Questions on NiMH Batteries

[Dan Marotta]

I'm considering replacing the lead-acid tail battery in my LAK-17a with
NiMH batteries. I find D cells rated at 1.2v 10 Ah which would be ideal
to build up a 12v 10 Ah pack. I've already checked fitment in the
sealed battery box using alkaline D cells.

Can anyone tell me if these batteries are actually 1.2v. If so, I'd
need to use 11 or 12 of them to get the voltage I want.
--
Dan Marotta

[Andrzej Kobus]

On Wednesday, February 25, 2015 at 6:51:09 PM UTC-5, Dan Marotta wrote:
> I'm considering replacing the lead-acid tail battery in my LAK-17a
> with NiMH batteries.* I find D cells rated at 1.2v 10 Ah which would
> be ideal to build up a 12v 10 Ah pack.* I've already checked fitment
> in the sealed battery box using alkaline D cells.
>
>
>
> Can anyone tell me if these batteries are actually 1.2v.* If so, I'd
> need to use 11 or 12 of them to get the voltage I want.
>
>
> --
>
> Dan Marotta

Dan, NiMH are a really bad choice. I know someone whose battery in a glider got really hot to the point of melting fiber glass. These batteries were put in by a glider manufacturer and properly sized.

If you want more information contact me directly.

[Dan Marotta]

PM sent.


On 2/25/2015 4:58 PM, Andrzej Kobus wrote:
> On Wednesday, February 25, 2015 at 6:51:09 PM UTC-5, Dan Marotta wrote:
>> I'm considering replacing the lead-acid tail battery in my LAK-17a
>> with NiMH batteries. I find D cells rated at 1.2v 10 Ah which would
>> be ideal to build up a 12v 10 Ah pack. I've already checked fitment
>> in the sealed battery box using alkaline D cells.
>>
>>
>>
>> Can anyone tell me if these batteries are actually 1.2v. If so, I'd
>> need to use 11 or 12 of them to get the voltage I want.
>>
>>
>> --
>>
>> Dan Marotta
> Dan, NiMH are a really bad choice. I know someone whose battery in a glider got really hot to the point of melting fiber glass. These batteries were put in by a glider manufacturer and properly sized.
>
> If you want more information contact me directly.

--
Dan Marotta

[Darryl Ramm]

On Wednesday, February 25, 2015 at 3:51:09 PM UTC-8, Dan Marotta wrote:
> I'm considering replacing the lead-acid tail battery in my LAK-17a
> with NiMH batteries.* I find D cells rated at 1.2v 10 Ah which would
> be ideal to build up a 12v 10 Ah pack.* I've already checked fitment
> in the sealed battery box using alkaline D cells.
>
>
>
> Can anyone tell me if these batteries are actually 1.2v.* If so, I'd
> need to use 11 or 12 of them to get the voltage I want.
>
>
> --
>
> Dan Marotta

Bad choice: compared to other options the have poor energy density, poor charge performance, can represent a higher fire hazard, require a specific type charger. You should not try to fast charge a NiMh pack in an enclosed space, especially without a thermal monitoring charger/cutoff. There is just much better battery technology available. Especially LiFePO2 batteries.

I am also aware of a glider NiMh battery with serious thermal damage caused by improper charging/insufficient manufacturer warnings, etc.

[bumper[_4_]]

On Wednesday, February 25, 2015 at 5:56:19 PM UTC-8, Darryl Ramm wrote:
There is just much better battery technology available. Especially LiFePO2 batteries.
>
> I am also aware of a glider NiMh battery with serious thermal damage caused by improper charging/insufficient manufacturer warnings, etc.

Darryl,

Did you mean LiFePO4?

Likewise, familiar with the glider that had issues with NiMH batteries. Besides the NiMH relatively high self-discharge rate, when using multiple batteries is keeping things balanced. This is exacerbated if the batteries are not all in the same location, as differing lengths and thus resistance of interconnect wire is enough to pretty much insure things will not go well, with some cells overcharging, deep discharging, or even reversing cell polarity.

bumper

[Darryl Ramm]

On Wednesday, February 25, 2015 at 9:44:52 PM UTC-8, bumper wrote:
> On Wednesday, February 25, 2015 at 5:56:19 PM UTC-8, Darryl Ramm wrote:
> There is just much better battery technology available. Especially LiFePO2 batteries.
> >
> > I am also aware of a glider NiMh battery with serious thermal damage caused by improper charging/insufficient manufacturer warnings, etc.
>
> Darryl,
>
> Did you mean LiFePO4?
>
> Likewise, familiar with the glider that had issues with NiMH batteries. Besides the NiMH relatively high self-discharge rate, when using multiple batteries is keeping things balanced. This is exacerbated if the batteries are not all in the same location, as differing lengths and thus resistance of interconnect wire is enough to pretty much insure things will not go well, with some cells overcharging, deep discharging, or even reversing cell polarity.
>
> bumper

Uh yes, LiFePO4. But if anybody can find a LiFePO2 battery call me.

[Pierre Vav]

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.

[Papa3[_2_]]

> bumper

On Thursday, February 26, 2015 at 12:44:52 AM UTC-5, bumper wrote:

>
> Darryl,
>
> Did you mean LiFePO4?
>

PO2/PO4, 220/221, "whatever it takes"

www.youtube.com/watch?v=iX3kxAA2L4Q

[Dan Marotta]

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 are:

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 are:

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

[Pierre Vav]

If you find something compliant, please keep us informed.

[Per Carlin]

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.

[Dan Marotta]

It looks like this will fit the bill for me:
*http://www.bioennopower.com/products/12v-12ah-lfp-battery-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 are:
>
> 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 are:
>
> 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

[Charlie M. (UH & 002 owner/pilot)]

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/12v-12ah-lfp-battery-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 are:
>
>
>
> 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 are:
>
>
>
> 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]

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/12v-12ah-lfp-battery-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 are:
>>
>>
>>
>> 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 are:
>>
>>
>>
>> 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

[Papa3[_2_]]

On Thursday, February 26, 2015 at 5:23:56 PM UTC-5, Dan Marotta wrote:
> 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.
>

I like these shot bags. Mix-n-match to get the weight that you want. Easy to swap out if you have someone heavier flying the ship.

http://amzn.com/B0034ZECX4

[Charlie M. (UH & 002 owner/pilot)]

On Thursday, February 26, 2015 at 5:23:56 PM UTC-5, Dan Marotta wrote:
> 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/12v-12ah-lfp-battery-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 are:
>
>
>
> 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 are:
>
>
>
> 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

NP, glad to add something worthwhile.
;-)

[Dan Marotta]

Been shopping for lead for the past couple of hours and finally settled
on lead ingots. I've ordered 10 pounds and, if they don't simply slip
into the battery box, they can be easily cut to fit. I'll be replacing 6
lb of batteries and moving the dry CG aft from 73% to 79%. I have
enough capacity in the tail ballast tank to move it further aft as I like.

The shot bags looked nice, but their form factor would not fit into the
box which is very long and thin. I also considered lead shot which
would have required me to line the battery box with aluminum foil and/or
plastic wrap, pour in the shot, and then pour in epoxy to stabilize the
load. The walls of the battery box are thin fiberglass and I would not
have wanted any flexing to release shot into the lower fin area.

All's well now - just waiting for Christmas to arrive!

On 2/26/2015 8:22 PM, Charlie M. (UH & 002 owner/pilot) wrote:
> On Thursday, February 26, 2015 at 5:23:56 PM UTC-5, Dan Marotta wrote:
>> 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/12v-12ah-lfp-battery-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 are:
>>
>>
>>
>> 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 are:
>>
>>
>>
>> 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
> NP, glad to add something worthwhile.
> ;-)

--
Dan Marotta

[MNLou]

Hey Dan -

Why not just use water for tail ballast and not have so much weight up high? Possibly a freezing problem at altitude?

[Charlie M. (UH & 002 owner/pilot)]

On Saturday, February 28, 2015 at 6:10:30 PM UTC-5, MNLou wrote:
> Hey Dan -
>
> Why not just use water for tail ballast and not have so much weight up high? Possibly a freezing problem at altitude?

Water can be good to offset the balance when dumping wing ballast..... If he is looking at "static balance" (my choice of words).... he is looking at fixed ballast for the "normal pilot" (normal is a relative term here.... if you're a pilot, lots of peeps think we're abnormal.... sigh).
Tail water ballast can be useful when dumping wing water ballast creates a CG issue.

Just my $0.02US........

[Dan Marotta]

Exactly right, Charlie!

I've chosen to add an extra 4 lb of lead to the tail battery box
because, with dry wings and tail, my current CG is at 71% aft and that
requires most of my aft trim capability, full aft trim for thermalling
below about 50 KIAS. The extra 4 lb moves the CG back to 79% aft which
should give me one or two notches on the trimmer and should be just fine
during the winter months. In the summer, I can supplement the tail
weight with the tail tank to move the CG back into the 90s. According
to my W&B spreadsheet, I can trim to 92% aft at gross weight. That
satisfies me.

On 2/28/2015 4:41 PM, Charlie M. (UH & 002 owner/pilot) wrote:
> On Saturday, February 28, 2015 at 6:10:30 PM UTC-5, MNLou wrote:
>> Hey Dan -
>>
>> Why not just use water for tail ballast and not have so much weight up high? Possibly a freezing problem at altitude?
> Water can be good to offset the balance when dumping wing ballast..... If he is looking at "static balance" (my choice of words).... he is looking at fixed ballast for the "normal pilot" (normal is a relative term here.... if you're a pilot, lots of peeps think we're abnormal.... sigh).
> Tail water ballast can be useful when dumping wing water ballast creates a CG issue.
>
> Just my $0.02US........

--
Dan Marotta

[Surge]

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

[Martin Gregorie[_5_]]

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 |

[Nick[_5_]]

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