# Interest group forums > Energy and Resource Conservation Forum >  Selecting a solar lithium battery

## Isetech

It seems once again, no apples with apples comparisons, only apples with oranges and pears with grapes. 

What are the key factor to consider.

The battery capacity in amp/hr and KWh 

Cycle life @ the C rating.

The normal and max charge/discharge current.

The type of cells being used in the battery.

The communication with the inverter. 

How many you can connect in parallel.

Working temperature.

The warranty. 

Very very important, the support and availability.

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## Isetech

The C rating of the battery, which is better?

Hubble 

New Li-ion Prismatic Cells

3000 Cycles @ 100% DOD, Above 6000 cycles @ 50% DOD

New Li-ion Prismatic Cells

Or

Sunsynk

 LiFePO4,Lithium Iron Phosphate

6000 Cycles @ 80% DOD / 25°C / 0.5C,  60% EOL

So if you increase the Sunsynk to 1C then it would only offer 300 cycles, it would be the same specs? 

I am trying to understand which would be a better buy, they are both the same price, Hubble a little more expensive. 

If it were the support, the company I am dealing with for the Sunsynk would be my choice. 

It seems they both have the same cells, the communication is better between the Sunsynk inverter and the Sunsynk battery and I hear if I use the Sunsynk battery with the Sunsynk inverter there could be a better warranty period on both products. 

DO you have any other suggestions or comments with regards to selecting a battery for the Sunsynk inverter. 

Some say the Deye and Sunsynk are the same inverter out the same factory, unfortunately I will only be able to comment on that once I have the inverter and battery setup on my work bench.

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## Isetech

The next question - 

3000 Cycles @ 100% DOD, Above 6000 cycles @ 50% DOD

6000 Cycles @ 80% DOD / 25°C / 0.5C, 60% EOL

Lets try get an apples for apples comparison @ 25degreesC : 

If both batteries had 3000 cycles @ 100 % DOD, what would be the C rating of the Sunsynk battery? 

IF both batteries had 6000 cycles A 80% DOD  what would be the C rating of the Hubble battery? 

If both batteries had 6000 cycles @ 100% DOD what would the EOL % value be? 


What makes the one battery better than the other, taking into consideration that we are going to be installing Sunsynk inverters for our customers. 

The shape of the cells, hubble indicates the use of prismatic cells? I would need to find out the shape of the Sunsynk cell, I would think by now they are also using prismatic cells.

The capacity of the individual cells? Could the Hubble battery be using a higher amp/hr cell or more cells to give it a 1C rating and +/- 16 year design life? 

Would that indicate that the Sunsynk has a 30 year design life @ 6000 cycles? 

The communication between the inverter and the battery and the software for the monitoring? 

The make of the cells, Hubble indicate they using BYD ? I somewhere that Sunsynk are using a rebranded BYD battery, I would need to verify this statement. 

Just so many questions. I am glad I am at that point where people cant baffle me with all the bullshyte I hear or read. So many experts in this field, trying to find that person who has a little more knowledge than the general ramble, can prove to be a challenge.

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## Justloadit

Very difficult to compare batteries, as each supplier cherry picks the specifications they wish to hand to customers.

The 'C' rating refers to the charge value/capacity for reliable battery life.
Charging Lithium at 1C, will require careful monitoring of cell temperature, and reducing current(C) as the temperature rises.
Un-monitored battery temperature would recommend a below 0.5C

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## Isetech

Been doing more research into batteries today.

I still cannot find what makes one 5 kwh lithium battery better than another brand.

It seems that all batteries are capable of 1C, it just cuts the life span in half.

So if a battery offers 1C capabilities, you will notice it only has a 3000 cycle life span. 

So the battery offering 0.5C will have a 6000 cycle life span.

Prismatic cells are not a selling point, like BYD cells used by  most reputable brands to build their batteries using prismatic cells. 

I am at the point were I believe it boils down to the compatibility of the battery to the inverter. Using a Sunsynk battery with a Sunsynk inverter just makes more sense. I am sure the Sunsynk is rebranded battery spec'd to work with the inverter. 

There is a R2000 difference and something else to consider is the delivery cost and courier fees if the battery fails. It starts adding up. Where you source these products could make or break the sale.

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## Isetech

Looking at the spec sheet of the Sunsynk battery, it has a normal charge/discharge rate of 50 amps and a max charge discharge rate of 100 amps. How often would you require your battery to charge or discharge your battery at the max 100 amps? As mentioned then we have the temperature to consider, the quickest way to kill any battery is heat. 

Something else to consider, it's gona give you less than 1 hour of backup, so I would say a really badly spec'd system would require a 1C battery.

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## Isetech

How do companies determine the C rating of their batteries.

The capacity of each cell?

The physical size of the cell? 

The number of cells in the battery? 

The BMS firmware? 

Maybe the 1 C battery has cooling fans and the 0.5C battery not? 

If the battery is rated at 100 amp/hr battery, using prismatic cells and the same type of cells (BYD). 

What am I missing?

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## Justloadit

Batteries usually do not have any fans, so battery assembly probably plays a role in the temperature build up with in the pack during charging/discharging. 
Majority of battery packs are made up of the 18650 single cell.
They come in a variety of ampere capacity. 
By placing many in parallel, will give the battery ampere capacity in Amps. Then by placing a number of these packs in series, will give you the voltage of the battery pack. The BMS is then wired to each bank of parallel packs to ensure that the pack gets the correct current to match the full pack. 
The Tesla battery packs have water ways between the cells, which are kept at a constant temperature with a cooling liquid, and hence the reason they can be quickly charged as the individual cells are cooled down.

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## Isetech

How do you achieve 1C rating, by using more cells in parallel and derating the battery to as lower kwh rating or installing systems like heat sinks or a radiator systems ? 

Are prismatic cells made up of 18650 cells? 

I heard something interesting on the weekend, if you are selling lithium batteries and using "seconds" would you be required to advertise that your batteries are sold as "used " or could you still sell them as newly built or some other lingo to dodge the fact that your cells are not 1 st generation or off the production line ?

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## Justloadit

> How do you achieve 1C rating, by using more cells in parallel and derating the battery to as lower kwh rating or installing systems like heat sinks or a radiator systems ?


the 1C refers to the battery capacity. Adding more cells in parallel basically increases the value in amperes of the battery capacity. Using the terminology of 'C' makes the statement universal to any battery, where you would multiply the 'C' by the battery capacity in Amperes




> Are prismatic cells made up of 18650 cells?


Not necessarily.
A prismatic lithium battery, features a cell that has been encased in either aluminum or steel, mainly for the purposes of increased stability.

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## Isetech

I am trying to figue out how one manufacturer sells a battery with a 0.5C and another a 1C, but they are both 5 kwh and both use BYD cells? 

From the little knowledge I have acquired about lithium batteries, the only way I can see that you could achieve a higher C rating is if you have a cooling system in place.

The one has increased the warranty to 10 years and the other has reduced the cycles to 3000 but indicates a 15 year life design. 

How do you cut through all the bullshit and get the apples to compare apples with apples or 5 kwh with 5 kwh? 

Deep cycle batteries had thicker platers and bases, what makes a lithium battery a good battery, what a the key point to identify when selecting a good quality lithium battery? 

If I have ever had to deal with an industry that tries to baffle customers with bullshit, this solar industry certainly takes the cake with the cherry on top.

What do we know about lithium batteries, the harder they work the lower the cycle life. Can we agree that if a battery is advertised at 1C with 3000 cycles, then a 0.5 C battery advertised at 0.5C at 6000 cycles, would also be capable of 1C rating if advertised at a max of 100 amps (for a 100 amp hour battery) if we reduce the cycles to 3000 cycles?

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## Isetech

I hear chatter about, lithium batteries being sold which are not off the production line, how could you verify if the cells in your battery pack are off the production line or if they repurposed? 

A QR code on the cells maybe, considering a seal would be fitted to all batteries, how would you verify the origin of the cells used in your battery? 

This could become a huge problem as older batteries are decommissioned.

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## Justloadit

There are also many poor quality and incorrectly marked cells.
If they sound cheap then there is something wrong!
Keep to the known name brands, they will not compromise their quality for a cheap battery, the investment is just too high.

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## Isetech

Its seems the challenge to get credible information out of battery manufacturers and suppliers is a lot more difficult than I thought.

You get to listen to a lot of "please hold your call is important to us" or "please hold why I redirect your call" or some tune while the technical person you are speaking to has to find a technical person who can relay the information to the technical person who has very basic technical knowledge.

Now I know why we are sitting with really badly designed  R150 000.00 solar systems  :Frown:

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## Isetech

Cycle life: determined by the depth 

Sunsynk:  6000 Cycles @ 80% DOD 

Hubble: 3000 cycles @ 100% DOD and 6000 cycles @50% DOD 

Other than the 10 year warranty if used in combination with the inverter, the sunsynk just doesn't seem to stand achance against the Hubble.

Even the price, I can get a Hubble battery R2000 cheaper than the Sunsynk. 

The question: will the Hubble battery communicate with the new Sunsynk data logger and software?

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## Isetech

Then I found this hidden away in small print at the bottom of the Sunsynk data sheet. 

1. Test conditions: 100% depth of discharge (DoD), 0.2C rate charge & discharge at 25℃

2. Charge/discharge derating occurs when the operating temperature from -10℃ to 5 ℃.& 45 ℃ to 55 ℃.3. Condition apply. 

Refer to SUN-BATT-5.12 Warranty Letter

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## Isetech

As I keep scratching and become more knowledgeable about this topic, the more I realise how much bullshit there is being rattled out there  :Frown:

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## Isetech

This has become quite a challenge. 

Too many variables, too little technical support. 

It seems everyone has the downloaded check sheet, anything past the check list you are on your own.

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## Isetech

Why is selecting the correct battery so important? Load shedding, as the levels of load shedding go up, so the demand for higher discharge rate and fast charging.

Why lead acid batteries just dont cut it anymore, they may seem like a cheaper viable option, but as soon as you throw in a stage 4 or above schedule, those batteries become lead weights. 

Waiting 10 hours for a 100 amp/hr to charge at the recommended 10% charge rate is going to leave you sitting in the dark with candles. Yes they are more affordable and practical for stage 1 load shedding, anything past that , with cable theft and sub station fires and explosions, or a couples days of cloudy weather if you are fortunate enough to have solar panels, you will soon be wishing you had put a little more thought into the system.

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## Isetech

Today we learnt a little more. 

I founds a battery which looked like it had exactly the same product information, 52VDC-100amp/hr and even 5.12 kwh written on the battery. The batteries look the same, and even the the same manufacturer. 

So makes the one different from the other? 

The voltage - no 

The kwh rating - no 

The amp/hr rating - no 

The BMS - no 

The temperature rating - no 

Ok so what makes the one R5000 more expensive than the other.

The cells look the same, they are both lithium ion lifePO4  so what makes one better than the other, apparently the cells. 

the questions you need to be asking: 

How long is the battery warranty, it should be at least 10 years.

The cycle life of the battery under daily use, not just as a backup battery, it should be at least 6000 cycles at 80 % DOD. 

What grading of life PO4 cells are being used, and seems to be the big question. what grade lifePO 4 cells are being used.

It seems any battery with a 3000 life cycle can be rated at 1C with a 5 year or less warranty. 

If you spending around R25000 on a lithium battery, with a 5 year warranty and 3000 cycles the cells could be B or C
 grade cells. 

The sad part we will only know in the next 5 to 10 years.

As for battery support, I am sure those who have tried to get more technical data will know what a joke that has become. 

I have been reading technical data and features advertised and comparing to the actual data sheets downloaded from the manufacturer, it gets quite interesting.

It seems lithium batteries and Nike shoes have a lot in common  :Wink:

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## Isetech

Lets take a closer look at the questions you should be asking your battery supplier when purchasing a 52 VDC - 100 amp/hr - 5 kwh lithium lifePO4 (not just the sale talk used by most suppliers with check sheet)

We are talking about the same battery a 52VDC - 100 Amp/hr - 5kwh lithium, one of the most common sold at this point.

1/ Is you battery designed for backup or daily use?

2/ What power can the battery sustain for a standard load shedding period and can it sustain this value for multiple power cuts per a single day and for how many days?

3/ Are the cells in the battery "new generation cells" ?

4/ Can the cells in the battery be used for high currents?

5/ Are the cells in the battery repurposed (seconds) or brand new (off the production line) and what grade of cells being used, not all LifePO4 cells are equal

6/ What is the designed life, there is a good chance the replay will be the same as all the batteries 15 years.

7/ What is the cycle life of the battery at 80% DOD, dont get confused with 50% and 100 % ?

8/ What is the C rating of the battery is charged and discharged at 50% and 100 %?

There is a lot more to batteries and I am only scratching the surface. Because this industry is still too new, we will only know the true facts in years to come as the batteries start to fail and warranty claims are put to the test.


Which brings me to a very very important part of your purchase, did person who sold you the battery inform you about the warranty registration, because without it you are a fish out of water flapping your gums trying to get your battery repaired or replaced.

Copied directly from a warranty form

"2.2 It is the duty of the Customer to obtain confirmation from the installer that the product had been duly registered."


This is the important stuff.

5.1 In respect of the Lithium Iron Phosphate (LiFePO4) cells (hereinafter the Cells), the duration of
the warranty shall be 10 years or five thousand (5000) cycles (whichever comes first),
commencing on the date of sale.
5.2 For purposes of paragraph 5.1 a single cycle for the BR (Battery Rack) range is defined as a
discharge to maximum 80% depth of discharge of the batterys capacity at >C/2 (capacity at a 2
hour discharge rate or more) followed by a recharge to 100% state-of-charge at >C/2 (capacity at
a 2 hr recharge rate or more).

Do yourself a favour and make sure you understand who carries the warranty, it is passed on to you or will the person who sold the battery to you handle the claim. If you are responsible for handling the claim, best you try contact the company distributing the batteries in South Africa. Many people think that the batteries are manufactured in SA. I would verify that statement before you purchase. I am yet to find one which doesn't arrive her from the far afar away. They may designed in an office in SA, but actually built here, well show us the production line.

Once again please feel free to set the record straight if any of this information is incorrect. I am trying to find my way through a maze of bullshit.

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## Isetech

You need to read the warranty forms, the features and all that sales jargon is just that, sales jargon 


Warranty Exclusions & Terms and Conditions:

The battery has a 15 year intended design life, however the battery cells should achieve at least 5 years service life or deliver at least 3000 charge, discharge cycles as counted by the BMS, which ever event is achieved first.

 however a standard 3 year warranty is provided for the BMS 

9. If placed in storage then the ambient temperature should be no higher than 25 degrees Celsius.

24. Any damage to the battery caused by peripheral electrical equipment.
The integrated BMS module is designed to last over 15 years, however a standard 3 year warranty is provided for the BMS and all related probes and sensors.
The operating temperature for the battery is designed to be 0 to 55 degrees Celsius, however it is recommended to keep the battery below 25 degrees Celsius to maximise the design life and life cycle of the battery. The cycle life is negatively affected by temperatures above 25 degrees and cannot be guaranteed if the battery is operated in temperatures exceeding 25 degrees Celsius.

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## Isetech

This extended warranty indicates that the cells have a 10 year warranty or 6000 cycles, but also indicated a reduced period for the BMS only 5 years.

So the next question you need to ask : How are the cycles recorded, per charge and discharge no matter how short or only once a full cycle has been reached? 

Something else to note it seems all the supplier exclude labour charges and shipping. 

Another thing to consider is the total cycles per year. 


https://www.sunsynk.org/_files/ugd/50e58b_28402ba46c08406c8eb8e6bd2e141efb.pdf

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## Isetech

3.1 In respect of the Lithium Iron Phosphate (LiFePO4) cells (hereinafter the Cells), the duration ofthe warranty shall be 10 years or five thousand (5000) cycles (whichever comes first),commencing on the date of sale.

3.2 For purposes of paragraph 

3.1 a single cycle for the NG (New Generation) range is defined as adischarge to maximum 80% depth of discharge of the batterys capacity at >C/10 (capacity at a10 hour discharge rate or more) followed by a recharge to 100% state-of-charge, and a singlecycle for the HC (High Current) range is defined as a discharge to maximum 80% depth ofdischarge of the batterys capacity at >C/2 (capacity at a 2 hour discharge rate or more) followedby a recharge to 100% state-of-charge at >C/2 (capacity at a 2 hour recharge rate or more).

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## Isetech

What would you offer your customer a battery featuring 15 year life span with only a 3 year warranty on the BMS, a 5 year warranty on the cells and 3000 cycle life, which requires different software to remote view, special cables and dip settings etc? 

Or would you buy a battery which offers a 10 year warranty and 6000 cycles on the cells, a 5 year warranty on the BMS and links directly to the inverter and communicates without additional software and firmware glitches all on one app. 

It was down to the Sunsynk battery and the Blue Nova daily use battery, pretty much matched on price, but it just makes more sense to buy the battery that comes from the same supplier, has a decent warranty and communicates with the inverter. 

I think I have just made my decision, it looks like it is going to be the Sunsynk battery. Best I get those payment made so that I can get my demo model setup in my workshop. 


It might be a better option to get the customer to transfer the money directly to the supplier so they can benefit if they are VAT registered and I dont have to worry about warranty claims, then can also  charge the customer for any callouts and shipping for any warranty claims   :Wink:  

Once I know the products work, by then I will be Vat registered again, its a win win.

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## Isetech

Would the warranty of the battery not indicate the grade of the battery? 

If the cell has a 10 year warranty with 6000 cycles would that indicate a grade A battery compared to one only offering a 5 year warranty with only 3000 cycles being a grade C cell? 

From all time I have wasted doing research, I would go with credible data being featured for a 5kwh battery. A battery offering the following:

5 year BMS warranty.

10 year cell warranty or 6000 cycles 

Discharge and charge rate of 50 amps continuous and 100 amp max

Limited to 700 cycle per year. 

I would say this would be a fair way to compare apples with apples. 

If you feel I am way out the park on this, feel free to correct me supported with the technical data and warranty specs, not some bullshit feature for sales. 

Done forget to include a technical support contact number for people to contact to verify your information  :Wink:  

No matter how good a product in sale pitch, without technical support it is pretty useless.

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## Isetech

I should be ready to offer to supply and install products which will carry my personal stamp of approval, within the next 4 months, with a demo unit setup in my workshop to simulate any software or technical queries.

Now to figue out which panels will best suit the inverter. 

I have already started installing prewired essential and non essential 3 tier surface and flush DB,s with enough space to add any future EV requirements and automation using devices like the  ASC's for geysers, pool timers, security lights or any other automation.

All the automation, an be triggered by the alarm app we install  and manual switching. 

The alarm system can also trigger the automation using the alarm app or alarm keypad. 

Alarm PIRs can also trigger the security light in that specific area and send pre recorded notification to your phone from the camera linked to the PIR.

We also link the 12 VDC equipment like the CCTV, alarm, router and even 12 VDC flood lights to an independent backup systemin case everything else falls or the batteries on the main inverter backup cutout.

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## Justloadit

Just a question, with respect to this 10/15 year warranty.
What are the requirements to make the warranty claim? - Original invoice and original packaging, certificate of installation of qualified installer I suppose  :Smile: 
Are the companies even going to be in business?

All these claims made in my opinion are lip movement, the proof is in the actions when it goes south.

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## Isetech

> Just a question, with respect to this 10/15 year warranty.
> What are the requirements to make the warranty claim? - Original invoice and original packaging, certificate of installation of qualified installer I suppose 
> Are the companies even going to be in business?
> 
> All these claims made in my opinion are lip movement, the proof is in the actions when it goes south.


100%, that is the reason I still havent decided which battery yet.

I would love to hear a top 3 batteries in SA, comparing spec's and battery type and grade, new or old generation, the real information not the sales check list and features. 

Would you be getting what you pay if you spend R30 k on a battery battery compared to R25K or would a 5 year warranty be a better choice than a 3 year warranty.

Buying light fittings is just as bad, you get a 10 watt flood light with a 1 year warranty and one with a 2 year warranty, why would you pay R100 more for a light with a 2 year warranty, the lights breaks after 6 months and they indicate that there is no warranty because of the power issues in SA  :Frown: 

People are desperate and have money to waste, so in most case you can throw any crap at them and get away with it. They whine about the petrol price then go piss R150 000 against the wall on some crap system that not suitable for their application, then expect everyone  else to do it right and replace the system as a fraction of the cost.

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## Isetech

Here is an example of a company which displays the reality of selecting a lithium battery and the same size and voltage, just different cell grading. 

Note!

The warranty period 

The cycles at 80% DoD

Daily use or backup. 

We are going through an absolute stupid phase again. People going nuts, similar to when a message did the rounds that there was going to shortage.

The same thing happened when load shedding started, people went crazy buying generators, we had container loads of generators arriving, then suddenly the load shedding stopped, those containers arrived and people withdrew their orders and so a lot of people went bang, companies disappeared as fast as they arrived. 

Make sure all your orders are paid up front and the money has cleared before you order and pay for the shipment and hope that your container doesnt arrive full of sand. 

https://www.bluenova.co.za/rac-power/

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