Can I Charge A Lead Acid Battery Using A Powerbank.....

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Hi folks.

This is more of a prepper question than an Ebike question but its all interconnected.

Cut a long story short I have a rental garage which prohibits the use of generators or power generating equipment.

To counteract that, i have got some big, deep-disccharge lead acid batteries.

I can parallel these and invert them to get some AC power for charging my ebike batteries.

So no problems there.

HOWEVER....how do I charge these lead acid batteries back up, or at least keep them topped up.

I have seen these "powerbanks" that being used to kick-start cars , they are usually rated up to 16000Ah, or thereabouts.

I can charge these pretty fast and discretely in my local library

BUT my question is....can I use them to top-up lead acid batteries, or how would I go about doing this, if it is possible.

Thanks so much in advance for any suggestions.

I have basic engineering skills so please do not be shy about suggesting circuits , diodes, etc.

THank you.
 
I'm a bit confused by your post, but it sounds like you want to use a small power cell to charge large lead acid batteries. Volts flow downhill, irrespective of battery size, at least at ambient temperatures. Car stuff lives in a narrow range of voltages, and lead acid batteries produce flammable and corrosive oxygen, plus explosive hydrogen. So generally a dedicated charger is best, one designed for the battery voltage as well as whether it's flooded, sealed or immobilized electrolyte. A device designed to start a car is probably a poor candidate for charging a big 12 volt battery because the charging voltage needed, not too mention control, is unavailable. There are plenty of cheap AC chargers that can do the job, as well as solar, if you have the time and sunshine.

p.s. If one leaves lead acid batteries in a discharged state for a long time, the result is usually a very heavy brick. For long battery life limit discharge to fifty per cent and recharge immediately.

--tp
 
The Mighty Volt said:
This is more of a prepper question than an Ebike question but its all interconnected.

Really, more of a basic electronics and battery question.

Cut a long story short I have a rental garage which prohibits the use of generators or power generating equipment.

What is "power generating equipment" - a solar panel out back? Running a car?

Does the garage have a light socket you could use to power a charger?

HOWEVER....how do I charge these lead acid batteries back up, or at least keep them topped up.

You attach a charger to them. This seems straightforward. If you can't do it in the garage, you haul them somewhere you can charge them.

I have seen these "powerbanks" that being used to kick-start cars , they are usually rated up to 16000Ah, or thereabouts.

16,000 AH? Are you sure you're not thinking 16000mah (16AH)? A 16kAh battery is going to be gigantic, heavy, and not something you can charge discreetly.

BUT my question is....can I use them to top-up lead acid batteries, or how would I go about doing this, if it is possible.

You can. It'd be more efficient to run the inverter off them directly. They're not going to carry around that much power.

I have basic engineering skills so please do not be shy about suggesting circuits , diodes, etc.

Find a way to get power into the garage, or find a way to get the batteries to power. They're not magic.
 
Car jump starter/booster packs usually contain a cheap sealed lead acid battery of <18Ah. Connecting a charged LA battery to a discharged one will cause the latter to be partially charged at a slow rate. Trying to charge a large battery with a small one will mean you won't get much charging done before the voltage of the small battery falls to the same as the charging battery, at which point you're done.

Depending on your usage consider something like a 50W solar panel on the roof to trickle charge your batteries.
 
Punx0r said:
Car jump starter/booster packs usually contain a cheap sealed lead acid battery of <18Ah. Connecting a charged LA battery to a discharged one will cause the latter to be partially charged at a slow rate. Trying to charge a large battery with a small one will mean you won't get much charging done before the voltage of the small battery falls to the same as the charging battery, at which point you're done.

Depending on your usage consider something like a 50W solar panel on the roof to trickle charge your batteries.

Hi there.

I understand this is all very unusual....I think what I will do is take my powerbanks to the library, charge them up, and then buy an icharger and run the icharger off the powerbanks and just keep my big lead acids topped up.

Thanks.
 
I think you're going to have a bad time.

A 16000mah Powerbank (16AH) will run at 3.7v. So that's 60WH, near as makes no difference.

A deep cycle lead acid battery is typically 75+AH at 12v, or 900WH. So you'll need 15 Powerbanks to charge one of those, assuming full efficiency (which you won't get).

Why not just take your ebike battery somewhere to charge it? You're inventing a complicated, absurdly inefficient chain of systems to accomplish something more easily accomplished through other means.

Or stick a solar panel on the garage and top off your lead acid cells that way.
 
Syonyk said:
I think you're going to have a bad time.

A 16000mah Powerbank (16AH) will run at 3.7v. So that's 60WH, near as makes no difference.

A deep cycle lead acid battery is typically 75+AH at 12v, or 900WH. So you'll need 15 Powerbanks to charge one of those, assuming full efficiency (which you won't get).

Why not just take your ebike battery somewhere to charge it? You're inventing a complicated, absurdly inefficient chain of systems to accomplish something more easily accomplished through other means.

Or stick a solar panel on the garage and top off your lead acid cells that way.

I think you need to read up a bit on Powerbanks. Some of them run at well over 12v and are designed to jump-start cars.

I have already explained that 99% of the suggestions you insist on making are not practically feasible at my garage.

Simply. Cannot. Be. Done.

I also need the lead acids for lighting, boiling water with an element.....emergency welding without firing a generator, running my tab welder, etc.

You try bringing a LiPo battery with wires and ichargers and balance boards into a library in London, see how long it takes for the IDIOTS to work in public services to call out the SWAT teams.

But hey maybe I will just put a solar panel on the roof and bring my battery to the library na na na na na na na etc etc etc etc...
 
The Mighty Volt said:
I think you need to read up a bit on Powerbanks. Some of them run at well over 12v and are designed to jump-start cars.

Maybe you could link to something you're thinking about, because searching for "Powerbank" shows an awful lot of cell phone chargers, and I'm quite familiar with those. They're 3.7v devices, internally. Most of them will put out higher voltages, including the car starters, but their capacity rating is for a parallel bank of cells at 3.7v.

https://www.google.com/search?q=powerbank&oq=Powerbank&aqs=chrome.0.69i59j0l5.1119j0j7&sourceid=chrome&es_sm=0&ie=UTF-8

I see the PowerAll Supreme, which is a 16000mah jump starting pack: http://powerallcanada.com/supreme.html

But while it will output 12-14v to crank a car, I see nothing to suggest it's got anything other than a 3.7v cell internally, meaning it's still only packing around 3.7*16=59.2WH of energy. A far, far cry from what a big, deep cycle lead acid pack holds.

I have already explained that 99% of the suggestions you insist on making are not practically feasible at my garage.

Simply. Cannot. Be. Done.

Ok. Then I have no idea. Good luck shuttling a car jump starter back and forth a few dozen times to charge your batteries.

I also need the lead acids for lighting, boiling water with an element.....emergency welding without firing a generator, running my tab welder, etc.

It sounds like you're using a lot of power in a garage in which you are not allowed to have power/power isn't provided, with no plans for providing such power. The little gizmos you're asking about simply do not carry much energy, and are not designed for charging batteries in any case - that they will do it is a side effect, not their designed purpose.

You try bringing a LiPo battery with wires and ichargers and balance boards into a library in London, see how long it takes for the IDIOTS to work in public services to call out the SWAT teams.

If I were to do such a thing, I'd have a heat shrinked battery or some other professional looking case, I'd leave the battery and charger in my backpack to charge (after verifying the battery and charger wouldn't overheat charging in there), and sit there with a laptop charger down near my backpack as well. You could even use a little power strip so you didn't take multiple outlets. I certainly wouldn't charge it on the table!

But hey maybe I will just put a solar panel on the roof and bring my battery to the library na na na na na na na etc etc etc etc...

*shrug* I'm done. Good luck. I don't think your solution will work, and you clearly aren't allowed to have any solutions that do work, so good luck getting mains-levels of power in a garage where you're not permitted to have power.
 
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).
 
amberwolf said:
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)

I play a good bit of Ingress, so I'm familiar with these - I've yet to see anything rated for capacity at anything *but* 1S cell voltage. :/ And I've never seen a 4.1v rating.

My current pack is listed: "Li-ion cell 14000mAh @ 3.7V / 52Wh" - and all the others I've ever seen are similar.

I'm pretty sure, set up properly, it could start my truck in most conditions (assuming the cells can source the power, which is probably not the case).

I need (at 12v):
160A (1920W) for 15s to heat the glow plugs (160*12*(15/3600)) = 8WH
~500A (6000W) for 5s to crank (500*12*(5/3600)) = 8WH

So a pack my capacity that could source ~800A of 12v (whoof - yes, the truck has dual batteries) could start my truck multiple times, but it still doesn't carry much energy - it's only 1/10th the capacity of my ebike pack, and wouldn't get me more than 2 miles, tops.
 
Syonyk said:
I play a good bit of Ingress, so I'm familiar with these - I've yet to see anything rated for capacity at anything *but* 1S cell voltage. :/ And I've never seen a 4.1v rating.
The rating numbers I listed were what those cells might be at or near full charge, for the most optimistic ;) rating one might calculate wh from (not realistic).

As for ratings, we've had several "vendors" of them spam their ads on here disguised thinly at first as users, revealed as vendors quickly (sometimes immediately) and removed as spam, who didn't bother noting their actual rating...just the total Ah, and the "12v" output voltage, with no other detailed info besides (sometimes) a photo of the object and sometimes a price, sometimes size and/or weight, sometimes peak A output, etc. Hasn't happened in a while, thankfully.

None of the ones spammed on here ever said anything about the internals or the true ratings, they gave partial specs and left it up to the potential buyer to mis-assume that as the whole truth, and much greater capacity than they actually would have.

I'm sure many of them actually do what they say they will, for starting a vehicle. I also expect some of them actually have the capacity stated, for the single-cell voltage...and some of those probably also even let you use all of that Wh. :)

But having seen so many cells and batteries and devices here on ES with much lower actual output capacity vs claimed, even when properly used and balanced, etc., I doubt that most of them actually meet all their claims at the same time.

If they do, that's great--but I don't trust them to advertise truthfully, as many (most?) internet vendors don't udnerstand battery stuff and don't quote their own product spec sheets (if any) verbatim, but rather "interpret" them by giving only the big impressive numbers and leaving out little ones as unimportant (or little unnecessary units like "milli" :lol:), or just plain copying someone else's incorrect ad copy instead of bothering to make their own, thus perpetuating a mistake or a lie.

But as you also note, they have insufficient capacity to do much for long, or to act as intermediate charge holders for something like what the OP wants to do (without many of them, or many recharge trips and huge amounts of wasted time).
 
Hi guys, thanks for all of the feedback, you both make very valid points.

Yes, it is entirely possible that these figures provided by these retailers are total BS, in fact, we have been there before with them, have we not :?: :oops: Yes, we have.

Basically, what I have is as follows:

10 {ten} 12v, 7Ah Yuasa Pb batteries, taken from Emergency Lighting, almost pristine condition. So I have 12v, 70Ah, basically.

I have this {well its in the post} powerbank which claims to be able to give me 12v of charge and says it has 16Ah capacity.

Now...of course, the chances are its just a 3.7v {1s} string of cells up to 16Ah in capacity that goes through a DC-DC converter to give the 12v.

I also have numerous 4s 8p packets of old, but good, LifePO4 cells, basically 12v 6.6Ah under heavy discharge.

I have one big 36v {12} LiFePo4 battery which is split internally into three 12v batches {4s} each providing around 12Ah under heavy load.

The idea of the lead-acids, the big ones, 115Ah or so, is to use them for a few welding applications I need to get done, as I cannot run the generator at least I don't want to run it, drawing attention to myself, etc.

Those big 115Ah batteries will wear down during such use and will need to be topped up in order to give me a supply I can run my inverter with for the ebike charging.

What I am thinking now is that I will bring two of the Yuasa to the library or to the building site with me, and charge them discretely using a small smart charger, until all of them are charged.

I will then parallel them into a 70Ah block, run them into an inverter, then run that into a smart charger and top up my big lead acids until I am back fully charged on that.

Does that sound more feasible.

I understand this all sounds ridiculous but...its the best I can do.

THanks.
 
Why are you so insistent on running everything through the lead acid packs instead of using your other packs directly to provide power for almost everything you need to do?
 
The Mighty Volt said:
Does that sound more feasible.
I don't know.

Did you do the math yet?

That's how you find out if it will work (other than just doing it).
 
Syonyk said:
Why are you so insistent on running everything through the lead acid packs instead of using your other packs directly to provide power for almost everything you need to do?

Because big lead acid packs, when charged up, means I can get 3, 4, charges without having to worry about any other aspect of the "System".

If I do all my charging in the library on a Saturday and Sunday, then I can charge small batteries and top up the lead acids.

Monday, Tuesday, etc are then easy days. Maybe I will hit a bit of a flat spot towards the end of the week.
 
why not figure out a way to get 120V AC into the garage. if not then find a garage with power or where you are able to get power. nothing wrong with using an extension cord.
 
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