frodus
10 kW
I wonder how much for the 150W 15V output modules.... I could use some 10A's
a DC-DC to charge li-ion... GREAT!!
- Thread starter Doctorbass
- Start date
Well friends I am learning ...but somehow i was using the top view instead of the bottom view... i was hooking positive in to negative in. Duh...
any how i think i fried the one for sure ( that's why i guess a diode is a good idea Doc!)
i hooked one module properly and saw 3.39 output wonderful!
now i need a decent way of attaching the resistor and pot to the bottom of the modules but they are in epoxy or some sort of soft surface that would be a challenge for me what you all suggest breadboard?
any how i think i fried the one for sure ( that's why i guess a diode is a good idea Doc!)
i hooked one module properly and saw 3.39 output wonderful!
now i need a decent way of attaching the resistor and pot to the bottom of the modules but they are in epoxy or some sort of soft surface that would be a challenge for me what you all suggest breadboard?
I just received my BXB150 for testing. This is the FLT model, which I believe means that the RC pin is active low. So to turn on the unit, I connect the RC pin to the input's minus, and to turn off the unit I leave the RC pin unconnected. Is that correct?
Thanks.
Bill
Thanks.
Bill
Another question. Based on the pictures that doc posted, it looks like the heat sink on the bottom is electrically isolated from the DC/DC, is that also correct? I'm thinking about attaching all of the converters to one big sheet of of 1/8-inch aluminum, and then bolting that sheet to the car's hood and blowing a fan across it. Sound like a viable plan?
Bill
Bill
flip_normal
100 W
efreak said:
Glad to hear you got one working.
I'd epoxy or super glue a multi-turn preset pot to the underside (pin side) of the dc/dc and use the resistor as a wire to one of the pins. Don't forget to use a fuse on the +V input.
flip_normal
100 W
Yes.wjdennis said:
Yes.wjdennis said:
70 of these 150W dc/dc's working flat out at 85% efficiency will give off something like 1.5Kw of heat. You'll need a large sheet of aluminum and strong fan(s) to keep them below the over-temp cut-off point (though it's good that this is a non-latching protection circuit, IIRC). It may be necessary to use a heatsink with fins and position the converters so they aren't placed too close together. I guess you'll just have to try it and see.wjdennis said:
How are you doing low voltage cut-off? Is it at the cell level?
Undervoltage detection:
I currently have a LM431 with its Ref pin tied directly to cell positive. When the cell drops below 2.5V, the LM431 turns off, which allows current to flow through an opto. The opto outputs from all cells are paralleled, illuminating a red LED on the dash when one or more cells drops below 2.5V. Pretty crude. I've been watching the following thread with interest, and may be building some of these:
http://www.batteryvehiclesociety.org.uk/forums/viewtopic.php?t=1245&postdays=0&postorder=asc&start=190
By the way, only 35 of my cells are under the hood, not 70, so there'd be only 35 BXB150s on the sheet of aluminum. That comes to about 6 sq. ft. of aluminum at 1/8 thick, with 1.4 sq. ft of BXB150s attached: (2.4 in. x 2.4 in * 35) / 144 sq-in per sq-ft. I'm not sure how to do heat loss calculations, so as you say, I might have to just experiment.
Bill Dennis
I currently have a LM431 with its Ref pin tied directly to cell positive. When the cell drops below 2.5V, the LM431 turns off, which allows current to flow through an opto. The opto outputs from all cells are paralleled, illuminating a red LED on the dash when one or more cells drops below 2.5V. Pretty crude. I've been watching the following thread with interest, and may be building some of these:
http://www.batteryvehiclesociety.org.uk/forums/viewtopic.php?t=1245&postdays=0&postorder=asc&start=190
By the way, only 35 of my cells are under the hood, not 70, so there'd be only 35 BXB150s on the sheet of aluminum. That comes to about 6 sq. ft. of aluminum at 1/8 thick, with 1.4 sq. ft of BXB150s attached: (2.4 in. x 2.4 in * 35) / 144 sq-in per sq-ft. I'm not sure how to do heat loss calculations, so as you say, I might have to just experiment.
Bill Dennis
flip_normal
100 W
Case pin is connected to the steel plate on top of the converter. I leave 'em disconected.
Again thank you very much flip
what is the difference betwwen multi (12-- 25) turn pots and a single?
i was thinking about using a 20 amp fuse in line from the main + supply to all four + wires to the modules . or do you suggest me using 4 fuses 1 per module like Docs picture?
also i am using 14 gauge wires i hope that's good!
again i am static about getting any kind of cuurent out of these modules the rest seems easy some how thanks to all the help provided here.
in measuring the back of the flatpack 2 i noticed that it would be a rather tight fit for 10 of these modules.
I have 2 of the 4 channel Gary's lvc boards to be incorporated into the battery packs as well .
Thanks a lot
what is the difference betwwen multi (12-- 25) turn pots and a single?
i was thinking about using a 20 amp fuse in line from the main + supply to all four + wires to the modules . or do you suggest me using 4 fuses 1 per module like Docs picture?
also i am using 14 gauge wires i hope that's good!
again i am static about getting any kind of cuurent out of these modules the rest seems easy some how thanks to all the help provided here.
in measuring the back of the flatpack 2 i noticed that it would be a rather tight fit for 10 of these modules.
I have 2 of the 4 channel Gary's lvc boards to be incorporated into the battery packs as well .
Thanks a lot
The BXB150's spec is 150W (5V at 30A). But I've read doc's comments here that they will supply 39A at a lower voltage. Why is that? I thought that the limiting would be on amps, not on watts. Are they really limiting the watts? If they're limiting on amps, I'd expect them to regulate to 30A, regardless of the voltage. I hope that if I set them to 3.3V, they're not going to put out 45A? Or does the 39A have nothing to do with voltage, but simply that they supply more than spec?
Bill
Bill
flip_normal
100 W
more turns = more acurate setting. 12 should be fine.efreak said:
I'd think Doc knows best, ie. one fuse per coverter. 14 gague is good 5 amps no problem. How many watts are your converters rated for?
Try putting a 12V car headlamp bulb across the outputs to check for output current. If it lights the bulb then it's working. Don't forget the sence wires if they're needed.
flip_normal
100 W
The max amps I see (charging 50Ah of 5 parallel Headway 10Ah cells to 3.65V) is 37A. It should be easy enough to quicky test how they behave with your larger Thundersky cells, just hook one up to a partly drained cell (assuming you have a way to measure the high-ish current that is). When I was testing these with a load resistor the voltage would drop off rapidly (to ~ 2.1V) if I tried to pull more amps from them. As the cell voltage reaches the set charge voltage then the amps drop off. I think that 5V 30A is the optimum for these; at 3.3V I doubt you'll get the full 150W output.wjdennis said:
i tried a 100k ohm resistor and a 10k ohm single turn pot. and the reading is between 3.53 volt to 3.58 so iam gonna need some more resistance i need a multi turn with some more kohms. perhaps 30 kohm
these modules are 66 watt
and a fuse per
time to owork on the main charger soon although this could work for a smaller pack or..
these modules are 66 watt
and a fuse per
time to owork on the main charger soon although this could work for a smaller pack or..
frodus
10 kW
I started another project (the SLA solution is being tested now... works great at 5A/battery).
This time, I wanted to build a cheap 4-cell 26650 cell charger.
The cells are 3.2Ah 26650 3.2V and can be charged at 1C (3.2A).
I have a 48V power supply, and 4 Vicor 48V -3.7V @ 74W(20A) DC-DC converters. How do I control current? I know I can't charge them at 20A, so how would I charge them? I'm just not 100% sure on how well these work with Lifepo.
Doctorbass?
Do I just set them at 3.7V and let them go? or should I parallel more to get the whole pack to charge at 1C (like 6 in parallel for 3.3A each)?
This time, I wanted to build a cheap 4-cell 26650 cell charger.
The cells are 3.2Ah 26650 3.2V and can be charged at 1C (3.2A).
I have a 48V power supply, and 4 Vicor 48V -3.7V @ 74W(20A) DC-DC converters. How do I control current? I know I can't charge them at 20A, so how would I charge them? I'm just not 100% sure on how well these work with Lifepo.
Doctorbass?
Do I just set them at 3.7V and let them go? or should I parallel more to get the whole pack to charge at 1C (like 6 in parallel for 3.3A each)?
powermed
10 W
- Joined
- Jun 22, 2008
- Messages
- 80
Hi Travis,
No onboard way I know to adjust current on these vicors (there might be one, but I've never tried).
Someone confirm my math...A simple method is to multiply the number of cells (4) x the charge voltage you need (3.7?) x the max safe charge current (3.2) = the max wattage of the 48v power supply you should use. I get around 47 watts. You would likely be fine with 50+ since there's 10 - 20% loss of efficiency with converters. I'm thinking a 1 - 1.25 amp 48v power supply should do the trick. Check the output with an ammeter. There are a ton of cheap 48v supplies in that range on ebay.
z.
No onboard way I know to adjust current on these vicors (there might be one, but I've never tried).
Someone confirm my math...A simple method is to multiply the number of cells (4) x the charge voltage you need (3.7?) x the max safe charge current (3.2) = the max wattage of the 48v power supply you should use. I get around 47 watts. You would likely be fine with 50+ since there's 10 - 20% loss of efficiency with converters. I'm thinking a 1 - 1.25 amp 48v power supply should do the trick. Check the output with an ammeter. There are a ton of cheap 48v supplies in that range on ebay.
z.
frodus
10 kW
hey, yeah, these are going to be your converters.... did you ship them out yet?
I've got my eyes on a 600W power supply... we'll see
I've got my eyes on a 600W power supply... we'll see
powermed
10 W
- Joined
- Jun 22, 2008
- Messages
- 80
hi Travis, they're off via USPS...
Here's what should be a pretty good fit:
http://cgi.ebay.com/CISCO-48V-1-25A-AC-ADAPTER-IP-PHONE-CUBE-ROUTER-POWER_W0QQitemZ290292077018QQcmdZViewItemQQptZCOMP_EN_Networking_Components?hash=item290292077018&_trksid=p3286.c0.m14&_trkparms=66%3A2%7C65%3A15%7C39%3A1%7C240%3A1318
They are all over ebay, probably even cheaper than this.
Here's what should be a pretty good fit:
http://cgi.ebay.com/CISCO-48V-1-25A-AC-ADAPTER-IP-PHONE-CUBE-ROUTER-POWER_W0QQitemZ290292077018QQcmdZViewItemQQptZCOMP_EN_Networking_Components?hash=item290292077018&_trksid=p3286.c0.m14&_trkparms=66%3A2%7C65%3A15%7C39%3A1%7C240%3A1318
They are all over ebay, probably even cheaper than this.
frodus
10 kW
got them last night, thanks a ton.
As far as supplies... aren't those 3.7V converters 100W on the input? so they'd be just over 2A (2.08A) each. So for all 4 that I've got, I'd need 9A total to be safe.
As far as supplies... aren't those 3.7V converters 100W on the input? so they'd be just over 2A (2.08A) each. So for all 4 that I've got, I'd need 9A total to be safe.
powermed
10 W
- Joined
- Jun 22, 2008
- Messages
- 80
Hi Travis,
The way I've used them (without any problem) is to work "backwards" with the math. I haven't seen any evidence of the vicor's attempting to draw more current from the power supply than the power supply can deliver in order to charge my cells.
Not my area of expertise, but I suspect that charging a battery (at least a LiFePO4 or Prius NiMH) isn't the same kind of load as say a motor.
Bottom line, I source a power supply that can provide a safe amount of current - up to the charge rate of the cells to be charged - using the calculation method described.
The way I've used them (without any problem) is to work "backwards" with the math. I haven't seen any evidence of the vicor's attempting to draw more current from the power supply than the power supply can deliver in order to charge my cells.
Not my area of expertise, but I suspect that charging a battery (at least a LiFePO4 or Prius NiMH) isn't the same kind of load as say a motor.
Bottom line, I source a power supply that can provide a safe amount of current - up to the charge rate of the cells to be charged - using the calculation method described.
powermed
10 W
- Joined
- Jun 22, 2008
- Messages
- 80
I should add, although I've not tested it, I think it would be dangerous to have a DC supply that can power up the Vicor's beyond the C rate of the cells. Those Vicor's can supply up to 20 amps if there's enough power coming from the input side. That's a 2C rate for a 10AH cell should the cells be able to draw it during the charge.
frodus
10 kW
I'll be chargint multiple cells in parallel for now.
I'll work on something soon, I might just throw our BMS board on these (they control the current output for the vicors).
I'll work on something soon, I might just throw our BMS board on these (they control the current output for the vicors).
frodus
10 kW
WOOHOOOO!! I totally forgot... I bought a Unipower 1000W 48V power supply (85-264VAC)... it'l do 21A. I just need to hack the connector a little (its made to hook into a rack, have to "enable" it)....A couple of trimpots, some cable and a setup to charge 6 in parallel (DC-DC's are 20A, cells charge at 3.2A)... 24 cell charger good for a 12.8V @20Ah pack in an hour....
Then I can use this:
to drive these:
so I can charge these:
Then I can use this:
to drive these:
so I can charge these:
Doctorbass
100 GW
Good l;uck Frodus...!
I was always woried about these back bus connectors!! :?
I was interested to buy some on ebay... very cheap!! Rectifier are great psu but they all have to be connected to a main system bus to operate.. some would need some serie bit data to be activated some just need an enable pin to short to the gnd or 5V... some like my 27A 48V from "pioneer electronic" never started! I bought it on ebay one years ago and both 24V fan run when i plug it to the 120V.. but no output!... It have a kind of inhibit pin that need to have around 2.0V following the datasheet.. but I spend more than 20hour on it without any succed.. so i was refund from the saler without the need to send it back.. I bought another one drom meanwell for 150$.. operating on 120V and give full 1500W 50V 30A!!
Good luck with your's!
Doc
I was always woried about these back bus connectors!! :?
I was interested to buy some on ebay... very cheap!! Rectifier are great psu but they all have to be connected to a main system bus to operate.. some would need some serie bit data to be activated some just need an enable pin to short to the gnd or 5V... some like my 27A 48V from "pioneer electronic" never started! I bought it on ebay one years ago and both 24V fan run when i plug it to the 120V.. but no output!... It have a kind of inhibit pin that need to have around 2.0V following the datasheet.. but I spend more than 20hour on it without any succed.. so i was refund from the saler without the need to send it back.. I bought another one drom meanwell for 150$.. operating on 120V and give full 1500W 50V 30A!!
Good luck with your's!
Doc
