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Discussion Starter #1
After thinking about doing this for a long time I finally put a system together. Its extremely simple, actually overly simple. There are still a ton of things to work out but. . . it works. The basic set up is this, 3 x 48V DC power supplies plus 2 x 12V battery float chargers hooked up in series to get about 168V. There is a diode to prevent current from flowing out of the car battery too and that drops it to about 167V. Is this safe? Well, I took several readings of the battery charge and saw it up to 170V( and as low as 145V.) If it normall goes to 170 then 167 should be safe (I think.) The MAJOR problem is that I'm bypassing the battery control module and it doesn't know that the battery is being charged. After starting the car and driving a few minutes the battery control module realizes that the battery is full and resets the state of charge (SOC) to full. To take advantage of the charge I have been driving in higher gear, lower RPMs more battery assist and coasting in neutral the last few miles before home instead of allowing parasitic hidden charging/ normal cruising charging. The power supplies are only 0.3 amps so I'm charging the battery very slowly (hopefully safer.) Also, you can't just hook the positive connection to the top of the battery pack unless you always leave the car on. I have it hooked up to some resistor thing down below (I have no idea what it is but it reads 160ish V when the car is off.) I'm sure I'm going to get a ton of comments about this especially admonishing my bypassing the BCM. The BCM and SOC are not so good in the first place. I always got low voltage SOC resets in the past so I wouldn't be surprised if the SOC is more accurate after a little plug in charging. I will add more info later, just excited about this and wanted to post. I have had it on for only 2 days and driven about 200 miles. The mpg increase is slight so far.
 

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Umm, nicely done??? Don't really understand what real benefit you will get from this, the battery still discharges under boost and recharges while braking and coast. Sure, you might be able to start off with a full battery every morning, but you are still paying for it with house hold A.C. and risking your battery, your life, and personal injury. If you want a plug in car, get one.
 

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good luck.

slower is safer your right about that much... 0.3 amps is about ~1 / 20 the rated capacity of the stock batteries so this part should be ok...

The biggest problem I see is that since you are bypassing the normal SOC control and battery level indication... You don't know what the SOC of the batteries is... Since NiMH does not track the Voltage directly to the SOC you are being a bit risky by charing to a voltage point instead of by amp counting as the SOC stock system does.... At first this won't be an issue... over time it might cause you a big problem... as the SOC that the car thinks it should have gets more and more off from what it is.... only time will tell...

The only other concern I would voice is that NiMH Batteries if charged above 80% capacity on a regular basis tend to have a serivce life around 300 to 500 charge cycles..... If you keep the battery in a sweet spot.. including not charging above 80% or bellow 20% ... then NiMH can have a service life more like 10,000 charge cycles.... that is why honda keeps such tight control of the SOC.... Since you are bypassing that SOC control... be careful you don't charge the battery pack over 80% or you may end up wearing it out much faster than it ever normally would. . . . and remember SOC on NiMH is not linearly conected to the Voltage like a Lead Acid battery is.

But only time will tell....

make sure to let us know how it ends up working for you.

and congradulations.

Eventually my plans for something like this is a bit different.... Eventually I plan to setup a second battery that I can charge up and then use that second battery to extend the use of assist in the car while driving ... by giving the car an extra 20 amps or so from the second battery when it does assist... so if I am doing like 40 amps of assist I should be able to do it for twice as long... kind of like the way Mike does his but I am planning for a high voltage booster battery instead of a lower voltage that needs to be steped up... if you have any questions about trying this you may want to check out Mike's plug in Insight mod at.... http://www.99mpg.com some nice stuff . . . .
 

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I don't understand the point of doing this either. If the Insight had an electric only mode then it might be worth doing but it's not the Insight has a history of a low battery state that needs additional charging. When I had my CVT it always had more than enough juice in the batteries from regenernative charging.
 

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IamIan said:
The only other concern I would voice is that NiMH Batteries if charged above 80% capacity on a regular basis tend to have a serivce life around 300 to 500 charge cycles.....
I'm with Ian on this one, charging up to full SOC and back down again will dramatically shorten the life of the battery.

You can do 100% discharges 10,000 times with the new LiIon types, but with the old NiMH tech in the Insight battery deep cycling could kill it far more quickly than you expect.

Having said that, I'm TOTALLY pro-plug-in for dozens of reasons. It would just be safer for your wallet to take a booster battery approach - at least when a lead-acid pops you won't be shelling out for a new IMA battery.
 

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Discussion Starter #6
booster battery

Tell me more about your booster battery idea. I don't want to rig up a fifth wheel or anything crazy but I do have 144V + worth of small 7 Ah lead acid batteries. That would basically double the battery capacity and only add about 100 Lbs to the car. I already have a way to charge the system, how would you inject the charge? I want to keep this as simple as possible.
 

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First of all, the 5th wheel is not crazy, it works quite well, and I am considering making a high power version for non hybrid pickup trucks and vans.
The safest way to charge is through the SOC current sensor as I have, and only do it when the car is on. The charge voltage under normal conditions can go as high as 180V, the highest I have seen the pack when not charging is 169V. You are probably ok if limiting to 168V, but as Clett and Ian warn, you could be shortning the pack life. Armin is doing something similar to what you are doing, and has many months of data reguarding this type of charging.
Good luck, and be careful that you do not let that expensive smoke out of the batteries, the will not work well once that happens.
;)
 

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Interesting, perhaps we are being too careful.

I appreciate that Honda limit charge range to 20-80% of capacity and that using full 0-100% range will shorten battery life, however we cannot discharge below 20% (can we?) as BCM willl not allow it, if the author perhaps limits charge to 90-95% of max he might get a useful increase in available IMA power with only minimal impact on life. Who knows. I like the idea of starting with a fairly full IMA pack each day especially if charged from some renewable source at low rate <500ma.

Perhaps we can safely charge with the vehicle off, if it recognises the change in SOC after a few minutes use, which the author reports it seems to do. The cold/low ima pack, cold engine morning starts are an mpg killer as we know. Please keep us updated. Peter
 

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Discussion Starter #9
SOC current sensor

Mike,

I would like to go through the SOC current sensor. Where is it? How hard is it to access? I don't mind leaving the car on. Thanks

Tom
 

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Re: booster battery

ibangpots said:
Tell me more about your booster battery idea. I don't want to rig up a fifth wheel or anything crazy but I do have 144V + worth of small 7 Ah lead acid batteries. That would basically double the battery capacity and only add about 100 Lbs to the car. I already have a way to charge the system, how would you inject the charge? I want to keep this as simple as possible.
As mike said . . . I plan to use the same connection point he is using... to keep the SOC correct and such....

Using the high voltage lead acid booster is similar to what I have eventually planed... but you will need a method to limit the current coming from the booster pack or you could end up seeing 70+ Amps being pulled from the booster battery when the car wants to do assist....

I think the easiest way to limit the current from the booster pack is to use a PWM controller ... So far the least expensive PWM controller I have found that would handel a PHEV Booster Battery for the Insight is.....

http://eportal.apexmicrotech.com/mai...df/msa260u.pdf

If I am reading the data sheet correctly... it will do voltage ranges from a minimum of 16V up to a Max of 450V, so the high voltage booster pack shoudl not be a problem ... It can do continuous 20Amp PWM effect .... short peak currents up to 30Amps .... operates in the 90% to 95% efficiency range ..... and when ordering small amount of as little as one unit the price is $221.25 each + Shipping.

Does anyone know of any other PWM controllers that can handel ~190V and 15+Amps that are less expensive than this one?

and of course... if I am mis-reading the data sheet please let me know... or if I am just generally missing anything I would rather know than not.

My eventual plan is a 130 or so cell string of NiMH D cells rated at 10Ah ... they shouldn't have a problem at 20 or 30 amp rates and will be much lighter than a lead acid booster pack... but will be about $800 or so ... so a bit more expensive but not the several thousand dollars of a Li booster pack.

best of luck.
 

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Ian
I met a guy at altwheels that is using a booster battery system for his Prius.
The system as he has it configured has a 115VDC pack of the Valence LiPO batteries.
He is working with another guy to make a voltage flexable input/output DC/DC converter that could output 45 or more amps. It is microcontroller based, and can be configured for the max output voltage and current.
I will be working with him to see if we can define a booster that would work for both Prius and Insight, as well as the Honda Civics. On the Honda IMA systems, boosting the small battery without a mod that will allow more agressive use of the charge, will only have a small MPG improvement for most people. The big gains with the IMA come with heavier assist use and booster charge replacement.
 

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Discussion Starter #13
SOC charging

I moved the charging wires to the top of the battery terminals. The state of charge as indicated at the dash is rising . . . slowly . . .
 

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good new mike... thanks for the tip... I hope it goes well.... keep me updated.

It will be some time before I save up the money for my plug in booster battery project .... I am expecting around $2,000 or so .... and that will take a while for me to save up....

All good stuff..

IAn.!
 

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Discussion Starter #15
update

I had the IMA light come on and didn't think much of it. I unhooked the 12V to reset everything and reconnected it. Then I plugged the charging system in and left the car on (with the car thinking it had no charge from the battery disconnection) This morning I went out to find that the 144V battery was about full (167V up from 155V) but the 12V battery was dead and I couldn't start the car or get a reading on the battery level on the dash. Why did the 12V die? Was it because I disconnected it and the reset prevented the 144V to 12V converter from working or will the 12V always discharge if the car is left on even though the big battery is being charged? I ended up getting over 200 mpg on the way to work (I had to take my bicycle.) :)
 

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I just came across this thread. Good to see the grid-charging crowd is growing!

I use grid charging on a daily (well, nightly) basis. I charge at 0.33A for about 12 hours.

I don't like to keep the car on (since that uses about the same power as I'm chargigng the battery with, dropping efficiency in half! And I don't like to allow the car to force-charge until it realises it's full. This is putting an aggressive charge current into a full battery. A BAD THING.

There is a trick to get the cars SoC to register the charge: After charging over night, turn the ignition on without starting the engine. Wait 2-3 minutes. Observe the SoC to start climbing to full. This is essentially an upper-end recal.


To those who question the point of this: On my daily commute it saves more gas than it uses in electricity to charge the car. And that even at the subsidized gas prices in the US! One big part to this is MIMA. Only with MIMA can you use the grid-charged battery effectively and fully.

Good Luck in your endeavors!
 

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Discussion Starter #18
update

Armin wrote in PM:
I use a bunch of DC power supplies in series to get about 175V. Then I use a constant current source made out of a 7805 regulator with a 15 Ohm resistor to get the 0.33A current. This neatly does two things: it constant-current charges, but also limits maximum voltage, since the 7805 drops 5V and so the charge current will start to drop once the battery reaches 170V. There are protection diodes to prevent the car from blowing up the circuit in case of a power outage.

I connect the positive lead to the "hot" side of the main battery contactor. That way I can charge when the car is off. It's very difficult to reach without electrocuting yourself, unless you take the battery out, first. The negative goes to the negative terminal on the top of the battery. I have a 30A fuse rated for 300VDC directly on the battery connection and a 2A in the charger circuit just in case...


For the 12V battery: of course this is what powers the car when you turn the ignition on. I did some experiments where I kept the car on and had a separate 12V supply hooked up to the little battery to keep it from draining. Just keeping the ignition on uses about 7A, or 84W, which is about the same power as we're charging the traction battery with. Kinda stupid to waste that much! Also not sure if it's ok for the ignition and injection systems to be powered for hours without the engine running.


Ibangpots:

Leaving the car on is totally killing the 12V battery. 84W just to be on is such a waste! I tried charging overnight hooking to the battery with the car off. The battery got up to 165V. I turned the car on for 10 minutes without starting it. No recal happened, I still only have 3 battery bars.

Does anyone know what voltage causes an upper end recal? Maybe I need to go higher, say 170V, but I don't want to overdo it.

Any ideas for providing 12V to the BCM so the car can be left off but the SOC can register correctly?

One other option is to charge the battery fast while leaving the car on. Any ideas on what a safe current is? I'm sure we can go higher than the 0.3 amps that Armin and I independently settled upon. The car must charge via regen braking a lot faster than that but that is when it has the fans on too. The fans shut off when the car comes to idle stop or if the engine hasn't been started yet.

If anyone else is thinking about doing this I put my system together for about $50. Its not that expensive to do but still obviously has problems.


Tom
 

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I see a couple of options . . .

If you leave the car on to have it track the SOC . . .

you could put a seperate battery tender on the 12V to keep it from draining down. . . .

You could switch over to a seperate 12V battery to feed the car for this chargeing that doesn't drain the car's 12V. . . . Switch back when your done charging. . .

Since the stock system's DC-DC down converter is self controlled and just does its thing when it gets power from the high voltage battery pack.... you could put in a type of bypass that lets the DC-DC system keep the 12V charged up.

The batteries during regenerative braking take up to 50 Amps... I would bet that they shouldn't have too much of a problem taking 5 Amps .... but you would want to make sure to have the chargeing cut off before it passes that upper 80% SOC .... that is the tricky part determining the SOC since on NiMH it is not linear with Voltage. . . . if you could do this you could charge the 144V pack in under 1 hour which shouldn't be a problem for the stock 12V to stay on for that long ... Then you also run into the problem of ~170V at 5 Amps is 850 Watts .... and is a bit ahrder to setup.

Or you could do what mike does an charge up a seperate battery and then just limit the current going from that battery into the main battery while you are driving around with either the DC-DC system he has or a PWM.

Makign the fans run while the engine is off is not hard they are just 12V fans... run 12V to them and they will run... but that is just more power consumption... and charging at 5 amps shouldn't cause a problem with over heating.
 

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IamIan said:
Making the fans run while the engine is off is not hard they are just 12V fans... run 12V to them and they will run... but that is just more power consumption... and charging at 5 amps shouldn't cause a problem with over heating.
I started running the fans in the summer, after I noticed that the car would turn the fan on immediately when I started it. Even at a very low charge current, the battery will heat up quite a bit, since it's heating with this very low rate for a very long time. The battery fan doesn't take much power.

In the fall I stoped running the fan, since that helps to get the battery warmed up, so I don't have the problem of limited assist in the morning.
 
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