I recently came into a large supply of new MeanWell, (Mean Well), switching power supplies.
Enough, and cheap enough, that I don't mind sacrificing a few on the alter of R&D.Specs:
Mean Well S-150-24
150w max continuous output
24V - adjustable from 19.5V - 29.8V (As tested on 2 samples)
6.5A max continuous output@24V -
24V x 6.5A = 156W
No fan - Open grid shell - convection coolingFactory SpecsProblem:
Rated at 6.5A, but will surge-sustain much higher, burning componentsSolution:
Restrict the amp output -
The "R33" resister is the key to regulating amperage.
For testing purposes, I soldered 2 wires of a 2s balance plug to the ends of the R33 resister.
Then plugged a multi-turn 2K, (then as high as 10K), Pot (potentiometer) into the balance connector.
Then I lowered the voltage to minimum and applied "load".
Removing and measuring the pot's ohms at each 1/2 amp mark.
(Pot must be removed to measure! "In circuit" it is laid parallel with 2 other resisters.)With the following results:
8.5A = OEM
8.2A = 10K
8A = 8.1K
7.5A = 4.6K
7A = 3.3K
6.5A = 2K
6.0A = 1.65K
5.5A = 1.3K
5.0A = 1K
4.5A = .81K
4.0A = .63KWider Amp adjustment:
Disconnect, or remove R33 & R38.
Replace with adjustable" pot"
Working with 12.6V LiPo pack through inverter
Amps ...... Ohms
1A ... from ... 70 ohms
2A ... from ... 175 ohms
3A ... from ... 287 ohms
4A ... from ... 392 ohms
5A ... from ... 500 ohms
6A ... from ... 610 ohms
7A ... from ... 715 ohms
8A ... from ... 855 ohms
9A ... from ... 920 ohms
10A .. from .. 1050 ohms = 1.05 k
11A .. from .. 1140 ohms
12A .. from .. 1293 ohms
13A .. from .. 1357 ohms
14A .. from .. ? ohms
15A .. from .. ? ohms
16A .. from .. ? ohms
17A .. from .. ? ohms
18A .. from .. ? ohms
19A .. from .. ? ohms
20A .. from .. ? ohms
A 2K pot should provide a, near to, 20 amp capability.
A 300% amp increase!
Need lower voltage high drain rig to determine higher amps.
* Not precise ... used analog amp meter.Widening the voltage range:
By changing the value of the Voltage pot, I was able to lower the output range substantially.
1K = 19.5 - 29.9V (oem)
2K = 15.1 - 29.9V
5K = 9.8 - 29.9V
10K = 6.6 - 29.9V
20K = 4.6 - 29.9V
100K = 2.9 - 29.9V
As I will demonstrate later, there can be great advantages to lower voltages.
Note! The higher value pots (100K etc) only allow a very "coarse" adjustment at the high voltage end. Harder to fine adjust.Raising Voltage?
Not tested ... or recommended!
This model has 35V caps ... a fairly strict limitation! = 150 Watt! =
To be safe and effective, amperage should be adjusted as voltage is altered.
Volts x Amps = Watts
Watts should equal, or be slightly below, 150 watts.
29.4V x 5.1A =150W - 7S Li-ion - 2 in series *
= 58.8V 14S Li-ion
28V x 5.35A = 150W
27.3V x 5.5A = 150W - 2 in series *
= 54.6V 13S Li-ion
26V x 5.77A = 150W
25.2V x 5.95A = 150W - 2 in series *
= 50.4V 12S Li-ion
24V x 6.25A = 150W
22V x 6.81A = 150W
21V x 7.14A = 150W - 2 in series *
= 42V 10S Li-ion
20V x 7.5A = 150W
18V x 8.33A = 150W
16V x 9.4A = 150W
14V x 10.7A = 150W
12V x 12.5A = 150WNote
- modding below 11V demonstrated occasional ... "unreliabilities".
10V x 15A = 150W
9V x 16.67A = 150W
8V x 18.75A = 150W
7V x 21.42A = 150W
6V x 25A = 150W
5V x 30A = 150W
4V x 37.5A = 150W
3V x 50A = 150W
2V x 75A = 150W
Yeah ... I'm gonna try pushing everything to the limits ... and then a little further!(Will test to confirm) *In Series
"In series" is when the neg of one power supply is run through the positive of another - combining their voltages.Important!
When run in "series" the DC "negative" must be isolated from the 110AC negative ... on all but the primary unit!. Otherwise, the DC positive from the primary unit will "short" through the AC negative on the secondary unit.
'The negatives are usually connected through the "ground".
3 points of "ground" to remove.
The external ground - terminal 3.
The green wire, at F1 near terminal 3.
The bottom of the circuit board, under screw hole next to fuse. (Cut circuit traces, or insulate with ... fiber, or nylon, washer and screw?)
The case can be "properly" grounded by connecting the AC ground wire to the removed green wire directly.Lowering Voltage
Lowering voltage could take advantage of higher amperage.
Without removing components, amperage is regulated below ~8Amps.R33, combined with it's neighbor R38, have a measured resistance of ~865ohms.
Removing both and replacing with a 2K pot allowed me to produce a 14V 10A supply.
(1.1K setting. Will compile a chart for higher amperages.)
14V x 10A = 140W
14V 10A in series with with 2 paralleled 28V 5A = 42V 10A 10s charger.Fan Mod?
With a listed 85% efficiency, the 150w power supply should produce a maximum of 22.5w of heat.
Considering the large heatsinks, I would think this to be adequate, so long as convection (air) is not restricted. Component View