Temporary LiFePO4 battery charging solution?

[Firstascent]

Hey all,

I have 16, 280Ah 3.2v cells for my project and a Batrium BMS. But, that's all I have so far so can't do much with it. Right now the cells are fine, they are all connected in parallel hovering right about 3.2v.

I will eventually do some type of Victron inverter/charger but in the meantime I was wanting to charge the batteries and play with the Batrium BMS for fun while I'm waiting but I don't want to necessarily buy a separate charger that I'll never use again.

I have an Optimate LFP 4s 5A charger I use for my lithium motorcycle batteries etc. I'm thinking I could separate my cells into 4s packs and use the Optimate to charge them and watch it on the BMS? This is a link to the company website for the model I have if it helps at all ( https://optimate1.com/oml4s5a/ )
I'm sure it would charge slowly but I have time since I have plenty more equipment to purchase still ha!

Let me know what you guys think. If I have to buy a cheap charger I can, but I'd rather not if I don't have to

 

[Fred S]

Since your cells are all balanced, I don't see any problem with making four 4s packs and placing them in parallel to charge them with a 4s LiFePO4 charger. I would monitor each cell from time to time for the first few charges. 5a is pretty small, charging will take a while. I don't know if the Batrium can be set up for that arrangement, I guess it can. If not, you could add a LVD device to disconnect the charger if the voltage gets above say 14.0v or so, as a backup failsafe.

 

[Firstascent]

Since your cells are all balanced, I don't see any problem with making four 4s packs and placing them in parallel to charge them with a 4s LiFePO4 charger. I would monitor each cell from time to time for the first few charges. 5a is pretty small, charging will take a while. I don't know if the Batrium can be set up for that arrangement, I guess it can. If not, you could add a LVD device to disconnect the charger if the voltage gets above say 14.0v or so, as a backup failsafe.

Thanks for your input, and what I was thinking too. Yes the 5A will be slow, but like I said, since I don't have the rest of my components I can wait days for it to charge

And yes, one thing I love about the Batrium is it takes me 15 seconds to change the config for any series/parallel config of my battery bank, so I'm covered from a BMS perspective.

Aside from the longer charge time, any difference in connecting a single 4s pack vs 4s4p? I'm thinking no, just higher capacity --> longer charge time.

 

[Fred S]

Some will say it would be better, if you're paralleling all 4 packs together, to parallel the individual cells rather than parallel the 4s (i.e. 12v) packs. But with new and balanced cells, the difference is not very significant. As far as charging each 4s pack one at a time, versus all at once, no real difference except the charge rate, again because you're starting with balanced healthy cells.

P.S. I guess your Batrium won't work anyway with only 4 cells in 4s, or 4 groups of paralleled cells in overall 4s? I'm not familiar with the bms.

 

[Firstascent]

Thanks, yeah this just for now for testing purposes.

It'll be a 24v system (2p8s) in the end but I don't have a 24v charger until I get the Victron but want to get familiar with the BMS for now.

The Batrium will work in ANY config. I have 16 individual cell monitors I can install on each battery. In the config I can tell it I have, 4s, 16s, 4s4p, 2p8s, anything! I'll be able to monitor temperature of Each cell which is cool too.

In the beginning I didn't know what I was going to do (24v vs 48v and what battery pack config), so that's one reason I went with the Batrium because it can handle whatever I throw at it, and expand to many more cells if I wanted, which I'm not doing though.

 

[Firstascent]

Does anyone know of a cheap charger that would charge my 24v pack? Even if it’s slow?
Depending on price I’m thinking of just getting something to charge my 24v setup, this way I can at least get the battery pack wired correctly with my BMS so it’s ready to go.

 

[tictag]

Does anyone know of a cheap charger that would charge my 24v pack? Even if it’s slow?

Plenty of options out there e.g. Samlex, Stirling, Victron, CTEK etc

Or you could buy a desktop power supply and charge at 29.2V, for example, here.

 

[schmism]

If you are going to charge through the BMS (so you have proper cutoff) Then why not just configure them for 12v pack and charge with a normal 12v car battery charger? (again hooked up through your BMS - do not connect the 12v FLA battery charger directly to a 12v Li pack)

 

[Firstascent]

Plenty of options out there e.g. Samlex, Stirling, Victron, CTEK etc

Or you could buy a desktop power supply and charge at 29.2V, for example, here.

Thanks for the examples, most of those are more expensive than I want to spend right now but the desktop power supply at ~$65 would be perfect! This is just a temporary solution. I see you listed Victron, I'll eventually be for sure ordering a Victron. I'm just working with them on a timeline/possibility of a Multiplus-II 120v unit. So that's why I'm just looking for something cheap I can hook up for some testing in the meantime. Definitely not required, but I'd be ok with $65 to be able to test.

If you are going to charge through the BMS (so you have proper cutoff) Then why not just configure them for 12v pack and charge with a normal 12v car battery charger? (again hooked up through your BMS - do not connect the 12v FLA battery charger directly to a 12v Li pack)

I have a 12v Optimate charger already I use for my lithium batteries I have in motorcycles etc. But now I'm considering finding a cheap 24v charger for now because then I can wire my pack how it's final config will be and get the BMS wired appropriately (cell monitors and busbars etc).

 

[tictag]

but the desktop power supply at ~$65 would be perfect!

Please don't take this as a recommendation, I have no experience with this product. I personally have a Rigol DP711 bench power supply, and can certainly recommend that, but this would be way more [spec] than you need to simply charge a battery.

 

[Firstascent]

Please don't take this as a recommendation, I have no experience with this product. I personally have a Rigol DP711 bench power supply, and can certainly recommend that, but this would be way more [spec] than you need to simply charge a battery.

Thanks for the updated info! Yeah I will have to look at some models to see what would suit me best. Maybe my dad has use for one then it would make sense to spend a little more if it will still get used. Thanks for the link to what you use and recommend, I appreciate it!

 

[tictag]

You're welcome. When you start looking you will come across two distinctly different types: Linear (transformer-based) and Switched-Mode (transistor-based). The latter will be the far cheaper option, whereas the former offers rapid transient response and very low noise ... you won't need this kind of spec for battery charging.