[blastexx]

My eken m001 now has a 3600 mAh battery and it still has it's orginal housing !I placed a second 7.4V 1800 mAh battery in parallel with the internal battery inside the eken m001 and it works ! The batteries i used are identical to eachother and i first fully charged them both seperately.I am now testing the battery performance, the only downside is that it is a very very tight fit (actually it bends the case somewhat

). The battery is placed under the motherboard.Here are some pics:

 

[metal03326]

Where did you got the second battery?

 

[blastexx]

I got the battery from ebay:Replacement Battery For EKEN MID M001 M002 Tablet PC - eBay (item 200488443962 end time Jul-26-10 21:18:50 PDT)

 

[blastexx]

OK, i have measured the total battery time with wifi off and it is a whopping 6 to 6,5 hours!The next time i will measure it with the wifi on, but i think it will be about 4 to 5 hours.Charging the battery right now

 

[blastexx]

The battery fully charged in 3 hours. It's safe to say that the battery mod works

 

[enotar]

Interesting but I repeat putting in // is dangerous as one set of battery can discharge in the other if these are not well balanced.I personally took the step to buy 2 3500mah of 3.7 and set in serial but I had to set a small box on the back of the Eken like Carnivore.I get 6 hours battery life

 

[blastexx]

both of the batteries have a balancing board, so my guess is that this will protect the batteries from overcharge/discharge.I have seen multiple website about battery mods for laptops and they have even put 3 battery packs together in parallel.If my eken starts to fizzle i will let you know But by the looks of it, it is working fine.I don't feel extra heat or hear strange sounds coming from the batteries.I think the most important thing is to first fully charge them separately before you put them together.

 

[vtpad]

They should be balance charged. In other words, each cell should be charged individually and monitored individually while charging. You can buy balance chargers at RC forum advertisers. I wouldn't leave the room when the are charging.Two other concerns -- if under the PC board and under pressure already, the solder leads could puncture the cells -- they can swell if overcharged. Perhaps you put a hard spacer under the PC board -- that would be better. Also, lipos can heat up quite a bit. Sandwiching them in tightly will trap that heat, plus there are more batteries to heat up. And there's less air space for the cells and the PC board ICs for cooling.Not saying it won't give long service, but all of these things increase risk.

 

[blastexx]

There are no solder leads under the motherboard, i checked that.I charged the batteries with an open case and the batteries did not heat up extremely, but your right about the cooling. If i could just find another spot for the extra battery, but there is just no room elsewhere in the Eken Besides, all mods are increased risks, that's why modders do it. You could fry your machine or you can make it better

 

[vtpad]

[quote name='blastexx;29392]If my eken starts to fizzle i will let you know But by the looks of it' date=' it is working fine.I don't feel extra heat or hear strange sounds coming from the batteries.I think the most important thing is to first fully charge them separately before you put them together.[/QUOTE']This guy let people know, which I think is a good thing. But better to be aware of the risks. Definitely be present in the room when you are charging your rig:Lipo fire took my house and everything I own - RC Groups

 

[blastexx]

I think it is pretty safe.The battery pack consists of 2x 3.7v cells in series connected to a balancing board.The charge voltage is 9v, this goes to both batteries.So the batteries cannot overcharge because they both have their own balancing boards present.If one battery fails (due to overcharging) it will switch off and the other one will take over.The guy in the article charged the lipo battery WITHOUT a balancing board, this is indeed not wise!

 

[vtpad]

There are many more fire posts on RC forums which didn't involve the same cause I listed a few in another thread and don't want to belabor the point again, so those interested can look it up. @blastexx, I agree with you about the balance boards if they also have under voltage cutoff and other smart safety cutoff circuitry -- they probably do if they are typical of the latest boards.My own worry would be the tight fit and possible cell swelling. But yours may be fine. As you said, keep us posted on any problems.

 

[blastexx]

Battery pack cells are balanced when all the cells in the battery pack meet two conditions:If all cells have the same capacity, then they are balanced when they have the same relative state of charge (SOC.) In this case, the open circuit voltage (OCV) is a good measure of the SOC. If, in an out-of-balance pack, all cells can be differentially charged to full capacity (balanced), then they will subsequently cycle normally without any additional adjustments. If the cells have different capacities, they are also considered balanced when the SOC is the same. But, since SOC is a relative measure, the absolute amount of capacity for each cell is different. To keep the cells with different capacities at the same SOC, cell balancing must provide differential amounts of current to cells in the series string during both charge and discharge on every cycle.

 

[metal03326]

...or you can make a special place with limited oxygen to charge your Eken there

 

[blastexx]

Update:My eken is going strong, no overheating and no fire of any kind am i the only one who tried a parallel battery mod?

 

[enotar]

I am ready to try this WE but I have installed 2 3.7v 3500mah in serial and just uninstall the stock battery.I am a little preocupied about the capacity diference 3500 and 1800 in parallel.I know if these are fully charge prior conecting everything should run smooth but what abpout the 1800mah discahrging completely before the 3500 ?I think I should try or maybe I just buy a 10,000 mah 7.4 volts.I let you know on monday if I took the jump.

 

[vtpad]

[quote name='blastexx;29781]Battery pack cells are balanced when all the cells in the battery pack meet two [URL=conditions:If]conditions:If[/URL] all cells have the same capacity' date=' then they are balanced when they have the same relative state of charge (SOC.) In this case, the open circuit voltage (OCV) is a good measure of the SOC. If, in an out-of-balance pack, all cells can be differentially charged to full capacity (balanced), then they will subsequently cycle normally without any additional adjustments. If the cells have different capacities, they are also considered balanced when the SOC is the same. But, since SOC is a relative measure, the absolute amount of capacity for each cell is different. To keep the cells with different capacities at the same SOC, cell balancing must provide differential amounts of current to cells in the series string during both charge and discharge on every cycle.[/QUOTE'] source: Wikipedia.Also of interest re. Lipo protection, both circuitry and physical: over discharge, cell swelling, cell puncture, overheating. Also re the Eken's charger: output capacity relative to charge rate and power-on board draw.

 

[enotar]

[quote name='vtpad;30363]source: Wikipedia.Also of interest re. Lipo protection' date=' both circuitry and physical: over discharge, cell swelling, cell puncture, overheating. Also re the Eken's charger: output capacity relative to charge rate and power-on board draw.[/QUOTE']Looks complex!

 

[blastexx]

source: Wikipedia.Also of interest re. Lipo protection, both circuitry and physical: over discharge, cell swelling, cell puncture, overheating. Also re the Eken's charger: output capacity relative to charge rate and power-on board draw.

Complex indeed

 

[blastexx]

@enotar: where did you buy the two 3500 mAh batteries? i would like to have those too !