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

[drsolly]

I set my low voltage alarm at 3.2, I agree that 3.0 is a bit low. I love your lunchbox package. If you don't want all your batteries in one basket, how about making up multiple baskets, and plug in number two when number one is depleted?

Charging at 0.5A is really slow. Those lipos can easily take 5 amps. Because they are 5AH batteries, 1C charging means 5 amps.

I've seen the videos of lipo exploding, but I think you have to really abuse them badly to make that happen. I see a lipo as about as dangerous as a can of petrol. I do keep a spare can in the car, but I wouldn't have a naked flame nearby while pouring it. Like a can of petrol, you have to treat lipos with a bit of respect.

Your charger will beep and stop charging when it reaches 4.20 on all cells.

When you got the batteries they were 3.85 volts, because for long term storage, it's best not to have lipos fully charged. So Hobbyking store them at 3.8 or so, and ship them that way also.

 

[Deleted member 4366]

I reckon that in your test you used about 1/3 of their capacity. Lipos go down more or less linearly from 4.2v to 3.6v, then they accelerate rapidly downwards, so you had about .25v instead of .6v. That means about 3 hours run time. Trust me. There's not a lot left after 3.6v. Set your alarm higher.

1 amp charge rate is OK for one pack. As you have six in parallel, you can go to 6 amps or even 10 or more.

 

[eHomer]

I confess it did cross my mind to divide up the pack, but I guess even three would give me a big melt down scenario aboard a plastic canoe !

I hear what you're both saying about charging rates, I'd screwed it right down to half an amp for the first full charge out of timidity, but yes, even the max of 5 amps is well within the safe rating of the six packs in parallel, giving them less than an amp each.

Yes, I'm guilty of frightening myself with the youtube videos of the Lipos exploding. As you say, when charged and discharged at the safe voltages and currents with BMS's or balance leads, and secured from physical damage, the danger is really minimal. Most of the youtube vids show them being intentionally "set off".

Thanks for the reassuring comments, I'll stay with it and construct a fire resistant cubby hole in my garage to enable even safer charging of all my lithium batteries.

Wow, if I got 1 hour of max speed out of my outboard with only 1/3 of a charge, then my little lightweight lunchbox is going to be very useful with the canoe motor.

I'll do a full charge, then try another tank test run with low voltage beeper set at 3.6 and let you know how long it lasted.

 

[Geebee]

You could always go with a Lipo charging bag, they will smoke but every test I have read of says they will contain the fire.
I store mine in the spare room now days in a Lipo bag, in an an old electric frypan with lid
On the bike they are usually just put in the pannier bag inside a plastic container.

 

[eHomer]

I had a look at those online Geebee, but I couldn't find one big enough to take my plastic lunchbox container.

That's why I thought maybe my fire blanket sewn into a sack shape would maybe do, it's quite heavy fabric ?

I've got it set up in the garden now, trying to givve a full cahrge for the fisrt time. I set the charger to Lipo, 4S, 6 amps, and it starts ok, but then keeps stopping with the error message "Vol Select Error", which the instructions say is "The voltage of the lithium battery pack was selected incorrectly. Verify the voltage of the battery pack carefully".

I'm confused though, each pack is definitely 4S, paralleled up to six parallel.

The charging voltage for 4S Lipo seems to be fixed on the charger at 14.8 volts though, 3.7v per cell. I thought it should be 4.2 volts ?

It's a Turnigy Accucell-6 bought from Hobbyking with the battery packs.

 

[Geebee]

Is it set to Lipo battery type?

 

[Deleted member 4366]

The problem is your supply to the charger. What are you using to supply it? If the supply can give sufficient current like a PC power supply, they sag a bit at 6 amps. There may be a setting in your lipo charger for minimum supply voltage. If so, you can reduce it to 10v, which should eliminate the error.

 

[eHomer]

Yes it's set to Lipo Geebee.

I think you've nailed it again Dave. Rather than run my mains extension lead into the garden, I was using an 85amp leisure battery.

I'll try it with my 12v DC power supply plugged into the mains.

 

[eHomer]

It's coming up with the same error again "Vol Select Error".

I've now got it powered by a 12v regulated bench supply that can supply 3 amps continuous, so I set the output current on the Turnigy to 3 amps as well.

It was charging away for about 10 minutes and has now come up with that same error again and stopped.

When I unplug the charger and plug in the lipo alarm, it shows 3.72 volts on each of the cells and 14.8v total.

I'm wondering if my only recourse now is to unplug all my paralleling leads and try charging each 5amp pack individually ?

 

[Geebee]

If the PSU is rated for 3 amps you will have to lower the output as the voltage is stepping up to 16.8v at full charge which means the amount of amps in needs to be higher than the output.
For example if you have 12v input and were charging a 24v battery you would need twice the amps in as out, ie. 24v at 1 amp equals 24w 12v at 2 amps equals 24w

Try a quick test at 1.5 amps or maybe 2 amps max. output.

 

[Deleted member 4366]

Chuck that 3 amp power supply and make one out of an old PC supply:

Cut off the connectors;
Join all the yellows for the 12v;
Join all the blacks except one for 0v;
Join the orange to a grey;
Join the green to the remaining black. You can make this the on/off switch;

That's it - a 300w power supply that can give 10 amps. Cost: £1 from a car boot sale or zero if you have an old PC.

It's very satisfying when you recycle something like that too. You get a real sense of achievement.

If you want to be really clever, you can use the reds for a 5v supply/charger, and the oranges for 3.3v

 

[eHomer]

Yes, I'm sure you're both absolutely right, my crappy little ancient 3 amp psu is getting hotter and hotter, even with the charging restricted to 3 amps.

As you say Geebee. I was forgetting the jump in power from the increase in voltage at the output.

The photos show the latest tests, with the battery packs lifted out of the lunchbox to disconnect the paralleling, and i'm now charging just one pack, and it's working fine, with 3 amps in already and the cell voltages up over 4v now.

You don't know the half of it Dave, I've got about four old PC PSU's in the loft, and I was too damned lazy/impatient to wire them up to the charger's input lead, as you suggest.

I'll get one out now and modify it, then try parallel charging the other five packs, before I reconnect my sandwich pack.

Maybe my Noob questions and silly mistakes will save anyone else reading it from overlooking the basic ingredients !

 

[eHomer]

Blast !!

I really thought it was soled there.

I've dug out one of my old PC power supplies, one rated at 20 amps.

I've cut the leads and joined the colours as Dave suggested, and it's pushing out 11.7 volts.

I connected the five uncharged packs via the balance leads and set it going at the maximum, 6 amps.

It put in about half an amp, the beeped and stopped with the error code "Vol select error" again. I then tried not connecting the balance leads (as I'd read somewhere on another forum about the Turnigy), but the same result again.

I then substituted the 6 way breakout balance lead for the 6 way balance board, and the same result again.

I'm now charging another of the packs individually again, and it's still charging ok.

So, the charger keeps giving the error whenever the battery packs are paralleled.

The only differences I can think of are the 30 amp fuses inline with each cell when they're in parallel, and the different balance socket used on the charger. With individual charging, the pack's 4s plug goes in the charger's 4s socket, but when parallel charging, the balance lead's 6s plug goes in the 6s socket in the charger.

In both cases though, the charger shows the correct individual cell voltages, and the battery is correctly identified as 4s.

 

[Deleted member 4366]

As I said before, It happens when your supply voltage goes below the minimum allowed. You can normally set it to a lower value somewhere. Have a look through all the menus. For a PC power supply, you need to set it to 10v

 

[Deleted member 4366]

I just checked the manual. It's the last screen in the menu. You can decrease it.

http://www.hobbyking.com/hobbyking/store/uploads/ACCUCEL_manual(2).pdf

 

[eHomer]

I hadn't noticed that setting but I've just checked it, and I'm afraid it was already on 10v, the lowest it would go.

I'd thought about the balance lead using a 6s plug, so I checked out the pins on the various balance sockets on the charger. Unlike the balance board and breakout lead, the respective pins were isolated from each other, so I thought that might have been triggering the error. So I moved things around to be able to connect the 4s plug on the 6 way breakout cable into the 4s socket of the charger, but the fault popped up again.

So I'm still left with it only being able to charge one pack at a time. I now have two charged up with 4.15 to 4.2 volts per cell, and four partly charged at around 3.7 volts per cell.

I'm wondering if the charger is just not capable of charging packs in parallel, either via breakout cable or balance board ?

 

[awol]

I hadn't noticed that setting but I've just checked it, and I'm afraid it was already on 10v, the lowest it would go.

I'd thought about the balance lead using a 6s plug, so I checked out the pins on the various balance sockets on the charger. Unlike the balance board and breakout lead, the respective pins were isolated from each other, so I thought that might have been triggering the error. So I moved things around to be able to connect the 4s plug on the 6 way breakout cable into the 4s socket of the charger, but the fault popped up again.

So I'm still left with it only being able to charge one pack at a time. I now have two charged up with 4.15 to 4.2 volts per cell, and four partly charged at around 3.7 volts per cell.

I'm wondering if the charger is just not capable of charging packs in parallel, either via breakout cable or balance board ?

Could it be a problem with the balance board? What about a lead like this instead
http://www.hobbyking.com/hobbyking/store/__45752__JST_XH_Parallel_Balance_Lead_4S_250mm_6xJST_XH_UK_Warehouse_.html?strSearch=parallel balance

 

[Deleted member 4366]

Did you try 2A or 3A charge rate with the PC power supply? It's probably just voltage sag. I think I've only used mine up to 4A. Its marked 12V 15A (300w), but I know that it goes close to 10v at 4A.

 

[eHomer]

I've tried both Awol, I bought a balance board and also the two separate 6 way breakout leads, one for the main pos and neg, and one for the balance leads.

I was monitoring the input voltage to the charger Dave, and when it was set to 6 amps output with all six packs plugged in, it dropped to 10.8 volts.

I think I've found the problem now, (famous large words ).

I googled around a bit more, and there's another parameter in the Accucel's user setup called "Chk Time".

The instructions were a bit vague over exactly what it meant, but my best guess now is that the charger monitors the rising voltage while charging, and expects it to rise at a specific rate, depending on the number of cells selected by the user. The default is 10 minutes, and I suppose that is adequate for a single battery pack of the usual up to 5 amps. (and the charger works fine with single packs with that parameter).

However, I have six 5 amp packs, so my resultant 30 amp pack voltage rises much more slowly, and after 10 minutes it thinks the wrong cell count has been entered, and it shuts down.

I've just increased it to 40 minutes, and for the first time it charged two batteries in parallel with no problem.

My pack is now fully charged to 4.2v per cell in each pack, so I'll try a test run with the outboard in the tank with the alarm set to 3.6v, then I'll try charging again, and keep increasing that check time to see if it stops it.

Fingers crossed !!

 

[eHomer]

The fully charged 6 pack battery lasted 2 hours at full throttle on the outboard, dropping it from 4.18 volts per cell to 3.6 volts, when the alarm sounded.

I'm now trying charging again with all six paralleled together, and the chk time parameter set to maximum 60 minutes (instead of the default 10).

It did stop charging again with the vol select error, so I'm now trying "balance charging" instead at 0.5 amp. cells 1 and 2 are on 3.78 volts, and cells 3 and 4 are on 3.80 volts.

I also made my modification of the PC PSU into a more permanent job, replacing the multiple yellow and black wires with single 12 awg silicon red and black, and a proper connector, instead of the croc clips.

The input voltage while charging is now 11.6, instead of the 10.5 with the wires temporarily bundled together.

Thinking about the current capacity and volt drop of the connections though, the input and output leads supplied with the Turnigy charger are really thin, like 3 amp bell wire.

Do the more expensive chargers have thicker connecting leads ?

The output socket on the charger is 4mm banana plugs, but the input socket is a very small coax power plug, like on a phone.