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Adding new batteries to existing bank of batteries


David1SA

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Hi All,

 

Apologies for the basic question. I have a simple 8kw Inverter/UPS with 4x 200ah batteries at my house. This has been working well as backup power for the past 5 years.

The long term goal is to replace this system with an 8kw hybrid Sunsynk, 16 panels and 20kwh of batteries. (i have been running an efergy monitor for 2 months to see exactly what i need).

While my current system has served its purpose, the batteries are lasting now less than the 2 hours of loadshedding. I unfortunately do not have the means to outlay the 200k+ required for the sunsynk system. I am looking to get additional batteries or replace my current ones.

The questions:

1) My current 4x 200ah lead acid batteries are not dead but they dont last as long as they used to. Can i simply add 4 x additional 200ah batteries onto this system (ie running 4x 5 year old batteries + 4xnew 200ah lead acids (a total of 8). OR is this not recommended and i should simply replace the current bank of batteries with 4x new Gel/lead acid 200ah.

2) Is there an option to buy 1 or 2 (5kw) lithium batteries instead of buying lead acids. I dont mind paying a bit extra as i know the lithiums will form part of my longer term goals. My worry is that my inverter/UPS will not be able to manage/communicate with the batteries correctly (and thus cause damage to them).

 

Looking forward to your responses.

Thanks 

David

 

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Hi David

I changed my 4 gel batteries with 1 x lituim battery ,

I have an old inverter but could use the manual charging parameters with lituim because the built-in BMS in the battery handles the rest

 

For me it was :

- the space saving (bulky gel batteries to wall mounted lituim),

- maintenance (I do not have battery balancers) , I annually manually balanced them

- I am hoping for an extended lifetime lituim is offering (more than ave 5 year life of gel batteries)
 

In hindsight:

I would have gotten some monitoring ability (battery shunt) first , so I could see what was happening to batteries before just changing them

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Hi. Inverter model and name please. If the batteries are shot, you can rather sell them for scrap.

Imo, go for lithium. Wish I had when I got my system.

Don't feel bad for the basic question, my first venture into going off grid was a 1.2kva mecer pc ups and 10 7ah sliding gate batteries. I knew nothing.......

 

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On 2022/05/18 at 9:26 AM, David1SA said:

1)  Can i simply add 4 x additional 200ah batteries onto this system

 

Unfortunately not. It has been proven that the new lead acids will soon deteriorate to the level of the old ones. It will be better to create two separate sets and use a changeover switch to run either one.

 

Lithium batteries on the other hand can be added as required....

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On 2022/05/20 at 12:54 PM, Dieter said:

Hi David

I changed my 4 gel batteries with 1 x lituim battery ,

I have an old inverter but could use the manual charging parameters with lituim because the built-in BMS in the battery handles the rest

I’m sorry for hijacking this post but regarding your replay, what lithium battery would you recommend to swop out 2x 100ah lead acid batteries that would give the same output. I have a 3kva pps inverter. Its a rather terrible inverter imo because there isn’t much monitoring I can do. My batteries are shortening in life span an looking to upgrade my batteries 

thanks

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On 2022/05/22 at 12:14 AM, Derek Ramos said:

 

I’m sorry for hijacking this post but regarding your replay, what lithium battery would you recommend to swop out 2x 100ah lead acid batteries that would give the same output. I have a 3kva pps inverter. Its a rather terrible inverter imo because there isn’t much monitoring I can do. My batteries are shortening in life span an looking to upgrade my batteries 

thanks

You can only use 50% from a lead acid if you want 2 years plus.  Thus a lithium of 100Ah if you use 80% of capacity will provide 60% more usable power and last perhaps 3 times longer. Just pay attention to the max current some lithiums can provide. This is one metric that lead acids are great. Some are only 0.5C.

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42 minutes ago, Scorp007 said:

You can only use 50% from a lead acid if you want 2 years plus.  Thus a lithium of 100Ah if you use 80% of capacity will provide 60% more usable power and last perhaps 3 times longer. Just pay attention to the max current some lithiums can provide. This is one metric that lead acids are great. Some are only 0.5C.

 Thank you for the information, much appreciated 

Edited by Derek Ramos
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Hi there, No such thing as a dumb question, I had to do exactly the  same 2 years ago. had 8 Narada 220AH batteries that was donated to me from another persons house they did not last 2 hours. 

I then Bought 1 x lithium battery from Lithium batteries SA, the Battery I bought was the 1st version that does not have any comms to the inverter it only has a big trip switch and a voltmeter. I cuurently get between 6-8 hours 

I  have been running it for 2 years and saved about the same price I paid for it in the 2 years, I save average R850pm 

I am planning to add another Battery and more panels this year if God supplies me with the finances for that, I already got confirmation from Lithium Batteries SA that I can add the newer battery with Comms to my system without any problems. 

 

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On 2022/05/22 at 12:14 AM, Derek Ramos said:

 

I’m sorry for hijacking this post but regarding your replay, what lithium battery would you recommend to swop out 2x 100ah lead acid batteries that would give the same output. I have a 3kva pps inverter. Its a rather terrible inverter imo because there isn’t much monitoring I can do. My batteries are shortening in life span an looking to upgrade my batteries 

thanks

Have a look at the below links, Hubble seems to be the right replacement you are looking for. 

https://powerforum-store.co.za/collections/batterys/products/hubble-lithium-s-100-12-8v-1-2kwh

https://powerforum-store.co.za/collections/batterys/products/copy-of-hubble-lithium-s-120-12-8v-1-5kwh

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3 hours ago, hoohloc said:

Definitely the S120s, but I am not sure about stock levels at the moment, best that @Derek Ramos gives Steve a call.

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  • 5 months later...
On 2022/05/18 at 9:26 AM, David1SA said:

Hi All,

 

Apologies for the basic question. I have a simple 8kw Inverter/UPS with 4x 200ah batteries at my house. This has been working well as backup power for the past 5 years.

The long term goal is to replace this system with an 8kw hybrid Sunsynk, 16 panels and 20kwh of batteries. (i have been running an efergy monitor for 2 months to see exactly what i need).

While my current system has served its purpose, the batteries are lasting now less than the 2 hours of loadshedding. I unfortunately do not have the means to outlay the 200k+ required for the sunsynk system. I am looking to get additional batteries or replace my current ones.

The questions:

1) My current 4x 200ah lead acid batteries are not dead but they dont last as long as they used to. Can i simply add 4 x additional 200ah batteries onto this system (ie running 4x 5 year old batteries + 4xnew 200ah lead acids (a total of 8). OR is this not recommended and i should simply replace the current bank of batteries with 4x new Gel/lead acid 200ah.

2) Is there an option to buy 1 or 2 (5kw) lithium batteries instead of buying lead acids. I dont mind paying a bit extra as i know the lithiums will form part of my longer term goals. My worry is that my inverter/UPS will not be able to manage/communicate with the batteries correctly (and thus cause damage to them).

 

Looking forward to your responses.

Thanks 

David

 

Hi David,

I’m hoping you can help me.

A yr ago I had an inverter  installed as we have load shedding of up to 3× a day for 2 hours at a time sometimes where I live. After one year my battery is no longer lasting more than 20mm. The guy in who installed it unfortunately has been very unprofessional about getting back to me and helping me out. This was his message to me:

“That is a 200ah 12v Gel battery.  You may use any  12v battery, but when ah (amps/ hour) is lower than 200ah it will give you less time.”

I use the inverter  for a few lights, my tv, 3 x laptops with internet connection. No heavy appliances 

Can I switch to lithium and what will give me more time over the next few years? 
 

thank you so much 

Kind regards 

Trish 

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  • 2 weeks later...

Hi @Trish,

 

I’m not David but I can answer your question.

 

It’s hard to say how long a new battery would last compared to your old one when it was new. Gel batteries are supposed to be set up to only use half of the battery to keep the battery in good health for longer. This is called using 50% “depth of discharge” (DOD). But if the battery was not set up that way, you could get slightly less capacity from a similarly-sized lithium battery (specifically lithium iron phosphate, or “LiFePO4” as they are known) because LiFePO4 batteries are ideally used from 90% to 10% (in other words, you get 80% DOD).

 

Put another way: If the gel battery was set up correctly, you would get 60% extra juice with a new 12V 200Ah lithium battery than you got from the brand new gel battery. If it was set up incorrectly, you would get 20% less juice compared to when the gel battery was brand new.

 

As long as the lithium batteries you buy are capable of “parallel” function (being connected to other batteries in a way that increases capacity but not voltage, ie opposite of “series” connection), you can add more down the road. So you could get a 200Ah now and another 200Ah later if you wanted. Or you could get 100Ah and add more later. I think you can mix sizes but for simplicity sake I would advise against it, and never mix lithium and gel.

 

My advice would be to get a 200Ah 12V LiFePO4 “drop in” battery, or 2x 100Ah ones connected in parallel. That would probably solve the problem, and get you back to around where you were when the gel batteries were new. Plus they will last at least 8 years, probably 10+. “Drop in” batteries can be used with systems that do not normally support lithium, but you still need to check which charge settings to use on your inverter (eg you may need to change from “gel” to an “SLA” setting, check the manual for the battery). And remember you will need new cables/connectors if you go from one battery to two.

Good luck!

JC

 

Edited by JankCity
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