setup..

Solar charger permanently fixed in one of the boot side windows such as this for example (or one that looks better maybe)

solar charger controller to avoid overcharge and provide additional outputs like this

connect directly to battery and just leave it permanently attached

is that a bad idea for any reason I haven't considered

apologies for thread hijack but it's along similar lines

Nice idea, I could hook up my 10W solar panel for the 2 week periods I don't use the car. In which case, I might not need to charge up the battery at all.. Also there's no need to worry about transients because it's pure DC.This may just keep the battery from draining too much, although it depends on the drain current from the car's system.

10W, should give 0.83A, that's in full sun. In reality it gives 0.5A on a bright day and less than 0.2A to nothing on a cloudy day. At a rough guess, this equates to an average of 0.3A for 7 hours (2.1Ah per day), because the days are getting shorter and mostly cloudy. I suppose that equates to 30Ah for a 2week period.

The panel you describe 8W should give 0.65A max. In the summertime it would trickle charge you battery. The panel will have a built in regulator to ensure that you don't put large voltages directly to the battery. As for overcharging, I wouldn't worry about that, the sort of current it supply's will not harm a lead acid battery even if it's topped up. Probably going a bit overboard with a 30A solar charger though, it would probably suck more current than the panel can supply.

There will be no issues connecting a charger directly to the battery, contrary to some opinions car electronic modules (especially Volvo) are very robust and car batteries are the best surge protector available...

Connect positive to battery negative to chassis earth

If you need to charge it after a couple of weeks standing, it could be the battery is getting weak, or there's a drain?

Mine will happily start with ice on it after standing for 3 weeks at an airport, so it shouldn't really be a problem

I've used a small solar charger on several vehicles, it's enough to replace a small current drain from the battery. I've found they work better when placed on the top of the dash, obviously subject to shade. It means have a longer wire to get to the socket in the rear but for occasional use it wasn't a problem.

With mains chargers I've always used the terminal under the bonnet, I've never had any problems with not disconnecting the battery but I've always used an electronic, regulated charger/maintainer. Some of the older high current unregulated chargers can generate voltages well over 25 volts, personally I'd rather not risk it.

A point involving AGM batteries.

In brief, I've read that old fashioned chargers -ones we'd commonly attach and leave for days- are OK for charging an AGM battery except for the home stretch.
The warning is that as AGMs approach full charge, the charging voltage must be lowered. Continued over-charging of a near fully charged AGM is deadly to them.

Newer chargers with proper circuitry are what's called for. This "accommodation" is what battery addressing in some new cars is for.
Some newer chargers I've seen have other features such as "dead battery resurrection".

Also, as many who work in garages have posted, I'll only replace a battery with a like kind.

Thanks for the comments everyone.

I feel more at ease now just hooking up the charger without removing any leads, the battery certainly serves as a big smoothing capacitor and yes it looks like my battery isn't holding charge like it should. I've had the car two and a half years now, and have no idea how old the battery is. Just checked the voltage to find that it's registering 12.2V after a week on the drive, which Is not brilliant.

I never thought of putting the charger on the terminal under the bonnet, that's a lot less hassle than unbolting plates to access the battery itself.

I've put the 10W solar panel on just to see how effective it is. Yesterday in bright conditions it was charging at 0.2A. With the sun shinning it was 0.5A.

However, the engine only just cranked over so I'll probably have to hook the charger up soon. I can't see the solar panel restoring it to full capacity.
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2004 V70 2.4 D5 (163bhp) P2 manual 150k