Control of Battery Pack Performance

To achieve a high efficiency is needed to increase supply voltage. If your have a restriction on number of cells you may use a boost converter with continuous output current (our International Application WO 2006/019328 A1) to increase output voltage up to 1,6 times.

Joint patenting over the world is possible.

My Email: yikras@mail.ru

Dear Krass,

Thanks for your comments. I will contact your e-mail for commericial communication when back to office on Monday.

I suggest you look further a field for a supplier of NiMH batteries. From what I have seen you can get packs of up to 12V with a capacity of 100AH. Try the link below;

http://www.batterybook.com/

Building packs yourself is probably not a good idea, its best to go to a supplier that can do it for you but if not you can get chips that can be incorporated in the pack to monitor and correctly charge each cell. I havn't been able to find ones for NiMH cells but the following link is an example of one for LiIon cells;

http://www.master-instruments.com.au/products/58159/MIPCM-4SXP5A.html

I would be surprised if these couldn't be modified to do the same thing for NiMH cells.

The NiMH cells are going to be extremely expensive though and its probably not going to be economical to use them instead of the Pb acid cells. I am currently working on a project that requires about 100AH at 12V and the only realistic way to go is Pb Acid. Other technologies so far have been coming in between 6 and 14 times as expensive.

Dear Masu,

Thank you for your comments, it helps.

I know your mentioned NiMH. It is prismatic type and it can achieve 100AH, but yes very expensive, 12V 100AH is usd1100 (energy store 1200W hr)

What we tried are using cylinderial type, each cell 1.2V and capacity 13AH, the most far we can go is 48V26AH, it is only usd490 (energy store 1248W hr).

The problem is the former is very stable and can discharge 200A maximum, running 500 cycles, where my packing format can only discharge 30A and only lasting 80 cycles, cannot be good enough for commercial sell.

Some Indian manufacturers are doing a three wheel simple "car" that includes a driver and a back seat of 2 adults, these "car" are very cheap and no fuel required compare to real car, and very suitable for Indian market. The only problem we now face is my battery are still need improvement.

The problems you refer to above are similar to those that you get with LiIon battery packs except with LiIon packs you end up with an explosion. The solution is to use individual charger/monitor units on each cell like the one at this link;

http://www.master-instruments.com.au/related_info/PCMs%20for%20Lithium%20Ion/PCMs%20MI%20Offer%20for%20Lithium%20Ion%20and%20Lithium%20Polymer%20batteries.htm

If you could reprogram these for NiMH in stead of LiIon use it would probably mean you could use the small cylindrical cells in bank to achieve similar results as the prismatic type cells. The idea would be to have a charge monitor on each cell in the bank to protect it and balance it so it doesn't get over/under charged/discharged and fail prematurely.

Have you used diodes in parallel sets? Just checking.

They just take aprox 0.7 V drop in full load.

Joe Wojcicki - Power C

Hi Joe,

Yes our engineer use diode, but I don't know what value they use. I only know they used the wrong one and the diode burned out in last test during discharging. I will check and tell you what it value they used.

We are still trying. Thanks for comments.

Such power diods are 1) causes drop of end voltage of battery by 0.7 V as you referred, but power consumtion .7x IxI W. 2) Need big heatsinks & forced-cooling. 3)As soon as any battery drops it will not share load. This condition just starts as low as <1mV drop. Physically the best battery in system only will be on-load.

Please see my reply to the gentleman who posted:

********* Quote ************

Alternatively, we put cells in parallel to achieve 26AH or 39AH. However, its performance very bad, because each battery pack cannot be exactly same in capacity.

********* Quote Ends************

Bateries/cells are not connected in parallel as the ones which are low in voltage will start drawing current from others instead of sharing load current.

Instead larger-capacity batteries are used.

To connect power sources in parallel [Generators are normally connected in parallel & not batteries] & need special controls for equal / proportional sharing; which itself a costly & sophiticated system.

Series connection of Batteries is also not recommended but instead higher voltage batteries be selected as:

the cell/ battery which is discharged earlier will start charnging in reverse polarity so decreasing end voltage of Series-connected network.

For this "Group-Testing" of batteries/ cells is done to make make groups to be connected in series.

Diodes are connected normally in series of one of the source where dual source is used to aviod intruption in system if power-outage /brown-out,. As soon as power is out the redundent-power source takes the load instantly without intruption.

Whether the Redundant-source is is re-chageable battery or Non-chargeabl one.

Thanks to comments for all you guys.

From information I got, including your comments, I know that it is not easy to achieve it. I therefore decide don't go further for R&D in that because our company don't have enough money and man power to do so.

For the time being, we will only concentrate on less power battery pack, such as 36V 13AH. We manufactured these for long and knowing that this packing is very stable and compact, suitable for electric bicycle application, power up to 500W.

I will let the Indian partner to do higher power e-vehicle research as they have more man power to do so.

If you are interested in the update information, please inform me (my e-mail sanforce@gmail.com) and I will e-mail to you for the test result - their test result will come out about one week's later.

********* Quote ************

Alternatively, we put cells in parallel to achieve 26AH or 39AH. However, its performance very bad, because each battery pack cannot be exactly same in capacity.

********* Quote Ends************

Bateries/cells are not connected in parallel as the ones which are low in voltage will start drawing current from others instead of sharing load current.

Instead larger-capacity batteries are used.

To connect power sources in parallel [Generators are normally connected in parallel & not batteries] & need special controls for equal / proportional sharing; which itself a costly & sophiticated system.

Series connection of Batteries is also not recommended but instead higher voltage batteries be selected as:

the cell/ battery which is discharged earlier will start charnging in reverse polarity so decreasing end voltage of Series-connected network.

For this "Group-Testing" of batteries/ cells is done to make make groups to be connected in series.