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Discussion Starter #1 (Edited)
I did some research into HV CC power supplies, and think we can get off the shelf components to make one for less than $100.

The supply would be made with:

LPC-20-350---------$16.57
LPC-20-350, Mean Well LPC-20-350
Constant current supply

three RS-25-48-----$20.16-----$60.48
RS-25-48, Mean Well RS-25-48
Adjustable fixed voltage

one RS-15-12-------$18.14
RS-15-12, Mean Well RS-15-12
to run the battery fan


All supplies are universal AC inputs 85-260VAC, have isolated outputs.
The outputs of the three fixed 48V and one constant current supply would be connected in series to yield a 148 to 192VDC 350MA CC supply for the charging/balancing supply, and the 12V supply connected to the battery cooling fan.

The TRC people only sell to OEM, but I could order them through my business.
Of course if we did a group buy, the pricing could be better.
Output fuse and diode, and some leads and power cord, and we have a 350MA CC grid charger/balancer for just a bit over $100.

http://99mpg.com/Data/resources/downloads/gridchargerstuff/basicgridchargerv1.pdf
 

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Mike,

Keeping in mind that I'm an electrical idiot,

What would this be used for? Charging the battery overnight? Could it be used to restore a weak battery?

Thanks!
 

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Mike,

Keeping in mind that I'm an electrical idiot,

What would this be used for? Charging the battery overnight? Could it be used to restore a weak battery?

Thanks!
It would be used to keep the Insight pack from going out of balance and developing P1447 errors. You would simply top up your battery every month or so.
 

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grid charger

I the install is fairly simple, count me in on a group buy.

Kevin
 

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What would happen if you used this every night? Would it damage the battery?

In my daily drive I go about 120 miles but over a 9 hour period. What would happen if I had a 12 deep cycle battery with an inverter powering the power supply to keep the pack up while the car is at rest between drives? I have an inverter going anyway to keep my laptop alive all day.

Thanks,
 

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I would be interested in the charger as well, so please keep me in mind for a group buy.

I understand that your immediate selection in a power supply would be fixed at 350 mA, but if I could chose, my selection would be more like 200 mA or so, or at least one that could taper off at higher voltages. That way it wouldn't be quite so critical if I forget to disconnect at the proper time, or fuss with a timer to do the same.

As ogregev mentioned, my intent would be to use it once a month or so to keep the cells balanced, and maybe replenish things on an occasional heavy use day.

Jim.
 

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Discussion Starter #8 (Edited)
I will talk with the TRC engineer, to see if he feels this would be safe, and then I will buy a set so I can build a prototype, and define some safe ways to tie it into the pack and bring out the charge port on a safe HV connector.
I can make battery fan connectors like I use for MIMA, that will allow plugging into the fan easily.

With the fan running, 350MA will be safe for days and would top off a pack in less than 24 hours.

We could use a simple 240V light bulb as a discharge load, and put in an automatic cycler, so you could leave it unattended for a weekend, and start off the week with a refreshed battery.
Another use would be to grid charge the insight pack with it so you could start most days with a full pack. a mini PHEV.

I just got this report from Allert in Holland: Who rebalanced a really weak pack.
See his users profile at the bottom of this page:
MIMA Users Page - MIMA Honda Insight Modified Integrated Motor Assist

"Allert said:
I just want to let you know that my battery is doing fine, I’ve made a trip to the Cote d’ Azur in France and drove almost 2000 miles.

Not one recall and better mileage than ever in the hills in France, battery capacity is what it should be and MIMA is very good in rolling hills. I did 85mpg on the whole trip and managed to get a little over 100mpg for a considerable distance from time to time."


This was after 2 cycles with 250MA


This charger will help cars that are having recalibrations frequently, and some that have an IMA code, but there will be others that will need a stronger cycling at the subpack level to bring them back. This is only for the full pack.
I will post a preliminary schematic on my website before the weekend, and do a blog on how to build it and how well it works. Then we can figure out how many we want to buy parts for.
This will be pretty simple to wire up, and if we stick with the 350MACC, no special components will be required.
A nice DIY project for the technically inclined. This supply will kill you just like the battery will, so don't try this if you are not qualified.
 

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The TRC engineer does not see any reason that this will not work, so I will order a set of power supplies tomorrow and build the prototype.
The price breaks for 10, 25, 50, pieces are pretty good, so this could be quite reasonable.
Mike, are you going to be able to detect full and stop charging?
 

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Discussion Starter #11
Ron,
We can do that, but that would add complexity and cost that may not be required. 350MA with the fan going will be a pretty gentle charge, and would not heat the cells or build up internal pressure for many hours after the pack is topped off. A built in digital or even analog volt meter will show when the voltage has stabilized at the end of charge, after it is stable for an hour or so, we switch to the discharge cycle with a light bulb, could be monitored with the same meter, and when the voltage drops to about 1V/cell, we would switch back to the topping charge, wait till it again stabilizes, and off you go.

If we wanted a fully automatic system, a small microcontroller could look at the terminal voltage, determine when the voltage has been stable for say 30 minutes, and automatically switch to the discharge. The number of cycles could be set, and when the cycles were complete it would turn off and set an indicator.

More components more time and more cost.
I have a lot of other projects that I need to be working on, so I am thinking that the simple totally manual system should do the job. Add a cheap programmable wall plug timer, if over charging is a concern.

Even the discharge half of the cycle may not be required.
The company does not have the RS-25-48 in stock but will be recieving 100 next week, so I will not have the parts in hand till the end of next week.
 

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Sounds good Mike.

My Insight was acting strangely after 3 weeks of non-use.
As mentioned before, I parked with a full SOC.
When I came back and started up, I still had full SOC showing, so the car would not background charge or take much regen. But in reality, I think the SOC was really low, as I could not get more than 1 second of assist either.

The car would NOT recal during several short trips, and disconnecting the 12v battery did not help either.

I decided to take a long trip and see what happend. After about 40 miles of highway, the car did a recal and slow recharge, and I drove 1000 more miles, and the pack is back to normal. I now get at least 10 minutes of 50% assist, and the SOC goes the entire range of all 20 bars.

I could use something safe for 3 weeks of plug time. Or, I'd set it on a daily timer to run it for 4 hours per day for my extended garage periods, or whatever the "experts" recommend.

:)
 

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Gents

I'm a little concered about the discharge cycle mentioned here. I appreciate it's not part of the project at present but it is being discussed.

Assuming we use the low current grid charger to top off an equalise the pack, then using some sort of discharger without some quite sophisticated monitoring of the pack voltage could easily lead to a reversed cell. Just discharging to say 1v per cell or (120v) assumes all the cells are of equal capacity. Which is almost certainly a false assumption.

Draining the cells with a 100w light bulb is a pretty low current discharge and if a/the weaker cell/s reach empty first they/it could be reversed before the pack reaches whatever nominal cut off voltage you/we select, as the strong cells maintain a false high pack V.

Or am I overly pesimistic?
 

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Discussion Starter #18
My reasoning is that if the pack is brought to 100% SOC and held there for an hour or so before the first discharge, the cells should be nearly matched at 100% SOC at the start of the discharge cycle.
While there is a slight possibility that a cell could discharge to 1V much more quickly than the others, it is more likely that the full charge had already balanced the cells enough so it should not happen?

This is why the process needs to be tested carefully.

Even Jims subpack level breakout with a monitor on each tap can still let a single cell reverse if it is out of balance enough, since we do not have the ability to see each cell.

A grid charge followed by a full MIMA discharge, repeated several times may be safer as the packs built in cell reversal test are still in place?
First lets work out the charging, then we worry about the discharging.
 

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Peter,

If I were to perform this cycling on my battery, I might be inclined to:

1) Charge fully to 100% and hold as Mike mentioned
2) Discharge to a known 50% SOC (using voltage measurements; pick a value)
3) Charge fully to 100% again
4) Discharge to 40% SOC
5) Repeat pattern

At some point, hopefully one could say "OK, now I can go down to 1.0 V per cell safely" and go for it.

The above would get the entire pack ready for an 'almost' complete drain cycle at some point in time. Does this sound reasonable??

Jim.
 
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