Britprius

This so called battery specialist knows nothing about Toyota/Lexus Hybrids. The 12 volt battery has nothing to do when the engine starts, and stops. It is the HV battery that provides the power to start the engine, and also keeps the 12 volt battery charged by an inverter. This keeps the 12 volt battery on charge as long as the car is in ready mode there being no alternator or starter as such as in other stop start systems where the 12 volt battery provides the engine turning power. The 12 volt battery only has to boot the computer systems (ECU's) and turn a few pumps as you put your foot on the brake, and press start. After this it is always being charged even if the engine is not running. There is nothing special about the 12 volt battery. It does have a temperature sensor that can be gently prized out of the top and just taped to the top of your new chosen battery. This is there to help regulate the charging voltage that is dependent on temperature. Some hybrids such as the Prius use an AGM battery (absorbed glass mat) that has no free liquid acid. This is used because in the Prius, and Lexus CT (Prius clone) the battery is in the passenger compartment, and in case of a rear end accident the battery will not splash acid onto the occupants of the car. Most batteries today are of the sealed type with a vent at one or both ends these can be fitted in the Lexus GS without any problems. If double ended vented one end vent is simply plugged with a cap provided. Good quality batteries are available (Bosh, Varta, and many more) at around £65 with up to 5year guarantees.

I have come across this same problem with a Prius. It is worth trying putting the steering in the strait ahead position, and the disconnecting the 12 volt battery for a few minutes. This has been known to cure the problem, and since it costs nothing is worth a try. Changing or disconnecting the 12 volt battery with the steering in a turned position can cause the fault.

Carrying a starter pack is a good idea in this situation, but be very aware connecting the jump pack with reverse polarity even for a split second will do £100's if not £1000's in damage to the electrical system. If the car is in an outside car park a cheap solar panel in a south facing window will keep the battery charged.

Although not the purpose of a dash cam I do not see how it could be illegal to use through the display while on the move. The Mercedes has a forward facing camera with infrared night vision and that is not illegal. Also I tow a caravan with rear facing camera, and this view was shown on the MFD of my Prius giving a much better view than it would be possible to get with door mirrors. I intend changing the system over to my GS to give the same results. You can use the reverse camera input for this, but be aware unless wired correctly the reversing lights may come on while the camera is being displayed. In the Prius the best place to tap into the wiring was under the passengers seat where the navigation DVD play is. I do not know the position of this in the RX or GS untill my car is delivered. When I have the car , and have time to fit the camera wiring I will update hear with the details.

I did tow my caravan with the Prius but it was lacking power for 1 in 5 hills. on motorways it towed well at the legal limit "60 mph" returning an amazing 49 mpg. This with a 15 toot 1 ton van.

At 70 mph you would be looking at 55 mpg winter 60 mpg summer. Road noise is the most noticeable thing, but that depends greatly on the road surface and the tyres used. Choice of tyres on the Prius is critical to good economy. Tyres with a fuel rating of A or B are a must and ideally tyres with a rating of 67 to 68db for noise. The OEM tyre size is 195/55/16, but going up to 205/55/16 improves road manners enormously, and also have the advantage of being 25% cheaper for the same make and type of tyre. Going up one size seems to have no effect on economy. The 1.8 Prius will achieve about 5mpg better than those quoted above on motorways. The reverse is the casein towns and rural areas.

The Prius is much maligned by programs like Top Gear. In reality the car is much quicker than the 0 to 60 time of 10.2 seconds suggests. In some ways rather like the GS the off the line acceleration "with no engine running" is remarkable. The front tyres may cherp a little on a smooth dry road as the electric motors huge torque at zero revs gets the car away instantly with no wheel spin. The traction control really works well in that situation. The 1.5 version will cruise all day at 70 mph still leaving reasonable acceleration to overtake. Top speed is 113 electrically limited. It is quite remarkable to see the mpg reading 99.9 mpg on flat and the slightest down hill sections of motorway at 70 mph. I am not saying it is a flying machine, but it does work very well. If or when I give up towing I will be going back to a Prius, and for those thinking about one have a test drive. Around town the 1.5 version does best on fuel. For motorway use the 1.8 does better. Performance otherwise is about the same. I belong to Prius Chat. It is world wide, but has an American byass as that's where most are sold.

I am just in the process of changing from a 1.5 Prius to the GS450H. The Prius is the most reliable, economical car I have ever had returning a genuine 58 mpg in the winter and rising to 67 mpg in the summer with £10 a year road tax.. The HV battery is still under guarantee and can remain so if serviced by Toyota or has a yearly health check till it is 11 years old irrespective of millage. My prime reason for the change is the requirement to tow a caravan. In a 123,000 miles of ownership the sum total of repairs was two rear shocks "under guarantee one was leaking both were changed" and a front NS wheel bearing at 96,000 miles. Services were carried out at the Toyota dealers and are set price at 10,000 mile intervals. The Gs will have a lot to live up to.

Yes I stand corrected (a senior moment). I will edit the post to reflect this.

The Prius modules are 6 cell nominal 7.2 volts. The RX400/450450H modules are 8 cell nominal 9.6 volts. Both rated at 6.5 amp hrs. This means the modules are not interchangeable without considerable fudging of voltage returns to the battery ECU. The GS450H module are the same as the Prius. (Above edited to clarify wrong information) I did a considerable amount of work on methods of re-hydrating Prius modules "documented on Prius Chat" that would work just as well on the longer, and higher voltage Lexus versions. The method requires drilling two small holes in a module "about 1mm" to enable the topping up of all 8 cells equally. Distilled water can be used but I used a solution of water, and sodium hydroxide. Potassium hydroxide can also be used. In manufacture a mixture of both is used. Results on old gen1 (2002) modules bought them back to full capacity in fact over 6.5 amp hrs.

New member moved across from Prius Chat having just changed from a Prius to a GS450H. Thanks Giles for the information on the pump motor bearings. I live in north Herefordshire, and would be happy to buy you a pint on behalf of the other members. In time I hope to contribute much to this forum as I hope I did on Prius Chat. I have an electronics background that is useful working on hybrid systems. I also have Techstream so am able to read all fault codes, and am happy to read codes for anyone able to get to me.

I found this forum through "Prius Chat" where I have been a member for many years. I have now moved across the family to join the Lexus community.