Charging regimes

[Don Fry]

I am a petrol head.

I use electric systems, and slowly, as they break/wear out, smaller IC airframes are replaced with electric power systems. Nowadays, the cusp is about 800 watts. In this area, the decision process is for another discussion
The trouble is, I have little idea as to what a charger does.

Knowledge base. Go fly. Charge battery at 1C. Don’t kick it in flight, land before it dies, go home, return to storage. Store at wine cellar temperatures. 10-15°C. 

What are the pro/cons of Fast Charge, Charge? I never use them.

 

 

[Simon Chaddock]

Don

A 1C charge rate is considered safe as it restricts heat build up during the charge which LiPo don't like as it shortens their life. A modest heat build up during discharge is less of a problem but excessive heat will shorten their life. 

Some very low resistance batteries (60C+ max discharge rate) can be charged at up to 5C but it is worth noting that the internal resistance of all LiPo increases with use so at some point in its life a 5c charge may become an additional risk.

A regular balance charge to ensure all the cells are bought up to exactly the same voltage (4.20V). It takes a bit longer to do but it will improve the LiPo life.

[Paul De Tourtoulon]

I only charge mine on 1C, small 1300/2500 mah lipo for epp stuff with an alarm (photo ) to make sure that I don't kill the battery, balancing

 never seems to be satisfactory so I finish off using the balance plug and charging the cells one by one,,

[Frank Skilbeck]

Don your regime looks good to me, especially if you are balance charging. The only pro to a Lipo fast charge is a shorter charge time, but you run the risk of increased heat build-up and battery degradation.

 

If you have a battery which the charger is struggling to get the cells in balance, try charging it at a lower charge rate, say 0.3 amps. The way the balancing works on charger is by diverting a small amount of current (typically 100 to 200 ma) around the high cells while charging, if you are charging at a high rate it doesn't give time for the low cells to catch up before the high cells are fully charged.

[Brian Cooper]

Fly, recharge. . . Fly, recharge. . Repeat often until the lipos go beyond their useful life.

 

Dispose of moody lipos and buy new ones. . . Repeat as above. 

 

Some lipos last longer than others. . Such is life.

 

Personally, my limit on electric flight is 4s. . After that, it just gets stupidly expensive. 

.

[Don Fry]

OK, I understand balancing, and I use balance charging. I, like Brian, stop at 4s, for much the same reasoning.
I also have, (in addition to standard 4 button chargers), a simple charger which is a multiple 1s charger, plug the balance lead in and it charges each cell individually. Useful if the battery has acquired a low volts cell, but I find a low volt cell is a symptom of impending failure, or in the past a fault on the 4 button charger.

But what is the charging and fast charge functions? What do they do?

[Peter Jenkins]

The other thing to do Don, if your charger will allow it, is to charge to 95% rather than 100%.  It is both quicker and extends the life of the LiPo all other things being equal.  Depending on your charger, "Fast Charge" may mean only charging to 95%.  Charging might mean charging to 100%.  If you use a voltage checker once your LiPos are off charge you should be able to see the difference between 100% and 95% charge.

 

If you have to resort to balancing the LiPo once it is off charger than consider buying a better charger that will sort out cell imbalance until one cell starts to go duff of course.  Since chargers last a good deal longer than LiPos, having a good balancing charger is worth it if you can extend your LiPo life.

 

As Brian Cooper says, some LiPos last longer than others.  I've got a bog standard Turnigy Blue pack (2 x 5S that I use in 10S configuration for flying) and that pack has reached 160 cycles and is just beginning to not perform in the schedule I fly.  These packs are charged to 95% capacity and end at 3.6 -3.7 V per cell after flight - shows as 14% remaining on my Voltage checker.  When I charge them, they generally take around 3200 - 3500 mAh which by my calculation means that I've used between 70% - 74% of capacity.   That gives 8 mins of flying a quite testing competition aerobatic schedule.

[MattyB]

6 hours ago, Don Fry said:

But what is the charging and fast charge functions? What do they do?

 

Peter has had a reasonable stab above, but tbh it is pretty hard to answer that question given you haven't told us what charger you have... 😉

Edited October 27, 2022 by MattyB

[MattyB]

17 hours ago, Simon Chaddock said:

Don

A 1C charge rate is considered safe as it restricts heat build up during the charge which LiPo don't like as it shortens their life. A modest heat build up during discharge is less of a problem but excessive heat will shorten their life. 

Some very low resistance batteries (60C+ max discharge rate) can be charged at up to 5C but it is worth noting that the internal resistance of all LiPo increases with use so at some point in its life a 5c charge may become an additional risk.

A regular balance charge to ensure all the cells are bought up to exactly the same voltage (4.20V). It takes a bit longer to do but it will improve the LiPo life.

 

I agree with most of this post, but I've seen little meaningful heat build up from charging at 2C, so that is my de-facto charge rate for all but the smallest lipos. I also always balance charge because it is far safer - the charger is monitoring all the cells and will pickup any impending overcharge before it happens.

 

Yes, I do parallel charge multiple packs which means the charger does not know the actual voltage of every cell in every pack (as a result some will tell you is the work of satan), but I always check every pack first individually when I put them into storage and again before I next charge, This means I will never parallel up packs that aren't well matched (I don't put them on together unless they are within 0.05V of each other). TBF though, now the latest 150-200W digital chargers are so cheap the need to parallel charge is going away; if I started again I'd go that route (though still with the awesome converted server PSU).

Edited October 27, 2022 by MattyB

[Don Fry]

Right, fair enough. I will dig out some instructions for the chargers.