MN Driver,
Thanks for your good insights from your testing.
I have been terminating the max temp at 90F to stay on the safe side, but remember seeing 120 a few times in the car. I suspect that my pack has seen more complete cycles in the car than most packs, but it was encouraging to see #9 come back from a pretty bad initial state.
I know that Ron will run cycles on the sticks until the AH does not further improve, so I expect that #9 will need another cycle or two to get as reconditioned as it can.
It was such a nice day yesterday that I had to do some outdoor projects, but hope to get back to the testing today.
I know the Meanwell CC power supplies can be put in parallel, but can these RS-25-48 CV supplies be put in parallel too so that two would go together to act similarly to having one RS-50-48 supply in its place and then series the three CV supplies? I might buy two of those ebay lots if this is the case since these probably aren't going to be around at this price forever.
The constant voltage supplies do not work in parallel very well, as even a small voltage difference would send current between the supplies.
You would be better off putting the whole 350ma grid charger in parallel with a second 350 ma grid charger, so the CC supplies ability to adjust output voltage would tune the voltage of each so they would work nicely in parallel to put out 700ma.
Tune the open circuit voltage of each supply to about the same voltage, put the two series strings in parallel and you are good to go. Those supplies sound like a good deal for a 350ma supply. Unfortunately my dual rate charger needs a bigger 48V supply, and like I explained above, putting them in parallel without a CC supply to do the balancing on each string is not recommended.
The charger will have a relay that will be manually latched on at the start of the charge to apply power to the 700ma CC supply.This along with the 350ma CC always on supply will yield ~1A.
When the voltage across the battery during the 1A combined CC charge reaches an adjustable voltage setpoint, the 700ma relay drops out, and the remaining 350ma CC supply will remain on to top off the pack.
I have been working through the 20 subpacks from my old pack, and am seeing that a long soak at 350ma is required to really get the cells all to the full charge point.
At 350ma, fan running, and you can stay there for many hours, allowing the weaker cells to catch up. http://99mpg.com/Projectcars/mimapackwhack/
I will include a cheap DMM for setting the switch point, monitoring the charge current, and watching the pack voltage. - Harbor Freight Tools - Quality Tools at the Lowest Prices
I am also building a 5A dual rate charger, and will use 3 of the Meanwell S-250-48 (48V 5.2A), with 4 of the LPC-60-1050 CC supplies in parallel with a LPC-20-350. The four 1050ma CC supplies will be latching relay controlled with a settable voltage as in the 1A dual rate unit, but will get there 4 times faster.
"Meanwell RS-25-48 Switching Power Supply 25W, 48V, 0.57A"
That would give a 570mA charge rate, not 350mA, right? Which would mean you should be able to get a full charge in 12 hours or so.
MeanWell's largest RS-series power supply appears to be the 3.3A RS-150-48, $45 from Jameco.
Mike, how/when does your dual-rate charger switch from its fast rate to the 350mA rate?
I had to read the site and this thread a few times myself because I was a little mixed up to. The power supplies can provide 570mA but they are constant voltage power supplies so they need to have their current limited because they won't do it themselves, instead they would overload and trip themselves off and would provide more than 570mA for the short period before they trip, possibly enough to cause some damage to the pack if the power supplies were larger or the overload goes well beyond their output rating before tripping. The charge rate comes from the constant current power supply that is in series with the other 3 constant voltage power supplies. Since they are in series the 350mA constant current supplies limit the current to the 350mA rate which is low enough to allow overcharge to not damage the cells provided that it isn't left on for too long after the whole pack is charged up. To have the higher rate, he takes the constant current supply that he has and connected it with another constant current supply that is rated to provide 700mA. So he can turn them both on and get 350+750mA = 1050mA (1.05 amps), or just one and get the 350 or 750mA.
...but to incorporate a larger constant current supply to be able to use higher than the 350mA you would need larger than the 570mA CV power supplies, or a daring nature to overload them to 700mA and possibly burn them up which could take the whole car. I checked and the CC power supplies come in 350mA 700mA and 1050mA for the ones that can provide up to 48 volts.
I was thinking of skipping the .57 amp supplies and going bigger but for the price I'll stay put and just get a 350mA CC supply for now to go with the cheap $20 ebay 4 pack. At 350mA they can more safely balance an out of balance pack but if I choose to go with a booster pack(or two), I might upgrade and get a 1050mA CC supply or two and larger 48v CC supplies when the time comes as long as I figure out the latching circuit that Mike is working out to drop it to 350mA to finish the charge safely. If I end up with a lithium PHEV system, depending on what I run into, I might work out an appropriate charger with these as I could setup a relay ramp-down for the current and termination when the pack reaches max charge voltage. Might be too much work though considering that ready made custom voltage 1500 watt chargers can be had for around $400 and I could work it into a BMS that would cut it off if something went awry with the charger.
I use the RS-50-48 supplies on the dual rate universal charger,which are rated at 1.3A, so the combined 700 and 350MA CC when operating in parallel are still safely within the rating of the 48V supplies.I use 4 48 so I can charge prius and civic packs as well as the Insight II.
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