56 V DC to 48 V DC Converter

This oxygen machine draws how much current?

This 56 volt battery, does it contain enough of those pesky ampere thingies to operate both machines for 100% (might be well to consider 120%, maybe more) of anticipated duration of an outing?

This is a battery pack in a golf cart. The machine uses 360 watts. The batteries are 70AH.I will carry a separate oxygen bottled supply in case of failure.

The problem I am having is finding a 56 VDC to 120 Volt converter of at least 1000 watts. .

There are small one for tools, etc. but not enough power.

Plenty of other voltages but not 56...why?

SE is good at finding the hard to find stuff, maybe he can come up with something...

SE Are you there?

There is a disjoint here.

In your OP you tell us convert the 56VDC battery to 48VDC. In post #2, the target is now 120 volt, presumed to be AC.

Do you wish to have on board the cart a 120VAC outlet, powered by the batteries, and you can plug-and-play your oxygen machine? If this is the goal, you might be able to find a COTS inverter that would accomplish this.

If you are already planning a belt and suspenders scheme (oxygen generator, and a backup bottle system), why not simply a different belt? A spare bottle (or two), from your description so far, would be far less expensive, requires no conversion, or gear added, to the cart.

We don’t know the intended user profile of the cart. A round of golf is, what, about 3 hours, so about 1,000 Wh total for the oxygen generator. Add in losses from conversions and efficiencies, you might be stressing your battery array pretty hard.

Well, I guess having 120VAC on a golf cart is a thing. A search of the unimpeachable internet information cesspool that is YooToob reveals many intrepid individuals showing us how that can be dubiously accomplished.

A search link for this yak fountain here:

https://m.youtube.com/results?sp=mAEA&search_query=56+volt+golf+cart+120+inverter

No report on the number of carts lost to autoignition can be found. Be careful, my friend.

There is more than just a disjoint here. There is a liability issue. Modifying medical equipment, in this case, an oxygen concentrator power source, without proper oversight, can expose the user, designer, and fabricator to multiple liability issues.

IMHO, HTRN should consider acquiring a COTS portable oxygen generator, such as this or this company's product. Tapping into a golf cart's battery for life-sustaining use makes me wonder about the cart's battery charge level.

re: Modifying a medical device. I hadn’t considered this. There is much truth in what you say!

re: battery reserve. As I read again post #2, HTRN tells us “The batteries are 70AH.” Batteries . Plural. 70 Ah each, or in total? How many in the battery array? Is there a battery management system in place? I am inclined to think yes; if so, will the BMS read this extra draw as a fault and shut down?

AFAIK there is no portable DC oxygen generator available that will supply enough oxygen for my needs. I require 3 l/m constantly .

They are all an on-demand type supplies, not a steady stream.

If anyone can find be an oxygen generator that is dc powered that can provide continuous oxygen, at 3l/m rate, that would great.

Thanks in advance!!

The golf cart I am using has a range of 8 miles, and I will use it only around the farm, so it will be sufficient for my purposes.

Here is a portable, battery-powered generator capable of delivering continuous flow. The flow can be adjusted from 1 to 5 L. The two-battery unit delivers 2 hours of use at 5L. I expect a reduced flow will provide more operational time, but not necessarily a linear extension.

I doubt you will find a DC powered concentrator that will fit your needs. There are a few out there that claim continuous flow for significant time, but in reality the batteries don't last long if they are used at full capacity. They may have improved. I haven't use one since 2019, but in my experience they never lived up to the marketing hype.

Prior to receiving a lung transplant in 2019, I was using 4-6 liters continuously. There were no portable concentrators capable of that and tanks didn't last very long. I was able to get by having a concentrator at home and one in my office. Tanks were used for the 15 minute commute. I am very happy to say that my lung function is almost fully normal after transplant.

I wish you good luck in your quest. I know what it is like to spend years tethered to an oxygen tank or concentrator.

I found this inverter below that seems like it would fit the bill and allow a full sized concentrator to be mounted on your golf cart.

The equipment will NOT BE MODIFIED. It will be used as is, which is why I need to provide 120VAC,which is the voltage it normally uses.

It is not "Life sustaining". It is a convenience to me. If the machine fails, I have backup tanks on the cart, with regulators set, ready to go if needed.

It would allow time for a cellphone call if i need it.

The golf cart has a very intelligent monitoring system that gives a continuous display of remaining power in the battery pack, and a limp-home mode if needed.

I don't travel very far from home base: max probably 300 yards, so it is fine for what I need.

I just need to get out of the house and tend my little victory garden and listen to nature in the forest nearby.

Would you tell us about the proposed golf cart?

The reason for this question is, the 56 volt seems to be pretty unusual, uncommon. One example that I had a look at is the E-Z-Go Liberty.

The spartan spec sheet I could find at the manufacturers website tells me that the battery is a 56.7 volt unit, but the cart itself is 48 volt. So, the cart electronics management system apparently has an internal down buck converter built in!

https://ezgo.txtsv.com/personal/models/liberty/specs/7084

If my understanding of this is correct, and if your selected cart is a similar engineering, you now have a simple solution.

A 1000 watt 48 VDC to 120 VAC inverter is a pretty common device; a popular e-commerce entity shows dozens of available models.

You are right. I misstated what I wanted. I need to convert 56 VDC to 120VAC.

You may think of using 2x24 volts (isolated output) with output series, or if you can find 8 volts isolated one, you may use it in buck mode with 56 input volts too,

EGO makes several models of 56V (EGO battery voltage) to 110VAC inverters. Do a search for "EGO inverter" and you will see the models available. It should be pretty easy to connect one of these to your cart battery.

The EGO inverters use the EGO 56 volt tool batteries. Might be able to monkey with one, and get it hooked up.

Similarly, I would be surprised if a a 48VDC to 120 VAC inverter was not able to handle 56V.

https://theinverterstore.com/product/1500-watt-pure-sine-inverter-48-vdc-to-120-vac/

Specifications:

• Continuous output power 1500 Watt
• Surge power 3000 Watt
• Input voltage range 38-62 volt
• Output voltage 120 volt
• DC input 48 volt
• Output wave form pure sine wave 60Hz (THD ≤3%)
• Efficiency 90%
• USB Output 5VDC, Max, 1 amp
• Input over-voltage shutdown 62 ± 1VDC
• Input under-voltage shutdown 38 ± 1VDC
• Input under-voltage alarm 39.2 ± 1VDC
• Over temperature protection 149 ± 8°F
• Over-load protection 1700 Watt ± 200 Watt
• No Load currents 0.5 amp
• Working Temperature 32-104°F
• Storage temperature 14-113°F
• Intelligent cooling (the cooling fan will start running when the case temperature reaches 104°F)
• Remote port for optional remote

Dimensions:

• Unit weight: 9.90 lbs.
• Unit size L x W x H: 15.88 x 8.38 x 3.88 inches
• Shipping weight: 12 lbs.
• Shipping size L x W x H: 18 x 12 x 6 inches

Product manual: click here

You need DC-DC buck converter with a wide input range (like 36-72V to 48V) that’ll work fine with 56V.

See comment #8.

A solar charge controller is designed to take higher cell voltages and charge several different selectable chemistry batteries.

A 30A rated PWM controller is under $100, but you need it for a 48V battery.

Here is one that should work. Your lithium battery connects to the PV input, your O2 machine to the battery connection. Set it up so your battery is lithium, so no float or other adaptations for chemistry.

https://bluemarine.com/products/victron-bluesolar-pwm-charge-controller-duo-lcd-usb?variant=49275978645800&country=US&currency=USD&utm_medium=product_sync&utm_source=google&utm_content=sag_organic&utm_campaign=sag_organic&gad_source=1&gad_campaignid=20511573037&gbraid=0AAAAAqKlSrhgcSuJw0n3xjG1AoPncpRJh&gclid=Cj0KCQjwkYLPBhC3ARIsAIyHi3SRwfYyQXXni0QdG-8dS-LO4gvFtGZzWpe4XCSqcfMxYQ7soYestEwaAjySEALw_wcB

I've built a battery pack or two and I'm wondering why you don't tap the battery bank at 48V? I can tap my 48V battery bank at 12V for onboard equipment and at 48V for my motor. You could connect to the negative terminal of the cart and run a fused connection to the point in the batter bank where you have 48V. This is assuming you are running with a bank of 6 or 12V deep cycle cart batteries.

I have done this also, but it creates an imbalance in the battery voltages and problems when charging. I will do it every now and then for a saw or drill, but the demands of the O2 generator are much much more and will create a severe imbalance.

Another option is to buy a couple of Atlas batteries and an inverter pack at harbor freak tools. That would be portable and useful for other needs as well.

If you want to roll your own, you could use a voltage regulator to drop 56 volts to 48 volts. Most regulator ICs are good only to 37 volts with a ground reference, but you can raise the reference voltage to a higher voltage using a zener diode as described in the reference.

https://www.idc-online.com/technical_references/pdfs/electronic_engineering/Floating_Regulator.pdf

See floating voltage regulator.

LM723 Datasheet

Definitely find a load resistor for the required voltage and current for testing before connecting to your oxygen machine.

A solar charge controller is designed to take higher cell voltages and charge several different selectable chemistry batteries.

A 30A rated PWM controller is under $100, but you need it for a 48V battery.

Here is one that should work. Your lithium battery connects to the PV input, your O2 machine to the battery connection. Set it up so your battery is lithium, so no float or other adaptations for chemistry.

https://bluemarine.com/products/victron-bluesolar-pwm-charge-controller-duo-lcd-usb?variant=49275978645800&country=US&currency=USD&utm_medium=product_sync&utm_source=google&utm_content=sag_organic&utm_campaign=sag_organic&gad_source=1&gad_campaignid=20511573037&gbraid=0AAAAAqKlSrhgcSuJw0n3xjG1AoPncpRJh&gclid=Cj0KCQjwkYLPBhC3ARIsAIyHi3SRwfYyQXXni0QdG-8dS-LO4gvFtGZzWpe4XCSqcfMxYQ7soYestEwaAjySEALw_wcB