LiON accessary battery

Seems odd to me that you would stick a LEAD ACID battery in the car as your accessary battery.

The energy density of a LiOH is far superior to the lead acid battery and the life is also superior.

The charge ability is also superior so using a solar panel you would not have to "baby" the charging of the accessary battery like you do with a lead acid battery bank. Lead acid batteries SUCK big time. They are cheap junk. I am betting my lead acid battery lasts about a year or two at most before it has to be replaced.

I hope they us a LiOH battery bank in the future along with a solar panel and you would certainly have a winning combination!

$$$

Exactly - It's all about the $$$

A lithium accessory battery would probly be $300 to $400, if not more (even an Optima is close to $200) and converting the roof into a curved solar panel would be another grand I'll bet

Even if the added cost was only $750, I wouldn't pay it if it was an option

The accessory battery never really discharges because it's constantly being recharged from the traction battery pack which is why they are able to use such a small battery so even an 'el-cheapo' lead acid battery should last 6 or 8 years

Don

Then they should offer a solar panel as an option and that option should cost no more then a few hundred dollars when you buy is large quanties. Or just make it a standard feature like the LEAF. I am quote sure

My understanding of the accessary battery is that while you are driving and NOT plugged in the battery is being discharged and it gets recharged when you plug your vehicle back in. Of course the accessary battery pack is being discharged when you are using the radio, heat seater, windshield washers, headlights, etc.

What is a "traction battery pack". Never head of that one Don. Where is it? (are you saying there are THREE battery packs in this car (accessory battery, main battery and traction battery?)? When you say "constantly being recharged" are you saying that it is constantly being recharged form WHERE? What source? From the main battery pack? Or from the plugged in charging when the car is idle? Please clarify. Thank you!

I doubt if that lead accessory battery will last 6-8 years, but I could be wrong. Why not spend a little more money and install a LiON and never have to replace it the first place?

Don't' people from Mitsubishi every read these posts or reply? Guess not!

The "traction battery" is what you're calling the "main battery." It's the lithium ion pack that drives the car's traction motor, hence traction battery.

Running a few calculations at home, the cost efficiency of an integrated solar panel on the roof of the car just wouldn't cut it. It would be quite a pricey option (likely more than $1,000), and a roof panel would only have peak output at noon when the sun is overhead. The remainder of the day would be varying degrees of suboptimal. The amount of additional charge you might get from a panel would be less than 10% of pack capacity. That's an awfully expensive range extender.

Maybe in the future when they improve the efficiency of solar panels.

mievsolar said:

When you say "constantly being recharged" are you saying that it is constantly being recharged form WHERE? What source? From the main battery pack? Or from the plugged in charging when the car is idle?

Click to expand...

First, let me explain that I do not own an i yet, but I do own a first-generation Honda Insight which has a 144 v. traction battery pack and a 12 v. accessory battery that is charged by the 144 v. battery pack through a DC-DC converter (it converts 144 v. to 12 v.). The 12 v. battery is charged when the ignition is on.

I can't imagine that the i electrical system design would be any different. Allowing the 12 v. battery to discharge while driving just doesn't make sense. If one were driving for a couple of hours at night, in the rain, with the heater on, while listening to one's high-powered audio system, the 12 v. battery would likely totally discharge which would shut down all of the above 12 v. accessories. That would make driving at night in the rain very difficult.

Whether the DC-DC converter is on during traction battery pack charging (i.e., whether the 12 v. battery and traction battery pack are charged together) will have to be answered by an i owner who understands the electrical system better than I do. I wouldn't think that this would be necessary because the 12 v. battery is being charged while driving.

alohart is correct, the 12v battery is constantly being charged (maintained is perhaps a better word) by the dc-dc converter from the main (traction) Lithium battery pack, either while the vehicle is being driven or while the vehicle is charging (owner's manual Page 6-5 para. 12). The only time I see this battery getting discharged is if a light is left on or if the key is turned and the radio and accessories are left running. When that happens, the iMiEV will appear dead because the 12v battery is needed to wake it up.

mievsolar, just because something can technically be implemented (e.g., Lithium 12v auxiliary battery float charged using a solar panel), proper engineering mandates cost-effectiveness for the task at hand. In this case, a simple small inexpensive lead-acid 12v battery meets the task at hand very well, and I would expect it to last many years because it is living in a completely stress-free electrical and thermal environment (unlike an ICE 12v starter battery under the hot hood by the engine). BTW, I have a flooded lead-acid 12v battery in my Isuzu Trooper that is 17 years old and still going strong…

My own preference will be to replace the iMiEV's 12v flooded-lead-acid (FLA) battery with a small sealed AGM battery, but I need to measure the exact dc-dc converter output voltage(s) (and if it is temperature compensated) before I do that. I simply don't like the small amount of corrosive fumes that emanate from an unsealed FLA battery. I did that with my own Gen1 Honda Insight, where a sealed Gel battery was a better match for the dc-dc converter output voltage (2002 model - Honda upped the voltage in later years).

Thank you for the clarification about what charges the 12V battery.

What they tell you is totally misleading, in there Owners handbook p 7 it shows "major functions run by the 12 Volt battery include ...

Then it says "the 12 Volt battery provides to numerous devices in the car. Even if the remaining electricity levels level in the main drive battery lowers, you can continue to use the lights and wipers" That lead me to believe that the 12V battery was charged separately only when the car was charging and that when it was not charging the 12V battery was on its own so to speak. I see why they did what they did, but I do not necessarily agree with it.

That to me suggest that the 12V battery is separate from the main battery. Apparently not true.

I agree 100% that the flooded lead acid is inappropriate in an EV period. AGM is the way to go if you want to stick with lead acid battery which you most likely will have to, but not necessarily. I plan to look into that too.

I disagree with you when you say the 12V battery "it is living in a completely stress-free electrical and thermal environment (unlike an ICE 12v starter battery under the hot hood by the engine)" The 12V battery is in the front of the car and it is subject to temperature extremes. Remember the cabin is heated in the car NOT the inside are where the 12V battery is. The 12V battery in an MiEV has less thermal stress than being in an ICE vehicle, but it still has pretty extreme temperature extremes if you park your car outside.

So one can still put a solar PV panel with a small CC and have the 12V battery being changed by two charge sources during the day and while driving. I see no reason that cannot be done. Plus it seems to me that when one would do that that it would not take as much energy from you main battery as the PV module would be charging instead or better yet set it up so that when the PV array would be charging the 12V battery that the DC/DC converter would simply shut off.

mievsolar: I currently have a number of small regulated solar panels float-charging a few of my rarely-used ICE vehicles, so i understand what you're saying. The vehicles are under covers but the panels are out in the sun. I do this because there are some parasitic battery-draining loads in these vehicles and I had the panels and regulators lying around so it was easy and inexpensive to implement.

For our iMiEV in daily use, I believe this would be a unnecessary: the auxiliary 12v battery is fully charged all the time. Putting a solar panel with regulator would result in a really negligible energy transfer.

A warning to anyone contemplating this: ALWAYS put a smart regulator on the output of a solar panel feeding the battery and don't simply connect the panel directly. Even a small panel can overcharge and cook a 12v battery.

I do agree with you that batteries sitting in a car do indeed get subjected to higher temperature excursions than, for example, if they were sitting inside the house.

This discussion caused me to run out and make the following voltage readings with a fairly good DVM (65degF ambient):

All power off: 12.68v (i.e., fully charged)
ON key position: 12.06v :shock: (much lower than I expected, even with their small FLA battery)
After START: 14.48v (this is the dc-dc converter output)

The 14.48v is a little too high for some AGMs and definitely too high for Gels. I'll need to run some tests to see how this voltage is temperature-compensated.

That 12.06v reading makes me wonder what all the loads are with the key simply turned ON - there was a fan running, the radio was on, hmmm

Joe5

The solar charge controllers trickle charge a typical lead battery to avid starting battery being dead so say 3 months from now and you have not driven the vehicle it will start.

I am talking about a solar panel that can do a bit better. And yes with a lead acid battery one needs a charge controller.

How does your 12V aux battery remain fully charged all the time? You say there is a DC/DC converter in the vehicle. My understanding is that the DC/DC converter goes from 330V DC to 12V DC.

What you could do is simply disconnect the DC/DC charger and replace the wires with a solar array with the proper CC. That way the DC/DC converter would not be sucking juice out of you main battery bank. One thing I am not clear on is does the AC run off the 12V aux battery too?

mievsolar: the dc-dc converter provides our primary 12vdc power, in addition to charging our 12v battery. Excluding heating and a/c, the vehicle 12v system is a negligible load on our HV traction battery compared to the drive motor. Why separate the 12v battery from the dc-dc and risk having it run down and disable the vehicle? Certainly don't want a larger and heavier 12v battery, either. I haven't looked at either heating or a/c to see how they're implemented. If you want to use solar efficiently, then rig up a dc-dc converter to charge the Lithiums directly, albeit slowly (speed being simply a function of solar size).

Everything runs off the 330 volt traction battery, as it should - That's where all the power is stored

There are many things on the car which require 12 volts - The stereo, all the lights, the wipers, the heater fan, the power steering, the motor and inverter cooling system, all the computer equipment and many other things. Those also run off the 330 volt battery, via a DC to DC converter. The little 12 volt battery basically acts as a big capacitor, showing a constant load to the converter so it doesn't react to spikes in load like when you turn on the headlights, wipers, blower fan etc. There isn't a battery in any car which has a less stressful life than the 12 volt battery in our cars. The only load on them at all is when you turn the key to the ACC position, before you start the car - All other times, the battery is constantly being float charged as the DC to DC converter outputs slightly more than all the 12 volt loads put together

I'll be very surprised if the little 12 volt battery doesn't last 8 to 10 years - The system is so well designed, that battery is the least of our worries

Don

Don said:

There isn't a battery in any car which has a less stressful life than the 12 volt battery in our cars.

Click to expand...

Maybe this statement should be modified to read, "There isn't a battery in any standard internal combustion engine car…". The 12 v. batteries in probably all gas-electric hybrids don't do any more than that in the i under normal operating conditions.

Don said:

I'll be very surprised if the little 12 volt battery doesn't last 8 to 10 years

Click to expand...

The 12 v. batteries in early Honda Insights don't seem to last any longer than those in regular cars. The explanation is that a starter battery needs to be exercised to stay healthy. Being float-charged continuously seems to shorten its live. There are long-life 12 v. lead-acid batteries designed to be float-charged continuously, but these aren't the relatively inexpensive batteries installed in cars. Some Insight owners used to partially discharge their 12 v. batteries monthly by turning on their headlights, ventilation fans, and other 12 v. loads to exercise their batteries. One had to be careful not to discharge them too far, so the bother of this exercise routine seemed too onerous for most owners.

Because the 12 v. batteries in hybrids and EV's get so little exercise, it's not easy to detect when they're wearing out until the day that they don't produce enough power to boot the computers and controllers, turn on the relays, etc., that are necessary for the car to operate. I suspect that this will occur with the i as well.

great question about the AC running off of the auxiliary battery. If it does then one should have no issues running the AC off of the solar charged auxiliary battery. WHy because when you need the AC is when you the sun shine s the most. A perfect match!

If one can locate the AC unit and see where the wires go that would be the answer. Anyone up for that mission?

There are no big loads running off the auxilliary battery - Biggest would probably be about 120 watts (10 amps) worth of headlights when they are on . . . . unless the power steering or wiper motor draws more than that. I'm guessing the climate control fan is probably on the order of 100 watts too, same for the drivers seat heater - All are small potatoes, comparitively speaking. The DC to DC converter can handle 1 Kw (85 amps @ 12 volts) which covers all the loads even when everything is running at once, with enough left over to maintain the auxilliary battery

The AC compressor is powered by a 330 volt DC motor, running directly off the traction pack - Same for the 5Kw heating element which heats the water for cabin heat

The A/C draws 4.5 Kw . . . . at 12 volts, that would be 375 amps - The heater is even worse . . . . 5 Kw which would be over 400 amps if run off a 12 volt source

http://myimiev.com/forum/viewtopic.php?f=10&t=483

Don

One thing I haven't seen mentioned in this discussion (or maybe I just missed it) is that these are not your normal ICE leadacid accessory/starter Battery. The battery in the i is a Deep Cycle style Battery. And as you all know, the lifetime is much much greater on a Deep Cycle than a normal "Starting" battery that you find in ICE's. Especially when you use some kind of "battery tender", (driving and plugging in the i server this purpose very well) to keep it topped off from time to time. If you own a camper or a boat, you've probably got plenty of experience with these things.


Also, it was mentioned that these batteries have an easy life. This is also true. While yes, they do see some environmental heat, even in the hottest conditions this is vastly less than the temperatures under the hood of an ICE.

I would imagine the 12v in the i should last many many years. I'll be very surprised if I get anything less than 6 years of non-degraded use out of it.

Anyway, I might be wrong on this, (i don't have access to my i right now, it's parked about a mile away) so I can't read the part number off of the battery to 100% verify this.

I think you will find the AC unit is rated at 4.5kw cooling output (not consumption) AC units are typically 200 - 300% efficient. When the compressor motor is running it is most likely only consuming 1.5kw or so from the battery.Then on top of that you have to factor in cycling time of the compressor motor. The actual consumption over say 1hr running might be as low as 1kwh.

The heater being a direct resistive load will consume the full 5kw when running. Consumption over 1hr might be little less if its thermostatically controlled and able to cycle a little.

Kurt

offgridQLD said:

I think you will find the AC unit is rated at 4.5kw cooling output (not consumption) AC units are typically 200 - 300% efficient. When the compressor motor is running it is most likely only consuming 1.5kw or so from the battery.Then on top of that you have to factor in cycling time of the compressor motor. The actual consumption over say 1hr running might be as low as 1kwh.

Click to expand...

It's important to post actual facts about the car's systems, rather than what we think is 'most likely'

The A/C compressor is a scroll type which uses a rare earth magnet motor and it is powered by it's own inverter system directly off the car's 330 volt traction battery. Mitsu says if uses 4.5Kw because when the compressor is running, it's motor draws 20.5 amps @ 220 volts, which is actually . . . . 4.5Kw. True, it doesn't run all the time . . . . unless you have the temp dial set to coldest and the MAX button depressed, so the typical load in normal everyday usage averages much less than 4.5Kw . . . . but when it's running, it does draw the 4.5Kw they say it does

Incidentally, Mitsu claims that the electric A/C system in the iMiEV slightly outperforms the mechanical system in the original ICE version of the I car. A ton (12,000 btu) of air conditioning is the equivalent of 3.5Kw, so our car must have about 15,000 btu's of cooling, though they don't give a specific figure for that. The 'average' automobile A/C system is rated at 1 3/4 ton (21,000 btu's) by comparison, so ours is smaller than average

There's a .pdf file which explains the cars climate control systems in great detail complete with diagrams, schematics and photos. http://myimiev.com/forum/viewtopic.php?f=19&t=551

Don

Don said:

The 'average' automobile A/C system is rated at 1 3/4 ton (21,000 btu's) by comparison, so ours is smaller than average.

Click to expand...

All I know is that, even in 100°F+ temperatures, my little i-MiEV has no problem keeping the cabin cool. I don't have tint on the windows, either, since it's a lease.

Don said:

The A/C compressor is a scroll type which uses a rare earth magnet motor and it is powered by it's own inverter system directly off the car's 330 volt traction battery. Mitsu says if uses 4.5Kw because when the compressor is running, it's motor draws 20.5 amps @ 220 volts, which is actually . . . . 4.5Kw. True, it doesn't run all the time . . . . unless you have the temp dial set to coldest and the MAX button depressed, so the typical load in normal everyday usage averages much less than 4.5Kw . . . . but when it's running, it does draw the 4.5Kw they say it does

Incidentally, Mitsu claims that the electric A/C system in the iMiEV slightly outperforms the mechanical system in the original ICE version of the I car. A ton (12,000 btu) of air conditioning is the equivalent of 3.5Kw, so our car must have about 15,000 btu's of cooling, though they don't give a specific figure for that. The 'average' automobile A/C system is rated at 1 3/4 ton (21,000 btu's) by comparison, so ours is smaller than average

There's a .pdf file which explains the cars climate control systems in great detail complete with diagrams, schematics and photos. http://myimiev.com/forum/viewtopic.php?f=19&t=551

Click to expand...

Great info.
I found the graph showing decrease in range for heat and AC interesting. Max heat really decreases range, something we owners know too well.
The new Nissan Leaf's SV and SL models (not the basic S model) come with a heat pump instead of a resistance heater that uses less energy in cold weather and extends range.
Now if the Nissan Leaf could only improve it's battery thermal management. The Nissan Leaf now comes with a battery warmer for temperatures below -4 degrees F, but the Leaf still doesn't have any mechanism for cooling the battery.