Understanding the High and Low Voltage Systems

[Tabvla]

I am trying to understand the workings of the two battery systems used in the PHEV.

The best way to do that would be if there was a schematic diagram of the Input and Output from the two systems. So if anyone has such a diagram I would be very grateful if you would send me a copy. The information that the diagram should contain should include at least the following: -

1. Low Voltage 12v Lead Acid Battery System

- How is the Lead Acid battery charged?
- Which systems receive their power from the 12v battery
- Which systems (if any) receive their power from both the Lead Acid and the Li-Ion batteries

Question : If the Lead Acid battery is "flat" is it safe to charge that battery with a standard 12v battery charger. Currently I have a 12v battery charger that charges via the cigarette lighter. This is a very simple, easy and safe way to charge a Lead Acid car battery. Would this charger be a safe option to use with the PHEV 12v battery while the battery is connected as normal?

2. High Voltage Li-Ion System

- How is the Li-Ion battery charged (Slow Charge, Fast Charge, Regenerative Charge, ICE Charge)
- Which systems receive their power from the Li-Ion battery
- Which systems (if any) receive their power from both the Lead Acid and the Li-Ion batteries

Question : If the PHEV is not used for a long period of time (say 3 months) should it be left plugged into the mains electricity charger?

Thanks in advance if anyone has a schematic diagrom of the PHEV electrical systems.

T.

 

[maby]

I am trying to understand the workings of the two battery systems used in the PHEV.

The best way to do that would be if there was a schematic diagram of the Input and Output from the two systems. So if anyone has such a diagram I would be very grateful if you would send me a copy. The information that the diagram should contain should include at least the following: -

1. Low Voltage 12v Lead Acid Battery System

- How is the Lead Acid battery charged?
- Which systems receive their power from the 12v battery
- Which systems (if any) receive their power from both the Lead Acid and the Li-Ion batteries

Question : If the Lead Acid battery is "flat" is it safe to charge that battery with a standard 12v battery charger. Currently I have a 12v battery charger that charges via the cigarette lighter. This is a very simple, easy and safe way to charge a Lead Acid car battery. Would this charger be a safe option to use with the PHEV 12v battery while the battery is connected as normal?

2. High Voltage Li-Ion System

- How is the Li-Ion battery charged (Slow Charge, Fast Charge, Regenerative Charge, ICE Charge)
- Which systems receive their power from the Li-Ion battery
- Which systems (if any) receive their power from both the Lead Acid and the Li-Ion batteries

Question : If the PHEV is not used for a long period of time (say 3 months) should it be left plugged into the mains electricity charger?

Thanks in advance if anyone has a schematic diagrom of the PHEV electrical systems.

T.

The 12v battery runs everything except the drive motors. It's charged from the high voltage battery and indirectly from the high voltage generator. The 12v battery is not particularly high capacity - a lot less than the equivalent in a conventional car - since it does not have to be able to source the very high cranking currents required by the starter motor. When the car is locked and powered down, the only drain on the 12v battery will be the security systems and, for a GX4, the wifi that supports the remote control application. It reportedly recharges itself from the high voltage traction battery if the car is left unused long enough. Presumably it does this in an intelligent way in order to avoid ever dragging the traction battery down low enough to damage it. I'm sure that you can charge it from a standard charger, though I'm never too happy about doing this through the 12v lighter socket - it usually is safe, there is potential for switching and safety circuits in the feed to that socket - it is intended as an outlet, not an input.

The high voltage traction battery is charged from a number of sources - the generator on the petrol engine, the motors running as generators during regenerative braking, the internal mains driven battery charger and, in the case of an express charger, the external battery charger. It drives the traction motors and can source the power to charge the 12v battery. I don't think any systems draw power from both batteries. I don't think it would do any harm to leave it plugged in for long periods - the control circuits cut the power as soon as the battery is fully charged. The Mitsubishi recommendation is to plug it in for a few hours every few (three?) months.

 

[user 258]

Hi,
I would just add that the traction battery also powers the a/c and heater due to their large power requirements.
Kind regards,
Mark

 

[Tabvla]

Maby & Mark.... many thanks for your informative replies.

So let me see if I understand this correctly......

A. Low Voltage Lead Acid 12v Battery

1. Relatively low-capacity compared to regular car batteries
2. Charged from the Li-Ion generator (or should that be alternator) via the Li-Ion battery pack
3. Powers all electrical systems except for the Electric Motors; Air Conditioning and Heating systems
4. The negative terminal is earthed to the vehicle chassis as is normal in a standard 12v configuration

B. High Voltage Li-Ion Battery

1. Charged from mains electricity; regenarative braking and the ICE via the Li-Ion generator
2. Powers the Electric Motors; Air Conditioning and Heating Systems
3. Charges the Lead Acid 12v battery
4. The negative terminal is not earthed to the vehicle chassis but runs a negative cable to the systems that it powers

C. A Question about a Flat Battery

Based on the above my understanding therefore is that if the 12v battery is "flat" the PHEV won't start and therefore the ICE cannot be used to charge the Li-Ion. Is this correct? In a situation where both the Li-Ion and the Lead Acid were "flat" and there was no mains electrical power available would it be possible (and safe) to connect Jump-Cables from a fully charged 12v car battery to the PHEV 12v battery and get the ICE started that way? If the answer to that is "No" then what other solution is there because the AA, RAC and the man with the little Green Flag won't be able to help either... :?

D. A Question about how the ICE starts

Maby, in your reply you wrote as follows.... ".....since it does not have to be able to source the very high cranking currents required by the starter motor....." I did not know that so I am interested to know how do you start a petrol engine without a starter motor?

Thanks for your help.

T.

 

[ian4x4]

As I understand it the generator is fixed to the engine and also acts as a starter motor when needed.

The link below looks at most transmission systems and has a very good diagram of the GKN (PHEV) gearbox in figure 7. It shows the power path the (front) gearbox in all 3 modes of operation.

http://www.jsae.or.jp/e07pub/yearbook_e/docu/15_drivetrain.pdf

 

[Regulo]

In a situation where both the Li-Ion and the Lead Acid were "flat" and there was no mains electrical power available would it be possible (and safe) to connect Jump-Cables from a fully charged 12v car battery to the PHEV 12v battery and get the ICE started that way? If the answer to that is "No" then what other solution is there because the AA, RAC and the man with the little Green Flag won't be able to help either... :?

T.

In the owners' Manual there's a step by step guide to jump starting with another vehicle, it's pretty much as any other vehicle as I recall. I'm not going out to get the manual from the car, as it's raining heavily here!!

 

[user 258]

In a situation where both the Li-Ion and the Lead Acid were "flat" and there was no mains electrical power available would it be possible (and safe) to connect Jump-Cables from a fully charged 12v car battery to the PHEV 12v battery and get the ICE started that way? If the answer to that is "No" then what other solution is there because the AA, RAC and the man with the little Green Flag won't be able to help either... :?

T.

In the owners' Manual there's a step by step guide to jump starting with another vehicle, it's pretty much as any other vehicle as I recall. I'm not going out to get the manual from the car, as it's raining heavily here!!

Hi,
Although it is pretty much impossible in practice, should you find yourself with a flat traction battery there is nothing you can do to jump start it.

The 12v battery simply powers up the computer systems which enables the traction battery to start the engine. No traction battery equals no running engine.

I wouldn't worry about getting the traction battery flat. The car has been designed with a large margin of error to make sure this doesn't happen.

A flat 12v battery is much more likely and getting a jump start is easier than with any other car (since the jump start doesn't have to turn the engine over). If this worries you, just carry a small 12v alarm panel type battery and use that to jump start your own car (as I do).

Kind regards,
Mark

 

[maby]

As I understand it the generator is fixed to the engine and also acts as a starter motor when needed.

The link below looks at most transmission systems and has a very good diagram of the GKN (PHEV) gearbox in figure 7. It shows the power path the (front) gearbox in all 3 modes of operation.

http://www.jsae.or.jp/e07pub/yearbook_e/docu/15_drivetrain.pdf

This is true. Also I believe, though I have not seen it stated anywhere, that the designers play tricks with the valve timing to decompress the engine when it is not running - this makes it far easier to spin up and the generator (running as a motor) can get the engine revs right up to normal running speed - the Prius has been doing this for many years. This reduces the load on the battery and makes the starting far quieter and smoother. It also means that they can rapidly get the engine in synchronisation with the rest of the drive train when they are switching to direct drive or parallel hybrid mode.

 

[Rooksdown]

Hi Tabvla

Just one interesting quirk is that the 12V supply also runs the heated windows. So turning the heated windows on and off will often cause the engine to start stop too.

Tks

Paul

 

[maddogsetc]

Just one interesting quirk is that the 12V supply also runs the heated windows. So turning the heated windows on and off will often cause the engine to start stop too.

I'm not sure I follow your reasoning here - why is the heated screen more likely to cause ICE to start than say the headlights or heated seats?

 

[jaapv]

Hi Tabvla

Just one interesting quirk is that the 12V supply also runs the heated windows. So turning the heated windows on and off will often cause the engine to start stop too.

Tks

Paul

Windows? As far as I am aware it has just the normal rear window heating.