100 Gel Cells just fell into my lap!!

solarpowercouple · October 2017

Hi all, my name is Josh and I'm new here as of 15 minutes ago. I am a Renaissance Man and am building an off grid homestead from the ground up, shipping container house and all!

*************My first post is also lengthy, and a challenge to any who dare think outside the box**************

I need opinions on how to utilize 48 12v batteries in a bank and get even charging/discharging. I know, not ideal... by far.... but read on.....

As stated I received over 100 Alphacell gel cell 12V 86Ah batteries(FREE) from a telecommunications company. 50 of these batteries tested over 12.6 volts sitting. The rest I will be taking in for $1000 in cores, SCORE!! I understand that these are not the ideal batteries for a solar setup but I've got over $12,000 in good batteries for free so no matter the lifespan my cost per lifetime WH will actually yield a profit from the core money I'll get. I also have the possibility of getting about 100 more every year as they replace 2 years old batteries as maintenance.

About my system first,

Off-Grid system
4kw pv
2- Outback GVFX3648 Inverters
1- Outback FM80
Mate 3

Currently I only have a 48V 100Ah battery bank as this is a new system I'm putting together as extra $ comes along. Our battery bank was really the thing obviously lacking the most. We would normally lose power like 5am til dawn... Currently only running 1 inverter until my Mate 3 gets here in the next few days!

So the inevitable question, how can I utilize this gold mine I fell into?
I know that parallel strings of more than 3 is not good so that only uses 1/4 of the capacity I have available. Anyone have any fancy wiring schemes they have used with OK success? Heres my first thoughts..

* Make 3 separate banks and get 3 more FM60's for charging and program a relay to switch power between banks to the inverters....
* Make a 480V string and get a large buck converter to step down to 48v... Do they make ones big enough?.......
* Say the hell with it and wire 12 parallel runs and add bus bars like noted here and monitor individual bat voltages.. Image result for 48v battery bank wiring

Image result for 48v battery bank wiring

* Sell the batteries and use the money to offset something like a forklift battery.. or a battery pack from a Tesla Model 3 lol

An idea is that this system will be so large compared to my daily usage that I will discharge less than 10% daily. Maybe this will help with more even charging as it can be charged with less amps over more time, ie the system is almost floating most of the time. This is an almost 50kWH bank and my daily usage is only about 3-5KW

Let me know if you guys have any crazy ideas. Thanks!!

Photowhit · November 2017

I guess if they were free, I'd first get a cheap battery load tester. Batteries can have voltage but little capacity.

It's basically a heating element to put a load on the battery and tell if the voltage drops off quickly.

https://www.harborfreight.com/100-amp-612v-battery-load-tester-61747.

Then I would put together 4-5 strings of the best batteries and see how well they hold up...

You could research the battery and see if it is suitable for solar use, maximum charge and discharge rate. cycling ability...

solarpowercouple · November 2017

Yes I plan on load testing them hopefully this weekend so I really know what ive got. Gel cells are usually not great for solar as the charge/discharge rates are fairly low. These were for telecommunications so they are meant to be normally kept floating with occasional discharge. That's why I'm hoping with a large enough bank I will be hardly discharging them at all giving hope to giving them longer life. Thanks for the info!

westbranch · November 2017

To simplify things I would contemplate as you did, 48V batteries but have 2 strings not 3, to ensure better charging...know nada about Gel cells.... and this configuration will yield 168Ah/48V... and then repeat as you have money for more charge controllers and cells.

mcgivor · November 2017

solarpowercouple said:

Hi all, my name is Josh and I'm new here as of 15 minutes ago. I am a Renaissance Man and am building an off grid homestead from the ground up, shipping container house and all!

*************My first post is also lengthy, and a challenge to any who dare think outside the box**************

I need opinions on how to utilize 48 12v batteries in a bank and get even charging/discharging. I know, not ideal... by far.... but read on.....

As stated I received over 100 Alphacell gel cell 12V 86Ah batteries(FREE) from a telecommunications company. 50 of these batteries tested over 12.6 volts sitting. The rest I will be taking in for $1000 in cores, SCORE!! I understand that these are not the ideal batteries for a solar setup but I've got over $12,000 in good batteries for free so no matter the lifespan my cost per lifetime WH will actually yield a profit from the core money I'll get. I also have the possibility of getting about 100 more every year as they replace 2 years old batteries as maintenance.

About my system first,

Off-Grid system
4kw pv
2- Outback GVFX3648 Inverters
1- Outback FM80
Mate 3

Currently I only have a 48V 100Ah battery bank as this is a new system I'm putting together as extra $ comes along. Our battery bank was really the thing obviously lacking the most. We would normally lose power like 5am til dawn... Currently only running 1 inverter until my Mate 3 gets here in the next few days!

So the inevitable question, how can I utilize this gold mine I fell into?
I know that parallel strings of more than 3 is not good so that only uses 1/4 of the capacity I have available. Anyone have any fancy wiring schemes they have used with OK success? Heres my first thoughts..

* Make 3 separate banks and get 3 more FM60's for charging and program a relay to switch power between banks to the inverters....
* Make a 480V string and get a large buck converter to step down to 48v... Do they make ones big enough?.......
* Say the hell with it and wire 12 parallel runs and add bus bars like noted here and monitor individual bat voltages..
* Sell the batteries and use the money to offset something like a forklift battery.. or a battery pack from a Tesla Model 3 lol

An idea is that this system will be so large compared to my daily usage that I will discharge less than 10% daily. Maybe this will help with more even charging as it can be charged with less amps over more time, ie the system is almost floating most of the time. This is an almost 50kWH bank and my daily usage is only about 3-5KW

Let me know if you guys have any crazy ideas. Thanks!!

The diagram posted would be 96Vby the way, pity they're small capacity, multiple strings would be the only way to get capacity up to limit discharge currents, which gell cells are better suited to. The idea of multiple charge controllers charging separate banks is probably the best from a ballance perspective, then parrallel after charging with contactors in order to limit discharge currents of each bank, would be rather complicated but not impossible, the question of supporting loads during charging comes to mind,so let's think. .......pause...... You have two inverters, use one on each bank, one your current 100Ah main bank, the other on the switched parallel gell cell bank, let's call them sacrifical because there is no investment, use a voltage trigger to transfer loads to the sacrificial system when the voltage of the main bank is say ~49V thereby preserving the main banks depth-of-discharge to around 20%, for arguments sake. Switching the AC side would be easier due to lower current, but it would have to be a break before make transfer, quiet easy to accomplish with relays, when morning arrives the voltage of the main bank would rise and the trigger would transfer the load back to the main bank, the same trigger which initiates the transfer, could also be used to switch the contactors of the sacrificial banks parallel connect/ disconnect contactors. Thinking about something like this it's best to use Boolean algebra, although used primarily in computer logic, it can be applied to relays because they are binary, either 1 or 0 .
Things to consider, when using multiple controllers, each controller must have its own separate array, they cannot share a single array, latching contactors only use power when a signal is received, avoid non latching, to keep costs down, consider cheap PWM controllers, not the most efficient but they do work.

You asked for some crazy ideas, now you got one, just off the top of my head, actual design would take more thought, but I love a challenge,

solarpowercouple · November 2017

Thanks for the replies.
@mcgivor I just used the diagram as a reference(I did not create it and it is likely comprised of 6v cells for a 48v system, or 2v cells for a 12v system) to show how it recommended adding bus bars across the battery terminals for optimal charging balance through all of the batteries. Just curious if anyone has went through the trouble of doing this and saw any benefits.

On the topic of the relays, that is not a problem, I am well versed in C++ and arduinos. My panels are on 4 seperate 130v strings already so separate charge controllers would be an easy addition although the breakers, wiring and terminals would probably cost half as much as the CC's.....Probably have enough stuff laying around to make the full switching circuit. Before I had a real system, I had a walmart 12v inverter but still needed to be able to run my well pump or large loads occasionally so I made a circuit similar to the one mentioned. With the push of a button it would auto start my old onan genset, give it a warm up time, then in about 50 ms switch the power from inverter to house off, and gen power to house on. It didn't even flicker a light or shut off the tv : ) I had plans to make it look for the well pump circuit closed and to start automatically but shortly after, I purchased all of the Outback stuff.

Its been a fun, outside the box, ride but I'm excited to be playing with big boy equipment now. Mate 3 is supposed to be here tomorrow at the latest and I'm dying to get it wired up and go through the settings. I plan on adding one of the new Predator 3500w inverter geensets very soon for the long dreary days we will start having here soon in Ohio.

Photowhit · November 2017

Separate charge controllers makes no sense unless you will disconnect your battery bank from each other and inverter/system. If they are all connected to the inverter, they are all connected. Might as well use the charge controllers to capacity. The relay system would require setting a system of relays and switching and the additional charge controllers...

Might as well sell the batteries for scrap and buy a new forklift battery and know what your getting for the same cost...

BB. · November 2017

I do not like cross linking batteries in series/parallel battery banks (the "vertical" dashed connections).

If the batteries are working well, then no current flows through the cross connects. So x-links are not "useful". If a battery/cell has failed, then x-links do not "fix" the failed component... Just "hide" the failure until more things go wrong or is caught via other means (specific gravity monitoring, measuring with clamp on DC current meter, notice temperature rises/paralleled battery voltage imbalance with rest of bank, etc.)..

If one or more cells (batteries) is not working correctly, you have the open or shorted cells. Open--You still have the loss of capacity, which now have only two batteries to draw from, and the third battery is "missing in action"--But you cannot simply take a volt meter and look for bad batteries (or cells) since they are all tied together.

If you have a shorted cell/battery, then the paralleled batteries will be discharged too--And again, you will not "see" the failed cell/battery with a simple volt meter check--But shorted cell will discharge the parallel connected cells--And possibly even catch fire if conditions are right.

Cross linking series/parallel batteries is done very often with Li Ion type cells--But I have always thought that this was a cheap and dirty way to cut voltage monitoring points (three paralleled cells, one monitoring point). Li-Ion batteries can be very "unstable" if over/under charged (too high/too low of bus voltage) and need active monitoring for safety (depends on chemistry too... LiFePO4 and similar Li Ion batteries are a bit more stable if operated outside voltage range--Can still kill the cell(s), but won't catch fire/explode).

-Bill

solarpowercouple · November 2017

@Photowhit yes there would be 4 separate disconnected banks switched with relays. Simple circuit really.

@BB. Thanks, that's the kind of input I was looking for as I've never cross linked batteries before.

Thanks for the responses. Just not too sure how hard it would be to sell the good batteries on craigs and sell the rest for scrap...

BB. · November 2017

Craig's list may not allow you to sell batteries.

-Bill

bill von novak · November 2017

solarpowercouple said:

Let me know if you guys have any crazy ideas. Thanks!!

For some odd ideas:

Wire for 48V then charge per battery with isolated chargers. If the chargers are all isolated and individual they don't care what the battery arrangement is.

Do 12 strings and charge them individually with 12 chargers (have to isolate the strings while charging.)

Do 12 strings, connect them all normally, monitor current in each string and use 1 or 2 extra chargers to make sure no string gets "deprived" during charging of the entire bank.

Photowhit · November 2017

solarpowercouple said:

Just not too sure how hard it would be to sell the good batteries on craigs and sell the rest for scrap...

Where are you located, I know where to sell them in Missouri. There are people who will arrange pickup of large quantities (multiple pallets) I don't know the current quote on batteries, 3 years ago +/-they ran 30-35 cents a pound, here in Missouri.

solarpowercouple · November 2017

@BB. In Ohio I have seen nothing on craigs against selling batteries. The first bank I purchased from Craig's. Crazy to think that would even be a thing!

@Photowhit I am in Columbus oh. I do auto repair on the side and right now Advance Auto Parts is giving $20 gift cards for battery cores. I have probably $500 in stuff that needs maintenance on my vehicles so I think I'll go that route with the bad ones.

@bill von novak thanks for the ideas!

BB. · November 2017

It looks like I am wrong... I see batteries for sale. Craig's List does not specifically prohibit batteries, just "hazardous materials":

https://www.craigslist.org/about/prohibited

-Bill

Photowhit · November 2017

BB. said:

It looks like I am wrong... I see batteries for sale. Craig's List does not specifically prohibit batteries, just "hazardous materials":

They use to be on the specifically prohibited list. Perhaps they've loosened up on this...

Photowhit · November 2017

If you can use them that sounds like the best route. If they don't have a limit, it might be the best route all the way around and just sell the cards...lol.

Scrap in Dover Car batteries are bringing 36 cents a pound, For the quantity they'll likely pick up... At 65 pounds each they would bring in about $23 each. Might call and check, but usually the price would be the same. Usually there is 1 dealer who's shipping out the batteries and everyone else is selling to them.
https://iscrapapp.com/yards/us-ohio-dover-speedie-recycling/pricing/

softdown · November 2017

Alphacell gels are very high quality gels with *very low* self discharge rates. They can handle a fairly robust charge compared to many other gels. 20 or 22 amps is what they told me.

I am not afraid of deviating from some "rules". Especially at that price. I might set up three 48 volt strings to keep their discharge from falling below...say...12.2 volts for example.

It would be awesome if you could charge them all and then test voltage a couple days later. Or use a load tester like Photowit suggested.

I would try for more than scrap. Most of those batteries may still be very good.

I had seven. Would have loved to use them if I had eight. Could not find one....anywhere.

softdown · November 2017

Question for BB and others. If you can find images of the lead acid strings used on the WWII Type 21 diesel-electrics.....how did they pull off the hundreds of interconnects successfully? I don't recall how many batteries were used but it is simply unbelievable. Did find this:

Battery: three 124 cell batteries.

Images seemed like there were hundreds. Here is a picture of the control panel for the batteries (7th picture down) : http://www.ipmsstockholm.org/magazine/2003/11/detail_uboot_xxi_05.htm

westbranch · November 2017

if you meant these they sure were not small....

Image: https://us.v-cdn.net/6024911/uploads/editor/8a/bypkrbp36oe0.jpg

softdown · November 2017

westbranch said:

if you meant these they sure were not small....

The external lugs had a different configuration. Kind of like forklift batteries.....the external lugs seemed to be built into the battery. The bank allowed the large submarine to operate submersed, without diesel, for five days as I recall. Imagine the power consumed. I did find a battery control panel that I linked above your post. Here it is....7th picture down: http://www.ipmsstockholm.org/magazine/2003/11/detail_uboot_xxi_05.htm

mike95490 · November 2017

Surplus Telecom GEL batteries are generally not deep cycle rated you might get 2 or 3 dozen Cycles out of them before they die.

There being sold off because they have reached the end of their serviceable lifetime.

Hey, lets change out all these batteries just for the heck of it and instead of paying for disposal costs, we could sell them

softdown · November 2017

I've got several 8D's that are not deep cycle rated and going strong for almost three years. Others developed a bad cell while the other cells were fine.

I sold my Alphacell batteries to my neighbor, quite some time ago, who uses them for his well system. They aren't good solar batteries but I don't think they are bad either.

I would suggest keeping the voltage over 12.2 and see what happens.

solarpowercouple · November 2017

@softdown Thanks for the info. I have 3 parallel strings running now. We'll see how it goes! It's kind of a win-win either way!

@mike95490 I got them 100% free and took half of them to scrap last Monday and got a $1000 check

They are used to keep cable and internet connections up for customers if there is a local power outage. I think its more of the the thinking that if they keep them replaced every 2 years they will not have failures and a bunch of pissed off customers complaining about their internet going down during the power outage. I still agree they are not ideal batteries but at this point I made $1000 by picking them up and still have 48 good batteries. No complaints here

gmrs170a · December 2017

For all those batteries, you'll probably need a good storage cabinet. See the purpose built steel battery cabinet listed here: https://maine.craigslist.org/ele/d/off-grid-storage-battery/6381713611.html or ping me back if you (Or anyone here) is interested.

100 Gel Cells just fell into my lap!!

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