Commute - charge both at home and at work?

benend · Jun 8, 2015

I bought a Pedego recently, and their web site says to keep it fully charged and to charge the battery even after a short ride.

Does that mean that if I commute, I should charge it at work as well as home? Or is it enough to just charge when I get home?

fredfire · Jun 8, 2015

It depends on the battery chemistry, but it's better to never fully drain a lithium battery for it to keep a good life.

Always keep it between 30% to 80% and it's perfect, never overcharge it.

wineboyrider · Jun 8, 2015

How far do you travel? What kind of battery do you have? Tell us more about your situation?

dnmun · Jun 8, 2015

your battery will produce power most efficiently when it is fully charged. if you only charge your battery to 80% then you are damaging it when you discharge it because the ability of the battery to conduct the current depends on the amount of available free lithium ions to conduct the current. the most free ions are available at full charge, not at 80% of charge. if you start discharge with a partially discharged battery you are inflicting harm on the battery for no reason.

you should charge at every opportunity, but do not leave it fully charged if you are not using it. so if you can charge at work conveniently that is what you should do. only charge it when you use it but charge it up to full charge to use it.

cwah · Jun 8, 2015

dnmun said:
your battery will produce power most efficiently when it is fully charged. if you only charge your battery to 80% then you are damaging it when you discharge it because the ability of the battery to conduct the current depends on the amount of available free lithium ions to conduct the current. the most free ions are available at full charge, not at 80% of charge. if you start discharge with a partially discharged battery you are inflicting harm on the battery for no reason.

you should charge at every opportunity, but do not leave it fully charged if you are not using it. so if you can charge at work conveniently that is what you should do. only charge it when you use it but charge it up to full charge to use it.

Harm only happen on deep discharge, so partial charge are good and recommended

d8veh · Jun 9, 2015

It's OK to only charge it only at home, provided that it doesn't become empty before you get home.Their advice is to keep it fully charged when practical.. The higher the state of charge, the more power and torque you get. A fully-charged Pedego battery gives 12.5% more power than a half-charged one.

I wish these people who mention charging a battety to 80% to lengthen its life would qualify their statements. It works for some batteries, but would destroy a Pedego one. It only works if you have a battery management system that balances at all states of charge (not common) or if you manage the balancing yourself.

voicecoils · Jun 9, 2015

If it is convenient to charge at work, I say do it. The bike will be quicker and zippier on the ride home then. It also means you can take longer side trips on the way home if the mood strikes.

But, if charging at work is a pain and the bike can do the round trip easily then just charge at home, no big deal.

dogman dan · Jun 9, 2015

Well, ask a too general question, and you get too general answers, all of which are right under some circumstances.

If you have a lead battery, Charge at every opportunity, and keep it fully charged as much as possible. Even if work is only 2 miles away. Lead MUST be kept full at all times.

If you have lithium, and work is 2 miles away, charge at home. Ideally, charge in the am so the battery does not sit fully charged all night. If it works out better, you could charge only at work, starting the charge at noon or whatever.

If you have lithium, and work is 5 miles away or more and your battery is 10 ah size, charge at work and at home. Again, ideally not until you actually need it full.

But in the end, really, you have to use this thing in the real world. When I did a long daily commute, I needed to charge at work to make it back home. And back home, charging took till past my bedtime. That battery was kept on the charger 22 out of 24 hours a day for five days each week. Then it would get charged some on the weekend, for fun riding. That lifepo4 battery still lasted 3.5 years.

So do what make it livable for you. Sure, the battery is expensive, but your free time is worth a lot more than a few bucks.

benend · Jun 10, 2015

All good info - thanks. I'm still learning.

Commute is 8 miles each way
Battery is Pedego 36v10ah Lithium Ion

From what I understand then, for Lithium Ion:
1. Don't store it 100% fully charged.
2. Don't discharge past 20% if you can help it.
3. Charge it as close to using it as possible.

And the recommendation from Pedego that you should charge it after every ride - no matter how short - that's incorrect?

wesnewell · Jun 10, 2015

If it's lead, it's best to keep at full charge. Not so with lithium. Keeping it at full charge does damage. Not charging at work won't hurt it a bit as long as iot has enough capacity left to get home without over discharging. An ideal situation would be to fully charge before leaving for work and getting back home with a 10% or high soc.

Jonathan in Hiram · Jun 10, 2015

I suspect Pedego is trying to keep people from over discharging their batteries which is very bad for them. Charging after every single ride no matter how short is not optimum but it's better than over discharging, many people aren't good about charging when they should and Pedego knows this so they are trying to account for normal human behavior.

You have 36*10 or 360 watt hours and your ride is 16 miles which if you run the battery all the way down would be 360/16 or 22.5 watt hours per mile. My guess is if you try to ride both directions on the same charge you will sooner or later over discharge your battery (strong headwind one day perhaps or maybe a tire going flat, brake pad rubbing and so on) so better to charge both ends of the ride.

If you aren't riding the bike on weekends leave it (approximately half) discharged after you arrive home and charge on Sunday night before your Monday commute (modify to your particular schedule if it's not M-F work).

dogman dan · Jun 11, 2015

But since his use pattern is commuting, and his capacity is a bit low for going both ways, that's exactly how he'll be using it anyway, whether he likes it or not. Likely he can make it both ways now, but the battery will last longer if he charges at work, and lowers his discharge depth each ride.

Ideals are ideal, and the real world just gets in the way of ideals. Charge at home, and at work. If you like, delay starting the charge when you get home. But honestly, that's just a pain in the ass when you get home.

Get two chargers. keep one at work. When you get home, plug in your bike and stop worrying about it. You need it in the morning, and relying on a timer just brings in another way to wake up to an un charged bike in the morning.

When you know you will drive to work tomorrow, that's the day to charge later.

If he had a 15 ah battery, then he'd have the right capacity to do his ride by charging it only at work, and not charging at home. Then he'd go overnight with the battery half charged.

Stop thinking about it, charge every time you ride to work, and back, and get on with other things.

benend · Jun 11, 2015

Great info - thank you! I brought the charger with me to work today. The throttle still reads green "Full" though it's hard to tell what that means. When you think about it, battery care is like managing your MPG.

So if I get home and charge it - what if I just charged it for an hour - then it would be at 80% or so, then in the morning fill it up? Does each charge reduce battery life?

Ykick · Jun 11, 2015

Definitely grab 2nd charger. You’ll also be glad you did somewhere down the road if/when a charger fails.

Charge cycle count has little to do with longevity, IMO. It’s really how deep you go and long-term storage which has demonstrated to be what degrades battery packs.

I regularly charge after every commute and only worry about sitting full charged if it’s gonna be more than 24-48 hrs before I would be able to burn off a little top charge. Otherwise, it seems to make little difference. I’ll repeat what the others have said, shallow discharges are best.

To really understand what’s going in/out you’re gonna need a power meter. Preferably a CA (cycle analyst) but don’t forget proper wire and connectors in order to make needed connections.

chas58 · Jun 11, 2015

I'm confused about something. If you have an LCV in your BMS and in your controller, How do you over discharge your battery? Isn't this the purpose of having a 36v battery cut out at say 28 volts, or is that too low for most circumstances?

My ride is about 18 miles, I have a 24 mile range (36v10ah), so I just charge at home.

wesnewell · Jun 11, 2015

The LVC for different types of 36V batteries should be different. Most BMS will allow you to use every bit of the battery and even more than that in some cases. The controller LVC should shut you off before the bms does. For a 36V lead pack, lvc should be ~31V. For 10s rc lipo, it should be ~35V. For 10s 18650 type, it should be ~30V. For 12s lifepo4, it should be ~32V. These are conservative that should keep you from over discharging.

cal3thousand · Jun 11, 2015

if you only charge your battery to 80% then you are damaging it when you discharge it because the ability of the battery to conduct the current depends on the amount of available free lithium ions to conduct the current.

Saying this is equivalent to saying that you damage your battery if you use it below 80% SOC. EVERYONE'S battery eventually hits this point. Starting out here is no different than riding down to 80% then continuing again down to 60%.

Where do you get this stuff?

dnmun · Jun 11, 2015

because it is true. if you discharge your battery from less than full charge it creates more heat internally than it would if you discharged it from the full charge.

if you need to understand more then go study the term transconductance and look for the letter N in the equations that are the population of ions used in the the transport equation. then you can try to insult me some more if your mind can understand the term transconductance.

chas58 · Jun 11, 2015

Yea, so if your controller limits the discharge, what is the harm in running the battery until it cuts out?

wesnewell said:
The LVC for different types of 36V batteries should be different. Most BMS will allow you to use every bit of the battery and even more than that in some cases. The controller LVC should shut you off before the bms does. For a 36V lead pack, lvc should be ~31V. For 10s rc lipo, it should be ~35V. For 10s 18650 type, it should be ~30V. For 12s lifepo4, it should be ~32V. These are conservative that should keep you from over discharging.

dnmun · Jun 11, 2015

the heat produced in the battery when you push current through it in a low charge state causes damage at the electrolyte to SEI/electrode interface. this is how the gas is formed that causes the pouches to puff up.

dogman dan · Jun 13, 2015

Back to the night charge, Life is short, free time even shorter. Just charge it when you get home and stop fretting. Leaving it charged overnight is not going to shorten it's lifespan so much it's worth fussing over.

But when you know you won't ride for 2-3 days, go ahead and wait to charge it.

Sure, it does matter, but it's not going to cut the lifespan by half or anything close to that. Make the bike easy, too much else in life is hard.

Definitely don't worry about cycle count. 500 100% cycles, 1500 30% cycles, all same. Be happy if you get 2 years commute use, but you may well get 3 or even 4 years, if you try not to discharge so deep every cycle. Light discharges avoid that heating, and a cooler battery is a happy battery. Be easy on the discharge and your battery will last as long as it can, from less hot discharges.

Discharge deep when you need to though, without worry. The bms will stop it going too deep. But don't discharge deep when you could be charging it back up.

Commute - charge both at home and at work?

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