grid charger/balancer

[Mike Dabrowski 2000]

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.

[SteveChicagoSC]

I like the idea of starting the day with a full charge with a mini PHEV method!! I'm definitely interested.

[Waynetc]

I Like! Count me in Mike.
Wayne

[Hybrid-Battery-Repair]

Originally Posted by Mike Dabrowski 2000

Ron,
We can do that, but that would add complexity and cost that may not be required.

You know why I want them. I've got to keep packs charged on the shelf.

[Mike Dabrowski 2000]

We still need to source a nice safe male/female connector, and a 1A 200VCD in line fuse and holder.
Anyone want to look into that?
I will have the power supplies in hand first week in May.

[gpsman1]

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.

[retepsnikrep]

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?

[Mike Dabrowski 2000]

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.

[3-Wheeler]

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.

[rccrashed]

I would like to get in on a group buy on this also.
Thanks
Ed Mc