Battery optimal charge current is higher than controller charging current

[poot_traveller]

I have a LiFePO4 battery with a optimal charge current of 50 A, and a MPPT controller with a charging current of 30 A.

I'm using the solar system to charge a laptop, and kontiki batteries which I think are 9V.

Do you think I should upgrade to a MPPT controller with a charging current of 50 A, or is a 30 A controller good enough for the battery?

It won't wreck the battery charging well below it's optimal charging current, will it?

 

[Elbear1]

Means nothing if you dont have enough panels to output 50A...like 800w

Wont hurt lithium. Would be a problem with flooded batteries.

 

[jonyjoe303]

Your lifepo4 will be ok to charge at less then 50 amps. My 220ah lifepo4 never charges at more then 12 amps, thats for the past 3 years. Actually its better to charge at lower amps, you get a better charge, if you charge at too high amps, the bms might shut down too early preventing a full charge.
At lower amps the battery surface voltage slowly goes up to 14.6 volts where the bms stops the charge, at high amps the surface voltage goes up quickly to 14.6 volts and when the bms sees 14.6 volts it stops charging, but the actual battery voltage might only be 14 volts or less.

As far as your mppt controller, you size it by your solar panels. If you have 1x 240 watt panel then you need something like a 20 amp controller since the panel won't put out more then 15 amps. If you put a 30 amp controller on the same 240 watt panel it will still work but your panel will only max at 15 amps. You spend extra money that didn't get you any extra benefits. A 50 amp controller will work also but the panel will still only put out 15 amps.

The inside of a lifepo4 battery is made up of smaller cells, my 220ah lifepo4 is made up of 160 cells ( the size of D batteries), thats why you can never damage the battery by charging at low amps, those cells prefer the lower amps.

 

[B and C]

When my current batteries do not supply my needs any longer, I am strongly leaning toward replacing them with battle born. I will be keeping my current 30a MidNite Kid MPPT controller. I have 350 Ah bank now and will probably drop that to 200 Ah. Thay give a max or suggested charge rate, not a minimum.

 

[poot_traveller]

Means nothing if you dont have enough panels to output 50A...like 800w

Wont hurt lithium. Would be a problem with flooded batteries.

That's OK, I was getting worried I'd have to buy another MPPT controller. I only got a 160 watt panel.

 

[Elbear1]

When my current batteries do not supply my needs any longer, I am strongly leaning toward replacing them with battle born.  I will be keeping my current 30a MidNite Kid MPPT controller.  I have 350 Ah bank now and will probably drop that to 200 Ah.  Thay give a max or suggested charge rate, not a minimak.

Sitting here thinking exact same. Lithium mak me drool.

 

[Elbear1]

That's OK, I was getting worried I'd have to buy another MPPT controller. I only got a 160 watt panel.

If you had a couple cheap 6v batteries youd ruin them by under charging. But you paid a premium and dont have to worry about any of that nonsense.

 

[poot_traveller]

Your lifepo4 will be ok to charge at less then 50 amps. My 220ah lifepo4 never charges at more then 12 amps, thats for the past 3 years. Actually its better to charge at lower amps, you get a better charge, if you charge at too high amps, the bms might shut down too early preventing a full charge.
At lower amps the battery surface voltage slowly goes up to 14.6 volts where the bms stops the charge, at high amps the surface voltage goes up quickly to 14.6 volts and when the bms sees 14.6 volts it stops charging, but the actual battery voltage might only be 14 volts or less.

That's good to hear. I don't really want to be doing any damage to the battery. If the battery lasts me 3 years, I'm happy with that.

 

[poot_traveller]

As far as your mppt controller, you size it by your solar panels. If you have 1x 240 watt panel then you need something like a 20 amp controller since the panel won't put out more then 15 amps. If you put a 30 amp controller on the same 240 watt panel it will still work but your panel will only max at 15 amps. You spend extra money that didn't get you any extra benefits. A 50 amp controller will work also but the panel will still only put out 15 amps.

I have a 160 watt panel and 30 A controller, if I payed little extra for nothing....so be it, I can live with that. 

You should see my "trial and error bill" for this van build, it's enough to make people gasp in horror.  But ya live and learn

 

[Elbear1]

We all been there!

 

[poot_traveller]

If you had a couple cheap 6v batteries youd ruin them by under charging. But you paid a premium and dont have to worry about any of that nonsense.

Sweet

 

[regis101]

“I have a 160 watt panel and 30 A controller, if I payed little extra for nothing....so be it, I can live with that. ”

Think of it as making room fir expansion

 

[Giuseppe Hardblast]

I was reading up on battleborn lithium batteries and the 3000 cycles rating they claim for thier batteries is calculated by charging and discharging at 100 amps at 100%.

Your lithium should be fine. Like others said, your panels need to be able to output that many amps. Which if I remember correctly, yours dont. Edit: yea a 160w panel will not do that. I would probably recommend if anything on your system is to get more panels first.

50a is the optimal recommendation. But I'm designing a system that will be at 75a. This is only temporary though because i plan on further expanding my system to 24v and when that happens the batteries will be charging at half of that which is approximately 40amps and would really be the ideal situation.

 

[Giuseppe Hardblast]

At that point I could maybe add another 300w panel but I'll have to see if it's possible. I'll be pushing the limits of my rooftop real estate.

 

[poot_traveller]

“I have a 160 watt panel and 30 A controller, if I payed little extra for nothing....so be it, I can live with that. ”

Think of it as making room fir expansion

Yes. The panel has a short circuit of 9.5A. So I guess it has lots of room for expansion.

 

[poot_traveller]

I was reading up on battleborn lithium batteries and the 3000 cycles rating they claim for thier batteries is calculated by charging and discharging at 100 amps at 100%.

Your lithium should be fine. Like others said, your panels need to be able to output that many amps. Which if I remember correctly, yours dont. Edit: yea a 160w panel will not do that. I would probably recommend if anything on your system is to get more panels first.

50a is the optimal recommendation. But I'm designing a system that will be at 75a. This is only temporary though because i plan on further expanding my system to 24v and when that happens the batteries will be charging at half of that which is approximately 40amps and would really be the ideal situation.

This is the panel specifics:

Max Power (VMP) 17.8V

Max Power Current (Imp) 9.0A

Open Circuit: (Voc) 21.1V

Short Circuit: (Isc) 9.5A

Max Sys Voltage: DC1000V

 

[poot_traveller]

At that point I could maybe add another 300w panel but I'll have to see if it's possible. I'll be pushing the limits of my rooftop real estate.

Yes, I'd also be pushing the limits of my rooftop space. In fact, I probably can't fit another panel on the roof....although where there is a will, there is a way.

 

[Giuseppe Hardblast]

You have one 160w panel? What are you driving?

 

[poot_traveller]

You have one 160w panel? What are you driving?

Yep just one 160 watt panel.

I'm driving a 1999 Toyota Hiace:

 

[billy.turnstile]

I have a LiFePO4 battery with a optimal charge current of 50 A, and a MPPT controller with a charging current of 30 A.

I'm using the solar system to charge a laptop, and kontiki batteries which I think are 9V.

Do you think I should upgrade to a MPPT controller with a charging current of 50 A, or is a 30 A controller good enough for the battery? 

It won't wreck the battery charging well below it's optimal charging current, will it?