Seems to work very nicely and assuming the overnight test goes OK I will be happy to supply and fit them for UK owners. You can get the supplies in the US as well from same supplier, perhaps we could/should think about a bulk purchase? I did discuss with the supplier in UK about price and possibly they could get it down to.
I am using the diodes in battery leads as before. I now need to find a nice neat enclosure to fit them into L200mm x W150mm x H100mm. I'm also using a 33R 25W resistor in series with them to limit the charging current when battery is at a low voltage to < 500ma which brings it down to the capabilities of the psu's. As the battery voltage rises the current falls away naturally anyway.
For this first test I set three of the supplies to mimimum output voltage and adjusted the fourth so in series they provide 170V no load output. Might adjust that up a bit later when I see how current has dropped as battery voltage rises.
Seems like a nice cheap option. 4 x psus, 2 x 400V 3A diodes and a 25W 33R resistor.
Seb & Art seems we have a solution for you. e-mail me.
Peter
EDIT
Just ordered a couple of ABS matt plastic enclosures to try for the Charger
How do those hold up charging at their current limit. Also, can their current limit be lowered? I have considered switching from my Variac system, but would need one supply @ ~600ma or two supplies at ~300mA.
Peter,
The resistor may not be required.
The 48V fixed supplies from meanwell will limit current to their max capabilities by pulsing the output, like a foldback limiter, when their 450MA max current is reached. After a few minutes of the fixed supplies pulsing, the pack voltage will rise to a level where the constant current supply will take over the current control. It is only a factor if the pack is pretty empty.
The supplies you have seem to have a similar feature.
uhtrinity,
The LPC-20 will regulate current to 350ma , and swing it's output voltage from ~4-48V to maintain the current. If you had 3- 48V fixed supplies that output 800ma+,in series with two of the LPC-20 in parallel, that should give you 700ma of constant current that will maintain the current over the top 4-48V.
The supplies run reasonably cool, as they are switching regulated, I just ran a charge on a pack in 85 degree high humity, and the supplies were just warm to the touch.
I am tinkering with a plug in automatic discharge system that will watch each voltage tap and terminate the discharge when a cell begins to drop out.
Yes they had a pulsing output when I did not include the resistor due to excessive current.
But I didn't like that, as it is surely bad for the supplies to be operated in that way.
Having the 33R resistor means they are operated within there capabilities and generate less heat, which will be important when they are enclosed in a box. They started out at about 460ma charge with battery at 155V this has now dropped to 250ma at 165V after several hours.
Others can experiment of course. I'm going for a simple reliable solution I can churn out fairly easily and cheaply.
I'm going to adjust the V outputs on each to 44V to share the load equally. Giving a total output of 176V
The constant current led supply pretty much keeps the other supplies out of over current,unless the pack is less than 125V, but it looks like you are not using one of those?
The resistor is wasting lots of power that the CC led supplies easily take care of at better than 80% efficiency.
Why not use one of those instead of the 4th 48V supply like my original design? The cost is nearly the same.
I don't agree that it's wasting lots of power. The resistor is not mounted on a heatsink and I can still hold it. Probably burning off a few watts only. I prefer the standardisation and the fact I can fit four of these tiny supplies in a nice black ABS box. I've ordered two boxes as well to fiddle with. I'll take some power readings to see how many watts it is using and work out effciency in/out.
EDIT
Just checked them Mains consumption is 50W according to my meter for a 220ma 167V dc output into Battery.
So 50W input power translates into 36.74W output power. 73.5% effciency.
I've just ordered another 8 of these psu's to make up a total of three grid chargers, one for me and two for customers
You were looking at the efficiency at the end of charge, a pack that is discharged to 20% can be down in the 130-140V area.
If the supplies are set at 170V,and the pack you try to charge is down to 130V, there will be 40 volts across the 33 ohms, the pack will try to draw 1.2A, and the supplies will go into foldback regulation. If the supplies could put out the current. You would dissipate 47watts in the resistor alone.
The constant current switcher keeps the current the same throughout the charge, and will do so with the pack at any voltage between 127 to 170V.
Just seems like a better solution to me?
I noticed the meanwell site states "does not sell retail"... I take it some folks get them sold to them retail anyway, but if there's enough interest around the York, PA area in the US I'd be happy set up a group buy for a quantity discount.
I seem to be finding ways to discharge the battery pack without having long enough trips to fully get the SOC back fully up yet, and it seems silly to not simply plug the thing in to recharge it at home, probably sustaining my 61 - 67 mpg (7 mile each way) commute average more easily in the process, if not exceeding it. It would only be an occasional full topping-off balancing charge, usually simply to get it back near the top of the expected SOC range.
I would think the current limiting unit would be a good inclusion, to allow stable and non-overloading current and voltage regulation.
I'll see how it works for the time being. I appreciate all the comments. I got an ABS black nice case for it today which seems to fit those 4 psu's i'm using quite well. I'm going to add a thermal fuse inside case on input to go off at 84C and a 1amp fuse on output. Probably use flying leads in/out for these first two examples I'm building. HV out connector will be fitted with shrouded plug. Insight will be fitted with shrouded socket and diodes near bat terminals. Might extend one of the 4 psu leds to protrude through case as mains indicator.
A couple of pics of my first assembled grid charger which will be installed in Seb's car later today. It's on burn in test at minute.
Well the socket for the charger will be installed into the car, the charger itself can sit where you like. It does not need to be carried around with you.
Let me know how your thermal fuse works out for you.
We have numerous environmental test chambers at work, and some of the older one's used to have thermal fuses that open circuit at 200C or so by design.
We ended up having to remove them and use another method to detect over temperature, since the thermal fuses did not prove to be very reliable. Even the chamber manufacturer no longer uses them due to their instability.
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