Granny charger

[cryo]

This is all very strange it appears form what I can read in this thread that 7KW systems appear unable to suffer from bad/warm contacts but the scare mongers or is that installers and car salesmen based solely on commission/profit return are quick to point out potential problems with 3 pin sockets? There are thousands of property's throughout the UK that have 2KW oil filled and resistive heaters plugged in for warmth with minimum to no problems from extended use. Modern washer driers can have a 7 hour high load wash dry cycle yet I do not see the government warning about these?? Yes there is a potential to overload old wiring but the same potential applies to any high load item whether it be an old three pin plug or a new 7.5KW installation, and yes new installations do fail. Unfortunately the EV charging market is seen as the new double glazing money making con starting with car salesmen striking the fear of god into prospective buyers based solely on commission earned from EV installation recommendations and this has now lead to a perceived/generic risk of using so called granny chargers. Where there is money to be made from the unsuspecting general public the con men will quickly latch on and move in, ask yourself who invented the name granny charger and why?? Just for interest before I retired I was a fully trained (4 year apprenticeship) industrial electrician and I have worked on many older private properties with far safer wiring than the 8 week dolls houses that are being thrown up today with a total disregard to safety or quality of installation. Please do not refer to this with there are checks because site inspectors rarely get further than the site manager office (fact) Ask yourself if this so called potential immediate inherent danger had more than slightest risk would the Tesla and many other manufacturers 3 pin systems have been allowed to be sold with the car?

 

[init6]

This is all very strange it appears form what I can read in this thread that 7KW systems appear unable to suffer from bad/warm contacts but the scare mongers or is that installers and car salesmen based solely on commission/profit return are quick to point out potential problems with 3 pin sockets? There are thousands of property's throughout the UK that have 2KW oil filled and resistive heaters plugged in for warmth with minimum to no problems from extended use. Modern washer driers can have a 7 hour high load wash dry cycle yet I do not see the government warning about these?? Yes there is a potential to overload old wiring but the same potential applies to any high load item whether it be an old three pin plug or a new 7.5KW installation, and yes new installations do fail. Unfortunately the EV charging market is seen as the new double glazing money making con starting with car salesmen striking the fear of god into prospective buyers based solely on commission earned from EV installation recommendations and this has now lead to a perceived/generic risk of using so called granny chargers. Where there is money to be made from the unsuspecting general public the con men will quickly latch on and move in, ask yourself who invented the name granny charger and why?? Just for interest before I retired I was a fully trained (4 year apprenticeship) industrial electrician and I have worked on many older private properties with far safer wiring than the 8 week dolls houses that are being thrown up today with a total disregard to safety or quality of installation. Please do not refer to this with there are checks because site inspectors rarely get further than the site manager office (fact) Ask yourself if this so called potential immediate inherent danger had more than slightest risk would the Tesla and many other manufacturers 3 pin systems have been allowed to be sold with the car?

I'm not disagreeing with the thrust of your argument, but comparing a constant 7kW load with a constant 2kW load or an intermittent 'high' load is not doing your argument any favours.

 

[Avendit]

Hi I’ve been using a granny charger for over a year and it works for me.

However before on the app it use to charge between 2kw and 3 kw.

I noticed it would flicker between 2kw and 3kw. I’m pretty use it use it charge faster over night.

Now it’s always at 2kw. Nothing has changed any ideas how I can squeeze a little bit more out of it?

Does it matter if the granny cable is rolled up?

Just to short circuit the rants that are coming through... Lots of thought about the granny charger and using it on the forum already, but probably one of 2 things happening here:
1) your voltage has dropped slightly so now its rounding to 2kw. My full charger delivers a reported '8kw' over night as the voltage goes up with less load on the grid, which is at 240+v, rather than the nominal 230v that we get in the day where "7kw" is reported.
2) Your 13A socket is getting tired of the abuse you are subjecting it to . Yes its rated to 13A, and you are using it at 10A, but you are using it waaaay harder than any other 13A socket in the house. Heaters are on thermostats and click on and off. Hair dryers and kettles are only on for a few minutes at a time. Using the granny charger you are pulling 10A for up to 48hr a time. I've had the thermal trip go on my UMC in all the garage sockets in my parents house (resistance goes up, voltage goes down, UMC cuts the power for 15 minutes to let it cool down then tries again). Something screwy in the wiring there, or lack of use in a very exposed location has got to them - the outdoor ones are fine weirdly)

The contact points on the 13A sockets aren't massive, so if you can't definitely track your change to a lower voltage, possibly check in case the plug/socket has started warming up more than it used to. It should be at about 20-25 deg C, any hotter and you have the start of the problem. Turning it off and pulling the plug in and out a few times will probably re-seat everything for another year TBH. Or swap to the other socket in the double and see how that works. Not much else in the way of options in a rented accommodation if the landlord is a git.

 

[GlynG]

I'm not disagreeing with the thrust of your argument, but comparing a constant 7kW load with a constant 2kW load or an intermittent 'high' load is not doing your argument any favours.

I'm not sure what you are saying here. Cryo's comments as i understand them is critical of the opportunists that do their best to get all EV owners to have a dedicated 7Kw charger rather than use the Granny charger with statements that allude towards a safety issue using the granny charger for anything more than occasional use. They imply that the dedicated chargers couldn't possibly have any safety issues develop from frequent use whereas the granny is a bit suspect.

Cryo's comments make absolute sense to me and bear in mind this fellow was a professional electrician.

 

[init6]

I'm not sure what you are saying here.

Read it again. If the loads are of no import, why mention them? If the loads are important then comparing different loads is not helpful.

 

[cryo]

I'm not disagreeing with the thrust of your argument, but comparing a constant 7kW load with a constant 2kW load or an intermittent 'high' load is not doing your argument any favours.

A bad joint is exactly as described and the whether it is on a 7KW system or a 2KW system irrespective of the power and will have exactly the same result. I cannot see the wording intermittent 'high' load used anywhere in my statement? Just to note I'm not arguing it is obviously a fact that the EV charging scenario is seen as a money maker and the public are in many cases being mislead/lied to and fleeced.

 

[init6]

modern washer driers can have a 7 hour high load wash dry cycle

These do not have the 'high load' on all throughout the cycle.

 

[init6]

A bad joint is exactly as described and the whether it is on a 7KW system or a 2KW system irrespective of the power and will have exactly the same result.

You will generate more heat with a higher current:

When current flows through a conductor, heat energy is generated in the conductor. The heating effect of an electric current depends on three factors:

• The resistance, R of the conductor. A higher resistance produces more heat.
• The time, t for which current flows. The longer the time the larger the amount of heat produced
• The amount of current, I. the higher the current the larger the amount of heat generated.

 

[Regulo]

Don't know if it's relevant, but I used the supplied "granny" charger with my Mitsubishi Outlander Phev for 7 years with no problems whatsoever. 10 Amps max current - about 2.5kW. If the charger supplied with any EV isn't to be used to charge the car, then surely the whole package would be considered not fit for purpose under consumer law? Household wiring is a different matter, of course. If your wiring is safe, I don't see a problem in solely using the Tesla charger.

 

[Undecided_2]

Granny charger is perfectly acceptable as long as you have good modern wiring. Been using for over 2 years with no issue albeit without any extension cable.

If you do need an extension use a heavy duty one rated for continuous 10amp draw.

Living in a rental property where I’m already paying the landlords mortgage I’m not paying for them to have a 7KW charger. 3 pin is sufficient.

My friend has used the granny charger for 5-years with no issues and his battery degradation is excellent. Gently charging is good for the battery.

We’re having a dedicated charger fitted and the electricians said that charging via a plug is fine as long as the wiring in the home is good but having a dedicated charger is a better long term solution but isn’t perfect - they pointed out that super chargers have issues and need fixing. These guys have been around a long time and if they say it’s not without potential issues then I believe them.

 

[GlynG]

Just to short circuit the rants that are coming through... Lots of thought about the granny charger and using it on the forum already, but probably one of 2 things happening here:
1) your voltage has dropped slightly so now its rounding to 2kw. My full charger delivers a reported '8kw' over night as the voltage goes up with less load on the grid, which is at 240+v, rather than the nominal 230v that we get in the day where "7kw" is reported.
2) Your 13A socket is getting tired of the abuse you are subjecting it to . Yes its rated to 13A, and you are using it at 10A, but you are using it waaaay harder than any other 13A socket in the house. Heaters are on thermostats and click on and off. Hair dryers and kettles are only on for a few minutes at a time. Using the granny charger you are pulling 10A for up to 48hr a time. I've had the thermal trip go on my UMC in all the garage sockets in my parents house (resistance goes up, voltage goes down, UMC cuts the power for 15 minutes to let it cool down then tries again). Something screwy in the wiring there, or lack of use in a very exposed location has got to them - the outdoor ones are fine weirdly)

The contact points on the 13A sockets aren't massive, so if you can't definitely track your change to a lower voltage, possibly check in case the plug/socket has started warming up more than it used to. It should be at about 20-25 deg C, any hotter and you have the start of the problem. Turning it off and pulling the plug in and out a few times will probably re-seat everything for another year TBH. Or swap to the other socket in the double and see how that works. Not much else in the way of options in a rented accommodation if the landlord is a git.

I do see a lot of sense in your comments, however, I don't believe anyone that needs to have the granny plugged in frequently for a 48 hour charge would consider the granny charger appropriate for their needs, The majority of granny charger users are likely to be those that do small mileages and therefore would have little benefit from having a charger capable of fully charging the car within a few hours, the scenario for me is I'm retired and keep the car around 90% all the time - If i use the car its usually for less than 50 miles at a time - so plugging in even with the granny is just 5 hours to be back at 90% - there wouldn't be a benefit to me if i could charge it back up to 90% in less than a couple of hours and i believe there are many owners just like me.

 

[WannabeOwner]

I don't believe anyone that needs to have the granny plugged in frequently for a 48 hour charge would consider the granny charger appropriate for their needs

Might well be £1,000 for a wall charger, more if the fuse board is a long way from the car location and/or cable routing is tricky - I suspect that will put some people off. There's a tesla in the village always plugged in on Granny cable. Brand new house, so I expect the wiring is fine, but if they come home empty its going to be a couple of days until car is charged again and the socket will be "flat out" for that time. 13AMP is around 5 MPH ... 240 miles range top up would be 48 hours

I've charged on friends' garage sockets and had to stop once I found they got red hot!! probably some "supplemental wiring" that was bodged at some point. Homeowner never realised 'coz they only ever plugged a drill or cordless garden device battery into that socket.

I've also tripped all the circuits in friends' houses plugging car into a 13AMP socket. Turning all their circuits off and back on one-by-one narrowed the culprit, such as a freezer; I assume some slight leakage on that device or socket.

My view is that Granny Charger is fine ... provided that the circuit is in good nick. But even then, if the circuit isn't designed for long duration high current draw will there be accelerated wear-and-tear on the contacts or similar? something that a dedicated wall charger avoids because it is intentionally more robust.

 

[Undecided_2]

My wife and I work from home and we were surprised that 43% SOC was more than enough for 70 miles travel in heavy traffic and with cold, windy weather and still left us with 26% SOC when we got home. We have a Tesla charger but clearly we don’t need to worry about having a high SOC for daily use.

 

[WannabeOwner]

clearly we don’t need to worry about having a high SOC for daily

FWIW ...

I charge immediately (not wait for overnight cheap rate) if I return home below 20% (might have to go out again ... and better for battery to not leave it at low SOC)

Similarly I only charge above 90% shortly before heading off on a trip - although i don't sweat that if it sits at 100% for a few hours; for me a going-on-a-trip 100% charge is not very often

 

[Undecided_2]

FWIW ...

I charge immediately (not wait for overnight cheap rate) if I return home below 20% (might have to go out again ... and better for battery to not leave it at low SOC)

I’ve been following a separate feed here about battery degradation and high SOC v low SOC. I think I’ll maintain it around 50-60% as that’s more than enough to get us to the first Tesla super charger if we need to head south - Scotland > England in an emergency.

 

[WannabeOwner]

I think I’ll maintain it around 50-60%

I've given up even thinking about it - except not leaving the battery very low, nor very high, for prolonged periods.

Did 100K miles in the first Tesla - that had the 90 battery which was probably one of the least-good-chemistry ones, and bought that 6 years ago. That lost 6% degradation ... and I reckon current battery chemistry is far more durable.

Current Nov-2019 car has 0.7% gain ... at 20K miles (did 10K miles over 4 months until end Feb-2020 and the other 10K since then)

I'd prefer to have the car well charged and be able to go somewhere if I need to.

 

[cryo]

You will generate more heat with a higher current:

Yes I do not disagree with this statement but bear in mind lower power systems can only be supplied with a limited amount of power/current so everything is proportional, its how electrical systems are designed.

 

[GeorgeSymonds]

The UMC shouldn't have a problem on a 3 pin plug - its rated for 32A so 10A will not create any great heat build up that it can't cope with.

Your domestic wiring and sockets are an unknown quantity and quality. Regs change over the years, old houses may have old forms of cabling and houses do get rewired from time to time for a reason.

Like all things, a little common sense goes a long way.

For those who want to see what Tesla actually say about the use, the UMC2 instruction manual is here:

https://www.tesla.com/sites/default/files/pdfs/charging_docs/gen_2_umc/Gen2_Mobile_Connector_en_EU.pdf

 

[cryo]

Might well be £1,000 for a wall charger, more if the fuse board is a long way from the car location and/or cable routing is tricky - I suspect that will put some people off. There's a tesla in the village always plugged in on Granny cable. Brand new house, so I expect the wiring is fine, but if they come home empty its going to be a couple of days until car is charged again and the socket will be "flat out" for that time. 13AMP is around 5 MPH ... 240 miles range top up would be 48 hours

I've charged on friends' garage sockets and had to stop once I found they got red hot!! probably some "supplemental wiring" that was bodged at some point. Homeowner never realised 'coz they only ever plugged a drill or cordless garden device battery into that socket.

I've also tripped all the circuits in friends' houses plugging car into a 13AMP socket. Turning all their circuits off and back on one-by-one narrowed the culprit, such as a freezer; I assume some slight leakage on that device or socket.

My view is that Granny Charger is fine ... provided that the circuit is in good nick. But even then, if the circuit isn't designed for long duration high current draw will there be accelerated wear-and-tear on the contacts or similar? something that a dedicated wall charger avoids because it is intentionally more robust.

I keep seeing this 5MPH stated on a 3 pin charger its 11MPH according to Tesla. Tesla app and Teslab app always state my car gains 44 miles added on my 4 hour octopus go overnight charges after AC losses. I use a three pin socket on an electronic timer with no problems but agree older or poorly installed electrics could cause problems. Its horses for courses I'm retired and use the lower powered charging but I have 4*50KW chargers within less than two miles if I need a quick charge and if heading west I can use the Scotts Corner charger (25 miles) if needed.

 

[MrBadger]

I'd find another electrician if I were you...

They probably moved on to installing cladding and fire breaks.