I have a Bluetti eb70 and I am thinking of buying a separate, stand alone LiFePO4 battery. I want charge the Bluetti with the other battery and use the Bluetti for all my DC/AC outlets. I am thinking that running cables from the LiFePO battery (or through a bus bar) to a male DC plug and then into the Bluetti will charge the Bluetti.
Has anyone tried that or have the knowledge to know if it would work?
One thing to remember is that the most watts you can draw from the auxiliary battery is around 100 if the battery is a 12 volt or 200 watts if 24 volts since the EB70 has an 8 amp input limit. It takes my EB70 around 8 1/2 hours to charge at 12 volts.
If you do get a battery, get one that is 24 volts. Doing so will double your charge rate to around 200 watts. The battery can connect direct to the PV input port. If you opt for a 12 volt battery, you will be limited to a little under 100 watts of charging
You can do that but make sure you get one with sufficient amperage. You will need 10 amps to get your 200 watts and I would get a 20 amp unit just so you are not running it at full capacity for long periods. They get quite hot. I have a 12 to 48 volt and a 24 to 48 volt that I use to do the same thing you want to do but at a higher voltage in order to charge my Bluetti AC200. There are several posts on it here.