Most cost effective 12v highest a/h lithium battery setup.

[Deleted member 4366]

The configuration at 12v would be 4S6P. To change it to 44v for an ebike, you reconfigure it as you suggested to 12S2P. Instead of the five parallel power leads, you'd only need three (3 x 4S2P). Then you need a series harness to connect them up to 44v. Ideally, you need a parallel balance lead (2 into 1) for each pair, and to monitor them, three lipo alarms.

You have to be more careful with charging lipos when you use them in a series configuration. It's a good idea to have a different connector on the final output to what's on the individual packs so that you don't get them mixed up. It's very important that you disconnect the packs from series before connecting your charger otherwise something will get vapourised.

 

[eHomer]

Thanks Dave, I can understand the potential problems with them in series from what you say.

I did start thinking about maybe setting up keyed 8 way connectors with two different plugs as adapters prewired for the two configurations, but if it means three alarms then it's getting a bit Heath Robinson.

It's made it clearer how simple and fairly safe that the six in parallel will be though.

 

[Alan Quay]

Another thing has just occurred to me...

Would I be right in saying that if I sometimes connected the same six Hobbyking 14.8v 5a/h Lipo packs as two parallel banks of three in series, then I'd get a 44.4 volt 10a/h battery for my ebike ?

Yup, that's idea and plenty do it. I would be a lot more reluctant to charge them in the house un-attended though.

I heard of one guy who charges his lipo's in an outside loo, on a plastic seat. His theory is that if it all catches fire, it'll melt the lid and drop through!

 

[eHomer]

Yes Mike, I've noticed some of the precautions when I've googled R/C lipo charging on the Internet !

Quite a few people seem to use hollow concrete building blocks, a sort of scale model blast chamber...

 

[awol]

Yes Mike, I've noticed some of the precautions when I've googled R/C lipo charging on the Internet !

Quite a few people seem to use hollow concrete building blocks, a sort of scale model blast chamber...

I will be using a lipo safety bag, similar to these.
http://www.ebay.co.uk/itm/Lipo-Safe-Charging-Bag-Safety-Fireproof-Charging-Sack-/151300990888?pt=UK_ToysGames_RadioControlled_JN&hash=item233a3de7a8
http://www.ebay.co.uk/itm/Lipo-Guard-Battery-Fireproof-Bag-Uk-Seller-9x11-5-23X30CM-/221460661541?pt=UK_ToysGames_RadioControlled_JN&hash=item3390158525

 

[Deleted member 4366]

I used to use all that safety, stuff, but after so many charges, nothing caught fire. Now I don't bother.

 

[eHomer]

When I first charged my 48v 10ah lithium battery, I wrapped it loosely in a fire blanket.

 

[Deleted member 4366]

I've just tested my electric outboard with 4S lipos. Before I used 30aH of 3S 18650s. Just like an ebike, it runs 33% faster and more powerful.

Rather than use all those parallel connectors, I used a balance board to connect up to seven packs in parallel. All the power connectors are connected by two wide tracks on the back of the pcb. I took the pcb out and re-inforced those tracks by soldering two pieces of thick copper wire (from that flat ring main wire) on the tracks. It should handle about 40 to 50 amps now.

http://www.ebay.co.uk/itm/Parallel-Charging-Balance-Board-60A-for-Lipo-LiFe-Li-ion-IMAX-B6-Battery-Charger-/171296146246?pt=UK_ToysGames_RadioControlled_JN&hash=item27e20bc346

My outboard is bigger than yours so takes a much higher current.

In case you don't know, unless you've got one of the very expensive ones, the throttle works by bringing in resistors in series with the motor. Max throttle is straight through, but at any other setting there's a lot of heat wasted by the resistors so not very efficient. I wonder how hot they get at 16.8v?

 

[eHomer]

I'm confused again (nearly, maybe, I think....)

I think you're saying you use that balance board to connect the output leads of the six 14.4v packs, rather than the individual two way adapters ?

The link describes it as for charging though ?

I thought that harness with the miniature sockets was for charging ?

Interesting what you've said about the resistors in those outboards to reduce the speed. I've got two electric outboards, the Minn Kota I think is some sort of electronic pulsing, but the small one that I use on the kayak is cheap and cheerful, so it probably is simply controlled with resistors, as you say.

It's very small, and light, and pushes the kayak at between 2 to 3.5 mph, in complete silence.

 

[Deleted member 4366]

Yes. The board is used for charging, but as long as your discharge voltage is below 22.2v(6S), you can use it for discharging as well. You connect the power leads and the balance leads. It saves a lot of messing about - nothing to connect or disconnect when charging except your charger.

 

[eHomer]

So would this be the configuration using the parallel board ?

 

[Deleted member 4366]

You don't need the parallel balance lead because you plug all the balance leads into the board, which puts them in parallel.

 

[eHomer]

Ah, I see.

I'm guilty of not really understanding how the board works

I'm trying to guess the connections and their function.
My thinking so far:

• The row of six red double spade plugs down the middle link the positives onto the output bus, and the heavy bottom red connector is the output lead ? or is it the one coming out of the end ?
  
• The six sets (3 each side) of small white balance connectors take the balance lead from each lipo pack for charging, from the dedicated "IMAX B6 digital rc balance charger", who's white multi way balance lead plugs into the end ?

I think I'm probably talking rubbish here, but I'll leave what I've said so far, so you can see my working out !

Is there anywhere on the web where some radio control enthusiast has constructed an idiot's guide to combining packs, chargers, balance leads etc.. ? I thought I nearly had it sussed, but I'm back to asking naive questions again...

 

[Deleted member 4366]

It's not as complicated as it looks. All the power connectors are joined in parallel to the charging lead, and all the balance connectors are joined in parallel, so when you connect six 4S packs, they become one 4S pack of six times the capacity. You then have one spare power lead for charging/discharging and one spare balance connector for balancing/monitoring. As I said before, discharging currents are higher than what the boards is designed for, so you need to beef up the two tracks that join the power connectors in the middle of the board.

 

[eHomer]

So there are no components or processing in it ?

So, as you originally said, it's a neater way of connecting the six packs in parallel, rather than the daisy chain charging/balance connector lead, and the "cascading" two to one output adapters ?

So all of the leads could be left permanently plugged in ?, and the whole pack of six batteries, balance board, and lipo alarm could be fitted into a weatherproof container with just the output pair and one charge/balance connector flying lead protruding from the box ?

That particular balance board specifically mentions the "IMAX B6 digital rc balance charger", but could the Hobbyking "The Turnigy Accucel 6 Balance Charger" be used instead ?

 

[Deleted member 4366]

You've got it now.

You can use any charger with it. They all have the same 6S balance connector. You'll have to put on matching connectors on the charger and motor if you want to leave it connected,

After beefing up those two main tracks, you connect up to 6 batteries with their power leads to the power connectors down the middle and their balance leads to the board. You can leave them like that permanently in a box with just the main power lead and balance ribbon cable coming out. The ribbon cable will be suppied with the charger.

Charging: Connect charger power lead to board power lead. Connect charger balance lead to board main balance connector (on edge)

Discharging: Connect board's main power lead to motor. Connect lipo alarm to main balance connector (on edge).

You need to think about the waterproofing of the alarm, especially if you go on salt water.

 

[eHomer]

......Charging: Connect charger power lead to board power lead. Connect charger balance lead to board main balance connector (on edge) .

So the balance lead is used by the charger to monitor each of the 4 cells in each pack, and shuts the charging down if one goes short or dis ?
If the balance connectors are just paralleled across to each pack as a direct connection, how can the single charger monitor lead know that one of the cells in one of the packs has gone short or dis ?

......Discharging: Connect board's main power lead to motor. Connect lipo alarm to main balance connector (on edge).

aha, I saw the multi pin connector at the bottom of the lipo alarm and wondered why it wasn't just a single pair connection. I'd assumed it was simply going to monitor the output voltage as a total, and not let it drop below VLC for the 4S. So now I understand that it's monitoring the voltage at each connection of the 4S ?

Again though, how could it do that if those connections are paralleled across the six battery banks ?

(If you ever get cheesed off with my possibly strange questions, let me know (gently)

 

[Deleted member 4366]

Let's call it "channels". Each channel is monitored by the charger and the lipo alarm. All the cells on the same channel will be the same voltage because they're in parallel. If one cell was duff, it would be held up by the others. For that reason, it's a good idea to cycle the packs individually first to check for any abnormalities. They rarely fail afterwards, but I had two duff packs out of eleven, where one or more cells went down more quickly than the others.

 

[drsolly]

Yes and yes. I just bought four more of those 5AH 4s hardcase batteries for £15 each. That includes vat, and they're coming from the UK, so no customs. I've looked and looked, and I can't find a source of Lipos that comes anywhere near Hobbyking prices. Although their customer service is poor. And once they sent me someone else's order instead of mine, and it took several weeks to sort it out.

One thing I've found about these batteries. On a few of them, I've had to tape the leads to the case (duct tape) to stop the lead moving, which causes intermittent connections.

I slightly disagree about the number of cell checkers you want. Even if you're running the six batteries in parallel, I'd still use six cell checkers. That's because, even though the batteries are in parallel, the cells aren't. So it's possible for a cell to get below the voltage you want as a minimum, even through the cell that you're checking (in a different battery) is above.

I set my voltage minimums to 3.2v.

The last lot of cell checkers I bought were £1.22 each (on ebay), so it's not a big expense!

You should also get enough balance plug savers; if you're going to be plugging and unplugging the balance leads, this will protect them from being pulled apart.

http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idproduct=41116

You might also want 4s extensions. http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idproduct=26096
But you can get them a few pence cheaper on Ebay

And a hobbyking tip. If you're newish to Hobbyking, go to the page with the batteries you want, and just leave it there for a bit (a few minutes). There will be a pop-up after a while that offers you the sale at a slightly lower price (5-8%).

 

[Deleted member 4366]

I slightly disagree about the number of cell checkers you want. Even if you're running the six batteries in parallel, I'd still use six cell checkers. That's because, even though the batteries are in parallel, the cells aren't. So it's possible for a cell to get below the voltage you want as a minimum, even through the cell that you're checking (in a different battery) is above.

You should also get enough balance plug savers; if you're going to be plugging and unplugging the balance leads, this will protect them from being pulled apart.

All the cell 1s are connected in parallel, same for cells 2, 3 and 4, so they cannot be at a different voltage. Therefore only one alarm is needed.

There's no need to unplug anything on the packs. Once connected they stay connected for both charging and discharging, so no need for those connector protectors.

It's a different situation if you use those packs for an ebike battery. For that, you can't use the balance board except for charging, in which case they'd be a useful accessory.