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Hi. Is this the best way to prolong battery life?

As I understand from reading a few forums and posts, a battery only has a certain amount of cycles before it dies. So, if I keep my batteries at float voltage and only start discharging them once the grid goes down, will this make my batteries last longer? or should I just cycle them every day at night? (They can handle the load with 70% left when the sun comes out and takes over to re-charge them) This will bring my utility bill down, but at the cost of the batteries been cycled a lot more.

I've set up solpiplog to change the charge priority so the batteries never goes below 99%, unless we have very bad overcast. Don't mind using the batteries, but will this behaviour really make my batteries last a few years more?, or a few months? or should I just don't worry and use them?

I haven't posted this forum for a long time. Any views/comments on this would be greatly appreciated.

 

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I don't know the answer to this, but I am equally interested.

I think it depends on their design and what you want from them.

A given is that using the grid is much cheaper than battery power.

So,I have heard of batteries that are designed to float for years, these are expensive and for what?

On the other hand:

I have also heard that proper deep cycle LA batteries don't last indefinitely, so that would seem to mean it makes economic sense to use them, to some smaller DOD regular anyway.

But:

If I was off grid, I'd definitely go for Lithiums and drive them harder.

Presently, I am nursing along 800Ah of LA car batteries, hoping to get another 6 months, keeping them in float. They are in their 4th year and the bank is 66% as big as when it started.

Edited by phil.g00
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13 minutes ago, phil.g00 said:

I don't know the answer to this, but I am equally interested.

I think it depends on their design and what you want from them.

A given is that using the grid is much cheaper than battery power.

So,I have heard of batteries that are designed to float for years, these are expensive and for what?

On the other hand:

I have also heard that proper deep cycle LA batteries don't last indefinitely, so that would seem to mean it makes economic sense to use them, to some smaller DOD regular anyway.

But:

If I was off grid, I'd definitely go for Lithiums and drive them harder.

Presently, I am nursing along 800Ah of LA car batteries, hoping to get another 6 months, keeping them in float. They are in their 4th year and the bank is 66% as big as when it started.

Thanks Phil.

Have my batteries (Allgrand gel vlra) batteries for about a year now and it seems they are still brand new. Once in a while (about 4 times) when the grid was off at night I punished them to about 42v, everything on and running through the night. Fridge, freezer, tv, amp,subwoofer,Server,internet,lights. Never had any problems. Next day sun comes out and start charging up the batteries, full at noon. But this is like driving your car at 280km/h, very lekker, but it will cost you eventually

 

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1 minute ago, Warlok said:

Thanks Phil.

Have my batteries (Allgrand gel vlra) batteries for about a year now and it seems they are still brand new. Once in a while (about 4 times) when the grid was off at night I punished them to about 42v, everything on and running through the night. Fridge, freezer, tv, amp,subwoofer,Server,internet,lights. Never had any problems. Next day sun comes out and start charging up the batteries, full at noon. But this is like driving your car at 280km/h, very lekker, but it will cost you eventually

 

Sorry, just checked. Installed system April 2019

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On 2019/11/17 at 1:04 PM, Warlok said:

So, if I keep my batteries at float voltage and only start discharging them once the grid goes down, will this make my batteries last longer?

 

On 2019/11/17 at 1:22 PM, phil.g00 said:

I have also heard that proper deep cycle LA batteries don't last indefinitely

You have to take into consideration the design life of the battery as well. I had the privileged a few years back to have two chemical engineer friends, and both were working for Battery Manufacturers. Two things both of them told me that I can mention is:

  1. Do not keep batteries charged for ever, give them a proper discharge at least once a month, keeping them charged also shortens their expected lifespan. (Why, I cant remember) 
  2. You can keep your bank of lets say, Trojan batteries (I asked them about trojans because I just bought Trojans) charged, but you cant expect to get 10 years out of them because you kept them charged. you can only expect to get 8 years out of them, because the chemical design was done for 8 years. 

Personally I feel you should cycle your batteries daily (to a safe level only), by doing so, you recover some of the cost at least. You will loose the complete investment if you don't and the batteries die from old age in any case.  

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19 minutes ago, Jaco de Jongh said:

Personally I feel you should cycle your batteries daily (to a safe level only), by doing so, you recover some of the cost at least. You will loose the complete investment if you don't and the batteries die from old age in any case.  

Exactly!

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On 2019/11/17 at 1:48 PM, Warlok said:

Once in a while (about 4 times) when the grid was off at night I punished them to about 42v,

I am not sure about VRLA's but i wont allow normal LA's to discharge to that level. Normally low voltage cutoff on inverters are set at 46volt, taking it to 42 to me sounds a bit risky. 

For interest sake, look at the Algrand performance graphs below. Take the average temp where you stay, that will give you the expected chemical lifespan of the battery. Then look at how far you can discharge your batteries to get the Cycles to match that expected lifespan. That should theoretically show you the % of DOD you can use to get the most back from your investment. 

For example if the average temp in your are is 34 degree C, you can expect a chemical lifespan of 7.5 years, also, if you allow a DOD of 25% it will give you an expected Cycle life of 2750 Cycles, and if you do it daily that also gives you 7.5 years. In this case it will make sense to allow 25%DOD daily as it matches the Chemical design perfectly. 

Algrand.JPG.a21828f9e96f2fc227af84ef0b1d0fa0.JPG

 

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