LiFeP04 Batteries for Solar & BMS

[karrak]

This not what the EV / Grid Charging Bottom Balancer's want to hear. They drive their EV, take it home and plug it in and charge it, unplug and it's left until they drive it again. They have no parasitic loads and no floating, they have no standby soc to worry about.

Another issue is that some here do not know or understand the features of the equipment used for Solar Charging and how it functions.

I'll second that.

Good on you for putting up with the abuse

Simon

[Willy T]

Also, to charge until one cell hits 3.45 (or whatever) volts, then stop the charge source is impractical in an off-grid application. You need to have the charge controller match the load as best as possible once your cells hit your chosen top voltage. (ie. zero net current from charge controller and loads)

This not what the EV / Grid Charging Bottom Balancer's want to hear. They drive their EV, take it home and plug it in and charge it, unplug and it's left until they drive it again. They have no parasitic loads and no floating, they have no standby soc to worry about.

Another issue is that some here do not know or understand the features of the equipment used for Solar Charging and how it functions.

As far as it goes for Top or Bottom balancing they argue and fight about it in every thread on the DIY EV forums same as they do here.

[tom rickard]

Maybe the rumors of failed cells you have heard of have also come from rival manufacturers?

I have a few comments on this thread having been one of the people that has been using LFP cells in a house bank as a stand alone power supply for over 3 years.

Bottom balancing: Great for EV's where you want to take the cells close to zero charge.

It would also be fine for off-grid solar application except that the batteries do not stay balanced for prolonged periods of time. To say that you bottom balance your cells once, then run your system for the next 10 years with no difference in performance from the cells is pretty far fetched.

Also, to charge until one cell hits 3.45 (or whatever) volts, then stop the charge source is impractical in an off-grid application. You need to have the charge controller match the load as best as possible once your cells hit your chosen top voltage. (ie. zero net current from charge controller and loads)

The charge controller I use has an algorithm that reduces the charge current in a no-load situation when the first cell hits a pre-set voltage, then "balances" or shunts current at a charge current of less than 5A, tapering to zero amps. In practice, it is rare to have a no-load situation in an off-grid situation, there is always a fridge etc. chugging away.

In reality, the cells aren't being balanced when the shunts are in action, as the voltage setpoint is below the 100% SOC voltage of the cells. What is actually happening is that the charge current is being limited in a feedback situation from the shunts when there is no load on the cells. This happens at a voltage setpoint that is programmable.

To balance the cells if you feel the need, they need to be taken to a voltage of 3.6V (approx.)

So... Until you can explain how you manage to make your cells behave in an identical fashion over their lifespan, and also explain how to manage the charge controller so that it matches the load current in a fully charged situation, then I don't think bottom balancing is for me..

[karrak]

Simon - That is meaningless - you got replies from battery manufacturers for all you know.

I have read enough posts from the three others in this sample to know that they are not battery manufacturers but real people who have installed real power systems where the LFP batteries are charged from solar panels. Not a big sample, maybe we have all been lucky and this sample doesn't match the quality of LFP cells manufactured in China going to the rest of the world.

Simon

[russ]

I did a quick survey on another forum of people who charge their LFP batteries from solar power.

The oldest batteries were installed around three years ago, with the majority being installed around two years ago.

I got replies from 4 people who have installed around 150 cells with an energy storage of over 100kWh in around 7 systems. Of those 150 Chinese made cells there has been 1 replaced under warranty and no other failures.

Simon

Simon - That is meaningless - you got replies from battery manufacturers for all you know.

[karrak]

What I read is defects usually exhibit themselves early, and Chi-Com cells have their share of defects.

I did a quick survey on another forum of people who charge their LFP batteries from solar power.

The oldest batteries were installed around three years ago, with the majority being installed around two years ago.

I got replies from 4 people who have installed around 150 cells with an energy storage of over 100kWh in around 7 systems. Of those 150 Chinese made cells there has been 1 replaced under warranty and no other failures.

Simon

[Living Large]

It is just a fact that mechanical and electrical are prone to defects and does not take long for them to surface after being put into service.

Hence the folly, from an economic standpoint, of extended warranties for most products.

[Sunking]

Language likes this reminds me of to 60s and 70s, when the same sort of comments were made about the Japanese and their products.

It was true back then until Japan was fully developed. The Japanese had to go to the USA to learn quality control. They earned their reputation.

[Sunking]

Why should problems occur in just the first few months?

That holds true for any manufactured product. In the USA we have Lemon Laws. It is just a fact that mechanical and electrical are prone to defects and does not take long for them to surface after being put into service.

[Living Large]

Language likes this reminds me of to 60s and 70s, when the same sort of comments were made about the Japanese and their products. How is the American car industry going these days? Who is the largest car manufacturer in the world.

Simon

I don't think the two industries are comparable, and as a reader I didn't take that comment as an insult as much as a fact from empirical evidence.

What I read is defects usually exhibit themselves early, and Chi-Com cells have their share of defects.

[karrak]

Any battery manufacture defect is going to show up by then which does happen with Chi-Com cells.

Language likes this reminds me of to 60s and 70s, when the same sort of comments were made about the Japanese and their products. How is the American car industry going these days? Who is the largest car manufacturer in the world.

Simon

[karrak]

Depends on what the users is comfortable with and how much money you are willing to throw into Automation.

Most are minimalist...

Would you recommend this approach and do you use it?

If something is going to go wrong, it is going to happen within the first month or two.

Why should problems occur in just the first few months?

Simon

[Sunking]

lol, wrong hemisphere.

Australian. That explains a lot.

[Willy T]

What do you want to bet that was you, back under a different username there Tasman. He got banned for suggesting unsafe installation practices like you have been warned about. Care to have the moderators compare IP Addresses?

lol, wrong hemisphere.

[Sunking]

Be careful, the last off grid person got banned for talking about their system and being called a lot of names.

What do you want to bet that was you, back under a different username there Tasman. He got banned for suggesting unsafe installation practices like you have been warned about. Care to have the moderators compare IP Addresses?