Small 12v charger advice

[Paul_R]

I'm going to put two new 12-volt 300ah in series and I want to bring them up to full charge separately first. Looking for a small charger to do that with. I don't want to buy junk and ruin my batteries but I don't want to spend way more $$$ than I have to. Any advice would be greatly appreciated, thank you.

 

[DThames]

Do the batteries have a BMS? If they have a BMS, almost any power source will work.

 

[Paul_R]

Do the batteries have a BMS? If they have a BMS, almost any power source will work.

Yes they do have a BMS. How would you know when the battery is fully charged using a power supply like that one?

 

[DThames]

Yes they do have a BMS. How would you know when the battery is fully charged using a power supply like that one?

You set the power supply to what you want your charge voltage to be. For example 14.2v, 14.4v, or whatever your goal is. The max current will be preset by the power supply or some of the supplies, have an adjustment so you can set your own current limit. The battery will come up to your set voltage after some initial charging and then as the charge cycle completes, the amps will go to zero, or approach zero. When zero or near zero, it is fully charged. You need an amp meter to monitor the amps. See meter links below for examples but there are many meter options.

Note that the charger doesn't (normally) do anything to charge the battery other than be a source of power. When the voltage is high enough and the battery needs power, it flows as a result of the nature of the electrical circuit. If for LiFePo4 you keep your charge voltage a bit below 3.65v per cell, (3.50v-3.55v) the amps will go to zero unless you have a bad cell. If you try to push to 3.65v per cell, the amps will get very low but maybe not go to zero. There is no normal need to push beyond 3.60v per cell. Going to 3.6v over 3.5v will allow the charge cycle to finish a bit sooner.

Panel meter
Clamp on meter

 

[Paul_R]

Thank you!

 

[GrumpyOldRetiree]

Take a look at: https://www.amazon.com/gp/product/B082LV7RKL/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I have both the 5A and the 20A Expert Power chargers. They both still work after 1 year of intermittent service. The 5A will be slow going to "fill" a 300AH battery from a low SOC, but it does get the job done in a "set and forget" fashion.

 

[Paul_R]

Take a look at: https://www.amazon.com/gp/product/B082LV7RKL/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I have both the 5A and the 20A Expert Power chargers. They both still work after 1 year of intermittent service. The 5A will be slow going to "fill" a 300AH battery from a low SOC, but it does get the job done in a "set and forget" fashion.

Just yesterday Amazon said the 5A units were backordered thru January. And today, bang, Six in stock. Thanks!