What's Better? Use up more Ah's or Charge more often?

[dogman dan]

In his situation, if his bms balanced at 80% that would be great. Or if he had a charger that charged even just 5% less he could use most of the time, that would also be ok. He's got plenty of extra capacity.

But he's got a bms and charger that goes to 100%, so he should charge fully every 3rd ride at least, and ideally not let the battery sit any longer than till morning fully charged when he does.

 

[tomjasz]

If your goal is maximum cell life, charge to 85% of maximum capacity, and recharge to that 85% as often as possible (so most shallow cycles). Many cells will last many 10s of thousands of shallow cycles like 85% SOC to say 40% SOC.

If you have a ride when you need the full pack capacity, charge to 100%.

I'm intrigued. How do you stop the charger at 85%? Doesn't the charger have to balance the pack after the charge cycle? How would it do that if you stop the charger early? I'm not questioning, I just don't know. Do you just kind of keep an eye on it and stop it at a certain Voltage?


ETA: My Charger is set to charge this pack to 96.6V

One of the fellows I built a bike for uses a timer. He's determined how long it takes to get to the charge he wants from a starting point. took a few days of fooling around but he's got a little chart for his batteries an he gets within fractional voltage levels. OR Buy a Luna Charge with 80, 900 and 100% setting for $99. OR buy a Satiator to do any battery up to 60V at any level you program.

 

[Lurkin]

I was under the understanding that the BMS controls the balance cycle point and bleeds the packs to bring into balance.

Is there any way this can occur with the luna charger without having to access the BMS? If so, I think I need one! 8)

 

[tomjasz]

If you are charging to 80 or 90% may suggest occasional 100% charges for a longer period to let the BMS do it's job balancing. My understanding is at 80% the BMS typically does not balance the pack. Check our the Satiator site for confirmation from Grin and Justin. I went for the satiator too. Having one charger for 3 different voltages is sweet. Soon I'll have a 52 V and I already have a charger that will do that too. Speedy but buying and owning 4 different chargers is almost as spendy.I use the cheap chargers for me 100% charges if I need to charge two packs. Every batt I bought came with a crap charger.

I assume all BMS are less than high quality BMS, except perhaps Allcell and such.


http://www.ebikes.ca/tools/charge-simulator.html#benefits-of-partial-charge


One of the only downsides to partial charging is that many inexpensive battery management system (BMS) circuits will only do active bleed balancing of the cells when they are at or near the full charge voltage of 4.2 V/cell. This means that with partial charge profiles that don’t reach that voltage, the BMS circuit will never be able to rebalance cells if they are drifting apart. Over time you may have less available capacity from the pack as certain cells will hit the low voltage cutoff on discharge well before others.

If this is an issue it can be easily remedied by occasionally (like once every month or two) leaving the pack connected to a 100% charge cycle overnight.

Good quality programmable BMS circuits will usually attempt to balance the cells whenever they see more than a certain voltage spread between the highest and lowest cell in the group, and in that case there is no problem with partial charges. Similarly, good quality cells rarely drift out of balance in a series string, and can easily handle 100 or more cycles and maintain a perfect voltage matching even if the BMS circuit doesn’t do any active balancing. But if you aren’t sure of the makeup of your battery pack, then the protocol of occasionally giving a 100% top-up is a good bet to ensure both a long cycle life and evenly matched cell voltages.

 

[999zip999]

Just use the charger and bms combo that came with the pack. The worse things is not using and charging the battery. Best to use your bike. Not all batteries packs would not like not being used ? Months ?

 

[Ottodog]

Second charger that only charges to 85% would be the easy way to do the 85% to 60% routine. Then occasionally, charge to 100% with the other charger and ride immediately, to get balanced once in a while.

I hesitated to suggest undercharging at first, mostly because of the cost of the new charger, and the slight inconvenience. At some point, we have to decide what is first priority, maximum battery life, or maximum convenience. Given the very short ride you do, it's very likely that your battery will time out in 3-4 years, rather than get used up. This will be the result of using the battery in the real world, unlikely that in summer it will be ridden in a cool environment, or have shade covered parking all day while you work. Because of this, I'm inclined to say the thing to do is just charge every 2nd or third ride, and not worry too much about undercharging all the time.

But if you find yourself needing a new charger anyway, EM3ev has one with a switch so you can choose a 90% charge anytime. I use one often, and typically don't need 100%, so I charge to 90% a lot. Why not, if it's that easy. But I still expect that battery to start really losing capacity this summer, it's 3rd summer.

I like the idea of that. Do you have a link to the specific charger? I'd like to check it out.

 

[dogman dan]

Assuming your pack is 14s,,, this charger. Likely to be about $100 by the time you add shipping.

http://em3ev.com/store/index.php?route=product/product&path=35_37&product_id=120

When you use the switch for a partial charge, you will get no balancing. NONE. So you will need to balance it once in a while. Because of your light duty use pattern, healthy cells in your pack will tend to stay balanced a long time. Even so, I'd still want to go ahead and charge to full about twice a week to balance it. Much less possible if you could confirm the packs balance, but you have no easy way to do that. So just balance often enough to be sure.

Apparently Luna also has a charger with the partial charge switch now. cool.

Supposing you do get a charger that does an 80 or 90% charge, in that case, I'd say very little to gain by not charging daily. And the flip side, still no real reason not to charge every other ride. Charge to 90% every other day just about perfect for you. And, never anything wrong with having a spare charger. In fact, downright dumb to rely on just one charger if you use the bike for real transportation to work.

 

[dogman dan]

Reading back, I'm not sure you ever said what your battery voltage is. To show you what charger you need, we need to know exactly what voltage your battery is, when full. Measured, not what is written on a charger or the battery.

54.6 is typical for a 13s 48v battery. But some are 14s, and charge to 58.4v. EM3ev has both, or also 36v types.

 

[tomjasz]

I've gone back to cheap chargers as backups to my Satiator. All 2A.

 

[tomjasz]

Reading back, I'm not sure you ever said what your battery voltage is. To show you what charger you need, we need to know exactly what voltage your battery is, when full. Measured, not what is written on a charger or the battery.

54.6 is typical for a 13s 48v battery. But some are 14s, and charge to 58.4v. EM3ev has both, or also 36v types.

EM3ev has a 36V selectable BUT it's a 6A charger and none of my 36V packs can be charges at 6A. Even the ones that came from EM3ev.

The devil is in the details.

 

[Ottodog]

If your goal is maximum cell life, charge to 85% of maximum capacity, and recharge to that 85% as often as possible (so most shallow cycles). Many cells will last many 10s of thousands of shallow cycles like 85% SOC to say 40% SOC.

If you have a ride when you need the full pack capacity, charge to 100%.

I'm intrigued. How do you stop the charger at 85%? Doesn't the charger have to balance the pack after the charge cycle? How would it do that if you stop the charger early? I'm not questioning, I just don't know. Do you just kind of keep an eye on it and stop it at a certain Voltage?


ETA: My Charger is set to charge this pack to 96.6V

Reading back, I'm not sure you ever said what your battery voltage is. To show you what charger you need, we need to know exactly what voltage your battery is, when full. Measured, not what is written on a charger or the battery.

54.6 is typical for a 13s 48v battery. But some are 14s, and charge to 58.4v. EM3ev has both, or also 36v types.

I did mention it, but it got kind of buried. The Pack is 96.6V at full charge but the Charger typically tops out around 96V or so.

 

[999zip999]

96.6volt you have a link to your battery. Not to many 96 volt batteries on the maket. What cells ?

 

[Ottodog]

96.6volt you have a link to your battery. Why would it only top out at 92 volts ?

Sure: http://www.hi-powercycles.com/new-hpc-elite-90v-13ah-li-nmc-ultra-high-performance-battery/

It uses Samsung Cells as far as I know. The link has the full specs. The Charger says 96.6V but It tops out at 96V and they told me it was within spec.

 

[999zip999]

They are a little secretive of what cells that they use but it seems like they use a very high quality cell. Meaning it has a better chance of staying in balance. Quality helps.
HPC makes you pay.

 

[Ottodog]

They are a little secretive of what cells that they use but it seems like they use a very high quality cell. Meaning it has a better chance of staying in balance. Quality helps.
HPC makes you pay.

As far as I know, they're using Samsung. 23 cells in series. Yeah, pricey as all hell.

 

[999zip999]

24s1p 13ah pouch cells ? Samsung 23 I will look it up. But don't think so. Prove it.

 

[Ottodog]

24s1p 13ah pouch cells ? Samsung 23 I will look it up. But don't think so. Prove it.

It's technically an 86V battery as I understand it. The old ones had a split pak with 12 in each (24 total), and a double charger. The single Paks are 4 less volts and one less cell (23 total), but are supposedly more reliable with the single BMS and a single Charger.

 

[Sunder]

Wow, at that price, I'd hope it came with a lifetime guarantee. No wonder you want to treat it with kid gloves.

 

[waynebergman]

I have a 2 battery packs, one at 14s and 1 @13s.They are the Panasonic PF cells. For my main pack, the 14s I have a charger that I can charge to 80 or 90 % for most of the time so thats great. However my second pack at 48v I only have a cheap charger for it and it charges up to 100%. For this 48v pack as I only use it as a range extender in my back pack and it only will get used say once a month or so. I am not sure if its best after this 48v pack has been say run down to say close to empty after a ride is it OK to leave it for a full month at this low state of charge and then top up just before my next ride? I have read its best to leave at 50% for extended storage but I don't have that option. With the charger I have for this 48v its either 100 % or not at all. So my question is if the 48v pack sits on the shelf for a full month with out being used is a very low SOC just as bad as a full SOC?

 

[Jon NCal]

I have a 2 battery packs, one at 14s and 1 @13s.They are the Panasonic PF cells. For my main pack, the 14s I have a charger that I can charge to 80 or 90 % for most of the time so thats great. However my second pack at 48v I only have a cheap charger for it and it charges up to 100%. For this 48v pack as I only use it as a range extender in my back pack and it only will get used say once a month or so. I am not sure if its best after this 48v pack has been say run down to say close to empty after a ride is it OK to leave it for a full month at this low state of charge and then top up just before my next ride? I have read its best to leave at 50% for extended storage but I don't have that option. With the charger I have for this 48v its either 100 % or not at all. So my question is if the 48v pack sits on the shelf for a full month with out being used is a very low SOC just as bad as a full SOC?

I think it's not so good to leave it empty, so why not just charge it for an hour or so when you get home? Then charge complete to full just before your ride.

 

[MrDude_1]

I really wish people would differentiate between a battery and a battery system...

A battery is just the cells, connected in series and/or parallel.
A battery system has a BMS, and possibly contactors and other parts.

When you're charging a battery, you (or the charger you choose) can control everything that happens.
When you're charging a battery system, your control is limited to however much you control your BMS.


So... charging a BATTERY to a specific voltage (or percent) is easy. You can have it balance at that level too.

Charging a battery system to a specific voltage, involves setting the BMS to hold and balance at that voltage. If you do not have control over this, it becomes much more difficult. Especially if you have a "dumb" BMS that will allow the cells to drift further apart if you dont hold it at a full charge for it to balance.

 

[Ottodog]

If your goal is maximum cell life, charge to 85% of maximum capacity, and recharge to that 85% as often as possible (so most shallow cycles). Many cells will last many 10s of thousands of shallow cycles like 85% SOC to say 40% SOC.

If you have a ride when you need the full pack capacity, charge to 100%.

I'm intrigued. How do you stop the charger at 85%? Doesn't the charger have to balance the pack after the charge cycle? How would it do that if you stop the charger early? I'm not questioning, I just don't know. Do you just kind of keep an eye on it and stop it at a certain Voltage?

ETA: My Charger is set to charge this pack to 96.6V

Some chargers are smart enough to charge to a certain % for you, like some RC chargers and I think the Cycle Satiator. Lenovo notebooks have a similar battery management option to extend battery life.

An alternative is to use a voltage which matches your cells. If you know what type of battery is in your pack, you can use a discharge curve to get an idea of where you should cutoff charge and discharge. Basically, when you look at a discharge curve you will see a point where the voltage rises sharply near the ends. If you draw a line to best fit the bulk of the discharge curve you can get an idea where to cut it off by excluding the steep ends.

Something isn't adding up if they say it is 1P in the details. It makes sense to be 24S5P and for the current rating it might be 25R, but AH rating suggests something else unless they round up. Elsewhere it quotes 1000 cycles, but of course accurate marketing has been a bone of contention that has gotten better but is not yet perfect.

I think I could do it with Voltage. I know about what Voltage my pack will be at with about 80% charge and I do recall them saying it was okay not to charge the pack fully every time. How often should one balance the Pack?

 

[tomjasz]

Luna charger has 3 settings, 80% 90% and 100% I think better quality than EM3ev and on par pricing, $97 from EM3ev with long distance warranty and long wait time or $106 for USA warranty and much faster shipping from Luna.

52V http://lunacycle.com/luna-charger/luna-charger-52v-advanced-300w-ebike-charger/
48V http://lunacycle.com/batteries/chargers/luna-charger-48v-advanced-300w-ebike-charger/

EM3ev gets a lot of press but when I went to repair my EM3ev charger it had a fuse and fuse holder but it was never soldered in to the board. It was never replaced and just shrugged off by the supplier as a non issue. Disappointing.

USA suppliers usually do better jobs at warranty service.

I missed the mark on this one. The Satiator is a vastly better charger and mine is more than a year old. Both Luna chargers are dead after 3 months. Now on version 4 I see. I'm all in for Satiators, or the charger that comes with packs from pack supplier for travel or backup. Yes I even have a backup for my Satiator. New rule, throttles, controllers, and chargers all have backups or a complete backup bike.

 

[LockH]

Interesting... maybe? In an ES "Search found 44 matches: +dendrite"? (Including once in this thread.) Any mention yet of watt flavour of "lithium" cells we're tapping about here? Lithium Manganese, Iron, etc? And, just curious, might dendrites be a function of partly discharged and unused? Or do dendrites occur whether charging or not using or discharging? Just curious. Tks. Any dendrite formation tied to ambient temps or internal resistance/self heating?

EDIT: Back in the daze of riding SLA the "rule" was Charge Early (and Charge Often). Currently sitting on a no-name "Lithium" pack (48V, nominal "10Ah"), unused for weeks now, kept inside at room temps. "Fully charged", had left with charger unplugged. Just now, plugged in and "idiot light" LED on charger went to green right away. (Zero time as red, aka "charging".) HAD thought that "lithium" charge was supposed to "degrade" over time?

 

[999zip999]

Tomjasz did you contact luna about your chargers ?
Why they quit ? The smoke came out ?
Most problems I see are with people not putting the battery on the charger and then it is dead.