Battery storage for solar

[Powerguy]

Hi all
posted before I’m on a small farm with solar already but grid tied . I’m thinking of using forklift batteries as my storage source my questions are this - I’m wanting about 48kwh usable power I was thinking 24 cells at 2v 1240 ah batteries using the formula volts x ah divided 1000 giving me about 59 kWh taking off 20 percent as you can’t fully discharge a battery . The battery bank would be connected is series , have I worked this out right , I would be charging with 16kw of panels and using 2 8kw sunsykn inverters. The batteries are expensive and have seen used batteries at 930 with a year warranty but would fail to get the storage is there where parallel connecting would come in or series parallel? And am I right in thinking that I could keep the volts the same and increase storage ? And what would the formula be to work out kWh? ( to add all the volts up as before ?
thanks Roger

 

[Ucatchmydrift]

Hi all
posted before I’m on a small farm with solar already but grid tied . I’m thinking of using forklift batteries as my storage source my questions are this - I’m wanting about 48kwh usable power I was thinking 24 cells at 2v 1240 ah batteries using the formula volts x ah divided 1000 giving me about 59 kWh taking off 20 percent as you can’t fully discharge a battery . The battery bank would be connected is series , have I worked this out right , I would be charging with 16kw of panels and using 2 8kw sunsykn inverters. The batteries are expensive and have seen used batteries at 930 with a year warranty but would fail to get the storage is there where parallel connecting would come in or series parallel? And am I right in thinking that I could keep the volts the same and increase storage ? And what would the formula be to work out kWh? ( to add all the volts up as before ?
thanks Roger

Dont even bother with lead acid, they would last you about 2 years discharging to 50%, you can only really discharge them 20% meaning you loose 80% of thieir capacity, then they MAY last you 6-10 years if your Very lucky. Then you have to charge them all up to the max each time. Not practical for energy storage unless they are free, but even then, id be selling them and just buying eve lifep04 cells and build my own. Much cheaper and far far better.

 

[offgridAndy]

Whilst I'd agree that in 2023. if your budget can run to it, then LiFePo4 cells will build a high quality battery; lead acid cells are still very good and on the face of about half the price.

My last quote for 48Kw battery (lead acid) was from Ecobat, for 8 plate EPS 720Ahr cells. A 48V system was priced at £3360 plus VAT, ie 24 cells in series.

My real life experience on lead acid batteries is rather different from Ucatchmy drift. I have lived of grid for over 22 years and currently have 24Kw battery 24 v 1000Ahr. First battery was replaced after 12 years .

I charge my battery up to 29.4V and discharge down to 22.2 v. Lead acid is much less fussy then LiPo and can handle over discharge and over charge with out suffering damage unlike LiPo. So the inverter doesn't turn it self off even if the battery voltage goes out of range.,

I rarely use the generator as we have sufficient RE that the battery can spend days around 24 to 27V neither fully charged or discharged. But when the genny runs I usually turn it of at about 28V as I know that there is going to be some RE along to keep the battery topped up.

When you read up on LA battery use you will find reference to holding the cells at a high voltage (29.2V) for an hr or to for absorb charge followed by a float charge rate. Whhen I asked the battery manufacturer about this, they had another view. These batteries are design for regular deep discharge and hard recharge go and see how fork lifts arre operated in the course of a day. They don't park up and stop work after a couple of hrs. Worked hard a set of cells in a fork lift have a predicted life of 5 years.

So in my opinion based on real life experience lead acid batteries have a place in the world. BUT don't buy second hand. You will regret it.

 

[MikeJhn]

LiPo batteries are "Lithium Polymer" and totally unsuitable, soft case and a fire hazard if over charged, LiFePo4 as they have generically been called now are "Lithium Iron" and a different chemistry, if you want to abbreviate use LiFe the Po4 was added by the Chinese when they ripped off the originator of the chemistry.

 

[Ucatchmydrift]

Whilst I'd agree that in 2023. if your budget can run to it, then LiFePo4 cells will build a high quality battery; lead acid cells are still very good and on the face of about half the price.

My last quote for 48Kw battery (lead acid) was from Ecobat, for 8 plate EPS 720Ahr cells. A 48V system was priced at £3360 plus VAT, ie 24 cells in series.

My real life experience on lead acid batteries is rather different from Ucatchmy drift. I have lived of grid for over 22 years and currently have 24Kw battery 24 v 1000Ahr. First battery was replaced after 12 years .

I charge my battery up to 29.4V and discharge down to 22.2 v. Lead acid is much less fussy then LiPo and can handle over discharge and over charge with out suffering damage unlike LiPo. So the inverter doesn't turn it self off even if the battery voltage goes out of range.,

I rarely use the generator as we have sufficient RE that the battery can spend days around 24 to 27V neither fully charged or discharged. But when the genny runs I usually turn it of at about 28V as I know that there is going to be some RE along to keep the battery topped up.

When you read up on LA battery use you will find reference to holding the cells at a high voltage (29.2V) for an hr or to for absorb charge followed by a float charge rate. Whhen I asked the battery manufacturer about this, they had another view. These batteries are design for regular deep discharge and hard recharge go and see how fork lifts arre operated in the course of a day. They don't park up and stop work after a couple of hrs. Worked hard a set of cells in a fork lift have a predicted life of 5 years.

So in my opinion based on real life experience lead acid batteries have a place in the world. BUT don't buy second hand. You will regret it.

I looked into the lead acid stuff before going for lifepo4 (lithium iron phosphate), and your experience seems to be quite unique.

"Lead acid is much less fussy then LiPo and can handle over discharge and over charge with out suffering damage unlike LiPo. So the inverter doesn't turn it self off even if the battery voltage goes out of range."

^^^^^Are you talking lipo or lifepo4? Lipos are not used (by the vast majority) for energy storage, more suited to model cars and the like, fast discharge etc, and yes, will catch fire and get damaged from over charging etc.
Lifepo4 is a much safer chemistry, and hence generally very safe.
Lead acid is FAR FAR more fussy about discharging below about 50% than a lifep04. The inverter turns off when its set to turn off. You get to use about 20% of the actual capacity of a lead acid if you want them to last more than 5 years. Lifep04 should be able to handle using 90% of its actual capacity and may last for 20 years, discharging and charging at high rates. You cant use 50% of a lead acid, then put 10% charge in, then discharge 10% etc etc else your battery will last about 2 years. This is well known info by both users and manufacturers.
I would guess that after 12 years, your lead acids would have about 50% of their original capacity or less, vs lifepo4 70-80% after 6000 cycles. Unless your only using a very small amount of their capacity each day, which must be the case... So like i said, maybe your forklift batteries are special in some way, but deep cycle lead acids are usually just starter batteries re labeled. Have you a link for 48kw for £3300? - as normally would cost far far more than that. My 14.4kw cost me £2500 for lifepo4 grade a eve cells which is very cheap for lifepo4 (diy).

 

[johnb2713]

Lead acid is much less fussy then LiPo

Generally were not talking about LiPo but LifeP04 which are very different batteries. I'm dont agree with your 'fussy' assessment of LifeP04 batteries, they have precise limits which all equipment is configured to deal with so not a big deal either.

and can handle over discharge and over charge with out suffering damage

That really is not true, talk to any caravanner about lead acid leisure batteries and they do suffer terribly, usually with over discharge but over charging also features in failures when 3 stage chargers go wrong, the failure is at times catastrophic too with explosive gasses and failing electrics - BOOM.

So the inverter doesn't turn it self off even if the battery voltage goes out of range.,

Thats not a good thing.

So in my opinion based on real life experience

How much of that experience is with LifeP04 batteries or is it only Lead Acid that youve used?

lead acid batteries have a place in the world.

They do but not really for this application.

 

[offgridAndy]

All of my comments are based on real life experience with lead acid batteries. That is to say genuine traction batteries. Ie 8EPZS1000L C5 rating. I'm not referring to caravan liesure batteries which are a different kettle of fish.

I should point out that living off grid for us is not squating in a bender with a couple of lights. House is about 2500sq ft 3 bed. We use approx 10Kw per day having 2 deep freezes, fridge dish washer washing machine etc, run a business from home 3 computers on all day plus lights. Run a welder in the garage etc just like normal life with out the utility bills.

LA batteries do need to be kept watered clean and dry but will also work at lower temperatures. I've only done this for 20 plus years so when I've got more experience I may modify my views.

 

[Ucatchmydrift]

All of my comments are based on real life experience with lead acid batteries. That is to say genuine traction batteries. Ie 8EPZS1000L C5 rating. I'm not referring to caravan liesure batteries which are a different kettle of fish.

I should point out that living off grid for us is not squating in a bender with a couple of lights. House is about 2500sq ft 3 bed. We use approx 10Kw per day having 2 deep freezes, fridge dish washer washing machine etc, run a business from home 3 computers on all day plus lights. Run a welder in the garage etc just like normal life with out the utility bills.

LA batteries do need to be kept watered clean and dry but will also work at lower temperatures. I've only done this for 20 plus years so when I've got more experience I may modify my views.

If your using about 10kw a day, with a 48kw bank, that equates to about 20% usage of the capacity of the battery each day, hence why they lasted 12 years, although i suspect they would not have much capacity left after this time, wheres a lifep04 would still be going strong for probably another 10 years, based on a much smaller and cheaper battery bank.
But what you said about lifepo4 is not very accurate. I guarantee if you went with lifepo4 you wouldnt look back... Yes, they are a bit more technical to set up, but once done, its Set and forget...

 

[offgridAndy]

I have lived of grid for over 22 years and currently have 24Kw battery 24 v 1000Ahr. First battery was replaced after 12 year

We are using about 50% discharge allowing for inefficiency rate.

All of my comments are about LA batteries.

I will indeed be changing to LiPo battery in the future as I recognise the benfits and can now afford the investment but I still stand by my comment LA batteries having there place in the RE world.

I charge my battery up to 29.4V and discharge down to 22.2 v. Lead acid is much less fussy then LiPo and can handle over discharge and over charge with out suffering damage unlike LiPo. This is true. as is the fact that LiPo can be damaged by over and under charging and in the real world inverter/chargers can fail or be set up incorrectly.

You cant use 50% of a lead acid, then put 10% charge in, then discharge 10% etc etc else your battery will last about 2 years. Sorry but this is totally wrong.

For the benefit of the OP if you wish to purchase LA cells I personally have dealt direct with the manufacturer. The used to trade as ManBat but are now called Ecobat. They are the largest lead processor in Europe. I simply phoned the sales rep and got prices then placed an order no problem And trade prices too.

You will need 24 Nos 2.2V cells @ 1000 C5Ahr capacity all connected in series to give nominal 48V battery which givess 48Kwh capacity. I personally use Outback charge controllers and inverter. Their design is a bit dated now but very reliable. 100amp charging rate is available with 150V DC max input from the PV string.

 

[binky]

OK, I think we have discussed the ops battery choice enough, anyone care to answer his actual question .

 

[johnb2713]

All of my comments are based on real life experience with lead acid batteries. That is to say genuine traction batteries. Ie 8EPZS1000L C5 rating. I'm not referring to caravan liesure batteries which are a different kettle of fish.

I should point out that living off grid for us is not squating in a bender with a couple of lights. House is about 2500sq ft 3 bed. We use approx 10Kw per day having 2 deep freezes, fridge dish washer washing machine etc, run a business from home 3 computers on all day plus lights. Run a welder in the garage etc just like normal life with out the utility bills.

LA batteries do need to be kept watered clean and dry but will also work at lower temperatures. I've only done this for 20 plus years so when I've got more experience I may modify my views.

I don’t doubt your experience with lead acid batteries I do doubt your wisdom in comparison to LifeP04.
Lead acid no matter which flavour, leisure, traction, C5 or whatever ALL are damaged by over discharging or over charging.
It’s great that your experience has been good and is real accolade for lead acid, from what said though in terms of battery size it is relatively light use.

 

[Powerguy]

OK, I think we have discussed the ops battery choice enough, anyone care to answer his actual question .

Thank you for all your input guys , rightly or wrong I have gone down the lead acid route going for 2v lead acid traction batteries 775ah . Going for 48 cells wired in parallel series giving me 48v . Opted for a watering system for them too. Will let you know how I get on . Fingers crossed the system should be fitted in the next month

 

[binky]

Thank you for all your input guys , rightly or wrong I have gone down the lead acid route going for 2v lead acid traction batteries 775ah . Going for 48 cells wired in parallel series giving me 48v . Opted for a watering system for them too. Will let you know how I get on . Fingers crossed the system should be fitted in the next month

Do please report back, lead acid batteries have been around for a very long time, so they do offer a tried and tested technology.

 

[johnb2713]

Thank you for all your input guys , rightly or wrong I have gone down the lead acid route going for 2v lead acid traction batteries 775ah . Going for 48 cells wired in parallel series giving me 48v . Opted for a watering system for them too. Will let you know how I get on . Fingers crossed the system should be fitted in the next month

Interesting project for sure, please do a thread on the build and operation.