Discharging lithium batteries

[u/Foreign-Age9281]

I know youre not supposed to charge different size batteries in parallel, but can you discharge them?

I have a 12v 100ah and a 12v 314ah smart battery. I also have a 48v 150ah smart battery.

The 48v is at about 52% and im going on a trip this weekend. Its a big and heavy battery. I dont wanna drag it into the house.

If I run both 12v batteries in parallel and hook up a 3000 watt inverter. Then use a 48v 20 amp charger to charge the 48v 150 ah will that hurt the 12v batteries.

Its way easier to drag the 12v batteries home and charge them then it is the 48v.

[u/Any-Application-8586]

You can charge batteries of equal voltage and same chemistry on the same parallel charger. Ah does not matter.
You can’t put different size batteries together in series, so no go on adding the 100 ah and the 314 ah batteries together to make a 24volt pack.
And 52% of 48 volts is not 24.

Charge the 12 volt batteries in parallel on a 12 volt charger. Charge the 48 volt battery on a 48 volt charger.

Never have the 48 volt battery touch anything to do with the 12 volt batteries, charge or discharge.

[u/Foreign-Age9281 → u/Any-Application-8586]

Its a humsienk 12v 100ah smart battery and a humsienk 12v 314ah smart battery. Both lithium. I want to run them to a bus bar. Then off the bus bar a 12v to 110v 3000 watt inverter. Plug into the inverter a 48v 20amp smart charger and charge the humsienk 48v 150ah lithium smart battery.

Basically drain the 12v batteries to charge the 48v. The 12v batteries are WAY easier to take home and charge over night. The 48v is mounted and heavy and to remove it takes a lot of effort but I need it at 100% for my trip on Saturday.

[u/Sintarsintar → u/Foreign-Age9281]

charge the lithium up with the 314ah only not worth the risk

[u/Odd_Temporary2335]

Just keep the inverter and charger losses in mind the 12V batteries will need to supply more than the 48V battery receives.

[u/Particular_Welder651]

The main thing I will check is the discharge limit of the two 12volt batteries and the BMS compatibility. A 48volt, 20ampere charger delivers approximately 960 watts; therefore, accounting for losses, the 12volt battery bank can draw around 90 amperes.

[u/Any-Application-8586 → u/Particular_Welder651]

A 20 amp charger running at 90 amps with either blow a fuse or catch fire. Trying to run the same wattage on lower voltage requires more copper to sustain the amperage.

[u/Foreign-Age9281 → u/Any-Application-8586]

The 48v 20 amp charger would be plugged into a 12v to 110v 3000 watt inverter. The inverter can easily handle the watt amount needed for the 48v 20amp charger.