Another parallel charging question

[milly0812]

I have 6 5000 packs that I can charge simultaneously but depending on the flight they come down after 4 mins with anything up to 25 % difference in capacity. So if I fly balls to the wind they come in with 20% left and if I fly sensibly practicing they come down with 45% left.

Is it still ok to charge all six packs with different capacities on the pl8 with para board or safer to charge singularly ?

[johnsandywhite]

I have been charging mine with different % left. If you put the charge leads in first to the highest to the lowest and then do the same with the balance leads, there should be no problems. Only time I had a problem was when I had the charge leads reversed.

[450man]

No it is not safe at all to parallel charge when the batteries have significant differing state of charge. If you do then when you plug them in the battery with the higher charge (voltage) will instantaneous charge the others. So you could easily exceed the C rating of the battery.

I have seen that they should be within 0.2V and that is what I use as my personal buideline but I have seen others that are less ridged about it. This means that in practice I nearly always charge singularly as it is rare that they come down with voltages that are that close together.

I would be interested in what others do.

[Varelco]

I don't know what the recommended limit is but I don't parallel charge packs which have more than 10% difference in capacity. For example If you had one pack at 20% and another at 60% the 60% is gone bolt 20% of its capacity instantaneously up the arse of the 20% charged pack. Not good man. Will do neither battery any favours.

[johnsandywhite]

That's a shame, because I have been doing what I mentioned for the past 18 months. I suppose I must be lucky when charging my CHEAPO Turnigy and Zippy 5000mah 6s 30c/40c Lipos??????????????????????????????????

[milly0812]

Another parallel charging question

I'm glad I posted as there seems to be greatly differing views ? Yes it's safe, no it's not safe . It is if the packs are within 10% hmmmmm so is there a definitive ??

[Tim Procter]

Never had a problem here balance charging at different levels.

Having said that most of mine come down in a similar state.

[aparkin]

and I was told to connect all your batteries up but not power up the charger for 10 to 20 mins and let all the pack balances then self's first is this true are false ??

[johnsandywhite]

For instance. Yesterday I had 2 x 6s 5000mah 30C Turnigy from my TDR with 35% left. I had 2 x 6s 5000mah 40C Zippy with 20% left, 1 zippy 40C with 14% and 1 x Zippy 45C with 23% left. Charged them ALL on a cheapo parallel board with my PL8. No BANGS, no SPARKS. Just a nice smooth plug and go charging system.

[Varelco]

and I was told to connect all your batteries up but not power up the charger for 10 to 20 mins and let all the pack balances then self's first is this true are false ??

The voltage of each pack will match each other almost instantly, there is no need to wait. I turn my charger on first before I connect my packs too.

For instance. Yesterday I had 2 x 6s 5000mah 30C Turnigy from my TDR with 35% left. I had 2 x 6s 5000mah 40C Zippy with 20% left, 1 zippy 40C with 14% and 1 x Zippy 45C with 23% left. Charged them ALL on a cheapo parallel board with my PL8. No BANGS, no SPARKS. Just a nice smooth plug and go charging system.

No one said it will bang or spark. It's just going to expose the batteries to very large charge/discharge C ratings for a brief period. The intenal resistance of a pack is virtually nothing, its literally like putting it to earth. Whether this has a detrimental effect over a long term I don't know, I'm not a battery guru but I still can't see it doing any favours.

Perhaps I'm being over cautious, then again some people don't like parallel charging at all. I think it's personal preference, I'm interested to see what every one does now.

[450man]

Once you understand what happens when you connect batteries together in parallel you will see why it isn't a good idea to do it if there is a significant different in charge.

As soon as you connect a battery to another it will try to equalise the charge. In fact, the battery with the higher charge will discharge to the battery with the lower charge. It happens almost instantaneously for our purposes. Waiting 20 mins after will have no real benefit because the bulk of the balancing will happen in the first few milliseconds and that is the problem because even if there is not a huge difference between them the discharge/charge happens so quickly that the approved C rating can easily be exceeded and you may not even know it has happened if there is no sparks or smoke.

The problem for me is that no one knows what an acceptable difference is and even worse, that "acceptable" difference will be different for each battery because every battery has different acceptable C rating before damage occurs.

The only safe way is to not parallel charge if there is anything of a difference and that is what I do.

[aparkin]

As soon as you connect a battery to another it will try to equalise the charge. In fact, the battery with the higher charge will discharge to the battery with the lower charge. It happens almost instantaneously for our purposes. Waiting 20 mins after will have no real benefit because the bulk of the balancing will happen in the first few milliseconds and that is the problem

so if we add a resister to slow your instantaneous balances and limit the amount of charge that can go from batter cell to battery cell and then let them balance before we connect to are balance chargers would this help and would any1 no how to make this possible if it is resemble

[mahbouni]

When I want to charge 6 packs I first check the voltages and sort them in order from lowest to highest. I connect the 2 lowest in parallel together and wait a few seconds for them to equalize. The 1st 2 packs must be pretty close. I like them be within 2% of each other. When I connect the 3rd pack it will discharge into 2 packs, sharing the current. The 4th will discharge into 3 packs, the 5th into 4 and the 6th into 5. I've been using this technique for years. It works for me.

[st200ol]

If using the Cellpro MPA connect the balance leads first, as it says in the instructions.

Then any flow of current between the packs as they are connected will be limited to approx 4A by the poly fuses.

[GtD]

I charge 6 x 6S batts in one go - all different makes and 3 different capacities. The voltages are never exactly the same and I've never had a problem. I had read somewhere not long ago that the flow from the 'high' battery to the 'low' one (assuming you only have 2 connected as an example) is not as fast as you might think...because as soon as you put the higher battery under load by effectively charging the lower voltage battery, the voltage of the one doing the charging drops a little (if you have telemetry you can see how much lower your flight pack voltage is when under load...you then land and the voltage reads a fair bit higher).

So even if you had one pack at 3.7v per cell and another at 3.9v per cell, the one at 3.9v would drop down as it started to charge the lower one - so the actual voltage difference wouldn't be as great.

I've also seen someone do a parallel charge on (I think) 3 batteries...1 of which was already fully charged! Not something I'd recommend at all - but the charge seemed to end up OK with all the batts balanced at 4.20v per cell.

having said all that...my knowledge of electricity stops at the 'flick the switch to make things work' level, so I'm only repeating what I've read - and if the person doing the writing seems to be fairly technical (wrt electronics) I tend to go with what they say.

Next time I charge I'll check each batt, find the highest and lowest and then connect the high first, then the low (just the charge lead) and leave it for about 5 secs then disconnect and see what each pack voltage is and see how long it takes them to equalise (i.e. will it really do it almost instantly??)

J