Quick charging question - Bench top and battery

[Rednecktek]

So quick question for y'all. I recently built a toy 52Ah 24v battery and used my bench top power supply to feed my HQST 20a SCC to do the initial charge. I'm seeing that between the 32v limit on the bench supply and the voltage differential that my cells never could get over 3.5v each, so it never really got a "full charge". Can I just set my bench top charger to 29v and connect it straight to the battery or would that be a "Bad Thing"?

 

[sunshine_eggo]

So quick question for y'all. I recently built a toy 52Ah 24v battery and used my bench top power supply to feed my HQST 20a SCC to do the initial charge. I'm seeing that between the 32v limit on the bench supply and the voltage differential that my cells never could get over 3.5v each, so it never really got a "full charge".

Holding cells for > 60 minutes at 3.5V/cell is absolutely fully charged.

Can I just set my bench top charger to 29v and connect it straight to the battery or would that be a "Bad Thing"?

provided you connect with BMS protection, youbetcha. This is actually described in the top balance guide.

 

[Rednecktek]

Kewl. I didn't have the parts handy at the time to top balance so I let the BMS do the balancing, it just couldn't do the 3.65/cell that we normally top balance to.

Thanks!

 

[GSXR1000]

you need bigger wires on your charger

 

[Rednecktek]

you need bigger wires on your charger

10AWG for 24" from bench supply to MPPT, 8AWG for 24" to battery pack. Wires are plenty big enough for 10a of current, I think it was more of an efficiency thing and minimum voltage differential between a 32v power supply and a 28v battery that was the issue, just not enough overhead to really move anything past a certain point.

 

[GSXR1000]

10AWG for 24" from bench supply to MPPT, 8AWG for 24" to battery pack. Wires are plenty big enough for 10a of current, I think it was more of an efficiency thing and minimum voltage differential between a 32v power supply and a 28v battery that was the issue, just not enough overhead to really move anything past a certain point.

the voltage at the output of the SSC and the battery should be the same.. if it isn't then it's the wire or connection.. read by a volt meter

 

[Rednecktek]

They're pretty close enough to count as efficiency losses. I bet if I had a 60v supply it would have been able to push the full 29v.

As in 28.2v on the MPPT screen, 28.1v on the BMS. It just never could get up to the 29v I was hoping for.

Either way it's resting at 27.2v according to the Xioang app after sitting in the garage for a few days. Grade B cells and all.

I guess my next question is if I wanted to just go straight from bench power to battery, what voltage should I set it for?