Charging with Switch Mode Power Supply?

[squowse]

What would be the downsides of charging using one of these using a BMS? -



I've seen them being sold with LifePO4 batteries as chargers, well it certainly looks the same -





I'm thinking -

1) The voltage would have to be adjusted to approx 3.4 to 3.5V per series cell
2) The current wouldn't be constant - would it even draw a huge current and shut down the power supply?
3) If it charged at something like it's max current would that actually matter

4) What would be involved in adding a current control facility to these, eg reduce the voltage to obtain the correct current with a control circuit


Thanks for your thoughts, sorry if it's a frequent question

 

[snoobler]

I have several of these. Voltage output adjustable to somewhere around 14V.

https://www.amazon.com/ALITOVE-Universal-Regulated-Switching-Transformer/dp/B06XJVYDDW

A little cheaper than the unit you linked.

1) 3.4V/cell can get cells to 95% capacity
2) The PS typically has an operating voltage range. It will supply 30A provided voltage remains above X and below the set voltage. Current would be constant until the power supply senses its set voltage and will then taper current to maintain set voltage.
3) No.
4) Yep, reduce voltage to allow the voltage drop between source and battery to regulate the current. Would be very sensitive.

 

[BarkingSpider]

The trick with those DC power supplies is to use them with a cheap solar charger controller. Once connected to your 12v/24v battery, plug in the DC output where the solar panels would normally go, this charges your battery correctly. You can buy a simple (not MPPT) 30amp Solar Charger for under $30.

 

[snoobler]

The trick with those DC power supplies is to use them with a cheap solar charger controller. Once connected to your 12v/24v battery, plug in the DC output where the solar panels would normally go, this charges your battery correctly. You can buy a simple (not MPPT) 30amp Solar Charger for under $30.

How is it any more tricky than using a 30V/10A bench power supply to directly charge a 12/24V battery with a BMS installed as instructed in the top balancing guide?

 

[BarkingSpider]

It's about the same amount of work, but the big difference is your can charge up to 1000w or more vs 300w max (often much less) with the bench supply. It's much faster.

 

[snoobler]

With a 12V/30A power supply as the OP linked, you're not getting 1000W out of it. Nor will you get 1000W out of your proposed configuration with a 30A PWM controller.

 

[BarkingSpider]

You misunderstood, I'm using a 1000w dc charger with a 40amp pwm controller. It works on my 24v system fine. Confirmed with DC meters.
It's a similar setup to Wills in his recent milk crate videos.

 

[snoobler]

How does your response relate to the OP's inquiry?

 

[MattiFin]

The trick with those DC power supplies is to use them with a cheap solar charger controller. Once connected to your 12v/24v battery, plug in the DC output where the solar panels would normally go, this charges your battery correctly. You can buy a simple (not MPPT) 30amp Solar Charger for under $30.

This may or may not work. On minimum you need power supply with current limiting and even with that its not guaranteed to work.

 

[BarkingSpider]

I have had bad luck with those 10a 30v chargers on Amazon, they all lasted around a week, then blew up. They all had to be returned.
The Power supply style units (picture at top) work much better and ones that put out much more power are available. Will had the same experience and appears to be going with these PS units also. Meanwell are a quality brand, also Drok.

 

[squowse]

I have had bad luck with those 10a 30v chargers on Amazon, they all lasted around a week, then blew up. They all had to be returned.
The Power supply style units (picture at top) work much better and ones that put out much more power are available. Will had the same experience and appears to be going with these PS units also. Meanwell are a quality brand, also Drok.

I thought they were the same thing

 

[squowse]

I have several of these. Voltage output adjustable to somewhere around 14V.

https://www.amazon.com/ALITOVE-Universal-Regulated-Switching-Transformer/dp/B06XJVYDDW

A little cheaper than the unit you linked.

1) 3.4V/cell can get cells to 95% capacity
2) The PS typically has an operating voltage range. It will supply 30A provided voltage remains above X and below the set voltage. Current would be constant until the power supply senses its set voltage and will then taper current to maintain set voltage.
3) No.
4) Yep, reduce voltage to allow the voltage drop between source and battery to regulate the current. Would be very sensitive.

thanks - I was thinking of using one rated 12V 60A. They're very cheap on Aliexpress, I realise the longevity may be an issue on such a cheap unit.