I would like to use solar charge controller to get from 48v to 12v. Need suggestion.

[Roswell Bob]

My 48v Sears Die Hard lead-acid pack is about dead. I am doing a 48v LiFePO4 pack to replace it. But first I am doing a 12v LiFePO4 battery pack to run lights and small TV at night. I want to get some experience with the LiFePO4 with a smaller 12v pack before I put the 48V pack together.

So I have been thinking 12v chargers, and buck converters and so forth. I think best deal maybe a MPPT controller to charge the 12v pack, and put it on the dead 48v Die Hard pack. I will run it when the sun is shining and voltage is above 50v or so.

I am looking for a decent MPPT charge controller for $200 or so. I think 30 or 40 amps should be plenty. Got any advice for manufacturer/Model? If you have something you like please let me know.

Thank you
Roswell Bob

 

[pollenface]

Victron for MPPT, but you'd have to spend a bit more.

I've had a couple of Epever Tracer AN's for a couple of years and I don't recommend them due to voltage spiking caused by cloud edge effects and heavy loads drawn from the system during charging, the controller just isn't fast enough to adjust the charging voltage which causes 1 second spikes of 31.2v (24v system).

 

[rmaddy]

I'm confused about what it is you are trying to accomplish in the short term. You will have a 12V LiFePO₄ battery. You seem to want to connect the 12V battery to the battery terminals of the solar charge controller (SCC). Do you have solar panels that will connect to the SCC? How are the dead Die Hard batteries to be used in this setup?

Do keep in mind that not all SCCs can handle both 12V and 48V so if you do end up buying one for both voltages be sure you get one that does support both. Also note that many SCCs will only autodetect system voltage once. So if it's initially setup for 12V you will need to explicitly tell it to use 48V when the time comes.

 

[Roswell Bob]

I'm sorry. I wasn't very clear. I ordered the Lishen 280Ah cells a year ago and they never showed up. I am scrambling to get something together now. I don't have experience with these cells so I don't want to jump right into the 48v system until i get some experience with the 12v system first.

The lead acid array, that I bought 6 years ago, is about dead. I want to use the MPPT charger between the dead lead acid array and the new LiFePO4 array. I know it sounds crazy but a similar 120vac charger or DC-DC converter is about the same price. The MPPT is a better deal and I will eventually move the 12v array to a mobile installation and MPPT charger will be useful.

During the day when I am not home I will set it up so that when the lead acid voltage goes above 55v or so I will allow the 12v LiFePO4 array to charge. At night wife and I watch tv and run small light and phone charger loads. We are running a 4300w generator to watch tv now

So charger has to handle 50vdc to 60vdc input side and 12v on output side.

 

[Roswell Bob]

Victron for MPPT, but you'd have to spend a bit more.

I've had a couple of Epever Tracer AN's for a couple of years and I don't recommend them due to voltage spiking caused by cloud edge effects and heavy loads drawn from the system during charging, the controller just isn't fast enough to adjust the charging voltage which causes 1 second spikes of 31.2v (24v system).

Yes, I am looking at the Victron 100v/30a unit. Also the - https://www.homedepot.com/p/Renogy-...rce=shoppingads&locale=en-US#product-overview

 

[Roswell Bob]

Victron for MPPT, but you'd have to spend a bit more.

I've had a couple of Epever Tracer AN's for a couple of years and I don't recommend them due to voltage spiking caused by cloud edge effects and heavy loads drawn from the system during charging, the controller just isn't fast enough to adjust the charging voltage which causes 1 second spikes of 31.2v (24v system).

These 31.2v spikes are on a lead acid system? I would think a lithium system with a very low resistance would snub whatever current you could send to it.

 

[Rednecktek]

The lead acid array, that I bought 6 years ago, is about dead. I want to use the MPPT charger between the dead lead acid array and the new LiFePO4 array. I know it sounds crazy but a similar 120vac charger or DC-DC converter is about the same price. The MPPT is a better deal and I will eventually move the 12v array to a mobile installation and MPPT charger will be useful.

Aaahhh, so you want to use the 48v Die Hards to be a "fake PV array" and let the SCC convert the 48v from the DieHards to 12v to the LiFe?

Yeah, totally do-able. Don't get too wound up about the SCC. Since you're just using it as a temp setup for a 12v system, you should be fine with a decent name-brand MPPT like EPEver or even a Renology or HQST. Yes, Renology isn't doing too well but their products are still a decent affordable simple option.

 

[pollenface]

These 31.2v spikes are on a lead acid system?

Yes AGM system

 

[bobkart]

I have a 48V LFP pack (16S) on my electric boat for propulsion. I have plans to have a separate 12V LFP battery for accessory loads, and would use something like this to keep it charged from the main pack:

Mean Well RSD-500C-12

It handles a wide input voltage range and can supply a current-limited 420W of 12-14VDC, adjustable via potentiometer. I'd probably run it around 13.45V as that's 96% SOC for a 4S LFP module.

 

[Roswell Bob]

I have a 48V LFP pack (16S) on my electric boat for propulsion. I have plans to have a separate 12V LFP battery for accessory loads, and would use something like this to keep it charged from the main pack:

Mean Well RSD-500C-12

It handles a wide input voltage range and can supply a current-limited 420W of 12-14VDC, adjustable via potentiometer. I'd probably run it around 13.45V as that's 96% SOC for a 4S LFP module.

Thank you. I am going to get one of these - https://www.trcelectronics.com/ecomm/pdf/ddr480.pdf Also going to get their largest charger for the 48V pack I am building.

I spoke to application engineer at TRC yesterday and we believe this will work fine. have bought quite a bit of Meanwell products from TRC Electronics. I just finished my first 12v pack using the EVE 280Ah cells. I bought a charger and a small inverter from them. Their shit works well and comes from the good China - Taiwan.