# Battery charging question

If 50% charge is the ideal state of battery equilibrium and charging less than 100% allows many more recharge cycles - then wouldn’t it be ideal to ride down to 25% and charge up to 75%? Obviously if you have a long ride planned then fully charge and down to the min set by the vesc. But for every day 15-30 min rides would the above regimen be better?

According to Leo Leporte " the tech guy" The life of a lithium battery is determined by a certain number of full charge cycles. If you do a partial charge, it counts as only a percentage of that full charge cycle. So if your battery is good for say 500 full charge cycles and you charge it to 75% full and discharge it to 25% or charge it to 100% full and discharge it to 50%.( I believe it is better to use the 100% to 50%) Then your only using up 1/2 of a charge cycle each time you charge/discharge your battery. So doing this, you will be able to charge said battery 1000 times before wearing it out. The problem I find with this practice is that because you are effectively reducing your battery’s range, you will have to charge your battery more often. So have you really lengthened the life of your battery? In my opinion, no. But by charging to 100% and discharging only 50% will keep you safely away from an over discharge situation. My experience has been that charging a battery to 100% appears to have no adverse affect on the battery where as discharging the battery too low has immediate adverse effects on the battery. Granted that there can be other factors which may affect the health and life of a battery like trying to draw more current than the battery can handle and causing it to overheat. http://techguylabs.com/episodes/1022/how-can-i-make-my-batteries-last-longer

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You are right. That would be better for the cells. But you have to realize that 300 full cycles on a 10S4P battery pack would be more than 10000 km. In worst conditions the battery should be good for at least these 300 cycles. But in reality it will be fine with more cycles because when we ride we are not even close to worst conditions. (As long as your settings are in the battery limits). And i don’t think that there are many out there who did already 10000 km on one longboard battery pack. So you can safe some recharge cycles but i would recommend to not care about and just have fun. In the winter when you don’t use it for a couple of weeks or months then you should bring the voltage down to 3.75V a cell. But otherwise it doesn’t hurt that much. Just simply only charge the board when you know you ride the board that day or the next day.

One thing that I have noticed is that when Lithium cells are tested, they are allowed to rest between charging and discharging and I believe that this is a good practice when possible. Something like 30 min after discharge and before re-charging. And 15min after charging and before discharging.

I think that’s only because of the temperature. But we don’t use the cells contentiously with the maximum continuous discharge rate. To be honest, with quality high current discharge cells we only raise the temperature a little bit. So this is also something we don’t need to worry about. If you want to do your cells something good then charge them with a low current. This takes longer but your cells like it.

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Good point, slow charging is the best way. Although I think charging at 1C is safe for the most part.

1 C is already very high. For a 10S4P pack with 2500 mah cells this would be 10A. Most fast chargers have only 4A (0.4C). Best of course is a adjustable charger for current and voltage. A really nice 12S charger is the Graupner Ultramat 18. The build in power supply works with 100 watts. But with a external power supply you can use 300 watts. But i always charge my cells slowly so the 100 watts is enough. For my 1 kwh battery i need more than 10 hours but i simply leave it on over night. It also interrupts the charging every minute for a couple of seconds which is also good for the battery.

I charge my Lipo packs at 1C but it’s only 5a and they’re rated for 5C. I use a lab power supply with adjustable voltage and current up to 60v 5a with CC and CV. IT works great as a charger and won’t over charge.

http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

Look at tables 2 and 4. That tells the whole story. By discharging only to 80% and charging fully, you get a 33% increase in life cycles. By charging only to 80% and discharging fully, you get a 200% increase in life cycles.

Lithium Ion cells don’t like being fully charged regardless of what others say. Battery University is a great place to learn and has tons of citations to academic research papers with real good stuff if you’re looking to get really informed.

It also says this initially in that article: “The smaller the discharge (low DoD), the longer the battery will last. If at all possible, avoid full discharges and charge the battery more often between uses. Partial discharge on Li-ion is fine. There is no memory and the battery does not need periodic full discharge cycle” Base on this I came up with my recommendation of 75-25 use zone.

I’d say that it’s more beneficial to charge to 65% and discharge to 15% but there is no data to support that. Charging to 75% and discharging to 25% is really good though!

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It seems like when I go from 100-50 the battery goes on forever. Yesterday 18 miles. Then from 50-25 only another 3-4 miles. At 25 starts slowing down and acts funky.

Which battery??

12s4p lithium ion cells. Kali built it!

Do you know what cells were used?? @Kaly

@Wschles yeah that doesn’t sound good. You should be seeing more of a flat/linear drain between 90% and 20% than that.

The cell use are Samsung 25R The pack is a 12S-6P

On The battery indicator this is an estimate reading since that pack does not have a coulomb meter installed.

the LED indicator have 5 leds the last red dot indicates empty. And the behavior is the soft cutoff voltage setting from the VESC.

The setting can be change but I think 18 miles + 3-4 miles to depletion is pretty good for a eMTB.

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What are the ESC settings right now? I agree with @longhairedboy that it should be more linear than that but it highly depends on how much power he’s drawing. 25Rs are not great in delivering high amounts of current as voltage sag takes a toll on them specially past the 50% mark, this combined with high cutoff voltage can be cutting his range significantly but again it’s all highly dependent on how much power he draws.

And as @Kaly said, the percentage meter is only an estimate based on voltage. So while the board shows 50% at no load, under load it could dip below 20%.

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The issue here may be the LED indicator. The one I use on my packs are the push button type with 5 LEDS that represents a range of voltage, which in turn this voltage represent an estimate of the capacity, one red led is for empty, the remaining 4 leds each represents a 25% range in voltage this is good to estimate on what range of the discharge curve you are. But not to properly track a discharge curve.

@PXSS A graphic is worth 1000 words

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