The answer to your topic title is "yes". But the answer to your actual post is...it probably isnt' practical.
It's all about the Wh and efficiency of each stage of conversion. You've got some testing to do to get those, and then math to work out the results. Below are some steps to help you start:
The Mighty Volt said:
To counteract that, i have got some big, deep-disccharge lead acid batteries.
Figure out the usable Wh of those LA (probably between 1/2 and 3/4 of what they are "rated" for, at best).
Figure out the Wh you'll be using (and thus needing to recharge) out of the ebike packs you'll charge with them.
Figure out the efficiency of ebike pack charging method.
Figure out the Wh of the other things you'll need to draw out of them.
Total up the last two, and subtract from the first. That will tell you how much you'll be able to do before you need to recharge the LA. (which you will want to do every time you use them, right after you do so, or you'll wear them out quickly).
I can parallel these and invert them to get some AC power for charging my ebike batteries.
You said you have an RC charger?
Then don't waste their power in conversions, just run the RC charger off them directly--that's why they are made to work on car batteries.
Otherwise you will be wasting probably more than half of the Wh of the LA, and yo'll be wasting lots of time charging the LA up that you don't have to, because of heavy conversion losses in the inverter and then in the AC power supply for your charger.
HOWEVER....how do I charge these lead acid batteries back up, or at least keep them topped up.
Best: take them somewhere you can charge them.
Otherwise you are wasting a lot of time charging something else so you can inefficiently convert that Wh into charging the LA, and then transporting that intermediate pack back and forth to do the charging. Anything up to half or more of teh Wh you used to charge the intermediate source will be wasted in converting it's power into Wh for the LA, and some more will be wasted in moving it back and forth becuase you'll have to keep recharging your ebike batteries from the trips to do the intermediate charging.
I have seen these "powerbanks" that being used to kick-start cars , they are usually rated up to 16000Ah, or thereabouts.
I have a feeling that you are confusing "power" capability with "capacity" capability, in that just because something has enough power to jumpstart a car (a very short process), doesn't mean it has much capacity.
As discussed elsewhere on ES, at least some of those specs these things are advertised for are complete lies (even assuming you mean 16Ah, because you couldn't move the size pack you describe without a large freight truck
).
Or they may not be *complete* lies, but just deceptive in that they may contain a total of 16Ah of cells but at only single-cell voltage (if LiPo, then ~4.1V at 16Ah, if LiFePO4, then 3.6V at 16Ah)
At best (and unlikely), they'll be 12V-14V at 16Ah, which even if it has a converter to keep the output voltage *at* the 12V-14V as the internal batteries discharge, will still not deliver all of that Wh out to the charging LA--probably 3/4 of it at best, because of inefficiencies.
So....let's make up some numbers, since you didn't provide any details on your stuff. I'm using numbers that are easy to divide up just for my own use; you'll need to provde the real numbers for any useful calculations:
Assume LA are total of 200Ah @ 12V for "rated" Wh of 2400Wh.
Assume ebike packs are total of 10Ah @ 48V for 480Wh, and assume you use the whole thing every day.
Assume efficiency of charger system hooked directly to LA without inverter of 75%, so it's going to take 1.34x the Wh you use up to recharge the packs.
Assume other devices use 2000Wh total each day, including the losses in the inverter/etc to convert the LA power for their use.
So actual Wh used every day will be at least 1.34 x 480Wh =
643.2, + 2000Wh = 2643.2Wh total used each day.
That means that even if you totally discharged the LA for 2400Wh there is still not enough to do what you need to do.
So you'll have to charge up the ebike packs, then use them to take the intermediate packs somewhere to charge them, then bring them back just so you can finish whatever you are doing, *and* recharge the ebike packs again with whatever Wh it takes to do your outbound and inbound trip for that.
Ok, so now...let's assume the *best* (and unlikely) case of those powerpacks being 12v at 16Ah, giving them 192Wh each. Assume you get 75% of that out of them after conversions...144Wh.
Ok, so even if you directly connect those to your RC charger to charge your ebike packs (much better than first charging the LA and *then* charging the ebike packs with the LA), it will still take at least 4 of the powerpacks to recharge the ebike packs.
To fully charge the LA each day to do everything with the numbers I made up above, you'd have to have at least 18 of those powerpacks...and that's assuming they actually really are 16Ah at the full voltage from start to finish, and don't lose capacity as they age, etc.
It's more likely they are ~4V at 16Ah (or less), whcih nets you 64Wh at best. So you would need at least 41 of them to do everything, with those numbers I made up for your usage.
Or of course, have only 5 of them, and make at least 8 trips back and forth somewhere to charge them up. Probably more like 10 or 12 trips, cuz you will now need to recharge your ebike packs again, too.
How long do they take to charge, each one?
How long does it take to get to and from the charging spot and your storage?
That's the problem with this sort of system...you can only carry so many Wh with you--it's just like refueling stations--in order to refill something you first have to move all the energy from one place to another, and it takes energy and time to do that, so it doesnt' usually work out as practical unless you can carry a whole lot of wh compared to how much you actually use in transporting that wh.
Your best bet is to permanently build your ebike packs into a safe-looking object with a BMS in there so you don't have to balance it with bunches of wires to an external device, and then to use a single simple two-wire charger to it that makes it all look innocuous. Having the charger as part of the pack would be even better, cuz then you just have a normal AC cord to deal with, but you have to worry about heatsinking or ventilating it.
Then you could take it anywhere you're allowed to plug stuff in, and go for it.
If the library has noise restrictions, you could get teh Cycle Satiator from Grin, which is fanless and will charge pretty fast, up to 360W at room temperatures (less as it heats up a lot, if it's not placed where it can cool off). It even "looks safe" compared to common RC chargers and even some ebike chargers, as it looks like a large laptop brick power adapter. But it isnt' cheap. (on the flip side, it's useful for any pack and can have multiple charging profiles you can activate wheneve ryou need to, for most common ebike battery types).