Interference from battery charger in DC battery backup setup?

[Daxvex]

Hello all:

I have a battery backup that I've seen often used on the board:

- 12V AGM car battery
- Cigarette lighter connector
- DC 12v to 24v converter
- Resmed AS 11 CPAP
- Battery charger to keep the battery topped up

The charger I'm using is an 8 Amp "smart" charger with all sorts of battery health features (Search "HUSGW" 8 amp charger on Amazon, I'm new so I can't post links). When it's hooked up, the CPAP does not go into standby (i.e. screen stays on), but if I disconnect it, then everything is fine. I suspect the smart charging features are generating interference at the battery terminals, which is picked up by the CPAP despite the DC converter and confusing the CPAP somehow. Has anyone else experienced this?

I noticed most people use lower amperage keepers (i.e. 1-2 amps), maybe using one of these avoids this problem? 

Any shared experience or advice is appreciated!

Dax

[Crimson Nape]

Hi Daxvex! -
It may be dependent on your power supply type. Is it a charger or a maintainer? A battery maintainer, often referred to as a battery tender, is a device designed to keep a battery in an optimal state of charge over an extended period, such as during long-term storage. It differs from a battery charger in that it is specifically designed for long-term battery maintenance rather than rapid recharging.

Also, after power up, the display may remain illuminated for 5–7 minutes.

- Red

[RNeil]

Many battery chargers provide pulses rather than a steady current. These pulses can interfere with electronic equipment. The charger probably works well for its intended use, charging the battery in your car. There are ways to filter out the noise, but the easiest is to charge when not using the CPAP or get another charger. If a lower current charger generates noise, it would be less, and less likely to cause problems.

[Daxvex]

Hi Red! Thanks for the response!

Yes, exactly. I'm using a charger as opposed to a keeper. I didn't think it would make a difference when I put everything together. Unfortunately, I don't have a keeper to test with. Also, I was hoping not to run down the battery a bit every night since the CPAP is probalby using more than 2 Amps. I'm just wondering if the problems I'm seeing could be caused by using a charger instead of a keeper.

The screen stays on for far longer than 5-7 minutes. It will also randomly turn on when not in use with the charger attached. Since the charger is somewhat directly attached to the DC converter, the charger is functioning as a sort of power supply unit and it wouldn't at all surprise me to learn that a battery charger doesn't make a good power supply for the electronics in a CPAP, but I wanted to check if anyone else had seen this issue before I go buy a keeper just for testing.

Thanks,

Dax