Replace lead acid battery with LiFePO4

J

Jan-P

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Hello.

I want to replace the 12V 7Ah lead acid battery that I use for my alarm system and electric fence with two LiFePO4 versions.

SecuriProd sells a 12.8V 7Ah model that they say is a drop in replacement. I am just concerned that, although this model may last longer (life span) than the lead acid variety, it will still take heavy knocks due to stage 6+ loadshedding. I then wonder whether it makes sense to pay so much more for it (R800 vs R350).

My question is this: would the 12.8V 20Ah model make more sense? It is more than double the price but I figured that the higher capacity will prolong its life because it won't be emptied as often, thereby reducing costs in the long term.

I am not very clued up on electric theory so I'd really appreciate some help. Firstly, does it make sense? And would it be plug and play or whould I need to install some kind of adapter for it to work? I know it is physically bigger as well, but I can deal with that using an extension.

Here is a link to the larger model: https://www.makro.co.za/home-garden...v-20ah/p/c77cb036-8458-4192-92ec-97ff26553ac3
 
Features:
  • Securi-Prod Lithium Iron Phosphate LiFePO4) Battery
  • New Lithium Iron Phosphate cells
  • High Cycle Life: >3000 @ 80% Depth of Discharge

Isn't the cycle life the same for all sizes?
 
With 4 hours of loadshedding and 2 hours of power to charge before the next cycle of loadshedding, this is not enough time to charge the battery.

This will affect the lifespan of the battery, rather stick with the lead acid battery and save your money.

If you could add a solar panel to charge the battery then it's worthwhile buying the LiFePO4 battery.
 
D said:
Features:
  • Securi-Prod Lithium Iron Phosphate LiFePO4) Battery
  • New Lithium Iron Phosphate cells
  • High Cycle Life: >3000 @ 80% Depth of Discharge

Isn't the cycle life the same for all sizes?
Click to expand...

The cycle life will be the same, but a larger battery will be less likey to drain to 20%. I was hoping to save costs over the long term.
 
nivo said:
With 4 hours of loadshedding and 2 hours of power to charge before the next cycle of loadshedding, this is not enough time to charge the battery.

This will affect the lifespan of the battery, rather stick with the lead acid battery and save your money.

If you could add a solar panel to charge the battery then it's worthwhile buying the LiFePO4 battery.
Click to expand...

The problem with the lead acid variety is that they cost around R350 and I have to replace them every three months for my alarm to function. So it turns out to be quite expensive.
 
Could you parallel 2x 7ah lead acids to give you better runtime, or use a higher capacity lead acid battery; unsure on the charge rate of the alarm system itself though, or whether it would charge both in the 2hr window.

If running 2, they should not discharge to the level of 1 on its own, I believe.
 
"D" said:
Surely that can't be due to loadshedding only?
Click to expand...
What's the power draw of a standard alarm system?

7Ah @ 12v is a measly 85Wh.

Just using 45Wh from that battery a couple of times a day will render that battery useless in a few months. I don't think a 20Ah LA battery will make much of a difference.

These batteries and the chargers in alarm and gate motors were never intended for daily cycling but only for emergency electricity outages.
 
AchmatK said:
What's the power draw of a standard alarm system?

7Ah @ 12v is a measly 85Wh.

Just using 45Wh from that battery a couple of times a day will render that battery useless in a few months. I don't think a 20Ah LA battery will make much of a difference.

These batteries and the chargers in alarm and gate motors were never intended for daily cycling but only for emergency electricity outages.
Click to expand...

This is why I was thinking of using a larger capacity LiFePO4 battery. Is my thinking flawed?
 
Jan-P said:
This is why I was thinking of using a larger capacity LiFePO4 battery. Is my thinking flawed?
Click to expand...
Larger lithium batteries will help. Only real concern is if the built in chargers in the alarm and gate motors can charge it.

Lithium wil also give you 3 000 cycles even if you discharge them all the way. They are more forgiving than LA batteries if they are left to go flat during load shedding. Taking an LA battery to below 50% just a few times will severely degrade them and needing replacement within months.

Even if you only get 1 000 cycles out of a lithium replacement battery that's going to be a couple of years before they will need replacement.
 
AchmatK said:
Larger lithium batteries will help. Only real concern is if the built in chargers in the alarm and gate motors can charge it.

Lithium wil also give you 3 000 cycles even if you discharge them all the way. They are more forgiving than LA batteries if they are left to go flat during load shedding. Taking an LA battery to below 50% just a few times will severely degrade them and needing replacement within months.

Even if you only get 1 000 cycles out of a lithium replacement battery that's going to be a couple of years before they will need replacement.
Click to expand...

Thanks, AchmatK.

I think I will try this.
 
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