I also mentioned you might want to take the precaution of diode protecting the chargers from eachother. In hindsight I don't think that's necessary. They must already be protected because they don't let the magic smoke out when you leave them plugged into the battery and turn off the mains.
Any time I've done this "fast charging" method I was relying on the battery to voltage clamp both chargers and I pulled them before "float".
Which means I don't know if the diode is in the charger or the BMS or both...so if the discharge port blows your charger don't blame me.
Law of opposing voltages unplug the battery first and mains second she'll be grand!
A few (more) Caveats:
- DC barrel connectors are 3Amp rated. They will melt if you exceed this and sometimes even when you don't.
- The BMS is on the Charge Port if you are using the discharge port to charge then you have no balance circuit on that "input". To mitigate risk I reduce the charger Absorption voltage and use the charge port with inline BMS most of the time, meaning the cells can't ever be too far from balanced.
- I'm demonstrating this with 2 chargers. You could use an MPPT charge controller on the discharge port which can handle up to 40A I believe.
- Most batteries come with a charger that will take 8 hours to charge. eg. 24Ah battery comes with a 3Amp charger.
The benefits are;
The battery does get warm when you deplete it (at 1C), it'd be a bad idea to heat it further with an aggressive charger before it can cool.
Slower charging facilitates better cell balancing and cell longevity.
DC barrel connectors are junk and can only barely handle 3Amps anyway.
- It drastircally reduces risk of catarophic failure from charging at High C rates in low temperatures
- We all know it's actually because it was the cheapest solution...
Here's a dualy I strapped together and wired into the same mains plug.
Complete with custom adapters.
Visual proof of concept using the adapters. I haven't got an XLR female to XT60 direct. Outside of this thread I've never needed one but I would make one if I was doing this in the real world just to remove the DC barrel from the 4A circuit.
Same kinda thing with a 29Ah Triangle Battery