TouringRob

Thank you Barry, I have a friend who attends yearly (out of the virus era) but have not been myself, I will indeed aim to go - will be a nice day trip for my son before he gets too old to not want to spend time looking at old cars with me any more! Yes sorry for the digression OP 🙂

I couldn't agree more, I have a 1968 Vauxhall Viva tucked. I am hoping to restore this summer and it looks VERY easy to work on compared to anything from this century!

No problem Barry, I really only know battery basics compared to some out there so I will watch your video with interest! As Herbie mentioned above the LED lights are pretty efficient, I'm not sure what the power rating of the LED units is but I would guess at 5-10watts each, so 10-20watts total, which is a total current draw of between .8 and 1.6 amps which given the capacity of your HV battery is not an issue. The charge controller will account for this so other than the occasional helpful neighbor it shouldn't be a problem. I'm not familiar with the 450h but I wouldn't be surprised if there was a fuse you could temporarily pull while building work is going on and its parked? Good luck with the building chaos, we've had scaffolding up since 4th Jan for a 1 week job - then all the roofers caught covid 🤦‍♂️ And PS - don't let the engineer bit fool you I get plenty wrong - met many non qualified engineers whos knowledge has humbled me.

Thats awesome, I have a keen interest in high end audio!

AGM mode will have a lower current limit. Regular batteries also don't like high current charging when at low temperatures. Your charge voltages are wrong, and the hybrid charge scheme will not overcharge a regular lead acid. The issue is actually the other way round, a regular charge system is bad for an AGM, while you can charge a regular lead acid using the AGM scheme (as proven by you CTEK AGM/Low temp mode).

Jesus, that was longer than anticipated. Congrats if anyone makes it through. TL:DR - Charging is a non issue.

Lead acid and AGM self regulate. That means that if you charge with a constant voltage, regardless of set current when the battery approaches full charge it will draw less and less current. The float voltage of AGM is 13.6V, while lead acid (wet) is 13.4 this takes a lead acid upto 2.26v per cell which is permissible and within spec for most (all?). The absorption voltage (which is the maximum charge voltage) is 14.7 for AGM and 14.8 for standard lead acid which is also so similar so as not to be an issue. The float voltage should be adjusted according to battery temperature. Flooded lead acid batteries are relatively indifferent to higher temperature charging, thats why the majority of old tech cars do not have a temperature sensor on the battery while most agm equipped cars will. An agm battery requires the float voltage to be lowered more than a fla for every extra degree in temperature. AGM batteries come with a maximum charge current recommendation, this is typically 0.2C-0.3C, so 0.2 x capacity, fla batteries are less intolerant of charge current and can often be charged at 1C (if not more) without damage. An overcharged fla battery will vent and require 'topping up' so one of big (marketed) advantage of an agm is that it is maintenance free. Regular cars will simply charge their batteries at 14.4V forever, this poses no real issue to a fla other than the need to very occasionally add distilled water, since an agm is sealed and cannot be maintained this 14.4 (2.4/cell) at some point may represent an overcharge - most information simply states that overcharging an AGM will dramatically shorten its life, likely because they have a pressure relief and so vent which means lost electrolyte(?) The charge system in an AGM equipped Toyota/Lexus will likely be doing a number of things. It will charge the battery to absorption voltage and then drop charge voltage to float voltage (where it will be maintained) these values will be altered depending upon battery temp (hence the additional sensor). Above a certain voltage charging will be indefinitely halted. The maximum charge current will be limited since a flat or low voltage lead acid of any type will draw a lot of current, enough that the electrolyte can boil, not such an issue if they vent and can be topped up - incidentally the gassing voltage for fla is 14.4V at 25deg C, at higher temps the gassing voltage is lower. The gas is hydrogen which is explosive at concentrations of over 4%, a normal cause of battery explosion is a single low (fluid) cell, the cell fills with hydrogen and at some point explodes. The other gas emitted by overcharge is hydrogen sulfide which is both explosive and toxic - filling up a car with that would be bad and likely another consideration for using an agm when the battery is located within the car. So from that blurb. You should NOT charge an AGM type lead acid using a regular charger (unless you know what your doing a little) OR install an AGM in a car which usually has a regular flooded/wet battery, the battery maybe overcharged which will at best shorten its life. You CAN install a flooded lead acid where an AGM has previously been used because the charging method is compatible this way round. AGM is maintenance free, a non sealed flooded battery is not. An AGM is able to be deep cycled to 80% without damage, a wet lead acid can be deep cycled to 50% without damage, an AGM has a lower self discharge rate (so can be left for longer with needing to be charged) I believe around half that of FLA. So another consideration when installing a FLA where an AGM previously was fitted is that you do not allow the car to sit idle for long periods otherwise you will shorten the life of your new battery. Apparently an AGM can accept charge faster than a FLA however I dispute that due to the fact that the don't like high charge currents but I'll leave that for others who know more. On the bench an AGM is technically 'better' in practice with this application I do not believe it is so clear cut. Thats charging covered, Now the biggest advantage an agm has, and possibly a very big tick in their favor for an OEM - They can be shipped as non hazardous goods and require no paperwork. Health and safety I'll leave to others. PS - apologies for interchanging terms so much, its late and I can't be bothered to go back and correct it all, maybe a few typos too so please forgive me. AGM - Absorbent glass mat FLA - Flooded lead acid WET - Flooded lead acid

Just come in from the cold - installing a lintel in winter is a silly silly idea so need to time to digest your reply Barry but while I do I will state this: While I am stating that a regular lead acid battery is compatible and is a good alternative to the OEM battery I am not discouraging anyone from using their own judgement and to draw their own conclusions from what I've written my only motivation is to assure people that they are not doing anything wrong or outrageously dangerous - they can sleep easy and save some money. As for my anecdotal views and qualifications? Other than being a long term home mechanic having restored and maintained quite a number of vehicles I am also a qualified electronic engineer and for some time owned a company which designed automotive electronics. The endless research and development that role required does give me some faith that what I've written is not dangerous and will not cause harm to those who follow it, their vehicles or their wallets. However I would encourage anyone to not let their low voltage battery run flat routinely and to use their own best judgement - I will freely admit that I have not worked for any OEM and that Lexus/Toyota will have done their R&D so take my view point as opinion. EDIT* I'm not a battery engineer so only really know the basics, my father however has a life times worth of knowledge in this field and has I believe several patents specifically covering battery charge technology - next time we speak I will ask for his views as they will be more in depth and qualified than mine, it might very well be that he totally disagrees with me but he will at least be able to give educated reasons for his disagreement. Sorry to hear your car was rear ended and glad your weren't injured - let us know if you find the thread with the exploding battery, would be interested to know if the battery was improperly vented. Rob

Today my car passed its MOT with no secondary cat, just a straight pipe. Called to check first the answer was: "We do not do an emissions test but will perform a visual inspection. If the primary cats and sensors are in place and we have no other car to compare yours against then we do not know which cars have secondary catalysts and which have simply had a silencer removed therefore we will pass it" Naturally MOT found more bushes to replace, very annoying as one of the front lower arm bushes has play and the lower arms were new last year from Lexus Parts direct... I've been worrying that they wouldn't pass it, so much so that I have bought a catalyst to weld in but with more snow incoming wanted the RX legal again. So straight pipe and a slightly friendly chat seems to do the trick 👍

Interesting that the ES has a conventional battery in the boot. I would love to know their rational for making choices like this but would imagine that Toyota who are fond of over-testing would have good reasons, while other manufacturers I am positive under-test which makes me doubt many of their engineering choices.

I believe both. The AGM for in cabin seems to be a popular modern choice which is why I suspect it is legislated somehow, or possibly counts towards crash test safety ratings in some way. Was under the impression the 400 used AGM also, but have never looked and would not be amazed if it was wet given its in the engine bay which AGM doesn't typically like (heat). I haven't actually seen the battery location for the 450 in person but do know that 10 years ago a wet battery in the boot was the norm. Another consideration is that an overcharged battery which is able to vent can become a fire/explosion risk, that may have counted towards their original decision, AGM on paper should be more reliable full stop (although owners say different). But lets face it, a leaking battery after an accident would be the least of my concerns given how severe the impact would need to be! Battery is presumably under the floor/carpet, after looking over a terribly rear ended E36 touring some years ago which had the battery about as exposed as you could get for that type of accident the battery was cracked, all of the acid had leaked - none of it was in the cabin (beyond the battery box). Id likely choose an AGM or gel battery if the car was used offroad or on track lots due to vibration and the risk of turn over. I would trust a conventional lead acid in the boot of any car over say charging a Tesla in my garage which many seem very happy to do. Not trying to convince people either way but just wanted to put peoples minds at rest that replacing their original battery with a cheaper standard alternative isn't going to damage their vehicle and in my opinion is very unlikely to represent any real world safety trade offs.... Put the money saved towards some good tyres!

Barry, I have indeed watched the video and several others by Proff Kelly, as an EE I do not find myself so in awe of him as you seem to be, he makes no comparison between a regular lead acid and agm for example, and only touches on some minor benefits of having an agm. Yuasa themselves state that the only benefit of AGM in a hybrid vehicle with charging systems such as ours is that an AGM is able to survive deep cycling better than a lead acid. My guess is that Toyota/Lexus were concerned about long term reliability of a regular wet battery (sealed or not) - it is technically the better solution and I am not surprised that Toyota who are very mindful of long term reliability would choose the better technical solution. A good quality, appropriately vented wet battery that the owner does not leave to go flat has zero disadvantages in this application. You are naturally free to do as you will but I just wanted to make that point clear for other future viewers who might feel obligated to spend £300 with Lexus on a battery. PS. You should keep the E39! They are appreciating.

Yes indeed, a deep cycle will be more tolerant to being left to go flat. If you never let the battery go flat a deep cycle will have a similar life time to a good quality normal battery I believe.... but seeing as these cars seem to like to flatten their batteries a deep cycle wasn't a bad decision at all. And agree with the 4A point, that is actually a fairly low figure compared to the capacity, its fine to charge either type at 4A. The battery will self regulate as it reaches float voltage so you only need to current limit during the first part of the charge cycle. Where you can hurt batteries is if you allow them to draw an excessive amount of current when they are flat. Still miss the E46! Rob

Barry I think you are massively overthinking this. I would have absolutely no hesitation in fitting a wet battery in place of the AGM in this particular application. The battery doesn't have a hard life if you don't let it go flat (deep cycle), in fact it has the easiest life of all given that its being charged at a low rate and is never subjected to high current draw a normal stop/start car would be. Worried about battery acid inside the car? Remember that until mid 2000's there were a great many cars with a battery in the cabin (some with two!) without issue (BMW E36/E46 etc). This will be a change driven by legislation rather than being a practical requirement. There is nothing else to consider, the charge methodology used for and AGM type battery is compatible with wet lead acid (not necessarily the other way round!). My 400 battery is the original (12 years old now) and when it finally dies I will use a wet Yuasa, the 400 has gives the battery a harder life as it is within the engine compartment. Yuasa is great choice, for good deals check out Tanya on eBay, I have bought several batteries from them recently all have arrived within a day and are superbly packaged/keenly priced.

Glad you got a reasonable quote in the end! We use ours as a family car and honestly its been great, I've not regretted buying it at all so goof luck with the hunt!