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M600 Battery Capacity Issues

EEx

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Oct 19, 2021
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Hello all,

I am experiencing pretty significant battery capacity drops from our TB48's and TB47's. We have quite a few batteries that are at approximately 150 charge cycles and are now only charging to half the original battery capacity... Has anyone else experienced anything like this before? And does anyone have any advice on how to maintain our batteries (besides what DJI recommends) to avoid this from happening? At this point I have contacted DJI and they will most likely replace the batteries as they are still under warranty, but I would like to know how to avoid this in the future. Any help of advice would be appreciated. Thanks!
 
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Hello, I found that our batteries go to half life after about 120 cycles. This is mainly because the BMS inside the battery is balancing the cells only while charging which is not how a lipo should be maintained.
The standard procedure for full discharge and then full charge do not balance the cells while at their minimal voltage so it is half of what should be done.
So first I'm discharging the battery until it shuts down itself then I open the battery top, disconnect DJI's balance cable and desolder the main leads. Next step is to solder 6s balance wires to the cells as well XT60 connector to the mains so to make it like ordinary lipo without BMS and then I do 2-3 full cycles at 1C including cell balance in both, charging and discharging using standard lipo charger, I use iCharge380 duo. This tedious procedure fixes the overall capacity of the battery and results in less internal resistance between individual cells. We found this while experimenting with our inspire's batteries and it is the same for m600.
Finally discharge the modified battery to 3.2v per cell, desolder balance and main wires, solder original main wires and connect DJI's balancing cable and charge with dji charger. That's what I do :)
 
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I follow a similar path... maybe a bit less tedious.
I've kept the I1's batteries & M600Pro batteries functional using similar practice.
Tired cutting a I2 / M210 TB50 for similar maintenance but that wasn't productive.
This routine Works Great for 48 & 47 batteries, recovers many that indicated fail or poor.

I had made 2 custom leads... using older dead battery mini-balance connector (donated by Forum members) using the circuit board's mini balance connector and other end attached standard balance lead cable ( I think if I recall, you flipped the leads?... I'd have to look again.

From this point going forward... when needed, I pop the top of battery.
Unplug balance lead and connect my custom balance lead. Using alligator to banana clips attached to my iCharge banana leads, connect the Pos & Neg blades inside cap to iCharger and my custom balance lead to iCharger balance boards. Perform a few maintenance cycles: Discharge down near minimal voltage to help start the balance, Very Low amp charge to about mid-point (60-70%), discharge again (balance begins to improve now), repeat this 1-3 times to get balance close, then perform full charge on iCharger.

This normally restores battery condition to normal charge and operation.
Note: On batteries I've performed this balance routine, going forward... I will often on leisure time, hover above LZ until batteries are in the low 8-13% range, then land and spin motors til 4-9%, then stop motors and allow system to pull batteries gently down future. Notice, when on skids, not hovering, no load, LiPO Batteries will regain surface charge.

Damage can be 2 Fold on LiPo's... if heavy amp draw (flight or hover) rapid discharge can "dip" too quickly increasing discharge heat, then with rapid Recharge can keep gel heated to point of damage: increase decay and increase IR factor. If brought down to gentle hover, monitor battery cells... watch the lowest cell. Land and allow it to continue to discharge under No Load... a no load discharge will pull more from a higher percentage cell than the lower.
Always allow the batteries to cool Gel internally (30-60 minutes) before Recharging... requires several sets of batteries.
 
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