Overclocker
10 kW
Punx0r said:
is that a "Smun" psu? or another brand of meanwell clone?
Bulk charging via digital DC-DC boost Minghe BST-900W
- Thread starter Overclocker
- Start date
is that a "Smun" psu? or another brand of meanwell clone?
whereswally606
100 kW
Samd said:
Thanks Samd this totally explains weird behaviour I see when I use the esp120 at 54ish volts and the DCDC minghui at 54.40v. clearly the draw from the batteries dips the DCDC voltage below the esp120 supply.
Shouldn't be an issue when I go to 26s but for now at 16s its a bit concerning.
Overclocker said:
Just checked and it says "AC-DC" instead of "SMUN" but labels are otherwise identical.
Just about to order another - at the price of these things they're worth taking a chance on and just binning if you get a bad one.
Alan B
100 GW
I doubt it is worth getting another. They are all made with marginal components and inadequate quality control, probably not UL listed either.
Buying them encourages them to keep doing business this way, too, which is bad.
Get something higher quality, one of these could even burn down your house.
Buying them encourages them to keep doing business this way, too, which is bad.
Get something higher quality, one of these could even burn down your house.
Overclocker
10 kW
Punx0r said:
http://www.aliexpress.com/item/400W-36V-11A-Single-Output-Switching-power-supply-for-LED-Strip-light-AC-to-DC-LED/936022784.html
get a Smun. i've seen a lot of cheapo PSUs, the Smun seems to be better made
Too late, I already ordered one... Was in a hurry because I'm currently using a 12V telecom PSU, which means having to turn the current way down on the dc-dc converter to avoid overheating it and consequently painfully slow charging.
Overclocker
10 kW
Ykick
1 GW
Looks good OC...
bobc
10 kW
Looks pretty neat - You'll be using the built in fan for cooling ? I'd expect it to be enough, it can pull cold air in by sealing the lid round a fan 'hole' then put some exit holes over by the boost converter? Do keep an eye on temperatures, if you just shut the box as is it would probably get hot enough in there to start melting the box...
Overclocker
10 kW
thanks i just open during use
btw i did a simple mod to increase airflow over the fins
btw i did a simple mod to increase airflow over the fins
Ykick
1 GW
OC - I really enjoy your resourcefulness!
And thanks again for the great tip about reworking cassettes for my BBS02 ride!
And thanks again for the great tip about reworking cassettes for my BBS02 ride!
cerberpeter
10 mW
Anyone tried to beef up these "BST900"?
I will be trying to get it working on at least 500W output with 12V server power supply charging 20s Li-ion. I was experimenting and testing a bit and found that I would need much bigger inductor. With the stock one I manage to get only about 13 Amps on the input no matter what I do with the output or with the shunts
Very disappointing knowing that I have 70A on 12V...
So I tried putting 2 additional random inductors that I had in series with the stock one. It started to get quite noisy, but I manage to pull about 18 Amps on the input. The good thing is that it is not limited in current by the chip, but only the power components.
So my goal is to achieve at least 50A input and I think I would only have to do these several things:
- mount the mosfet on a CPU sink
- replace the STPS30150C with STPS80170CW
- make a huge new inductor and probably mount it under
- replace the 20A fuse
- beef up the traces
- maybe add more capacitance on the input and output?
I will be trying to get it working on at least 500W output with 12V server power supply charging 20s Li-ion. I was experimenting and testing a bit and found that I would need much bigger inductor. With the stock one I manage to get only about 13 Amps on the input no matter what I do with the output or with the shunts
Very disappointing knowing that I have 70A on 12V...So I tried putting 2 additional random inductors that I had in series with the stock one. It started to get quite noisy, but I manage to pull about 18 Amps on the input. The good thing is that it is not limited in current by the chip, but only the power components.
So my goal is to achieve at least 50A input and I think I would only have to do these several things:
- mount the mosfet on a CPU sink
- replace the STPS30150C with STPS80170CW
- make a huge new inductor and probably mount it under
- replace the 20A fuse
- beef up the traces
- maybe add more capacitance on the input and output?
Overclocker
10 kW
cerberpeter said:Anyone tried to beef up these "BST900"?
I will be trying to get it working on at least 500W output with 12V server power supply charging 20s Li-ion. I was experimenting and testing a bit and found that I would need much bigger inductor. With the stock one I manage to get only about 13 Amps on the input no matter what I do with the output or with the shunts
So I tried putting 2 additional random inductors that I had in series with the stock one. It started to get quite noisy, but I manage to pull about 18 Amps on the input. The good thing is that it is not limited in current by the chip, but only the power components.
So my goal is to achieve at least 50A input and I think I would only have to do these several things:
- mount the mosfet on a CPU sink
- replace the STPS30150C with STPS80170CW
- make a huge new inductor and probably mount it under
- replace the 20A fuse
- beef up the traces
- maybe add more capacitance on the input and output?
that's why i'm using a 36V power supply here. when i begin using a 63v battery i'll probably use a 48v PSU. boosting 12v to 48v++ is inefficient
the first thing i want to do is to improve the thermal resistance of the MOSFET. i noticed that the MOSFET heats up way more than the diode so i figured that we could improve the thermal resistance of the MOSFET by moving the pad to the diode instead.
what do you think?
bobc
10 kW
I'd have said that if you mess with the circuit you lose the expectation that it will work at all and all of the nice features like current measurement and amp-hours accumulation.
Why not simply buy 2 or 3 & wire 'em in parallel? I'd actually expect that to do what you want.
Why not simply buy 2 or 3 & wire 'em in parallel? I'd actually expect that to do what you want.
cerberpeter
10 mW
Personally I mess with the circuit because it is fun. I also think the Chinese design is not perfect and there is a room for improvement.bobc said:
Overclocker, I know it would be much better to use higher voltage PSU, but I just want to achieve that low voltage high current boost. It would be nice if it is possible, because this is 10 to 20£ for a server power supply + £15 for the boost converter + some sort of balancing + some modifications. All in all it would be powerful, cheap and relatively easy to carry charger, not just for me, but my friends that I got into the ebike fun.
Overclocker
10 kW
cerberpeter said:
well the Smun 36v i'm using costs $31
apparently boosting from 12v is simply inefficient no matter how well you design it. even the very good iCharger hobby chargers heat up and don't achieve max power when using 12v
bobc
10 kW
I just bought another; both main power semis are 150V parts 
shottky - STPS20150CT
FET - FDH055N15A
shottky - STPS20150CT
FET - FDH055N15A
bobc
10 kW
yes. needs a DC power source. A 12V SLA would just about do what you're asking - with a higher voltage source you'd get more output current
Further up this thread is a link to instructions for use of this converter
these are generally regarded as AC solutions/controls, so no
Overclocker
10 kW
bobc said:I just bought another; both main power semis are 150V parts
shottky - STPS20150CT
FET - FDH055N15A
i got another one too
Overclocker
10 kW
kocetoMR said:
i'm now using it to charge 12s, 13s, and 17s. using 36v power supply
12s and 13s no problem
17s: efficiency is not good. MOSFET heats up. i plan to get a 48v PSU for this
Overclocker
10 kW
kocetoMR said:
36V/ how amp?[/quote]
see page2 for pics of the Smun 36v PSU. also an aliexpress link
take note this BST900 is a BOOST converter as such it needs about 4v (i think) input to output voltage difference for it to comply w/ your set current limit. e.g. if your depleted battery pack is 38v and your PSU is 36v, even if you set a 4A current it will exceed it
since a 10s pack is 30v empty then it's not possible to use a 36v PSU. a 24v PSU will work OK w/ the 10s pack but will be less efficient at charging 13s
bobc
10 kW
To expand on overclocker's point:
at heart this is a basic boost converter.
It has a DC source and a DC output.
When it is "boosting" the DC output is controlled. Otherwise you get slightly less than source volts at the DC output limited ONLY by the fuse on the PCB. Whether you like it or not. Whether it is switched on or off.
So be careful using it to charge really flat batteries.
You'll get better efficiency with a higher source (input) voltage but always be aware of the above limitation.
As I hinted above, I'm using a bank of old 12V lead acid batteries as the power source. I'm charging to about 60V so charging current is limited by input current limit to about 1.8 to 2A. Also as hinted above it is pretty inefficient with such a large boost ratio (say 70% ish). The battery bank would happily supply hundreds of amps into a low voltage load through the boost converter, even if it were switched off.
My alternative charging power source is a cheap mains 48V switcher - this is a 5A supply so I've set the (boost converter) output current limit to 3A; this gives safe & cool operation on both power sources without having to alter any settings.
at heart this is a basic boost converter.
It has a DC source and a DC output.
When it is "boosting" the DC output is controlled. Otherwise you get slightly less than source volts at the DC output limited ONLY by the fuse on the PCB. Whether you like it or not. Whether it is switched on or off.
So be careful using it to charge really flat batteries.
You'll get better efficiency with a higher source (input) voltage but always be aware of the above limitation.
As I hinted above, I'm using a bank of old 12V lead acid batteries as the power source. I'm charging to about 60V so charging current is limited by input current limit to about 1.8 to 2A. Also as hinted above it is pretty inefficient with such a large boost ratio (say 70% ish). The battery bank would happily supply hundreds of amps into a low voltage load through the boost converter, even if it were switched off.
My alternative charging power source is a cheap mains 48V switcher - this is a 5A supply so I've set the (boost converter) output current limit to 3A; this gives safe & cool operation on both power sources without having to alter any settings.
