Battery advice please..

Deleted member 4366 · Apr 25, 2014

You'll have to pay duty on Em3ev stuff too. If you know how to handle lipos, they're probably the best option because you can play about with the number of cells to get the right speed and power. You can always get a ready-made battery later when you're sure what you want. I like the 4S hard-packs that you can get from Hobyking. They're pretty cheap and have good protection against dropping, bashing, etc.

Arbol · Apr 25, 2014

d8veh said:
You'll have to pay duty on Em3ev stuff too. If you know how to handle lipos, they're probably the best option because you can play about with the number of cells to get the right speed and power. You can always get a ready-made battery later when you're sure what you want. I like the 4S hard-packs that you can get from Hobyking. They're pretty cheap and have good protection against dropping, bashing, etc.

Are the hard packs these ones ("car hardcase packs")?:

http://www.hobbyking.com/hobbyking/store/__15521__Turnigy_5000mAh_4S1P_14_8v_20C_hardcase_pack.html

There are very few of the in Europe and UK, mostly are only available at the Global warehouse.

Deleted member 4366 · Apr 25, 2014

That's them. They often run out but soon restock.

drsolly · Apr 25, 2014

I use those, and they're great, I love them. I put six or eight them in a hard plastic box, with a bit of foam padding, and use the beeper alarms to tell me when I have to stop using them. I put two of them in series for 8S, or three in series for 12s, or two plus a 2s 5ah in series for 10s, depending on the voltage that the bike wants.

And they're very cheap, compared to any other non-SLA batteries you might get.

Arbol · Apr 25, 2014

Do you buy them at the international warehouse? Because I believe I cannot see the ad at the European warehouse (even, not the Out of Stock sign). There are 60C, but the 20C, which are the cheap ones, do not appear anywhere but at the international warehouse, I believe.

Edit: yes, I have found the ad for all the warehouses, but under Cars, not under Batteries. Anyway, they are out of stock everywhere.

Arbol · Apr 25, 2014

Which charger do you use for those batteries? a cheap 4s? or a maybe a 8s charger fits two at the same time? I imagine a charger able to charge 4 6s cannot charge 6 4s, right?

Deleted member 4366 · Apr 25, 2014

http://www.hobbyking.co.uk/hobbyking/store/__26801__Turnigy_5000mAh_4S1P_14_8v_20C_hardcase_pack_UK_Warehouse_.html?strSearch=4s hard

I wouldn't advise bulk-charging lipos. It's not worth the risk. Get a proper balance charger and a balance board to charge multiple packs.

cwah · Apr 25, 2014

They are cheap but not that cheap... and you'll have to mess around load of wires.

I don't think it worth the hassle. Learn to make your own 18650 pack. You can buy cells for cheap.

drsolly · Apr 25, 2014

I get them from the Hobbyking UK warehouse. Yes, sometimes they're out of stock. I notice they're out of stock right now. But they usually rectify this in a couple of weeks. I've been paying $25 each.

You can also use these: http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idproduct=31951

2s 5000mah 20C. They're not quite as cheap, because you'll need twice as many. They are $15 each. But they are in stock right now.

For charging I use these:

http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idproduct=28150

But any good quality Lipo charger will work. You'll need a way to supply it with 12 volts; I use old PC power supplies.

I charge multiple packs using one of these for the balance leads : http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idproduct=45752

And I made a parallel main power lead myself, it's very easy to solder up. I call this my "charging cable. It just takes the output of the charger and splits it six ways, so I can plug in up to six batteries at once.

One caution if you're charging parallel - all the batteries should be at about the same voltage. If you connect up an exhausted battery (3.2 volts per cell) with a partially used battery (maybe 4.0 volts) in parallel, the 4.0 volt battery will send a *huge* current to the 3.2 volt battery. If you connected your balance leads first, that could burn them out, but even if you connect your main power leads first, that huge current flow isn't good.

So what I do is, I charge up all the fully depleted batteries, in parallel, and on a different charger, I charge up the partially depleted battery.

Yes, you do have to mess around with loads of wires; I made a "driver cable", consisting of a female EC5 (that connects ot the bike), a 40 amp fuse, a switch (I use a 53 amp circuit breaker), a 220 ohm resistor across the switch leads (to stop the spark on connection), a wattmeter (optional, that tells me the AH used by the bike) and two male EC5s so that I can put two of the 4S batteries in series. I also have four wires connected to this (also optional) that lead to my on-handlebar voltmeter and ammeter. A bit complex, but once made, it'll serve indefinitely.

So, when I'm riding the bike, I plug in the two batteries to the driver cable, the driver cable to the bike, and a beeping battery monitor to each battery http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=42953 (that means that I don't think I need a BMS). Then I can ride until one of the battery monitors starts to beep (telling me that one of the cells is down to 3.2 volts). So I stop, and plug in the next pair of batteries.

You really really don't want to bulk-charge without unplugging the serial harness, unless you have a BMS. If you do, then (for 8s) you're giving it 33.6 volts, but if one of the cells only charges up to 2 volts, the others will charge up more than the maximum, and you'll ruin the cells (and you're risking a fire). If you do have a BMS, then it will stop that happening, but getting and installing a suitable BMS for a battery system isn't for beginners.

I hope this helps.

Arbol · Apr 26, 2014

Thank you for all the helpful comments.

Nothing described in the last few comments is for beginners

What I am surprised is there are no BMS for lipos (AFAIK). There are the bestech ones, eg:

http://bestechpower.com/444v12spcmbmspcbforli-ionli-polymerbatterypack/PCM-D100.html

and they say these BMS are for both Li-ion and lipo, but:

Over discharge detection voltage
2.3V~3.0V(Adjustable)

is in the range for Li-ion, but not for lipo, which should be of the order of 3.5V (I remember in the past I sent an email to bestech asking about this specifically, but I never got an answer).

For a newbie like me, adding a BMS to these lipos would be a nice solution, because:

1. you do not need to spot weld, only solder (more widely available)
2. once cables are put in place, you do not need to take them out to charge
3. you do not need special chargers, a bulk charger suffices
4. if a cell fails, I believe it is much simpler to substitute under this arrangement rather than 18650 which have been spot welded and have some kind of RTV

Of course, lipos are not safe, so this is a massive drawback vs 18650.

I tried to do a search on ES about lipo and BMS, and there are a gazillion of posts, but surprisingly and AFAIK, no practical solution.

Arbol · Apr 26, 2014

Question:

if LVC = 3V for BMS bestech is a problem, what about having a 48V controller for a 12s battery?

If I look at pictures of BMSbattery, LVC for 48V controllers is set at 40V (plus minus 0.5V). Dividing 40 / 12 gives me 3.3333V. So LVC at the controller level is set higher than 3V. 3.3333V is not 3.65V yet, but would it be safe enough?

d8veh, do you know where the LVC for the 48V Xiongda controller is set up to?

Arbol · Apr 26, 2014

drsolly said:
I made a "driver cable", consisting of a female EC5 (that connects ot the bike), a 40 amp fuse, a switch (I use a 53 amp circuit breaker), a 220 ohm resistor across the switch leads (to stop the spark on connection), a wattmeter (optional, that tells me the AH used by the bike) and two male EC5s so that I can put two of the 4S batteries in series. I also have four wires connected to this (also optional) that lead to my on-handlebar voltmeter and ammeter. A bit complex, but once made, it'll serve indefinitely.

(...)

I hope this helps.

Yes, it helps a lot, thank you.

Would it be too much asking if you could take a picture of your "driver cable"? I would like to see how your setup looks like, if possible. I am especially interested in the combination fuse + switch + resistor (as well as the wattmeter, voltmeter & ammeter, and the male / female EC5, of course).

paul b · Apr 26, 2014

Wow they are light 58 volts 20amp for just over 2 kilos

Deleted member 4366 · Apr 26, 2014

Many people fitted a BMS to their lipos. It's OK as long as you test every function of the BMS. LVC at 3.0v is OK.Higjer would be better, but as long as it works, its only a safeguard. A wattmeter will stop you from running into the danger zone.

There's always a slight risk with using a BMS. If one function fails, you can have a nasty situation. Some of the worst fires on ES were when the BMS failed, but I don't know how well, they tested it before relying on it.

Arbol · Apr 26, 2014

I have asked Xiongda about the possibility of setting LVC of their 48V controller to 43.8V (3.65V for 12s) instead of the standard 40V:

"The Min.Voltage should be 40V+/-0.5V, so far what we make Min.Voltage for 48V Double speed motor set is always DC 40+/-0.5V.

If you prefere Min.voltage 43.8V,it is ok for us, but it will take longer time to oder from our controller supplier.we dont have stock of such controller you need now."

So, the LVC of the controller should be safe for lipos then (and the LVC of 3V at the BMS level would be an "emergency" one, hopefully never be tested).

Would that make sense?

drsolly · Apr 26, 2014

Arbol said:
Yes, it helps a lot, thank you.

Would it be too much asking if you could take a picture of your "driver cable"? I would like to see how your setup looks like, if possible. I am especially interested in the combination fuse + switch + resistor (as well as the wattmeter, voltmeter & ammeter, and the male / female EC5, of course).

A picture wouldn't help you much, it just looks like a mess. Here's a diagram.

I have EC5s on all the batteries. I use EC5s because they'll carry a *lot* of current, they solder on easily, you add the plastic housing after you've soldered it (so you won't melt the plastic while you're soldering) and they plug in and unplug without needing a big fight. Female on the batteries (and things offering power) and male on the things accepting power. They are impossible to plug in the wrong way round; you can't plug a negative into a positive, if you soldered the plug up the right way round.

The resistor in the circuit means that as soon as it's plugged in, the batteries slowly (a couple of seconds) charge up the capacitors in the controller, so you don't get a big spark. That saves the contacts on the switch. The switch is a domestic contact breaker, rated at 53 amps (so it should switch power off if there's a short circuit). £2.79 on Ebay, http://www.ebay.co.uk/itm/Gewiss-Series-90-GW-92-MT60-Type-B-Single-Pole-MCB-/180950744687?pt=UK_BOI_CircuitBreakers_RL&var=&hash=item2a21813e6f

But I don't rely on that, there's a 40 amp fuse (it's a car blade fuse, costs £1.10 on Ebay). http://www.ebay.co.uk/itm/LIQUID-ICE-14-GAUGE-AWG-IN-LINE-STANDARD-BLADE-FUSE-HOLDER-CAR-BIKE-BOAT-BIKE-30-/400591678378?pt=UK_BOI_Electrical_Components_Supplies_ET&var=&hash=item5d451febaa And, of course, I have a few spare fuses, which I carry in my puncture repair kit.

The shunt needs to be 0.75 milliohms. That's four inches of 10 AWG wire, you can work out how much you need if you use a different guage from this: http://www.powerstream.com/Wire_Size.htm. The ammeter/voltmeter sits on the handlebars, so I can see at any time, how much current I'm pulling, and the battery voltage.

The ammeter/voltmeter is from Ebay, £3.59 http://www.ebay.co.uk/itm/LED-Digital-Volt-Amp-2-in-1-Panel-Meter-Voltmeter-Ammeter-100V-100A-Blue-Red-/161224223929?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item2589b66cb9

The wattmeter is Ebay http://www.ebay.co.uk/itm/Digital-LCD-DC-60V-100A-Balance-Voltage-RC-Battery-Power-Analyzer-Watt-Meter-/201051715341?pt=UK_ToysGames_RadioControlled_JN&hash=item2ecf9db70d, expect to pay between £8 and £9. I have that down with the batteries, because it's easiest to put it there. I use it to tell me how many amp-hours the battery has done since being connected up. I use 5ah batteries, and I'm getting 4.5 ah or so. The batteries will slowly deteriorate over time, so when they only give me 3ah, I'll replace them.

The "battery to power voltmeter/ammeter" is a holder for four AAA batteries with a little switch. I run it until the AAA batteries are dead, then recharge them - this means that I could be without my ammeter/voltmeter display for a little while.

The series connector is just two EC5 males in series, connected to an EC5 female. It's just as easy to wire up three or four, depending on how many batteries you want in series to drive your bike.

As well as all the usual wiring on the bike, I have an ethernet cable going from the battery pack to the handlebars. That has 8 conductors; four are for the ammeter/voltmeter, two for a 5 volt power supply that feeds my PDA (which I use for navigation) and the other two will be feeding a headlight when I install it. The 5 volts comes from a step-down unit that runs from the bike battery, and the headlight will also be fed by the bike battery.

Here's the diagram.

http://blog.drsolly.com/2014/04/driver-cable-for-bike.html

Arbol · Apr 26, 2014

Wow, that is great, drsolly. By looking at the diagram, several things have become clear to me.

Just a basic question: since the wattmeter has already a voltmeter and an ammeter, why not just using the wattmeter? If I understand correctly, this would simplify the whole structure, since AAA batteries are not needed (does the wattmeter need AAA?) and the shunt is not needed.

I guess one reason for your choice comes from your comment "I have that down with the batteries, because it's easiest to put it there". But couldn't the wattmeter be put at the handlebar?

About the resistor, I assume the 220 ohm version of something like this:

http://www.ebay.co.uk/itm/50x-Carbon-Resistor-1-4W-1st-Class-Postage-UK-Resistors-0-25W-/290739434280?pt=UK_BOI_Electrical_Components_Supplies_ET&var=&hash=item43b16bb328

would work, right?

Battery advice please..

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