Replace Lead Carbon bats with LiFePO4, new inverter needed too?

[Penoffgrid]

Hello all, this is my first post, I am very new to this, so any advice greatly appreciated!

I bought some land with an off grid PV system already installed by a pro. Unfortunately in ignorance I think we have wrecked the Lead Carbon batteries by allowing them to discharge too low (I thought there would have been some sort of cut off, but apparently not). Now they do not hold charge well and the system can only just about run a light bulb without cutting out. I put the volt meter on each one when a load was turned on and there was a huge drop so I assume they have had it.,.

This is what we currently have, and I would like to replace the batteries with LiFePo4 ones, but I think this may also require a new inverter.

• 6 x LG Neon 2 (giving a total of 2010watts or 2.01kw maximum power.
• 1 x 5kw combi inverter (IC2 -KMS)
• 4 x 170ah 12v lead carbon batteries

The original installer quoted around £8000 K GBP to covert to LiFePo4, but this seems hugely expensive, since I have seen batteries for much less than this online, so I would like to try to source them and do the install myself. However, now I see from the inverter manual that it states only lead acid batteries be used. So I really need some advice please! I am a bit scared!

Many thanks indeed for your help

 

[MichaelK]

A word of warning to you. Li in a bit more tolerant to deep discharging, but Li still shares the same kind of discharge profile as traditional lead-acid, meaning the battery life goes down drastically as the discharge rate goes up. So, don't fool yourself into thinking that Li is going to solve all your problems. You are still going to be hands-on to determine your depth of discharge to prevent serious loss of battery life. Your system most likely can be calibrated to Li though with custom programing of the charge voltages. That will be documented by the battery manufacturer.

This was for a 48V system? I would consider 170Ah small for 48V, barely adequate. I would want at least 400Ah at 48V. I would consider also upgrading the panels to at least 3500W, and 4000+ would be better. For my own 48V system, I still utilize lead-carbon batteries, which are still in "like new" condition. And they are 568Ah. My primary arrays are 4500W total.

So, I'd say what you really need are bigger batteries, more solar, and more attention.

 

[Samsonite801]

Hello all, this is my first post, I am very new to this, so any advice greatly appreciated!

I bought some land with an off grid PV system already installed by a pro. Unfortunately in ignorance I think we have wrecked the Lead Carbon batteries by allowing them to discharge too low (I thought there would have been some sort of cut off, but apparently not). Now they do not hold charge well and the system can only just about run a light bulb without cutting out. I put the volt meter on each one when a load was turned on and there was a huge drop so I assume they have had it.,.

This is what we currently have, and I would like to replace the batteries with LiFePo4 ones, but I think this may also require a new inverter.

• 6 x LG Neon 2 (giving a total of 2010watts or 2.01kw maximum power.
• 1 x 5kw combi inverter (IC2 -KMS)
• 4 x 170ah 12v lead carbon batteries

The original installer quoted around £8000 K GBP to covert to LiFePo4, but this seems hugely expensive, since I have seen batteries for much less than this online, so I would like to try to source them and do the install myself. However, now I see from the inverter manual that it states only lead acid batteries be used. So I really need some advice please! I am a bit scared!

Many thanks indeed for your help

Do you have the manual or specs sheet for that inverter? (I can't seem to find it based on searching the model indicated)

Assuming it is an all-in-one with a charge controller built into it? Does it have a user-adjustable custom battery charge profile? Is the inverter low-voltage shutoff user-definable in settings?

 

[Penoffgrid]

Thanks very much for the replies. Sorry, I should have been clearer- there are 4 12v bats in series, each are 170ah.

I did find the manual online - here: https://www.photonicuniverse.com/en...-parallel-capability-No-Battery-Required.html

We will not require a heavy use. Just charging mobile phones and laptops, a few led lights, but occasionally also to power the onboard caravan water heater and a small cooler. We do not live at the site all the time.

Thanks so much for your advice

 

[Samsonite801]

Thanks very much for the replies. Sorry, I should have been clearer- there are 4 12v bats in series, each are 170ah.

I did find the manual online - here: https://www.photonicuniverse.com/en...-parallel-capability-No-Battery-Required.html

We will not require a heavy use. Just charging mobile phones and laptops, a few led lights, but occasionally also to power the onboard caravan water heater and a small cooler. We do not live at the site all the time.

Thanks so much for your advice

It does look like you can customize charge cycle voltages on a custom user profile (to make proper profile for LFP/LiFePO4), and it also supports setting a custom low voltage shutoff point on the inverter...

"- A range of highly customisable settings:
The parameters for this inverter can be personalised to an exceptionally specific degree via the user-friendly interface. At the touch of a button, the user can customise parameters such as the AC input range, battery type, max charging current, specific high/low voltage disconnect points (and preferred charging source upon reconnection), the duration and voltage of each charging stage, auto-restart options, power saving mode, overload bypass, battery equalization stage characteristics and so on. There are also options for managing operational features such as the audible alarm and backlight settings."

There is a sticky thread here on setting the battery charge and inverter shutoff parameters for LFP/LiFePO4 batteries:

Recommended Charge Profile for DIY LiFePO4 Batteries *Sticky Post*

12V 4S LiFePO4 Battery w/ BMS: Absorption: 14.5V Float: 13.6V Inverter Cut-off: 10.7V-12V (depending on size of load and voltage drop etc) 24V 8S LiFePO4 Battery w/ BMS Absorption: 29V Float: 27.2V Inverter Cut-off: 21.4V-24V 48V 16S LiFePO4 Battery w/ BMS Absorption: 58V Float: 54.4V...

diysolarforum.com

One think to consider, if your cabin is in area prone to freezing temperatures, LFP/LiFePO4 can't be charged below freezing (without damaging cells), so you need to make sure the battery you buy has a BMS with low-temp (freezing) cutoff capability, and you may want to get an internally-heated battery, or add a heater pad / thermostat, insulation box, etc, some means to keep battery above freezing, so you can charge in freezing environment.

The BMS is the last line of defense so it should halt charging at freezing or below (if is a good BMS), but the heater pad would be a way to stay operational despite freezing temps.

If that is too much trouble, then could go the simple way and just get an AGM battery replacement or something. If you set the inverter low-volts cutoff to a correct voltage point, it would shut off the inverter before the battery can ever run too low (below low threshold). Typical lead battery chemistries shouldn't be run lower than 50% SoC... For LFP/LiFePO4 chemistries it's no lower than about 14% SoC...

 

[Penoffgrid]

It does look like you can customize charge cycle voltages on a custom user profile (to make proper profile for LFP/LiFePO4), and it also supports setting a custom low voltage shutoff point on the inverter...

"- A range of highly customisable settings:
The parameters for this inverter can be personalised to an exceptionally specific degree via the user-friendly interface. At the touch of a button, the user can customise parameters such as the AC input range, battery type, max charging current, specific high/low voltage disconnect points (and preferred charging source upon reconnection), the duration and voltage of each charging stage, auto-restart options, power saving mode, overload bypass, battery equalization stage characteristics and so on. There are also options for managing operational features such as the audible alarm and backlight settings."

There is a sticky thread here on setting the battery charge and inverter shutoff parameters for LFP/LiFePO4 batteries:

Recommended Charge Profile for DIY LiFePO4 Batteries *Sticky Post*

12V 4S LiFePO4 Battery w/ BMS: Absorption: 14.5V Float: 13.6V Inverter Cut-off: 10.7V-12V (depending on size of load and voltage drop etc) 24V 8S LiFePO4 Battery w/ BMS Absorption: 29V Float: 27.2V Inverter Cut-off: 21.4V-24V 48V 16S LiFePO4 Battery w/ BMS Absorption: 58V Float: 54.4V...

diysolarforum.com

One think to consider, if your cabin is in area prone to freezing temperatures, LFP/LiFePO4 can't be charged below freezing (without damaging cells), so you need to make sure the battery you buy has a BMS with low-temp (freezing) cutoff capability, and you may want to get an internally-heated battery, or add a heater pad / thermostat, insulation box, etc, some means to keep battery above freezing, so you can charge in freezing environment.

The BMS is the last line of defense so it should halt charging at freezing or below (if is a good BMS), but the heater pad would be a way to stay operational despite freezing temps.

If that is too much trouble, then could go the simple way and just get an AGM battery replacement or something. If you set the inverter low-volts cutoff to a correct voltage point, it would shut off the inverter before the battery can ever run too low (below low threshold). Typical lead battery chemistries shouldn't be run lower than 50% SoC... For LFP/LiFePO4 chemistries it's no lower than about 14% SoC...

Thank you very much for your reply. I’ll look into how to customise settings in the thread you mention

 

[Penoffgrid]

So my next question would be, which batteries are considered good (but not astronomically expensive) in the UK, that can be run in series? The Renogy ones I have seen an only be used in parallel ....

But, why am i tied to 48V anyway? What would be the disadvantage to running 4 in parallel? e.g 12v @ 100Ah?
Sorry for the basic questions

 

[Samsonite801]

So my next question would be, which batteries are considered good (but not astronomically expensive) in the UK, that can be run in series? The Renogy ones I have seen an only be used in parallel ....

But, why am i tied to 48V anyway? What would be the disadvantage to running 4 in parallel? e.g 12v @ 100Ah?
Sorry for the basic questions

If you run 48v LFP batteries though, each BMS on a battery balances all of its own cells as a single array. If you run 4x 12v LFP batteries, only sets of 4 cells will balance by their respective BMS's, but the groups of 4 would not be guaranteed to stay in balance. For simplicity I would prefer to just get or build 48v (16s) packs.

Do you have a preference for turn-key blackbox battery solution or is a DIY option something you might be open to? You might check out the battery storage threads here as well as far as brands. The Seplos batteries to me look promising for a turn-key solution. I know Pylontech batteries seem somewhat popular in Europe... I went all DIY with my batteries anyways.

Also might not hurt to know what your budget is like, how many KWh you need...

 

[Penoffgrid]

If you run 48v LFP batteries though, each BMS on a battery balances all of its own cells as a single array. If you run 4x 12v LFP batteries, only sets of 4 cells will balance by their respective BMS's, but the groups of 4 would not be guaranteed to stay in balance. For simplicity I would prefer to just get or build 48v (16s) packs.

Do you have a preference for turn-key blackbox battery solution or is a DIY option something you might be open to? You might check out the battery storage threads here as well as far as brands. The Seplos batteries to me look promising for a turn-key solution. I know Pylontech batteries seem somewhat popular in Europe... I went all DIY with my batteries anyways.

Also might not hurt to know what your budget is like, how many KWh you need...

Thank you for your advice, that’s really helpful. I had seen the PylonTech ones but wasn’t sure of their quality. They seem quite hard to find at the moment but this company do them, though out of stock currently. I guess I could start with one than add another in Parallel when funds permit.
https://energymonkey.co.uk/product/pylon-us3000-3-5kwh-lifepo4-solar-battery/

I have done an energy audit using the excel file and I think we would need max 3kw storage. We do have a petrol generator if we need to top up (essential in the winter at our latitude)

 

[Penoffgrid]

@Samsonite801 , I spoke to a supplier of that PylonTech 48v LiFePO4 batteries in the UK because on their website it said this battery was only compatible with ‘tier 1’ inverters. I asked what this meant and why it had limited compatibility. He said it was to do with the BMS communication between battery and inverter. So it looks like I would need to get a new inverter in order to use one of these batteries. Do you think this sounds correct? Would it be the same issue if I used 4 x 12v in series? Is it only lithium batteries that have BMS?

 

[Samsonite801]

@Samsonite801 , I spoke to a supplier of that PylonTech 48v LiFePO4 batteries in the UK because on their website it said this battery was only compatible with ‘tier 1’ inverters. I asked what this meant and why it had limited compatibility. He said it was to do with the BMS communication between battery and inverter. So it looks like I would need to get a new inverter in order to use one of these batteries. Do you think this sounds correct? Would it be the same issue if I used 4 x 12v in series? Is it only lithium batteries that have BMS?

Yeah, inverter communication is a luxury and not a basic requirement. Usually what it gives the inverter / battery is a way for the battery to report State of Charge to the inverter, and set charging to work more based off SoC and not just control charging based on voltages. I know the MPP Solar / Voltronic inverters support Pylontech BMS communication protocol for sure.

Without communication, you have to log into the BMS by other means to read SoC, and the charging would be set to generic (preset), or user defined custom profile based on charging cycle voltages... Not a real bad thing, but I generally tout that it can be cool to have the BMS communication working if it's reasonably possible.

You might want to learn about the advantages of it prior to making a battery purchase...

 

[midahar]

Hello all, this is my first post, I am very new to this, so any advice greatly appreciated!

I bought some land with an off grid PV system already installed by a pro. Unfortunately in ignorance I think we have wrecked the Lead Carbon batteries by allowing them to discharge too low (I thought there would have been some sort of cut off, but apparently not). Now they do not hold charge well and the system can only just about run a light bulb without cutting out. I put the volt meter on each one when a load was turned on and there was a huge drop so I assume they have had it.,.

This is what we currently have, and I would like to replace the batteries with LiFePo4 ones, but I think this may also require a new inverter.

• 6 x LG Neon 2 (giving a total of 2010watts or 2.01kw maximum power.
• 1 x 5kw combi inverter (IC2 -KMS)
• 4 x 170ah 12v lead carbon batteries

The original installer quoted around £8000 K GBP to covert to LiFePo4, but this seems hugely expensive, since I have seen batteries for much less than this online, so I would like to try to source them and do the install myself. However, now I see from the inverter manual that it states only lead acid batteries be used. So I really need some advice please! I am a bit scared!

Many thanks indeed for your help

I don't the back the inverter wouldn't be any different for the lead acid or carbon lead or or lithium it doesn't matter of the the chemistry it just matters the power density

 

[midahar]

Hello all, this is my first post, I am very new to this, so any advice greatly appreciated!

I bought some land with an off grid PV system already installed by a pro. Unfortunately in ignorance I think we have wrecked the Lead Carbon batteries by allowing them to discharge too low (I thought there would have been some sort of cut off, but apparently not). Now they do not hold charge well and the system can only just about run a light bulb without cutting out. I put the volt meter on each one when a load was turned on and there was a huge drop so I assume they have had it.,.

This is what we currently have, and I would like to replace the batteries with LiFePo4 ones, but I think this may also require a new inverter.

• 6 x LG Neon 2 (giving a total of 2010watts or 2.01kw maximum power.
• 1 x 5kw combi inverter (IC2 -KMS)
• 4 x 170ah 12v lead carbon batteries

The original installer quoted around £8000 K GBP to covert to LiFePo4, but this seems hugely expensive, since I have seen batteries for much less than this online, so I would like to8 try to source them and do the install myself. However, now I see from the inverter manual that it states only lead acid batteries be used. So I really need some advice please! I am a bit scared!

Many thanks indeed for your help

I don't the back the inverter wouldn't be any different for the lead acid or carbon lead or or lithium it doesn't matter of the the chemistry it just matters the power density I believe carbon leads like the next thing and we need some sort of a cut-off device to keep us from over if it specifies lead acid batteries then it must be because the parameters that it works with are designed for lead acid charging Cycles discharging Cycles otherwise it's not going to matter just as long as you got power going into the inverter