8s charger from balance plug

[cwah]

Guys,

I've just found this:

http://www.alibaba.com/product-gs/523921637/LiFePO4_or_Li_ion_RC_Battery.html

An 8S charger from the balancing port. Voltage is adjustable!

Isn't that what we need for a foolproof and easy bulk charging solution? Get 3 of them and you can bulk charge your 24s pack!

 

[deVries]

Ask her for price and minimum quantity to order... let us know what you find out.

 

[dogman dan]

An RC lipo charger that actually charges each cell individually, and stops charging each cell individually when full would be very nice. Not sure if that techincally is called balanced, but all cells at thier max capacity, or rather the max voltage you choose, may be better than "balanced" at a lower capacity. Set em for 4.1v, and you betcha by golly.

That would not be bulk charging at all, but the best solution, individual cell / cell group charging. Even if the rate was only 50w per cell, that would still be a decently fast charge.

Following that link, looks like it is an 8s individual cell charger. Based on input amps and volts, about 250-300w. That's a good rate, so two of em would charge a 16s pack at about 500w total. About a 1 hour charge for a 12s 10 ah pack for example. Sweet! Hope they become avaliable to buy one by one soon.

GOOD FIND Dude! 8) 8) 8) 8)

 

[Jeremy Harris]

That does look interesting. As already said, charging individual cells like this is far preferable, to bulk charging, in terms of keeping the pack well balanced. My only word of caution would be that 8A is really pushing the capability of JST balance port connectors, they can just about manage 2 or 3A, any more would probably lead to them melting. Not really a problem for a pack where the balance ports are paralleled and then heavier leads are brought out to the charger.

It'd be nice to see if we could find a price for small quantities of these, as I'd have a couple.

 

[The Mighty Volt]

Neat, keep us posted, well done.

8s is such a popular basic format, whether for a 24v pedelec or right up to a 72v build.

 

[deVries]

Ask her for price and minimum quantity to order... let us know what you find out.

I put in a request for a sample w/pricing info...

 

[dogman dan]

The way I interpereted it, you'd be charging at 8 amps total, so an amp per cell? If so no problemo.

On the other hand, I balance my lipos about monthly. They need it a lot less, but I get to fretting and just run a regular balance charge. Lipo packs that need balancing often need to get chucked in the bunker of spare cell packs. So this charger fixes a problem that scarcely exists.

But when you do need to balance, bet this does it a LOT quicker.

 

[dumbass]

Please foregive me but I must be missing something. If your dealing with lifepo4 cells how is this different then 8 2a single cells chargers installed in a case? To me the 8 single cell chargers are actually better because 1) they don't require another power supply because they are 110v ac to dc and 2) their putting out an individual 2a charge. I agree it's pretty and would be nice if it were ac to dc so you wouldn't need another power supply. I've been extreamly happy with my single cell chargers and they were easy to build into a plastic/alm box.

Bob

 

[Jeremy Harris]

Please foregive me but I must be missing something. If your dealing with lifepo4 cells how is this different then 8 2a single cells chargers installed in a case? To me the 8 single cell chargers are actually better because 1) they don't require another power supply because they are 110v ac to dc and 2) their putting out an individual 2a charge. I agree it's pretty and would be nice if it were ac to dc so you wouldn't need another power supply. I've been extreamly happy with my single cell chargers and they were easy to build into a plastic/alm box.

Bob

AFAIK, the single cell 2A chargers only do LiFePO4 cells (assuming they're the the Voltphreak type). The chargers being discussed here do the higher charge voltage needed for LiCoO2 LiPo.

 

[dumbass]

Thanks Jeremy, I relize that yous are talking about lipo cells and not lifepo4 cells. But the original add on Alibaba indicated it was for both. And honestly I had forgotten there seams to be a problem getting single cell chargers for lipo cells.

Bob

 

[dogman dan]

It also said the voltage was adjustable. Perhaps not easily user adjustable, but it sounded like you could get them set to 4.1 or 4.2v, your choice.

This should balance packs quicker than regular RC chargers that stop charging and start slooooowly trickling out power from one or two cells. I've found that once you have a pack .1v out of balance, it's quicker to just hook that single cell up to a charger and let it finish at 1 amp.

Are the voltphreaks chargers user adjustable for voltage? Do they taper the end of a charge enough to be safe for RC lipo?

 

[Jeremy Harris]

Are the voltphreaks chargers user adjustable for voltage? Do they taper the end of a charge enough to be safe for RC lipo?

AFAIK they are only available for LiFePO4, not LiCoO2, and aren't user adjustable. They do effectively taper as they switch from constant current to constant voltage at the end of charge, but then pretty much any single cell charger does that inherently, just reducing current as the cell voltage rises.

 

[etriker]

Interesting. It would have to stop charging, read the voltages then start charging again over and over until charged ?

When the balance connector is used to read voltage the current has to go low so the voltage seen at the charger won't sag because of the small wires and connectors on the balance wires.

That's what the Hyperion does. Stops charging and reads the voltage and starts again over and over until the cell is charged.

 

[Jeremy Harris]

Interesting. It would have to stop charging, read the voltages then start charging again over and over until charged ?

When the balance connector is used to read voltage the current has to go low so the voltage seen at the charger won't sag because of the small wires and connectors on the balance wires.

That's what the Hyperion does. Stops charging and reads the voltage and starts again over and over until the cell is charged.

No, all it does is charge each cell to a set voltage. It's essentially exactly like the DC-DC converter chargers I've built, and that Doc Bass and a few others have built. If you charge via the balance port, rather than via the pack power terminals, then you can simply use a current limited, fixed voltage supply to charge each cell to the set point. What happens is that the cell voltage initially drags the charger voltage down and puts it in current limited mode, then as the cell voltage rises the current decreases until the point where the cell is at the set voltage of the charger.

It's really a very nice and simple way to charge cells, with very little risk of imbalance. The down side is that you can only put 2 or 3 A through a typical RC pack JST balance connector and leads, so the charge current per sub-pack is limited and the charge connection has to have a lot of pins that can carry the required charge current.

 

[etriker]

Interesting. It would have to stop charging, read the voltages then start charging again over and over until charged ?

When the balance connector is used to read voltage the current has to go low so the voltage seen at the charger won't sag because of the small wires and connectors on the balance wires.

That's what the Hyperion does. Stops charging and reads the voltage and starts again over and over until the cell is charged.

No, all it does is charge each cell to a set voltage. It's essentially exactly like the DC-DC converter chargers I've built, and that Doc Bass and a few others have built. If you charge via the balance port, rather than via the pack power terminals, then you can simply use a current limited, fixed voltage supply to charge each cell to the set point. What happens is that the cell voltage initially drags the charger voltage down and puts it in current limited mode, then as the cell voltage rises the current decreases until the point where the cell is at the set voltage of the charger.

It's really a very nice and simple way to charge cells, with very little risk of imbalance. The down side is that you can only put 2 or 3 A through a typical RC pack JST balance connector and leads, so the charge current per sub-pack is limited and the charge connection has to have a lot of pins that can carry the required charge current.

Yet it is so small. I would like to see inside it.

Most of the new chargers are microcomputer controlled with a charging flowchart. I am thinking this one is too. For charging safety reasons for sure.

I would love to see the Hyperion charging flowchart !

 

[Jeremy Harris]

Yet it is so small. I would like to see inside it.

Most of the new chargers are microcomputer controlled with a charging flowchart. I am thinking this one is too. For charging safety reasons for sure.

I would love to see the Hyperion charging flowchart !

It's described as having separate DC DC converters for each channel, so will be identical in principle to the DC DC converter chargers a few of us have built. No need for microcontrollers or anything complex, just simple isolated power supplies for each cell. This is probably safer than having a microcontroller just because it's so much simpler to implement.

I've built a couple of these, they really are pretty foolproof. Here's one I built a while, using fifteen 16A DC DC converters set to 4.15V each:

View attachment 1



Set to maximum charge current these could charge a 15S LiCoO2 LiPo pack at around 1kW...................

 

[Arlo1]

There seems to be a few of these popping up. I just ordered one that will do bunch of different packs up to 6s from dealextreme for $80 I also still have 31 isolated 20 A 4-5 v power supplies like Jeremy has, but Ive just been so dam busy. http://endless-sphere.com/forums/viewtopic.php?f=31&t=41107

 

[etriker]

If no mpu then I guess you could use cell logs to shut things down if a charging problem

I like a mpu watching the voltages .

 

[Jeremy Harris]

If no mpu then I guess you could use cell logs to shut things down if a charging problem

I like a mpu watching the voltages .

No need for it. It's inherently safe, because it uses separate supplies for each cell. Think of it as a series of fixed voltage power supplies, with built in over voltage and over current protection (as pretty much all supplies like this have). Why would you want to add another, redundant, set of voltage sense connections, with the inherent risk of another failure mode?

Those converters in my DIY charger like this even shut themselves down if they get too hot, or get short circuited, then start up again as normal when all's OK.

You don't fit a microcontroller to monitor your household supply, or the voltage from the DC supply feeding an RC charger, so why bother with doing the same to this?

 

[etriker]

If no mpu then I guess you could use cell logs to shut things down if a charging problem

I like a mpu watching the voltages .

No need for it. It's inherently safe, because it uses separate supplies for each cell. Think of it as a series of fixed voltage power supplies, with built in over voltage and over current protection (as pretty much all supplies like this have). Why would you want to add another, redundant, set of voltage sense connections, with the inherent risk of another failure mode?

Those converters in my DIY charger like this even shut themselves down if they get too hot, or get short circuited, then start up again as normal when all's OK.

You don't fit a microcontroller to monitor your household supply, or the voltage from the DC supply feeding an RC charger, so why bother with doing the same to this?

Most rc chargers will read out the input voltage from the power supply and shut down if it goes out of range.

I may be one of the few people on here that gets up early Sat morning , puts on a Frank Zappa record and watches the Hyperion charge up a pack with a readout on a computer monitor.

 

[Jeremy Harris]

Most rc chargers will read out the input voltage from the power supply and shut down if it goes out of range.

I may be one of the few people on here that gets up early Sat morning , puts on a Frank Zappa record and watches the Hyperion charge up a pack with a readout on a computer monitor.

I accept you might want to look at the voltages for fun and amusement, but if the charger is just so bog-simple that all it can do is give a fixed, preset voltage per cell, then there's no need to monitor it at all. I mean, do you monitor your cell phone or laptop LiPo when it's charging? The 'phone and laptop almost certainly doesn't, as the majority of devices that use LiPo cells just use one of the many fixed voltage charging chips, that are really all that these chargers are (except they use an array of them).

The problem with the RC chargers is that they aren't all that reliable and are subject to both user error and reliability issues (only one of the three I've bought still works, one died minutes after being first plugged in the second died a few months later). Witness the issues that people have had with the false voltage readouts from the Hyperion, for example. Looking inside some of these RC chargers I'm a bit surprised that more don't fail, TBH, as they are often running pretty close to the limits and they aren't exactly designed for high reliability. It's the latter point that scores with single cell charging, with one fixed voltage charger per cell, as it needs no monitoring, just a robust voltage/current regulator per cell, which is pretty cheap and simple stuff to implement.

 

[etriker]

I would get false readings from the Hyperion sometimes when it would be balancing at the end of a charge.

That is when the balance connectors have the most current flowing in them.

Sometimes the alarm would go off.

Ended up being flakey connections on the balance board and balance connectors.

The hyperion balance board is kinda like the one in the first post.

The balance connectors on the Hyperion are too small and flakey too.

I bought some high quality connectors and that is my next project. Upgrading all my balance wires and connectors.

 

[Punx0r]

Set to maximum charge current these could charge a 15S LiCoO2 LiPo pack at around 1kW...................

I take it this would require upgrading the balance leads and connector? Not a big job really.

 

[cwah]

I've also found this one to charge up to 15s at once:

http://www.hobbyking.com/hobbyking/store/__10708__Turnigy_X5_3S_5_port_Lithium_polymer_Battery_Charger.html

But when I see the review from HobbyKing, it doesn't seem to work very well and go into flame lol. Probably better not to buy it

 

[Jeremy Harris]

Set to maximum charge current these could charge a 15S LiCoO2 LiPo pack at around 1kW...................

I take it this would require upgrading the balance leads and connector? Not a big job really.

I limited it to half power, by fitting low value current limiting resistors in the outputs, so in practice I only ran it at about 8A. It charged a 4P pack, so that's only 2A per balance port connector, which is just about OK. I'm about to try a 4S version on my new boat pack, which has 14 4S packs wired in parallel (giving a 14.8V nominal, 70 Ah, pack). For this I'm going to let it charge at the full 16A that the converters will run at, as that'll only be a little over 1A per pack, so by no means a fast charge.