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Asked — Edited

Questions About Battery 7.4Vdc 1300Mah Sold By Ez-Robot

Questions about Battery 7.4VDC 1300mAh sold by ez-robot

Does anyone have one?

How long does it take to fully change?

J


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United Kingdom
#1  
Looking at the image of the battery charger it looks like it's a 1A charger.

A 1300mAh battery will take 1.3 hours (1 hour 18 minutes) to charge at 1A.

Depending on the battery it may be able to accept faster charges. If it has a charge rate of 2c it will accept a charge of 2.6A, which would only take half an hour to charge. Some can take quite large charges which means shorter charge time.

Personally I charge my 5000mAh batteries at 800mA as I have read that slower charging is better for the battery and avoids excessive heat and is safer. However, 5000mAh batteries charged at 80mA take 6 hours 15 minutes to charge.
#2  
The Lithium chemistry batteries do not suffer from overheating. Only the NiMH and NiCD cells are damaged by heat.
United Kingdom
#3  
Lithium based batteries still get hot while charging. Mine is built in to Melvin as is the charger. A lot of heat could potentially build up inside the robot if it was getting too hot.
#4  
The only heat I've detected when charging 4400 mAH LI-ion packs inside a Roomba is coming from the charging circuits not the cells. Of course this is using a switching power supply rated at 1.25 amps.
#5  
thanks for information about charging.

So no one has one yet, I guess.

j
PRO
Canada
#6  
Hey guys

@Rich's calculations are remarkably close, it takes ~1hr 15mins to charge the ezrobot batteries from 6.6V (battery low) to fully charged with our 1A LiPo Balance Charger.
#7  
@Rich.... tsk, tsk... You're must be slipping... you're off by a full 3 minutes. I bet you Jarvis could have nailed it....:P
United Kingdom
#8  
I allowed for finding the charger and plugging it in;)

The difference comes from my calculation assuming the battery was totally dead. In the case of a LiPo this wouldn't accept a charge, but at 6.6v (3.3v per cell - personally I don't like mine going below 3.4v per cell) it isn't 100% flat, it'll still power things if you wanted to risk the battery going under voltage.
#9  
I am too chicken to let mine hit the warning buzzer... I have a tendency to top up my lithium's... Am I correct in thinking that below 3v/cell is the kiss of death for a liPo? I mean can you let them drop to 3.3v on a regular basis without worry?
United Kingdom
#10  
From what I read after under volting one of mine, there is no exact voltage. I read a few places that 3.4v per cell is recommended cut off point however I have read some people who let theirs go under 3v per cell.

Personally I don't want to waste money on another 5A LiPo so my battery monitor was set for low voltage at 3.6v on either cell, 3.5v was the second warning and 3.4v was critical. That gave it enough time to find the charging base and charge up (in theory, finding the charging station isn't something I've even started yet).

There are reports of people bringing LiPos back to life too but it involves very unsafe practice and I like my house not to be on fire, a battery is a lot cheaper than a house!
PRO
USA
#11  
I just powered my mini 6 w/turnigy 2c Lipo 1700 battery.
Am I wrong in trusting my HobyKing low voltage alarm? (3.3v)
I have given it much play time with no alarm. Still performing better then my old battery packs.
Still learning about Lipos.
Edit. Richard R , I think 3.3v will b ok.
Steve S
#12  
I believe 3.2v per cell is the value you will find in most ESCs that have the low voltage protection and in the low voltage alarms for LiPo batteries.

1.25 hours is a long time to charge a 1300mAh battery. I would guess the battery can handle better than 1A but you need to make sure you have a good charger that can detect and automatically adjust the charge rate to make sure you can do it safely.
PRO
USA
#13  
Thank you Zap,
I will let my low voltage alarm work.
I also want to see how long it will play?
Steve S
PRO
Canada
#14  
@Rich's values are quite conservative, most hobby RC companies state that 3.0V is the cutoff and 3.3V is just best practice. We defaulted to the best practice value but everyone is welcome to set the low battery warning to whatever they like in ARC we just recommend that it's 6.6V (2cells in series at 3.3V = 6.6V) or higher for 7.4V LiPos
United Kingdom
#16  
Yes I totally admit I am probably too careful with my voltages. My plan was to return to charging station and automatically charge on low power, knowing motors take a lot of energy I wanted to cover myself and know there would be no chance of dropping below the cut off point.

3.0v is fine, as Jeremie says.
PRO
USA
#17  
Thank you Rich,
That is great to know.
Steve S
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