Questions on NiMH Batteries

On Thursday, February 26, 2015 at 4:06:54 PM UTC-5, Dan Marotta wrote:
It looks like this will fit the bill for me:* http://www.bioennopower.com/products...ery-pvc-pack.*
It's a 12v 12 Ah soft pack with BMC and charger.* It appears it will
slide right into my tig welded covered aluminum box where it will be
padded with foam and secure from any stresses.



It will be a simple matter to pull it out and take it home for
charging.* I'll simply reload the (mostly) dead lead batteries back
into the tail box for weight and balance purposes.* They won't be
connected any more.




On 2/26/2015 10:13 AM, Dan Marotta
wrote:




Thanks to all.



It looks like NiMH batteries are out of the question for me.* I
have a 10 Ah LiFePO4 drop-in replacement as my main battery and am
very happy with its performance.* I'm looking for LiFePO4 cells
(and BMS) for protection that can fit in my tail battery box.* The
dimensions of the drop-in box a



Length = 58 cm

Width = 3.5 cm

Height = 6.5 cm



No luck so far, but I'm continuing the search.* I could also build
up a pack for a separate box which I've installed behind the seat
back.* Its dimensions a



Length = 36 cm

Width = 4.8 cm

Height = 10.8 cm



Any suggestions would be most welcome.* I've been searching the
net, but nothing yet satisfies my specific needs.



Dan




On 2/26/2015 8:16 AM, Pierre Vav
wrote:



Hi,

I have a pack of 11 9ah Nimh 1,2 v as a backup battery in the tail of my Lak17.
They have the same format as alkaline D cells.
I use a RC charger that automatically detects the right number of elements.
At end of charge, voltage is arount 16,2 volts, but drops quickly to under 16. Also cable length drops voltage to something usable by instruments (15v).

As it is a backup battery, I use it after the main 9ah pb is lowered down, so voltage is ok.

I never had any problems with these batteries. But they are old now, and i plan to replace them with lifepo4.
also nimh auto discharge force me to derig the tail very often. With Lifepo4, If I do not use the backup, no need to derig.







--

Dan Marotta




--

Dan Marotta

Hi Dan,

Even if you're only using the old LA batteries for ballast (in the tail)..... I would NOT recommend it.
LA (Lead Acid) batteries will suffer from "plate sulfation", basically the "battery form of rust". This causes the battery plates to swell, sometimes a LOT. This can cause the pack to wedge itself into a fixed compartment as well as crack the case letting out the small amount of electrolyte contained within to go "where ever it wants" (basically down.... attacking anything,like steel..... "control cables/rods anyone?").

Take this info from an "Ex UPS battery monitoring person" with ~15 years in the industry. I have seen batteries explode/crack cases more than once.

You want weight, get lead bricks, please DON'T use old LA batteries..........

UmmmmK?!
;-)

Thanks for that great advice, Charlie! I will find lead bricks or shot
which I can load into the box. Bricks or sheet will be better, of course.

On 2/26/2015 2:34 PM, Charlie M. (UH & 002 owner/pilot) wrote:
On Thursday, February 26, 2015 at 4:06:54 PM UTC-5, Dan Marotta wrote:
It looks like this will fit the bill for me: http://www.bioennopower.com/products...ttery-pvc-pack.
It's a 12v 12 Ah soft pack with BMC and charger. It appears it will
slide right into my tig welded covered aluminum box where it will be
padded with foam and secure from any stresses.



It will be a simple matter to pull it out and take it home for
charging. I'll simply reload the (mostly) dead lead batteries back
into the tail box for weight and balance purposes. They won't be
connected any more.




On 2/26/2015 10:13 AM, Dan Marotta
wrote:




Thanks to all.



It looks like NiMH batteries are out of the question for me. I
have a 10 Ah LiFePO4 drop-in replacement as my main battery and am
very happy with its performance. I'm looking for LiFePO4 cells
(and BMS) for protection that can fit in my tail battery box. The
dimensions of the drop-in box a



Length = 58 cm

Width = 3.5 cm

Height = 6.5 cm



No luck so far, but I'm continuing the search. I could also build
up a pack for a separate box which I've installed behind the seat
back. Its dimensions a



Length = 36 cm

Width = 4.8 cm

Height = 10.8 cm



Any suggestions would be most welcome. I've been searching the
net, but nothing yet satisfies my specific needs.



Dan




On 2/26/2015 8:16 AM, Pierre Vav
wrote:



Hi,

I have a pack of 11 9ah Nimh 1,2 v as a backup battery in the tail of my Lak17.
They have the same format as alkaline D cells.
I use a RC charger that automatically detects the right number of elements.
At end of charge, voltage is arount 16,2 volts, but drops quickly to under 16. Also cable length drops voltage to something usable by instruments (15v).

As it is a backup battery, I use it after the main 9ah pb is lowered down, so voltage is ok.

I never had any problems with these batteries. But they are old now, and i plan to replace them with lifepo4.
also nimh auto discharge force me to derig the tail very often. With Lifepo4, If I do not use the backup, no need to derig.







--

Dan Marotta




--

Dan Marotta
Hi Dan,

Even if you're only using the old LA batteries for ballast (in the tail).... I would NOT recommend it.
LA (Lead Acid) batteries will suffer from "plate sulfation", basically the "battery form of rust". This causes the battery plates to swell, sometimes a LOT. This can cause the pack to wedge itself into a fixed compartment as well as crack the case letting out the small amount of electrolyte contained within to go "where ever it wants" (basically down.... attacking anything,like steel..... "control cables/rods anyone?").

Take this info from an "Ex UPS battery monitoring person" with ~15 years in the industry. I have seen batteries explode/crack cases more than once.

You want weight, get lead bricks, please DON'T use old LA batteries.........

UmmmmK?!
;-)

--
Dan Marotta

If you find something compliant, please keep us informed.

If you need a LiFePo4 pack with odd dimmension, take a look at you local hobby store. Often called LiFe, the range in size are from matchstickbkx (700mAh) to larger 10000mAh+. You need pack with 4 cells in serie.

Aluminium-ion batteries look promising after the latest break through by Stanford University scientists.
If this makes it to the market it could be a game changer.

Their aluminium-ion battery can be:
- Charged very quickly (around one minute)
- Handle 7500 charge cycles with no loss of capacity
- Can be destroyed/damaged with no risk of fire

http://news.stanford.edu/news/2015/m...ry-033115.html

On Wed, 08 Apr 2015 01:22:29 -0700, Surge wrote:

Aluminium-ion batteries look promising after the latest break through by
Stanford University scientists.
If this makes it to the market it could be a game changer.

Their aluminium-ion battery can be:
- Charged very quickly (around one minute)
- Handle 7500 charge cycles with no loss of capacity - Can be
destroyed/damaged with no risk of fire

http://news.stanford.edu/news/2015/march/aluminum-ion-
battery-033115.html

However, as others pointed out yesterday when this was reported in The
Register, notice that there's nothing mentioned about its capacity or
energy density. This is odd as these are two of the things that usually
get hyped when a new battery chemistry is developed.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

http://en.wikipedia.org/wiki/Aluminium-ion_battery has more info.
Current energy density is much lower, and voltage lower.