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Dec 27, 2017, 09:38 AM
Nose down, you're gonna stall
rowdyjoe's Avatar
Quote:
Originally Posted by feathermerchant
If you slow the fans down, be sure to not load the power supply fully. It will overheat.
I an lucky and we have power at the field. I arrive at the field with batteries at storage then set them up to charge and unload and assemble airplanes. By the time I am done, I have 4 or 5 batteries ready to go.
Also be real careful charging indoors and NEVER leave the charger unattended.
Same here. Thunderbird field has power at just about every pole and I don't charge until I get to the field. I wasted money over the years learning the hard way about battery care/storage charge. None burned, just ruined by improper care. Now that I've "graduated" to high mah 4s, 2x4s, & 6s batteries, I needed an accurate, higher power, charger to protect my investment and speed up the charging process.

Roger on the charging safety.

BTW ....I've learned a lot about battery quality, etc. from the "Battery Load Test Comparisons" thread here on Groups (https://www.rcgroups.com/forums/show...risons/page349). Great info.
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Mar 05, 2018, 01:15 PM
Registered User

Do I float the grounds on both psu' s in series for 24 v?


Hi feathermerchants.
I've read (almost all) of the build pages on the site.great info on there from yourself and others.
I'm just about to receive two 600 dps psu.i want to connect in series for 24 v out put.
Having done a lot of reading of a couple of different sites which I trust, I seem to be getting conflicting info.(or maybe it's just me.,.)
Anyways, on rchelicopterfun.com, the server build has the first psu DC ground floated and then the DC-ouput is grounded to the case useing a metal tab or piece of wire,hooked up to the duel banana terminal on the outside Then if you want to connect another unit up to it for 24v ouput,the second one has the DC ground floated only(not grounded on DC -output to case with tab or piece of wire. )
Now on this site and the build forum I've been reading, here on the RC groups, it is saying that you only need to float the DC ground on the second and subsequent psu that are hooked up in series or parallel to the first unit. Nothing about a grounding tab/wire from DC- ouput to case.

So I'm not 100% sure on which way to do it,...
They both seem right. The grounding tab on the first units DC-ouput does make sense to me as if there was ever a fault and high voltage somehow got onto DC side,the DC ouput is grounded to case which is Earth grounded through the AC side, and therefore won't damage the charger .
I apologise if this is a silly question, I'm just want to do this safely and not destroy an expensive charger.
Thanks in advance,and a million thanks for all the info on the build thread that you contribute.it was your info that made it possible for hundreds/thousands to build there own power supply,safely and cheaply.
Kind regards
Ben
Mar 05, 2018, 01:44 PM
Nose down, you're gonna stall
rowdyjoe's Avatar
Ben,
I'm not Feathermerchant but, with his coaching, I completed my conversion a couple of months ago. You need to float the ground on only one power supply. They work great.

RJ
Mar 05, 2018, 02:55 PM
Registered User
Thanks for quick reply RowdyJoe.that was quick.
So I'm taking it from that ,you didn't do anything with the first supply's DC ground-you just left that alone, and done the the other mods necessary ( ribbon cable 1,2,3,4,5, to ground etc) and then floated the DC ground on subsequent psu/psu's.?
Kind regards
Ben
Mar 05, 2018, 03:16 PM
Nose down, you're gonna stall
rowdyjoe's Avatar
Quote:
Originally Posted by Irishben
Thanks for quick reply RowdyJoe.that was quick.
So I'm taking it from that ,you didn't do anything with the first supply's DC ground-you just left that alone, and done the the other mods necessary ( ribbon cable 1,2,3,4,5, to ground etc) and then floated the DC ground on subsequent psu/psu's.?
Kind regards
Ben
I'm running two Dell N750P-SO mainframe supplies (12v @ 62amp) in series. I don't think we have the same power supply as I didn't have any ribbon cables to deal with.
On ONE ps only, I had to remove the case to get to the ground stud on the main board. I removed it and insulated the contact pads with electrical tape and reassembled.
The rest of it is straight forward wiring like batteries in series. DO NOT remove the ground stud on the power cord(s) or the interior of the supply where the cords connect.

Good luck and be careful
Last edited by rowdyjoe; Mar 05, 2018 at 03:25 PM.
Mar 05, 2018, 03:22 PM
Registered User
Ok.
The supplies I am getting are hp DPS 600 PB.what ones did you modify,?
Kind regards
Ben
Mar 05, 2018, 03:28 PM
Registered User
Ok.
The supplies I am getting are hp DPS 600 PB.what ones did you modify,?
Kind regards
Ben
Mar 05, 2018, 03:29 PM
Nose down, you're gonna stall
rowdyjoe's Avatar
Quote:
Originally Posted by Irishben
Ok.
The supplies I am getting are hp DPS 600 PB.what ones did you modify,?
Kind regards
Ben
I edited my last post. Take a look

Whichever PS you're converting, you need to isolate the main board from ground. That usually means disassembling the PS to get to the board so you can remove the ground wire or stud. Before you remove or cut anything, make sure it's the ground.
Mar 05, 2018, 03:34 PM
Nose down, you're gonna stall
rowdyjoe's Avatar
BTW ...if you're having trouble identifying the ground, you probably shouldn't be doint this. If that's the case, take the PS to someone who can ID it for you. Disconnecting it is simple once you know where it is.
Remember, you're trying to disconnect the main board from the case.
Mar 05, 2018, 05:03 PM
Registered User
TheBum's Avatar
Quote:
Originally Posted by rowdyjoe
BTW ...if you're having trouble identifying the ground, you probably shouldn't be doint this. If that's the case, take the PS to someone who can ID it for you. Disconnecting it is simple once you know where it is.
Remember, you're trying to disconnect the main board from the case.
Specifically, you're trying to sever the electrical connection between the DC ground (V-, or black, output) and the case. Use a continuity checker to make sure. That can be anything from a digital multimeter in continuity or resistance measuring mode, to a battery, light bulb, and wire.
Mar 05, 2018, 07:27 PM
Use the 4S Luke
feathermerchant's Avatar
TheBum is correct. You DO NOT want to isolate the whole board from ground. Just the output end of the board. In the case of the DPS600, that is the two screws nearest the output.
I do not cut any ground wires or remove any wires from ground studs.
Remember there are lethal (deadly) voltages in these power supplies. If you are not sure what you are doing then get help. By 'get help' I mean enlist someone who does know what they are doing or buy a power supply from someone who knows what they are doing.

And NEVER charge unattended.
Mar 06, 2018, 12:59 AM
Registered User
Thanks everyone for replying!
I do know how to isolate the DC ground,and I do have a digital multimeter to check for (lack of) continuity.
I was really asking about the two methods I have seen for doing it. I was thinking about the other method(rchelifun) & would it be correct to say that
As that method isolates the DC-ground on the first psu, but then attached a grounding tab back to the DC- output terminal (to the case shell) he is basically reattaching the DC- ground which he removed in the first place?
Hence why the method here on Rcgroups, doesn't isolate the DC ground on the first psu, only isolating on the second (and subsequent psu)
If this is incorrect please let me Know...
Kind regards- and thanks to everyone who has taken the time to reply.
Ben
Mar 06, 2018, 01:47 AM
Nose down, you're gonna stall
rowdyjoe's Avatar
Ben,
Sorry about my misleading answers. Hope I didn't cause you any undo stress.
Mar 06, 2018, 02:07 AM
Registered User
Quote:
Originally Posted by rowdyjoe
Ben,
Sorry about my misleading answers. Hope I didn't cause you any undo stress.
Hi Joe.
Not at all joe.i don't really do stress
I just am grateful for the replies.ive read so much information as to how to do the conversion, I'm fairly certain of what I am doing.it was more that I've seen two different methods ( I'm sure there's more than that) and I am trying to understand why they are different.
I think I understand why both methods are different, and at the same time, why both methods are the same.... IF that makes sense
Kind regards
Ben


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