Battery charging circuit

[Damn Dan]

I've been working on a project that would recharge the battery of my Honda
Insight (a hybrid vehicle) while I'm parked at work using a solar panel.
The Insight's battery pack averages around 165V during usage. Currently I
have the solar panel constantly charging a 12V battery with an appropriate
charge controller. The battery is then connected to a 12Vdc to 120Vac
inverter, which is connected to a 120Vac to 220Vac converter, which is in
turn rectified to 220Vdc. I actually only get 200Vdc in the end, I guess
just due to inefficiencies.

I'm trying to design a current limiter that would only allow as much power
into the 165V battery as is coming in from the solar panel. The panel is
80W, so after it's been stepped up to 200V, the output current is 0.4Amps
(200V * .4A = 80W). Thus, I want to implement a current limiter that will
only allow 0.4A into the 165V battery.

The main issue I'm dealing with right now is understanding how two power
sources interact with each other in the same circuit. Specifically, I have
a 200V source charging a 165V battery with 0.4Ohms internal resistance. So
is that exactly equivelent to setting up a circuit with a 35V source
(200V-165V = 35V) and a 0.4Ohm resistor? I set that circuit up in PSpice,
but it doesn't seem to account for the two DC sources interacting with each
other. Any thoughts?

 

[Ross Herbert]

You are starting from the wrong end...

You need to determine the charging requirements of the 165V battery
itself before anything else. Only then can you determine what is
required of your charging circuitry and design it accordingly. The
fact that you want to use a 12V (nominal), 80W solar panel as the
charging source simply because that is what you have on hand is not
the way to go about the problem. Once you know what the charging
requirements of the battery are you can then determine how many solar
panels you will require in order to charge a 12V,24V or 48V battery to
power a suitable dc - ac inverter/rectifier/charging arrangement.



|I've been working on a project that would recharge the battery of my Honda
|Insight (a hybrid vehicle) while I'm parked at work using a solar panel.
|The Insight's battery pack averages around 165V during usage. Currently I
|have the solar panel constantly charging a 12V battery with an appropriate
|charge controller. The battery is then connected to a 12Vdc to 120Vac
|inverter, which is connected to a 120Vac to 220Vac converter, which is in
|turn rectified to 220Vdc. I actually only get 200Vdc in the end, I guess
|just due to inefficiencies.
|
|I'm trying to design a current limiter that would only allow as much power
|into the 165V battery as is coming in from the solar panel. The panel is
|80W, so after it's been stepped up to 200V, the output current is 0.4Amps
|(200V * .4A = 80W). Thus, I want to implement a current limiter that will
|only allow 0.4A into the 165V battery.
|
|The main issue I'm dealing with right now is understanding how two power
|sources interact with each other in the same circuit. Specifically, I have
|a 200V source charging a 165V battery with 0.4Ohms internal resistance. So
|is that exactly equivelent to setting up a circuit with a 35V source
|(200V-165V = 35V) and a 0.4Ohm resistor? I set that circuit up in PSpice,
|but it doesn't seem to account for the two DC sources interacting with each
|other. Any thoughts?
|

 

[mike]

I've been working on a project that would recharge the battery of my Honda
Insight (a hybrid vehicle) while I'm parked at work using a solar panel.
The Insight's battery pack averages around 165V during usage. Currently I
have the solar panel constantly charging a 12V battery with an appropriate
charge controller. The battery is then connected to a 12Vdc to 120Vac
inverter, which is connected to a 120Vac to 220Vac converter, which is in
turn rectified to 220Vdc. I actually only get 200Vdc in the end, I guess
just due to inefficiencies.

I'm trying to design a current limiter that would only allow as much power
into the 165V battery as is coming in from the solar panel. The panel is
80W, so after it's been stepped up to 200V, the output current is 0.4Amps
(200V * .4A = 80W). Thus, I want to implement a current limiter that will
only allow 0.4A into the 165V battery.

The main issue I'm dealing with right now is understanding how two power
sources interact with each other in the same circuit. Specifically, I have
a 200V source charging a 165V battery with 0.4Ohms internal resistance. So
is that exactly equivelent to setting up a circuit with a 35V source
(200V-165V = 35V) and a 0.4Ohm resistor? I set that circuit up in PSpice,
but it doesn't seem to account for the two DC sources interacting with each
other. Any thoughts?

I'm fascinated by all this.
Over 8-hours, you get at most 640WH. Depending on where you live and
what season it is and the weather and...and...and...maybe MUCH less.
About how much gas will this save you per day??
How much gas does it cost you to haul around all this extra weight?
What's the cost of a new set of batteries when your controller fries
'em? What's the cost of
the remote alarm system you'll need to let you know when someone stole
the panel?

Where are you gonna park it? Complete address please ;-)

....fascinating...
mike

--
Return address is VALID.
500MHz Tek DSOscilloscope TDS520
Wanted, 12.1" LCD for Gateway Solo 5300. Samsung LT121SU-121
Bunch of stuff For Sale and Wanted at the link below.
http://www.geocities.com/SiliconValley/Monitor/4710/

 

[Watson A.Name - \Watt Sun, the Dark Remover\]

You are starting from the wrong end...

You need to determine the charging requirements of the 165V battery
itself before anything else. Only then can you determine what is
required of your charging circuitry and design it accordingly. The
fact that you want to use a 12V (nominal), 80W solar panel as the
charging source simply because that is what you have on hand is not
the way to go about the problem. Once you know what the charging
requirements of the battery are you can then determine how many solar
panels you will require in order to charge a 12V,24V or 48V battery to
power a suitable dc - ac inverter/rectifier/charging arrangement.

I don't buy that at all. Firs off, he doesn't need to know the charging
requuirements of the 165V battery because it can charge at anywhere up
to hundreds of amps for short periods. And he will never be able to buy
enough solar cells to do that, let alone the next problem.

And the next problem is that the solar cells will put out anywhere from
max to min to zero depending on the time of day, and the weather,
cloudy, overcast, etc. So he needs a converter that can handle a large
variation in input power. Why should he need an intermediate battery,
12V, etc. to charge? That's just a waste of efficiecny.

What he needs is a converter that monitors the input voltage to see if
it drops below a threshold, as long as it stays at about 12V, pull as
much current from the solar cells as it can. Then monitor the output
voltage to make sure it doesn't go much above 200V, so that if the
converter is not plugged into the battery, it shuts down.

What I would do is start with a standard Dc-Dc converter like those used
for running tube equipment off 12V. Add an overvoltage monitor to the
output, and under voltage to the input. And fuses, of course.

And he can put a large capacitor across the solar cell, to hold enough
charge to run the converter for a second or two. If the converter
charges in spurts, that's okay, too.

 

[Watson A.Name - \Watt Sun, the Dark Remover\]

I'm fascinated by all this.
Over 8-hours, you get at most 640WH. Depending on where you live and
what season it is and the weather and...and...and...maybe MUCH less.
About how much gas will this save you per day??
How much gas does it cost you to haul around all this extra weight?
What's the cost of a new set of batteries when your controller fries
'em? What's the cost of
the remote alarm system you'll need to let you know when someone stole
the panel?

Where are you gonna park it? Complete address please ;-)

...fascinating...
mike

Geez, what a skeptic. Maybe he works on a campus with a guard t the
gate. Fries what batteries? It's unlikely to do that. As for saving
gas, that's a valid question, but it may have some saving.

But I'd say it's none of your biz where I park it!

 

[Damn Dan]

I don't buy that at all. Firs off, he doesn't need to know the charging
requuirements of the 165V battery because it can charge at anywhere up
to hundreds of amps for short periods. And he will never be able to buy
enough solar cells to do that, let alone the next problem.

And the next problem is that the solar cells will put out anywhere from
max to min to zero depending on the time of day, and the weather,
cloudy, overcast, etc. So he needs a converter that can handle a large
variation in input power. Why should he need an intermediate battery,
12V, etc. to charge? That's just a waste of efficiecny.

What he needs is a converter that monitors the input voltage to see if
it drops below a threshold, as long as it stays at about 12V, pull as
much current from the solar cells as it can. Then monitor the output
voltage to make sure it doesn't go much above 200V, so that if the
converter is not plugged into the battery, it shuts down.

What I would do is start with a standard Dc-Dc converter like those used
for running tube equipment off 12V. Add an overvoltage monitor to the
output, and under voltage to the input. And fuses, of course.

And he can put a large capacitor across the solar cell, to hold enough
charge to run the converter for a second or two. If the converter
charges in spurts, that's okay, too.

Right, getting enough panels to produce that much voltage would be
financially and physically impossible. The second problem you mentioned is
actually the very reason I went for the 12V battery as a middle-man.
Originally I wanted to hook the panel directly to the 165V battery through
the converter. But my main constraint is that I'm trying to do this El
Cheapo style. I did a bit of research but found no reasonably cheap (i.e.
less than $50) 12V-200V DC-DC converters. If you happen to know of one,
please let me know! The inexpensive solution I have come to is using a
regular car inverter that you plug into your cigarette lighter. That gives
me 120Vac. I step that up with a international power converter that you can
buy at any Radio Shack. The 200 or so volts out of that gets rectified to
DC. All in all, it cost just over $50. So now the reason I'm attaching the
car inverter to the 12V battery is all car inverters have safety mechanisms
that shut off power if the inverter detects a "weird" voltage input. The
solar panel outputs between 15V and 20V, which it considers "weird", so it
doesn't work. The 12V battery keeps the voltage at an unweird level. It
also accomodates for any variation that the solar panel will give due to
weather conditions and time of day. Plus, it keeps a steady, predictable
current into the 165V battery. But like I said, if you know of any
off-the-shelf, cheap converters that would accomplish the same goal, I'm all
ears.

 

[Damn Dan]

I'm fascinated by all this.
Over 8-hours, you get at most 640WH. Depending on where you live and
what season it is and the weather and...and...and...maybe MUCH less.
About how much gas will this save you per day??
How much gas does it cost you to haul around all this extra weight?
What's the cost of a new set of batteries when your controller fries
'em? What's the cost of
the remote alarm system you'll need to let you know when someone stole
the panel?

Where are you gonna park it? Complete address please ;-)

...fascinating...
mike

Mike. Your credulousness is embarassing you. In an attempt to demonstrate
your expertise, you've done nothing but make an ass of yourself. Since all
of your conclusions are based on incomplete evidence and a thorough lack of
understanding of the subject matter, allow me to explain.

I live in Arizona. If you do a little research, you'll find that the
Southwest receives some of the highest solar energy per square foot in the
country. The change of seasons and weather do not change the ambient solar
energy all that much around here.

My hybrid battery has a mere 6.4Ah capacity. The internal circuitry limits
the available capacity to the middle 60%, thus there is a realistic capacity
of 3.84Ah. On my drive to work, I use between 5-10% of that capacity.
That's .384Ah. By keeping my battery charged, I prevent the electric
generator from sipping energy off of my forward momentum to recharge the
battery. I have calculated through observation that I get about 10mpg less
when the battery is charging itself while I drive. So yes, acheiving .384Ah
a day will save a lot of gas.

By implying that the extra weight of a solar panel will have a non-trivial
affect on my gas mileage, you are only proving your lack of understanding of
inertial physics. The car weighs 1800 pounds. With me in it, it weighs
1955 pounds. The panel weighs 17 pounds. You do the math.

An 80W panel, once stepped up to 200V, will only deliver at most 0.4A. This
will trickle charge the battery. Rechargable batteries are able to handle
trickle charging for a very long period of time (on the order of weeks or
months). As you have already proven you know nothing about the subject, I
did not expect you to know that.

Finally, I do not expect to mount the panel on the outside of my car, so
there is no reason to introduce an extra security system. The panel will
rest on the dashboard of my car, with the nose of the car facing the daily
path of the sun. The energy lost to my front windshield is minimal (I have
already tested it), so that is what I will do.

In conclusion, Mike, bugger off.

 

[Ross Herbert]

On Mon, 18 Oct 2004 05:56:40 -0700, "Watson A.Name - \"Watt Sun, the

|
||> You are starting from the wrong end...
|>
|> You need to determine the charging requirements of the 165V battery
|> itself before anything else. Only then can you determine what is
|> required of your charging circuitry and design it accordingly. The
|> fact that you want to use a 12V (nominal), 80W solar panel as the
|> charging source simply because that is what you have on hand is not
|> the way to go about the problem. Once you know what the charging
|> requirements of the battery are you can then determine how many solar
|> panels you will require in order to charge a 12V,24V or 48V battery to
|> power a suitable dc - ac inverter/rectifier/charging arrangement.
|
|I don't buy that at all. Firs off, he doesn't need to know the charging
|requuirements of the 165V battery because it can charge at anywhere up
|to hundreds of amps for short periods. And he will never be able to buy
|enough solar cells to do that, let alone the next problem.

A logical approach would need to balance the time it takes to charge
the 165V battery in the time space determined by the OP's time frame,
so he does need to know the charging requirements. He might require
the battery to be charged in 4 hrs or less, since he is talking about
solar charging, and the weather conditions would have some bearing on
whether that is possible. The fact that he may need more than one
panel is therefore dependant upon this time frame.

|
|And the next problem is that the solar cells will put out anywhere from
|max to min to zero depending on the time of day, and the weather,
|cloudy, overcast, etc. So he needs a converter that can handle a large
|variation in input power. Why should he need an intermediate battery,
|12V, etc. to charge? That's just a waste of efficiecny.

Exactly.... However, a nominal 12V, 80W panel can deliver a max of
around 6.8A peak and that will vary up and down depending on weather
conditions. One thing you can be sure of is that for 60 - 70% of the
year the maximum output of the panel will never be achieved, therefore
some consideration will be necessary to increase input capacity to
whatever converter is used in order to raise the actual output above
the theoretical maximum.

|
|What he needs is a converter that monitors the input voltage to see if
|it drops below a threshold, as long as it stays at about 12V, pull as
|much current from the solar cells as it can. Then monitor the output
|voltage to make sure it doesn't go much above 200V, so that if the
|converter is not plugged into the battery, it shuts down.

I agree. It would be wonderful to design a 12V > 165V converter to run
directly off solar panels such that it could accurately control the
charging in the required time frame while at the same time taking into
account the variable input voltage. I think this is not the best
method since the panel might not be able to get started on cloudy
days. If a battery is used it can be storing charge at all times when
charging of the 165V battery is not being undertaken so that when
required it will start charging immediately and it will also smooth
out the peaks and troughs in the panel output. The very same converter
you suggest is just what you would need even with a battery although
the input voltage monitoring might not be so important depending on
the battery capacity.

|
|What I would do is start with a standard Dc-Dc converter like those used
|for running tube equipment off 12V. Add an overvoltage monitor to the
|output, and under voltage to the input. And fuses, of course.
|
|And he can put a large capacitor across the solar cell, to hold enough
|charge to run the converter for a second or two. If the converter
|charges in spurts, that's okay, too.

Yep, this would work. However, what do you do when you desperately
must have the 165V battery charged right now and the weather is such
that only brief periods of sunshine were available during the daytime?
At least with a panel storage battery already fully charged you could
dump most of the stored capacity into the 165V battery via the
charging converter.

I know who's system would work best and it wouldn't be yours.

 

[Watson A.Name - \Watt Sun, the Dark Remover\]

[snip]

Right, ftting enough panels to produce that much voltage would be
financially and physically impossible. The second problem you mentioned is
actually the very reason I went for the 12V battery as a middle-man.
Originally I wanted to hook the panel directly to the 165V battery through
the converter. But my main constraint is that I'm trying to do this El
Cheapo style. I did a bit of research but found no reasonably cheap (i.e.
less than $50) 12V-200V DC-DC converters. If you happen to know of one,
please let me know!

Just about every inverter nowadays is a DC-Dc converter. The first
thing they do is convert the 12V to 320VDC, then chop it up into AC with
some power FETs. So if you have a cheap inverter, check it out
internally, without power of course.

The trick is to get it to put out lower than 320V or so. I guess you
could remove windings off the transformer. Or else if it uses a v
doubler circuit, then change it to be a half wave rectifier. In any
case, for 30 bucks or even less on sale, you may be able to get yourself
a system that skips over all that multi conversion and gets straight to
the point. Anyway, be careful of high voltages, and caps that might
stay charged even when off. High voltage Dc can be very nasty.

The inexpensive solution I have come to is using a
regular car inverter that you plug into your cigarette lighter. That gives
me 120Vac. I step that up with a international power converter that you can
buy at any Radio Shack. The 200 or so volts out of that gets rectified to
DC. All in all, it cost just over $50. So now the reason I'm attaching the
car inverter to the 12V battery is all car inverters have safety mechanisms
that shut off power if the inverter detects a "weird" voltage input. The
solar panel outputs between 15V and 20V, which it considers "weird", so it
doesn't work. The 12V battery keeps the voltage at an unweird level. It
also accomodates for any variation that the solar panel will give due to
weather conditions and time of day. Plus, it keeps a steady, predictable
current into the 165V battery. But like I said, if you know of any
off-the-shelf, cheap converters that would accomplish the same goal, I'm all
ears.

Well, hear, hear!

 

[Watson A.Name - \Watt Sun, the Dark Remover\]

[snip]

Yep, this would work. However, what do you do when you desperately
must have the 165V battery charged right now and the weather is such
that only brief periods of sunshine were available during the daytime?

You start the engine. THis is a h-y-b-r-i-d vehicle!

At least with a panel storage battery already fully charged you could
dump most of the stored capacity into the 165V battery via the
charging converter.

I know who's system would work best and it wouldn't be yours.

An intermediate battery would be just a waste of efficiency. Leave it
out.

 

[Damn Dan]

[snip]

Yep, this would work. However, what do you do when you desperately
must have the 165V battery charged right now and the weather is such
that only brief periods of sunshine were available during the daytime?

You start the engine. THis is a h-y-b-r-i-d vehicle!

At least with a panel storage battery already fully charged you could
dump most of the stored capacity into the 165V battery via the
charging converter.

I know who's system would work best and it wouldn't be yours.

An intermediate battery would be just a waste of efficiency. Leave it
out.

If I may peacefully chime in here.

I wanted to clarify that I only use a fraction of the usable 3.8Ah of the
battery. At most I would need to recharge a 1/10th of that capacity, which
by my elementary calculations shouldn't take too long, even after
considering in substantional ineffiencies.

Watson, I looked inside of my inverter... and basically forget about it.
It's way too complicated. It's a double-sided printed board and the little
bit of multimeter probing I did returned nothing I was able to understand.
Unfortunately my electronics abilities are far inferior to start
reverse-engineering that thing. Although even if I was able to get the
inverter to give me 200V, I still have the inverter's "safety" feature to
contend with, which is why I am including the battery. The solar panel puts
out a voltage that is above the inverter's tolerance range. Thus far,
introducing a 12V battery, however inefficient, is the only solution I've
come up with.

Ross, my philosphy with this project is basically "get whatever I can get in
8 hours at work". I'm going to feed the battery a mere trickle-charge that
could not possibly charge the whole battery in a day. Instead, I hope to
simply recover the loss I accrued while driving to work, which is very small
compared to the capacity of the battery. During the 6 mile drive, I almost
recover the charge I use through regenerative braking, but not quite, so
there's a slight net loss.

-Dan

 

[nospam]

Mike. Your credulousness is embarassing you.

I presume he didn't also spend that much money on an 'economy' car - he is
rather less credulous than you.

An 80W panel, once stepped up to 200V, will only deliver at most 0.4A. This
will trickle charge the battery. Rechargable batteries are able to handle
trickle charging for a very long period of time (on the order of weeks or
months). As you have already proven you know nothing about the subject, I
did not expect you to know that.

Your car battery has an energy storage capacity of around 3.4MJ. Gasoline
has a stored energy capacity of around 43MJ/kg.

Assuming your battery/controls/electric motor is twice as efficient as your
car engine your battery is equivalent to 16g or about 22ml of gasoline.

Assuming you could arrange to arrive at work every day with a completely
flat battery (which you can't) and fully charge it during the day you
would save 22ml of gas.

You real gas saving is unlikely to be more than 1/2 gallon/year. Do you
think that is worth all the trouble you are going to and the 300? bucks you
spent on the panel?

 

[William P.N. Smith]

I've been working on a project that would recharge the battery of my Honda
Insight (a hybrid vehicle) while I'm parked at work using a solar panel.

You might ask in alt.solar.photovoltaic for some ideas about charging
directly from your panel thru an appropriate step-up charge
controller, your proposal of
panel->chargecontroller->battery->inverter->voltagedoubler->dcconverter->chargelimiter->battery
is really inefficient in terms of time, money, mass, efficiency, etc.

A solar panel is (to a first approximation) a current source, where
the output current depends on the instantaneous insolation, FWIW. At
the very least, your "chargelimiter" has to measure or infer solar
panel output in order to match input and output power...

Also, make sure the charge controller you use is appropriate for your
Insight battery pack, both in terms of chemistry, construction, and
float voltage levels, or you might risk significant damage to your
battery pack, which is probably a very expensive replacement, and
adding your own charger will certainly void the warranty.

[Does Honda sell a line voltage charger for the car? Analysis of
Honda's charge systems might be instructive.]

 

[Damn Dan]

I presume he didn't also spend that much money on an 'economy' car - he is
rather less credulous than you.

Are you implying that having a fuel efficient car is not advantageous?
Please, explain.

Your car battery has an energy storage capacity of around 3.4MJ. Gasoline
has a stored energy capacity of around 43MJ/kg.

Assuming your battery/controls/electric motor is twice as efficient as your
car engine your battery is equivalent to 16g or about 22ml of gasoline.

Assuming you could arrange to arrive at work every day with a completely
flat battery (which you can't) and fully charge it during the day you
would save 22ml of gas.

You real gas saving is unlikely to be more than 1/2 gallon/year. Do you
think that is worth all the trouble you are going to and the 300? bucks you
spent on the panel?

You have misinterpreted my strategy. My intent is not to substitute solar
energy for gallons of gas. If I were trying to do that, I'd need a head
check. My intent (as I stated in another post of this thread) is to prevent
the electric generator from sipping power from my forward momentum. From
observation, I take a 10mpg deduction whenever that occurs. If I keep the
state of charge of the battery above the 50% mark, it does not sip power and
thus I acheive maximum mileage (about 70mpg).

On an ordinary drive to work, I have a net loss of about 10% of the capacity
of my battery. The usable capacity is 3.8Ah (60% of the total capacity).
Ten percent of that is .38Ah. Since you like to measure things in Joules,
that's 197kJ. My 80W panel, assuming 6 hours of good sun, will give me
1.73MJ. That's almost 10 times the amount I need. Work in some efficiency
loses and I'm probably still well above 197kJ.

If I am successful, I will average about 10mpg higher for a large percentage
of my driving. So yes, that equates to a lot of financial and environmental
savings.

 

[Damn Dan]

You might ask in alt.solar.photovoltaic for some ideas about charging
directly from your panel thru an appropriate step-up charge
controller, your proposal of
panel->chargecontroller->battery->inverter->voltagedoubler->dcconverter->cha
rgelimiter->battery
is really inefficient in terms of time, money, mass, efficiency, etc.

A solar panel is (to a first approximation) a current source, where
the output current depends on the instantaneous insolation, FWIW. At
the very least, your "chargelimiter" has to measure or infer solar
panel output in order to match input and output power...

Thanks for pointing me to the photovoltaic newsgroup. Didn't know about
them before.

I completely agree with you that my setup is wrought with inefficiency. I
think what I'm going to do, though, is use this setup for now just as a
proof of principle. Basically because it's the simpliest and it doesn't
need an intelligent current controller to compensate for a varying solar
panel. The battery will provide a constant current for as long as it has
charge to give. Once I have this system working, I'll try to start
eliminating components from it and making it more efficient. I am
optimistic, though, because based on some elementary calculations, my system
only needs to be about 11% efficient to recharge the 10% battery capacity I
use during my daily commute. I'll see how things go when I actually
implement it.

Also, make sure the charge controller you use is appropriate for your
Insight battery pack, both in terms of chemistry, construction, and
float voltage levels, or you might risk significant damage to your
battery pack, which is probably a very expensive replacement, and
adding your own charger will certainly void the warranty.

[Does Honda sell a line voltage charger for the car? Analysis of
Honda's charge systems might be instructive.]

Honda's "charge controller" for the Insight battery is not a typical
controller in the usual sense of the word. A computer monitors the state of
the battery using temperature sensors and voltmeters. It also actively
keeps track of all current going in and out of the battery. Using that
data, it makes an estimation about the state of the battery and informs the
electric engine about its condition. The electric engine then sends power
to the battery (to recharge it, if it is ok to charge) or receives power
from the battery (during assist mode, if it is ok to load) based on the
state of the battery. So really its the electric motor that acts as the
"charge controller".

 

[William P.N. Smith]

A computer monitors the state of
the battery using temperature sensors and voltmeters. It also actively
keeps track of all current going in and out of the battery.

So really its the electric motor that acts as the
"charge controller".

Umm, no, it's the computer that's the charge controller. Adding your
own charger without an equivalently smart charge controller (we'll
skip the details of how you inform the computer that you've added
amp-hours for now) risks improperly charging the battery pack, and
potentially damaging it.

[Dunno why Honda doesn't just make a flexible amorphous panel built
into the roof a (say) $3000 option...]

 

[Damn Dan]

A computer monitors the state of
the battery using temperature sensors and voltmeters. It also actively
keeps track of all current going in and out of the battery.

So really its the electric motor that acts as the
"charge controller".

Umm, no, it's the computer that's the charge controller. Adding your
own charger without an equivalently smart charge controller (we'll
skip the details of how you inform the computer that you've added
amp-hours for now) risks improperly charging the battery pack, and
potentially damaging it.

[Dunno why Honda doesn't just make a flexible amorphous panel built
into the roof a (say) $3000 option...]

Heh, sorry, in my attempt to simplify the system so I wouldn't bore anyone
reading my post, I guess I skewed what I was trying to say. The eletric
motor is not actually the charge controller, but it is the final player
between the motor and the battery. There's no more circuitry that limits
the current into the battery once it's left the electric motor. The Battery
Control Module along with the Motor Control Module are actually the brains
behind the charge controller. They decide what condition the battery is in
and then control the electric motor to send power in of the battery or
receive power out.

You've raised a good point about informing the computer about the change of
state of the battery during the recharge. I purchased the Electric Repair
Manual for my car to tackle exactly that problem. Luckily, the BCM has a
full I/O description in the manual, so it shouldn't be too hard to use a
little bit of power to turn it on during the charge. But I'm not entirely
convinced it's necessary yet. I'll probably try charging the battery once
without waking up the BCM and see what happens. The worst it'll do is
recalibrate the battery (drain the capacity to 20% and then recharge back to
80%), and that's not a big deal.

I'd be nice if Honda did provide some kind of solar device or at least an
external charger... that'd make my life a lot easier. But to be honest, I'm
having more fun and learning more about my car this way then if I could just
go to the store and buy it.

 

[Watson A.Name - \Watt Sun, the Dark Remover\]

[snip]

Honda's "charge controller" for the Insight battery is not a typical
controller in the usual sense of the word. A computer monitors the state of
the battery using temperature sensors and voltmeters. It also actively
keeps track of all current going in and out of the battery. Using that
data, it makes an estimation about the state of the battery and informs the
electric engine about its condition. The electric engine then sends power
to the battery (to recharge it, if it is ok to charge) or receives power
from the battery (during assist mode, if it is ok to load) based on the
state of the battery. So really its the electric motor that acts as the
"charge controller".

THe scary thought here is that what if the Honda can't account for the
extra charge you're putting in? In other words, it thinks the battery
is discharged when actually it has been topped off by your solar panels.
And then it tries to charge the battery even more.

 

[Florian]

(snip)

I'd be nice if Honda did provide some kind of solar device or at least
an external charger... that'd make my life a lot easier.

Wouldn't an external charger be the way to go in any case? In other
posts you've mentioned that 1) driving to work consumes 10% of the
battery charge, and 2) when the battery goes below 50%, the car starts
recharging it, reducing your gas mileage. From this, it seems the solar
panel is an unnecessary complication -- if you can make a round trip
commute to work with only 80% loss, you're not triggering the recharge
cycle, so why not just top off the battery at home every night from a
wall socket and forget about fickle and expensive solar panel?

(snip)

 

[Damn Dan]

[snip]

Honda's "charge controller" for the Insight battery is not a typical
controller in the usual sense of the word. A computer monitors the state of
the battery using temperature sensors and voltmeters. It also actively
keeps track of all current going in and out of the battery. Using that
data, it makes an estimation about the state of the battery and informs the
electric engine about its condition. The electric engine then sends power
to the battery (to recharge it, if it is ok to charge) or receives power
from the battery (during assist mode, if it is ok to load) based on the
state of the battery. So really its the electric motor that acts as the
"charge controller".

THe scary thought here is that what if the Honda can't account for the
extra charge you're putting in? In other words, it thinks the battery
is discharged when actually it has been topped off by your solar panels.
And then it tries to charge the battery even more.

Good point. I'm definitely going on faith that the many onboard sensors
(serveral voltage, current, and temperature sensors) will pick up the change
and react accordingly. Granted, the current sensors are useless unless I
power them while I'm charging. I'll keep that in mind, though.

I guess I'm being an optimist and imagining that I'll turn the car on after
charging it and voila, the SOC indicator will accurately reflect the
increased capacity. That sure would make me happy .