LifePo4 newby quetions

is it good to just let my ping 48v15ah LifePo4 battery charge for days at a time? i am using the free charger that came w/ the battery.

how should i store my battery during winter (no riding) months? should i just charge it all the way then leave it until spring? or should i keep it pluged up to the charger?

if i keep the battery on the charger for days will it use up the amount of time i can charge/ discharge my battery?

Lotsa discussion on that one. There is how it should be, like how a single cell would act, and then there is what actually happens with a pack connected to a bms.

One of the things coming out is a few have had a bms left connected drain the cell group that powers the bms, causing failure of those cells. So for long term storage, disconnecting the bms seems to be a good idea.

The theory says, store the battery not completely charged. But I'd be inclined to charge it up all the way and unplug the bms. Check on it monthly, and charge it back up. Dogman logic says that keeping it fully charged all summer while using it couldn't be any worse than storing it charged in the winter. Dogman is't worrried about shelf life though, since I ride 4000 miles a year or more. I'll wear it out long before it dies of age.

In use, I leave my ping charging all the time, basicly because I cycle it twice a day, but if I don't ride to work, I unplug it in the morning. It won't boil away the battery like a dumb wet cell lead battery charger.

you don't have to leave it on the charger, but you should put it on the charger every month or 2. the BMS will drain the battery dead if you leave it for long periods without charging. you can unplug the sense wire plug from the battery at the BMS and the BMS won't discharge the battery then but you need it to charge, and you only have the self discharge which is very low in lifepo4, but just charge a little every month or so is easiest. it's best to keep riding through the winter.

Yeah, bundle up and ride once a month just a mile or so, then recharge would do it.

Here are some numbers from http://en.wikibooks.org/wiki/Battery_Power/Lithium_Ion_Batteries

At a 100% charge level, a typical Li-ion laptop battery that is full most of the time at 25 degrees Celsius or 77 degrees Fahrenheit, will irreversibly lose approximately 20% capacity per year. However a battery stored inside a poorly ventilated laptop, may be subject to a prolonged exposure to much higher temperatures than 25 °C, which will significantly shorten its life. The capacity loss begins from the time the battery was manufactured, and occurs even when the battery is unused. Different storage temperatures produce different loss results: 6% loss at 0 °C/32 °F, 20% at 25 °C/77 °F, and 35% at 40 °C/104 °F. When stored at 40% charge level, these figures are reduced to 2%, 4%, 15% at 0, 25 and 40 degrees Celsius respectively.

Click to expand...

Don't know how applicable for LiFePO4. but it suggests the charge state is more important at room temperature and below, with 3-5 times the capacity loss for full charge compared to half charge.

dak664 said:

Here are some numbers from http://en.wikibooks.org/wiki/Battery_Power/Lithium_Ion_Batteries

At a 100% charge level, a typical Li-ion laptop battery that is full most of the time at 25 degrees Celsius or 77 degrees Fahrenheit, will irreversibly lose approximately 20% capacity per year. However a battery stored inside a poorly ventilated laptop, may be subject to a prolonged exposure to much higher temperatures than 25 °C, which will significantly shorten its life. The capacity loss begins from the time the battery was manufactured, and occurs even when the battery is unused. Different storage temperatures produce different loss results: 6% loss at 0 °C/32 °F, 20% at 25 °C/77 °F, and 35% at 40 °C/104 °F. When stored at 40% charge level, these figures are reduced to 2%, 4%, 15% at 0, 25 and 40 degrees Celsius respectively.

Click to expand...

Don't know how applicable for LiFePO4. but it suggests the charge state is more important at room temperature and below, with 3-5 times the capacity loss for full charge compared to half charge.

Click to expand...

This only applies to Li-Co lithium ion batteries. It does not apply to LiFePO4 which is far more thermally stable.