Resmed S9 DC-DC Converter Photos

[billbolton]

What's in the box Bill?





How do I know they aren't clever cardboard replicas, staged in a studio in Houston Bill?



OK, so they are real, but how does the size compare to the AC power adapter Bill?



As far as I can tell without using a set of scales, the weight for DC and AC devices feels pretty much the same.

I used the DC converter last night and ran my S9 Autoset on my "normal" settings.... APAP mode 14-16cm range, EPR 3, H5i + Climateline set to 19 degrees Celcius.... using a fully charged "Absorded Power AGM GT12-90C 90 AH battery. It ran just as if it was on mains power, and as far as I can tell from measuring battery terninal voltages, it drew down about one third of the total battery capacity on those settings.

Cheers,

Bill

[BernieRay]

Thank you so much, Bill, both for the photos and the usage info!

Based on your settings, it looks like a sprial cell AGM 90AH is in my future. Although I've gone passive on the H5i for the last week or so, I could switch back, so I need to plan for that possibility. With 10-13 and EPR3, it sounds like I could probably get 2 nights usage without overdischarging the battery depending on my CC setting, a lot more if I go passive on the H5i. Even if I do switch back to CC, I'm sure that I could make do in passive mode during a power outage, or keep the temp in the 60-65F range.

[sk8rs_dad]

Are there any specs on the input voltage tolerances. In specific, is a 14.8 V L-ion battery going to work (15.3V no-load), or am I going to get out-of-range errors like I do with most inverters on the market?

[Uncle_Bob]

Great post Bill

I don't think i ever seen such a cheerful post from you

-UB

[chunkyfrog]

So when will this puppy be available to us Yanks?

[BernieRay]

Last Friday, officially. I ordered one on Thursday. My DME called on Monday to tell me that it had arrived. I'll be picking it up on Friday, though I haven't had the time to get everything else.

[billbolton]

Are there any specs on the input voltage tolerances. In specific, is a 14.8 V L-ion battery going to work (15.3V no-load), or am I going to get out-of-range errors like I do with most inverters on the market?

I'm ine the office right now so don't have the instruction handy, however, Its spec'ed for working with either 12V or 24V DC electrical systems.

I know that the Resmed DC-12, the equivalent unit for the S8 range which also had the 12/24V DC input spec, would work fine from a ~16V DC input as that is what I used when doing various tests before building my NiMH battery packs a few years back, so I'd expect that the S9 unit is the same in that respect.

I haven't had a chance to try the S9 converter off a non-Lead-Acid technology battery DC source as yet, but will try it when I get some time to test that (coul dbe up to several weeks away).

There is a lower limit cut-off voltage spec''ed for both 12V DC and 24V DC inputs (to avoid running a battery down too deeply), so presumably its not a continuous spread between ~12V and ~24V DC for input.

Cheers,

Bill

[BernieRay]

I picked up my converter yesterday., so now I need to get everything else. Since the manual states to not use the S9 with the converter when the battery is being charged by AC, and I don't expect to need it much, I think I'm going to keep things simple - converter, battery, and float charger, maybe a battery box.

I'm probably going to get

Optima blue top D31M (75 AH) - http://www.optimabatteries.com/optima_p ... /specs.php
PulseTech 12-V Xtreme Charge™ Battery Charger - http://helios.pulsetech.net/cgi/hsrun.e ... NO=100x010

Any thoughts?

[billbolton]

PulseTech 12-V Xtreme Charge™ Battery Charger

I'm using a CTEK MXS 4003 and have been very pleased with the results.

http://www.ctek.com/EN-AU/consumer/mxs-4003.aspx

This model has just been replaced in CTEK's 2011 product line with the MXS 5.0 ......

http://www.ctek.com/EN-AU/corporate/news.aspx?id=53

.... (which is pretty much the same but has bit more capacity), so there are some good deals going on MXS 4003s, if you look around for them

Cheers,

Bill

[LoQ]

I picked up my converter yesterday., so now I need to get everything else. Since the manual states to not use the S9 with the converter when the battery is being charged by AC, and I don't expect to need it much, I think I'm going to keep things simple - converter, battery, and float charger, maybe a battery box.

I'm probably going to get

Optima blue top D31M (75 AH) - http://www.optimabatteries.com/optima_p ... /specs.php
PulseTech 12-V Xtreme Charge™ Battery Charger - http://helios.pulsetech.net/cgi/hsrun.e ... NO=100x010

Any thoughts?

Just curious why you selected the blue top instead of the yellow top?

The YellowTop can repeatedly bounce back from deep power drains to full energy capacity, so it can power plenty of electronics and still start you up time after time. Lower internal resistance also provides more consistent power output and faster recharges.

[BernieRay]

Just curious why you selected the blue top instead of the yellow top?

The YellowTop can repeatedly bounce back from deep power drains to full energy capacity, so it can power plenty of electronics and still start you up time after time. Lower internal resistance also provides more consistent power output and faster recharges.

I had 2 main reasons, LoQ. The Blue Top has 5/16" threaded studs and the D31M has 9AH more capacity than the largest Yellow Top (D27F). Plus, the D31M supposedly has 3X more cycles compared to the D27F's 2X more, if those claims are true. They're both deep cycle, so that's a wash between the two.

The 5/16" will be handy since the PulseTech comes with a fused ring lug harness. I will probably end up making a modified battery box, similar to what JohnBFisher made, so using these lugs will just make things simpler. Since the D31M weighs 58 lbs, I will probably keep the battery on a small hand cart. I don't really want to lug it around in the middle of the night when I'm not 100% awake - I like my toes!

I also plan to replace the Resmed converter's female lighter to battery clamp cable with one similar to this, assuming that I can either find or build one that can handle at least 6A. If so, then I can use the single harness for both the charger and the converter. That would help keep things clean, and I won't have to use any clamps on the SAE posts.

[idamtnboy]

Bill, have you had a chance to try the converter more than just the one night? I'm curious about one thing. In your pictures the mfr label on the converter shows that the DC input is 12/24 volt, 13/6.5 amp. The Resmed battery guide shows 7.25 amps at 12 volts for the greatest current draw for the S9 + H5i. I'm sure the converter is designed and rated for the greatest current draw of the S9 + H5i, plus some safety factor, but 13 is almost double the 7.25 listed max draw. Makes me wonder just what the efficiency of the converter really is. Have you made any tests at all comparing the current draw from the battery by the converter for various S9 + H5i settings and compared the results with the battery guide table? Makes me wonder how much more efficient the DC converter is than a DC/AC inverter + the standard power supply. Greater efficiency is what most every one here was wanting from a DC converter. Did we get it or not? Any idea?

Has anyone made any tests to find out just how good the Resmed DC converter is? I'm hesitant to buy one if the efficiency isn't all that much better than an inverter plus AC power supply.

[billbolton]

Bill, have you had a chance to try the converter more than just the one night?

It runs fine for two succesives nights from my particular battery, with my normal S9 + H5i settings.... since that was my personal design goal for domestic power outage coverage, I haven't investigated endurance from the battery beyond that.

I've written about efficency issues previously here, on a number of occasions. If you already have a switch mode inverter, don't need 24V DC source capability, and don't mind carrying two power devices, and efficency is your only issue then there's only a relatively small efficency gain (IMO about 5%, tops) likely to arise from using the DC/DC converter versus an Inverter + AC adapter combination.

I suppose Resmed will eventually get around to updating their battery guide paper to cover the new converter, and perhaps more on the comparitive efficency front may be evident when they do that.

Cheers,

Bill

[JohnBFisher]

Bill, as you note, thanks to the use of electronics and the need to supply DC current to those devices, inverter technology has improved remarkably over the years. I have personally seen the size of the power supplies shrink over the years and become much, much more durable. I also would be surprised if the loss of power between inverter and this converter was over 5%.

And for the average user, I was extremely happy to see that Resmed changed their power supply to allow use of a modified sine wave (rather than requiring a pure sine wave). This was a HUGE step forward.

[nmevan]

thanks for all the hard work and info

I'm new to all of this and I'm wondering if this device would work with my respironics auto bipap biflex system one?
the sticker on the back of the machine says 12V 5A
do most machines have a similar power connection?

I'm hoping to go camping in july to a place where there is no electricity
any suggestions on the best way to recharge a battery?
the area is somewhat shaded, so I'm worried about solar and I don't want to make a bunch of noise with a loud generator

thanks again

evan