12v battery maintenance

[Roker]

On 12/22/2021 at 4:53 PM, Trewithy said:

I use a CTEK to maintain my battery but I don't disconnect the battery.  I just connect the red cable to the + terminal on the battery and the black cable to a lug on the cylinder head.  Do not put it directly on the battery - terminal.  

Why can we not connect direct to the Battery the negative is the same potential as the lug

[Roker]

I was thinking of buying a very small Jump starter and charging it via the power connection in the boot 

The advantage is, if you leave the car for any length of time there is no parasitic current from this as there is from the 12v Battery and it should remain charged in case of an emergency,  it will also keep charged up from the boot power socket while driving avoiding it going flat and getting ruined

[Trewithy]

2 hours ago, Roker said:

Why can we not connect direct to the battery the negative is the same potential as the lug

If you connect the Battery charger directly to the Battery terminals you are by-passing the Battery management system and the ECU may not recognise that the battery has been charged.

[Roker]

6 minutes ago, Trewithy said:

If you connect the battery charger directly to the battery terminals you are by-passing the battery management system and the ECU may not recognise that the battery has been charged.

I don't think the Battery management goes via a earth ground on the chassis, the chassis is the same potential as the Battery negative because they are linked

[Roy124]

3 hours ago, Roker said:

I was thinking of buying a very small Jump starter and charging it via the power connection in the boot 

The advantage is, if you leave the car for any length of time there is no parasitic current from this as there is from the 12v battery and it should remain charged in case of an emergency,  it will also keep charged up from the boot power socket while driving avoiding it going flat and getting ruined

My 5000mA Battery remains at over 75% for months.

[Derek.w]

4 hours ago, Roker said:

Why can we not connect direct to the battery the negative is the same potential as the lug

I have 3 leads sets comming directly off the Battery via a 5 amp in line fuse one set is solar charging the second is CTEK charger and the 3rd is Battery Monitor (BM).

[Dala]

1 hour ago, Trewithy said:

If you connect the battery charger directly to the battery terminals you are by-passing the battery management system and the ECU may not recognise that the battery has been charged.

Do you have any proof?

[Cyker]

41 minutes ago, Roy124 said:

My 5000mA battery remains at over 75% for months.

Be careful with that if you're just going by the LEDs - I've seen many cases where, e.g. My friend's one was showing 70-80%, but when he went to use it, it immediately sagged to 20%!

The percentage is guesstimated by voltage, and batteries can show a deceptively high voltage if they are only very lightly loaded (e.g. the draw of an LED)

It's worth charging e.g. your phone or a tablet off it now and then, to put a real load on it to make it show a more correct % remaining. This is why some batteries can appear to charge themselves, e.g. after a heavy load is put on them, then they recover, and the % remaining magically goes up!

[Roy124]

Cyker. Did as you suggested.  Started with 4 led, ie 75% plus.  After charging phone it indicated 3 led.  Connected to a charger,  3rd led started to blink.  Cup of coffee later 3rd steady, 4th blinking.

I guess a good SOC near 70% after a long time untouched. 

[Roker]

Can someone please explain why some jump starters are only supplied with a USB cable to charge, as the USB is only 5v how does it charge a 12v booster Battery

[Mooly]

Changing a DC voltage to different value of DC (which can be higher or lower) is common place using a DC/DC convertor. This technology is 'everywhere' in all kinds of consumer electronics.

https://en.wikipedia.org/wiki/DC-to-DC_converter

Conversion done this way is very efficient and can be as high 95% however you never get something for nothing. If you take a 5 volt USB 2 output which might support a maximum of say 0.5 amp then we could never get more than 0.16 amps at 15 volts available to charge a Battery pack using a DC/DC convertor.

 

 

 

[Roker]

8 hours ago, Mooly said:

Changing a DC voltage to different value of DC (which can be higher or lower) is common place using a DC/DC convertor. This technology is 'everywhere' in all kinds of consumer electronics.

https://en.wikipedia.org/wiki/DC-to-DC_converter

Conversion done this way is very efficient and can be as high 95% however you never get something for nothing. If you take a 5 volt USB 2 output which might support a maximum of say 0.5 amp then we could never get more than 0.16 amps at 15 volts available to charge a battery pack using a DC/DC convertor.

 

 

 

So where do we get the converter from if it is not supplied by the booster as seems to be the case

[Roy124]

7 minutes ago, Roker said:

So where do we get the converter from if it is not supplied by the booster as seems to be the case

My booster has USB input and 5v/12v output.  The 12v output is a guarded socket.  

I also have UPS systems in the house.  One has a 240v input and 5v and 12v output.  Without checking,it may also have a USB output.

[Mooly]

16 minutes ago, Roker said:

So where do we get the converter from if it is not supplied by the booster as seems to be the case

It must be internal within the pack. Convertors can be made really small, postage stamp size.

[Roy124]

I had a thought about people who think the jumper packs should not be necessary or that Toyota should provide them.

How many old hands used to carry, or still carry, jumper cables?  Jumper cables were one of those things that were carried routinely. 

It was not unusual to hear someone to call "anyone got jump leads?" Or can someone give me a push?

[Mooly]

11 hours ago, Roker said:

Can someone please explain why some jump starters are only supplied with a USB cable to charge, as the USB is only 5v how does it charge a 12v booster battery

Just to go back to your original question. Are you sure you mean the pack can be charged via USB (which is possible as I have outlined) or are you confusing 'USB charging' with the packs ability to charge a USB device like a phone or tablet?

The reason for asking is that given the limited current available from USB it is going to take a long time to charge a reasonable capacity pack. Using the figures I gave as an example it would take 2 to 3 days to charge an 8000mAh pack for example given real world losses.  

 

[Rhymes with Paris]

24 minutes ago, Roy124 said:

I had a thought about people who think the jumper packs should not be necessary or that Toyota should provide them.

How many old hands used to carry, or still carry, jumper cables?  Jumper cables were one of those things that were carried routinely. 

It was not unusual to hear someone to call "anyone got jump leads?" Or can someone give me a push?

Yes, still have heavy duty ones in the boot at all times.

Cheap thin ones just smoke and fizzle.

Hope I don't need them, but the old saying is better to have them and not need them,than need them and not have them.

[Roker]

48 minutes ago, Mooly said:

Just to go back to your original question. Are you sure you mean the pack can be charged via USB (which is possible as I have outlined) or are you confusing 'USB charging' with the packs ability to charge a USB device like a phone or tablet?

The reason for asking is that given the limited current available from USB it is going to take a long time to charge a reasonable capacity pack. Using the figures I gave as an example it would take 2 to 3 days to charge an 8000mAh pack for example given real world losses.  

 

That's exactly the point,  most jump starter packs are not supplied with 12v power plug,  so how can the power pack be charge via USB connector 

[Roy124]

1 hour ago, Mooly said:

Just to go back to your original question. Are you sure you mean the pack can be charged via USB (which is possible as I have outlined) or are you confusing 'USB charging' with the packs ability to charge a USB device like a phone or tablet?

The reason for asking is that given the limited current available from USB it is going to take a long time to charge a reasonable capacity pack. Using the figures I gave as an example it would take 2 to 3 days to charge an 8000mAh pack for example given real world losses.  

 

My pack is 4,000 or 5 000.  It is charged from USB but also has a USB output.   I just recharged it.  The SOC led indicated less than 75%.  In less than an hour it was over 75% and not that long before all led were steady ie 100% or thereabouts.

I had used it once start the car.  That took it below 75% I think. It was some time ago.

Edit:

I charged it on receipt although it had a significant charge.  I recharged it after I had recharged my SiL's phone and again after starting my Corolla.   I got my Yaris Cross over a year ago.  I just topped up the Battery as outlined.   I have not had it on charge for any particular length of time in 3 years.

[Mooly]

9 hours ago, Roker said:

That's exactly the point,  most jump starter packs are not supplied with 12v power plug,  so how can the power pack be charge via USB connector 

The simple answer is that it has been designed with that functionality as part of its design brief if it has that feature.

Any pack can be charged from 5 volts if it has the required DC/DC convertor on board. You can easily generate 500 or 5000 volts DC from 5 volts DC.

9 hours ago, Roy124 said:

My pack is 4,000 or 5 000.  It is charged from USB but also has a USB output.   I just recharged it.  The SOC led indicated less than 75%.  In less than an hour it was over 75% and not that long before all led were steady ie 100% or thereabouts.

Never loose sight of the basic theory with the numbers. A 5000mAh pack that is discharged needs at least that much (and more in practice) putting back in. 5 volts at 1 amp (5 watts) can only deliver 15 volts (for charging say) at a current of 1/3 (0.333 amp).

You step the voltage up by a factor of three so the current available goes down by the same amount. 0.333A * 15v is 1 watt. In practice a bit less because of inefficiencies and losses. Using those numbers as an example means a 5000mAh Battery needs at least 15 hours to go from discharged to full.

If any Battery (of any type or technology) seems to recharge very quickly then it may be that it is down on capacity in the way an old laptop Battery can appear to go from say 20% to 100% in 15 minutes. Yes it is 100% charged but that is now based on its reduced and aged capacity.  

[Roker]

A DC to DC converter is a very complex way of getting 12 volt, it's  more likely  USB-C socket which I think can supply 12v

[Cyker]

The standard USB voltage is still 5v, even with USB-C; There is an add-on standard called USB-PD which allows up to 48v, but that requires additional components and licences to be implemented; You mostly see it on newer high-end laptop and phone chargers.

DC-DC conversion is pretty mature at this point so it's not a big stretch to implement it; PC motherboards used to take in a variety of voltages from the power supply, but now they mainly use 12v and use on-board DC-DC to get whatever other voltages they need!

[Roker]

A DC to DC converter is a very complex way of getting 12 volt, it's  more likely  USB-C socket which I think can supply 12v.

To convert DC the current has to be chopped,  put through a transformer and rectified and smoothed back to DC.

So it doesn't answer the question why most power packs do not supply a 12v power socket and only a USB lead

[Cyker]

Oh I thought you were asking why power packs were charged with 5v and not 12v, although now that I think about it many of them are charged via a higher voltage via a barrel plug.

[Mr Billiards]

The Corolla GR Sport I have on order will be my first hybrid Toyota.  Having previously always run Honda's or Mazda's.

I'm aware if the car is not used a great deal in order to keep the 12v Battery healthy I can set the car in the ready condition in Park and the handbrake on for around 60 minutes to allow the car to charge the 12v Battery. I will most likely do this while I carry out the weekly wash and vacuum inside. 

 

Apologies if this seems a stupid question.

My question is......with the car in the ready condition for 60 minutes or so does the key fob need to be left in the car?