Victron Energy BCD 402 diode battery combiner (40A) powering radio from two isolated 12V systems

Very interesting product for very specific use cases - in my application it allow to combine 24V military gas generator with AC-DC industrial PSU while preventing back-flow of power into any of those sources since they have different operating voltages.

[@sharpblad3]

thanks for the video! I got 2 batteries, 1 is 120ah gel deep cycle and the other 150ah lead acid.
only used for work at the back of my van and I figured out this is the best way to use them both safely. charging with 1 solar panel split on 2 pwm controllers.
so they charge and being used separately, yet together the loads!
I wonder if from the diode is there any kind of voltage/capacity balancing. meaning if there is a high draw, will it split in balance from both sources or what?
I guess it will be from the higher voltage source as in the video. but what if the voltage drops and equals the other ? will it split ?

[@ElectronicNoobBlog]

You are correct - as voltage equalize current will flow from both but there came into play ohm law and internal series resistance of battery so It's close to impossible predicting how it behave and most like won't be 50/50 since both batteries are build different way so there will be no intelligent balancing at all - battery with lower ESR will push more current than one with high but both will be dragged down to same voltage potential.
Also recharging from two PWM controllers might introduce dangerous loop since most like they are not isolated - so You will technically join those two batteries in parallel before diode combiner - so it might produce unexpected results - not saying it will but it it's not protected from back-feeding something might happen. In general diode combiner You use with two separated sources not single one. Maybe You are looking for Cyrix-ct (from Victron) - -this is relay that make priority for recharging main battery and leave second untouched unless there is high current demand - or You put signal into "start assist". Try checking out documentation - maybe this is exactly what You are looking for - but I need to warn You - I never had one since I had different situation than Yours.

[@sharpblad3]

@@ElectronicNoobBlog
hi, thanks for the answer.
yes I was afraid that there is a potential paralleling between the solar controllers. which I don't think so but cause u said so, I ve found these : AVCXEC Solar PV Connector, Pack of 2 DC M-C-4 Plugs, Solar PV Connector Parts with Built-in Anti-Backflow Diode, IP67 Waterproof for Connecting Solar Panels (30A)
so I will buy 2 for the red wires and connect them between the solar cable split and each controller. it will protect the panels and the controllers from each other.
Cyrix-ct is paralleling the batteries in some cases and I want to avoid that.
probably I will add some Low Voltage Switches too.
what I do is so waste of money though 😂
if I knew it last year I would make a 1kw lifepo4 with the same money I ve spent for 100 tiny improvements 🥲

[@ElectronicNoobBlog]

@@sharpblad3 It's always like that! I also spend to much money playing around - but at end of the day You got knowledge. When You get it running let me know how it went!