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Any - Real Fuel Saving at Low Cost - Firmbutfair

If you externally charge up your 12 volt car battery, using say, an intelligent charger, just before making a long familiar journey, you can enjoy a significant fuel saving for the whole round trip, that will yield an indicated fuel economy similar to that achieved by HJ Real mpg readers running similarly sized but much more expensive hybrid engined cars such as the Toyota Yaris Hybrid.

For example, improving fuel economy from 51 mpg to 59 mpg in June/July 2019 on a 94 mile round trip, with the car driven gently (no aggressive acceleration or braking) but cruising at around 65 mph on dual carriageways. That is a 16% improvement in fuel economy. The 51 mpg figure is what the car has achieved on the same journey without the battery pre-charge before hand. My car is a 3 cylinder, 1 litre, five door hatchback, with gasoline direct injection and is rated at 100bhp, first reg Dec 2016, driven two up with some luggage.

This result is perhaps surprising when you consider the total energy stored in a fully charged 70Ah 12 volt lead - acid battery is around 910 Watt.hours. Given that each bhp is roughly equivalent to 750 watts then the energy stored seems trivial compared with the 100 bhp (75Kw) engine but then when you look into it you will see that it may take as little as 16 bhp (12 Kw) to cruise at 60 mph and thus if the alternator has to provide little or no charge to the battery during the journey then maybe 1.8 Kwh less battery charging energy is demanded from the engine. 1.8/12 = 0.15 = 15% energy saving! Even these numbers do not quite stack up, unless the 'engine to alternator to charging' is very inefficient, however a very real saving is recorded every time the battery is pre-charged!

Thus if we were all to 'plug in' our regular cars before each journey, we could save a significant amount of fuel. I wonder why the car manufacturers did not offer us this option as an alternative to the much more expensive hybrid and its cousin the so called 'plug in' hybrid? Just asking !

Edited by Firmbutfair on 13/07/2020 at 23:15

Any - Real Fuel Saving at Low Cost - Terry W

I think your logic is flawed.

The engine charges the battery as you drive - thus when you stop the battery is fully charged.

Next time the car is used it is starting with a fully charged battery. So I am unclear how keeping the battery on charge before the journey makes any difference to the battery charge or economy.

Any - Real Fuel Saving at Low Cost - mcb100

It's not a completely novel thought - Mazda have been there with the snappily named i-Eloop which consisted of a variable output alternator and a capacitor. It harnessed regenerative braking to charge the capacitor at up to 25V, which in turn would allow the alternator to be 'decoupled' (reducing drag on the engine) as the capacitor then powered the vehicle's electrics.

So the principle works, but I'm not convinced on the above figures....

Any - Real Fuel Saving at Low Cost - RT

Smart alternators have been around for a couple of decades - Ford fitted then to Focus and Mondeo around 2000 and Hyundai were using them on the 2006 Santa Fe - in simplistic terms they stop charging when the engine is accelerating the car but switch to full charging when lifting off the throttle, effectively a low level of regenerative braking.

With the pressure on manufacturers to reduce CO2 figures I'd expect almost every new car to have a smart alternator but the improvement is way less than the OP suggests.

Any - Real Fuel Saving at Low Cost - mcb100

The above figures seem to be taken on the strength of trips in Summer in lockdown traffic. What we don't know are traffic conditions on previous runs or ambient temperature. Both will make significant contributions to fuel economy.

Edited by mcb100 on 14/07/2020 at 08:42

Any - Real Fuel Saving at Low Cost - thunderbird

For example, improving fuel economy from 51 mpg to 59 mpg in June/July 2019 on a 94 mile round trip, with the car driven gently (no aggressive acceleration or braking) but cruising at around 65 mph on dual carriageways. That is a 16% improvement in fuel economy. The 51 mpg figure is what the car has achieved on the same journey without the battery pre-charge before hand. My car is a 3 cylinder, 1 litre, five door hatchback, with gasoline direct injection and is rated at 100bhp, first reg Dec 2016, driven two up with some luggage.

The same trip but on different days so not really possible to compare. Weather is a major factor as well as traffic. No 2 journeys are exactly the same. We travel the exact same route to Scotland twice a year (Covid permitting) and normally we are pretty lucky with traffic and the 430 miles takes us about 7 hours driving time (+ or - 15 minutes), an average of just over 60 mph. When we did the trip in the 1.6 TDCi Focus the best we saw was about 58mpg, the worst about 52 mpg and always with the same load. We actually did see worse but that day there were 2 fatal accidents on route which both caused large jams and the trip took over 10 hours.

then when you look into it you will see that it may take as little as 16 bhp (12 Kw) to cruise at 60 mph

I remember reading in my youth it was actually about 25 bhp was needed to do 70 mph but even back then it was dependent on the size and weight of the car. These days cars are on average much bigger, much heavier and have much wider tyres which also create more drag thus I think its reasonable to assume that your 16 bhp and even my 25 bhp figures are both way off the mark. As proof of this think back to the XR3i of 40 years ago, 105 bhp and it did 0-60 in about 8.5 seconds. Our Fabia 1.0 TSi 110 bhp car is about the same size as that Escort with a little more power (loads more torque) but weighs more and has 215 tyres not 185's like the Escort. The 0-60 is nearer 10 seconds.

Any - Real Fuel Saving at Low Cost - edlithgow

Smart alternators have been around for a couple of decades - Ford fitted then to Focus and Mondeo around 2000 and Hyundai were using them on the 2006 Santa Fe - in simplistic terms they stop charging when the engine is accelerating the car but switch to full charging when lifting off the throttle, effectively a low level of regenerative braking.

https://eprints.usq.edu.au/31465/1/Rendle-Short_K_Snook.pdf

Student project on a retrofit Alternator Interrupt Circuit to give old stupid alternators some fuel saving smarts.

Seems quite a good dissertation

The snag for such regenerative charging for me, as for the regenerative cooling that came up in the recent aircon load discussion, seems to be that I'd have to change my driving style to incorporate more engine braking, and much less coasting.

What I'd like would be a direct linkage to the transmission, but that involves too much engineering.

Edited by edlithgow on 15/07/2020 at 16:11

Any - Real Fuel Saving at Low Cost - thunderbird

Student project on a retrofit Alternator Interrupt Circuit to give old stupid alternators some fuel saving smarts.

Back in the 80's a racing friend of mine had that on his race car. It worked quite simply by somehow interrupting the output of the alternator once a user set throttle position had been reached. The theory was that although the battery was providing the power to the ignition when the alternator output was interrupted it was a low current requirement in old clockwork carburettor cars and would be easily replaced at lower revs and under braking (in other classes alternators were not required and cars would do a full race distance on battery power alone). From memory taking the alternator load off the engine was alleged to release about 5% more power and as we all know power costs money and the cost of the kit was way less than any worthwhile engine mods.

So did it work.

Not really for 2 reasons. The first was everybody fitted the kit without it you expected to be at a disadvantage thus the status quo had not been changed. The second reason was just as simple, no competitors lap time changed by a consistent amount and no driver got the reduction a 5% power increase should have given them.

As with most 1980's electronics they did not last in the harsh racing environment and I am pretty sure no competitors replaced the kit.

Any - Real Fuel Saving at Low Cost - RT

Student project on a retrofit Alternator Interrupt Circuit to give old stupid alternators some fuel saving smarts.

Back in the 80's a racing friend of mine had that on his race car. It worked quite simply by somehow interrupting the output of the alternator once a user set throttle position had been reached. The theory was that although the battery was providing the power to the ignition when the alternator output was interrupted it was a low current requirement in old clockwork carburettor cars and would be easily replaced at lower revs and under braking (in other classes alternators were not required and cars would do a full race distance on battery power alone). From memory taking the alternator load off the engine was alleged to release about 5% more power and as we all know power costs money and the cost of the kit was way less than any worthwhile engine mods.

So did it work.

Not really for 2 reasons. The first was everybody fitted the kit without it you expected to be at a disadvantage thus the status quo had not been changed. The second reason was just as simple, no competitors lap time changed by a consistent amount and no driver got the reduction a 5% power increase should have given them.

As with most 1980's electronics they did not last in the harsh racing environment and I am pretty sure no competitors replaced the kit.

Any number of cars have a "Wide Open Throttle" (WOT) switch built in to the accelerator pedal - it's what operates the "Kick Down" on automatic transmissions and often also cut out the air-conditioning and alternator charging - race cars would have routinely used something similar.

Any - Real Fuel Saving at Low Cost - thunderbird

Any number of cars have a "Wide Open Throttle" (WOT) switch built in to the accelerator pedal - it's what operates the "Kick Down" on automatic transmissions and often also cut out the air-conditioning and alternator charging - race cars would have routinely used something similar.

They may have today but I am talking about a clockwork car of the 1970's that as production was manual and never had aircon. Cars of that era only had a cable that connected the pedal to the carburettor with nothing in between. The only clever part would have been the auto choke and we all know how good they were, clever was the wrong word.

Any - Real Fuel Saving at Low Cost - RT

Any number of cars have a "Wide Open Throttle" (WOT) switch built in to the accelerator pedal - it's what operates the "Kick Down" on automatic transmissions and often also cut out the air-conditioning and alternator charging - race cars would have routinely used something similar.

They may have today but I am talking about a clockwork car of the 1970's that as production was manual and never had aircon. Cars of that era only had a cable that connected the pedal to the carburettor with nothing in between. The only clever part would have been the auto choke and we all know how good they were, clever was the wrong word.

I'm talking about 60/70 cars with automatic transmission plus later cars with aircon - a WOT switch may not be universal but it's common enough, a physical switch on the floor under the accelerator operated when the pedal is buried into the carpet.- certainly fitted on all '80s Bosch L-Jetronic fuel injection systems

Any - Real Fuel Saving at Low Cost - thunderbird

I'm talking about 60/70 cars with automatic transmission plus later cars with aircon - a WOT switch may not be universal but it's common enough, a physical switch on the floor under the accelerator operated when the pedal is buried into the carpet.- certainly fitted on all '80s Bosch L-Jetronic fuel injection systems

I cannot remember ever being in a car from the 60's and 70's with A/C and that includes Jags and Mercs. Auto's of that period had a mechanical control on the throttle cable under the bonnet for kickdown. Firat car I saw with a "button" under acelerator pedal was a colleagues Kia and the salesman and told him a press on that gave an extra 25% power. A chap in the office did not believe this but after investigation it proved correct, well partly. The button was simply a plastic "resistance" device that had no electronics or wiring. All it did was prevent you from getting more than 75% throttle unless you gave a firmer press. So if the car had 100 bhp you only got 75 bhp unless you pressed hard, very hard, it did not boost the car to 125 bhp as the salesman had suggested. Later Kia admitted it was actually an economy device to prevent owners from using too much fuel by restricting throttle.

And as you say L Jetronic came out in the 80's so hardly relevant for 60's and 70's cars. I had 2 80's cars fitted with mechanical K Jetronic, not the later KE Jetronic.

Any - Real Fuel Saving at Low Cost - RT

I'm talking about 60/70 cars with automatic transmission plus later cars with aircon - a WOT switch may not be universal but it's common enough, a physical switch on the floor under the accelerator operated when the pedal is buried into the carpet.- certainly fitted on all '80s Bosch L-Jetronic fuel injection systems

I cannot remember ever being in a car from the 60's and 70's with A/C and that includes Jags and Mercs. Auto's of that period had a mechanical control on the throttle cable under the bonnet for kickdown. Firat car I saw with a "button" under acelerator pedal was a colleagues Kia and the salesman and told him a press on that gave an extra 25% power. A chap in the office did not believe this but after investigation it proved correct, well partly. The button was simply a plastic "resistance" device that had no electronics or wiring. All it did was prevent you from getting more than 75% throttle unless you gave a firmer press. So if the car had 100 bhp you only got 75 bhp unless you pressed hard, very hard, it did not boost the car to 125 bhp as the salesman had suggested. Later Kia admitted it was actually an economy device to prevent owners from using too much fuel by restricting throttle.

And as you say L Jetronic came out in the 80's so hardly relevant for 60's and 70's cars. I had 2 80's cars fitted with mechanical K Jetronic, not the later KE Jetronic.

What's unclear about "60/70 cars with automatic transmission plus later cars with aircon" which surely makes clear that aircon refers to periods later than 60/70s.

Any - Real Fuel Saving at Low Cost - thunderbird

I'm talking about 60/70 cars with automatic transmission plus later cars with aircon - a WOT switch may not be universal but it's common enough, a physical switch on the floor under the accelerator operated when the pedal is buried into the carpet.- certainly fitted on all '80s Bosch L-Jetronic fuel injection systems

I cannot remember ever being in a car from the 60's and 70's with A/C and that includes Jags and Mercs. Auto's of that period had a mechanical control on the throttle cable under the bonnet for kickdown. Firat car I saw with a "button" under acelerator pedal was a colleagues Kia and the salesman and told him a press on that gave an extra 25% power. A chap in the office did not believe this but after investigation it proved correct, well partly. The button was simply a plastic "resistance" device that had no electronics or wiring. All it did was prevent you from getting more than 75% throttle unless you gave a firmer press. So if the car had 100 bhp you only got 75 bhp unless you pressed hard, very hard, it did not boost the car to 125 bhp as the salesman had suggested. Later Kia admitted it was actually an economy device to prevent owners from using too much fuel by restricting throttle.

And as you say L Jetronic came out in the 80's so hardly relevant for 60's and 70's cars. I had 2 80's cars fitted with mechanical K Jetronic, not the later KE Jetronic.

What's unclear about "60/70 cars with automatic transmission plus later cars with aircon" which surely makes clear that aircon refers to periods later than 60/70s.

OK I misread it.

But the fact that all the 60's 70's car I knew with auto tramsmission had the kickdown device under the bonnet on a cable (just like this one www.ebay.co.uk/itm/Jaguar-XJ6-E-Type-Mk10-Gearbox-...8) sort of confirms that autos of that period did not have a switch on the floor. Even the upmarket cars of that period were purely mechanical.

Any - Real Fuel Saving at Low Cost - Sofa Spud

If you can find a Rolls-Royce Silver Shadow or a Bentley T, look under the accelerator pedal and you'll see the kickdown switch! Those cars were introduced in 1966.

Any - Real Fuel Saving at Low Cost - edlithgow

So did it work.

Not really for 2 reasons. The first was everybody fitted the kit without it you expected to be at a disadvantage thus the status quo had not been changed. The second reason was just as simple, no competitors lap time changed by a consistent amount and no driver got the reduction a 5% power increase should have given them.

Interesting. But I'd suggest "just as simple" doesn't really apply here.

A race series is hardly a controlled experimental environment, but if the kit was deployed on a large scale over a long period maybe your conclusions are valid.

I'd wonder if power is sufficiently a limiting factor that a 5% gain would be expected to translate into consistent improvement in lap times, given all the other variables in play. I don't know it isn't, since I don't know much about racing, bit I'd be mildly surprised if it is.

Any - Real Fuel Saving at Low Cost - thunderbird

I'd wonder if power is sufficiently a limiting factor that a 5% gain would be expected to translate into consistent improvement in lap times, given all the other variables in play. I don't know it isn't, since I don't know much about racing, bit I'd be mildly surprised if it is.

For the front runners 5% should give an improvement but for inconsistent novices it would be difficult to tell. The experienced club racers who knew their cars well and probably knew the circuits better would be fast out of the paddock first thing and would be in the pits a couple of times during practice to check and adjust tyre pressures. At the time I am referring to the series was tightly controlled with almost no permitted changes (other than safety) in the lower class (to keep costs down) but more in the upper classes. 1 second could cover the top 10 in each class on the grid for the race. Any advantage you could find within the rules was tried, couple of examples. You had to have a passenger seat capable of carrying a person so it became normal to bolt the plastic bit from a cafe chair to the floor to save the weight of using the standard seat. After a couple of races it was no advantage, all were doing it. Another example which only applied in the lowest class was the rule to carry a "spare wheel". One chap thought about it and instead of carrying a "spare wheel and tyre" as intended by the rules bolted a spare steering wheel to the passenger floor of the car saving quite a bit of weight. He won but by the next race the rule had been modified to require something like a "spare wheel and tyre capable of being fitted to the vehicle".

So when a modification came along that promised 5% and would be perfectly legal in all classes there was nothing to loose (except the purchase cost) but it simply did not produce the gain a couple of hours tweaking the jetting and timing on the dyno to gain possibly 5% would do. The alternator mod should have been all gain really since unlike some carb mods would have no detrimental effect on low down performance.

Without doubt the biggest performance gain to be had was tyres despite having a controlled tyre rule in the series (think it was Uniroyal). The top racers had them shaved down to about 3 mm which produced lap time immediately and they degraded slower in a race since the block movement did not overheat them. Throwing away 5mm of tread seemed stupid to me as an onlooker but the results were clear enough (until it rained). But the top blokes had another set (still shaved) but only down to about 5mm).

Any - Real Fuel Saving at Low Cost - edlithgow

Vindication of my "Bald tyres as a safety enhancement for the Taiwan Dry Season" pitch.

But that's the kind of heresy that gets you a one-way trip to Guantanamo.

https://www.bobistheoilguy.com/forums/threads/please-maintain-your-tires-properly.296851/page-3

Any - Real Fuel Saving at Low Cost - Andrew-T

I would be interested to know how much heavier a battery gets between flat and fully charged. Of course the charge/discharge process is a reversible chemical change, but how much does it weigh ? It's not quite E=mc2 (nuclear) which would weigh almost nothing, but it can't be very much ?

Any - Real Fuel Saving at Low Cost - bathtub tom

If you externally charge up your 12 volt car battery, using say, an intelligent charger, just before making a long familiar journey, you can enjoy a significant fuel saving for the whole round trip, that will yield an indicated fuel economy similar to that achieved by HJ Real mpg readers running similarly sized but much more expensive hybrid engined cars such as the Toyota Yaris Hybrid.

I'd suggest a hybrid is no more economical on a long journey than a non-hybrid unless stop-start is encountered a lot. A hybrid could be less economical on a long cruise due to the extra weight of the hybrid battery.

I used to participate in economy runs (remember them?) back in the '70s. It would be normal to fully charge the battery beforehand, bump start the car (my drive's on a slope), drive with all the windows fully closed and not use any electrics unnecessarily. I don't know if it made any measurable difference, but it could get very hot and sweaty on sunny days!

Any - Real Fuel Saving at Low Cost - Andrew-T

<< A hybrid could be less economical on a long cruise due to the extra weight of the hybrid battery. >>

The extra weight will only have much effect during acceleration, which I suupose if done gently can be minimised. When the car reaches cruising speed all other variables should be the same on a level road if tyre pressures are correct. The extra energy needed to accelerate may be regained on the downhill, so if the journey starts and ends at the same altitude there may be little difference ?

Real life probably isn't like that though.

Any - Real Fuel Saving at Low Cost - thunderbird

The extra weight will only have much effect during acceleration, which I suupose if done gently can be minimised. When the car reaches cruising speed all other variables should be the same on a level road if tyre pressures are correct.

A heavier car will be putting that extra weight down to the road at all speeds and that extra weight will create more drag through the tyres.

But that is only one factor of course. If its 2 identical cars on the same tyres the drag factor will be identical for the hybrid/non hybrid we can discount that as a red herring (unless the hybrid has low resistance tyres).

Any - Real Fuel Saving at Low Cost - Andrew-T

<< A heavier car will be putting that extra weight down to the road at all speeds and that extra weight will create more drag through the tyres. >>

That's why suitable tyres have to be fitted, at a suitable pressure to minimise rolling resistance.

Any - Real Fuel Saving at Low Cost - thunderbird

<< A heavier car will be putting that extra weight down to the road at all speeds and that extra weight will create more drag through the tyres. >>

That's why suitable tyres have to be fitted, at a suitable pressure to minimise rolling resistance.

A bigger heavier car will indeed have tyres chosen to carry that weight which can be larger diameter, wider, higher load rating etc. No doubt the manufacturers choice takes rolling resistance into consideration but they cannot defy the laws of physics, if it heavier it takes more energy to keep it moving at a certain speed on flat on uphill roads. Obviously the weight could help downhill but its impossible to drive downhill all the time.

Any - Real Fuel Saving at Low Cost - Terry W

I can understand the attraction of a hybrid if most journeys could be completed under battery power, with the ability to ocassionally cover longer distances using petrol/diesel.

I am not sure whether most plug in hybrids have regenerative braking - otherwise every incline represents an "acceleration" with the downhill bit done on a trailing throttle. So even on a long trip on a motorway with no congestion their will be a weight/fuel penalty.

Whether the savings in fuel by using plug in recharging are sufficient to justify the additional cost and complexity is questionable. 10000 miles pa at 50mpg = 200 gallons @ £5 per gallon = £1000. Assume a saving of £700 pa (electricity is not free) it may take 5-10 years to recover the initial cost.

Any - Real Fuel Saving at Low Cost - mcb100

'I am not sure whether most plug in hybrids have regenerative braking' Yes they do.

Any - Real Fuel Saving at Low Cost - Catfood

I don’t think the sole reason of buying a hybrid is to save few £. To me, added reasons are ease of driving, paying more to appreciate an alternative technology….not those refined but boring 3/4 pots going up & down at xxxx RPM.

I'd rather pay extra £££££ and enjoy the benefit of having the latest technology than thinking about saving/recover £££ for next x number of years......

Any - Real Fuel Saving at Low Cost - thunderbird

We really wanted to like the Corolla Estate and the 2 litre was an excellent drive with the rev increase of old well controlled. For us its immediate downfall was the pain in the right foot that both me and the Mrs got whilst driving it, found other references on the web as well.

Decided to give it another chance this week and booked a test in a 1.8 and a 2 litre (at a different dealer) in an attempt to get more time in the cars and check the pedal for comfort. But the dealer cancelled at the last minute saying that his boss had taken one car on holiday and they had sold the other.

They must be doing well if they can afford to potentially turn customers away.

Any - Real Fuel Saving at Low Cost - alan1302

They must be doing well if they can afford to potentially turn customers away.

They are - Toyota had it's best June of all time in the UK this year...there was a thread on it a few days ago...you did post in that thread as well!

Any - Real Fuel Saving at Low Cost - madf

I don’t think the sole reason of buying a hybrid is to save few £. To me, added reasons are ease of driving, paying more to appreciate an alternative technology….not those refined but boring 3/4 pots going up & down at xxxx RPM.

I'd rather pay extra £££££ and enjoy the benefit of having the latest technology than thinking about saving/recover £££ for next x number of years......

A car is just a means of transport.

Being an early adopter of new tech means you pay over teh odds for a soon to be outdated product.

Thinks PCs and mobile phones.

Cars are just white goods..but bigger and more expensive..And require regular expenditure to keep going..

Any - Real Fuel Saving at Low Cost - Catfood

Toyota Hybrid, for example, is on the market since 1997. It's not hardly a new technology....

Any - Real Fuel Saving at Low Cost - Engineer Andy

I don’t think the sole reason of buying a hybrid is to save few £. To me, added reasons are ease of driving, paying more to appreciate an alternative technology….not those refined but boring 3/4 pots going up & down at xxxx RPM.

I'd rather pay extra £££££ and enjoy the benefit of having the latest technology than thinking about saving/recover £££ for next x number of years......

A car is just a means of transport.

Being an early adopter of new tech means you pay over teh odds for a soon to be outdated product.

Thinks PCs and mobile phones.

Cars are just white goods..but bigger and more expensive..And require regular expenditure to keep going..

I still use (because it has free voicemail for life on Virgin mobile) my 'ancient' Nokia 3410 phone to pick up messages when my new-er Lumia 620 is on PAYG and costs quite a bit to check messages.

The other benefit being (unlike the newer phone, which locks up occasionally [design flaw], needing the battery to be removed to reboot it) proven tech (not one problem in 17 years and hardy too, especially in its leather protective case), and, in standby mode, a very long battery life. Still going since 2003.

Like my 14yo car, I don't stop using things or throw them away unless they break (and cannot be economically repaired), my needs change enough to justify a change or I'm really flush with cash (not at the mo).

Just had to change tha car's battery again (5 years life this time) - now on No. 4 (including the original) from new. Dead easy to get all the settings for the ICE back - less than 5 minutes...and no code needed either!

Any - Real Fuel Saving at Low Cost - bathtub tom

I'd rather pay extra £££££ and enjoy the benefit of having the latest technology than thinking about saving/recover £££ for next x number of years......

I'd rather have the older, boring technology that's been proven than the new untested stuff.

Any - Real Fuel Saving at Low Cost - Ethan Edwards

Regarding the OP's suggestion of constantly charging the battery to gain a reduction in fuel usage. I'm not going to comment on how effective that might be. I'm just noting your home electricity bill won't thank you. And relate to you the story of my late dear old dad. He was from the time of cars with dynamos and so we owned a charger. Towards the end of his life he had Alzeheimers. Before the diagnoses he had some odd behaviour going on. He had a Rover 214 or 216 can't recall. Anyway it had a Alternator. Nice reliable little car. Got him out and about. He was always charging the battery. Now I can't tell you the exact number but he ruined many batteries and an alternator. Eventually the car died. I suggest this cost much more than any putative fuel savings.

Any - Real Fuel Saving at Low Cost - Catfood

Don't get me wrong. I do like the "proven" new technology. I'm not keen on untested, guarenteed to break techno gizzmo offered by some German brands....

Any - Real Fuel Saving at Low Cost - thunderbird

He was always charging the battery. Now I can't tell you the exact number but he ruined many batteries and an alternator.

If he was charging it on the car with an old school charger that was not compatible with modern battery's it would potentially cause damage. Charging with the correct kit should be fine.

Any - Real Fuel Saving at Low Cost - edlithgow

He was always charging the battery. Now I can't tell you the exact number but he ruined many batteries and an alternator.

If he was charging it on the car with an old school charger that was not compatible with modern battery's it would potentially cause damage. Charging with the correct kit should be fine.

My understanding is/was that in-car charging in use didn't get the battery to full charge (or did so rather slowly) and that an occaisional external charge offline promoted longer battery life.

As with many, even most, automotive stories, this, if it was ever true, might be invalidated by a shift in the technology applied to current cars.

I cant really date the origin of the story without doing some historical poking about, but I/m pretty sure it post-dates the alternator.

BTAIM, probably a bad idea to externally charge a current (or even this century) cars battrery without disconnecting it from the car, and then you'd probably need a backup battery to keep its computers online.

Probably OK with mine. Hope so anyway, because I've been doing it for years.

Maybe I've been getting a tiny fuel saving benefit too.

Re ""Your electricity bill won't thank you""the impact on even my very low domestic electricity consumption is going to be similarly undetectable.

Edited by edlithgow on 18/07/2020 at 05:38

Any - Real Fuel Saving at Low Cost - Firmbutfair

Thanks for such a lively debate, ladies and gentlemen. My 5 door family hatchback car, has performed faultlessly since purchasing it from new and these savings have been carefully recorded over 26,000 miles spead over 42 months with the first battery charging only being introduced when the car was over 2 years old in May 2019. Thus it was fully 'run in' when the modified maintenance process was introduced and I have 26 months of regular driving to use as a firm basis for my modified battery maintenance/fuel economy comparisons.

The observation that a fully charged battery is essential to achieve the best overall fuel economy is borne out by the comments about Mobil Economy Runs and the like, from bath tub tom and others, plus the fact that when prototype models are submitted for WLTP fuel economy and emissions testing, the car battery is always fully charged before the test to minimise and significantly reduce normal alternator 'drag' on the engine during the testing.

Indeed it is not unheard of for the manufacturer to build in engine management software to detect when the car is beng driven gently, such as when under WLTP test and modify its 'mapping' and control systems characteristics accordingly to give the most favorable test results!

So its is all there for the taking folks. Drive it like its under the WLTP test and you might just get the fuel economy recorded and published under the WLTP regulations! Alternatively, drive it like you just stole it and it will come nowhere near those figures. As they say on Star Trek - "You can't change the Laws of Physics" . Just saying.

Edited by Firmbutfair on 04/09/2020 at 18:49

Any - Real Fuel Saving at Low Cost - Engineer Andy

If you drive a (standard) car reasonably smoothly and don't labour the engine, and plan ahead for both routes and whilst driving to reduce stopping/starting, you can get close or even better than the quoted mpg. I've maneged to get 40-41 mpg average over the 15 years I've owned my Mazda3, and yet the published mpg for the car was (not the makeove one that had a re-mapped engine with better mpg and less performance) was 38.5.

With my mid 90s Nissan Micra, the official combined mpg was 47, I achieved 52-53 on mixed driving over nearly 8 years of ownership. And I'm not Captain Slow either (though not a speed merchant).

Any - Real Fuel Saving at Low Cost - misar

The OP is more or less correct on theory but totally wrong on the magnitude of any possible fuel saving.

As he and many others have said repeatedly in this thread, by far the largest effect on economy for a given car is how it is driven. I don't doubt he is accurately reporting his test figures but a small, subconscious change in his driving style almost certainly accounts for most, if not all, the fuel saving he is claiming.

Any - Real Fuel Saving at Low Cost - Big John

Another thing to consider - On a modern car with stop/start/regenerative braking the car will have an advanced charging control system, which can be confused if the battery is charged from another source.

I've known a few people have issues of this post lockdown when old battery chargers have been pulled out of the shed etc - some requiring a trip to the dealer to sort!

Edited by Big John on 04/09/2020 at 21:13

 

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