8s charger from balance plug

[deVries]

I've gotten no response despite a simple inquiry for pricing & minimum quantity per order. Plus, asked if I could pay for a sample to test before quantity purchase.

I suggest if anyone is really interested in these, then you should request order information and pricing too. It's best to catch them online, after 9pm in USA/Canada, otherwise you often don't get a reply.

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...

 

[etriker]

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.

If RC chargers are not all that reliable and are subject to both user error and reliability issues why would this RC charger be different.

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

You don't know they quality or what is inside it at all. I would guess that the quality is about the same as other RC chargers.

For sure not the quality that the ones you built are.

 

[Jeremy Harris]

If RC chargers are not all that reliable and are subject to both user error and reliability issues why would this RC charger be different.

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

You don't know they quality or what is inside it at all. I would guess that the quality is about the same as other RC chargers.

For sure not the quality that the ones you built are.

Simple.

It doesn't work the same way! I've been trying (and seemingly failing) to describe the big difference in approach between single cell charging (which is what these balance port chargers use) and bulk charging with cell sensing (which is what the microcontroller based RC chargers use), to no avail.

An ordinary RC charger passes all the charge current through the main power terminals of the pack. It senses the cell voltages, and does a very crude process of cutting the charge, allowing the highest cells to drain off, then resuming the charge, repeating this sequence until the pack is balanced. It's grossly inefficient (because a lot of charge power ends up as heat dissipated during the cell discharge periods), takes a long time, and is subject to sensing errors by the charger, dodgy balance port connectors, etc.

The parallel balance port chargers charge each cell separately, from an isolated fixed voltage supply, with current limiting during the initial charge phase. They don't need any form of control, as they will inherently balance a pack extremely well, with virtually no wasted power. They will also balance faster, as there is no requirement for discharging then recharging.

 

[etriker]

If RC chargers are not all that reliable and are subject to both user error and reliability issues why would this RC charger be different.

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

You don't know they quality or what is inside it at all. I would guess that the quality is about the same as other RC chargers.

For sure not the quality that the ones you built are.

Simple.

It doesn't work the same way! I've been trying (and seemingly failing) to describe the big difference in approach between single cell charging (which is what these balance port chargers use) and bulk charging with cell sensing (which is what the microcontroller based RC chargers use), to no avail.

An ordinary RC charger passes all the charge current through the main power terminals of the pack. It senses the cell voltages, and does a very crude process of cutting the charge, allowing the highest cells to drain off, then resuming the charge, repeating this sequence until the pack is balanced. It's grossly inefficient (because a lot of charge power ends up as heat dissipated during the cell discharge periods), takes a long time, and is subject to sensing errors by the charger, dodgy balance port connectors, etc.

The parallel balance port chargers charge each cell separately, from an isolated fixed voltage supply, with current limiting during the initial charge phase. They don't need any form of control, as they will inherently balance a pack extremely well, with virtually no wasted power. They will also balance faster, as there is no requirement for discharging then recharging.

I bought lots of laptop battery packs on ebay and tested the cells.

Some cells will not charge up all the way and get hot. The B6 would sit there trying to charge until the timer shut it off.

The current would go low at the end of the charge and the voltage on the cell would drop then the charger would increase the current and try to charge it up again.

The cell would get warmer and warmer.

'That is why good RC chargers have a capacity shut down, timer shut down, over temp shutdown and the such.

Without safety features like that a charger could get weak cells overheated ?

It is more than fun and amusement.

It is serious study !

I tried the packs I bought on ebay in my laptop and the same thing.

Some packs would not charge all the way up and get the whole bottom of the laptop hot trying to charge.

I don't like to get my cells hot unless it is on the grill !

A setup like you are talking about would be ok with all good cells and all but if something is not right or a cell or cells go weak it won't know what to do ?

 

[deVries]

A setup like you are talking about would be ok with all good cells and all but if something is not right or a cell or cells go weak it won't know what to do ?

If a weak cell goes high in voltage, then it just cuts the charge to that specific cell. Simple enough.

The LED lights would give feedback for a weak cell just by observing the "cycle lights" occasionally.

Obviously, you should not use these cells if you don't check cell level voltage sometimes, and/or, at least, have an LVC that actually protects each cell from dying.

 

[etriker]

A setup like you are talking about would be ok with all good cells and all but if something is not right or a cell or cells go weak it won't know what to do ?

If a weak cell goes high in voltage, then it just cuts the charge to that specific cell. Simple enough.

The LED lights would give feedback for a weak cell just by observing the "cycle lights" occasionally.

Obviously, you should not use these cells if you don't check cell level voltage sometimes, and/or, at least, have an LVC that actually protects each cell from dying.

They get shorts in them and won't reach 4.1v with low current. The power put into them turns into heat.

I have seen lots of laptop cells that will do this. That is one of the things they do when they start to fail.

They have temp sensors but still get hot in the pack on the laptop.

It keeps trying to charge them too.

 

[deVries]

They get shorts in them and won't reach 4.1v with low current. The power put into them turns into heat.

I have seen lots of laptop cells that will do this. That is one of the things they do when they start to fail.

They have temp sensors but still get hot in the pack on the laptop.

It keeps trying to charge them too.

We're talking about eBike RC batteries -not single cell laptop. It's a different chemistry if L-ion. :?

Bad cells need to be detected and not used in an eBike battery. Bad RC LiPo cells that are not dead will go high even with 1A-2A charger. Bottom line, you can't depend on any charger to do your safety for you! You have to choose a charge method and use it within those safety parameters.

Low amp single cell chargers with a timer shut-off protection are as good as it gets in the simplest & lowest cost categories. RC chargers fail all the time too! If I want simple & foolproof, then I do NOT want RC Xs charger. Also, it's much cheaper to replace one single cell charger that failed for $10 vs $100 for a decent RC charger that still needs a power supply too.

The OP 8s charger in this thread is a bit different, since it requires a PS. Also, it won't be easy to replace a failed single cell charger inside this unit of 8s. Therefore, I just talked myself out of using this one. I prefer simple repair & replacement too.

I won't be ordering a sample... unless these are amazingly cheap... someone else can do this one...

 

[etriker]

They get shorts in them and won't reach 4.1v with low current. The power put into them turns into heat.

I have seen lots of laptop cells that will do this. That is one of the things they do when they start to fail.

They have temp sensors but still get hot in the pack on the laptop.

It keeps trying to charge them too.

We're talking about eBike RC batteries -not single cell laptop. It's a different chemistry if L-ion. :?

Bad cells need to be detected and not used in an eBike battery. Bad RC LiPo cells that are not dead will go high even with 1A-2A charger. Bottom line, you can't depend on any charger to do your safety for you! You have to choose a charge method and use it within those safety parameters.

Low amp single cell chargers with a timer shut-off protection are as good as it gets in the simplest & lowest cost categories. RC chargers fail all the time too! If I want simple & foolproof, then I do NOT want RC Xs charger. Also, it's much cheaper to replace one single cell charger that failed for $10 vs $100 for a decent RC charger that still needs a power supply too.

The OP 8s charger in this thread is a bit different, since it requires a PS. Also, it won't be easy to replace a failed single cell charger inside this unit of 8s. Therefore, I just talked myself out of using this one. I prefer simple repair & replacement too.

I won't be ordering a sample... someone else can do this one...

Laptop cells and A123 26650 cells are the ones I know the best. They are what my etrike runs on.

They are not cheap li ion that's for sure.

I am still learning about li ion. I have learned that cheap chargers and cheap batteries are not for me.

Have learned a lot using the Hyperion hooked to a computer and cell logs. Money well spent for learning about li ion.

You can't know your cells too well.

 

[999zip999]

Dodgy cell balnce connectors but I use HK 6s ext. to the hyperion package ones, What could be wrong with that ? Junk ( HK balance wires ext. ) . I got to go and get the ebuddy ones.

 

[Jeremy Harris]

[
I bought lots of laptop battery packs on ebay and tested the cells.

Some cells will not charge up all the way and get hot. The B6 would sit there trying to charge until the timer shut it off.

The current would go low at the end of the charge and the voltage on the cell would drop then the charger would increase the current and try to charge it up again.

The cell would get warmer and warmer.

'That is why good RC chargers have a capacity shut down, timer shut down, over temp shutdown and the such.

Without safety features like that a charger could get weak cells overheated ?

It is more than fun and amusement.

It is serious study !

I tried the packs I bought on ebay in my laptop and the same thing.

Some packs would not charge all the way up and get the whole bottom of the laptop hot trying to charge.

I don't like to get my cells hot unless it is on the grill !

A setup like you are talking about would be ok with all good cells and all but if something is not right or a cell or cells go weak it won't know what to do ?

Sorry, but the message clearly isn't coming across clearly!

If you charge using a single cell charger (which is what these balance port chargers are) then there is no need for sensing. What do you mean by a "cell going weak"? Cells are either OK or they are not OK. If they are OK they will accept charge to the charger fixed terminal voltage and then stop accepting charge. If they are not OK they won't accept charge. It's very simple, if you supply a regulated voltage to a cell if it's OK it will charge up to that regulated voltage. If it isn't it won't and you throw it away. You can even charge cells with different capacities in a string with balance port charging, all that will happen is that the higher capacity cells will take longer to charge.

Here's an example of a bad pack with reduced capacity, but that still sort of works OK:

Say we have four cells in series that are supposed to be 5 Ah each, but one cell has lost capacity and is now only 4 Ah.

Put this on a conventional RC charger, like the Hyperion, and it will charge until the lowest capacity cell reaches cut off voltage. It will then stop charging and turn on a bleed resistor across the lowest capacity cell to discharge it a bit. Once it's done this it will resume charging until it again cuts off, probably because the lowest capacity cell has reached cut off voltage again. It''ll keep doing this for a while, repeatedly charging all the cells, pausing and discharging the lowest capacity cell, then resuming until all the cells reach the set cut off voltage. In the process it will have cycled the already low capacity cell many times, because the only way this type of charger can put charge into the cells is through the neighbouring cells. This is not a good way to get best life from a pack, but happens to be a way to get a rough and ready fast charge, which is what the model aircraft people want (they want a fast turnaround on the field).

Now, let's look at what happens if we charge at a lower current through the balance port, using individual cell chargers like the thread topic. The lowest capacity cell will still reach cut off voltage first, but the charger will just stop charging that cell at this point, the other cells will continue to charge as before. The charger doesn't need to switch on and off, or discharge any cells, as it's really a lot of separate chargers in one box. The remaining cells will reach cut off when they are charged and full charge will be indicated by all the charged LEDs showing. The lowest capacity cell doesn't get cycled at all, so gets no further stress to shorten its life. This is far and away the best charging strategy for a pack because of this. It's also inherently safe, as charge current isn't being forced through cells that are at, or close to, cut off, as can happen with the normal RC charger if cell sensing partially fails. If a cell connection is dodgy with the parallel charge method then it's inherently fail safe, as it just stops charging that cell, with no impact at all on the other cells.

 

[etriker]

Your idea that the lowest capacity cell will reach cut off voltage first is not correct in the real world.

They will in an ideal world but in the real world your idea is only sometimes true.

Sometimes the lowest capacity cell will not charge up to the cutoff voltage.

If there is a cut off voltage then the charger would need to know the voltage on the cell so it could cut off.

If there is current flowing through the balance lead there will be a voltage drop and the voltage on the cell will be lower than the voltage in the charger.

When laptop cells get old or weak they get shorts inside.

A123 26650 cells do to.

They will still charge and discharge but have lower capacity and will get warm while charging.

Some laptop cells will get real warm trying to charge.

The shorts inside them are making them discharge at the same time you are trying to charge them.

A charger like you are talking about will just sit there and keep trying to charge it because the voltage won't go to 4.1v on the cell with a small current trying to charge it.

You could make the voltage go to 4.1v on these cells with higher current but then they will get real hot.

That is what they sometimes do when they start to go bad.

I don't know if the charger in the first post has the needed safety features to deal with some of the real world problems that pop up with battery pack charging. I am guessing it does and does have a mpu that controls the charging.

I don't know why you are so sure they copied your design being as you have not seen it inside.

 

[Jeremy Harris]

Your idea that the lowest capacity cell will reach cut off voltage first is not correct in the real world.

They will in an ideal world but in the real world your idea is only sometimes true.

Sometimes the lowest capacity cell will not charge up to the cutoff voltage.

If there is a cut off voltage then the charger would need to know the voltage on the cell so it could cut off.

If there is current flowing through the balance lead there will be a voltage drop and the voltage on the cell will be lower than the voltage in the charger.

When laptop cells get old or weak they get shorts inside.

A123 26650 cells do to.

They will still charge and discharge but have lower capacity and will get warm while charging.

Some laptop cells will get real warm trying to charge.

The shorts inside them are making them discharge at the same time you are trying to charge them.

A charger like you are talking about will just sit there and keep trying to charge it because the voltage won't go to 4.1v on the cell with a small current trying to charge it.

You could make the voltage go to 4.1v on these cells with higher current but then they will get real hot.

That is what they sometimes do when they start to go bad.

I don't know if the charger in the first post has the needed safety features to deal with some of the real world problems that pop up with battery pack charging. I am guessing it does and does have a mpu that controls the charging.

I don't know why you are so sure they copied your design being as you have not seen it inside.

First off, I'm afraid your wrong, the lowest capacity cell in any bulk charged pack, where the charge current is being fed via all the other cells in the pack, will ALWAYS, repeat ALWAYS be the cell that reaches cell cut off voltage first. No ifs, buts, or maybes, this is ALWAYS true, unless there is a serious cell fault. If there is a serious cell fault then no matter what sort of charge regime you use it will remain.

If there is a cell fault with a typical RC type charger, then it may sense it as a low cell and give a warning, or it may not and just sit there trying to charge and discharge it for a long time. Either way the pack won't charge properly. If there is the same cell fault with a parallel charger, then that cell won't charge, and the charger will indicate it. In both cases there should be an indication of the cell problem, but in the RC type bulk charger this may well take a long time to become apparent, as the charger will possibly go through a lot of attempted balancing cycles before either flagging an error or, more likely, just timing out and not giving a definitive indication of a problem, unless you take the time to look at the charge log on a PC, perhaps, if the charger is so equipped (and many aren't).

I have a feeling that you know very little about the chemistry at work in lithium polymer cells, from some of the terms used. The charge/discharge process is quite different to that in other types of secondary cell. As such, it's very straightforward to determine how a cell will behave under given conditions, and equally straightforward to build in safety features to any charger to minimise the risk of failure. This is actually easier to do with cell level chargers, as the problem reduces to a simple one of ensuring that each charger in the string has a well-defined CC/CV characteristic, and also has things like over-current and over-voltage protection.

Finally. please don't tell lies about me, it's offensive. Not once have I claimed, suggested or hinted that any of these commercial products, quote: "copied your design" (meaning a design of mine) as you allege, what's more I haven't once ever claimed that the chargers I've built ARE actually my design, all I did was build them. Read back and you'll see I made mention of others who have done pretty much the same as I've done, my comment earlier in this thread was this, quote: "It's essentially exactly like the DC-DC converter chargers I've built, and that Doc Bass and a few others have built". I actually believe that the first person here on ES to build a charger like this was Doc Bass, maybe four years ago. The description in the advert for this charger says, quote:

"8 independent DC/DC inverter and to realize parallel balance charging and high charge efficiency.
Charging mode: CC and CV charging to ensure 100% full charge, superior to common series charging plus balancer stuff"

which states pretty clearly that this is a parallel charge, DC-DC converter for each cell charger, which appears to be exactly the same topology that a few of us have already used with success.

 

[etriker]

I do know that if you have a pack that needs to be balanced a lot then:

The cells were not matched well in the first place.

There is a bad connection in the pack.

Your cells are getting old like mine are.

If you have a good pack then keeping it balanced is not a big problem.

If you want a charger that will handle a pack with problems like needing to be balanced a lot then the charger in the first post is not the way to go. I would rather fix the pack.

Sorry if I offended you with the copy design stuff.

Thanks, Steve

Will shut up now.

 

[Arlo1]

I do know that if you have a pack that needs to be balanced a lot then:

The cells were not matched well in the first place.

There is a bad connection in the pack.

Your cells are getting old like mine are.

If you have a good pack then keeping it balanced is not a big problem.

If you want a charger that will handle a pack with problems then the one in the first post is not the way to go.

Sorry if I offended you with the copy design stuff.

Thanks, Steve

Will shut up now.

Dude with a statement like that it proves how very little you know. A pac with problems whether its balance problems or the cells have more capacity then others will BE BEST TO BE CHARGED WITH A CHARGER LIKE IN THE FIRST POST! I REPEAT IT IS BEST TO CHARGE WITH THE BALLANCE WIRES ON A BAD BATTERY. This is how you bring up the lowest cells with out overcharging the hi cells. I have had packs with cells go way out of whack and I used 4.2 volt power supplies to bring back the lowest so I could save my pack!
It might be best if for now on you only post with questions. PS a bad connection in the pack will cause the whole pack not to flow current properly or at all effecting all cells.
Current in a series curcuit is the same in the whole curcuit!

 

[etriker]

I do know that if you have a pack that needs to be balanced a lot then:

The cells were not matched well in the first place.

There is a bad connection in the pack.

Your cells are getting old like mine are.

If you have a good pack then keeping it balanced is not a big problem.

If you want a charger that will handle a pack with problems then the one in the first post is not the way to go.

Sorry if I offended you with the copy design stuff.

Thanks, Steve

Will shut up now.

Dude with a statement like that it proves how very little you know. A pac with problems whether its balance problems or the cells have more capacity then others will BE BEST TO BE CHARGED WITH A CHARGER LIKE IN THE FIRST POST! I REPEAT IT IS BEST TO CHARGE WITH THE BALLANCE WIRES ON A BAD BATTERY. This is how you bring up the lowest cells with out overcharging the hi cells. I have had packs with cells go way out of whack and I used 4.2 volt power supplies to bring back the lowest so I could save my pack!
It might be best if for now on you only post with questions.

Ok, did you see the inside of the charger in the first post ? I did not. I don't know that anyone on here has or even tested one and it is better than a Hyperion ? Hello ?

There is a lot to be said for reading and asking questions but doing tests is part of it too and I have done lots of tests.

I do not see how the charger in the first post can be better than a Hyperion with a usb port.

If you think it is then buy one and go for it. Charge through your balance ports all day for all I care.

I like to charge fast then ride ! Hyperion does that.

 

[Arlo1]

You just said for a battery with isuses. YOU 100% NEED TO ADD OR TAKE POWER AWAY THROUGH THE BALLANCE WIRES IF YOUR BATTERY HAS ISSUES! So why would you think its better to charge though the main wires then short out the ballance wires on the hi cells to balance it??? Like your Hyperion charger does. How does it make any sense to waste extra energy to do this???

AND YOUR HYPERION CHARGER PUTS JUST AS MUCH STRESS ON THE BALLANCE WIRES TRYING TO BRING DOWN THE HI CELLS!
I have 31 isolated supplies like jeremy has. I am building a quick balance charger so the wife can hook them up and walk away and not worry about over charging.
The charger in the first post will use the same thing and will have the inherent safety of not having the voltage available to wreck or over charge any cells because of its design!
Charging at the cell level is the safest way. And if you are only charging 1p then maybe you should use thicker balance wires but who has 1p e-bike packs???
I'm running 3p in my e-bike and 6p in the electric dune buggy. So the 8amps/3 = 2.666 amps or 8/6= 1.3333 amps and you think that will hurt my balance wires

PS Jeremy is one of the smartest guys on the forums he REALY knows his shit!

 

[etriker]

You just said for a battery with isuses. YOU 100% NEED TO ADD OR TAKE POWER AWAY THROUGH THE BALLANCE WIRES IF YOUR BATTERY HAS ISSUES! So why would you think its better to charge though the main wires then short out the ballance wires on the hi cells to balance it??? Like your Hyperion charger does. How does it make any sense to waste extra energy to do this???

AND YOUR HYPERION CHARGER PUTS JUST AS MUCH STRESS ON THE BALLANCE WIRES TRYING TO BRING DOWN THE HI CELLS!
I have 31 isolated supplies like jeremy has. I am building a quick balance charger so the wife can hook them up and walk away and not worry about over charging.
The charger in the first post will use the same thing and will have the inherent safety of not having the voltage available to wreck or over charge any cells because of its design!
Charging at the cell level is the safest way. And if you are only charging 1p then maybe you should use thicker balance wires but who has 1p e-bike packs???
I'm running 3p in my e-bike and 6p in the electric dune buggy. So the 8amps/3 = 2.666 amps or 8/6= 1.3333 amps and you think that will hurt my balance wires

PS Jeremy is one of the smartest guys on the forums he REALY knows his shit!

The reason I say the Hyperion would be better is because it will alarm and shut down charging a pack that has cells that are hard to balance. Then you troubleshoot the pack.

I study packs at the ends of their life and the Hyperion will show charging problems right away.

The charger that Jeremy talks about offers little feedback about the condition of the pack.

The Hyperion gives a lot of feedback about the condition of the pack when charging.

That is why I like stuff with usb ports.

 

[Jeremy Harris]

Thanks Arlo.


Steve,

If you want to fast charge a typical pack made up with RC type LiPo cells, then you pretty much have to charge through the power leads, as you can only put a limited amount of current through the balance leads (maybe 2 to 3 A per sub-pack). This is why RC chargers are designed the way they are; not because it's the best way to charge (it isn't), but because it's pretty much the only option for really fast charging (and by fast charging I means charging at 2C or above) currently available, weight sensitive, packs. The really big market is with the RC aircraft, car and boat folk who like to recharge packs in the field in less than 1/2 hour if they can. The whole RC market is skewed very heavily to batteries, chargers, motors and controllers that can handle very high current for short periods of time, as that is how the majority of customers for this stuff want to use it.

Ebikes rarely need discharge rates of more than 2 or 3C sustained, maybe 5 or 6 C continuous, as the majority want a battery life of at least an hour, which implies a 1C or less average discharge rate. Similarly we don't usually need to recharge in less than 1/2 hour (although it can be useful at times). We are a tiny bit of the RC equipment market, so the manufacturers haven't really looked at giving us what we want, hence all the experiments that go on here on ES.

Sooner or later the ebike market will get big enough for the RC equipment manufacturers (and others, perhaps) to start looking at what we need. I suspect that when that starts to happen we'll see some technically better solutions becoming available, ones that better meet our needs.

WRT the Hyperion. It's OK, but only in as much as any other RC-focussed fast charger is OK. It's far from technically excellent, in terms of charging cells for best life, or even safety (as some have already shown with the way it can glitch and misread). It's designed to meet the needs of the RC model folk, who aren't usually too worried about making battery packs last for a year or two, they usually just want a fast turn around on the field and maximum performance from a pack for a few minutes, at high discharge rate.

What feedback do you really need, from a charger? For me, an individual indicator that tells me that each cell is still accepting current, or has reached a preset cut off voltage, is fine. The charger that's the subject of this thread has an individual indicator for each cell, so gives this information. If you get a problem (indicated by a light not going out or changing colour) then it's easy enough to plug a cellog in and see what's going on.

Finally, just because something produces a fancy plot on a screen doesn't mean it's always telling the truth! We've already seen instances here where the cell voltage graphing function of the Hyperion has been found to be in significant error, not surprising given the way it tries to measure cell voltage.

 

[etriker]

Thanks Arlo.


Steve,

If you want to fast charge a typical pack made up with RC type LiPo cells, then you pretty much have to charge through the power leads, as you can only put a limited amount of current through the balance leads (maybe 2 to 3 A per sub-pack). This is why RC chargers are designed the way they are; not because it's the best way to charge (it isn't), but because it's pretty much the only option for really fast charging (and by fast charging I means charging at 2C or above) currently available, weight sensitive, packs. The really big market is with the RC aircraft, car and boat folk who like to recharge packs in the field in less than 1/2 hour if they can. The whole RC market is skewed very heavily to batteries, chargers, motors and controllers that can handle very high current for short periods of time, as that is how the majority of customers for this stuff want to use it.

Ebikes rarely need discharge rates of more than 2 or 3C sustained, maybe 5 or 6 C continuous, as the majority want a battery life of at least an hour, which implies a 1C or less average discharge rate. Similarly we don't usually need to recharge in less than 1/2 hour (although it can be useful at times). We are a tiny bit of the RC equipment market, so the manufacturers haven't really looked at giving us what we want, hence all the experiments that go on here on ES.

Sooner or later the ebike market will get big enough for the RC equipment manufacturers (and others, perhaps) to start looking at what we need. I suspect that when that starts to happen we'll see some technically better solutions becoming available, ones that better meet our needs.

WRT the Hyperion. It's OK, but only in as much as any other RC-focussed fast charger is OK. It's far from technically excellent, in terms of charging cells for best life, or even safety (as some have already shown with the way it can glitch and misread). It's designed to meet the needs of the RC model folk, who aren't usually too worried about making battery packs last for a year or two, they usually just want a fast turn around on the field and maximum performance from a pack for a few minutes, at high discharge rate.

What feedback do you really need, from a charger? For me, an individual indicator that tells me that each cell is still accepting current, or has reached a preset cut off voltage, is fine. The charger that's the subject of this thread has an individual indicator for each cell, so gives this information. If you get a problem (indicated by a light not going out or changing colour) then it's easy enough to plug a cellog in and see what's going on.

Finally, just because something produces a fancy plot on a screen doesn't mean it's always telling the truth! We've already seen instances here where the cell voltage graphing function of the Hyperion has been found to be in significant error, not surprising given the way it tries to measure cell voltage.

Right ? The Hyperion is the best charger I have been able to buy.

I have several other cheap chargers that I don't use anymore. Should have never bought them.

I have a feeling if I bought the charger in the first post it would be sitting not used like they are.

The only readout I trust is my Fluke meter and none of my chargers match it.

Yeah, cheap chargers suck. The Hyperion is the best sucky charger I have found.

And yeah the market is wide open for a good ebike battery charger.

I am starting to think it won't come from China.

Thanks, I like talking about batteries and chargers with you. Steve

 

[Ykick]

+1 Arlo and Jeremy...

 

[etriker]

+1 Arlo and Jeremy...

Hi, what kind of charger do you use and why do you like it ?

It's ok to say. ` I did.

I have built many battery packs from recycled cells and ride almost every day and do not own a car.

I shared some things I have learned from doing this and it was ok.

Please don't believe any of it and get some laptop cells and old A123 cells and do tests yourself.

Did you know that if you discharge a laptop cell hard it will get warm and sometimes the voltage will start to rise during discharge ?

 

[deVries]

Did you know that if you discharge a laptop cell hard it will get warm and sometimes the voltage will start to rise during discharge ?

Could you graph that with your Hyperion?

 

[etriker]

Did you know that if you discharge a laptop cell hard it will get warm and sometimes the voltage will start to rise during discharge ?

Could you graph that with your Hyperion?

I guess so.

I was using the Fluke meter to be sure.

Discharge the laptop cell hard at 5 amps and watch the voltage drop then drop the discharge to 1 amp and watch the voltage go up while discharging at 1 amp.

Hey, you can put a bunch of old not working Dewalt 36v battery packs and non working laptop batteries in front of me and I can make kick butt ebike packs out of them using the Hyperion to test the cells first.

I am proud of them too ! How can you kids be proud of a pack made with HK RC lipo ? I don't get it.

http://i180.photobucket.com/albums/x218/biodiesel_2007/SUNP0018.jpg

My way of seeing the whole li ion thing may not be the same as yours but then again we both get down the road, right.

That is the bottom line. Right ?

 

[Jeremy Harris]

Discharge the laptop cell hard at 5 amps and watch the voltage drop then drop the discharge to 1 amp and watch the voltage go up while discharging at 1 amp.

Of course it does.

Most cells behave like this when discharged beyond their rating for a time then have the discharge rate decreased. It's pretty fundamental to the way cells work, and is down to a couple of effects. The first is that higher than rated discharge current causes the cell to heat up from power loss (I²R loss) primarily, that is the resistive loss in the cell. Cell internal resistance (IR) is temperature dependent - make the cell hotter and its IR increases, which increases the I²R loss, which then makes the cell hotter still, etc, etc. Lower the discharge current and the cell starts to cool, as the I²R loss will have dropped (in the case of going from 5A to 1A the I²R loss will drop a great deal). As the cell cools, IR drops, reducing the resistive loss so terminal voltage increases.

I'm shocked that someone so obviously expert on the best cell charging methodology as yourself should find this surprising....................... :wink:

 

[deVries]

Did you know that if you discharge a laptop cell hard it will get warm and sometimes the voltage will start to rise during discharge ?

Could you graph that with your Hyperion?

I guess so.

I was using the Fluke meter to be sure.

Discharge the laptop cell hard at 5 amps and watch the voltage drop then drop the discharge to 1 amp and watch the voltage go up while discharging at 1 amp.

I would still like to see your first statement at the top "graphed" with your Hyperion.

...if you discharge a laptop cell hard it will get warm and sometimes the voltage will start to rise during discharge ?