Clubjazz - Honda Jazz & HR-V Forums

Honda Jazz, HR-V & Hybrid Forums => Hybrid => Topic started by: Bonobo on November 23, 2021, 09:41:16 PM

Title: Any way to charge an empty starter battery from the one in the boot?
Post by: Bonobo on November 23, 2021, 09:41:16 PM
Imagine you are in the middle of a desert, and your hybrid jazz 2012 has an empty starter battery. But you have thick and long enough wires, a knife, spanners, screwdrivers and reasonable electric skills. Is there any way to charge an empty starter battery from the one in the boot?
Title: Re: Any way to charge an empty starter battery from the one in the boot?
Post by: Neil Ives on November 23, 2021, 09:45:56 PM
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Title: Re: Any way to charge an empty starter battery from the one in the boot?
Post by: Neil Ives on November 24, 2021, 03:28:02 PM
The drive battery holds a high voltage, something like 180volts.
In theory, to be able to charge the baby 12v battery from the drive battery you would need to produce alternating current from the HV battery using a DC to AC device, pass the AC through a transformer to reduce the voltage then rectify the lower voltage AC to DC at 12v. Then you'd need to regulate the current drawn by the baby battery.
I suggest calling out the AA!
Title: Re: Any way to charge an empty starter battery from the one in the boot?
Post by: culzean on November 24, 2021, 03:52:23 PM
Imagine you are in the middle of a desert, and your hybrid jazz 2012 has an empty starter battery. But you have thick and long enough wires, a knife, spanners, screwdrivers and reasonable electric skills. Is there any way to charge an empty starter battery from the one in the boot?

Yeah, but before you try make sure you have long cables,  long enough to place the 12v battery behind a wall, preferably the opposite side of the wall to the side where you will be.  Attach cables to 12volt battery and then to the battery in the boot, you should hear a loud bang, and if the 12volt battery is still in one piece it may start the engine.. The batteries for EV motor power in a car will always be in the 200 to 800 volt range.... Good Luck
Title: Re: Any way to charge an empty starter battery from the one in the boot?
Post by: csp on November 24, 2021, 04:00:15 PM
Don't even think about trying to charge the 12V battery from the high voltage battery. This would be very dangerous & likely to cause injury & damage the car!
Title: Re: Any way to charge an empty starter battery from the one in the boot?
Post by: nowster on November 24, 2021, 10:30:54 PM
The drive battery holds a high voltage, something like 180volts.
In theory, to be able to charge the baby 12v battery from the drive battery you would need to produce alternating current from the HV battery using a DC to AC device, pass the AC through a transformer to reduce the voltage then rectify the lower voltage AC to DC at 12v. Then you'd need to regulate the current drawn by the baby battery.
I suggest calling out the AA!
Or a buck regulator.

https://en.wikipedia.org/wiki/Buck_converter
Title: Re: Any way to charge an empty starter battery from the one in the boot?
Post by: Jocko on November 24, 2021, 11:05:17 PM
You could use a chain of resistors and tap off your 14 - 15v that way.
Title: Re: Any way to charge an empty starter battery from the one in the boot?
Post by: culzean on November 25, 2021, 08:00:30 AM
One of those occasions you need one of those jump start packs,  or a tow from a herd of camels... 8)  May be a good thing in the desert to carry a fold-out solar panel...  But looking at it, the desert is not the natural home of the Jazz...
Title: Re: Any way to charge an empty starter battery from the one in the boot?
Post by: nowster on November 25, 2021, 04:23:47 PM
You could use a chain of resistors and tap off your 14 - 15v that way.
Not particularly efficient, though, and not very well regulated. You'll need quite beefy resistors as they're going to get blooming hot feeding a lead-acid battery. Buck converters can get up to about 90% efficiency.

You could alternatively use a motor-generator (or motor-alternator) set with the correct voltage ratings.
Title: Re: Any way to charge an empty starter battery from the one in the boot?
Post by: culzean on November 25, 2021, 04:39:12 PM
You could use a chain of resistors and tap off your 14 - 15v that way.
Not particularly efficient, though, and not very well regulated. You'll need quite beefy resistors as they're going to get blooming hot feeding a lead-acid battery. Buck converters can get up to about 90% efficiency.

You could alternatively use a motor-generator (or motor-alternator) set with the correct voltage ratings.

You are in the desert - unlike in UK solar actually works in desert areas....

Do motor generators cater for 12volt DC ( or 15 volts ),  or do you need a 230 volt AC to 12 ( 15 ) volt battery charger as well ?

Where does the fuel for the motor-generator come from ?
Title: Re: Any way to charge an empty starter battery from the one in the boot?
Post by: culzean on November 25, 2021, 05:04:44 PM
Imagine you are in the middle of a desert, and your hybrid jazz 2012 has an empty starter battery. But you have thick and long enough wires, a knife, spanners, screwdrivers and reasonable electric skills. Is there any way to charge an empty starter battery from the one in the boot?

Anyone who had even 'less than reasonable' electrical skills would not attempt to connect a 200 volt battery to a 12 volt one.
Title: Re: Any way to charge an empty starter battery from the one in the boot?
Post by: Kremmen on November 25, 2021, 05:24:23 PM
Don't our Jazz MK4 charge the 12v from the HV job?

Some clever electronics there then.
Title: Re: Any way to charge an empty starter battery from the one in the boot?
Post by: culzean on November 25, 2021, 06:19:04 PM
Don't our Jazz MK4 charge the 12v from the HV job?

Some clever electronics there then.

It is easy to do with electronics,  but not in the middle of the Western Desert with a flat battery..

Most mobile devices like phones and laptops contain chips that can change the voltage level of the battery to the voltage needed to power various parts of the device, both up and down. mainly using fast switching FET to make the devices more efficient and prolong battery life.
Title: Re: Any way to charge an empty starter battery from the one in the boot?
Post by: nowster on November 25, 2021, 06:21:54 PM
Don't our Jazz MK4 charge the 12v from the HV job?

Some clever electronics there then.

It'll be a version of the buck converter, as previously said, or maybe a chopper/step down circuit like is found in a switched-mode power supply (SM PSU). They tend to work at about 340V DC (rectified 240V mains) on the primary side.

And the motor could be DC powered (off the battery), driving a generator or alternator on a common shaft. (These used to be very common to provide clean mains supplies to the likes of mainframe computers back in the day.)
Title: Re: Any way to charge an empty starter battery from the one in the boot?
Post by: Jocko on November 25, 2021, 06:22:36 PM
Where does the fuel for the motor-generator come from ?
The HV battery runs the motor which drives the generator which charges the battery.
Title: Re: Any way to charge an empty starter battery from the one in the boot?
Post by: nowster on November 25, 2021, 06:26:35 PM
Don't our Jazz MK4 charge the 12v from the HV job?

Some clever electronics there then.

It is easy to do with electronics,  but not in the middle of the Western Desert with a flat battery..

All you need is to have enough power to boot up the ECU to switch on the HV-to-12V converter to charge the battery. Once you've bootstrapped that, the converter can power the ECU (at 12V) whilst it's charging the battery.

I dare say if you knew exactly where to apply power and control signals, you could switch on the DC-DC converter with a PP3 battery.
Title: Re: Any way to charge an empty starter battery from the one in the boot?
Post by: culzean on November 25, 2021, 06:32:09 PM
Use your mobile to contact AA ( Abduls Automotives )  recovery service,  give them the map reference and they will turn up with a team of camels and a sledge and tow you to nearest garage. 
Title: Re: Any way to charge an empty starter battery from the one in the boot?
Post by: culzean on November 25, 2021, 07:00:53 PM
Doesn't the 2012 model use the hybrid battery to start engine anyway ?
Title: Re: Any way to charge an empty starter battery from the one in the boot?
Post by: Bonobo on November 25, 2021, 11:23:12 PM
The drive battery holds a high voltage, something like 180volts.
But it should then consist of 180/1.5=120 1.5 v cells, right? So, is it possible to connect to only 8 out of those 120 cells to get exactly 12 volts?
Title: Re: Any way to charge an empty starter battery from the one in the boot?
Post by: nowster on November 25, 2021, 11:55:19 PM
The drive battery holds a high voltage, something like 180volts.
But it should then consist of 180/1.5=120 1.5 v cells, right? So, is it possible to connect to only 8 out of those 120 cells to get exactly 12 volts?

They don't use Ever Ready HP7s.  :D

NiCd and NiMH are 1.2V, but it's not those either.

The HV battery uses Lithium Ion cells which are not 1.5V, but usually 3.6 or 3.7V.

Many portable booster batteries are indeed four Lithium Ion cells wired in series to give about 14.4-14.8V output.
Title: Re: Any way to charge an empty starter battery from the one in the boot?
Post by: Kremmen on November 26, 2021, 03:06:26 AM
Use your mobile to contact AA ( Abduls Automotives )  recovery service,  give them the map reference and they will turn up with a team of camels and a sledge and tow you to nearest garage.

..... or a suitable WhatThreeWords location....... 'stuck, bored, help'
Title: Re: Any way to charge an empty starter battery from the one in the boot?
Post by: culzean on November 26, 2021, 09:03:09 AM
Imagine you are in the middle of a desert, and your hybrid jazz 2012 has an empty starter battery. But you have thick and long enough wires, a knife, spanners, screwdrivers and reasonable electric skills. Is there any way to charge an empty starter battery from the one in the boot?

Let us know when you are going into the desert in the Jazz and we will have a crowd fund to buy you an emergency starter battery....

Now lets think what will happen if you run out of fuel,  can you use cactus juice instead of petrol ?
Title: Re: Any way to charge an empty starter battery from the one in the boot?
Post by: JimSh on November 26, 2021, 09:04:21 AM
Are you allowed one of these?

https://www.ebay.co.uk/p/26031190058?iid=233129991124
Title: Re: Any way to charge an empty starter battery from the one in the boot?
Post by: culzean on November 26, 2021, 09:17:40 AM
Are you allowed one of these?

https://www.ebay.co.uk/p/26031190058?iid=233129991124

Those little solar panels are just a maintainer to make up the losses from parasitic drain, to try to stop battery going flat when parked for a long time, they normally supply millamps - what you need to actually charge a battery is something like this

https://www.amazon.co.uk/powkey-100W-Charger-Monocrystalline-Parallelable/dp/B08NV2FPHJ/ref=sr_1_1_sspa?keywords=folding%2Bsolar%2Bpanel&qid=1637918075&sr=8-1-spons&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUExUkxZRFVPNVBGQzFRJmVuY3J5cHRlZElkPUEwNzYzMjg2M082SERNMkJWOTQwMyZlbmNyeXB0ZWRBZElkPUExMDAyMzAyOE5IUzBXUVBWUVcmd2lkZ2V0TmFtZT1zcF9hdGYmYWN0aW9uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl&th=1
Title: Re: Any way to charge an empty starter battery from the one in the boot?
Post by: John Ratsey on November 26, 2021, 07:05:50 PM
Doesn't the 2012 model use the hybrid battery to start engine anyway ?
No. The hybrid Mk 2 Jazz still has a starter motor to initially get the engine running but once the engine has warmed up and the car is sure that there's charge in the big battery (nickel-based IIRC so vulnerable to self-discharge) then it will use the big battery to restart the engine when the stop-start activates.