# Which Battery too I swap out in a battery bank

Registered Users Posts: 90 ✭✭
edited October 2018 #1
12V Battery failed and was removed, three others were also removed because it is a 48V system and they are in series together making one string, there are 5 parallel strings left in the battery banks, voltage readings after overnight discharge are as follows:
String 1 = removed
String 2 = 12.51 12.52 12.52 12.51  Average = 12.515
String 3 = 12.51 12.51 12.53 1251 Average = 12.515
String 3 = 12.51 12.51 12.51 12.53 Average = 12.515
String 4 = 12.47 12.47 12.47# 12.63* Average = 12.51
String 5 = 12.47 12.41 12.60* 12.60* Average = 12.52

So the weak battery is 12.41 and is candidate to be swapped out

Now the three that were taken out were all corroded terminals, they were doing the 12.60 load lwhere the three with a star are now, that is where they were taken from and were also operating at high voltage, so the question is as follows:  given that the three corroded batteries were overloaded for 1 year or more at 12.60 what has happened to their internal plates, the external terminals were oxidised with air so one would assume the plates inside have either got thinner or have a build up.

So I will pick the least oxidised and swap it for the 12.41 battery which is obviously the weakest, that leaves 2 batteries which were running at 12.60 for a year and 4 batteries which have 12.47 (slightly low) as their voltage.  My gut feel is to put one back in in place of the one marked #
the other one is so oxidised that I can get the terminal bolt out yet so that is the most overloaded of the three.

Q) keep overloaded batteries out of bank give them a rest so to speak or replace weak battery.

So I anticipate the new voltages tomorrow to be
String 5 = 2.49 12.54 12.49 12.54 after the planned swap
String 6 = 2.50 12.52 12.52 12.52 after the planned swap

Or something similar, If I can get the bolt out of the overloaded battery without the terminal being permanently damaged, I have the option of putting it back in the following day, what are your thoughts on this.

Tagged:

• Registered Users Posts: 4,460 ✭✭✭✭✭
IMHO, corrosion on a terminal doesn't, in itself, indicate an end-of-life problem with a battery.  It's possible the higher voltage ones heated some, which could lead to accelerated corrosion.  Whether this caused an EOL condition or not isn't clear (to me).

IIRC, these are sealed battieries, so getting SGs for a more definitive indication isn't possible.  As such, I'd do some other testing on the suspect batteries, including a controlled load test, and measurment of charge current in late absorb.  Depending on the results, I'd keep reasonably good ones as spares to swap out in-service batteries as they fail.

It may be worth having a go at rejuvenating the 12.41 battery with an extended aborb.  It may have lost some capacity, but still be an acceptible spare.

My guess is in-service batteries will fail regularly, so I'd be inclined to keep spares rather than putting the suspects back in service now.
Off-grid.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
For AGM/Sealed batteries, look closely at the positive battery post(s). If it looks like the post is pushing up/out of the battery (extruding), then the positive plates are corroded and the battery is probably near/at the end of its life (Oxygen forms on the plates during charging/EQ--gassing--and cause the positive plate/grid corrosion).

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Registered Users Posts: 90 ✭✭
Estragon said:
IMHO, corrosion on a terminal doesn't, in itself, indicate an end-of-life problem with a battery.  It's possible the higher voltage ones heated some, which could lead to accelerated corrosion.  Whether this caused an EOL condition or not isn't clear (to me).

IIRC, these are sealed battieries, so getting SGs for a more definitive indication isn't possible.  As such, I'd do some other testing on the suspect batteries, including a controlled load test, and measurment of charge current in late absorb.  Depending on the results, I'd keep reasonably good ones as spares to swap out in-service batteries as they fail.

It may be worth having a go at rejuvenating the 12.41 battery with an extended aborb.  It may have lost some capacity, but still be an acceptible spare.

My guess is in-service batteries will fail regularly, so I'd be inclined to keep spares rather than putting the suspects back in service now.
Yes that is the plan, the one that caused no current to flow in the removed string, I have mentally written off for use as a camping battery
The one with the now cut off bolt will have to wait for my next visit when I have a bolt remover tool, but may be OK as well.
The 12.41 and the 12.47 was planning to do some equalisation charging on the I return with a separate battery charger.

Any ideas on which charger to get that could do 2V and 12V with variable equalisation charge or am I just dreaming that such a device exists

• Registered Users Posts: 90 ✭✭
edited October 2018 #5
BB. said:
For AGM/Sealed batteries, look closely at the positive battery post(s). If it looks like the post is pushing up/out of the battery (extruding), then the positive plates are corroded and the battery is probably near/at the end of its life (Oxygen forms on the plates during charging/EQ--gassing--and cause the positive plate/grid corrosion).

-Bill
The posts are fine, unfortunately I put a bad battery back in yesterday which has now been removed, so that leaves the three 12.47 V reading batteries still in the system waiting for an equalisation charge.  I will try and get a bolt removal bit today (last day on site) and put that bacttery back in place of a 12.47 battery in string 5

Realistically speaking equalisation is required, (never been done) so will try and equalise if I have time left today, otherwise I will leave it until I come back in a few weeks with a separate battery charger to do the job for me rather than use the generator for equalisation.

My view is that a 2nd string will have to be decommissioned sooner rather than later, perhaps in 6 months time, so we are planning for that when we get the new batteries, the old battery bank (minus 2 strings = 4 strings) will be from a 66,000 Wh design life down to a 44,000 Wh design life of which we can get 38,000 Wh - 40,000 Wh * 20% = 7,500 - 8,000 usable Watt Hours per evening or rainy day before using the generator in support of the batteries. Option exists to up the DoD from 20% to 30% going forward.

New battery bank was being sized for 48,000 Wh perhaps I will up that

Also need to select battery is finally selected
1. Tubular OpzV / OpzS Gel 1000Ah plus * 24 * 2V
2. AGM 1000aH plus *24 *2V
3. Thick plate Gel 1000Ah plus *24 *2V

No going for Lithium or other new technologies at this stage of the product lifecycle no one with any experience locally
Flooded isn't an option, no maintenance capability here in the middle of nowhere
• Registered Users Posts: 337 ✭✭✭
AGM batteries generally can not be equalized without some damage to the battery.

Conext XW6848 with PDP, SCP, 80/600 controller, 60/150 controller and Conext battery monitor

21 SW280 panels on Schletter ground mount

48v Rolls 6CS 27P

• Solar Expert Posts: 5,088 ✭✭✭✭✭
Richard,
As a business owner you really need to replace this system. You will only ruin your reputation doing all of this.

Call it years of experience but sometimes it is better to just put your foot down and risk loosing the job. As I said early on to you, someone has to be an adult here.

My prediction is you get it running and then 2 months later it is something else and they blame you!

No matter how beautiful the place is you have to run a reputable business.  Good Luck
"we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
http://members.sti.net/offgridsolar/
E-mail [email protected]

• Solar Expert Posts: 3,299 ✭✭✭✭✭
Harsh words hit home, however someone who is in the business such as Dave, would know the value of using the right equipment including the benefits of progression to newer technology, lead acid is older than the Model T Ford, so why use Model T Ford's to build your new fleet, metaphorically speaking of course. The mystery is taken care of with purpose built systems, all safeguards included, far more than a lead acid system, which has shown it's shortcomings. Naturally lightning is a wild card which must be addressed with appropriate protection in the form of appropriate SPD's, but am I blowing against the wind?
1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank
Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
• Solar Expert Posts: 5,088 ✭✭✭✭✭
I felt bad saying that even though I have not followed this thread. I could have missed alot.

I disagree with you about using the latest in a place like I imagine the op is at.

There is no reason a decent bank can't be built and new equipment to make it reliable.
I can ship most anywhere as long as someone can be there and the duty is paid. So, I know what is possible.

A shipping container full of equipment can get through customs and a truck to the site.
A helicopter if needed. I know it is not easy as all of the money has to be up front.

The people who own this place have to decide between candles and electric light.
"we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
http://members.sti.net/offgridsolar/
E-mail [email protected]

• Registered Users Posts: 4,460 ✭✭✭✭✭
Gravity is also older than a model T Ford, but I still use that tech for part of my water system.

IIRC, OP is working for newbie owners who may have little/no experience with such systems, and/or conflicting priorities for capital.  Replacing the system entirely may make sense to us, but OTOH there's something to be said for making do with what can be salvaged until the various trade-offs can be fully appreciated by the owners.
Off-grid.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
• Registered Users Posts: 90 ✭✭
edited October 2018 #11
Estragon said:
Gravity is also older than a model T Ford, but I still use that tech for part of my water system.

IIRC, OP is working for newbie owners who may have little/no experience with such systems, and/or conflicting priorities for capital.  Replacing the system entirely may make sense to us, but OTOH there's something to be said for making do with what can be salvaged until the various trade-offs can be fully appreciated by the owners.
Absolutely, the battery bank can wait a while, in the meantime we are getting the rest of the system up to scratch.

That includes the replacement of the Two lightening damaged inverters with three new VFXR3048E Inverters, the upgrade of the Hub 4 to Hub 10.3 and the replacement of the Mate with a Mate 3 so remote diagnostics is possible.

Picking them up this morning and driving through to get the central system functioning properly on Friday.

Any views on implementation of 3-phase power vs single phase for the 3 new inverters

Our proposals to the new owners include:
To replace the ageing 4kVA generator with a 2-wire system such as the PRAMAC P9000 or P12000
Battery replacement with Lead Carbon using 24 * 2V Narada REXC 1200Ah for PSOC capacitor behaviour and 7000 30% DoD lifecycle
An additional 3900 Watts of panels is proposed and the decommissioning of 6 of the old 175W panels for use elsewhere

Inverter capacity - From 6kVA single phase to 9 kVA 3-phase
Panel Capacity from 4725W to 7575W
Battery capacity stays similar at 57,600 Wh but with deeper DoD limits at 33% 1/3 instead of the previous 20% 1/5
(this equates to 19,000 Wh usable each day compared to 13,000 with the previous system)
Generator is replaced from COP 4kVA single phase to COP 9 kVA or COP 11 kVA  3 -phase with 2-wire AGS support for system

Overall a 50% improvement in system capacity plus the benefit of AGS for system support and Optics RE for monitoring
• Registered Users Posts: 90 ✭✭
edited October 2018 #12
A full electrical re-work is required on the site as well, this will include SPDs, what are the requirements for inverter protection with SPDs, here the input AC is  from the generator so class 1 is unlikely to be of much use, class 2 from generator, so do I need 2 of these ? one 3 pole+N set on generator input to inverters and one set on inverter output to LOAD DB board for remote suites with a class 3 in each guest suite db board and a class 2 in the main lodge building and laundry db boards
• Solar Expert Posts: 3,299 ✭✭✭✭✭
Regarding 3 phase, if the infrastructure is already single phase, and are the loads are single phase, there would be little to no benifit using 3 phase. A significant amount of rewiring as well as phase ballanceing would need to be performed, which is extremely time consuming and invariably inaccurate due to the changing nature of single phase loads.

The model T Ford analogy is in reference to the lack of monitoring, if the system is unattended for any length of time it would be advisable to have some sort of protection, in the case of lithium the BMS serves this function, in the case of using single cell lead acid, it would be advisable to include a neans of protection, there are such systems primarily used in telecom applications, which can be used in off grid, here is an example  https://www.alibaba.com/product-detail/PILOT-PBAT-2-Volt-Lead-Acid_60441763584.html?spm=a2700.7724857.normalList.13.2ead84963W5VDy&s=p

SPD's, Ive just completed an order with a supplier who custom makes devices according to specification, don't skimp on their use especially where long runs are concerned, voltages are critical a 1000V SPD offers little protection to a 24V system for example and the price difference between classes is negligible, consideri the value of the entire system and the aggregate cost of downtime, saving money is false economy.
1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank
Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
• Registered Users Posts: 90 ✭✭
edited October 2018 #14
mcgivor said:
Regarding 3 phase, if the infrastructure is already single phase, and are the loads are single phase, there would be little to no benifit using 3 phase. A significant amount of rewiring as well as phase ballanceing would need to be performed, which is extremely time consuming and invariably inaccurate due to the changing nature of single phase loads.

The model T Ford analogy is in reference to the lack of monitoring, if the system is unattended for any length of time it would be advisable to have some sort of protection, in the case of lithium the BMS serves this function, in the case of using single cell lead acid, it would be advisable to include a neans of protection, there are such systems primarily used in telecom applications, which can be used in off grid, here is an example  https://www.alibaba.com/product-detail/PILOT-PBAT-2-Volt-Lead-Acid_60441763584.html?spm=a2700.7724857.normalList.13.2ead84963W5VDy&s=p

SPD's, Ive just completed an order with a supplier who custom makes devices according to specification, don't skimp on their use especially where long runs are concerned, voltages are critical a 1000V SPD offers little protection to a 24V system for example and the price difference between classes is negligible, consideri the value of the entire system and the aggregate cost of downtime, saving money is false economy.
I was thinking of replacing power hungry water pump motors for the JOJO elevated water tanks with more efficient lower power 3-phase  motors, currently they operate the borehole motor for 2 hours per day as the largest power user in the resort, they are already going to replace the old 210L freezers (500W) with the same but current model product which is an A rated power version (100W)

The new big power user in the resort is going to be a laundry, previously everything was done by hand with no ironing available.
I was thinking of using the old batteries on a separate system just to power the laundry and the borehole motor in the day, but this approach would complicate things considerably.  The laundry will have two washing machines for cold wash cycle and an industrial steamer iron
The steamer iron would be the new big power user in the resort but they are fairly insistent that they must have one as they do in all their other (on grid) big 5 game lodges it will use approx 7.5kWh every day 3hrs at 2.4kW

There is no electrical protection at the moment, wires are all over the place so implementing 3-phase might be a good way to start load management, and checking of the inter-building wiring, THE POWER UTILITY DOES NOT EXIST at this location so it looks like the power distribution evolved over the last 8 years and has never been looked at properly.
For the well pump(s), look at Variable Frequency Drives (VFDs). These are basically three phase AC inverters that have a variable frequency output. They can "soft start", adjust pump RPM based on available power/pressure and volume needs/etc.

VFDs can be run off of AC voltage (single or three phase). And some now run off of DC voltage (solar electric panels, battery bank, etc.).

And there are pumping system that already have VFDs internal to the pump such as Grundfos.

https://www.grundfos.com/

The have different versions of pumps--Some pumps that will accept AC or DC input directly (the pump adjusts its operation based on the input power). Good/reliable pumps... But not cheap.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 3,299 ✭✭✭✭✭

My question about SPDs was more about the need to protect the Inverter input circuitry being fed from the Generator AS WELL as the Inverter output circuitry as a power source in its own right as follows:

Inside AC BOX of FlexWare 500 integrated system for Original Flex Power TWO
Generator Power - 3 pole switch - 3 fuses - 3 phase Class 1 SPD feeding 3 * Inverter input Hot Live
3 * Inverter Output hot live taken directly to LOAD DB BOARD with bypass switch for direct Generator connect to Load DB board

New 3 Row LOAD DB Board
DB ROW 1 = 3* Inverter Output - 3 Pole Isolator Switch - 3 fuses - 3 phase Class 1 SPD - Overall 3-phase kWh meter - 3-pole isolator switches for 3 phase buildings each with own kWh meter
DB ROW 2 Left = 3-pole isolators for each 3 phase motor with kWh meter for all motors
DB ROW 2 Right = L1 as Single Phase - 2 pole Isolator, E.L. + Distribution circuit breakers for 1-phase buildings each with own kWh Meter  + local lights and plugs in this power building
DB ROW 3 Left = L2 as Single Phase - 2 pole Isolator, E.L. + Distribution circuit breakers for 1-phase buildings each with kWh Meter
DB ROW 3 Right = L3 as Single Phase - 2 pole Isolator, E.L. + Distribution circuit breakers for 1-phase buildings each with kWh Meter

Does that sound OK or Have I too many E.L. and 2-pole isolators on separate phases
Really don't want to comment on the overall design this should really be done by an electrical engineer as part of a risk management, there is much useful information particularly if reference is through reputable global suppliers here is a good example https://blog.schneider-electric.com/power-management-metering-monitoring-power-quality/2013/03/19/how-to-choose-the-right-surge-protector/ Hope this is useful.
1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank
Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
• Registered Users Posts: 90 ✭✭
edited November 2018 #17
If I go with Single Phase design for the three new Inverters, VFXR3048E, with AGS documentation it is not clear about LOAD support function, I take it this works with the load transfer switch, I presume, that if I set 8.25kVA for AGS Load Start and 7.75kVA for AGS load End with a 9kVA Inverter bank, how much power will the inverter passthru, and draw for charging in total, it mentions on PG 28 of the Operators manual that the current is not limited other than by the transfer switch capability which is 30Amps per Leg, hence assuming it balances across the three inverters the actual limit would be 90Amps for three inverters or 20kVA, inverter damage would be prevented by the 30A circuit breakers that are specified for use on the Input and output circuits of the Inverter, so it will transfer the entire Generator capability.

If the generator is only 12kVA, then it isn't going to help much, because the inverter isn't going to combine the battery bank and the generator, so this is one reason you might think about 3-phase power, a 3-phase generator can deliver much more power than a single phase generator, but on the other hand, it is unlikely that your heavy load use is across the three phases, so either way you are going to be limited to just a bit more power than what you can get from the batteries anyway and the cost of the generator starts to become important.

• Registered Users Posts: 90 ✭✭
edited November 2018 #18
After much thought, you are correct the 3-phase doesn't make much sense when you only have 3 inverters, perhaps if you had 6 or 9 then it might make more sense, so at this stage we are going to keep it simple and implement a single phase, that still makes me question the appropriate Surge Protection design, specifically because their is no lightning rod anywhere near the installation and hence we will be dealing with class 2 protection.

Now their are two circuits to worry about, the load circuits which have cables running all over the place underground between buildings, all but one is armoured, so I think I know what caused the inverters to suffer a FET board failure. the Borehole Well Pump is fed by ordinary 6mm three core cable and it is one of the longest cable runs at around 80 metres, this needs to be replaced with armoured 3 core cable.

Will need to put a 40kA class II device in the load DB board which feeds about 11 buildings and then we have the following:

Inverter(Out) --> Load DB Board Isolator --> EL--> Isolator switches
--> SPD 40kA --> Earth

there is also the inverter input circuit which may need protection even though it is only just outside and close by

Generator(Out) --> Generator Isolator --> Inverter(In)
--> SPD 40kA --> Earth

When operating in inverter bypass mode that means 2 SPD 40k in series but that isn't the normal mode of operation.  The sub-DB Boards of the 11 buildings will only need SPD 20kA Class II 2-pole devices in their DB Boards