SLA batteries opinions?

On Monday, April 2, 2018 at 10:47:02 PM UTC-7, krasw wrote:
tiistai 3. huhtikuuta 2018 2.16.45 UTC+3 kirjoitti:
The theoretical number of times the batteries of each type can be cycled is irrelevant if they will die of old age in a number of years, even if that's 10+ years for LiFePO4 and only 3-4 years for SLA in my use.


In my experience lifetime of LFP is not better than SLA. My first battery died completely in 6 months, second had much reduced capacity after 2 seasons. Idea that chinese LFPs last thousand cycles or decade is just false.

In my experience LFP batteries are much better than SLA and deliver close to the label AH for many cycles. And if you drop them on your foot is does not hurt as bad.

Richard

Richard

I have flown with both an LFP and SLA battery in my ship for 5 years. I alternate which one is primary and which one is secondary on each flight. A PowerSonic 12V14Ah SLA vs Powerizer 12V15Ah LFP. With all my instruments running the SLA voltage drops below the minimum requirements of my radio by 5 hours. My LFP has never failed to power everything up to a 7 hour flight.. The SLA gets replaced after 3 years. My LFP is six years old and still working perfectly.

When I fly in very cold conditions (0C) the SLA is usually not driving my radio by three hours. Again, the LFP has run up to six hours without any significant voltage drop.

Would you use any of the lithium batteries for initial hi current demand tasks such as electric pylon deployment and self-starter motors?

On Tuesday, April 3, 2018 at 8:16:30 PM UTC-7, Duster wrote:
Would you use any of the lithium batteries for initial hi current demand tasks such as electric pylon deployment and self-starter motors?

I would (and do) use a properly spec'd LFP for that purpose. However saying so will start an epic chit fight on this thread like the other ones. So it would be best to live in the past and use whatever your copyright 1995 flight manual says to use. Don't do so unless you are familiar with all the issues and able to make a proper engineering call.

On Tuesday, April 3, 2018 at 11:05:18 PM UTC-4, wrote:
I have flown with both an LFP and SLA battery in my ship for 5 years. I alternate which one is primary and which one is secondary on each flight. A PowerSonic 12V14Ah SLA vs Powerizer 12V15Ah LFP. With all my instruments running the SLA voltage drops below the minimum requirements of my radio by 5 hours. My LFP has never failed to power everything up to a 7 hour flight. The SLA gets replaced after 3 years. My LFP is six years old and still working perfectly.

When I fly in very cold conditions (0C) the SLA is usually not driving my radio by three hours. Again, the LFP has run up to six hours without any significant voltage drop.

My microair 760 likes the higher voltage of the LiFePo, and I needed two 12V9Ah SLAs for long flights; never had to switch to back-up with LiFePo. I also like the faster charge, and the way the new batteries maintain charge.

I have to ask, then:Â* Why keep putting SLA batteries in your glider?Â* Do
you need them for weight and balance?Â* Why not just two LiFePO4?

My experience with the lithium batteries was nothing short of terrific.Â*
Prior to the switch, I couldn't power everything with two SLA batteries
for 5 hours (15 AH combined).Â* After switching (10 AH LFP), I never had
a shortage of power.

On 4/3/2018 9:05 PM, wrote:
I have flown with both an LFP and SLA battery in my ship for 5 years. I alternate which one is primary and which one is secondary on each flight. A PowerSonic 12V14Ah SLA vs Powerizer 12V15Ah LFP. With all my instruments running the SLA voltage drops below the minimum requirements of my radio by 5 hours. My LFP has never failed to power everything up to a 7 hour flight. The SLA gets replaced after 3 years. My LFP is six years old and still working perfectly.

When I fly in very cold conditions (0C) the SLA is usually not driving my radio by three hours. Again, the LFP has run up to six hours without any significant voltage drop.




--
Dan, 5J

A few things about SLA batteries.

The capacity is usually defined when discharged at the C/20 rate - so for a
7Ah battery 350 mA for 20 hours. The capacity at higher rates is reduced.
If you try to take 1.4A out of a 7Ah battery it won't last 5 hours.

I have found that if you treat them well they last well. Treating them
well means not to over discharge them, or overcharge them, and to recharge
them as soon as possible.

I have had good results with a simple constant voltage charger, charging to
13.6V. This seems to be enough to recharge them overnight. I've had
batteries last for 5 years or more.

The trick is to look at your energy budget, how much current do you need?
For a fairly simple system, a LX7007 (260 mA), a radio (200 mA) and a nav
device (200 mA), that's about 7 Ah in 10 hours. That lot should run off 2
7Ah batteries with no trouble. If you have higher demands then install
enough capacity that you only use 50% on the average day's flying.

The reservation about Lithium based batteries I have is their tendency to
catch fire. I realise that this depends on the chemistry and manufacture
but there have been enough instances of this that I'd be inclined to be
cautious unless the reduced mass and increased energy density is
essential.

And regardless of what chemistry your batteries use and what other things
are in place put a fuse in the battery lead close to the battery. All
batteries have enough capacity to produce an entertaining amount of acrid
smoke in the cockpit if you get a short.

Chris


At 14:40 04 April 2018, Dan Marotta wrote:
I have to ask, then:Â* Why keep putting SLA batteries in your glider?Â* Do

you need them for weight and balance?Â* Why not just two LiFePO4?

My experience with the lithium batteries was nothing short of terrific.Â*

Prior to the switch, I couldn't power everything with two SLA batteries
for 5 hours (15 AH combined).Â* After switching (10 AH LFP), I never had
a shortage of power.

On 4/3/2018 9:05 PM, wrote:
I have flown with both an LFP and SLA battery in my ship for 5 years.
I
alternate which one is primary and which one is secondary on each flight.

A PowerSonic 12V14Ah SLA vs Powerizer 12V15Ah LFP. With all my
instruments
running the SLA voltage drops below the minimum requirements of my radio
by
5 hours. My LFP has never failed to power everything up to a 7 hour
flight. The SLA gets replaced after 3 years. My LFP is six years old
and
still working perfectly.

When I fly in very cold conditions (0C) the SLA is usually not driving
my
radio by three hours. Again, the LFP has run up to six hours without any
significant voltage drop.




--
Dan, 5J

On Wednesday, April 4, 2018 at 12:00:07 PM UTC-7, Chris Rowland wrote:
A few things about SLA batteries.

The capacity is usually defined when discharged at the C/20 rate - so for a
7Ah battery 350 mA for 20 hours. The capacity at higher rates is reduced..
If you try to take 1.4A out of a 7Ah battery it won't last 5 hours.

I have found that if you treat them well they last well. Treating them
well means not to over discharge them, or overcharge them, and to recharge
them as soon as possible.

I have had good results with a simple constant voltage charger, charging to
13.6V. This seems to be enough to recharge them overnight. I've had
batteries last for 5 years or more.

The trick is to look at your energy budget, how much current do you need?
For a fairly simple system, a LX7007 (260 mA), a radio (200 mA) and a nav
device (200 mA), that's about 7 Ah in 10 hours. That lot should run off 2
7Ah batteries with no trouble. If you have higher demands then install
enough capacity that you only use 50% on the average day's flying.

The reservation about Lithium based batteries I have is their tendency to
catch fire. I realise that this depends on the chemistry and manufacture
but there have been enough instances of this that I'd be inclined to be
cautious unless the reduced mass and increased energy density is
essential.

And regardless of what chemistry your batteries use and what other things
are in place put a fuse in the battery lead close to the battery. All
batteries have enough capacity to produce an entertaining amount of acrid
smoke in the cockpit if you get a short.

Chris


At 14:40 04 April 2018, Dan Marotta wrote:
I have to ask, then:Â* Why keep putting SLA batteries in your glider?Â* Do

you need them for weight and balance?Â* Why not just two LiFePO4?

My experience with the lithium batteries was nothing short of terrific.Â*

Prior to the switch, I couldn't power everything with two SLA batteries
for 5 hours (15 AH combined).Â* After switching (10 AH LFP), I never had
a shortage of power.

On 4/3/2018 9:05 PM, wrote:
I have flown with both an LFP and SLA battery in my ship for 5 years.
I
alternate which one is primary and which one is secondary on each flight..

A PowerSonic 12V14Ah SLA vs Powerizer 12V15Ah LFP. With all my
instruments
running the SLA voltage drops below the minimum requirements of my radio
by
5 hours. My LFP has never failed to power everything up to a 7 hour
flight. The SLA gets replaced after 3 years. My LFP is six years old
and
still working perfectly.

When I fly in very cold conditions (0C) the SLA is usually not driving
my
radio by three hours. Again, the LFP has run up to six hours without any
significant voltage drop.




--
Dan, 5J


Please relate to us the stories (with backup links) about - specifically - LiFePo4 batteries catching fire in gliders - or other similar applications.

John,

My experiences with LiFePO4

I have never heard of a LiFePO4 battery catching fire. I have had some customers connect reverse polarity. It burnt up the internal positive wire but the battery did not burn. I also just shorted a LiFePO4 12V10Ah turned it upside down and placed on a metal plate. It got hot and distorted the case near the contacts for the cells. It did not burn and was cool when I looked at it 1/2 hour later.

I had one supplier that gave me 24 Volt chargers by mistake. I charged one battery overnight and it got very large but did not catch fire.

Richard
www.craggyaero.com

Wow. Didn't these batteries have a battery management system to prevent
damage?



On 04/04/2018 03:22 PM, Richard Pfiffner wrote:



John,

My experiences with LiFePO4

I have never heard of a LiFePO4 battery catching fire. I have had some customers connect reverse polarity. It burnt up the internal positive wire but the battery did not burn. I also just shorted a LiFePO4 12V10Ah turned it upside down and placed on a metal plate. It got hot and distorted the case near the contacts for the cells. It did not burn and was cool when I looked at it 1/2 hour later.

I had one supplier that gave me 24 Volt chargers by mistake. I charged one battery overnight and it got very large but did not catch fire.

Richard
www.craggyaero.com