Battery powered trickle charger?

[Mr Al]

Slightly odd situation; my drive is outside next door's house so I could run a mains cable but would be a PITA. I already have an Optimate but would buy a C Tek mxs 5 if there was power.

Been looking at battery boosters and concluded that what would work best is a battery boost - jump start pack that could trickle charge through the cigarette lighter. I could then leave the car on a trickle, and remove the pack to charge from the mains (in my hallway) when out driving.

Obv I could wire in an O ring connector to the battery itself but the cigarette lighter option would remind me to disconnect.

To be clear I'm asking about trickle or conditioning not full on charging.

Any recommendations?

Cheers

Al

[pete.g]

If you do this you will have two batteries in series and the stronger charge will slowly discharge into the weaker one, performing the function you require.

However, this will also happen once the situation reverses, so your car battery will top up the starter pack battery once it becomes the stronger.

So, if left for a lengthy period you will end up with two batteries of equal weakness, neither of which is able to start your car.

Your best option is probably a decent solar trickle charger, as the car is outside it will get enough light to keep the battery topped up. You can always get a starter pack as well, for use if it does fail.

ETA - if the battery is still going flat connected to the Optimate, then you either need a new battery or a new solar charger.

Edited by pete.g on Thursday 12th January 11:28

[Mr Al]

Thanks Pete, that's really helpful.

I had considered a solar charger as an option, especially as there's a streetlight outside so I could angle this (below) towards the light. More 'minimise discharge' than retain charge but it must help? Do these things work?

https://www.amazon.co.uk/gp/product/B00AC1LLQY/ref...

[jkh112]

I have a "briefcase" solar charger with rectifier bought from ebuyer a few years ago. It sits in the rear shelf area of my 996 and keeps the battery topped up indefinitely in the Summer and significantly improves the battery life during the Winter.

edit: Can't find it on Ebuyer, but it is made by Xenta and is 13W.

Edited by jkh112 on Thursday 12th January 12:32

[Mr Al]

Great, thank you JKH, got to be worth a try. Amazon here I come...

[Mr Al]

Back to you Pete, another option would be a second battery - which would perform as you describe but hooked up with a diode to prevent reverse drain?

Put the temporary second battery in the boot and take out before driving. Charge in the house as before.

[996TT02]

Mr Al said:

Back to you Pete, another option would be a second battery - which would perform as you describe but hooked up with a diode to prevent reverse drain?

Put the temporary second battery in the boot and take out before driving. Charge in the house as before.

There is no such issue with "reverse drain" - at least if the backup battery is properly charged.

All you will do if you hooked up another battery is effectively have two batteries, with double the Ah capacity, which will take longer to drain than a single one.

Current can't be "forced" if that's what you may be imagining - you can't have one battery fully draining "into" another one (of same voltage). Current flows until voltage is equalised.

The only way I could see this working alternatively (but with complications) would be to step up the voltage of the backup battery - in effect unless some direct device exists I could see an inverter upping the voltage to 240AC then a battery charger providing 14 or whatever to your car's battery. "Complications" because an ordinary inverter and battery charger's inefficiencies would drain the backup battery far faster than your car's battery by its electronic devices. So OK only in theory, again unless a really low-loss device already exists.

Go solar, or disconnect the battery, but the latter only if garaged.

[pete.g]

996TT02 said:

Mr Al said:

Back to you Pete, another option would be a second battery - which would perform as you describe but hooked up with a diode to prevent reverse drain?

Put the temporary second battery in the boot and take out before driving. Charge in the house as before.

There is no such issue with "reverse drain" - at least if the backup battery is properly charged.

All you will do if you hooked up another battery is effectively have two batteries, with double the Ah capacity, which will take longer to drain than a single one.

Current can't be "forced" if that's what you may be imagining - you can't have one battery fully draining "into" another one (of same voltage). Current flows until voltage is equalised.

The only way I could see this working alternatively (but with complications) would be to step up the voltage of the backup battery - in effect unless some direct device exists I could see an inverter upping the voltage to 240AC then a battery charger providing 14 or whatever to your car's battery. "Complications" because an ordinary inverter and battery charger's inefficiencies would drain the backup battery far faster than your car's battery by its electronic devices. So OK only in theory, again unless a really low-loss device already exists.

Go solar, or disconnect the battery, but the latter only if garaged.

I would concur with all of this. We use multi battery setups in boats and also in a couple of the 4x4s I have run. I have always used a split charge relay on the 4X4s and a simpler manual switch on boats. I don't think either application is the answer to your question - solar is the way forward.

[Mr Al]

JKH's charger looks good, much more powerful than the AA one I linked to. Anybody have specific recommendations? The Ravpower one on Amazon seems OK but has USB output - need to work out if that will charge with my iPhone USB cigarette lighter charger i.e. the opposite way as intended.

Apologies all for my schoolboy electrics 😳 which is of course why I' m asking...

[paralla]

http://www.tandsarchitectural.co.uk/caravan-motorh...

[ATM]

paralla said:

http://www.tandsarchitectural.co.uk/caravan-motorh...

Does that plug in the CAN port?

[paralla]

OBD2 port which you might be thinking of as the CAN port.

[ATM]

paralla said:

OBD2 port which you might be thinking of as the CAN port.

Do these stay on / connected when you turn car off?

[edc]

ATM said:

paralla said:

OBD2 port which you might be thinking of as the CAN port.

Do these stay on / connected when you turn car off?

My fault code reader will only read when the ignition is on so I presume there is only power to the OBD2 port when the ignition is on.

[ATM]

edc said:

ATM said:

paralla said:

OBD2 port which you might be thinking of as the CAN port.

Do these stay on / connected when you turn car off?

My fault code reader will only read when the ignition is on so I presume there is only power to the OBD2 port when the ignition is on.

Exactly - I've always thought this but now newer cars are getting stolen via obd reprogramming - where obviously the ignition is off because they dont have a key. So maybe newer cars do this and older do not?

[paralla]

Pin 16 is battery (rather than ignition) on all OBD-II protocols