Ballistic Performance Components - EV02 Batteries

I'll take the high road and avoid accusing you of "misinforming". I respect what you do, you've done a ton for the motorcycle community, you've got tons of experience in this realm. If you could see the things I have with the 40+ brands of Lithium Ion batteries I've looked at over 1000's of hours in the last 3 years, you'd probably listen to my experience a little more....


You may be a guru with motorcycles, but I'm a guru with batteries.....

Regards,
Travis

 

Travis, any thoughts on how to charge this type of battery, i.e. will a Battery Tender work okay? One of my concerns is how to keep a charge in the battery during the off season (I'm located on the East Coast). Thanks!

 

holy bat farts batman this is getting heated..

 

Not heated at all.

More I am trying to dial in all the info.

JD himself wrote back in July of this year that (lead-acid) battery tenders are not compatible:

http://vfrworld.com/forums/mechanics-garage/35832-light-weight-battery-save-3-35kg.html#post325154

This said, it may be that the shelf life is such that they will winter over fine but I do think having the option to charge these would be of benefit.

 

If you want to recharge it in a total loss system, get a lifepo4 charger. Most Sealed Lead Acid chargers go well over 15V, which is a little too high. Should be fine with the onboard Regulator Rectifier for normal use.

Get one of these:
BatterySpace.com/AA Portable Power Corp. Tel: 510-525-2328 - Smart Charger for 12.8V (4 Cells) LiFePO4 Battery Packs

See post below, you don't need to trickle Lifepo4.

 

Oh, Ok, I see what you're really asking....the shelf life for lifepo4 is great! Just disconnect it during the winter. They have a very VERY low self-discharge. You probably won't even need a charger..... you don't need to trickle.

 

Okay, so as noted I would need an 8-cell unit for my 500.

If I could ask, how long will one of these hold a charge on average, i.e. when would you need to look into investing in a charger?

Can you charge a battery like this if it does not have a balance port?

 

Acting as a discussion balance both JD and Frodus are right; it's the level of detail that makes their differences.
If primary goal is getting all energy from batteries and charge them back as fast and safe as possible then Battery Management is the way to go.
If just starting energy is needed and a "constant voltage" standard motorcycle charging system is used for recharging the battery then BM is a bit of over engineered for purpose though it can be beneficial in some circumstances.

IC you will probably start the bike to warm up every few months for the sake of the engine and carbs and in any case you will need need nothing more than that for the sake of the battery.

 

Are you asking how long would a battery left sitting disconnected last?

If so, It's Over a year without even being touched. I've had cells that are 2 years old, haven't touched them and they've barely lost any charge.


You can charge the battery with or without the balance port.

 

Yes, sorta.....It actually happens whenever you put energy into or take energy out of the battery. The more total energy you put in/take out the more unbalanced they become. Now in a normal case, as Jamie is saying, you don't take much energy out, and you don't put much back in, and it's never completely discharged, and you don't do it very often.

My point is, every time you discharge a battery, most of the current goes to the circuit, but a small energy is dissipated in heat due to the Internal resistance. Since no 2 batteries are the same, the energy dissipated by each battery is different. Over time, this becomes more and more pronounced.

For a nice little graphic of how it works, Go here:
Elithion - Call balance visualizer

Put in:
4-cells
same capacity
100% SOC
random leakage
No balancing
random control

Let it sit there, watch it. Even if you sit there and only discharge like 10-20% (as you would by starting your motorcycle with a 2.5Ah battery), and charge, discharge, over and over.... the minute differences start to make a difference.




I'll provide some numbers:

Now, lets say you're using a 2.5Ah pack (like Jamie), discharging it at 150A (40C, like Jamie) while starting the engine cold, the pack voltage at rest is something like 12.8V. Now discharge at 150A, and you drop to something like 2.5V a cell (about 10V) while you're starting for.... lets say 5 seconds.
That works out to be 2.5V * 150A = 375W per cell, but since it's only for 5 seconds, we divide by 60 minutes, then divide by 60/5s = 12, or 1/720 of an hour. 375W/720 = 0.52Wh.
The battery is rated for 3.2V * 2.5Ah = ~8Wh. 0.52Wh is about 6.5% of the total energy in that cell, just for 5 seconds. That's just the amount of energy out of the battery, lets look at the IR.

Now lets say batteries 1-4 have IR values of 9,10,11,10 mOhm each (from the A123 datasheet for DC Internal Resistance, they're around 10mOhm).

Under 150A, the energy dissipated by each cell is
1: Power = 0.009ohm * 150 ^2 = 202.5W, for 5 seconds would end up being ~0.28Wh of energy dissipated.
1: Power = 0.01ohm * 150 ^2 = 225W, for 5 seconds would end up being ~0.31Wh of energy dissipated.
1: Power = 0.011ohm * 150 ^2 = 247.5W, for 5 seconds would end up being ~0.34Wh of energy dissipated.
1: Power = 0.01ohm * 150 ^2 = 225W, for 5 seconds would end up being ~0.31Wh of energy dissipated.

So not only are you dissipating 0.52Wh from each cell, you're dissipating the above energies..... Adding these to 0.52Wh, you get:

1: 0.8Wh, which is 10% of the cell capacity.
1: 0.83Wh, which is 10.38% of the cell capacity.
1: 0.86Wh, which is 10.75% of the cell capacity.
1: 0.83Wh, which is 10.38% of the cell capacity.


slight differences, but they're there..... even if the differences weren't 1mOhm, and more like 0.5mOhm you get some differences, and after time, after charging/discharging, the cells will each have a different state of charge.



And the one thing that makes all of this confusing, is if you put a multimeter on a pack, at rest, to check the voltages of the cells after you cranked over the engine, they'd all be resting at almost the same exact value, they tend to rest at their nominal value regardless of their state of charge..... Voltage alone doesn't tell you the whole story.

 

Okay, got it, I think. Thanks for taking the time to explain the details.

Again not trying to stir things up here but am I correct in understanding that a balance port while not necessary is technically a good thing to have on this type of battery?

 

Required? No.

Would it help you keep your pack longer? healthier? In my opinion, Yes. Would it be good to have on it? In my opinion, Yes.

 

I spoke with Dan about including a balancing tap in the packs. After much head shaking and questions about "why", he said that it's really not be a problem to add this. For those people interested he will install a balance cable assembly to the packs for $5 each. There are several balance devices on the market (mostly for the RC guys) that could be used. Those are pretty inexpensive items, if it's peace of mind you are looking for then it should do the trick.

 

Great solution for those that want it as an option, cheap insurance.

and BTW, you're not going to have to balance it all the time, these batteries require little maintenance, just once in a while, like maybe when you put your bike away for the winter.

 

A big thanks for this JD. I very much appreciate you talking to Dan (even if he thinks we're a bit batty) and a shout out to Travis for the great info he posted above.

In terms of charging these, for example let's say your engine doesn't start and you drain the battery, what charger does Dan recommend for an 8-cell?

 

So, here is excatly what I was saying. You caused a bunch of trouble and got IC all excited earlier in this thread by stating a balancing circuit is needed. You have slowly moved away from that point and now you are stating that a pack without a balancing device is just fine. This is what I have been stating from the begining. It could have saved us all a bunch of trouble if you would have taken a step back a few days ago and realized the application and the fact that a balancing device really does not appreciably benefit the pack life.

Since you will unboutedly need something to retort, here are some points to ponder:

- DeWalt 36V drill battery uses LiFePO4 cells, which is the same chemistry as the Lithium motorcycle packs. The drill batteries have three times the number of cells in series as do the motorcycle packs and are drained almost completely each use. They do not contain a balancing device. Why? Because it's not needed.
- Your stock lead-acid battery contains 8 cells in series, it also does not contain any balancing device. Why? Because it is not needed.

 

Stock 12V lead-acid battery contains 6 cells in series, not that it makes any difference in your argument.

 

I know you're asking Jamie/Dan.....

don't use a lead acid charger, it'l charge to over 3.7V a cell, which is the max you should charge these to get long life out of them. There are a few (under $30) chargers for life batteries. If you need help I can always point you towards something that will work well.

 

5x5, thanks.

 

You shoulda just left it be, since you now have it as an option and it would have shut me up..... In fact my response to you was very positive.

Wrong.....I asked where is the balancer or balance port. If you don't have a balancer onboard, then a balance port should be there so you can use a balance charger.... I've not backed down or changed. My point (again): Batteries WILL go out of balance and you "had" no way of rebalancing the pack..... but you mentioned it's an option for people now..... should have been the end of it..... Is it needed? it's not required, but without it, the battery WILL NOT LAST AS LONG AS ONE THAT IS PROPERLY BALANCED.

You forgot to quote all of what I said:

ACTUALLLLLLLY, they do have one! Go take one apart, there's a little circuit board inside. It's the balancer! They acutallly wire to each cell, and balance the batteries. I know this because I have a couple sitting in my shop. 10 cells of 3.2V lifepo4.....dewalt A123 battery pack. I use them all the time building packs for people. A123 actually requires a BMS on all of the products that manufacturers/OEM's install cells into. It's part of their contractual agreement.

Doubt me: Here's some pictures:
Dissecting DeWalt 36V Packs (A123 Systems)
Disassembly of a DeWalt 36v Battery - RC Groups

You know why they don't need one? Because all of those plates are in the same electrolyte.... it's one big battery with lots of little electrodes, but all in the same electrolyte solution with the same potential energy between each cell..... They do actually become unbalanced because of sulfate on the electrodes causing differences between plate voltages.... which can be eliminated by an equalization charge (a setting many new battery chargers have on it).... this removes the sulfate by overcharging them slightly and boiling the sulfate off.

Your 4/8/12 cells of Lifepo4 batteries don't share electrolyte.