shorting solar panels for testing current

dickensian

i've got a portable solar panel setup, and want to test the panels themselves. i know i can attach a VOM to the positive and negative leads and measure voltage, and measure current. you've eliminated the controllers, extra wires, etc... however, my VOM can only read up to 10a dc current, and my panels output up to 16 amps or maybe more. my questions are a) can i cover half of the panels, and expect half the output current. in which case, i can use my 10a VOM meter wo blowing it up. b) this is the big question: can i actually just connect the leads, and put an amp clamp meter on it. my clamp meter reads up to 80a dc.... but i just don't no if this is doable. it sounds crazy, like, i expect it to blow up...   c) since b sounds crazy to me, is there a type of meter i can get that would be capable of measuring more amps than my VOM meter - that is, similar to to 80 amp maximum of my clamp meter.

and i'm assuming the above is a reliable and generally good test for a panel?

BB.

Welcome to the forum dickensian,

There are several things you can do to test your panels. Testing Voc (voltage open circuit) in almost any sunlight, and Isc (short circuit current) will find about 80% of the bad panels.

Isc is proportional to the amount of sunlight hitting the panel. You could do the measurement early in the morning/later in the afternoon (less sun, less current), or you can simply point the panel away from the sun (Cosine of 60 degrees = 0.5) at a 60 degree angle and you will get 50% of the rated Isc.

Covering 1/2 the panel could work--But it depends on the how the panel is wired and how you shade the panel (some panels are one string of cells in series, others are 2 or 3 parallel strings--All depends on the design). I would not count on shading to do this measurement (without blowing up your DMM).

If you are going to do a fair amount of DC work (cars, boats, solar), you really should look at getting an AC+DC Current Clamp DMM (digital multi-meter). They are very easy to use (just clip over a single wire) and read the current (DC current clamp meters do need to be zeroed every so often as they drift). Here are a couple links you can start with your research:

https://www.amazon.com/UNI-T-Digital-Multimeter-Current-Capacitance/dp/B078PDNS27 (prices are variable--from $50 typically to >$100 today????)
https://www.amazon.com/gp/product/B019CY4FB4 ($100 to $130 typically--Prices trending up lately)

There are AC only current clamp meters--And they are great meters, but do not do DC current measurements, so not as useful for us.

If your Clamp Meter does measure up to 80 Amps DC--Then you can use it without issue for measuring your panel current. Generally, you should not damage a DC Current Clamp meter with over current.

To measure Isc, just connect the + and - leads of the panel together (panel pointed away from sun, many solar connectors do not like to make/break connections under load). Point the sun at the panel and clip your clamp meter on the panel wire. Current Clamp meters can read around 40 or 400 amps max current--So they are great for DC power systems.

The other test is to connect the panel to battery (i.e., a "12 volt panel" to a 12 volt battery) and measure Imp (full noontime sun). This will usually find the last 20% of panel failures (past Voc and Isc, but fail Imp/Vmp test). Note that solar panels must be connected + panel to + battery and - panel to - battery... If you connect the panel backwards to a good size battery, it will typically fry the panel.

Most panel failures cannot be repaired (failed cell to cell connection, burned cell/trace, water corrosion, overheated panel, etc.).

There is one failure that sometimes can be repaired. Most panels have "by pass" diodes... And sometimes these diodes fail shorted and can be replaced. Or the junction box could have a loose or dirty connection (some panels you can open the J-Box, others are sealed).

https://www.electricaltechnology.org/2019/10/blocking-bypass-diode-solar-panel-junction-box.html

One last method to check panels... If you have two or more panels in parallel (or parallel strings of panels), you can either disconnect one string at a time while your Solar Charge controller is charging the battery bank (and/or running a heavy DC load or your AC inverter with a heavy load).... Ideally, all strings will read the same current and voltage. If you have one string that reads less current / less voltage, then you have have a bad panel or bad electrical connection in that string. Or you can simply connect your DC Current Clamp meter to the output of each parallel string and see that they are all "close" (panel string current should be within 10-25% of each other to be "good" under the "same sun").

Comparing multiple panels for Voc/Isc/Vmp/Imp at the same time (same sun, same sun angle, etc.)... Generally bad panels stand out very quickly vs good panels/strings/wiring connections when you do A/B testing in same conditions.

For arbitrary current measurements (Isc, Imp), the amount of sun is critical (haze, smoke in sky, hot vs cool day, etc.). You can look outside, and not really see the the difference between "full sun" and "50% sun"--It looks almost identical to the human eye. So just doing random noontime Isc / Imp measurements--I would expect 50% to 100% of panel rating--And still very possibly have "good" panels.

I will stop typing here--Feel free to ask more questions or for clarification.

-Bill

dickensian

thanks so much, bb for the lengthy post. that's exactly what i was looking for! so --- just to be sure, i can literally connect the negative and positive of the panels, (face them away from the sun while doing this so there's minimal current), put on my clamp meter, and get a reading? that's so counter-intuitive - to a newbie... it just seems like there would be all this current - i really don't get it. but i know you can put a VOM between the positive and negative cables, and a VOM measuring current would offer minimal resistance --- i'm speculating, since idk.... so the difference between a VOM and the wires just connected together without the VOM --------- seemed pretty similar. but i needed to be sure...

i'll give it a try ----------- that's wonderful that a clamp meter can be used, since they often measure a LOT of dc amps.............. i may have more questions later... thanks again!

BB.

You have it all correct.

There are two major classes of electrical energy sources, in engineering terms.

A voltage source. Like a battery, your ac plug in your home, etc. They try to hold 12 VDC or 120 VAC. You connect a volt meter just fine (very little current draw, of course the correct voltage range). And if you attempt to connect a current meter, which looks like a dead short, you get very high/unlimited current flow (pop a fuse or circuit breaker, or over heat a wire or device and start a fire).

A volt meter with current setting is sort of an accident waiting to happen.

There other source type is a current source. Most people do not use current sources in day to day life.

Common current sources are welding transformers, ballasts for led and florescent lamps, etc.

A current source will output a regulated about of current (say 10 amps from 0 to 120 volts).

Solar panels are current sources. Yours will output 16 amps from 0 to 30 volts DC (guess). (More or less).

Bill

littleharbor2

There are a few 20 amp digital meters out there. I own and use one for the reason you are needing one.

mike95490

Please be careful, the MC4 connectors have a very thin gold plate and will be damaged if the contacts are mated/de-mated while the panels are illuminated

dickensian

littleharbor - i went ahead and shorted the positive and negative, and used my amp clamp, which is good for --- maybe 80 amps? i keep forgetting... it seemed to work just fine --- i got up to 13.2 amps, and it was bright sun, but the panels were almost flat on the ground.  is there an advantage to having a VOM that can handle the 20amps of current?
mike - ty.... i'll be careful to work with connections on my panels when they are not exposed to sun...

BB.

In general, you need to look at the meter specifications... The number of digits, accuracy, etc. is what also is affected by the meter "range"... I.e., 40.00 amps or 400.0 amps "accuracy". Some meters have 40.0 accuracy.

Some have 00.00-19.99 volt range and a 000.0 to 199.9 volt range, etc.

For batteries, a 12 volt battery bank should be able to read ~15.00 volts... And ideally, 15.000 volts (especially for Li Ion type banks). But you are going to (probably) pay a lot more for a meter that can (accurately) display 15.000 volts...

Here is a manual for a "mid price" Klein AC+DC current clamp DMM... You can see how they rate the accuracy and significant digits (a 6,000 count display--.... 0 to 6000 is typical display capability/range).

https://images-na.ssl-images-amazon.com/images/I/A1c0ve-aSIL.pdf

For debugging, almost any meter will do as long as it can measure the voltage/current/etc. ranges needed.

-Bill

dickensian

Bill

i tested my panels today. bright sun, 1pm. it's a dokio portable setup, not used much. (i'm learning solar on the fly) it has four panels. with all four panels unfolded, and previously shorted with an amp clamp positioned, i get 12.45 amps dc up to 13.2. when i fold it so half the panels are covered, i get 6.78 and 6.23 amps... so - i assume it all looks good so far? i guess max amps in this situation would be like 16 or something... i guess i'm guessing the 4 panels are in parallel, since i can fold them and still get current?

but the final test you mentioned... that's pretty confusing. should i discharge a battery to a certain voltage to make sure the controller is in bulk mode? after i discharged one of my 12 v gel wheel chair batteries to 11.6v, it began charging at 4.9a, then 7.4, and then appeared to be in float mode, afaict, charging at 1.4, then .6, .3, .2 and on down... i took it off after a few hours. right now one of my two batteries is at 12.6 volts..........should i put a load on it, and should i stop when the battery reaches a certain voltage, and then charge it, when it should be in bulk mode? i'm really not sure how to tell when a battery is ready to be bulk charged, and how low the battery can be discharged safely... i went down to 11.6 v.......

thanks again --- hopefully this is clear.........

gregg

BB.

It does sound like your panels are in parallel (should be Vmp~17.5 volts and 100w/17.5v= 5.71 Amps Imp per 100 Watt panel in full sun).

In general, the ideal test is if the panel(s) charge your battery. That your panels have similar Isc current in full sun (and hopefully Voc--Voltage open circuit, typically around 21.0 volts for "12 volt panels") is great.

Since you have 2 (or 4?) panels, that they perform nearly the same is great. The fact that they output something like 50% to 100% of Imp/Isc in full sun--Not really a surprise. Variations in weather/smog/haze/position of sun in sky/etc. all serve to "reduce" the actual output.

Isc for a solar panel is a pretty good solar reference... More or less, Isc is 1,000 Watts per sq meter of sunlight. If you measure Isc of a panel at 50% of rated (Isc), then your probably getting 50% of 1,000 W/sqmter. Or a hazy day, possibly sun lower in horizon, etc.

Different battery chemistries have different behaviors and charging requirements. For GEL batteries (at least in the USA), they are typically charged at 14.2 volts and 5% rate or charge (i.e., 100 AH battery * 0.05 rate of charge = 5 amps). They are typically charged at "lower" voltages and longer times (high voltage/rate of charge can damage the GEL/Plate interface--basically form gas pockets).

GEL batteries are usually not an ideal solar battery type... AGM, Flooded Cell Lead Acid, etc. tend to take higher charging currents and charge faster (solar has limited "hours of sun" in a day to do a charge--A deeply discharged battery may take 2 days to recharge, especially towards the "darker" months.

Lead Acid batteries typically take "high" charging current at less than ~80% rate of charge. As the battery gets >~80% state of charge, the battery charging voltage will rise (to ~14.2 volts for GEL) and then the charge will switch from "bulk" (maximum available charging current) to Absorb charging mode (charger holds ~14.2 volts constant, battery slowly takes less current until 100% full--Can take between 2-6+ hours for a "full absorb" cycle for Lead Acid batteries). Once the battery is "full", the charger will enter "float mode" (if it has a float mode) and hold ~13.6 volts until the sun goes down, or the battery is discharged and needs recharging.

The above numbers are just "starting points". As always, check the battery manual for proper charger settings and max charging current.

All of the numbers are just guesses at this point... If you want more exact answers, having the panel(s) Vmp/Imp/Power rating, possibly the number of cells (typically 36 cells in series for a "12 volt" solar panel), type of charge controller, battery bank AH capacity, etc.

But--From what you describe--Things seem to be working OK.

In general, wiring/panes/controller fail pretty much catastrophically (either the work or don't).

Batteries, however, are a different beast. They usually slowly decay from the moment they are manufactured. Lead Acid batteries (smaller types, less expensive types) can last from 3-5 years typically (in hot climates faster failures, in colder climates longer life).

If they are not properly maintained, lead acid batteries can fail sooner. Typically a Lead Acid battery "resting voltage" is around 12.7 volts fully charged (GEL and AGM can be a bit higher).

Flooded cells should be recharged at least once per month (or float charged). AGM and GEL can go ~6 months between charging cycles and have a pretty good life.

All of this can get pretty complicated pretty quickly... I will stop here and you can ask your specific questions.

https://www.solar-electric.com/learning-center/batteries-and-charging/ (battery FAQs)
http://www.batteryfaq.org/
http://batteryuniversity.com/

Some links you fall asleep too.

-Bill

BB.

I forgot to address discharging your batteries...

More or less, a resting 12 volt Lead Acid battery is around 50% capacity at ~12.1 volts or so (resting means no loads/charging for ~3+ hours).

For longer lead acid battery life, suggest designing your system to discharge to 50% of capacity on average (you can go as low as 20% State of Charge, but you should recharge as quickly as possible to limit sulfation).

A Lead Acid battery under significant load (10% or more of battery AH capacity?) should be limited to ~11.5 volts to prevent over discharge (high surge current to start a car engine, start a well pump, etc., 10.5 volts can be seen).

And a resting battery at 10.5 volts (or less) is pretty much at 0% state of charge (and running the risk of permanent damage).

Here is a good article about Lead Acid battery vs voltage vs load vs charging cycles:

http://www.scubaengineer.com/documents/lead_acid_battery_charging_graphs.pdf

If your battery is going to 11.6 volts in minutes... Either you have very heavy loads and/or a battery that has lost capacity (sulfation--hardening of the soft fluffy lead sulfate that turns into hard black crystals--That insulate the plates and no longer are part of the load/charging chemistry--And starts in hours/day after a battery is below ~75% state of charge (no discharge/charge current).

-Bill

dickensian

thanks, bill.............. i'll take a couple days to read these............. i may have questions after, if that's all right...

dickensian

hi bill
thanks again for the info..........  if i could run a couple things by you, or anyone else, i'd appreciate it. i checked out some of the links you included in your post...

so, this is a good site, i assume, and specifically here, where it has some common sense advice about ventilation for lead acid batteries? which is that it's relatively safe to have them in living quarters, provided you pay attention to not over charging, notice off smells, etc?
https://batteryuniversity.com/learn/article/health_concerns

i am thinking of 6v agm batteries or a lithium ion, such as the battleborne 100ah 12v. lithium seems to have every advantage, although it is newish technology. i know you can't charge them when they are sub-freezing, which would ruin your expensive battery. they seem to have every advantage except initial cost... any advice on which brand of battery? i know of battleborne, and i follow this guy will prowse, who tests a variety of cheap lithium ion batteries, some of which run down to the $700 range, i think. i think he recently tested one in which the detector for a frozen battery wasn't working --- actually, i don't plan on being in frozen temps much... there's also i think a victron bms that can help monitor your battery temperature, etc...

my main problem with lead acids and agm's is the slow recharge time. i'll have a 50L fridge --- maybe 30a per day? -- and not sure what else i can run... lights, chargers, monitor... i think recharging my lead acid to full charge would take a couple to three hours at bulk, and then more than that to top it off... i don't think i want to have to worry every single day of topping off my lead acids -- and especially so if the sun is not optimal. i'd imagine that they would be always kind of under charged, and would sulfate, etc...

so the lithium would provide me up to 80ah, but an equal set of lead acids i'd need about 160 to 200ah? the lithium would charge in half the time, and wouldn't suffer from being under charged.... 

i think that's the main points. i'm wondering any advice on which lithium to get, where to get it to save a few bucks... if i should spring for the battleborne, or some other cheaper one... 

thanks again!

g

dickensian

oh, and is this article accurate in the many wonderful qualities of lithium?
https://www.solar-electric.com/learning-center/why-switch-to-lithium/

mike95490

dickensian said:

oh, and is this article accurate in the many wonderful qualities of lithium?
https://www.solar-electric.com/learning-center/why-switch-to-lithium/

I don't know, the mail-list popup is broken and won't disappear to reveal the article.    X

BB.

This was from our "Mother Ship" (Northern Arizona Wind & Sun). I did not have any issues reading the page, but I will post a copy here:

Lithium Batteries: Are They Worth the Cost?

Lithium batteries cost more up front, but in the long run they are superior to lead acid batteries for
several reasons. They are maintenance free, extremely efficient, safe, can be recharged very quickly,
and offer an expandable battery solution. Lithium batteries are cheaper long-term and are more
tolerant to infrequent full recharging and excessive discharging than their lead acid counterparts. They
make the best battery solution for high demand applications, where lead acid batteries do not and will
not survive.

Cost

On the surface, lithium batteries can appear too expensive, but we believe they are one of the best
investments one can make for their system. While the upfront costs for lithium may be higher than
other battery types, the associated benefits like longer service life, superior reliability and excellent
efficiency, will far outweigh the high initial cost. In just about all cases lithium batteries have a lower
cost per KWH per cycle. This means throughout their life cycle they will cost much less than other
batteries and thus will be the most economical solution in the long run, especially when compared to
that of high-quality lead acid batteries.

Maintenance

Many customers contemplating the switch to lithium will be replacing an existing lead acid battery bank
of some type. A flooded lead acid battery bank will require a significant amount of maintenance
throughout its life to stay healthy. Poor maintenance is a leading cause of premature failure for flooded
lead acid batteries. The electrolyte level should be checked regularly to prevent the battery from
running dry, and the battery must be filled with distilled water when electrolyte levels are low. Checking
the specific gravity from time to time is needed to guarantee the batteries are fully charging.
Additionally, the battery must be equalized when the electrolyte starts to stratify to maintain efficiency.
These common maintenance procedures can become mundane and are often forgotten, which can
cause a flooded lead acid battery to fail early. A lithium battery is completely maintenance free,
eliminating the need to add water, check specific gravity, or equalize charge.

Tolerance

Another significant contributor to premature failure of lead acid batteries is excessive discharge and
deficit cycling. Regardless of whether you have a flooded, AGM, or Gel type battery, a 50% depth of
discharge (DOD) limit should be observed in order to prolong their life cycle. Deficit cycling is also very
harsh on lead acid batteries. This happens when a battery is discharged before having the chance to fully
recharge. Plate swelling, loss of active material, and sulfation of the plates can be caused by excessive
discharge and/or lack of full recharge. To achieve the longest life possible, it’s very important not to
over discharge lead acid batteries and to make sure they get completely recharged every cycle.
Unfortunately, this can be difficult to manage, and you may find yourself constantly worrying about your
battery health. Lithium batteries are a worry-free alternative. It’s not necessary to fully recharge lithium
batteries every cycle and most have internal protections within the battery that will never allow you to
discharge down to the point of permanent damage. Generally, you can discharge most lithium batteries
to about 20% remaining capacity every day without shortening cycle life. Lithium batteries can also be
fully discharged periodically without significant adverse effects. You can use them, abuse them, and they
will suck up the energy you give them and spit it right back.

Efficiency

In several applications (especially off-grid solar), energy efficiency is of crucial importance. The typical
round-trip energy efficiency (discharge from 100% to 0%, then back to 100% charge) of a brand-new
lead acid battery is around 80%. The round-trip energy efficiency of a lithium battery is 92-98%
throughout the entire life of the battery. The charging process of lead acid batteries becomes
particularly inefficient once the absorption state of charge has been reached. This can result in
efficiencies of 50% or even less in systems with oversized battery banks or failing batteries. As a lead
acid battery ages, internal resistance builds up and the battery bank becomes even less efficient, causing
more and more energy to be converted into heat rather than stored within the battery bank. As lithium
batteries age, usable capacity is reduced but the efficiency is still maintained.

Charge Time

In most cases lithium batteries can take on more power than can be delivered to them. Charge and
discharge current limits for lithium batteries are often portrayed as capacity scalars. For example, most
lithium batteries can be discharged and recharged at a continuous rate of .5C or half the overall
capacity. Some manufacturers rate their batteries with a discharge and recharge limit of 1C. In this case,
a lithium battery can be completely charged in just one to two hours from 0%. It’s also important to
note that a lithium battery is usually between 95%-99% full charge after the completion of the bulk
charge stage. In contrast, most lead acid batteries shouldn’t be charged at a rate greater than .2C, and
the battery will achieve a maximum of only 75%-80% full charge once the bulk charge stage is finished.
After this, an additional 3-4 hours of absorption charge is necessary to fully recharge most lead acid
batteries.

Safety (BMS)

The safety and reliability of lithium batteries is a big concern, so nearly all lithium battery solutions will
use an integrated Battery Management System (BMS). The BMS is a system that monitors, evaluates,
balances, and protects cells from operating outside the "Safe Operating Area". The BMS is an essential safety component of a lithium battery system, monitoring and protecting the cells within the battery
against over current, under/over voltage, under/over temperature, and more. Another essential
responsibility of the BMS is to balance the pack during charging, guaranteeing all cells receive a full
charge without overcharging.

Expandability

One of the most significant advantages of lithium batteries over that of a lead acid alternative is that
lithium battery banks can be expanded throughout the life of the battery. This is not an acceptable
practice for lead acid batteries as the result usually ends in significant premature failure of the whole
battery bank. Being that lithium batteries don’t suffer from lack of full recharge or deficit cycling
amongst other things; the addition of new batteries simply increases the storage capacity and reduces
the load on the rest of the batteries. In most cases, this will increase the life of the battery bank. Thus,
making for a whole lot more flexibility in the design on an off-grid system and can allow one to build up a
system as needed and as a budget allows.

Others here have much more information and experience than I... I will try to give my understandings about the questions you are asking. I am not a Battery or Solar engineer.

The Battery University Site is a good site for information... However, you can have some discussions about there suggestions/conclusions... A few:

Nickel is a known toxin to humans. About 10-20% of the population will have skin rashes on direct exposure. For the average person, not a big deal. In the USA we have Nickel coins--And you would wash your hands and avoid too much exposure even to these coins:

https://globalhealing.com/natural-health/metal-toxicity-health-dangers-nickel/

Regarding ventilation of Lead Acid and similar chemistries (such as AGM, GEL, and sealed types).

When correctly charged, hydrogen (and oxygen) out-gassing is not a big issue... However there are still problems.

First is some people are very sensitive to the rotten egg (sulfur) smell from the gassing (and fine mist of electrolyte). So not a great idea to share living space with a large battery bank.

There is also the issue with the fine mist that can be caused by charging/Equalizing Charging. This can settle on nearby items and cause corrosion (shelving, books, electronics, etc.). Ventilation and/or a ventilated battery box is helpful to prevent.

Hydrogen gas does rise (from batteries) and tends to diffuse through the ceiling/roofing pretty quickly (H2 is a very small molecule). But if you have lots of hydrogen being generated, it does not take much to create an explosive atmosphere.

And this is where the rubber hits the road. Most folks should design their system to operate unattended (design and buil a reliable/safe system that only needs weekly/monthly inspection). There can be system failures (solar charge controller that fails to regulate charging voltage, needing to EQ a battery bank which generates lots of heat and hydrogen gas--Over charging of Lead Acid and AGM/GEL/Sealed batteries). And as Lead Acid batteries age, they need more charging (and AGM batteries with catalyst internal to combine H2+O2 gasses, wears out and AGM/Sealed Batteries vent).

The idea of a safely designed an operating system will help prevent accidents from happening years down the road (just like using fuses/circuit breakers, wiring designed to carry the load current, following NEC and other codes for safety, etc.).

We don't want to design a system where one failure can cause a fire/explosion.

AGM batteries are sort of the nearly perfect Lead Acid Battery (clean, tends to be more expensive and typically a shorter service life vs a similar quality Flooded Cell Battery). Lead Acid batteries these days (at least in North America) are pretty much 100% recycled so little lead/chemical pollution problem (as always, there are people that do not follow the laws/regulations).

And Li Ion can be the almost perfect battery chemistry... However, you have to understand what Li Ion chemistries are out there, and what work best for your application (and what have been Listed for use in North America by UL/NEC/etc.).

Typically, some version of LiFePO4 (lithium Iron Phosphate) tends to be the type used for Homes and RV systems. A "relatively" forgiving chemistry (for Lithium). I.e., little chance for fire if misused. Over charging and over discharging can cause other Li Ion chemistry batteries to catch fire/explode. LiFePO4 batteries are not the highest capacity, highest charge/discharge current--But for our needs (running 5-12 hours a day/night then recharging from solar), they are a very good solution (excluding price).

HOWEVER, from my limited understanding, If your Li Ion bank catches fire, besides the other issues of lithium fires (very difficult to put out)--There is the issue of one of the products that can be generated in the fire--Hydrofluoric Acid:

http://www.nano.pitt.edu/sites/default/files/MSDS/Acids/Hydroflouric%20Acid.pdf

It is unclear to me under what conditions a Lithium Battery may produce Hydrofluoric Acid--But it can be released at a battery bank fire--This is is a very big toxic mess. Fire Departments have been known to take any equipment/clothing/hoses directly to a toxic waste dump (cannot safely decontaminate any surface/room by "cleaning").

https://forum.solar-electric.com/discussion/comment/400249#Comment_400249

A house fire with a fair amount of Li Ion batteries:

https://www.kcra.com/article/15-exposed-to-toxic-fumes-after-responding-to-fairfield-house-fire/27933317

FAIRFIELD, Calif. (KCRA) —

Fifteen first responders were treated for exposure to toxic fumes after helping battle a house fire over the weekend in Fairfield, officials said Tuesday.

The Fairfield Fire Department said 11 firefighters and four officers reported feeling sick after being exposed to the fumes.

Crews responded to a fire at a home on Ash Court around 5 p.m. Saturday. There, crews found 200 pounds of lithium-ion batteries in the garage, the Fairfield Police Department said. According to officials, the batteries emitted fluoride gas after being exposed to the fire.

That's when the 15 people were exposed to the toxic fumes.

The fire department also said the incident was so toxic that crews had to throw away all the hoses and boots that were exposed while battling the blaze.

Investigators are now trying to determine what kind of business the homeowner was running.

(no further information that I have found. -Bill)

And even a small exposure (ingestion, or even just contact with skin) can cause long term health problems for humans/animals (higher concentrations cause death).

https://www.batteryspace.com/prod-specs/MSDS_LiFePO4.pdf

Specific hazards: If the electrolyte contacts with water, it may generate detrimental hydrogen fluoride. Since the leaked electrolyte is inflammable liquid, do not bring close to fire. 

Understanding on how BMS (Battery Manage Systems) are designed, installed, and used for Li battery banks is critical towards having a safe and reliable off grid power system.

My personal suggestion is to have any Li Ion battery bank in a shed separate from a cabin/home. This is not a bad recommendation for any battery bank/generator/fuel shed anyway.

I know that there are thousands (if not many more than that) of Lead Acid and even Li Ion battery systems that have been installed and used safely... I just tend to be very careful with large battery banks of any type--Safe design and operation is critical.

-Bill

BB.

If this is your first solar system... Many times you do not even really know how large a system you will need... Too small, lots of generator runtime and fuel costs. To large, wasted money and more expensive maintenance (large battery bank, large solar controllers, replacement bank years down the road, etc.).

I tend to be a bit conservative on designing a lead acid battery bank... Because of the issues you state--Designing the bank for 2 days of storage and 50% max planned discharge gives you a long life, and fairly quick recovery to 100% State of Charge with appropriately sized solar array, etc.

A lithium battery bank can charge much quicker (and more efficiently) than a Lead Acid bank... Li Ion batteries are great for hot climates (lithium batteries do not overheat when charging, Lead Acid generate more internal heat when charging).

For sub freezing applications, Li Ion need to be kept above freezing if cycling. Lead Acid can go sub zero (F) very nicely (if at reduced AH capacity)--And even have their life extended when left cold/unused during winter.

Many times, a "training battery" bank for the first (and possibly second) battery bank is nice... Get "cheap" Flooded Cell Lead Acid batteries and use them for a while. See if they meet your needs, and learn how to run your system--Many battery banks are "murdered" the first time or two by operational and/or maintenance mistakes (i.e., in-laws use the cabin for a couple of weeks, leave lights/tv on, use hair driers, etc. and kill the battery bank--Most rechargeable type batteries do not like being taken to "dead").

Not saying to never use Li Ion battery banks--Just understand your needs and the proper installation/operation of the Lithium (or any) batteries. Details matter.

-Bill

dickensian

thanks bill......and for posting the contents of the link that was problematic... yes, my first solar array..... i'm leaning to lithium,,.. the LiFePO4.... i think if i got gels, which i'm guessing are about half the cost of lithium, with flooded being the cheapest, that i'd probalby slowly or quickly ruin them... i think the charging of lead acid is going to be a daily grind... and i would guess i'd ruin them, maybe in three or so years? wasn't aware of how toxic lithium is in fires.... i'll try to start with one 100ah lithium, and if necessary, add to that. i read lithium banks can be added to fairy easily, as compared to lead acid, which can't be.

but then the other option would be as you suggest --- i guess cheap flooded lead acids... a couple hundred amp hours, for a hundred ah or electricity.... maybe four golf cart types? i prefer lighter batteries, and have heard good things about golf cart type batteries...

sorry for all the text --- not sure how people figure this stuff out, unless they are engineers............ the hard part for lithium will be pulling out the card to pay for them.

gregg

BB.

GEL batteries (at least many available in the USA) are not very good for off grid solar energy.

The "Typical" (what is typical anymore? As always, check the specifications of any battery/device before purchasing and installing) GEL battery in the USA has a C/20 or 5% maximum rate of charge.

With solar power (depending on where the system is installed, season, trees/mountains/building shade, etc.), the "hours of sun" per day is limited (something around 9am to 3pm or ~6 hours of "useful" sun per day). When you are limited to 5% rate of charge, a "6 hour day" of sun is about 30% of the battery capacity. Would take 2 or more days to fully charge a GEL battery that is less than 50% state of charge.

A 10% rate of charge (FLA/AGM batteries can take 10-13% or more rate of charge), 10% x 6 Hours a day means that a well drained FLA/AGM battery can get upwards of 60% (or more) charge on a "sunny day". Larger array, faster charging.

With GEL batteries, too fast (or too high of charging voltage) can cause Hydrogen+Oxygen gasses to form pockets between GEL and Plates--This causes a permanent reduction in battery capacity and performance.

https://www.solar-electric.com/learning-center/deep-cycle-battery-faq.html/#Gelled%20Electrolyte

Gelled Electrolyte

Gelled batteries, or "Gel Cells" contain acid that has been "gelled" by the addition of Silica Gel, turning the acid into a solid mass that looks like gooey Jell-O. The advantage of these batteries is that it is impossible to spill acid even if they are broken. However, there are several disadvantages. One is that they must be charged at a slower rate (C/20) to prevent excess gas from damaging the cells. They cannot be fast charged on a conventional automotive charger or they may be permanently damaged. This is not usually a problem with solar electric systems, but if an auxiliary generator or inverter bulk charger is used, current must be limited to the manufacturers specifications. Most better inverters commonly used in solar electric systems can be set to limit charging current to the batteries.

Some other disadvantages of gel cells is that they must be charged at a lower voltage (2/10th's less) than flooded or AGM batteries. If overcharged, voids can develop in the gel which will never heal, causing a loss in battery capacity. In hot climates, water loss can be enough over 2-4 years to cause premature battery death. It is for this and other reasons that we no longer sell any of the gelled cells except for replacement use. The newer AGM (absorbed glass mat) batteries have all the advantages (and then some) of gelled, with none of the disadvantages.

Yes, jumping into the middle of a solar power system design, it is very easy to get lost and frustrated...

My suggestion, is to follow the process (we are here to help you through the steps):

• define your loads/power needs (Watt*Hours or Amp*Hours @ XX Volts per day, peak power like starting a well pump or refrigerator, etc.). Other information (Travel trailer or Cabin, or Vacation Home, full time off grid Home, Business, etc.).
• conservation: it is almost always cheaper to conserve power than to generate it. LED Lighting, Modern energy efficient refrigerator, "solar friendly well pump", laptop computer, etc... There are lots of information and choices out there--Plus we try to walk you through the search.
• Once you have the loads documented/understood, then some simple math to a) size the battery bank, b) size the solar array based on the size of your battery bank (larger bank, more panels to charge quickly), and c) size the solar array based on location and season(s) system used (lots of sun, less solar panels needed... Far North, more panels to support fall/winter/spring loads--Possibly run a genset in dead of winter (no sun, no solar power).
• Once you have a solar system design worked out on paper... Then you can start looking at hardware that will support your needs.
• Lastly, once all the above is done, then start buying hardware.

I like to size your loads first... Otherwise, we starting talking in generalities and things get confusing fast... Sort of like looking for transpiration without knowing your requirements (bike, motorcycle, compact car, pickup, 18 wheel tracker/trailer).

Once you have the rough system specifications, then we only need to discuss the "reasonable" solutions that support your needs. Golf Cart Batteries are a great starter bank for smaller to mid-size systems--But not for larger systems, and possibly too heavy/too large for some RV applications (for example).

It all makes more sense as you build on your knowledge... And even if you decide to hire somebody to design and install your system--It is still good for you to know/understand the basics and what your installer is doing. Also makes it easier for you to do some of your own inspections and maintenance down the road.

-Bill

Photowhit

Something I wrote a couple years back, Lithium prices have come down a bit, but I don't consider them a value for off grid home use yet.

Lithium vs Lead Acid

While LiFePo4 can be discharged 80-90% and they last a long time, they are still more expensive than lead acid for off grid use. In off grid use we need to have a reserve capacity, usually 4-5X our daily use for cloudy days.

We try to stay in the upper 20-25% in daily cycling. But use the extra capacity when needed. Lead acid forklift batteries are often discharged below 50% daily for years. Golf cart and any 'true' deep cycle can be discharged 80%, but your number of discharges to this state are limited.

This is roughly how I works. 

Lithium may get 3x the amount of cycles if compared. Some are claiming they will last 10,000 cycles, which may be true, but cost as much as 10X. Lithium will basically tell you they are not, yet, cost effective for off grid solar use.

Here are 2 statements cut and pasted from the linked site;

"Let’s compare a classic in the off-grid solar world, the Trojan T-105 flooded lead acid battery. It’s 6V, 225Ah (amp hour) for a total of 1350Wh (watt hour). It costs about $160. We’ll compare that with the SimpliPhi 1310Wh 12V, 102.4Ah, that costs about $1750. I know, that’s 10x more for almost the same capacity battery,...."

"That means, you will have to replace the lead acid batteries more than 3 times to get the same life cycle of the SimpliPhi batteries"

They make it LOOK like lithium are a better value, because they say you don't need as large a battery. But if you don't have the reserve capacity, you will need to run a generator or other supplemental charging sources. Requiring a generator and gas to supply expensive energy and that savings on maintenance will go into servicing the required generator.

Lithium is likely the future of batteries, but it will have to be much less expensive, to be cost effective for off grid use.

https://www.altestore.com/blog/2017/02/simpliphi-lithium-batteries/#.XNlXyPZFzIU                                     

I'll add that a couple winters ago, I left for a 7-10 days in Florida. I have PEX plumbing and heat with wood. My lead acid battery lives outside, but I would HAVE to have a lithium battery in heated space. Turns out I helped my mom with a cracked vertebra and didn't return until about 10-12 weeks later. When I got home, I opened the freezer and tossed a couple Hotpockets into the microwave. If I use a lithium battery bank, it would have to be inside or heated in a different space, or I would have had to shut down my entire solar electric system. 

I'm always puzzled by the people who think it's a huge chore to maintain flooded lead acid batteries. I replace lost water about once a month in the winter, even with my 9 year old battery running hard in the summer it's no more than once a week and likely if I kept it 1/4" under the top I could go 2 weeks. When the system is minimally used it requires less attention. I think I had to add add distilled water to 2 or 3 cells after I returned.

Consider also that current pricing for lithium is a bit under $1000 for  1 kWh of storage, my 16 kWh battery cost $2525 delivered. A comparable lithium battery with around 12 kWhs would run $10,000...

Lithium is very likely to be cost effective soon, but IMO isn't there yet. I'm looking forward to solid-state lithium batteries. Pray they are 'Goodenough'! (John B. Goodenough is a one of the people who helped design lithium batteries and at 98 yrs old is still in the forefront of designing the solid state version.)

dickensian

sorry, this thread has morphed a bit, and it's my first post... maybe it should've been in something like vans/rv's, as i will be in a cargo van. but my initial question was general --- how to test my new portable dokio 300w panels..... my first panels....

i'm definitely not getting gel... if i go lead acid (a moderately big if, at this point) it'd be the cheapest option (flooded lead acid) or agm (more expensive, but seems superior). i sort of guessed that FLA on homes would make sense, or on other big vehicles that need big battery banks... my god, the cost for lithium.......omg.... for a big bank seems crazy. 

so i'll be living in the same space as my battery or batteries --- hence my interest in health concerns of charging lead acids. i'm still unsure about that, but the post from battery university seemed to clearly say that lead acids in a living space were possible and that hazards can be watched and smelled for.... but since i'm in a van, and the exigencies of travelling and everything are very flexible, it tilted everything against lead acids (because of the necessity to keep them fully charged) and to lithiums... which have a lot of advantages, except initial cost.  i could definitely see, i think, flooded lead acid in a house. it's all stationary!  for a van though, with less of a need for power consumption, the initial outlay for lithiums isn't ...well, completely off the chart..

but, yeah, this is pretty difficult and kind of frustrating. i'll take your advice, bill, and try to calculate my loads. i have my 50L fridge, a kill a watt meter... and i looked up conversions from ac to dc power... so, i'll start there, as that will be my major load. i've already bought some equipment, though --- it's just too hard to do this all in my head without some actual stuff to experiment with. so i have a 40a charge controller, epever, the 300w portable panels, a couple used wheel chair batteries... and am watching a ton of videos and reading articles on solar, batteries, wiring, fusing, etc...... a lot of stuff flying at me!  i'm definitely trying to keep my power consumption low, but will have the various electronics we all seem to need nowadays.... hope to use a raspberry pi computer, which uses very little power.

i definitely appreciate the support i've gotten here......thanks so much, particularly bill....