New(er) batteries - anyone tried?

[rogerconnelly]

Hi all - I've been a happy AirMini user for about a year now - that is, I use that machine when I travel rather than lug my larger Dreamstation with me. However, I'm in the market for a battery for the AirMini and I'm just bothered by the fact that the Medistrom Pilot-24 is the one and only battery that is recommended because they hold their price at what looks to be a higher than industry standard these days.

So, I'm seeing a couple of new options that are at least somewhat lower priced offered on Amazon these days - but am wondering if anyone has tried either of these out with an AirMini (or similar) device yet?

Zopec medical battery:
https://www.amazon.com/Zopec-Battery-Ad ... way&sr=8-5

Chargetech battery:
https://www.amazon.com/Portable-Outlet- ... pons&psc=1

Or any other options to the Medistrom that anyone has tried out successfully?

- thanks up front - Roger

P.S. I see there is a current battery thread on the first page of this forum - but it seems pretty focused on lead batteries for camping (the right tool for that job) - but I haven’t seen (nor does a search turn up) any talk of the above two batteries or their type.

[zonker]

bump

[CapnLoki]

Hi all - I've been a happy AirMini user for about a year now - that is, I use that machine when I travel rather than lug my larger Dreamstation with me. However, I'm in the market for a battery for the AirMini and I'm just bothered by the fact that the Medistrom Pilot-24 is the one and only battery that is recommended because they hold their price at what looks to be a higher than industry standard these days.

So, I'm seeing a couple of new options that are at least somewhat lower priced offered on Amazon these days - but am wondering if anyone has tried either of these out with an AirMini (or similar) device yet?

Zopec medical battery:
https://www.amazon.com/Zopec-Battery-Ad ... way&sr=8-5

Chargetech battery:
https://www.amazon.com/Portable-Outlet- ... pons&psc=1

Or any other options to the Medistrom that anyone has tried out successfully?

- thanks up front - Roger

P.S. I see there is a current battery thread on the first page of this forum - but it seems pretty focused on lead batteries for camping (the right tool for that job) - but I haven’t seen (nor does a search turn up) any talk of the above two batteries or their type.

Its a little hard to endorse any battery pack that requires you to run though an inverter. These tend to be only 60% efficient so you really have to almost double the price and weight to get the same power. And they require the use of the power supply that adds more weight. The Medistrom allows you to run directly from 12 or 24 volts (depending on which you buy) and use a tailored power cord. Its pricey, but that's the cost of custom setups rather than mass market.

I'm a bit skeptical of the claim in the comments of the Zopec of 16 hours for an Airsense, given that the available specs imply somewhat less and that's if the inverter is 100% efficient!

There's a reason why most of my posts focus on lead-acid: I try to write about things I know and know to work well. For all the hype about lithium packs they are still rather pricey and generally not configured for cpaps.

[rogerconnelly]

Thanks CapnLoki - I appreciate the response!

[Lane101]

Hi Roger,

To add to CapnLoki's response:

It's a bit of a wild west for products like this on Amazon so careful assessment of customer reviews is required.

Before I get to the batteries you need to validate the AirMini's power consumption. Per the 2018 ResMed Battery Guide the AirMini would consume 0.5 amps at 12 volts at 12 CM of pressure using a ResMed DC to DC converter - they do not show lower efficiency inverter numbers for the AirMini. You will also need to adjust the above for your actual therapy pressure. Using 12 CM as an example this implies 48 watts of power for 8 hours. The 95 watts hours in the Medistrom Pilot-24 would provide one and a half nights sleep with 80% of the Medistrom battery capacity per the above calculation.

Regarding the alternative batteries an initial scan of the reviews raises questions about their applicability for CPAP use:

The Zopec only has two reviews (one who has yet to use it) so almost it's almost impossible to understand its actual quality level. No way they can fairly claim a universal 2 -3 nights of use given the wide range of CPAP current requirements across machines and pressure settings.

The Chargetech has a number of one and two star reviews from CPAP users who were disappointed with the run time. Per a very thorough August 19,2016 three star review, provided by one Chargetech customer (who did a complete teardown and various tests), the 27K mah comes from 4.2 volt cells and the inverter is a basic modified sine wave with only 56% efficiency (CapnLoki was right). Not all CPAPs run on modified sine wave. You would need to confirm that this is safe for your machine.

An assessment of battery capacity raises additional concerns:

Since neither of these manufacturers specify the voltage at which they provide the claimed 27K or 54K mah (likely at individual lithium cell level of 3 - 4 volts) you need to look at watt hours to understand actual capacity converting to 12 volt amp hours and adjusting for efficiency. For example the Zopec states a capacity of 160 watt hours - about the same as a 13 amp hour 12 volt battery that might support roughly one and a half nights of AirMini use at 12 CM assuming 60% inverter efficiency and use of 80% of capacity. This is similar to the Medistrom. The issue here is there are no valid reviews to confirm that this battery works and provides the stated capacity. Also at 160 watts you may not be able to bring it with you on all flights per FAA rules.

The Chargetech, per the manufacturer on a 10/24/17 in a Q&A, has 92 watt hours, roughly the same as an 7-8 amp hour 12 volt battery. At 56% efficiency it will only provide a fraction of the Medistrom's power and it's unlikely you will get a full night - further validated by the one and two star CPAP user reviews where only a few hours of use was noted.

Looked at Lithium when I recently upgraded my camping powerpacks with new replacement 20ah agm lead-acid batteries ($40 each) and the cost/performance just wasn't there yet. Lithium should be considered a premium option where weight is the primary concern or where lead-acid is not an option such as on airlines. Note that a couple agms can be wired in series to generate 24 volts.

Bottom line is that if you need Lithium due to weight or airline restrictions it's necessary study the reviews in detail to validate quality and do the math on the capacity figures to determine if the capacity will support your CPAP. Also, you need a 12 (with converter) or 24 volt battery to avoid inverter efficiency loss. CapnLoki is right to be skeptical that these two batteries will meet your needs.