I don’t really know, but I would be very cautious about mixing battery chemistries. Even if the nominal voltage is the same, there is a lot other differences in how they charge/discharge. A lot of electronics goes into charging lithium batteries so they don’t turn into fireballs.
You are probably much safer with these battery packs because they have the charging circuits and protections built in.
If it was bare lipos I’d be worried that connecting the lead acid battery in parallel, as if the voltages are not actually balanced one will try to charge the other. Even with two lithium batteries I think there are risks as there are multiple lithium ion chemistries that act differently, and even with the same chemistry you may get problems if you connect up two in different states of charge.
I suppose what is safe comes down to what the charging system around the batteries are designed to expect.
I found the docs for the mothbox and it looks like it takes 12v and runs it into a buck converter that outputs to the Pi juice/etc. So you should be able to connect an automotive (sealed lead typically, or AGM) 12v battery or similar directly to the 12v barrel jack input.
What I would advise against is connecting mixed chemistries in parallel like a sealed lead/AGM car battery and the camera’s internal Li-Ion battery bank. In parallel, they’ll try to balance each other, inevitably pulling one into the ground.
100% resting for (4S)LiPo is 16.8v, (4S)LFP is 13.6v, AGM is 13v, SLA is 12.89V, (3S)LiPo is 12.6v. Lithium and lead acid don’t play well together because their voltages are to dissimilar. You can use LFP in cars because the 12v systems tend to be tolerant up to 15v (most alternators charge 14.2-14.8v).
As far paralleling two of the LiPo banks, it “should” be okay, but there’s some circuitry between the barrel jack port and batteries, so it’s hard to say how it’ll react. You could make a barrel Y-pigtail with diodes to isolate each battery bank from the other. But it mostly likely would work just fine with a simple Y cable.
If you’re looking for bulk capacity though, a car battery should work fine and be mostly tolerant of the environmental factors. Nice thing is that the moth box can utilize car batteries that are unsuitable for car use, so you could probably get them for dirt cheap or free.
Don’t forget to hook up a speaker amp to your old car battery and crank some AC/DC into the battery. High frequency AC does a good job shaking the lead plates and desulfating the battery. The amp is AC coupled, so no worries about the battery’s DC current getting into your amp and mucking it up. Does wonders for nasty old truck batteries that have been lying around uncharged for a decade.
I guess you could do the same trick with different music, but would you really want to?
You should use a blocking diode in each battery in parallel, to prevent the batteries trying to charge another battery when connected up. Schottky diodes are tempting due to the lower forward voltage, but I’d us silicon diodes for lower reverse leakage, especially since at 12V the forward voltage isn’t significant anyway.
I suggest you look into LiFePo4 batteries, the most popular for off-grid systems. and add solar panels and an MPPT charging controller, etc… so it lasts forever!
I’ve just seen this being used in another project:
It seems awesome. Big old lithium battery, loads of configurable power outputs. Including AC, high voltage DC, a programmable DC output, USB-C, or USB-A.
Can charge either on the USB-C or on the DC jack while supplying power. The DC jack is happy to charge on anything from 5V DC to 20V DC. So you can charge from a car battery, or a solar panel.
It seems to have about every form of protection built in.
The downside it it is pretty pricey. But it does seem if you power through one of these, then you charge you just wang in some DC from any other source and it handles the charging.
Also i just emailed Talentcell And they said we could hook up any solar panel that provides 14 to 20 volts as long as it’s not more than 60 watts of power. So that’s cool I think I’ll try that out later.
We have been wanting solar panels on the mothbox because it would serve three purposes really well
extend battery life (duh)
act as a rain shield above the camera lens
act as a heat shield during the day (having a clear box can potentially lead to some problems, luckily our thing only runs at night! And we haven’t actually had any problems with this)
And personally i would drop those fancy expensive power super charger banks and just go for a simple solar setup, with a decent LiFePo4 that suits your power consumption needs (with or without bluetooth, prize really depends on the capacity), a 10A MPPT charge controller shoult be enough for you. can be less than 30USD. You can always scale the panel and the battery, depending on where you set it up, sunlight etc.
You have some numbers about the power consumption of the setup?
I like the LiFePo4 batteries! but the $88, 38Ah lipo batteries we have been getting from talentcell are proportionately cheaper in cost and size and weight it seems, and in a form factor that raises fewer eyebrows when we take them on planes (even though i think the LiFePo4 are actually safer)
