Charger for 12s lipo

[ebiker]

I'm thinking about getting a 12S lipo pack for my 48V setup and I don't know how to charge that pack the best way?
I have no experience with lipo batteries yet. Do I need to balance the pack? Or do I need a charger with internal balancer?
Is a 12s lipo to small for a 48V setup? Do I need 14S?
Does somebody have a suggestion for a (not too expensive) charger?
Sorry for so many questions, but I never dealt with lipo so far.

 

[GGoodrum]

I'm thinking about getting a 12S lipo pack for my 48V setup and I don't know how to charge that pack the best way?
I have no experience with lipo batteries yet. Do I need to balance the pack? Or do I need a charger with internal balancer?
Is a 12s lipo to small for a 48V setup? Do I need 14S?
Does somebody have a suggestion for a (not too expensive) charger?
Sorry for so many questions, but I never dealt with lipo so far.

First of all, you need to read this thread if you don't already have lots of experience with LiPo packs: viewtopic.php?f=14&t=9170. If you were trying to match setups, so that you could use an existing 48V SLA charger, which typically put out about 58-59V, you would use a 14s LiPo configuration. The problem is that this doesn't provide you with cell-level monitoring during the charge process, so if there is a problem, you could end up with exploding cells and catestrophic fires. If you are going to try and use LiPos, you really need to use LiPo-specific chargers with built-in balancers and cell-level monitoring. On the 1st page of the thread in the link I provided, there's a couple of good 6s charger/balancer units that Luke references from Hobby City (based in Hong Kong...), that are also reasonably priced. The largest pack configuration that you can get these days seems to be 6s. 5Ah capacities are about as big as they offer, so to get 10Ah, you would use two 6s/5Ah packs in parallel. You can use two sets of these in series to get 12s/10Ah. You can either charge these one at a time, with a single 6s charger/balancer, or get two chargers. You can connect 2, or more, in parallel for charging, but only if you connect the balance plugs from each pack in parallel as well.

-- Gary

 

[recumbent]

Lipo batteries are certainly the most compact power source for ebikes, that's for sure, but the charging issue is a deterrent, combined with the safety hazzard, Which is minimal if correct charger is used.

I think the balancing boards that Gary & Fetcher designed can be wired for lipo, but the safety issue and potential liability, hence the lack of info, well... maybe if you PM the right person they might tell.

 

[johnrobholmes]

The Hyperion DUO, or two 6s chargers used together is probably the easiest way to go. They have built in balancers.

 

[GGoodrum]

With LiPos, you really need to use a balancing charger designed to monitor each cell during the charge process to make sure no one cell goes over 4.3V, period. If it detects a cell that does, it will immediately shut down the charger, and indicate an error. The BMS board that Richard and I did does not have this capability, so while you can change a couple of resistor values, to get the board to work with LiPo packs, there is no absolute protection against a cell getting overcharged, which for Lithium-Cobolt - based chemistries, is disasterous.

-- Gary

 

[ebiker]

Thank you for your advice so far. Just one more stupid question
For charging the lipos, do I just connect the balancer plug to the charger?

 

[liveforphysics]

If you get a charger that charges through the balance taps, then yes, you justs plug in the little JST balance plugs, and the charger will run until all the cells are charged and at the same voltage. You don't even need other charge leads for this type of charger. These are the most friendly of all battery chargers, but they often charge at 1-2amps max per cell, so a big pack may take many hours to charge, but you really can't screw things up, and it's totally simple. No settings or anything at all to mess up. Just plug in the balance connector and walk away, unplug it when all the lights turn from red to green.

If you get the higher current types that can charge a big pack quickly, then you plug in the balance taps, and it asks you were you want the cut-off voltage and things. It will resistively balance any cells that are out of wack during charging, and if anything is too far out of wack, it has to cut the charge current back to the level that it can balance at (typically around 300-1000mA). For normal charging though, packs are close enough in balance that they can hold things in balance as they rapidly charge the pack with just the small amount of resistive balancing. These chargers need a connection to the power taps of the battery, as well as the balance leads plugged into them. They also need to have some basic settings programmed into them to ensure they will charge your specific battery how you want it to be charged.

 

[stew007]

You need to use a proper balance charger designed for Lipos, and it is best to use a good quality one like the two mentioned below. (note they can also balance charge Lifep04/a124 etc if you ever decide to switch over. The software is also upgradable so they are fairly future proof.

http://shop.graupner.de/webuerp/servlet/AI?ARTN=6444.GB

http://robotbirds.com/catalog/product_info.php?cPath=9_94&products_id=3264

The graupner can do 14 cells (2 x 7s packs)

The hyperion duo can do 12 cells (2 x 6s packs)

Both can give out nearly 400 watts of charging power.

http://cgi.ebay.co.uk/400W-24V-16-7A-Switching-Power-Supply_W0QQitemZ310132582935QQcmdZViewItemQQptZUK_CCTV?hash=item310132582935&_trksid=p3286.c0.m14&_trkparms=72%3A1683|66%3A2|65%3A12|39%3A1|240%3A1318

cheap mains power supply for the DUO, works a treat.

I would avoid the cheaper types that only charge through the balance leads, they can only charge at very low currents due too the balance wires being so thin, so your e-bike battery would take forever to charge. Its really not very practical.

You can also charge your lipos in parallel, so long as you make a parallel balancing lead, and parallel power lead.