Year: 2019

Lithium-ion vs AGM Battery………………..

February 26, 2019

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

https://www.youtube.com/watch?v=pnCJFXWEVYs

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

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.

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

Lead Acid – Discharge Capacity vs Terminal Voltage

Useable Energy (Lead Acid)

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.

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.

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

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How to Choose Solar Panels in Ghana

February 20, 2019

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How to Choose Solar Panels in Ghana will always be a major question . This is due the the wide assortment of varieties available and the lack of expertise in this specialized area of electrical energy.Solar panels provide renewable energy for your home, which helps the environment and reduces your electricity bill. But not all panels are alike. The material a panel is made of, what solar inverter it uses, and how it mounts to your roof determines what environments it works best in. Before you buy solar panels for your home, research the different factors and decide which option is right for you in Ghana.

Ghana has an average effective sunshine of 5.5 hours daily .As a considerable investment, it’s worth evaluating a solar power system for your home before have it installed. Doing your research and seeking professional advice can help you to make an informed decision. Here are a couple of other things to consider before making the change:

Types of Solar panels in Ghana

There are different types of solar cells, with different efficiencies. Although their names might sound confusing, it is good to know at least the name not to be out-of-topic if your supplier happens to mention this.Popular solar panel brands in Ghana include ,Jinko solar,Victron Energy,TrinaSolar LG,Yingli, and Canadian Solar.Its however important to seek the advice from a professional as there are many knock offs or fake products on the Ghana market.

Monocrystalline silicon offers high efficiency and good heat tolerance characteristics with a small footprint. Polycrystalline (or multi-crystalline) silicon cell based solar panels are now the most popular choice in Ghana’s residential installs. There are also Amorphous (or thin-film) silicon cells, which use the least amount of silicon and are not very efficient. For an equivalent wattage, a crystalline panel will be smaller than an amorphous panel.

monocrystalline solar panels in Ghana installed on a rooftop

Choose monocrystalline solar panels for efficiency. Monocrystalline solar panels are the best at converting light to energy because of their high silicon purity. That being said, monocrystalline solar panels are often the most expensive—this option is best if you want the highest productivity and price tag.

Monocrystalline solar panels cost between $150-350 USD per panel.
Monocrystalline solar panels also produce the most waste when they’re manufactured. If you’re buying solar panels to go green, another material may suit your needs better.
All solar panels are made of silicon. The higher the silicon purity, the better your panel will work, which is why monocrystalline solar panels in Ghana are ideal.

Go with polycrystalline solar panels for an environmentally-friendly option.Polycrystalline solar panels utilize all of the silicon material they’re manufactured with, making them the “greenest” panel option. Polycrystalline solar panels are also cheaper than mono crystalline panels, though they are about 2% less efficient than Mono crystalline.

Polycrystalline solar panels in Ghana usually cost between $100-250 USD per panel.
other school of thought claim that Polycrystalline solar panels do not do as well in warm temperatures and that Hot climates with temperatures regularly above around 80 °F (27 °C) are not suitable for polycrystalline panels.This may be true depending on the installation technique utilized.Its important to allow steady air flow underneath the solar panels to produce cooling effect.

Buy thin-film solar panels for the most budget-friendly option. Thin-film panels are cost-efficient to make and are usually the cheapest option. They also, however, degrade faster than other panels. Choose thin-film if you need a simple solar panel that may need more repairs over the years.

There is also another variation called solar cloth i.e photovoltaic textiles we have developed are as thin as bank notes and flexible enough to wrap around a pencil, which allows their use on virtually any type of surface

Thin film solar panels usually cost between $125-200 USD per panel.
Thin-film panels usually need the most space and are less practical for smaller homes. They may need up to twice as much room as a mono- or polycrystalline solar panel with the same energy output.

Buy amorphous solar panels for smaller homes

Amorphous solar panels are a subset of thin-film solar panels. Generally, they are smaller than other thin-film panels. Through a process called “stacking,” which involves multiple layers of amorphous silicon cells, these panels can reach high levels of efficiency, around twice as high as other thin-film solar panels.

Amorphous solar panels are more expensive than other thin-film panels.
Amorphous solar panels generally cost between $100-200 USD per panel.

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Solar Cloth:producing power from textiles everywhere

February 19, 2019

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Solar Cloth:producing power from textiles everywhere .we always need to keep our eye on emerging technologies and how they may relate to our products, both now and in the future. Solar cloth is one such technology that has certainly got me excited. You can see the solar cloth panels embedded in the mainsail of the yacht above, which is ideal as deck area for conventional modules is limited on sailing yachts.

Solar cloth is not just for boats though. Yesterday I spoke to Alain Janet from solarclothsystem.com and learned that it can also be integrated into canopies, to provide power for outdoor events for example or indeed to recharge electric vehicles. Even an awning for an RV or overland 4 x 4 could probably use such a system too.

However, Alain is a sailmaker to trade and naturally it is in that field that his first system is to be deployed, with UK Sailmakers (France). The UK Sailmakers group has over 50 lofts and service centers around the world, so to my mind they are well placed to bring this technology to market.

Below is a press release, concerning these new PowerSails.

SOLAR SAILS TO POWER TRANS-ATLANTIC RACER

Frenchman Daniel Ecalard has entered his Open 50 DEFI MARTINIQUE in the 3,500-mile Route du Rhum from St. Malo, France to Guadeloupe in the Caribbean. His goal: to complete the race with zero carbon emissions. Ecalard plans to carry no diesel for generating electricity in a boat that bristles with electronics that do everything from communicating and navigating to making water and moving the boat’s canting keel.

He will use the boat as a test bed for clean energy solutions. His primary source of power will be solar panels laminated into his Titanium® mainsail to cover all the boat’s electrical needs. The sails are being made by UK Sailmakers France, which has developed the technology for solar cells that can be either laminated to new sails or affixed to existing sails. This exclusive technology is called PowerSails and is being developed by Alain Janet, owner of UK Sailmakers France.

These cutting-edge, light-weight films can generate electricity in low light and indirect sunlight. They are supple enough to handle the sail being luffed as well as folded. The panels will be put in the upper part of the main, above the third reef.

Janet says that the mainsail for DEFI MARTINIQUE is expected to produce on average 500 Watts per hour, budget allowing. Ecalard’s boat was built in 1998 for that year’s BOC race. In 2002-2003, Brad Van Liew won the 50-footer division of the 30,000-mile Alone Around Race by winning all four legs with this boat. She still holds the 24-hour distance record for a singlehanded 50-footer when she went 345 miles in a day. In 2008, she won her class in the Newport Bermuda race. In 2010 the boat starred in the Hollywood movie “Charlie St. Cloud” where Solar Cloth:producing power from textiles everywhere

Ecalard’s ultimate goal is to build a sailing freighter for working the inter-island trade in the Caribbean. For more information about this project go to: http://seafretcaraibes.fr/

Credits

Our thanks to Adam Loory of UK Sailmakers International for the interview and text above, with RDR (Route du Rhum) skipper Daniel Ecalard.

As a footnote, we also wish Alain all the best for his PowerSails project. And if there is a place for Victron to assist, then I’m sure we will as emerging markets and technologies are surely a key to business growth for all. So, if on your Victron travels you too come across something new, that is noteworthy of a post here on the Victron blog, do let us know.

John Rushworth

Official opening: VICTRON-Competence Centre, Klagenfurt

February 15, 2019

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Official opening: VICTRON-Competence Centre, Klagenfurt

A little over a year ago Victron Energy in association with Austrian Victron Energy dealer E-BOX Off-Grid Power Systems, together with HTL1 Lastenstraße and their headmaster Dr. Michael Archer forged a partnership to utilise Victron Energy products for their varied educational program – to build a ‘Competence Centre’.

As a result on Thursday, 5th December 2018, the new VICTRON-Kompetenzzentrum (VICTRON-Competence Centre) for ‘Renewable Energy and Storage Technology’ was opened at the school.

HTL1 Lastenstraße is a Higher Technical Institute in Klagenfurt, southern Austria, with around 1100 students and 120 teachers. The school trains engineers in the fields of mechanical engineering, electrical engineering and mechatronics. It has around 34 workshops and laboratories as well as several competence centres. Another focus is ‘Land und Umwelttechnik’ (agricultural engineering and environmental technology).

This all makes HTL1 a unique training centre, not only for students from Carinthia but southern, eastern and western Austria. With the new VICTRON-Competence Centre training courses will specialise in the fields of energy storage technology, photovoltaics and energy management. Besides these courses Victron Energy have also been welcomed to run their own special courses at the school. In addition, interested companies will also have the opportunity to use this modern infrastructure for their own education and training events.

HTL1 Lastenstraße – The school is equipped with many different, modern photovoltaic-systems.

The school were particularly pleased to receive a visit from Victron Energy sales manager Leo Yntema for the opening. Here’s a brief video (in German) of that visit and a few photos from the opening event.

https://youtu.be/r9wasVuZIUU

From left to right: Manfred Hartner – Managing Director of E-BOX Off-Grid Power Systems, Dr. Michael Archer – Principal of HTL1 Lastenstraße and Leo Yntema of Victron Energy.

A student explains one of the 5 Workstations and its components at the opening.

From left to right: Andreas Albel, the teacher who is responsible for the VICTRON-Kompetenzzentrum and Leo Yntema of Victron Energy.

Equipment utilised

There are 5 workstations utilising Victron Energy equipment. Each workstation is equipped with its own separate 3kWp photovoltaic-system, plus each of the panels can be switched on and off separately.

Workstation 1: components / power storage / 3-phase

3 x MultiPlus 48/3000/35-16
1 x Color Control GX
1 x Battery Monitor BMV-700
4 x LiFePO4 battery 12.8V/90Ah – BMS
1 x Battery Management System VE.Bus

Workstation 2: components / power storage / 1-phase

1 x MultiPlus 48/3000/35-16
1 x Color Control GX
1 x Wall mount enclosure for Color Control GX
1 x Battery Monitor BMV-700

Workstation 3: components / power storage / 1-phase

1 x ECOmulti 24/3000/70-50 2,3 kWh LiFePO4
2 x LiFePO4 battery 12.8V/90Ah – BMS

Workstation 4: Components / power storage / DC coupled

1 x BlueSolar MPPT 150/85 CAN-bus
1 x Wall mount enclosure for Color Control GX
1 x Battery Monitor BMV-700
1 x Venus GX
24 x OPzV 200 Batteries

Workstation 5: Components / power storage / DC coupled

1 x EasySolar 48/3000/35 MPPT 150/70 with Color Control GX built-in
24 x OPzV 200 Batteries

Conclusion

It’s great to see the new VICTRON-Competence Centre now open and we trust it will serve as a valuable resource for the school and the young engineers of tomorrow.

This artcle was orriginally published on the victron blog by John Rushworth on January 31st, 2019

Links

Interview with Dr. Archer – https://www.victronenergy.com/blog/2017/11/13/back-to-school-with-victron-energy/

HTL1 Lastenstraße Klagenfurt Website – http://htl1-klagenfurt.at/index.php/en/

HTL1 Lastenstraße Klagenfurt on Facebook – https://www.facebook.com/HTL1.Klagenfurt/

E-BOX Off-Grid Power Systems Website – http://www.e-box.co.at

Siemens partners WestPark for industrial park in Takoradi

February 13, 2019

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Siemens partners WestPark for industrial park in Takoradi

Siemens has announced it has signed a Memorandum of Understanding (MOU) with WestPark Enterprises to develop an expandable microgrid solution for the fast-growing industrial and business park based in Takoradi, Western Ghana.

The Westpark aims to eliminate many of the challenges faced by companies doing business in Sub-Sahara Africa, such as access to reliable power, water, broadband internet and transport.

The new industrial park is poised to accelerate the transformation of Takoradi – Ghana’s third-largest city.To lay the foundations for reliable, competitive and efficient energy, WestPark has entered into a partnership with Siemens.

As part of the agreement, Siemens will develop a 250kW microgrid that controls the energy generation for the initial phase of buildings to be constructed at WestPark.

Siemens will design the microgrid so that the first phase of WestPark can be powered entirely by renewable energy and therefore provide a sustainable and cost-effective solution for tenants.

On-site photovoltaic panels will power the microgrid and a back-up battery storage solution will be sourced as well.

The grid can be expanded as more buildings are added with the aim of ensuring that the park remains powered by renewable energy.

According to Sabine Dall’Omo, CEO of Siemens Southern and Eastern Africa, “This project is perfectly in line with Siemens’ vision for future business in Ghana and other African countries. As a company, we are continuously looking for new responsible and efficient energy and infrastructure solutions, and our collaboration with WestPark is a good example of how we can support partners with similar goals.”

Siemens is specifically committed to economic growth across Africa, and in doing so in a forward-thinking manner by implementing environmentally sustainable solutions that will help its partners and customers succeed in today’s environmentally-conscious global market.

Siemens AG is a German conglomerate company headquartered in Berlin and Munich and the largest industrial manufacturing company in Europe with branch offices abroad. The principal divisions of the company are Industry, Energy, Healthcare, and Infrastructure & Cities, which represent the main activities of the company.

Victron Energy Phoenix Inverter Smart – out now

February 12, 2019

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We’ve just added two Bluetooth enabled Inverters to our range. The new-build Victron Energy Phoenix Inverter Smart models are rated at 1600VA and 2000VA and we have models for 12V, 24V and 48V systems.

Dynamic cut-off/intelligent restart
We’ve added 48V models to the range
Bluetooth communication – allows easy set-up and monitoring on your phone, laptop or smart device
Slimline design allows for discreet wall-mounting
Eco mode

Bluetooth …and VE.Direct

Bluetooth has been built in to the Victron Energy Phoenix Inverter Smart – allowing your power consumption to be monitored, or the settings changed, straight from your phone, tablet or laptop via our VictronConnectapp – which is free to use. Victron Energy Phoenix Inverter Smart also has a VE.Direct communication port allowing wired connection to a tablet or laptop via an optional VE.Direct to USB cable. The unit can then be set-up and programmed using VE Configure software.

Built in Bluetooth allows you to view live data on your mobile phone, laptop or smart device via our VictronConnect app – which is free to use.

Dynamic Cut-off

Your battery is protected by a user-defined low voltage alarm.

The alarm will be followed by an automatic cut-off – the value of which is Dynamic: For example, if the inverter is providing a lot of power at the time a low-voltage condition is detected, the unit will perform its disconnect at a lower battery-voltage than if it were providing only a modest amount of power. When only a modest amount of power is being drawn, cut-off will take place immediately a low-voltage condition exists. See the Manual for full details.

Intelligent re-start

A cut-off will be followed by three intelligent restart attempts. If the cut-off was triggered by a sudden but temporary drop in voltage, the load will be reconnected. A thirty-second delay ensures that the increase in voltage which has been detected is enduring.

ECO mode

In ECO mode some Victron Energy Phoenix Inverter Smart units consume just 0.6 watts – so they can be left in ‘standby’ for extended periods without worrying about the battery running down between jobs. ECO mode is intelligent, too: When the power being provided by the device falls below a certain value – it will automatically enter standby mode. As soon as it detects a load above a preset ‘snooze’ limit, the unit will remain on, to power this new demand.

LED diagnostics

Similarly to its predecessors, the Phoenix Inverter Smart is equipped with ‘traffic-light’ LED’s – the behaviour of which relate to the Inverter’s current ‘status’ – providing you with information concerning which mode the unit is in, whether any alarm conditions exist, or if an automatic trip has taken place. In depth information can be found in the manual. Bluetooth connection to your smart device provides deeper analysis.

The Victron Energy Phoenix Inverter Smart – which weighs around 12kg – can be tidily installed in an out-of-the-way location, thanks to its slim profile, and sturdy mounting plate. But if it’s tucked away – what about reaching it …to turn it on and off? No problem – a remote on/off switch is available.

Summary

True Sine Wave power output can be used for sensitive electronics such as computers; and it’s Peak Power capability – of around twice its ‘continuous’ rating – will supply the inrush current typically drawn by workshop tools such as drills, jig-saws, sanders and LED lamps. It can continuously power all the comforts of home – such as Microwave cookers, vacuum cleaners – even pressure washers.

Phoenix Inverter Smart continues to use ultra-reliable ‘full bridge’ configuration and toroidal transformer topology – all housed in a stainless steel case – to provide years of worry-free service.

Phoenix Inverter Smart is a protected against short-circuit, and overheating.

Inverters for every requirement

We have Inverters, and Inverter/Chargers for every possible requirement – from compact 175W models to 144kW – configurable for 3-Phase; Multi source AC; and even for Assisting Grid-Power. In Ghana call +2332442700092 or visit our facebook page to find the right Inverter for you.

Lead acid battery charging in cold weather

January 11, 2019

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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