lifepo4 charging

[slafko76]

I have LiFePO4 battery 48V/12Ah with range cca 40km. My daily tour is 18km. Do you recomend to charge every day or every 2nd day? I have possibility to charge at work too, so that would make 27km/charge every 2nd day. Whats best for battery life?

need advice pips, till now i charged daily, can i save few cycles of battery charging every 2nd day?

 

[dnmun]

charge more, don't overcharge, but if you are using the pack it is best to use power from the top of the charge, not the bottom.

if you discharge it deeply it is harder to keep the pack in balance. if you discharge any lifepo4 cell below the 2-2.1V level while under load it damages the cell.

 

[Jeremy Harris]

As dnmun says.

Definitely charge "little and often" if you can. Cycle life is non-linear with respect to depth of discharge, so if you discharge to, say, 80% of total capacity and then recharge you might get 600 to 800 cycles, but if you discharge to, say, 50% of total capacity and then recharge you might get 2000 cycles. If you're fortunate enough to only discharge to 30% or so then you may well get many thousands of cycles (although age degradation will probably reduce capacity a fair bit before that happens).

 

[N!co]

Can you leave the charger connected overnight after every commute? Or should you disconnect as soon as charging is ready?

 

[slafko76]

i'm charging for 14 hours, over night
i have possibility to charge 22h/day if that's good, 14 hours at home and 8 hours in the office, riding 9 km between charges, using only 25% of battery

 

[Jeremy Harris]

Best to disconnect the charger as soon as the pack is charged, in my view, both for best pack life and for safety.

There's a slight degradation in life from keeping cells right at their maximum charge voltage for long periods, so if you can charge just before you use the bike that would be ideal, otherwise just turn the charger off as soon as you can after the pack is charged. If this is inconvenient, overnight charging, for example, then you could maybe fit a time switch to the charger, set to turn off a short while after you are pretty sure the pack will be fully charged.

 

[dogman dan]

Jeremey is always right, but depending on the situation, you might want to leave it charging overnight. If you have done a deep discharge, then you will need to let the bms of the battery have more time to balance the pack. The charger will cylce on and off repeatedly, and might need all night to get it fully charged and balanced.

I commuted about 10,000 miles on ebikes, and pretty much the only time the battery was not on a charger was when my butt was on the bike. My commute required a pretty deep, 80% discharge twice a day, so my battery needed that longer charging to keep it balanced. The battery still lasted 3.5 years, so long enough to pay for itself three or four times over.

But in your case, lots of short cycles possible, your battery should remain balanced nicely, finish charging long before you go to bed, and then you should take the battery off the charger. Perhaps monthly, you could charge longer so as to be sure the bms has time to balance the pack.

Do use a voltmeter from time to time, or better still have one on the bike. The voltmeter will tell you right away if a charger or bms is not working right and the battery is overcharging. Or if it won't charge completely because it's out of balance, you'll see a few less volts than normal.

 

[dumbass]

In most all cases I would bow to the experience and knowledge of both dogman and Jeremey. But there's something about leaving a charge running overnight that I find very unsetting. Agreed, the chance of a problem is very small. But so is the chance of my house being robbed. But yet I still lock the doors when I go to bed or out for the weekend. To me leaving a charger running on any battery when your not home or asleep is not a safe idea.

Yeah, I know there are a lot of simular devices plugged into laptops and cell phones and other things all over my house. But their something about charging a large pack overnight or while out that bothers me.

Bob

 

[dnmun]

the battery can short out at any time when the wires wear through or one of the wires is left where it can fall onto another part of the battery and short it out. this is how fires start.

there is no need to leave it charging when not around or asleep either. it should remain balanced for many cycles with regular charging.

 

[Jeremy Harris]

In most all cases I would bow to the experience and knowledge of both dogman and Jeremey. But there's something about leaving a charge running overnight that I find very unsetting. Agreed, the chance of a problem is very small. But so is the chance of my house being robbed. But yet I still lock the doors when I go to bed or out for the weekend. To me leaving a charger running on any battery when your not home or asleep is not a safe idea.

Yeah, I know there are a lot of simular devices plugged into laptops and cell phones and other things all over my house. But their something about charging a large pack overnight or while out that bothers me.

Bob

Hence one of the reasons for me saying this earlier in this thread "Best to disconnect the charger as soon as the pack is charged, in my view, both for best pack life and for safety. "

 

[dumbass]

Best to disconnect the charger as soon as the pack is charged, in my view, both for best pack life and for safety.

There's a slight degradation in life from keeping cells right at their maximum charge voltage for long periods, so if you can charge just before you use the bike that would be ideal, otherwise just turn the charger off as soon as you can after the pack is charged. If this is inconvenient, overnight charging, for example, then you could maybe fit a time switch to the charger, set to turn off a short while after you are pretty sure the pack will be fully charged.

Sorry Jeremy, I must have missunderstood this part of your posting. When I read this it sounded to me like you were endorsing overnight charging if you used a timer to turn it off at some point. My error.

Bob

 

[N!co]

When using a timer you can 'connect and forget', i like that. Now i only have to check if the charger is disconnected from mains it will not drain the battery.

 

[slafko76]

the seller told me the battery is full 1 hour after green light turns off, in my case that's 3 hours. will use timer.
i have no bms, analyzer or voltmeter, that's why i bought lifepo4 instead of lipo

so the best is to fill it from 3am till 6am just before i drive to work, or is it better to charge right after riding?
thanks for answers guys!

 

[dnmun]

why did the seller tell you that? do you believe him?

why doesn't the battery have a BMS if it is lifepo4?

you need a voltmeter for measurements and some kind of wattmeter to monitor the discharge of the battery. buy them now and use them to keep from destroying the battery and it will be cheaper in the long run.

 

[slafko76]

they offer only Cycle Analyst.
everywhere in my country (somewhere in Europe) they sell LiFePo4 without bms

 

[dumbass]

You have no BMS on the pack? Why do you think you don't have one? If you don't have a BMS you do not want to just turn on the charge and forget it (overnight or not)!! You need to have some type of BMS on that pack even if you become the BMS by manually monitoring each cell minute by minute. You must keep track of what the individual cells are doing or you WILL damage them.

Ether your seller knows there is a BMS on the pack and is why he said that or he has no idea what he is talking about. Do you have the specs on the pack? If so please post them.

Bob