I’m hoping to extend the capacity of a Goal Zero 500 Wh solar generator by essentially inserting a Victron MPPT controller and 12V 100Ah or 300 Ah Lifepo4 battery in the chain between the solar panels and the DC input of the Goal Zero. So in the diagram below, the DC Load is the DC input on the Goal Zero (12.3V - 28V, 10A max). I’d like be able to use either solar for “C” or a 24V (10A?) DC power supply when I have shore power and want to charge faster. See any issues leaping out? As an alternative, any reason to not bypass the Victron MPPT load output and just connect the battery to the DC input (with a fuse) ?
While it can work, an MPPT is not intended to be fed by a constant voltage source. Charging faster might be a stretch anyway. When using a 300Ah battery, which is discharged to 50% for example, then you would need 15h of constant 10A charging to get those missing 150Ah back
You mean you want to connect the cable going to the GoalZero directly to the battery? By using the load output you can control at which point charging will start and stop. Theres also a BatteryLife algorithm which takes the daily PV yield into account
You’ll be limited to the SmartSolar/BlueSolar 100/20, which is the largest Victron MPPT that still includes a load output. That should be enough for about 300–400 W of solar.
From what I can see, you’re using a 10 A cable into the cigarette socket for DC-DC charging. A better option could be to add a dedicated cigarette socket wired directly to the battery with a suitable fuse (around 15 A, depending on cable size).
Other approaches include using a BatteryProtect (VSR or remote-controlled) for load management. Alternatively, there’s the Bluetti Charger 1, a universal MPPT charger made for small power stations. It accepts a 12–24 V input and can be configured to provide the correct current and voltage for charging.
Thanks for the response!
Clarifying: I would use (3) on the Yeti diagram, the 8MM charging port. What I think of as the cigarette socket (1) is a regulated output.
Can you explain more about why I would want the load output ? I understand about low voltage discharge protection for my battery (to distinguish from the Yeti battery), but my battery has that built in to its BMS. Is there something else I’m missing? A reason to NOT connect the Yeti input to the battery and so also connect it to the MPPT output?
Am I correct in thinking that you’re recommending the largest Victron MPPT (with a load output) to maximize the solar input capabilities? Or is there another reason?
Thanks! “By using the load output you can control at which point charging will start and stop”. I assume you mean charging my battery and not charging the Yeti. Can you explain more? Is that control still necessary for a LiFePo4 with a BMS and low voltage discharge protection? And is it about turning on/off the load or something else about the separation of the battery and the load in the circuit? I picture the load control as a simple relay disconnect. Are there any resources that would let me see the circuit or functional diagram inside the Victron?
“An MPPT is not intended to be fed”…I understand it’s not efficient, but can you say more about the downsides of violating this intent? Will it decrease the life of the MPPT?
I mean, it works, ive used a 150/35 fed by 110VDC before, because i just had nothing else on hand, but its not how you are supposed to use an MPPT. Youll probably void the warranty. I dont know about efficiency, probably not different than when using PV panels
The Yeti is the load, since you got another battery to charge. By using the load output you can prevent it from being over-discharged
If the 100/20 has enough charging for you, then you can use the load output. If you want to use a larger one, they dont have a load output. This is the cable that goes into that 8mm socket for charging. You can put a cigarette socket directly on the battery with a battery protector for VSR and remote control of the charger if you want. That is what I meant.
