Charger behaviour differences

[Big G]

Charger A I'd had for a few years. It was a advanced charger with a lot of features mainly to do with NiMH's, cycling multiple times and motor run-in, etc. It could charge, but not balance lipo.

Charger B is a new purchase I bought because it would be used on the mains or 12v without the separate adapter needed for charger A. Also it had a built in balancer.

Over my 2 1/2 years of racing I have owned 14 packs of lipo. I've had 5 or 6 of my packs start to bulge in their casing. 1 to the point I could fit it into the durango because it touched the driveshaft and also this 4200mah pack wouldn't recharge more than 3000mah after dumping and hitting the lipo cut off during a race.

Last night I was charging my packs with Charger B and I noticed it's behaviour was a lot different to Charger A's behaviour charging the same pack. Charger A used a CC-CV charging method. It would slowly build up the current over 10-15 secs to 4.5A (4500mah pack) and hold until 8.4V and then slowly the current would drop to 1.0A before saying done. The drop down took probably 10mins give or take.

Charger B will build it's current to 4.5A within 3 seconds and once the voltage has hit 8.4v it will drop to 0A and say done in probably 30 secs.

Had charger A been charging lipo differently (wrongly?) and could possibly be linked to my bulging lipo? It would put a fair few mah into the lipo after hitting 8.4v...

The worst pack I had bulge I bought new and used for 4 or so months when they had a very very slight bulge. I then sold them to my dad who used them for a further 4 months and now they have broken out of their hard case and almost doubled in size... This lipo was barely 8 months old with only 1 race a week on average.

All lipo have been used in buggies on mostly smooth tracks indoors and haven't been off loads of massive jumps. Regularly monitored and balanced when needed.

[Dazzler]

Charger 'A' seems to be doing things right to me, exactly how all mine do / have done and follows the logic of the charge cycle. Charger 'B' doesn't seem to have a soft start to current build up like 'A', and I'm surprised it ends the charge so quickly. Charger 'B' would be suspect in my mind, albeit, maybe something that can be changed in its settings. (As for selling your Dad your knackered old batteries...... )

To add, you're best off always Balancing, as over or undercharging one of the cells could be causing your issue. It will also take longer when you do eventually balance them than if you do it every time.

[RogerM]

It sounds like charger A is running true CC-CV charge mode which I am told is correct for lipo .... certainly what my charger does.

I've not had any swelling on the 2 packs I've used for 18 months but they don't balance any more ... ok they do but take about 2 hours to do so after reaching 8.4V so can no longer balance charge at the track. I used to balance every charge until I couldn't anymore.

[Big G]

Forgot to say. Charger B is 2 weeks old can't be responsible for bulging batteries

Daz I sold Dad batteries I bought new 4 months earlier

My worry was Charger A was holding onto the charger for too long

[CrashBangWallop]

I would have to second dazzler on the selling of bulged lipo's to someone else. they are really only fit for disposing of.

If you are able to balance charge, now you have the option i would definately do this. But discharge the pack on the new charger first before balance charging, this may make the new charger take longer to recharge the pack but they will be properly balanced at the end of the charge cycle.

The 'bulk' of the charging should take the packs up to about 95 % of their full capacity and the final 5% should take much longer to top off and balance the pack. Most up to date chargers will have a 'dual' type display for each cell so you can see whats happening i.e both voltages of each lipo in the pack should be displayed.

Sounds like your old charger was a much more charger for Nimh with a Lipo charge function added on. This was around when lipo's were in their infancy with RC, nothing wrong with it but just not bang up to date. Only thing I found with the Much More chargers is that they were VERY sensitive to fluctuations in input voltage and or something else taking current from the power supply.

[Big G]

I now have packs I bought in December which are starting to show a tiny bulge. I can't be replacing packs after 4 months of use at £80 a go!

Daz they were hardly knackered old batteries!

[RogerM]

G', what brand of charger are you using?

If your going to replace anything I'd say change the charger for one of the respected ones.

[Dazzler]

I would also check out your lipo cut off voltage on your speed controller if it's adjustable. Making sure it's not too low.

[Big G]

lipo cut off has been at 3v forever. I rarely hit it though only now and then.

ps. either of you 2 racing tonight?

[Dazzler]

I'm planning on it

I have run my cut-off at 3.4v / cell without any issues, the higher it is, the less risk you take, especially if you are not balancing your cells each charge. Try upping your setting.

[Jamie.T]

This is an interesting thread actually as ive noticed differences between both my chargers.

Ive noticed one charger reading the cell voltages wrongly and effectively over-charging my lipo. Sometimes i measure with a battery doctor or multimeter and the cell voltages displayed are often lower than the true voltage.

My newer charger (iCharger 206) is spot on and once it hits the 4.2v per cell for a brief moment, it cuts the charge off and beeps to say its done.

The older charger (JP lipro plus 5) keeps on charging until the cells also read 4.2v, but the true reading according to my multimeter and battery doctor is more like 4.22-4.23v which means the pack is being overcharged.

Just like Big G, some of my older lipos which were used with the old charger are starting to swell.

It makes you wonder what is a true "good charger" in terms of keeping your lipo tip top.

[Col]

I bought one of these 4 years ago.


I bought 1 pack of these 18 months ago


This is the only lipo I've ever owned, gets used 2/3 times a month all night long and has no swelling or performance issues. It has also NEVER been near cut-off voltage.

[Chequered Flag Racing]

@ Big G

If you know someone with a Pro-Trak charger and the sofware it's possible for the Pro-Trak to monitor each charger as they charge and do a screen capture with SnagIt or similar so you can do a video

I'd do it for you but there's 228 miles between us

[Dazzler]

Glenn, how are you connecting and monitoring with that? I'd be interested in knowing as I have all the necessary kit!

[Chequered Flag Racing]

Originally Posted by Dazzler

Glenn, how are you connecting and monitoring with that? I'd be interested in knowing as I have all the necessary kit!

your Pro-Trak needs to have the monitor option in the software though

similar to this



and

[Dazzler]

Thanks, I'll have myself a look at that when I've got a spare hour or so.!

[rondoolaa]

i'd also say charger A seems fine,

my chargers dont have ballancing ports so i have seperate ballancers, when i charge any battery nimh or lipo i charge at 1c and it takes about 10-12 seconds to get to the optimum (1c) charging level,
as soon as it reaches 8.4v the amp output starts to decline until it gets to 0.10amp and then beeps and charge is complete,

same as your A charger by the sounds of it,

you are charging at 1c arnt you...

[Big G]

yes 1C.

Glenn 228 miles even on sunday?

I don't have charger A anymore

[bodgit]

[QUOTE=Big G;498727]lipo cut off has been at 3v forever. I rarely hit it though only now and then.


3v is the absolute limit maybe hitting it now and again maybe doing the damage. reset it to 3.1per cell

[Big G]

Spoke with Daz last night. I think what's happened is the cells aren't 100% balanced and with 3v cut off it may have been 2.9/3.1 or something like that.

Will adjust teh cut off