I do quite a lot of short (<10 minute) trips in my 380. While the car is still starting okay, the voltage is dropping enough for my PowerMagic to shut off power to my dashcam after a few minutes of the engine being off (It's set to trigger at either 11.8 or 11.6 volts, can't recall which)
I have a 6-amp battery charger and wouldn't mind periodically giving my battery a decent charge to get it back up to max capacity,. however I'd like to do this in the most convenient way possible, preferably without having to remove it from the car or disconnect it, as it's a pain to reprogram my stereo etc.
So obviously the easiest and cheapest way to do this would be to just hook the charger up to the battery while it's still connected to the car and turn it on... but will this cause any damage to the car? Some of the stuff I have read online seems to say that if it's a slow charge (less than 7 amps) that it should be ok, but I would like the opinions of people that have maybe done it already themselves?
If it's not gonna be safe, then I will most likely buy a battery isolator terminal from eBay/Supercheap and use that, and make a memory saver from a 12V gel-cell battery and cigarette lighter plug.
Cheers.

Do some research on trickle chargers that can be mounted under the bonnet and left in there permanently.

Something like this:
http://www.amazon.ca/Schumacher-SE-1-12S-CA-Automatic-Onboard-Battery/dp/B0000AXTUY

That one is only 1.5A, you may want something with a few more amps, but hunt around - they do exist.

You still need a 240V extension lead and remember to hook it up, and disconnect when you drive off, so still some effort involved.

I always disconnect one battery terminal when I put a battery on charge while the battery is still in the car, and you are right, getting the car to behave - clock, radio, idle control - afterwards is a pain.

(The theory about disconnecting one lead is that a battery charger will not have a smooth DC output, and there is a possibility of spiking - destroying - a diode in the alternator. Don't know if this is still a precaution worth following with a good charger though.)

Do some research on trickle chargers that can be mounted under the bonnet and left in there permanently.

Something like this:
http://www.amazon.ca/Schumacher-SE-1-12S-CA-Automatic-Onboard-Battery/dp/B0000AXTUY

You still need a 240V extension lead and remember to hook it up, and disconnect when you drive off, so still some effort involved.

I always disconnect one battery terminal when I put a battery on charge while the battery is still in the car, and you are right, getting the car to behave - clock, radio, idle control - afterwards is a pain.

Hmmm interesting, probably outside what I'm prepared to spend at this stage. I can get an isolator terminal and cigarette plug with 45cm lead for about $13 from Jaycar - I have all the other bits I will need already so I reckon I am just going to make a battery that I can plug in to the lighter socket in the console to keep the memory while I charge the main battery.

Hmmm interesting, probably outside what I'm prepared to spend at this stage. I can get an isolator terminal and cigarette plug with 45cm lead for about $13 from Jaycar - I have all the other bits I will need already so I reckon I am just going to make a battery that I can plug in to the lighter socket in the console to keep the memory while I charge the main battery.

Let us know if this works.
What battery would you use? Would you need to leave the key in and on ACC to make it work?
I have a spare battery on trickle charge permanently, would be nice to be able to swap batteries in the car without loosing settings.

Let us know if this works.
I have a spare battery on trickle charge permanently, would be nice to be able to swap batteries in the car without loosing settings.

I see no reason that it shouldn't work, as long as there's something supplying 12 volts in the "always on" circuit then it should be fine. I just need to make sure I use the console lighter socket and not the main one :)

Apparently constantly trickle charging lead-acid batteries doesn't do them any good, as it leads to build up of sulphation on the plates. You can get Cadmium Suplhate solution to get around this (like Inox MX-2 Battery Conditioner), but ideally you want to avoid it.

DO NOT buy that charger listed on Amazon, it is 120 V input.

This is probably the best value for money, all 'round battery charger:
http://www.supercheapauto.com.au/online-store/products/Projecta-Pro-Charge-Battery-Charger-12-Volt-2-8-Amp.aspx?pid=292792#Recommendations

It has a Calcium mode for batteries with calcium technology (all modern decent batteries), and a de-sulphation mode. It can also be permanently attached to the battery as outlined in the instructions. The permanent attachment is more ideally suited for batteries on camper trailers etc. The charger is also dust and water proof (as long as the terminals and plugs aren't exposed to the elements).

That charger is on special at Supercheap Auto until 08/03/2015, at which point it will go back to it's normal price of $155, from $110 currently on special.

Apparently constantly trickle charging lead-acid batteries doesn't do them any good, as it leads to build up of sulphation on the plates.

Other way around, a battery left off a vehicle at a low state of charge will sulphate up.
As for the battery charger on Amazon - I was looking for "proof of concept", ie is there such a thing as a charger that can be permanently connected to a car battery and mounted inside the engine bay, so that all you need to do is open the bonnet and plug an extension lead in?

Answer: yes there is! Obviously voltage input and amperage output are important considerations.

Anyhow, moot point as the OP wants to do it differently.

EDIT: $110 for a 8A charger isn't cheap. I have a 20A, automatic 3 stage charger, didn't pay anywhere near that!

I've completed the project - I now have a 12-volt "Memory saver" which plugs in to the console cig socket and an isolator on the negative battery terminal.
This is the charger I have, by the way:
http://www.supercheapauto.com.au/online-store/products/Calibre-Power-Pack-Battery-Charger-3-Stage-12-Volt-6-Amp.aspx?pid=305595#Recommendations
You can see a lead next to the AC plug that has 2 pins - the lead with the alligator clamps connects straight to this, but the charger also came with a lead that had ring terminals on the other end, so I have "hard-wired" this lead to the battery (straight to the +'ve, and to the battery side of the -'ve) so I can connect the charger without having to use the alligator clamps :)
I hope that's descriptive enough, I can provide pics if needed or if anyone is interested.

Apparently constantly trickle charging lead-acid batteries doesn't do them any good, as it leads to build up of sulphation on the plates. You can get Cadmium Suplhate solution to get around this (like Inox MX-2 Battery Conditioner), but ideally you want to avoid it.



Continous trickle charging actually avoids sulphation of the plates.
But its still not good practise as it may cause increased "grid corrosion" on the positive plates.
If the plates have antimony in them you also accelerate antimony poisoning of the negative plates!
Over time you push out lead oxide paste and thereby loose paste to grid integrity.
Also the grid gets thinner (so your battery fails prematurely).
You could just charge for a day every 3 or 4 weeks if the battery is not being used.
Just use a normal battery charger, as that will drop to a trickle charge when the SG is high enough (battery nearing 80% capacity!).

Battery saver chargers might help if current limited to match the battery self discharge characteristics.
But who knows what that will be?

Hooking up the charger to the cigarette lighter (if there is one) with keys in accessory is fine.
I do it all the time to keep the batteries viable on cars I am not using.
If the SG is low, then charge for a week using a normal battery charger, in car or out it doesn't matter.

Normal starting of a car does not take a lot of capacity out of the battery, so even short trips will replace that lost capacity.
If the battery is loosing capacity in that scenario then its cactus or something is parasitically draining the battery.

Other way around, a battery left off a vehicle at a low state of charge will sulphate up.
As for the battery charger on Amazon - I was looking for "proof of concept", ie is there such a thing as a charger that can be permanently connected to a car battery and mounted inside the engine bay, so that all you need to do is open the bonnet and plug an extension lead in?

Answer: yes there is! Obviously voltage input and amperage output are important considerations.

Anyhow, moot point as the OP wants to do it differently.

EDIT: $110 for a 8A charger isn't cheap. I have a 20A, automatic 3 stage charger, didn't pay anywhere near that!

The $110 is because Projecta is a decent brand, and because of its features like the rejuvenation mode, Calcium mode etc. The rejuvenation mode is where it pulses at something like 1 MHz for 24 hours, and Calcium mode is where it charges at 16 V for a couple of hours to reduce stratification in the cells. The calcium mode also acts as a seventh stage for Calcium batteries and standard batteries. On top of this, it's designed to be connected permanently as an option.

http://projecta.com.au/site/DefaultSite/filesystem/documents/Battery%20Chargers/PC400-2100_instructions_Issue1.pdf

I did Google it, it is available a bit cheaper elsewhere but you have to pay for postage.

The other thing I like about it is that it is an Australian based company, and is Australian made as well? Most of their products are supposedly made in a factory in Victoria.


Continous trickle charging actually avoids sulphation of the plates.
But its still not good practise as it may cause increased "grid corrosion" on the positive plates.
If the plates have antimony in them you also accelerate antimony poisoning of the negative plates!
Over time you push out lead oxide paste and thereby loose paste to grid integrity.
Also the grid gets thinner (so your battery fails prematurely).
You could just charge for a day every 3 or 4 weeks if the battery is not being used.
Just use a normal battery charger, as that will drop to a trickle charge when the SG is high enough (battery nearing 80% capacity!).

Battery saver chargers might help if current limited to match the battery self discharge characteristics.
But who knows what that will be?

Hooking up the charger to the cigarette lighter (if there is one) with keys in accessory is fine.
I do it all the time to keep the batteries viable on cars I am not using.
If the SG is low, then charge for a week using a normal battery charger, in car or out it doesn't matter.

Normal starting of a car does not take a lot of capacity out of the battery, so even short trips will replace that lost capacity.
If the battery is loosing capacity in that scenario then its cactus or something is parasitically draining the battery.

I was probably thinking along the lines of that :). I was also thinking of directly charging batteries from solar panels, apparently that doesn't do the battery any good over time, but although it is trickle charging it wouldn't be the same as a proper permanent connection.

Continous trickle charging actually avoids sulphation of the plates.
But its still not good practise as it may cause increased "grid corrosion" on the positive plates.

Normal starting of a car does not take a lot of capacity out of the battery, so even short trips will replace that lost capacity.
If the battery is loosing capacity in that scenario then its cactus or something is parasitically draining the battery.

Grid and plate corrosion (erosion?) is what kills a battery in normal use, but it takes years. 3 years with a cheap battery, 6 years or more for a better designed battery.
If you take a dead battery, drain the acid, and wash it out with a hose, you would be surprised how much crap comes out of a battery.
Don't forget the battery is being charged continuously while driving, so a gentle nudge from a battery charger overnight won't speed up the process much.

Starting takes an initial current drain from the battery in excess of 300 amps, and drops rapidly as the starter gathers speed.
If the battery can't supply that initial current, the engine may not even turn over.
It does take a bit of driving to top the battery up again, but a healthy battery will cope.

Life of a battery is also temperature dependent, boot mounted batteries seem to last longer than ones mounted in the engine bay. bobistheoilguy.com tells me cold weather batteries in the US don't last anywhere as long as warmer climate cars.

Positive grid corrosion occurs whenever a battery accepts a current when its nearing full capacity and cannot use that current for reversing lead sulphate into lead oxide.
And so an overcharge reaction occurs that attacks/eats the lead /antimony grid of the positve plate.
The released antimony ions migrate to and plate the negative grid and causes a catalytic reaction that increases the self discharge (can reach 30% or more per month).

On top of increased self discharge, eventually loss of grid density and other failure mechanisms increases the internal resistance of the battery.
Initially seen as a reduction in AH capacity as well as Cold Cranking Capacity.
Continuous trickle charging will shorten the life of a battery, better to just do a minimalist charging duty cycle.
(maybe that is what these battery saver chargers do - I don't know - but someone said its was a continuous trickle charge!).
No problem with hooking up the battery the a charger and letting it sit on charge for up to a week to fully charge the thing.
Just don't keep it connected and if not used ust duty cycle it to replace that lost by self discharge.

The crap that falls out of the battery is crystalline lead sulphate and if you get lots then you have bulging plates and little grid to paste integrity.
Its stuffed even if you get a fair amount AH capacity out of it after the flush.

The cadmium solution made by Inox reacts with crystaline lead sulphate making some of it reversible.
I wouldn't tough that stuff in a million years as cadmium is extremely toxic and doesn't really restore the battery (causes catalytic self discharge reactions I think!).

Heat is also an enemy of batteries but its true that they give more CCC when warmer. Hence the appearance of earlier demise in cold climates (reduced CCC to start with!).

Anyway, the ubiquitous battery is a forgotten but very interesting car component.
I get 5 to 7 years out of GNB batteries.
If you want a good car battery - go for Century Yuasa lead calcium flooded electrolyte batteries.

Buy one of these, $10 well spent.
http://www.jaycar.com.au/productView.asp?ID=PP2140

Or one of these if you dont have a handy 12v cigarette plug power source available. (shop around, you can get them or build them real cheap)
http://www.ebay.com.au/itm/Car-Computer-Clock-Stereo-Memory-Saver-Battery-Backup-Unit-Automotive-12-volt-/400857015444?pt=LH_DefaultDomain_15&hash=item5d54f0a494

You can also get a small solar panel trickle charger, mount it on your rear parcel shelf, If you car spends long periods in the sun.
Otherwise, like others have said, a mains powered trickle charger and just connect it straight to the battery.
I have never disconnected the battery while charging, trickle or full power charge and i have never had any sort of negative outcome.
(10yrs as a mechanic)

Last charger I bought was Projecta 4300... gutfeel suggested not to touch the Calibre brand, it's just me.

http://www.supercheapauto.com.au/online-store/products/Projecta-Battery-Charger-12-Volt-4300mA.aspx?pid=292787&menuFrom=40703#Recommendations

these days with smart chargers its no longer necessary to disconnect the battery from the car to charge. (In the old days dumb chargers would pump 16-18V and blow the v-reg in your alternator)

I run a wire from battery to rear edge of bonnet; DC plugs mating to a cable glued to garage wall that eventually runs to the charger. For short trips I can disconnect and leave the wire inside the wipers channel, remove for long trips. Fuses inline on both wires at both ends just 'cos I'm anal.

http://www.supercheapauto.com.au/online-store/products/Projecta-Battery-Charger-12-Volt-4300mA.aspx?pid=292787&menuFrom=40703#Recommendations


?...the voltage is dropping enough for my PowerMagic

Blackvue junkie? ;)

Be aware that this gizmo can draw 1-2A continuously... thats like 12-15Ah overnight, 20Ah/day. When it's a daily driver started everyday that drain might be ok on a healthy battery. But if its sitting over a weekend or longer... it's not good for battery at all.

Typical battery is good for about 80Ah but with leadacids not designed for deep cycle I try not to drain them more than 30-40% ever! (That's barely 48hrs Blackvue parked) Any more drainage it really kills their lifespan, you might need a new battery every year. It might pay to get a deepcycle boat/RV battery or Optima, but neither comes cheap.

I have 550s but haven't yet hooked up rear cam nor leave wifi on.

And it does take a while for car alternator to recharge battery especially if you have Blackvue sucking out 12Ah every night. Alternator doesn't charge much whilst idling, you'd need to rev it to 2000rpm for something like 20mins nonstop to pump 12Ah back into the battery.

Everyday! :/

That means your Blackvue device is presenting a considerable standing load.
The normal car battery is not designed to cope with a standing load like that.
You are absolutely correct that car batteries are not designed for anything other than shallow cycling.

I think this scenario is a whole other issue than the one off "keeping batteries healthy while the car is parked for long periods".
That is - the only drain is parasitic and self discharge (no active loads - "maybe the security alarm"!.

But thanks for the warning to stay away from that camera.

Not convinced that 18 volts from a dumb charger would kill the alternator voltage regulater.
There is only reverse bias on the regulator and so virtually no power dissipation (but I could be wrong - not being a car electrician!).

Be aware that this gizmo can draw 1-2A continuously... thats like 12-15Ah overnight, 20Ah/day. When it's a daily driver started everyday that drain might be ok on a healthy battery. But if its sitting over a weekend or longer... it's not good for battery at all.

Of course I am aware, that's why I have a PowerMagic in the circuit in the first place.

But thanks for the warning to stay away from that camera.

nah nothing against Blackvue, I think all other dash cams have same issue if wired to be on always. HD video cams pump a heap of data bits and they do need power; other issue is heat - all that energy becomes heat.

Blackvue was the best available last Easter time when I bought in, there's some newer models out now but I don't think they're significantly improved to be worth upgrading. Other brands still look like cheap naff.



Not convinced that 18 volts from a dumb charger would kill the alternator voltage regulater.
There is only reverse bias on the regulator and so virtually no power dissipation (but I could be wrong - not being a car electrician!).

meh I'm not a car sparky, just been charging leadacids going on 4 decades hahaha

Some of the old dumbchargers do current control only inverse to the voltage; on open circuit there's anywhere 18-22V across the terminals when I measured. They'll keep pumping until the electrolyte is fizzing like Perrier.

The new smart chargers don't even powerup the leads until after its detected voltage from a connected battery. Instructions say its safe not to disconnect from car, I'm happy to obey. :)

Of course I am aware, that's why I have a PowerMagic in the circuit in the first place.

PowerMagic is really bad for battery if you flatten it (= <12V) repeatedly, I never bothered installing it in for that very reason. My KJ is parked far away and might only get run once a week in recent times.

What we really need is a system like the Prius' which is smart enough to start the engine and charge the battery automatically when voltage is too low. Prius also has solar cells in the sunroof to run roof vent fans.

You can also get a small solar panel trickle charger, mount it on your rear parcel shelf, If you car spends long periods in the sun.

Got 1, they're pretty much next to useless :) mines size of a small skateboard.

Outside in noon sun I measured less than 100mA current; much less when when under glass window. I set mine up outside on the roof of the garage... gotta be cleaned everyweek or the dust accumulated cuts generation too.

Plus most cars don't have their ciggy lighter live when key is off, so I don't know how those things can charge the battery when you're not there with key in ignition on. :)

I think this scenario is a whole other issue than the one off "keeping batteries healthy while the car is parked for long periods".
That is - the only drain is parasitic and self discharge (no active loads - "maybe the security alarm"!.


We have cars that are parked for weeks/months/years. I like to keep petrol tanks full & tyres pumped hard.

Easy solution for battery... ideally you remove it :D and keep a small Optima or similar on hand that's kept on a "battery tender" maintenance device. Only replace battery when you want to run it.

For cars run occasionaly, i install battery isolators... often on both terminals haha. If there's a PowerPoint nearby, install one of these on side of battery in the car.

http://www.supercheapauto.com.au/online-store/products/Projecta-Battery-Charger-12-Volt-1600mA.aspx?pid=292785&menuFrom=40703#Recommendations

Every 3-5yrs battery will still get tired & need replacing.

Or look at modern alternatives... race cars often use tiny little lipo batteries these days, smaller than a housebrick and half the weight.

@ Magnette
Agreed - removing the battery is the easy solution.
And just the occasional refresher charge with a normal battery charger is going to properly maintain the battery.
I mention that again only so that people that have a normal battery charger don't still feel compelled to purchase a "smart" charger.

Re the battery charger open circuit voltage - batteries a pretty "stiff" power source - meaning the battery charger OC voltage will not be seen by the alternator VR.
(but if there is a fault that isolated the battery, but not the alternator from the charger, then yes that OC will be across the VR)

So it turns out my memory-saver device wasn't actually 100% successful.
While my stereo memory and the clock in the MFD were retained, the trip computer was reset back to zero and the speed alert reset back to 50kph. This was with the main battery isolated for about 8 hours.
However it's possible that the backup battery I was using may have had a low charge too.

So it turns out my memory-saver device wasn't actually 100% successful.

What was your setup again?

I've done croc clips to the battery terminals before, powered by an 8pk of AAs :) works for the short time it took to swap a new battery over.

Just make sure you've got no cabin lights on or use any powerlocking whilst it's on life support. Them newer blinger models have silly cabin lights that don't even have an Off switch...

Ummmmm would it not just be simple to go for, ummm, I dont know, a drive.........

Plus if you are doing 5 to 10 minute trips that is more than enough to charge from a start up, I would say your battery is more the issue than the short trip

What was your setup again?

I've done croc clips to the battery terminals before, powered by an 8pk of AAs :) works for the short time it took to swap a new battery over.

Just make sure you've got no cabin lights on or use any powerlocking whilst it's on life support. Them newer blinger models have silly cabin lights that don't even have an Off switch...

A 12-volt motorbike battery plugging in to the lighter socket in the centre console for about 8 hours while the main battery was isolated. But like I said in post #22 the bike battery may have been partially discharged already.