Cheap 120v -> 29.2v Lifepo4 Charger - This a bad idea?

[mcarper]

120VAC -> 24VDC -> 29.2VDC -> BMS -> Batteries

1x 1200w DC 24v Power Supply

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3x DC-DC power converter (has current limiting) - Set to 29.2V

1500W 30A DC-DC Boost Converter Step-up Power Supply Module Out 12~90V In 10~60V | eBay

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1x 60A24V Separate Port - Feed the 29.2V into this to charge the batteries.

18.5US $ |Daly Bms Li-ion Lifepo4 Bms 3s-24s 12v 24v 36v 48v 60v 72v 29.6v 15a 20a 30a 40a 50a 60a 80a 100a 120a 150a Lithium Battery Bms - Battery Accessories & Charger Accessories - AliExpress

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$92 + $54 + $23 = $170 for an over 1000w charger.

 

[Steve_S]

Gluing this assemblage together will disappoint you and also creates 3 points of potential failure.

I would suggest a good reliable product like this for $216 (US product)
TP3020E switching power supply, tekpower

There are cheaper imports of course. If your intention is to charge only from a 110VAC source, then knowing the battery capacity is and cell type. Generally, the usual LFP folks use here prefer a charge rate of .5C or lower and will often behave best (least divergence) around .2C - .3C, so for a 100AH pack, 20-30A charge up to 50A. It is important that the charging system can reduce the amperage as the battery fills to prevent over charging.

 

[BarkingSpider]

An easier and safer solution is to take a quality power 1000w supply like a meanwell and output it thro a low cost PWM solar charge controller. You can buy a 40a one on amazon for under $30, this will correctly charge you batteries and you can use it for solar when the sun is shining. Just match the power supply output with the solar charger range it can handle.

The charger controller handles the power supply input just like a solar panel, it can’t tell the difference.
You could also do it thro a quality MPPT charger like a Triton 4215 which gives you more options. Maybe you already have a charge controller you can use? Just switch between the power supply and your solar panels as needed.

I do this and get 800w into my batteries from a generator when the sun don’t shine.

 

[mcarper]

I'm looking at making a 24v pack using 270-280ah lifepo4 cells, so I'd like a charger with some power; 1400w would be the max as to be able to use a standard 15a outlet.

In order for a PWM charger to work I'd need 30v, meanwell doesn't hit that range

SE-1000-MEAN WELL Switching Power Supply Manufacturer

MEAN WELL is one of the world's few standard power supply mainly professional manufacturers, covering 0.5 to 25,600W products are widely used in industrial control, medical and other fields, in line with international safety certification, short delivery of spot inventory.

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This can output 900w and would work with PWM, 30v @ 30a. It just costs some money but it might be the best option.

TP3030E , Tekpower supply, DC Variable power supply, Adjustable Power supply, DC Power supply

TP3030E , Tekpower supply, DC Variable power supply, Adjustable Power supply, DC Power supply

tekpower.us

Looks like I can find 30v power supplies, removing the dc-dc converters from the circuit.

AC DC 30 Volt 20/25/30/40/50 Amp Industrial Transformer Switching Power Supply | eBay

AC DC 30 V 20/25/30/40/50 Ampå·¥ä¸ååå¨å¼å³çµæº. è¾å¥çµåï¼AC 110væ220v. 100ï¼æ»¡è´è·èåæµè¯ï¼CE RoHS认è¯ï¼. 100ï¼ç§¯æçåé¦ï¼åè´¹æ´æ¢ï¼äº¤è´§è¿éï¼. 为äºå»¶é¿çµæºçåçï¼è¯·éæ©åçæ¯è®¾å¤é«20ï¼çåå·ã. æ¤çµæºè®¾å¤âä¸åâé带å®è£è¯´æï¼æ¥çº¿çµç¼ï¼å¼/å³å¼å³æèºä¸ã. IP20éçï¼ä»å¨å®¤å使ç¨ï¼. 1500Wï¼245 125 75mm.

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30v with a pwm seems like it'd work?

 

[BarkingSpider]

I used this 60a PWM controller, seems to work fine, its a throw away price.

Amazon.com

and fed it with this 1000W PS.

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If you want more power, simply buy more systems and connect them in parallel to your batteries.

 

[mcarper]

I used this 60a PWM controller, seems to work fine, its a throw away price.

Amazon.com

and fed it with this 1000W PS.

Amazon.com: YI MEI DA 24V 40A 1000W Upgrade Switch Power Supply Driver Display Switching Power Supply 24v for LED Strip Power Driver CCTV Camera 3D Printer: Computers & Accessories

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If you want more power, simply buy more systems and connect them in parallel to your batteries.

Thanks! Looks like that's all I'd need.

 

[BarkingSpider]

The only issue is those cheap controllers dont have a 29.2v LifePO4 voltage setting, so use the AGM 28v setting, that gets you 98% charged. Dont leave it on for ever, just to get the bulk charging done, you dont want equalization or long float voltages.

Remember ——— Dont ever leave that equipment running overnight or unattended. Its not UL listed.