Which_battery

Lithium-ion vs AGM Battery has been a very popular topic in independent power circles in recent times In light of my last post concerning the use of the DC or Hybrid concept for electrical power, it occurred to me that the system could also have used monobloc AGM/Gel batteries or indeed a bank of long life 2 volt gel cells. In that case why was Lithium chosen? Hopefully this post may go some way to highlighting that decision process.

Across all markets over recent years Lithium-ion batteries have been gaining in traction . To the uninitiated it is easy to dismiss Lithium-ion as an expensive alternative to VRLA (valve regulated lead acid) technologies such as AGM (absorbed glass mat), if simply looking at the amp-hour (Ah) rating. This was the initial mistake I made a few years back. Digging deeper it became clear to me that there is a lot more than Ah ratings to consider, when choosing the best batteries for your application.Lithium-ion vs AGM Battery

In the marine world (which is where I have the most experience) the choice these days and especially with higher loads – often simply comes down to Lithium-ion vs AGM Battery. In the comparisons below whilst Gel batteries are shown, they do have a lower effective capacity at high discharge currents.  They cost about the same as AGMs, assuming both types are monoblocs, as opposed to 2 V long life gel cells. Wet cell or flooded lead acid (FLA) batteries whilst referred to are not considered for the crux of this particular comparison, primarily due to maintenance and safety considerations in the marine environment. This of course may not apply to other markets.Lithium-ion vs AGM Battery

Useable energy and cost

It is generally accepted that the most economic and practical depth of discharge (DOD) for an AGM battery is 50%. For Lithium-iron-phosphate (LiFePO4 or LFP) which is the safest of the mainstream Li-ion battery types, 80% DOD is used.

How does this work out in the real world? Let’s take two Victron 24V battery examples and compare useable energy for a small yacht:

  • 1 x Victron Lithium-ion 24 V 180 Ah

The nominal voltage of the LFP cell is 3.3 V. This 26.4 V LFP battery consists of 8 cells connected in series with a 180 Ah rating. The available energy is 26.4 x 180 = 4. 75 kWh. Useable energy is 26.4 x 180 x 0.80 = 3.8 kWh.

  • 2 x Victron AGM 12 V 220 Ah

The nominal voltage of the lead-acid cell is 2.0 V/cell. Each 12 V monobloc battery consists of 6 cells connected in series with a 220 Ah rating. Connecting 2 x 12 V 220 Ah batteries in series to give 24V and 220 Ah, the available energy is 24.0 x 220 = 5.28 kWh. Useable energy is 24 x 220 x 0.50 = 2.64 kWh.

This begs the question, what Ah rating of AGM batteries would be the equivalent of the 3.8 kWh useable energy of the Lithium-ion battery? To get 3.8 kWh of useable energy from an AGM battery it would need to be twice that size to start with due to the 50% DOD economy rule i.e. 3.8 x 2 = 7.6 kWh. At 24V that would mean 7,600/24 which gives us a battery rating of 316.66 Ah, which is moving closer to twice the rated capacity of the Lithium-ion 24 V 180 Ah. Note this does not take into account, the ageing of the batteries, temperature derating or the effect of higher loads. For AGM batteries, higher loads have a greater effect than on Lithium. See the section – Useable energy: effect on discharge capacity and voltage with differing loads, below. Based on all this it is reasonable to say that an AGM battery will need to be twice the Ah rating of a Lithium one.

What about price? Using the Victron price list we see that a 12V 220 Ah AGM is € 470 ex VAT or 2.136 €/ Ah. For 316.66 Ah that is the equivalent of € 676.50 at 12V or € 1,353 at 24 V. The 24V 180 Ah Lithium is € 4,704 for the same amount of useable energy and is therefore 4,704/1,353  = 3.48 times more expensive (or less if we consider the factor of 2 referred to above) when comparing Ah ratings.

Based on this you might immediately conclude that Lithium is not cost effective, however useable energy compared to price is only part of the story.Lithium-ion vs AGM Battery

Usable energy

 

Weight

Most Ah ratings of batteries regardless of type are specified at the 20 hour rate. This was fine in the days of light loads, but as the number of loads and the size of loads has increased over time, we also need to look at high short term loads, medium and longer term ones for differing types of equipment. This can mean a large battery pack. At the extremes we might have air conditioning running for 10 hours using 10 kW, compared to an LED light using 100 Watts in that time. Balancing these differing requirements and all the loads inbetween becomes key. With a large pack as shown below to achieve this, it becomes clear just how heavy Lead Acid can be compared to Lithium. 1360/336 = 4 times heavier.

Weight

 

Useable energy: effect on discharge capacity and voltage with differing loads

As stated earlier most batteries Ah rating are quoted at the 20 hr rate. In the image below for the lead acid battery, if that were a 100 Ah battery at the 20 hr rate, you can see that 0.05C means 100 x 0.05 = 5 Amps for 20 hours = 100 Ah available until the battery is totally flat. As we use only 50% of the battery we can see that the voltage will still be 24 V at 50% DOD for a 5 Amp load over 10 hours, and therefore we would have consumed 50 Ah.

Increasing the current draw (as the graphs below show) can affect the useable energy available and battery voltage. This effective shrinkage in the rating is known as Peukert’s effect. With lead acid the higher the load, the more you need to increase the Ah capacity of your battery to help alleviate this. With Lithium however a load  of even 10 times greater at 0.5C can still have a terminal voltage of 24V at 80% DOD/20% SOC, without going up on the Ah rating of the battery. This is what makes Lithium particularly suitable for high loads.

Note: In the graphs below Discharge Capacity vs Terminal Voltage is shown. Usually you will see AGM graphs as Discharge Time vs Terminal Voltage. The reason we plot Discharge Capacity (instead of Discharge Time) is that Lithium has a higher and more stable terminal voltage than AGM, so plotting the curves with Discharge Capacity in mind gives a more accurate comparison of the chemistries, showing that Lithium increases useable energy at higher loads due to higher and more stable terminal voltages. Whilst you may consider this a grey area (in part too due to the varying internal resistance of batteries also) it is probably the only true way to compare the technologies. This is further demonstrated in the images below the graphs.

Lithium – Discharge Capacity vs Terminal Voltage

LithiumLead Acid – Discharge Capacity vs Terminal Voltage

Lead_AcidUseable Energy (Lead Acid)

Useable_Energy_Lead_Acid

Useable Energy (Lithium)

Useable_Energy_Lithium

 Charge Efficiency

Much that we have seen in the discharge process is also true in the converse process of charging. Don’t be put off by the large generator sizes shown below, as this blog merely shows a range of scenarios. Solutions are scalable in principal. First let’s compare charge efficiency of Lead Acid on the left to Lithium on the right, during the complete charge cycle. Charging the last 20% of a lead acid technology battery is always slow and inefficient when compared to Lithium. This is borne out in the fuel costs (or whatever charging source you use) in the images further down. Note the difference in charge times too.

Note: Charge rates

The recommended charge rate for large size AGM batteries is 0.2C  i.e. 120A for a 600A battery consisting of paralleled 200Ah blocks.

Higher charge rates will heat up the battery (temperature compensation, voltage sensing and good ventilation are absolutely needed in such a case to prevent thermal runaway), and due to internal resistance the absorption voltage will be reached when the battery is charged at only 60% or less, resulting in a longer absorption time needed to fully charge the battery.

High rate charging will therefore not substantially reduce the charging time of a lead-acid technology battery.

By comparison a 200Ah Lithium battery can be charged with up to 500A, however the recommended charge rate for maximum cycle life is 100A (0.5C) or less. Again this shows that in both discharge and charge that Lithium is superior.

Charge_Efficiency


Charge_Efficiency2


 

Charge_Efficiency3

Battery choices, markets and cycle life

Depending how you treat a battery you can reasonably expect the range of cycles below, subject to the DOD and the battery banks being properly sized for the loads. Operating temperature also comes into play. The hotter the battery the less time it will last. Battery capacity also reduces with ambient temperature. The baseline for variations due to temperature is 25 degrees Centigrade.

Battery_Cycle_Life


Battery_Cycle_Life2


Battery_Cycle_Life3

Conclusions

Clearly AGM batteries will need to be replaced more often than Lithium. It is worth bearing this in mind as this entails time, installation and transportation costs, which further negates the higher initial capital cost of Lithium as does the lower cost of recharging Lithium.

No matter what battery choice you make there is also both a capital cost and technological risk at the outset. If you are in a position of having the capital for the higher upfront costs of Lithium, you might find that life is easier and that choice is a cost effective one over time. Much of this depends on the knowledge of the operator and how they treat a battery system. There is an old saying that batteries don’t die, they are killed. Good management practices are your insurance against early failure, regardless of the technology used.

Lithium-ion vs AGM Battery? The choice is yours. Personally I think the time is right to consider Lithium in the marine industry as a cost effective, reliable, high performance solution. Last week (it was only out of curiosity you understand) I went for a test drive in a Lithium-ion powered Tesla Model S – and as we know, no self-respecting electric vehicle manufacturer would still use lead acid based battery technologies today. Time for the marine industry to catch up with the Lithium-ion vs AGM Battery debate?

John Rushworth

Credits

Thanks to Reinout Vader and Johannes Boonstra for the images and technical advice in writing this blog.

Further reading

Whitepapers, inc Energy Unlimited by Reinout Vader:  https://www.victronenergy.com/support-and-downloads/whitepapers

Battery choices: https://www.victronenergy.com/batteries

 

 

 

 


Lead acid battery charging in cold weather

This blog covers lead acid battery charging at low temperatures. A later blog will deal with lithium batteries.

Charging lead acid batteries in cold (and indeed hot) weather needs special consideration, primarily due to the fact a higher charge voltage is required at low temperatures and a lower voltage at high temperatures.

Charging therefore needs to be ‘temperature compensated’ to improve battery care and this is required when the temperature of the battery is expected to be less than 10°C / 50°F or more than 30°C / 85°F. The centre point for temperature compensation is 25°C / 77°F.

Cold weather also reduces a battery’s capacity. This is another factor that needs to be taken into consideration, along with the load and charge rate compared to the battery capacity (Ah). Both of these factors affect the correct and consequent sizing of a battery for your particular application.

Battery capacity in Ah is usually quoted as a 20 hour capacity rating at 25°C. The discharge rate or load can be written as 0.05C where for example C is the load factor of the 20 hour rated battery capacity at 25°C.

Worked examples: If a 100Ah 20hr rated battery then a 0.05 load would be 100 x 0.05 = 5 Amps or 100/20 which is also a 5 Amp discharge rate over that 20 hour period. A 10A load on a 100Ah 20 hour rated battery would therefore be a 0.1C discharge rate, a 0.2C discharge rate on a 200Ah would be 40A and so on. C ratings also relate to charge rates as well as discharge rates.

When buying a battery you may see its Ah quoted at 20 (the standard rate), 10 and 5 hour rates so you can see how load ‘shrinks’ the Ah. Some even quote at 25 hour rates, which often fools people into thinking they are getting a bigger battery than standard.

To recap – capacity reduces at low temperatures, as it does for higher discharge C rates above the 0.05C 20 hour rate. This reduction in capacity due to higher discharge rates is due to Peukert’s Law.

Graph showing the effect on battery capacity due to temperature and load:

Lead acid battery differences

Lead acid batteries come in a variety of types:
  • Wet lead with the ability to top up each of the six cells with de-mineralised water.
  • The so called ‘sealed’ wet lead leisure or rather maintenance free battery. These cannot be topped up and often have a green go or red no go cell inspection indicator.
  • AGM (Absorbent Glass Mat) valve-regulated lead-acid (VRLA), where the electrolyte is absorbed in a glass mat.
  • Similar to the AGM, but the electrolyte is held in a Gel.

All of the above are however lead based (as opposed to lithium) technology. Besides lithium batteries Victron Energy sell VRLA AGM and Gel monoblocs (6 x 2V cells in series) due to their superiority over wet lead monobloc types. Victron’s range consists of:

  • Gel (Better cycle life than AGM).
  • AGM (Better than Gel for higher loads and well suited for use with inverters).
  • AGM Telecom. Designed primarily for Telecom applications, but also excellent ‘footprint space savers’ for marine and vehicle applications.
  • AGM Super Cycle (Best if frequent discharge to 60-80% DOD is expected).
  • Lead Carbon Battery (Improved partial state-of-charge performance, more cycles, and higher efficiency).

Additionally Victron also sell specialist lead acid type batteries.

  • OPzV 2V individual battery cells. Long life, high capacity gel.
  • OPzS 2V individual battery cells. Long life high capacity flooded tubular plate batteries for specialist solar applications.

Temperature compensation and charging

Now we know about the kind of batteries, capacities and loads we are dealing with, we need to put some numbers together for temperature compensation and charging.

The recommended temperature compensation for Victron VRLA batteries is – 4 mV / Cell (-24 mV /°C for a 12V battery).

Besides accounting for cold weather charging the charge current should preferably not exceed 0.2C (20A for a 100Ah battery) as the temperature of the battery would tend to increase by more than 10°C if the charge current exceeded 0.2C. Therefore temperature compensation is also required if the charge current exceeds 0.2C.

How to achieve temperature and voltage compensated charging

There are a range of Victron products to achieve this.

With our range of inverter/chargers and since VE.Bus firmware version 415 was released some time back this has ensured that:

– Temp compensation continues down to -20C

– This is for all voltage set-points, except for float, storage and the start of bulk charging

– As soon as the temperature goes below -30C, the compensation mechanism is disabled (normal charge voltages are applied) and a warning is shown.

For systems that don’t use an inverter/charger – we can use Smart Battery Sense to ensure that charging sources provide optimal voltage and temperature compensated charging to your batteries, by wirelessly transmitting accurate battery voltage and temperature values to your Solar Charge Controller or Smart battery charger.

This information is then used to set the ideal charging parameters, resulting in more complete, faster charging – improving battery health and therefore extending battery life.

The Victron Toolkit app allows you to calculate cable sizes and voltage drop. Here’s an example where cable length is the round trip of the positive and negative battery charging cables. This is so you get an idea of what Smart Battery Sense automatically takes into account to ensure the correct charge voltage goes into the battery, by ensuring the charge voltage is compensated for and corrected due to any cable losses.

Victron’s range of SmartSolar MPPT Charge Controllers all work with the Smart Battery Sense. In fact I’ve just fitted one to my motorhome, along with the required Smart Battery Sense, due to the fact the leisure battery temperature location when compared to the location of the controller can have a difference of up to ten degrees. Definitely a case for ensuring accurate temperature compensation.

Other products can be connected too by using what we call ‘VE.Smart Networking support’. See the VE.Smart Networking page.

Conclusion

With the above solutions I know I’ll be happier now that my batteries are getting exactly the right charge due to optimal temperature and voltage compensation.

Why not make sure you are doing the same…

John Rushworth


Why do solar street lights fail in Ghana ?Why are our streets so dark? Why are we not seeing working solar street lights in our streets today?

The answer is simple: some stand-alone solar street lights cause more problems than they solve. In some cases they don’t solve any problems at all.In Ghana a lot of streetlights are installed during  the election year ,streets are kept lit constantly and then all of a sudden the lights go out and never come on again.In recent times regular streetlights have been replaced with stand alone solar streetlights and some of them are quite fancy.

Smart Solar Street Light installation in Antigua and Barbuda

The real question is still whether this technology is economically feasible right now or whether we should wait for technology to evolve further before we take the inevitable plunge.The question of feasibility has reared its head due to bad decisions on the implementation of inadequate solar
components combined with “quick fix” solutions versus sustainable, long-term solutions.
The solar street light is a prime example of this. How many solar street lights have you seen that are not in working order? If you haven’t seen any solar street lights at all, it may be that the local municipality has not been convinced of the feasibility of these systems because so many systems have failed to date.
The solar street light is mostly sold as an LED street light with a battery box and a solar panel mounted on top of a 6 – 9 m pole. This is known as a “stand-alone” solar street light. The theory is that the solar panel will charge the battery during the day and, at night, the light will use the power stored in the battery to provide light.This idea should be considered a match made in heaven and a solution to many problems: streets lights use a lot of electricity and eliminating even only half of this consumption would lighten the strain burden on the grid. LED has a much longer life expectancy, so maintenance costs on the lights should
be minimal. So why do we not see this exciting development in our streets today? The answer lies with a combination of quality and longevity and with an understanding of the products.

Victron Energy’s highly efficient, ultra fast MPPT Solar Charge Controllers provide more efficiency in solar street lighting

The lighting units use quality components. The solar panels are 24% efficient (about as good as you can get commercially) and the LED lights are among the best at 160 lumens per watt (lm/W). The more lm/W a lamp produces the more efficient it is.A traditional incandescent light is around 15 lm/W, an energy-saving fluorescent bulb is around 60 lm/W. Easy then to see the attraction of solar power for free and lamps that are over 10 times as efficient as old fashioned bulbs – all which nicely meets companies requirements for improvements in sustainability and efficiency.

EnGoPlanet Inc ,a New York based company chose to use Victron Energy’s highly efficient, ultra fast MPPT Solar Charge Controllers, plus Victron batteries together with lighting options such as:

  • Wireless internet connection for remote control and management.
  • Smart Cameras.
  • Sensors for collecting various environmental data.
  • Mobile phone charging stations.

Their Smart Solar Street Lights are used in the Kuwait project, where 140 units have been installed. Petar Mirovic, CEO of EnGoPlanet tells me that the success of the project has interested other oil companies too, such as Saudi Aramco who are considering an installation of over 1,000 units in the coming months.

Well – that all sounds to me like a recipe for success!


Apparently the economics for backup power alone just aren’t that attractive.

Tesla has quietly removed all references to its 10-kilowatt-hour residential battery from the Powerwall website, as well as the company’s press kit. The company’s smaller battery designed for daily cycling is all that remains.

The change was initially made without explanation, which prompted industry insiders to speculate. Today, a Tesla representative confirmed the 10-kilowatt-hour option has been discontinued.

“We have seen enormous interest in the Daily Powerwall worldwide,” according to an emailed statement to GTM. “The Daily Powerwall supports daily use applications like solar self-consumption plus backup power applications, and can offer backup simply by modifying the way it is installed in a home. Due to the interest, we have decided to focus entirely on building and deploying the 7-kilowatt-hour Daily Powerwall at this time.”

The 10-kilowatt-hour option was marketed as a backup power supply capable of 500 cycles, at a price to installers of $3,500. Tesla was angling to sell the battery to consumers that want peace of mind in the event the grid goes down, like during another Superstorm Sandy. The problem is that the economics for a lithium-ion backup battery just aren’t that attractive.

Even at Tesla’s low wholesale price, a 500-cycle battery just doesn’t pencil out against the alternatives, especially once the inverter and other system costs are included. State-of-the-art backup generators from companies like Generac and Cummins sell for $5,000 or less. These companies also offer financing, which removes any advantage Tesla might claim with that tactic, as GTM’s Jeff St. John pointed out last spring.

“Even some of the deep cycling lead acid batteries offer 1,000 cycles and cost less than half of the $3,500 price tag for Tesla Powerwall,” said Ravi Manghani, senior energy storage analyst at GTM Research. “For pure backup applications only providing 500 cycles, lead acid batteries or gensets are way more economical.”In Ghana  good  quality lead acid batteries such as the AGM telecom batteries retail at $219/Kw/hr and can be purchased at nocheski Solar (Victron Energy partner ) in the port city of  Tema. These AGM batteries have 1800 cycles at a D.O.D of 30% or 750 cycles at a D.O.D of 50%

 AGM telecom battery by victron energy

AGM telecom battery by victron energy

In California, batteries can benefit from the state’s Self-Generation Incentive Program (SGIP). But California regulators have indicated that battery systems need to be able to cycle five times a week in order to be eligible, which would exclude Tesla’s bigger battery.

“In current discussions on SGIP program overhaul, it is very likely that stronger performance requirements may get added, which will make a 10-kilowatt-hour/500 cycles product outright ineligible (if cycled only once a week), or last only 2 years (if cycled every weekday for about 500 cycles over 2 years),” said Manghani. “In short, the market’s expectation is that for a $3,500 price tag, the product needs to have more than just 500 cycles (i.e., only backup capabilities).”

Backup power alone simply doesn’t have as strong a case as using a battery for self-consumption. That said, the opportunities for self-consumption are still few and far between.

A GTM Research analysis for residential storage, purely for time-of-use shifting or self-consumption. found that the economics only pan out in certain conditions. In Hawaii, for instance, the economics of solar-plus-storage under the state’s new self supply tariff looks only slightly more attractive than solar alone under the grid supply option.

“So it comes down to the question of customer adoption of a relatively new technology for only slightly improved economics,” said Manghani. “This doesn’t mean residential customers are not deploying energy storage,” but he noted that these were the early adopters.

Tesla appears to be focusing its efforts on first movers and the markets where storage for energy arbitrage and self-consumption makes economic sense.

While the 10-kilowatt-hour option has been removed, the Powerwall website continues to offer specifications for Tesla’s 6.4-kilowatt-hour battery designed for daily cycling applications, such as load shifting. The battery is warrantied for 10 years, or roughly 5,000 cycles, with a 100 percent depth of discharge. The wholesale price to installers is $3,000.

The smaller battery is often marketed as 7 kilowatt-hours, which would appear to have a price of $429 per kilowatt-hour. In realty, it’s a 6.4 kilowatt-hour battery at a price of $469 per kilowatt-hour.

A bigger, cheaper or more integrated battery product could soon be added to Tesla’s lineup. In January, CEO Elon Musk announced a new Powerwall option will be released this summer.

“We’ve got the Tesla Powerwall and Powerpack, which we have a lot of trials underway right now around the world. We’ve seen very good results,” said Musk during a talk to Tesla car owners in Paris, The Verge reports. “We’ll be coming out with version two of the Powerwall probably around July, August this year, which will see [a] further step-change in capabilities.”

At this point, it’s unclear what the “step-change” will be.

 

 


Why your Lead Acid Battery is all Swollen Up

Working in the solar Energy industry in Ghana, I often come across several batteries that are swollen up .These mostly lead acid batteries have often than not, been purchased at very high prices not too long ago. On this particular occasion our team was conducting a survey at a prospects home in Tema when I noticed that all of her eight 100Ah batteries were swollen.

Typically a 100Ah battery will cost between $200-$300 depending on quality .In addition to this, most suppliers in Ghana give little or no warranty even though some global brands like Victron Energy give up to two year warranty on their batteries .This article aims to reveal to the public why lead acid batteries swell-up and how to avoid the problem.

Sealed lead acid batteries – both AGM and gelled electrolyte can swell up and expand sometimes. This happens due to the construction of lead acid batteries which is referred to as “recombinant”. They are constructed in such a way to allow absorption of gasses released during the chemical process inside the battery.

The positive and negative plates are placed very close together with only the thickness of the divider separating them. They are tightly secured in the cell cavity resulting in very little extra space inside the battery. When the cell plates expand, it exerts pressure on the inside walls of the battery. This situation can cause the battery case to swell resulting in possible splits and cracks at various points of the battery.

Why Do Battery Cell Plates Expand?

The cell plates most often expand due to overcharging of the battery. The battery may also expand due to shorting of the terminals of the battery. Both these situations results in heating up of the cell plates inside the battery. The lead of the cell plates has a high expansion rate when heated.

The outcome is that the battery experiences extreme pressure inside that swells up and deforms it. The swelling-up of the battery may also cause great damage to the internal components and parts.

Why your Lead Acid Battery is all Swollen Up ,How to Avoid Swelling Up of the Battery?

Overcharging or short-circuiting of the battery is the only reason for swelling up of the lead acid battery. The problem is not inherent in the battery itself. In order to avoid swelling up of the battery you need to tackle the underlying cause of the problem.

You need to follow proper instructions in charging the battery. The culprit may be that you are using a wrong charger when charging the battery. If the charger is providing too much current, this may be the cause for battery swelling up. For instance, if you used 24V charger to charge a 12V battery it will most probably result in overcharging of the battery.

Whatever the reason for overcharging of the device, the end result is the swelling up of the battery. To avoid the prospect of overcharging or short-circuiting of the battery, you need to take the following precautions:

  • Use the right type of charger that is fully compatible with the battery.
  • Ensure proper polarity when connecting the charger to the battery
  • Shield the battery terminals to avoid short-circuiting of the battery
  • Use a charger whose maximum charging capacity is lower than the battery
  • Using a good quality charger
Victron Energy Blue smart charger is a good choice for small battery banks in Ghana

Victron Energy Blue smart charger is a good choice for small battery banks in Ghana

 Battery charging tip: increase battery life with Victron 4-step adaptive charging

Victron developed the adaptive charge curve. The 4-step adaptive charge curve is the result of years of research and testing.

The Victron four-step adaptive charge curve solves the 3 main problems of the 3 step curve:

  • Battery Safe mode

In order to prevent excessive gassing, Victron has invented the ‘Battery Safe Mode’. The battery Safe Mode will limit the rate of voltage increase once the gassing voltage has been reached. Research has shown that this will reduce internal gassing to a safe level.

  • Variable absorption time

Based on the duration of the bulk stage, the charger calculates how long the absorption time should be in order to fully charge the battery. If the bulk time is short, this means the battery was already charged and the resulting absorption time will also be short, whereas a longer bulk time will also result in a longer absorption time.

  • Storage mode

After completion of the absorption period the battery should be fully charged, and the voltage is lowered to the

float or standby level. If no discharge occurs during the next 24 hours, the voltage is reduced even further and the battery goes into storage mode. The lower storage voltage reduces corrosion of the positive plates.

Once every week the charge voltage is increased to the absorption level for a short period to compensate for selfdischarge (Battery Refresh mode

The above tips will help you to protect your battery from swelling up and expanding. Taking precautions will not only protect your battery from being damaged but it will also minimize the threat of fire caused due to overheating of the battery.

Click here for more information on Victron Energy AGM & Gel batteries