Charging larger LiPo packs

SLT32 · May 28, 2015

I have some questions about charging LiPo batteries. Last year I built a 36 volt tadpole trike for my wife (twice a week usage) and a 48 V front wheel gear motor bike (daily commuter). Both using a 350 W motor. I have been using SLA batteries for convenience and trial. 36 V SLA 10 amp hour battery gets about 20 miles. 48 V 8 amp hour battery gets about 15 miles. 1000+ total miles.
I have already purchased (3) 10S 5800 mA batteries for my wife’s trike. If I split the 10S connector to two 5S connectors, can I use two 5-7S chargers to charge it? If I use the (2) 6S chargers at the same time, it seems like it would need to use a 24 V system. Most likely 2 automotive batteries in series connecting the chargers in series also. Would this work? This would give me redundancy of chargers if one would fail during a trip.
I have heard about charging Lipos in series. Charging the 10S pack to 42 V and occasionally rebalancing the cells. Is this safe and reliable?
How long can you leave a Lipo fully charged before causing a problem? I’m now use to charging my SLA batteries after each ride. But sometimes they can sit for a week before being used again. I do understand differences between a Li-ion, Lifepo and Lipo batteries and the safety risks involved. I have used smaller Lipos for RCs 3S-4S.
This forum is a great source of knowledge, with good advice. What a difference then all the forums where people talk and know jack.

dnmun · May 28, 2015

yes, lead acid needs to be recharged right away and then a little sustaining to compensate for self discharge.

but you can leave the lithium uncharged until you need it and that extends the life a lot more than just charging part way up but charging it up and leaving it charged all the time.

about the question of the 5S split. do you intend to make a 15S pack 15S2P?

that will give you 63V and you can run your 36V contoller up to that voltage with no risk.

i recommend a 16S D167 lipo BMS and you can use the first 15 channels. or go buy 3 more of the 6S packs and make a 16S3P pack and use the D166.

or order one more 10S and 4 of the 6S and make two separate 16S2P packs with two BMSs you get from bestechpower.

motomech · May 28, 2015

SLT32 said:
I have some questions about charging LiPo batteries. Last year I built a 36 volt tadpole trike for my wife (twice a week usage) and a 48 V front wheel gear motor bike (daily commuter). Both using a 350 W motor. I have been using SLA batteries for convenience and trial. 36 V SLA 10 amp hour battery gets about 20 miles. 48 V 8 amp hour battery gets about 15 miles. 1000+ total miles.
I have already purchased (3) 10S 5800 mA batteries for my wife’s trike. If I split the 10S connector to two 5S connectors, can I use two 5-7S chargers to charge it? If I use the (2) 6S chargers at the same time, it seems like it would need to use a 24 V system. Most likely 2 automotive batteries in series connecting the chargers in series also. Would this work? This would give me redundancy of chargers if one would fail during a trip.
I have heard about charging Lipos in series. Charging the 10S pack to 42 V and occasionally rebalancing the cells. Is this safe and reliable?
How long can you leave a Lipo fully charged before causing a problem? I’m now use to charging my SLA batteries after each ride. But sometimes they can sit for a week before being used again. I do understand differences between a Li-ion, Lifepo and Lipo batteries and the safety risks involved. I have used smaller Lipos for RCs 3S-4S.
This forum is a great source of knowledge, with good advice. What a difference then all the forums where people talk and know jack.

...Charging the 10S pack to 42 V and occasionally rebalancing the cells. Is this safe and reliable?

It's the only safe way for you to charge those bricks.
You need a quality 10S or higher balance charger and many of us here like the 12S capable Thunder 1220 w/ an inexpensive sever power supply..
If my ride has dis-charged the Lipo below 3.75V/cell, I will immediately charge up to a "storage" Voltage of 3.85V/cell and top-charge to rest of the way to 4.12V/cell right before I leave.

dogman dan · May 29, 2015

Re leaving it charged. The more time it's sitting there fully charged, the worse it is. But somewhere there is a practical middle ground. You want it more or less ready to go when you want to ride.

If you charge it fully, and don't ride after all, take it out for a 1 mile ride instead. Then at least it's not quite all the way charged while it sits. Ideally, leave it uncharged after a ride, till at least the night before your next use.
Store it cool as possible, not in a hot garage in summer.

Re safety, never charge it or store it in a place you wouldn't build a fire.

SLT32 · Jun 1, 2015

Thank you all for your advice. The idea of charging the 10S with 2 6S chargers is a NO GO. I would need to open the packs and add a larger gauge wire between cells 5 and 6 to handle the high current of charging at 6A. The balance wire for that cell is to small. There was a little misunderstand about the way the DC chargers step up the charge voltages. With the smaller packs the Input voltage was near the Charge voltage. I thought that charger rotated between cells while charging. This was explained to me be false. The charger steps up the voltage and current to the main connectors with balancers only bleeding off higher voltage cells. If this explanation by another RCer is wrong, please let me know. I will be getting a Turnigy Reaktor 30A 1000W Balance Charger. http://www.hobbyking.com/hobbyking/...A_1000W_Balance_Charger.html?strSearch=30a 10 The good news to that I can limit my 36v/48v SLA charger to 24V and use it as a power supply. Also decided to buy (2) 3S 5800mA packs to play my 48v bike.

docnjoj · Jun 6, 2015

Not sure what country you are in but in the US Hobbypartz sells the Thunder 1220 for 95 USD. It is a true 12S Lipo charger.
otherDoc

Charging larger LiPo packs

SLT32

10 µW

dnmun

1 PW

motomech

10 MW

dogman dan

1 PW

SLT32

10 µW

docnjoj

1 GW

Similar threads