Questions on NiMH Batteries

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

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.

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

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.

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

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.

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.

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

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

If you find something compliant, please keep us informed.