battery backup recommendations as10/as11

[robbob2112]

Well, poking around - the cheap generic 12vdc converters work fine and I ordered it.... but the genuine resmed version also converts from 12v or 24v to 24v, so it would have taken care of the voltage regulation and all that mess.... just at a $60 cost difference... or there maybe 24v converter that also do the same thing, I just havent seen them. Wouldn't have fixed my need for the concentrators to be 12v but for anyone just wanting to run the cpap 24v would be a simpler way to go.

[robbob2112]

Well, no shock here, plans change in the face of reality.  I'll be charging the battery downstairs and in the event of an outage bringing it upstairs to use.  And I'll use it periodically to drain the battery and see how long it lasts.  The inverter charger claims to be quiet, but when running it is at least a 60db fan.

So, going to put the battery in a box with just the cables for the pap and concentrator and (maybe a small inverter for the tv) will do all the charging downstairs.

For the disconnect I just bought some anderson powerpole sb350 connectors for the cables and when I get a box I'll use a panel mount adapter to pass it through the side. 

Note: sb350s cost around $35, there are MANY knock offs on amazon for 1/3rd the cost, don't be tempted

[robbob2112]

Well, I cancelled the cheap DC-DC converter from amazon for $30 and bought the real deal (resmed brand) from vendor #1 for $60 .... 30% off sales through today... This lets me convert to 24v later easy enough.


On the battery itself I plan a blue sea brand terminal mount fuse at 200amps for protection from shorts, a current shunt and display to show stat of charge, and pigtails for the SB350 to charge, and fused pigtails to the 12v sockets (10guage wire + 30amp fuses) for the cpap and concentrator.

On the inverter/charger I will have the type T fuse to a SB350 - so I can connect it and charge the battery or use the inverter for larger devices like furnace, tankless water heater, or fridge.  

Note on the furnace - I have a flame detector that uses earth ground and am not quite sure how to hook that up properly yet.  Also a full battery would only run the furnace for about 4 hours.  So there are details to work out.

With the SB350 I no longer need the disconnect switch since I can just unplug the cable.

Overall I learned a valuable lesson pretty cheap that I have read about over and over on the diy solar forum, but it appears to have not sunk in.

---plan -- plan---plan--sleep --plan--plan -- buy --figure out what you did wrong -- get the right stuff and install/connect

At least I didn't spend $25k on solar equipment to find out I got the wrong stuff.

[robbob2112]

Well, it is all assembled - mostly - I have the wrong size fuse there so when I went over 40% load I popped it... the holder came with a 100amp version and it should have been 225amps for the load and size wires.  The right size is on order.  

I also didn't have the right loops to hookup the current shunt panel properly and just used alligator wires until those arrive.  The battery terminals are 5/16" loops as are the terminals on the back of the inverter.  The fuse holder and disconnect switch both took the 3/8" version.  The shunt was 5/16".

The proper red/black heat shrink for the exposed loops at the back of the inverter is also on order.  

And I happened to have some clear 2" heat shrink that would cover the current shunt.  Doing it over I would have researched that better and spent a little more than $20, it is obviously a cheap piece of work and very crudely executed.  Rough bolts threads that were probably salvaged from the reject bin, half formed.  It also reads off by .2 volts verified by my fluke and the inverter screen.

The cables are all as big around as my thumb because of the voltage.  In hindsight I would get either the 24v or 48v and make the cables 1/2 or 1/4 size they are.  Being fine stranded pure copper welding cables they are very easy to bend, so there is that... (note - NEVER use CCA - copper clad aluminum)  

At 24v I could run the resmed dc-dc converter straight and a buck converter for the concentrator.  

Each big piece is about 40lbs and the wiring is another 5lbs.

If you are planning to just use it for camping either get a pre-built version or get a 24v 300Wh or 600Wh battery  I think the 300wh would probably run the pap about 2 days (8hrs) with the heater and tube at a guess...  If you are like me and planning it just for around the house I would get the 48v 5.1kw version and have way more power than you need.  The cost is a lot higher, but assembly would be quicker.

I plan to refine it quite a bit and when the quiet inverter and charger arrive I'll put it all in a box for the bedroom.

[robbob2112]

I highly recommend fuses.  Specifically terminal post fuses.  I will be switching to that verse the type I am currently using.  The reason is the battery short amperage on this is around 7000 amps.  And if you don't have a fuse and make the slightest mistake or screwdriver slip it can weld across the posts and cause bad things to happen.

https://www.amazon.com/gp/product/B0019ZBTV4
https://www.amazon.com/gp/product/B0026KY6R0

Also, all fuses on amazon are not created equal.  From reading and research a lot of the cheap knockoff fuses are the exact same physically with different amperage printed on them.  The only way to be sure what you are getting is to buy from a known company like Blue Sea systems that produces hardware for boats and marine equipment or red wolf that produces stuff for the car audio market.  So if the seller is a mismash of unpronounceable letters either buy extra and test one to see if it is real or spend the extra $$ and get things from a reputable company that supplies marine equipment.

There is a lot more about the ability to quench a plasma arc when you deal with larger batteries and solar equipment the fuses are filled with sand and other things that break the arc verse just air.  This is a whole different topic with many write ups and videos to explore.

Robert

[robbob2112]

OK, the offical resmed DC-DC converter has arrived. Using the victron smartshunt with nothing else connected, the converter draws 2watts of power. That is just sitting there plugged in. So, 48watt hours per day doing nothing but smoothng the voltage to 12v.

Now when running on battery I would make sure to turn off of disconnect the power brick.

[robbob2112]

   

Pic from the top of the unit.  

The asv draws 6 watts while idle 56watts just heating the tank and tank plus hose was 108watts.  It was bouncing around a lot.

I'll see how much the whole night tonight consumes.

Note: I need to remake one of the wires to the anderson power connector to get the same length.  The connector is for hooking up the inverter.

On top is a disconnect switch and victron smart shjnt on the negative side  and a 250a post fuse on the other side

[robbob2112]

Resmed aircurve 10 ASV with tube temp at 74 and humidity at 7.

The crazy high readings from my last post were from running it open ended without the mask or me attached, so fan was full out.

5:22pm -  4watts just for being idle with screen off - screen takes 1 more watt when on - 1.4ah used until bedtime
10:08pm - turned on, consuming 59watts - tube on, tank heater on - they will cycle on and off once they hit temp.
8:48am - woke up - total of 32Ah used

the math
32ah - 1.4ah = 30.69ah used

Now since the battery is rated in watt hours as are most of the all-in-one units we multiply by 12v * 30.6 and get 367.2Wh.  

A bit more than the smallest of the jackery or other unit.  So, if buying a jackery or other you need the 1000wh unit for almost 3 days use.

My battery has 2056wh in it so around 5 days of the Apnea machine alone.  

Can't wait to see what the O2 concentrator runs with the apnea machine tonight.

For reference my tundra has a battery with about 800wh in it and weighs 68lbs and the LiTime 200ah plus weighs at 45lbs with 2056Wh.  

And if you go from regular battery to deep cycle lead acid the weight increases by about 25% with marginal increase in Wh.  And for this you would want deep cycle.

[robbob2112]

Ran just the conectrator for an hour and did the math, 457wh for 10.6 hours used last night. Combined total of 77.74wh used each hour of sleep.

2056 ÷ 77.74 = 26.45 ×0.80 (never run below 20% charge) = 2 days sleeping for me with both. I may have to add a battery in parallel to double that or just recharge every day so I have a night available.

[robbob2112]

Last post from me unless someone asks a question

Ran both the concentrator and the asv last night from battery and came up with 947wh for 8.6 hours means 109.1wh per hour... a bit higher than I figured. 

I'll keep track for a while just to find the average for my own use.  

The main thing is it works for me.