Charging 2 batteries at once.

[aaron07]

I'm using a BC8 to charge 2 4S batteries at once. One battery has recorded 4.27 in each of the 4 cells. (above the 4.2limit) The other is 4.10 in each of the 4 cells. Is this dangerous? Why would this be so unbalanced?

[inmidair]

could it be a BC-8 calibration problem? do you have another charger you can throw it on to see if it gives you the same reading?

if you got the charger from rcaccessory i would contact him about it. sounds risky to keep charging like that. better to be safe and be waiting while your charger is on its way to the vendor then be sorry.

[tppjr]

I'm using a BC8 to charge 2 4S batteries at once. One battery has recorded 4.27 in each of the 4 cells. (above the 4.2limit) The other is 4.10 in each of the 4 cells. Is this dangerous? Why would this be so unbalanced?

The real question is what were the individual cells at with the start of the charge?

What rate were you charging at?

I assume the individual cells in each of the two batteries were pretty close to each other in voltage but the voltage of the two batteries was farther off. The balancer thinks the 8 cells are from one 8s battery and tried to bring the four cells from the higher battery down to the level of the lower battery. All this is being done at the same time you are charging all 8 cells. The balancer can only discharge 500mah per cell. My guess is that it could not bring down the high battery before it reached the 4.27.

This is the kind of stuff that can cause a battery fire. The BC8's balancer does balance the batteries IF it has time to do so at a max of 500mah per cell. The individual cell voltages are displayed on the BC8 BUT the BC8 does not use the cell information at all and will charge all cells untill it sees the total battery voltage it is looking for before it stops the charge.

For the dual battery charge to work you need to make sure that the individual cell voltage of ALL cells involved are really close to each other prior to the start of the charge which is very hard to do.

Thomas

[ke6d]

The real question is what were the individual cells at with the start of the charge?

What rate were you charging at?

I assume the individual cells in each of the two batteries were pretty close to each other in voltage but the voltage of the two batteries was farther off. The balancer thinks the 8 cells are from one 8s battery and tried to bring the four cells from the higher battery down to the level of the lower battery. All this is being done at the same time you are charging all 8 cells. The balancer can only discharge 500mah per cell. My guess is that it could not bring down the high battery before it reached the 4.27.

This is the kind of stuff that can cause a battery fire. The BC8's balancer does balance the batteries IF it has time to do so at a max of 500mah per cell. The individual cell voltages are displayed on the BC8 BUT the BC8 does not use the cell information at all and will charge all cells untill it sees the total battery voltage it is looking for before it stops the charge.

For the dual battery charge to work you need to make sure that the individual cell voltage of ALL cells involved are really close to each other prior to the start of the charge which is very hard to do.

Thomas

So how do people charge two 3s battery packs in series? Someone told me to make sure the two packs are full individually first by charging them individually. Then hook them up and balance them in series. Don't charge them until all the cells are balanced to each other.

Hook up the charger and top the battery packs in series until both of them are full. From this point on, always keep the battery packs discharge/charge/balance together.

Is this a correct procedure?

Thanks,

Dan, KE6D

[tppjr]

So how do people charge two 3s battery packs in series? Someone told me to make sure the two packs are full individually first by charging them individually. Then hook them up and balance them in series. Don't charge them until all the cells are balanced to each other.

Hook up the charger and top the battery packs in series until both of them are full. From this point on, always keep the battery packs discharge/charge/balance together.

Is this a correct procedure?

Thanks,

Dan, KE6D

Dan,

I would say to make sure that all eight of the battery cells are VERY close to each other in voltage prior to charging, I would say no more than .02 difference per cell. To be honest I would get a second charger. I have gone the route you are going before and did not like the results. For me I did not have a battery get overcharged it just took way too long to for the charge to end. It almost took longer than if I had charged the batteries seperately.

That being said I have a few Air Thunder batteries that I am trying out and have noticed that if I fly them pretty much the same and land RIGHT when the timer goes off that they have been really close to each other so I ordered a couple more balancers (I have two 902's and two PB-6 balancers now) and will try again to see if I can charge two 3s at the same time per charger. It would be really nice to be able to charge four batteries at once. Worst comes to worse If I hook two batteries up to the balancers right after flight by the time they are cooled down maybe they will be balanced to each other and all should be well. I don't think you can do that though since your balancer is internal to the charger.

Thomas

[ke6d]

Dan,

I would say to make sure that all eight of the battery cells are VERY close to each other in voltage prior to charging, I would say no more than .02 difference per cell. To be honest I would get a second charger. I have gone the route you are going before and did not like the results. For me I did not have a battery get overcharged it just took way too long to for the charge to end. It almost took longer than if I had charged the batteries seperately.

That being said I have a few Air Thunder batteries that I am trying out and have noticed that if I fly them pretty much the same and land RIGHT when the timer goes off that they have been really close to each other so I ordered a couple more balancers (I have two 902's and two PB-6 balancers now) and will try again to see if I can charge two 3s at the same time per charger. It would be really nice to be able to charge four batteries at once. Worst comes to worse If I hook two batteries up to the balancers right after flight by the time they are cooled down maybe they will be balanced to each other and all should be well. I don't think you can do that though since your balancer is internal to the charger.

Thomas

Thank you Thomas for the advice. I have the Pro-Peak Prodigy II charger now and in the process of buy the Thunder Power 1010 charger. I also have a TP205 and a TP210 balancers. I have a Hurricane EP550 that I will fly soon. The reason that I want to get the packs to be charged together in series because the Hurricane requires 2 packs to fly. I did a little bit of research and found out that the TP1010 charger is the way to go since I can see individual cell voltage with this charger if I hook up the TP210 balancer to it.

Do you foresee any problem with charging them in series using the TP1010/TP210V combination?

Thanks again,

Dan, KE6D

[zurie]

weird..

I charge 2x 3s in series... 6s 2200 mah 22 v

on my BC-6 and I never have had a problem... I also monitor my individual cell voltages as it charges and they all end up at 4.20 when its finished....

I fly them 6 minutes a pack and since I have 4 batteries, and 2 chargers I take the 2 batteries that are closest together and just use those 2 in series.

My charge times are right around 30 - 45 minutes to charge them simultaneously...

I've never experienced the balance problem you describe and I also have never had to deal with balancing two very unbalanced batteries... like you stated, that could take as much time to balance as it would to individually charge them on their own :D

[trireme]

I recently added a second FMA cellpro 4s to my collection... I have to say... owning two chargers is great!!! I I fly almost every weekday, and I had been chargin my cells in the evening one after another, but since I got the second charger... I just put em both to charge, and 40-50 minutes later, I am ready.

If I had more cash.... 5 batterys, and the ability to charge 4 of them at once.... that seems like the best method for all day flying.

[tppjr]

I have two bantam 902's and four pb-6 balancers. If I were to do it again I would get four cellpros and much cheaper to boot. You would just be SOL if you go over 4s which I do plan to do in the future.

Thomas

[tppjr]

weird..

I charge 2x 3s in series... 6s 2200 mah 22 v

on my BC-6 and I never have had a problem... I also monitor my individual cell voltages as it charges and they all end up at 4.20 when its finished....

I fly them 6 minutes a pack and since I have 4 batteries, and 2 chargers I take the 2 batteries that are closest together and just use those 2 in series.

My charge times are right around 30 - 45 minutes to charge them simultaneously...

I've never experienced the balance problem you describe and I also have never had to deal with balancing two very unbalanced batteries... like you stated, that could take as much time to balance as it would to individually charge them on their own :D


That I think is the best way to do it and is how I will try when I get the other two balancers in. Have you ever tried to hook up the two worst batteries just to see what happened? If you do, keep a close eye on everything.

Thomas

[RC Accessory]

You did not say that you were balance charging them. If that is the case and you just serial charged 2 4S packs, what you experienced can easily happen unless the cells are very evenly discharged. The charger is seeing the total voltage of a 8S pack.

The only way to do this correctly would be to create a balance wiring harness so you can balance charge the 2 packs at the same time.

There is another thread on HF that someone did just that on the BC-6. It is easy to do.

[xStatiCa]

The individual cell voltages are displayed on the BC8 BUT the BC8 does not use the cell information at all and will charge all cells untill it sees the total battery voltage it is looking for before it stops the charge.


Is this accurate for the BC8? Hypothetical scenario... If you are doing a basic balance charge with one 6s battery and have a single cell that is 1v above all the others(4.1, 3.1, 3.1, 3.1, 3.1, 3.1 for example) and you charge it you are saying that the charger would not abort the charge if the one cell got too much above 4.2 volts?

The BC8 manual has an error listed for BATTERY VOLTAGE CELL HIGH VOL that they define as 'The voltage of one of the cell in the Lithium battery pack is too high. Please check the voltage of the cell one by one.'. That seems to indicate they they do check the individual cells during the charge as a safety to prevent a single cell getting overcharged.

Btw... I realize that the scenario with the original poster is a series charge which seems dangerous to me because I thought the BC8 would abort the charge if a single cell got too far above 4.2 volts which doing a series charge would defeat the purpose of.

[RC Accessory]

Is this accurate for the BC8? Hypothetical scenario... If you are doing a basic balance charge with one 6s battery and have a single cell that is 1v above all the others(4.1, 3.1, 3.1, 3.1, 3.1, 3.1 for example) and you charge it you are saying that the charger would not abort the charge if the one cell got too much above 4.2 volts?

The BC8 manual has an error listed for BATTERY VOLTAGE CELL HIGH VOL that they define as 'The voltage of one of the cell in the Lithium battery pack is too high. Please check the voltage of the cell one by one.'. That seems to indicate they they do check the individual cells during the charge as a safety to prevent a single cell getting overcharged.

Btw... I realize that the scenario with the original poster is a series charge which seems dangerous to me because I thought the BC8 would abort the charge if a single cell got too far above 4.2 volts which doing a series charge would defeat the purpose of.

I have never seen any cells get above 4.23V on the BC-6 or the BC-8 charger and when it did the balancer brought it down to 4.20V very quickly. The only time in my experience where it did go to 4.23V per cell was on 1 cell in a very severly out of balance pack that I was experimenting with it.

The charger will terminate the charger if any 1 cell gets too high in voltage and/or the pack gets too high in voltage.

[aaron07]

Thanks for the great info. I need to rig up an adapter board to 'balance' charge the 2x 4S packs at once. I was not balance charging. The pack that reached 4.27 (Thunder Power 14.8V 2170) is now puffed, only after 4 easy break-in flights. Should Thunder Power replace this?

[ke6d]

Thanks for the great info. I need to rig up an adapter board to 'balance' charge the 2x 4S packs at once. I was not balance charging. The pack that reached 4.27 (Thunder Power 14.8V 2170) is now puffed, only after 4 easy break-in flights. Should Thunder Power replace this?

Yike, that would happen if you over charge the pack. That is why I am going to buy the TP1010 charger and use it along with my newly purchased TP210V. The charger will communicate with the balancer during charging and will stop charging if something is not right. I also like the ability to read individual cell voltage during balancing.

Bob Finless has a good video on this charger/balancer combo.

GL,

Dan, KE6D

[zurie]

i balance charge my batteries in series at the same time... each cell can independantly receive its own amperage, if i understand correctly... i thought that if you balance charge them the higher cells just charge at a lower amp and the lower cells charge at the higher amp and it magically does its thing and works out... charging them on their own, and then plugging them together to balance really doesn't make alot of sense to me??? i do the charge and balance simultaneously and i've had great results every time! just last night I charged 4 2200 3s packs in 1 hour 20 minutes.

mathematically, thats like 20 minutes a pack(x2)... balanced and all at 2.2amps.
(where it would take 40 minutes normally if you were doing each pack individually)

[RC Accessory]

Yike, that would happen if you over charge the pack. That is why I am going to buy the TP1010 charger and use it along with my newly purchased TP210V. The charger will communicate with the balancer during charging and will stop charging if something is not right. I also like the ability to read individual cell voltage during balancing.

Bob Finless has a good video on this charger/balancer combo.

GL,

Dan, KE6D

Let me it clear that the Balancer was NOT used in the way he originally charged the battery. IF the balancer was used this would not have happened. The charger operated as programmed.

[tppjr]

....................The charger will terminate the charger if any 1 cell gets too high in voltage and/or the pack gets too high in voltage.

Evan, does the BC-8 work differently with the balancer than the 902?

Thomas

[RC Accessory]

Evan, does the BC-8 work differently with the balancer than the 902?

Thomas

The only difference is that the PB-6 balancer will give an alarm in an over voltage situation (it can't terminate the charge) where the Bc-x chargers will terminate the charge. This is on a per cell basis.

The PB-6 balancers have a 500 ma discharge rate while the BC-x series chargers have a 300 ma bleed rate on the balancer.

Both chargers will terminate the charge in a pack total voltage situation and the BC-x chargers will also terminate in a cell over voltage situation.

[xStatiCa]

Thanks for the info. It is nice to know that it does what I expected it to do :). I really like the BC8 charger. It can only do ~7 amps vs the 1010c's 9amps on 6s but that is not much different and most people probably only charge close to 1C anyway. The integration of the balancer with the charger makes it very compact and the interface seems very intuitive.

[tppjr]

The only difference is that the PB-6 balancer will give an alarm in an over voltage situation (it can't terminate the charge) where the Bc-x chargers will terminate the charge. This is on a per cell basis.

The PB-6 balancers have a 500 ma discharge rate while the BC-x series chargers have a 300 ma bleed rate on the balancer.

Both chargers will terminate the charge in a pack total voltage situation and the BC-x chargers will also terminate in a cell over voltage situation.

Got it!!, thanks, I wish the 902 would stop the charge. Have you worked out your dual battery charging leads yet??

Thomas

[RC Accessory]

Have you worked out your dual battery charging leads yet??

Thomas

The PQ and Align versions are done. I started the TP and got very busy with multiple trade shows coming up. I have been rethinking the harness. I am considering doing a small pcb board instead of the wiring harness. I feel the board would be safer and definitely more durable.

[RC Accessory]

Update:

I am at the iHobby trade show in Chicago and have started the process of job costing these serial balance boards. I expect to know in a few weeks estimated costs and time frame to delivery.

Initially, we will have the following assuming all goes well:

BC-6: 2S and 3S boards
BC-8: 2S, 3S, and 4S, boards.

The BC-6 boards would also fit the PB-6 balancer so you can balance 2 3S packs at the same time.

Regards,

Evan

[TomRex]

I have two LBA6 balancers on the leads of 1 Astro 109, I double the charge and plug in 2 batts to charge. when 1 finishes up faster I reduce the input till the other one is done. Whats the question?

[tppjr]

Update:...............

The BC-6 boards would also fit the PB-6 balancer so you can balance 2 3S packs at the same time.

Regards,

Evan

Evan,

Then I would think you would add 4S to the BC-6 boards too, right?

Thomas