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.

[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.

[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