SLA batteries opinions?

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 11:24:19 AM UTC-7, john firth wrote:
On Monday, April 2, 2018 at 1:14:19 PM UTC-4, john firth wrote:
Recently I tested two 12v SLA s which had been in use
sequentially for some years usually recharged before going
going flat, or at least within one day.
Both were run down to 10.5 v with a 10 ohm load and then recharged to 14v,

The Yuasa 7 AH bought 2005 was good for about 2.5 AH
the UB 1280 8AH 6 years old good for 2AH.
On this showing the Yuasa look like the better battery.
Both were used as panel supplies running at .5 A load.

Any opinions on competing SLA batteries?

John

The specs on the Dakota 12v 10 ah ($99) bats look good
Any experiences?

JMF

They are like all the 10Ah Chinese LiFePO4 batteries.
They Claim 10Amp but when tested with deliver 8 or 9 aH.

I just tested 2 K2 12V10Ah batteries for a customer use for several years. Tests results with a West Mountain Radio CBA IV 7.3 aH and 8.5 aH. My conclusion is they are not any better than the $99 12V9Ah batteries

Richard
www.craggyaero.com

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

At 20:25 04 April 2018, jfitch wrote:
On Wednesday, April 4, 2018 at 12:00:07 PM UTC-7, Chris Rowland wrote:

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.

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


The more literate members of this forum will notice that I said "Lithium
based" and "this depends on the chemistry and manufacture".

A couple of links a
http://ul-segelflug.de/images/storie...017_G-GSGS.pdf

and

https://assets.publishing.service.go...-AOP_09-15.pdf

and

https://www.caa.co.uk/Commercial-ind...ium-batteries/

An experiment to try is to short out a fully charged battery and see what
happens. Wait until everything is cool and think if you want to be around
it.

Chris

On Wednesday, April 4, 2018 at 2:31:07 PM UTC-7, kinsell wrote:
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


I have found that BMS will not save a short.

Richard
www.craggyaero.com

On Wednesday, April 4, 2018 at 1:25:55 PM UTC-7, jfitch wrote:
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.

r.a.s. is powered by lithium.

On Wednesday, April 4, 2018 at 7:16:02 PM UTC-4, Darryl Ramm wrote:
r.a.s. is powered by lithium.

- you mean the type that comes in pills? :-)

Regarding the other messages, I am surprised that the BMS does not protect from a short, I thought that was one of the stated protections officially promised. And that BMS was one major advantage of the (better) LiFePO4 batteries over SLA.

The Gliding federation in Australia has approved the Fusion lithium 10ah battery for use in place of SLA.
http://doc.glidingaustralia.org/inde...ess&Itemid=101
Ive just got one, and am very happy with it so far.