Advice wanted Lithium/gel/ for cpap machine??

[MaidinDevon]

copied and pasted from email to Off Grid Solutions. Their quote is £750 for 100life POA and victron dc2dc, plus fitting.

I need some advice before choosing which set up to use.
Currently I have one Gel battery, and 120w solar, with a controller.
This is not able to run a cpap machine overnight without flattening the battery, to und3r 12v, when the panel switches it off.
I recently sent the control panel and EBL away to be tested, because it seemed to be malfunctioning and Applejack have confirmed they are working as they should.
I mostly use the van off grid, rallies and pub car parks etc.
The van is a Hymer B654, 2005 registration.
So, my options, as i understand it are
Replace I gel battery and see if a new one can manage.
Replace 2 gel batteries.
Change t9 lead acid or AGm and change the EBL profile.
Or lithium.
I don't use a lot of power, laptop, 3 way fridge and hot water, etc, but wo7kd be nice to have extra, if not too expensive.
The van just passed her MOT, so certainly planning to keep her another 12 months at least.
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I pressed rhe wrong button, an sent rather than attachment.
I hope you have some advice, and likely costs I am based near Worcester, but can travel for work to be done.
Thank you
Karen
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Hi Karen
Thanks for reaching out about your battery.
Do you happy to know how much power your cpap machine draws?
In terms of pricing for lithium, here is an estimate for installing lithium with a DC to DC charger: https://squareup.com/pay-invoice/estimate/inve:0-ChCphnH1m06xHVSXzbqXqhKdEP0P
This 100Ah lithium battery would give you the equivalent power to two Gel or Lead Acid batteries. We offer a 10 year warranty for our batteries. The battery has a BMS built into it, which will offer protection so if you did happen to drain the battery completely, it would stop it from being damaged.
Also, having a DC to DC charger will help in that it will speed up the charging of the battery as you drive.
We’re based in Wantage, Oxfordshire and.
Hope this helps! Please get in touch if you have any questions.
Thanks,
Nigel Ivy
offgrid power solutions
visit our website
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[stevewagner]

How are you powering your CPAP at the moment? I use a CPAP with a 12 volt dc adapter Which I have been using for any years without any problems.
The quote for the upgrade seams reasonable.

 

[MaidinDevon]

Not sure that I have explained myself very clearly.
I need to be able to run a cpap machine a Philips Dreamstation 2.

My current battery can't cope. But it is probably old. I've had the van, 4 years, and it hasn't been replaced.

Do I need lithium? I'd like it, new tech etc, but I think it is probably twice as expensive as 2 gel batteries. I cant afford to put extra solar on as well, so would i get the benefit.

Confused

Edited to add I have a 12 bolt adapter for the cpap machine, bought on Amazon.

 

[WESTY66]

RogerIvy ??

 

[Jake Royd]

My wife has a Phillips Dreamstation machine which runs on 12VDC. We use a lead directly from the leisure battery via a fuse of course.
The leisure battery is nothing special just a 90ah lead acid. It is pretty new.
We have a 200w solar panel charging both can and leisure batteries.
Never have a problem although we don't use it off grid for many days without driving.
The mains power supply gives its output as 12v and 6.6A but it seems unlikely the machine draws 6.6A all night? That would be a 50%dod.
Can't see any wattage given on the machine.
However, thinking about it for a moment that current will be to also power the heated humidifier, so the current for the machine will be much less.

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[Jake Royd]

Note 6.6A is 80w at 12v

 

[MaidinDevon]

Yes, Roger Ivy is offgridsolutionsand has been helpful.
. I have a heated humidifier too. Wonder if I cam switch it off in the van. Although I cough more without it. So maybe a false economy.

 

[Jo662]

I think this would be a good time to have something like an Ecoflow Delta power bank,
purely for the Phillips Dreamstation machine

 

[Reallyretired]

I think this would be a good time to have something like an Ecoflow Delta power bank,
purely for the Phillips Dreamstation machine

Only downside is that costs more than the lithium solution proposed and doesn't have the B2B.

 

[Jo662]

Only downside is that costs more than the lithium solution proposed and doesn't have the B2B.

Very true,but could be an easy solution and portable.

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[Red Sonja]

Yes, Roger Ivy is offgridsolutionsand has been helpful.
. I have a heated humidifier too. Wonder if I cam switch it off in the van. Although I cough more without it. So maybe a false economy.

It's the humidifier that uses all the power. I have a resmed 10 and remove the humidifier. We havec1 80 watt solar panel but 2 batteries. Only ever run put of power on a week long cold winter rally.

 

[RogerIvy]

Hi Karen, I’ve been travelling today so just seen your thread.

I guess the real question for you is whether you drop in two 100AH lead acids (or AGM/Gel) or go for a Lithium upgrade. As Nigel said in the estimate a 100AH lithium is pretty much the equivalent storage of two 100AH lead acids, so in terms of total power storage about the same.

So what would Lithium provide that lead acid can’t? There are a few advantages that may or may not make the upgrade worthwhile.
Lithium charges 10-20% faster than lead acid under the same current. Less “wasted” power. This increased efficiency helps when you have limited solar input.
Lithium accepts a higher charging rate than lead acid. (So they’re more efficient and can be charged faster).
Usually one installs a DC-DC (B2B) with lithium and this often speeds up the charging when driving.
Lithium, through the BMS can tell you fairly accurately how much is left in your battery and what you’re currently drawing (and how long the battery will run before being depleted). You can do the same with lead acids if you install a shunt.
Lithium has built in protection with the BMS. You can install something like a Victron Battery Protect to protect lead acids and they start at about £37
A 100AH lithium is much lighter than 2x100AH lead acid.
Lithiums should last much longer than lead acids, so at some stage become cheaper. Having said this the longevity benefit is better with the bigger capacities.

Not knowing much about CPAP machines and knowing very little about your model I did some research. It would appear that usage varies greatly from one person to another but that in theory a single battery could run it for a few days depending on things like the dehumidifier.

To summarise, you would likely be able to run your machine on a single new LA or Gel battery. A set of two LA or Gel batteries would be better, if you decided to stick to with LA or Gel. A smartshunt would be a good idea have visibility of what the system is doing.
Lithium would charge more efficiently and last longer, so you would not be in the same position of having to change your batteries again in 5-7 years time.

Hope this helps a bit.
Rog

 

[autorouter]

I recently sent the control panel and [Broken Link Removed] away to be tested, because it seemed to be malfunctioning and Applejack have confirmed they are working as they should.

What model number of EBL is it? and what model number of control panel is it? Does the control panel show the percentage of charge remaining in the leisure battery?

 

[ManTheVan]

For what it’s worth, I think the quote for a new LiFePO4 battery, B2B and fitting is very reasonable indeed.

 

[autorouter]

Your Philips Dreamstation 2 uses 80W at full power, when using the humidifier. I think you are one of those users that needs to run it on full power, including the nebuliser. From a 12V battery, 80W uses 6.7A. This is calculated using 'Watts = Volts x Amps', so 12V x 6.7A = 80W.

If that is on for 8 hours, it will use 80 x 8 = 640 watt-hours (Wh) of energy.

However 12V batteries usually have their capacity rated in Amp-Hours (Ah) not Watt-Hours (Wh). Its easy to convert Wh to Ah, just divide Wh by the battery voltage. So 640Wh = 640 / 12 = 53Ah.

That is quite a lot of the battery's capacity. You don't say what the capacity of your battery is but it's probably about 100Ah. For a Gel battery, about 80% of that is usable, so that's 80Ah available.

If the battery isn't new, it may have lost some capacity, and may be say 80% of its original capacity. In that case its real capacity is only 80Ah when 100% full. But only about 80% of this is usable, which is 80Ah x 80 / 100 = 64Ah. So you'd be using 53Ah out of a possible 64Ah just for the CPAP machine.

I think that in reality you would be lucky for it to last for the whole 8 hours when you include all the other loads on the battery, and that is what you say is happening.

I think the minimum upgrade would be two new Gel batteries, maybe 200Ah in total, giving you a usable 180Ah. That would be easily enough to last for one night, and should last for two nights, maybe even three. Standard Lead-Acid (LA) batteries have less usable capacity than Gels - only about 50% of the label capacity is usable. So two new 100Ah LAs will only give you 100Ah of usable capacity, which would be enough for 1 night, but probably not quite enough for 2.

Then you have to think about how to recharge them. A 120W solar panel will give you about 35Ah on an average day, and 45Ah on a good long sunny day. But a lot less in a spell of dull weather. So it's not going to be enough to refill the battery. I would think at least 250W of solar would be needed to do that.

A B2B charger would be another possibility, to boost the charge from the alternator while driving. A 60A B2B would push about 60Ah of charge into the batteries for each hour of driving. So about an hour would be enough to put back what the CPAP takes out in one night. Of course a 30A B2B is a bit cheaper, but would take twice as long.

On the lithium question, I think the suggested 100Ah lithium battery won't be enough, you'll need 200Ah at least. Even though I am a big fan of lithium it may be that you won't gain as much as you think in terms of capacity when you compare two new 100Ah Gels to 200Ah of lithium. Two new 100Ah Gels will have a usable capacity of 180Ah, and 200Ah of lithium will have maybe 190Ah.

However a 200Ah lithium will be happy charging from a 60A B2B, unlike 200Ah of Gels which would prefer a B2B with a maximum rate of 40A or so. So if you want to have fast charging and want a big B2B, a lithium is definitely better.

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[MaidinDevon]

Thank you Autorouter

That is extremely useful and detailed. I followed advice on here, and used the machine without the humidifier, snd the battery did not drop much. Which is great news, although I would prefer the humidifier as well. Definitely need to consider what to do. It is important to use the cpap, for my health, less important for odd weekends, but I also go away fir a week at a time.