Real world battery life experience

[Guest]

31 minutes ago, Jaco de Jongh said:

Back to the chemisist. He asked me what DOD I allow and I told him 20%, he laughed at me and told me that i am wasting my money. He explained that the "chemical design" if I may call it that, of the Trojans allow for a maximum life time of 8 years and that the battery might even fail after that time  irrespective of the total cycles it was subjected to. His recommendation to me was to allow for a 50% DOD, and to use the battery's to get the most from them before they pack up due to old age.

Called a Trojan supplier with all the above info.

He said the 1600 cycles at 50% DOD is pretty accurate. 4000 cycles at 20% also.

And the "chemical design" is pretty much in line what Trojan states as what they anticipate the cycles to be.

BUT, what we are doing here are not golf carts nor forklifts, so with what you found Jaco, combining all the info, I am adjusting my expectations to 8 years at 20% DOD, with 4000 cycles = +- 10 years, as a bonus.

But, once we have figured how to adjust the BMV's programatically, I am going to drop my 20% DOD lower. Going to use the batts and "feel how it feels".

[Jaco De Jongh]

6 minutes ago, The Terrible Triplett said:

I am adjusting my expectations to 8 years at 20% DOD, with 4000 cycles = +- 10 years, as a bonus

Exactly what I had in mind when I bought the Trojans. Now I have increased to 30% , but wont feel bad if I need to go down to 40% occasionally. I wont do that every day, but am more comfortable allowing it when its needed.  

[SilverNodashi]

18 hours ago, Jaco de Jongh said:

For what its worth, and please don't understand me wrong, I don't make this recommendation. This was a statement made by a supplier. 

The guy I bought my Trojans from is a chemisist and owes two battery company's and are a partner in two more.  According to to him the Trojans are the best flat plate batteries in the world. He told me that the Trojans can really take punishment , for example in Golf cars they get depleted on a daily basis and recharged for use the next day. He claimed that even with a 80% DOD the battery can last up to 7 years, but in most cases they get replaced in about 6 years.

I confirmed the replacement frequency with 3 different Golf estates and was directed to talk to Easy-go who is in charge of the maintenance contracts for most of the Golf Clubs/Estates. Got hold of the owner of the Pretoria/Johannesburg Branch and asked him about this. He confirmed that the normal life time under heavy punishment is 5-6 years. I asked him if i can buy some of the old one and he said the same as TTT above. When they get replaced, they are shot. They replace thousands of battery's a year, so they have the best technology available to try revive and prolong the life of their battery's and when they decide to toss them its because there is nothing left in them. 

Back to the chemisist. He asked me what DOD I allow and I told him 20%, he laughed at me and told me that i am wasting my money. He explained that the "chemical design" if I may call it that, of the Trojans allow for a maximum life time of 8 years and that the battery might even fail after that time  irrespective of the total cycles it was subjected to. His recommendation to me was to allow for a 50% DOD, and to use the battery's to get the most from them before they pack up due to old age.

Interesting conversations I had with these guys and it made me think differently about my bank, what if they are  right, what if I nurse my bank, only for it to fail chemically because of age. Now my DOD is limited to 30% and i will even allow for 40 should the need arise. My current load doesn't even take me to the 30% mark. Some mornings I still have 10-14 hours Time to go according to my 702. 

 

EDIT. The first guy  said that they have a store for their scrap battery's with 40000 scrap battery's at any given time with less that 5% being Trojans. 

Sounds like you spoke to Pieter, or Petrus? He's quite knowledgeable on the product, but I won't "hang on his lips" with this. Trojans are good but some other brands deliver the same performance. 

I have seen forklift 2V cells which can be drained down to 0%, get fully recharged the next day and still happily continue along. This particular bank is an unbranded bank. Some of the more expensive brands also do this very well. 

[ebrsa]

@Jaco de Jongh 's post contains some very interesting information regarding DOD. This is surely a subject that deserves much attention. What DOD will result in the most economical use of the batteries. I went with T105 Trojans as they are 6 volt so if a cell dies, I will be dumping 2 good ones not 5 as with a 12 volt battery. Forgot why I chose flooded but I don't mind checking and adding distilled water if necessary once a month or so. This week I am increasing capacity from 225 to 450AH and will then see what DOD is reached if I run off batteries all night after the heavy loads like supper cooking is done. Found that on sunny days my batteries are recharged after DOD of 20% at around 11:00 am and then around 800W is wasted as the panel capacity is 2250W and average load less than 1000W. This is clearly a waste of of generating capacity.

[Jaco De Jongh]

10 hours ago, ebrsa said:

450AH and will then see what DOD is reached

To give you an Idea of what to expect. I work with a 450Ah bank and start drawing amps from the batteries after 4 in the afternoon. With normal load, TV , home entrainment center,  lights, 4min 1800 watt microwave, 2 gaming pc's, 4 ceiling fans, fridge ext. I run a 800watt load till about 10-11 at night, after that, couple of lights, 3 ceiling fans and fridge will drop the load to 350watts average. Before switching of the bulk of the above, the BMV normally indicates 8-9 Hours "TIME TO GO" to reach my set point of 70% SOC (30% DOD), After switching off, that time increases to over 16 Hours. Some mornings I still have 9hours and above left on the BMV

[DeepBass9]

11 hours ago, Jaco de Jongh said:

To give you an Idea of what to expect. I work with a 450Ah bank and start drawing amps from the batteries after 4 in the afternoon. With normal load, TV , home entrainment center,  lights, 4min 1800 watt microwave, 2 gaming pc's, 4 ceiling fans, fridge ext. I run a 800watt load till about 10-11 at night, after that, couple of lights, 3 ceiling fans and fridge will drop the load to 350watts average. Before switching of the bulk of the above, the BMV normally indicates 8-9 Hours "TIME TO GO" to reach my set point of 70% SOC (30% DOD), After switching off, that time increases to over 16 Hours. Some mornings I still have 9hours and above left

That's interesting, I am really going lightly on my 300Ah bank in that case. Overnight I use between 5 and 10,  3-5W LEDs , 1 or 2 laptops. wireless access point and router and that's about it. Fridge and freezer of on a timer from 6am-6pm. So evening I draw about 300W, and overnight 150-200W  Normally in the mornings the batteries are 49.2V or therabouts, but I don't know the real SOC. If I see <49V in the morning its rare.

[Guest]

1 hour ago, DeepBass9 said:

Fridge and freezer of on a timer from 6am-6pm

Question, what made you decide to not power them 24/7 on solar?

Using only 5-10% of the batts is a little bit low. Try for 20% maybe?

[SilverNodashi]

1 hour ago, DeepBass9 said:

Fridge and freezer of on a timer from 6am-6pm.

This didn't work for me, some foodstuffs don't like it and we often had to throw away stuff, especially meat and dairy products. It could be because our freezer is about 30 years old, but only use about 150w/hr

[DeepBass9]

39 minutes ago, The Terrible Triplett said:

Question, what made you decide to not power them 24/7 on solar?

 

I don't want to shock you, but the sun only shines in the day......

Its not neccessary though to run them 24/7, they are both turned to their coldest, kept full all the time (even if its bottles of cold water in the fridge). And at night they are kept shut after about 8pm. Its a chest freezer and an upright fridge without a freezer compartment.

[DeepBass9]

41 minutes ago, SilverNodashi said:

This didn't work for me, some foodstuffs don't like it and we often had to throw away stuff, especially meat and dairy products. It could be because our freezer is about 30 years old, but only use about 150w/hr

My fridge & freezer use that much together. Maybe the insulation is better in newer fridges. Another factor is that dairy products last about 5 mins in the fridge with small children.

[Guest]

21 minutes ago, DeepBass9 said:

I don't want to shock you, but the sun only shines in the day.

Got me there ...

Let me rephrase: Power them 24/7 off your solar SYSTEM so that the batts are used a bit more at night to 20% DOD or close to that.

[DeepBass9]

Maybe because I started off with a 150Ah bank where it was neccessary, and just never changed? 

[Guest]

Cool. I asked the question to hear your view, and your "maybe because" actually makes sense. 

If it works, why fix it.

[SilverNodashi]

1 hour ago, DeepBass9 said:

My fridge & freezer use that much together. Maybe the insulation is better in newer fridges. Another factor is that dairy products last about 5 mins in the fridge with small children.

I know, I should replace that ancient freezer but can't yet justify the R8K investment to save a couple watt/hour

[DeepBass9]

That's OK, just buy yourself some more solar panels instead!

[SilverNodashi]

1 hour ago, DeepBass9 said:

That's OK, just buy yourself some more solar panels instead!

I already did, it's the night time base load that could be lower with a new fridge. One day. When it packs up. If it packs up. 

[DeepBass9]

Solved...

[___]

1 hour ago, SilverNodashi said:

One day. When it packs up. If it packs up.

My old fridge/freezer combo had a 250w compressor and was on 12 hours a day. I'm not kidding. The cost of the new fridge (7.5k) is easily covered in electricity savings over 4.5 years, probably less if you include increases, and even less when considering other factors like 1) better cooling meaning less spoiled food and 2) more space means buying in bulk for more savings.

Then I sold the old one for 1k, so repayment is definitely less than 4 years.

I also did the freezer and the numbers were similar, except the Defy Eco unit (1kwh a day vs 3kwh a day before) was only R1999 at the time! At R2 a unit (top end domestic, if I recall), that's 500 days! Not even two years.

Then I sold the old one for R600 too, so repayment was a year.

That is to say, I also thought I'll do it if/when it packs up, but I changed my mind :-)

[wtjaden]

Too low temps will also cause a fridge/freezer to run allot longer.
my fridge/freezer  seem to be happy at   -19c and  3c  but going to -20 on the freezer increases the run time allot 

[Chris Hobson]

Ok so this morning I awoke to classic battery age warnings

Graph of Battery volts (Inverter and BMV) Batteries' voltage steadily decreases and then just free falls.

Here is the overnight load so no large loads.

The batteries in question are CB Solar 260Ah batteries rated at 800 cycles (50% DOD). We have done 670 cycles at a DOD of 42%. However if you included the fact that batteries age twice as fast at 30°C than at 25°C then with our high summer temperatures it is equivalent about 900 cycles. Total cost is R22.80  per cycle or roughly (because I do not have totally accurate figures) R4.20/kWh. That is considerably better than the R10/kwh running on a gennie.

 

[Mark]

Nice Chris.  I think for you being offgrid you are getting a great deal vs the Gennie.  Have you calculated the costs of the batteries and then can you give us a cost per kwh based on replacement value...

[Czauto]

I had the same problem, same graph. I had just one cell, ONE CELL in the whol bank that was at fault. At low loads it was okay but at high loads or if the voltage went down too low it seems that one cell shorted and screw up the whol bank!

Sent from my S60 using Tapatalk

[Guest]

In my experiences, batteries ALWAYS fail when we need it the least ... 

[Engr naeem]

bulk& float voltage are always designed in accordance with application of load & their usages.

[Chris Hobson]

On 27/04/2017 at 6:06 PM, The Terrible Triplett said:

In my experiences, batteries ALWAYS fail when we need it the least ... 

Is there ever a good time for a battery to fail?