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Discussion Starter · #1 ·
At the risk of creating a thread which effectively replicates one already in existence - or a you tube video which covers this topic - this thread segues from Parkwood's post at the bottom of page 1 of the Trip Data thread.

I don't believe Mercedes me Eco Coach is available in Australia and I'm not sure what information it provides in any case.

I am mainly interested in better understanding how to use the energy stored in the high voltage battery economically, without going to extremes - such as turning the air conditioning off, irrespective of the weather conditions. Having said that, I typically drive with the Consumption graphic displayed in MBUX and I am somewhat alarmed at the energy consumed by non-driving functions, especially early in a journey.

If I recall correctly, Parkwood posted in another thread that one way to reduce depletion of the high energy battery is to prepare the car for travel whilst charging the battery. I understand the objective, but that's not always convenient and I assume the same amount of energy is being consumed in that scenario as would be the case if the car were prepared for travel using the on-board battery alone.

First question: is any less energy consumed if the car is 'prepared for travel' prior to commencing a journey than if one simply drives off from 'cold'?

The aspect of energy consumption of possibly greatest interest to me is the selection of driving mode. To date (I've owned my EQA for about 10 weeks / 1,000 km), I've mainly used the Individual setting in default, apart from Sport suspension setting. I don't imagine the suspension setting affects energy consumption. I then typically select D- and I invariably use the speed limiter. Most of my driving is in urban areas at up to 60 kph, with occasional journeys allowing speeds up to 80 or 110 kph.

Second question: I enjoy the (almost) one pedal experience of driving in D-, but I do wonder about its effect on energy consumption. I note that when I activate regenerative braking, I perceive, initially at least, what feels like a slight dragging effect, so I'm not sure whether say driving on flat ground without the need to slow down is less energy efficient in D- than say D, D Auto or D+. Logic suggests to me that if you need to slow down, regenerative braking is an energy efficient way to do so because, depending on the level of motor braking (dictated by throttle position), energy consumed in acceleration is, to some extent, recuperated through the regenerative system. I contrast that with driving without regenerative braking (using the brakes to slow the car) where I assume the energy dissipated through the braking system is simply lost. Assuming one enjoys the regenerative braking experience, is that therefore the most efficient in terms of energy usage? (Noting the comments of D Auto advocates, I have tried D Auto, but in low speed urban situations I haven't noticed any difference to just plain D.)

Third question: as mentioned, I invariably use the speed limiter, but I'm not sure whether, once one reaches the set speed limit, braking is primarily effected via regenerative braking or whether the brakes are also (automatically) activated.

Fourth question: is the 12 volt battery effectively on continual charge from the high voltage battery?

There are, no doubt, many other scenarios within this general theme; perhaps they will emerge through further discussion.

Alternatively, if contributors feel this topic has been covered elsewhere within the MBEQ Club, I'm happy to be directed to that, as, I suspect, may anyone else interested in this subject.
 

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At the risk of creating a thread which effectively replicates one already in existence - or a you tube video which covers this topic - this thread segues from Parkwood's post at the bottom of page 1 of the Trip Data thread.

I don't believe Mercedes me Eco Coach is available in Australia and I'm not sure what information it provides in any case.

I am mainly interested in better understanding how to use the energy stored in the high voltage battery economically, without going to extremes - such as turning the air conditioning off, irrespective of the weather conditions. Having said that, I typically drive with the Consumption graphic displayed in MBUX and I am somewhat alarmed at the energy consumed by non-driving functions, especially early in a journey.

If I recall correctly, Parkwood posted in another thread that one way to reduce depletion of the high energy battery is to prepare the car for travel whilst charging the battery. I understand the objective, but that's not always convenient and I assume the same amount of energy is being consumed in that scenario as would be the case if the car were prepared for travel using the on-board battery alone.

First question: is any less energy consumed if the car is 'prepared for travel' prior to commencing a journey than if one simply drives off from 'cold'?

The aspect of energy consumption of possibly greatest interest to me is the selection of driving mode. To date (I've owned my EQA for about 10 weeks / 1,000 km), I've mainly used the Individual setting in default, apart from Sport suspension setting. I don't imagine the suspension setting affects energy consumption. I then typically select D- and I invariably use the speed limiter. Most of my driving is in urban areas at up to 60 kph, with occasional journeys allowing speeds up to 80 or 110 kph.

Second question: I enjoy the (almost) one pedal experience of driving in D-, but I do wonder about its effect on energy consumption. I note that when I activate regenerative braking, I perceive, initially at least, what feels like a slight dragging effect, so I'm not sure whether say driving on flat ground without the need to slow down is less energy efficient in D- than say D, D Auto or D+. Logic suggests to me that if you need to slow down, regenerative braking is an energy efficient way to do so because, depending on the level of motor braking (dictated by throttle position), energy consumed in acceleration is, to some extent, recuperated through the regenerative system. I contrast that with driving without regenerative braking (using the brakes to slow the car) where I assume the energy dissipated through the braking system is simply lost. Assuming one enjoys the regenerative braking experience, is that therefore the most efficient in terms of energy usage? (Noting the comments of D Auto advocates, I have tried D Auto, but in low speed urban situations I haven't noticed any difference to just plain D.)

Third question: as mentioned, I invariably use the speed limiter, but I'm not sure whether, once one reaches the set speed limit, braking is primarily effected via regenerative braking or whether the brakes are also (automatically) activated.

Fourth question: is the 12 volt battery effectively on continual charge from the high voltage battery?

There are, no doubt, many other scenarios within this general theme; perhaps they will emerge through further discussion.

Alternatively, if contributors feel this topic has been covered elsewhere within the MBEQ Club, I'm happy to be directed to that, as, I suspect, may anyone else interested in this subject.
The Eco Coach app gives some interesting info on Mercedes’ ideas on driving style and battery preservation but is no use for when you’re driving.
I have found quite a significant difference in battery energy used by “preparing for travel “ compared to driving from cold, especially in colder temperatures, the effect is almost like a petrol engine needing choke until it warms up, not performance wise, but in terms of fuel consumption. There‘s data available somewhere that shows traction batteries perform best at certain temperatures and by preconditioning your battery it is at a better temperature when you set off. By using your charge point while preconditioning you are not drawing power from your battery to raise battery temperature.
The best display to use in the car to see the effects of driving styles is this consumption dial:
Speedometer Gauge Steering part Automotive design Car

The outer green band in combination with the bottom blue power band shows immediately any change in efficiency. Try for example travelling in D+ up a slight steady gradient keeping the accelerator pedal at the same position and changing to D-, you will see exactly what happens to efficiency.
You will be able to see on the “EQ” “energy flow” display what effect braking has on regeneration while using the speed limiter, I’ve not used the limiter but I think it won’t have any effect on braking merely affecting max speed. It’s interesting to see that applying the brakes produces regeneration even if using D+.
The 12v battery is getting charged by the traction battery whenever the car is switched on.
 

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My thoughts are uneducated and incomplete on most of these queries, but I'll add my 2c.

Q1 - I've only prepared the car a few times prior to setting off. Does it really prepare battery temperature in addition to cabin temperature? I don't know. If it's only cabin temperature being prepared, it may use a little more total energy as the cabin is being heated/cooled for a slightly longer period. However the car's recorded energy consumption (energy from the HV battery) should be a little less, making the car's stats look better overall.

Q2 - I was of the understanding that regenerative braking is always being undertaken when slowing down, either via D- or D--, or using the brake pedal, or even braking from a D+ situation. The only times regenerative braking is not used is the last bit of final stopping distance from slow speed to standstill, or under heavy/emergency braking situations where the decelleration is too much for the regenerative braking to handle.

I think that smooth use of D- or D-- would achieve much the same efficiency as D or D auto. However sudden changes in speed may cause inefficient regeneration leading to higher overall energy consumption.

Q3 - as above, regenerative braking used in most situations.

Q4 - I'll defer to FDRs answer, above, for this one. Which leads to another question. What are the major loads drawing power from the 12V battery?

I sometimes keep an eye on power draw when waiting at traffic lights. It's interesting to see the variation.
  1. Basic power consumption at standstill seems to be around 0.3kWh/h
  2. Use of seat heaters can increase this to 0.5kWh/h
  3. When the heat pump is first turned on consumption is around 1.5kWh/h
  4. Once the cabin temperature has stabilised, standing consumption drops below 1kWh/h
The units of measure seem a little strange. kWh/h should really be expressed as kW.
 

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My thoughts are uneducated and incomplete on most of these queries, but I'll add my 2c.

Q1 - I've only prepared the car a few times prior to setting off. Does it really prepare battery temperature in addition to cabin temperature? I don't know. If it's only cabin temperature being prepared, it may use a little more total energy as the cabin is being heated/cooled for a slightly longer period. However the car's recorded energy consumption (energy from the HV battery) should be a little less, making the car's stats look better overall.

Q2 - I was of the understanding that regenerative braking is always being undertaken when slowing down, either via D- or D--, or using the brake pedal, or even braking from a D+ situation. The only times regenerative braking is not used is the last bit of final stopping distance from slow speed to standstill, or under heavy/emergency braking situations where the decelleration is too much for the regenerative braking to handle.

I think that smooth use of D- or D-- would achieve much the same efficiency as D or D auto. However sudden changes in speed may cause inefficient regeneration leading to higher overall energy consumption.

Q3 - as above, regenerative braking used in most situations.

Q4 - I'll defer to FDRs answer, above, for this one. Which leads to another question. What are the major loads drawing power from the 12V battery?

I sometimes keep an eye on power draw when waiting at traffic lights. It's interesting to see the variation.
  1. Basic power consumption at standstill seems to be around 0.3kWh/h
  2. Use of seat heaters can increase this to 0.5kWh/h
  3. When the heat pump is first turned on consumption is around 1.5kWh/h
  4. Once the cabin temperature has stabilised, standing consumption drops below 1kWh/h
The units of measure seem a little strange. kWh/h should really be expressed as kW.
Without the means to show battery temperature, I am like you, I really don’t know if preconditioning without the use of the charge point prepares the battery temperature, (also I’ve never preconditioned off the charge point) it may not as it most likely uses the cabin temperature setting as a switch although it does keep the conditioning going for about 10 minutes after a preset departure time when presumably the cabin has reached its temperature. No doubt there’s a small increase in temperature caused by even a small draw from any battery, charging at the same time will definitely help.
I have found it difficult to draw definitive answers as to which D setting is best, or even if it is better to use D- downhill and D+ uphill, as it would need the same distance to be covered at the same speed and the same temperature using the different D settings. We get quite a range of temperatures here from day to day and temperature has a huge effect on the efficiency of the car. I think D auto should be best but I’ve not seen big differences on short journeys, I do tend to only use it out of town as it is a bit unpredictable in traffic, sometimes it will freewheel almost into the back of a stationary queue of traffic and next time it slows to a halt well before the queue.
As the car has all the same auxiliaries (lights, aircon, radio, door locking,cabin fan, theft alarm etc) as an ICE car running off the 12volt battery the extra loads would be those specific to EVs eg engaging the traction battery contacts, battery heat/cooling pump (although this pump can continue to run for a while after switching the car off, according to my 12v monitor the transaction battery is still providing power to the 12v during this time). There can be a draw if the car is unlocked then time spent loading luggage for example as unlocking the car starts some systems. The main problem I have had with the 12v (hence the monitor) getting low on charge is the amount of short journeys I do means the main battery is not on long enough to put back the charge lost on startup and while sitting for periods running the alarm and dashcam.
 

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Discussion Starter · #6 ·
More interesting insights.

TOUcharging, I too have wondered about units of measure. I Googled kWh and Which Car?'s 'definition' is as follows: "The total battery capacity of an EV is measured in kilowatt-hours (kWh or kW-h). This rating tells you how much electricity can be stored in the battery pack. It's a unit of energy just like calories and one kWh is equal to 3600 kilojoules (or 3.6 megajoules). Unlike kW, it is not a unit of power." I realise that kWh is fundamental to the EV world, but that's not an intuitive concept for me, so I'll have to work on it!

FDR, which 12 volt battery monitor do you use? I have fitted a CTEK Battery Sense monitor to my wife's 2016 B250 and I find it very useful, especially as the battery is the original and is now losing some performance, plus, it's not helped by mainly short journeys. One simple measure of charge in the B250 is to leave the idle stop/start (which we hate!) switched on: if the engine stops, say at traffic lights, the battery charge is acceptable, but if the engine keeps running, it probably needs a charge.
 

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Third question: as mentioned, I invariably use the speed limiter, but I'm not sure whether, once one reaches the set speed limit, braking is primarily effected via regenerative braking or whether the brakes are also (automatically) activated.
At least in the EQC, when the computer is in charge of slowing the car down - either because of the speed limiter or the adaptive cruise, it uses re-gen braking (sometimes quite aggressively). I don't think I've ever heard it use the actual brakes except for the final bring-to-a-halt right at the end of a full stop. It does that regardless of the paddle settings. The paddle settings only influence what happens when you lift your right foot off.

There's a chance the EQA may behave differently - a recent post claimed they removed D-- from the EQA because the smaller battery couldn't cope with the high re-gen power. By far the easiest way to determine what's going on in any specific set of conditions is to configure the right hand dial of the instrument cluster to be a Power meter.

Fourth question: is the 12 volt battery effectively on continual charge from the high voltage battery?
It's being charged whenever the high voltage battery contactors are on, which includes:

.when the car is "READY" (i.e. started)
.when the car is being charged
.when the pre-entry climate system is active

By far the biggest load on the 12V system is the 12V battery itself. Lead acids self-discharge, then add in all the overnight background loads and leave the car unused for a few days and that thing can need some topping up. You'll notice that on short-runs first thing in the morning (especially if the car hasn't been used or charged in a while).. the percentage that goes into the 12V system can become pretty significant... that's it dumping energy back into the lead acid battery. Compare that to a run immediately after you've charged the car. In that case you'll see very little go into the 12V system because the 12V battery was charged before you left home. In either case after a 2 or 3 hour run, I usually see both the aircon and the 12V system have settled down to about 4% each.... and that's with the aircon set to 22C and the seat chillers on (or seat warmers these days).
 

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Discussion Starter · #9 ·
Thanks for both posts, dBC.

I note the Jaycar 12v battery monitor. There's a Jaycar store near us. The EQA 12v battery has a conventional bolt-tightened clamp on the negative terminal, but the only readily visible positive terminal is a charging plate with a red sliding plastic cover (i.e. nothing much to attach the monitor's positive terminal to).

Is the EQC setup similar and if so, can you please explain where you installed your 12v monitor.

I note the dire warnings about electrocution in the Owner's Manual, so I'm keen to avoid sources of high voltage/current - also upsetting any part of the electrical system. I'm not sure whether it's part marketing, or the genuine risk of getting 12v battery replacement wrong, but the Owner's Manual provides no direction in that regard other than involving the dealer.
 

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I borrowed the battery monitor from my camping rig (different vehicle), cut off the positive terminal and replaced it with a small alligator clip which went onto that plate under the sliding cover. It was all a bit temporary... I left it here for a couple of weeks to get a feel for how it all works, then returned it to the camping rig.

The high voltage stuff is all orange, although you'll notice there's no exposed metal terminals on that stuff, and I vaguely recall popping the bonnet also shuts down the high voltage contactors.
 

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Discussion Starter · #11 ·
Perhaps something like this (earth stake clamp terminal) could be used to attach the positive lead to the copper positive 'terminal' on the 12v battery?
Rectangle Circuit component Metal Fashion accessory Passive circuit component
 

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I use the Cetek battery sense monitor too, it gives a State of charge readout as well as voltage and battery temperature. It’s interesting to see that the battery is not fully charged for long after the charging criteria mentioned by dBC have switched off. I usually give it a charge overnight once a month depending on what the monitor is showing, it can get down to 40%SOC without the Mercedes me app saying there’s anything wrong.
I connected th monitor as normal to the battery terminals, it’s a bit fiddly getting access to the positive side, the black plastic cover with the red sliding lid can be unclipped but it’s easier to see what you’re doing the first time, if you shift the battery cover by removing the 4 screws and leaning it forward. It can be removed if necessary by unclipping the 2 pipe supports fitted to the front and side.
 

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Discussion Starter · #13 ·
Thank you for your comments, FDR - and for the tip on locating the positive terminal. Sounds as if the 12v battery monitor is a worthwhile addition, but disappointing that Mercedes doesn't see fit to build a 12v battery SoC function into MBUX and/or Mercedes me.
 

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Yes, as many manufacturers of EVs seem to have 12volt problems reported by owners in various forum posts (though I don’t see many complaints about this on Teslas for some reason) it would be useful if they could find a place amongst the other information displays for a 12volt monitor.
Mercedes me app does have what they could easily make a more detailed 12volt SoC indicator in the Service menu but it only says “Charged” with no advanced warnings right up to the point when the battery urgently needs charging where it says to get your dealer to charge it. I haven’t found what their low limit is as I’ve only seen the “Charge needed“ warning once, before I got the monitor, and according to my Ctek monitor I have a few times had an indicated 40% SoC, with voltage near 12 V which I think could be low enough to cause battery sulphation even if the car continues to function , so I’ve put it on the charger. As I have it on a spare socket in the garage fixed beside the car, it’s a two minute job to open the bonnet and connect the clips.
 

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Discussion Starter · #15 ·
Thanks again, FDR. I haven't previously seen 12v battery on the service page of Mercedes me. Mine says "partially charged": I'll keep an eye on it from time to time and see if, for instance, it says something different after a long high voltage battery recharge. Better still, when I have a proper measure once I fit my monitor.

You've answered my next question: is it OK to charge the 12v battery by connecting a normal 12v charger to that battery's positive blade under the red plastic slider and the visible negative terminal? I have a NOCO G7200 charger (NOCO - G7200 Overview - Support), which I find very effective. It has a de-sulphation mode, which I've used for several conventional lead-acid batteries and it has brought them 'back to life' with great effect. Not sure I'd try that on the EQA 12v battery at this stage.
 

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FDR what voltage do you see on your monitor when you first plug the car into your EVSE and how long does your typical high voltage battery charge take (I remember you saying they were short because of the 11kW)?

Here's what the battery monitor caught during a ~6 hour charge of my EQC:

Rectangle Slope Font Parallel Pattern

Rectangle Slope Font Parallel Pattern

It roughly held it at 14V throughout. I suspect the 12V battery was in a pretty good SoC to begin with so it probably quickly dispatched the CC stage, and went to the CV stage. A plot of yours during a charge might reveal what's going on.

On a previous occasion I was away for ~3 weeks. I left the car at 50% SoC and plugged in. About 2 weeks in it came to life all by itself and gave the 12V battery a charge for about 40 mins. I didn't have the battery monitor installed then, but the house mains monitor captured it. It was quite an unusual pattern - usually charging the car is a 7500W brick wall, but in this case it was about 6000W for ~8 mins and then a long drawn out taper from ~800W to 400W. I'm assuming that was all about bringing the 12V battery back up to a decent level of charge. It (inadvertently?) took the high voltage battery from 50 to 51% in the process.

Rectangle Slope Parallel Font Pattern
 

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Discussion Starter · #17 ·
Interesting, dBC.

I've had a closer look at fitting the 12v battery monitor when it arrives. (I expect that the Cetek monitor will show 12v battery voltage, state of charge and temperature.)

I would prefer not to remove the metal shroud in front of the battery, so I investigated removing the plastic cover on the positive terminal. I found that the black part of the cover assembly is retained on a sub-assembly with 3 clips. The second attachment shows the cover assembly up the right way and the third attachment shows it inverted. The two side clips are reasonably clear in that photo and the third clip is on the opposite end to the red slide. I found that it released quite easily - as did the side clips, once I spotted them.

When the battery monitor arrives, I plan to fit it with eye terminals sufficiently large to fit over the battery cable clamp bolts. Of course, I want to leave the cable ends connected to the battery, but I am mainly concerned about preventing shorts when working on the positive terminal nut (see first attachment). I plan to line the inside of the metal shroud with reasonably tough plastic sheet and wrap all but the ring end of my spanner in duct tape - then proceed carefully!

Any other suggestions most welcome.
 

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FDR what voltage do you see on your monitor when you first plug the car into your EVSE and how long does your typical high voltage battery charge take (I remember you saying they were short because of the 11kW)?

Here's what the battery monitor caught during a ~6 hour charge of my EQC:

View attachment 1404
View attachment 1405
It roughly held it at 14V throughout. I suspect the 12V battery was in a pretty good SoC to begin with so it probably quickly dispatched the CC stage, and went to the CV stage. A plot of yours during a charge might reveal what's going on.

On a previous occasion I was away for ~3 weeks. I left the car at 50% SoC and plugged in. About 2 weeks in it came to life all by itself and gave the 12V battery a charge for about 40 mins. I didn't have the battery monitor installed then, but the house mains monitor captured it. It was quite an unusual pattern - usually charging the car is a 7500W brick wall, but in this case it was about 6000W for ~8 mins and then a long drawn out taper from ~800W to 400W. I'm assuming that was all about bringing the 12V battery back up to a decent level of charge. It (inadvertently?) took the high voltage battery from 50 to 51% in the process.

View attachment 1406
Lots of interesting info thanks dBC. If my Ctek monitor has a fault it’s that the history graph for voltage isn’t nearly as detailed as your monitor, it needs a bit of guessing to see what the voltage is between 10v and 15v but here’s what it shows for a 2hr 46min charge session on my EVSE taking the traction battery from 26% to 70% the 12v was in a high SoC as the car had been driven for the past few days.
Rectangle Slope Font Parallel Screenshot


The Overview page gives exact voltage figures but not historically. Connecting the EVSE does the same thing as your monitor shows, ie voltage rises to about 14v and continues until the last 10mins (14:50 to 15:00) when it reduces slightly before the charger switches off (at 15:00).
Interesting what happened when you left your car plugged in for 3 weeks. Did you have your car max charge set to 50%? If I did a similar thing and set a scheduled departure time for preconditioning in my car and a max charge limit was set to 50% my Zappi EVSE would charge until the car stopped it at 50% then when the preconditioning time started the Zappi would provide more power but at 6kwh instead of 11kwh. I have seen this with preconditioning, it could be the same thing would happen to protect the 12v battery from discharging.
 

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Interesting, dBC.

I've had a closer look at fitting the 12v battery monitor when it arrives. (I expect that the Cetek monitor will show 12v battery voltage, state of charge and temperature.)

I would prefer not to remove the metal shroud in front of the battery, so I investigated removing the plastic cover on the positive terminal. I found that the black part of the cover assembly is retained on a sub-assembly with 3 clips. The second attachment shows the cover assembly up the right way and the third attachment shows it inverted. The two side clips are reasonably clear in that photo and the third clip is on the opposite end to the red slide. I found that it released quite easily - as did the side clips, once I spotted them.

When the battery monitor arrives, I plan to fit it with eye terminals sufficiently large to fit over the battery cable clamp bolts. Of course, I want to leave the cable ends connected to the battery, but I am mainly concerned about preventing shorts when working on the positive terminal nut (see first attachment). I plan to line the inside of the metal shroud with reasonably tough plastic sheet and wrap all but the ring end of my spanner in duct tape - then proceed carefully!

Any other suggestions most welcome.
Well done getting that plastic cover off without moving the metal shroud! When you fit your monitor you’ll need to make sure the positive eye terminal is in a position to allow the plastic cover to get back down into place, there’s not much spare room under it. Also I tend to try and keep my hand between the spanner and any surrounding metal when working on a battery positive terminal, Bruised fingers are better than sparks and a bang!!
 

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Discussion Starter · #20 ·
Yes, FDR, I'm contemplating how to get the monitor cable past, or through the plastic cover.

Couldn't agree more about avoiding "sparks and a bang"!
 
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