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12V consumption and range increase

Thu Nov 28, 2019 2:38 am

Dear All,

few month that i'm looking for ou C-ZERO or IOn ( here in France, Imiev are not easy to find) and finally i found one.
So i'll have my Ion on next Saturday.

I'm looking on the forum on how to improve global efficiency.
Of course, fist i'll make insulation on doors and on heater.

But i have an other idea , but for the moment i didn't find any information about , so i'll share it with you :

Idea is to change 12V battery to a bigger one (in term of capacity) and to allow system to run on the 12V battery without charging it continuously during driving.

So that , i'll save some energy from principal battery (330V) that is normally used to charge de 12V with the DC/DC converter.

Dors some of you have any data about 12V consumption on board?
I found on different topic about 300 to 400W at "idle". Of course depending of accessories you put "on" that value could increase.

Do you know if some one already did this can of modification?
So i'll need to cheat on DC/DC to stop charging the 12v battery without creating any christmas tree on the dash board ;-)

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Re: 12V consumption and range increase

Thu Nov 28, 2019 6:27 am

Rickilller, congratulations on your purchase and welcome to the forum!

After initially purchasing our i-MiEVs, many of us were obsessed with improving the car's efficiency and thus its range. Over time, we realized that from a practical point of view it simply did not matter as most of the modifications provided a negligible improvement when compared to simply improving our own driving habits. Reality is that very rarely do we need those extra few kilometers and when we do we simply slow down and featherfoot the accelerator to get to that particular destination. In everyday driving range simply does not matter and, in my case, I rarely even fully charge my car and after almost eight years and 100,000 miles of driving the i-MiEV I can still claim that I never saw turtle.

By far the largest energy consumer outside of the car's motive system is the cabin heater, especially now in winter (Northern Hemisphere). The most significant and useful improvement made by our seriously-cold-weather members which you might consider is the addition of a diesel/kerosene/bioethanol heater http://myimiev.com/forum/viewtopic.php?f=14&t=1248

Yes, adding insulation helps of course, both thermally and acoustically, but few of us outside of seriously-cold-weather regions have done that. For myself, if I really need to extend my range in winter I turn off the heater and wear thermal clothing or wrap my legs with a fleece or even a 12v electric blanket (but need to occasionally activate the heater/aircon for window defrosting).

Regarding your concept of a larger 12v battery which you would only charge at home and might have enough storage capacity so as not need the dc-dc during a trip, there are a few different issues -
1. In the overall scheme of things, 12v power consumption is not significant compared with motive power. Other than the fixed draw by the car's electronics, use of the car's headlights or radio or seat heater simply does not matter.
2. The i-MiEV is VERY sensitive to voltage drops in the the 12v system and, we find, most problems with the car stem from this voltage being too low at startup due to older discharged batteries. Avoiding sagging of the 12v battery voltage is very important.
3. After many years of incredible reliability, the Achille's Heel of the i-MiEV is the on-board charger/dc-dc module (OBC/dc-dc) which suffers from a variety of design flaws in addition to an unfortunate placement location in the car. Replacement of this module from Mitsubishi/PSA is cost-prohibitive as it often exceeds the value of the car. For this reason I personally would not do anything that might mess with that module's operation. Luckily, in the USA Mitsubishi has acknowledged this problem and has extended the warranty for this module to ten years.

If I might suggest, first focus employing the many driving tricks available to you to see how easily you can very significantly extend the range of the car, and only then see if you think making additional improvements will really be needed. You can quantify your experiments by utilizing the Range Remaining dashboard display and comparing it to your fuel consumption gauge. By far the most valuable addition you can make to your car is to obtain a bluetooth genuine OBDLink LX or MX module and one of a number of smartphone apps, with my own favorite being CaniOn for Android OS. This will enable you to quantify not only your driving efficiency but will give you insight into your battery status and many other useful car parameters.

Wish you all the best and do let us know of your progress.
EVs: Two '12 Wht/Blu SE Prem., '13 TeslaMS85, three 156v CorbinSparrowsLi(NMC), 24v EcoScoot(LiFePO4)
EV Conv: 156v '86 Ram PU, 144v '65 Saab96
Hybrids: 48v1kW bike
Mothballed ICE: Orig.Owner '67 Saab96V4, '88 IsuzuTrooper; '76 MBZ L206D RHD RV

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Re: 12V consumption and range increase

Thu Nov 28, 2019 8:21 am

300W 12V DC means. 0.3kWh per hour.

If you disable DC DC charger. After one hour driving you will save 3km range :)

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Re: 12V consumption and range increase

Thu Nov 28, 2019 10:02 am

JoeS wrote:The i-MiEV is VERY sensitive to voltage drops in the the 12v system and, we find, most problems with the car stem from this voltage being too low at startup due to older discharged batteries. Avoiding sagging of the 12v battery voltage is very important.

This would be my BIG concern with your idea as well. There are many things which run off 12 volts - Fans, pumps, the brake vacuum pump as well as all the computers and lights - When any of those kick on or off, your voltage will vary . . . . and it will always be 12.6 volts or lower and the car will not like that. The DC to DC converter keeps the car's 12 volt system at a rock steady 14.4 volts regardless of how much current is being drawn from the 12 volt system. 12.6 volts will seem very low and your 12.6 will vary quite a bit depending on which fans, pumps, lights and so forth are running

If you implemented this plan, your range gains will be minimal and I think you'll probably be letting yourself in for an assortment of weird, nearly unsolvable problems . . . . all due to a very low, fluctuating 12 volt system

If this is your first EV, your big range gains will come as you learn how to maximize range by driving sensibly - Avoiding quick starts and avoiding using friction braking as much as possible. Once you learn how to drive an EV for best range, you could then get back in your old ICE and probably see about a 20% increase in gas mileage - It's a real awakening!

2012 iMiEV SE Premium, White
2012 iMiEV SE Premium, Raspberry Metallic
2012 iMiEV SE, White
2017 Chevy Volt Premier
2014 Ford Transit Connect XLT SWB wagon
2006 Itasca Navion Sprinter Motor Home

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Location: Essex, UK

Re: 12V consumption and range increase

Tue Dec 10, 2019 4:12 am

Hi all,

I have thought about this before - I found that the brake booster uses a lot ofamps, like 30 or 40 amps. I read of someone that had a failed booster and had to replace it - they said the new one was a lot lower power consumption. The booster does not run all the time but it would save some power if you fit a more efficient one.

Other range thoughts - replace your front wiper blade with a flat one rather than the original, for reduced wind resistance. Get the best rolling resistance tyres you can, and check that the brakes are not binding (jack up each wheel and check it spins freely). Reduce weight - get a lithium starter battery (check that it can cope with high charge rates, as the dc-dc converter can output 80Amps). Fit LED lights.

Do you have a heated seat? If not get one from an i-miev or get a heated seat cover - it is far more efficient to heat the driver with a 100w than the entire car with the 3kw heater.

Well done on the purchase, they are great fun cars !

Thanks all.

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