at 350 ma probably not, unless you live in the deep south and are trying it in the summer. But I would leave the lid open on the storage compartment and remove the "bucket" so air can circulate. I have regularly charged mine on the bench at 300ma and cannot feel any warming with my hand on the sticks.
__________________
Jim Isbell
2000, 5 speed, 250,000 miles
"If you are not living on the edge, well then,
you are just taking up too much space."
I just did 5 sticks At 350 MA, on the open pool table.
The charger was one of the LPC-20-350 with alligator clips. Can't get much easier than that.
The ambient temp was 68, and the subpacks in open air no fan were all at 90-96 degrees F once they were all in the topping zone.
In the enclosed pack, the central and top area will accumulate the heat, and cause a temperature gradient across the pack, so the top cells will be running at over 100F, and the bottom and end sticks will be much cooler.
The idea of grid charging is to charge all the sticks fully, which will bring many of them into the final charge/heat generating zone well before the weaker subpacks, so many hours of soaking in the heat zone will be required, with more and more of the energy turning into heat as more and more cells get into the topping/heat generating area.
The charge acceptance characteristics of the cells is quite different based on their temperature, with cool being better than hot, so while the cells will not cook at 350 ma without a fan, keeping the pack fan running, even at 6-9V provides all the air movement required to eliminate the gradient, and provide a more uniform charging experience for the cells.
randerson0248,
Thanks, the RS-25-48 just showed up, I will put it to good use.
I got the universal dual rate grid charger cranked up today.
It works pretty well. I have a rotary switch that selects from 6 different things to monitor.
1. real pack voltage
2. pack voltage /100
3. 700ma switch off setpoint
4. output current
two more positions available.
I can set the 700ma switchoff from zero to the max 260V, so the dual rate can be used over the full range.
The DVM is mounted to the box with velcro, so the meter can be unplugged and used for other things.
The 4-48 V supplies can each be turned on or off, so the charger can do anything from a single 6V subpack to a gen 2 prius at over 260V.
Turn on charger, turn on the number of supplies required for the battery, adjust the 48V supplies to the max voltage for the pack, while reading the voltage on the meter.
Connect to the battery, and the voltage will drop to the pack voltage.
Switch to setpoint monitoring, and set the 700ma switchoff point to about 162-168V (insight pack).
Press the high rate start button, and the yellow led turns red. When the pack reaches the switch off point, the 700ma supply turns off,led back to yellow and the 350ma remains on forever to safely top off the pack. Will have Insight fan adapter plug to put in series with the fan harness to run the pack fan.
Now I have to do some testing and draw up an aluminum chassis, and layout a PC board for the switchover control, and it will be ready to start making them.
Pretty slick Mike. Maybe someday we will be telling other people,"I knew Mike back when he was making custom pack chargers for us few Insight owners, before everyone had a DabCharge in their garage.
I like the switchoff point idea, definitely a great way to keep things simple and still accomplish a PHEV type setup. With a 1 amp current flowing to the pack, a voltage in the 160's *might* be premature, but would be safe. As long as the pack is well balanced, I figure that a trip point very close to the final charge voltage might be more approrpriate. Testing of course would be needed, I've got plans of adding a parallel pack or going to a lithium PHEV setup and if I stick with NiMh this is definitely a very cost-effective way to go. I'm going to have to look over your switchpoint parts to the schematic a bit more when I have the time to look up parts and understand them a little better to understand how this switching section of the electronics works.
op amp 101:
The LM324 is an operational amplifier, a common analog component.
op amps are very powerful analog amplifiers that can be used for many functions.
They can amplify AC or DC voltages from less than 1X to over 1,000,000 times.
They can act as high input impedance "buffer amplifiers", which can monitor a high impedance circuit without loading it down, and give a low impedance copy of that voltage that can drive a relay or led directly.
op amps are also useful to detect minute differences between two signals and switch from lo to high as the voltages cross each other, this is called the comparator mode.
Thousands of other circuit variations allow op amps to be the most versatile analog component.
I use the LM324 as a buffer and comparator in this circuit.
The battery/charger output voltage is divided by 100 as it passes through the 100K,950, and 100ohm pot. 200V will produce 2V which can be calibrated with the 100 ohm pot to be very accurate.
The divided voltage is passed through one of the 4 operational amplifiers used as a buffer amp. This duplicates the divided voltage on the buffer output with up to 20 ma of current available, while not loading the high resistance divider, as the buffer input impedance is way up in the megohm range.
The setpoint voltage which needs to be very stable, is held stable by the two precision voltage reference ICs which hold the voltage supply for the setpoint pot at exactly 4.88v even with the 12V supply operating over a 9-13V range(fan power).
The setpoint pot is a 2k 20 turn pot so the adjustment is smooth and repeatable over the full 270V operating range. The setpoint is also buffered with another of the op amp section.
The two buffered voltages run through identical 10k resistors to a third op amp which compares them and amplifies the difference by over 1,000,000, so only a few microvolts of difference will send the op amp output either to the + supply voltage or to ground.
The battery volts when charging starts will be lower than the setpoint, so the op amp output will be at the max + voltage, until the battery gets to just a few microvolts higher than the setpoint, at which point the op amp output will switch to ground.
The DPDT relay is what switches the 700ma CC supply AC power.
If the op amp output is high (Battery volts < setpoint), the transistor is turned on, but the relay is off, as the power for the relay coil is passing through a NO set of the relay contacts, so even though the circuit is ready to hold the relay on, we must "latch it on by momentarily completing the coil circuit by shorting across the NO contacts which will activate the relay and latch it in the on state. This allows both CC supplies to work in parallel. Once the battery volts gets to the setpoint, the op amp output will switch off, turning off the relay as the transistor switches off.
Once to CC drop-s to 350ma, the battery voltage will drop slightly, causing the op amp comparator to go high, but the relay in the off state has disconnected the path to ground through the contacts and cannot re-activate.
Hope that clarifies how it works.
I was just contacted with a bid of $13.67 for the Meanwell CC power supply. They could not quote the shipping but said it was just the UPS charge from Calif., no extras for handling. They are supposed to be sending me a quote by email. If anyone is interested, I can share it with you ...when I get it....
But at the same time I have just bought 10 of the 317 regulators for $6 (60 cents each) AND 10 each 2.4ohm 2 watt resistors for $3.50 which I will make into a current regulator that is switchable from 280ma to 560 ma with a single relay driven by a series resistance divider and a switching transistor with a second relay for a "latching relay" to keep it from backing up. There will be two 2.4 ohm resistors in series to set the current to 560 ma and the relay will short out one of them to drop the current to 280 ma. So for under $15 I can make 10 constant current regulators. This will go in series with 4 of the Meanwell 48V power supplies in series set to about 180V. Then it will automatically switch to the lower current when a preset voltage determined by the resistive divider is hit. The fans will be run from a 12V Wall wart that I got from the thrift store for $1 and it will connect to the AC pigtail so fans are on whenever the pigtail is plugged in. All automatic, in the battery compartment, with only a 115V AC pigtail out the back.
__________________
Jim Isbell
2000, 5 speed, 250,000 miles
"If you are not living on the edge, well then,
you are just taking up too much space."
Hi Jim,
I understand only a small part of what you and mike are writing here, but on the other side I am in a big need of a grid charger, my driving style does not give enough charging opportunities to the battery while the assist is eager to engage at any moment , so ima recals are very often.
Ii seems that it might be better if I can top off the ima pack every other day , if possible
Anyway I have a set of the 48v RS-25-48 power supplies and wish to make a grid charger , please count me in on a set of the rest of the parts needed for a charger...
__________________
2000 mt silver, 245k presently , 64.7 lt mpg (reset at 201k) mima #125 , grid charging from Dec 2010
I was just contacted with a bid of $13.67 for the Meanwell CC power supply. They could not quote the shipping but said it was just the UPS charge from Calif., no extras for handling. They are supposed to be sending me a quote by email. If anyone is interested, I can share it with you ...when I get it....
But at the same time I have just bought 10 of the 317 regulators for $6 (60 cents each) AND 10 each 2.4ohm 2 watt resistors for $3.50 which I will make into a current regulator that is switchable from 280ma to 560 ma with a single relay driven by a series resistance divider and a switching transistor with a second relay for a "latching relay" to keep it from backing up. There will be two 2.4 ohm resistors in series to set the current to 560 ma and the relay will short out one of them to drop the current to 280 ma. So for under $15 I can make 10 constant current regulators. This will go in series with 4 of the Meanwell 48V power supplies in series set to about 180V. Then it will automatically switch to the lower current when a preset voltage determined by the resistive divider is hit. The fans will be run from a 12V Wall wart that I got from the thrift store for $1 and it will connect to the AC pigtail so fans are on whenever the pigtail is plugged in. All automatic, in the battery compartment, with only a 115V AC pigtail out the back.
I ordered some of the LPC-20-350's for about $14.50 ea, but they are backordered for about a week.
On those lm 317's ..... you need the lm317hv. The LM317 will burn out if you try to span to great of a voltage range. I know as that was the first one i tried. I also tried the higher current version and they also burned out. The 317hv's have been running almost 2 years with no issues.
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