Dual MightyBoosts?

[Jfisher]

Hi Felix,

So my project has the following (current draws):
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RPi 3 (400 mA)
RPi Camera (250 mA)
RPi 7" Touch Screen (500 mA)
MightyBoost + Moteino (120 mA, RFM69HW @ TX)
+ LEDs, small fan, small speaker etc.

All up lets say constant 1200 mA current draw @ 5V.

The MightyBoost is designed to run at constant 1000 mA with occasional spikes to 1500 mA to avoid overheating.

What if I do run it at 1200 mA constant; does it need a heatsink but can still run reliably?

OR

Can two MightyBoosts be used in parallel while still retaining the ATXRaspi capabilities?

The 7" touch display allows for a separate power source and I can run that on its own isolated MightyBoost+Battery combo, but I want to know whether I'll have any issues if I 'bridge' both of the MightyBoost controls to run them from a single Moteino?

[Felix]

1200mA might be OK if you provide a large enough battery. I recommended specs that I know work with most batteries. So 1200 is not much more than that. Experiment and see what you get. Overheating should not be really a problem, more a drop in output voltage when the booster can't possibly make up the demand from a lower voltage, boosting is tricky.

I would NOT recommend driving 2 units in parallel (output) to make up for a larger load than designed. The outputs are used as a feedback path back into the boosters so if they are wired in parallel it will probably malfunction since they assume a single output.

[Jfisher]

I would NOT recommend driving 2 units in parallel (output) to make up for a larger load than designed.

Thanks for clarifying; I figured that would be the case.

If the total current was, for example 2000mA (outputs to separate, isolated devices, each 1000mA), can two MightyBoosts be ATXRaspi-style controlled by a single Moteino?

I imagine that the Moteino can sit atop the 'Master' MightBoost which monitors the battery and is connected to the Pi serial IO while the 'Slave' MightyBoost waits for a low-battery/shutdown signal from the 'Master'/Moteino in parallel.

Is that possible?

[Felix]

Conceptually I think it could, but I have not tried something like that. The MBoosts have some inputs that control their power output switches (mosfets).
You are limited by the amount of IO a Moteino has, but it depends if you use them with radios or not, that gives you an additional 4 IOs. Your second MBoost could simply just control the output, then you have to add one control pin to the MBoost sketch for it, and when power is cut, notify both MBoosts, perhaps that's very simplistically explained but I don't see a lot more than that.
Depending on what the real power demands and requirements/constraints I would weigh what's the easiest and more feasible option before going with a complex setup like that.