Wednesday 14 March 2018

solar energy batteries




1/ Limited “Useable” Capacity

It is typically considered wise to use just 30% – 50% of the rated capacity of typical lead acid “Deep Cycle” batteries. This means that a 600 amp hour battery bank in practice only provides, at best, 300 amp hours of real capacity.
If you even occasionally drain the batteries more than this their life will be drastically cut short.
2/ Limited Cycle Life
Even if you are going easy on your batteries and are careful to never overly drain them, even the best deep cycle lead acid batteries are typically only good for 500-1000 cycles. If you are frequently tapping into your battery bank, this could mean that your batteries may need replacement after less than 2 years use.
3/ Slow & Inefficient Charging
The final 20% of lead acid battery capacity can not be “fast” charged. The first 80% can be “Bulk Charged” by a smart three-stage charger quickly (particularly AGM batteries can handle a high bulk charging current), but then the “Absorption” phase begins and the charging current drops off dramatically.


Just like a software development project, the final 20% of the work can end up taking 80% of the time.

This isn’t a big deal if you are charging plugged in overnight, but it is a huge issue if you have to leave your generator running for hours (which can be rather noisy and expensive to run). And if you are depending on solar and the sun sets before that final 20% has been topped off, you can easily end up with batteries that never actually get fully charged.
Not fully charging the final few percent would not be much of a problem in practice, if it wasn’t for the fact that a failure to regularly fully charge lead acid batteries prematurely ages them.
4/ Wasted Energy
In addition to all that wasted generator time, lead acid batteries suffer another efficiency issue – they waste as much as 15% of the energy put into them via inherent charging inefficiency. So if you provide 100 amps of power, you’ve only storing 85 amp hours.


This can be especially frustrating when charging via solar, when you are trying to squeeze as much efficiency out of every amp as possible before the sun goes down or gets covered up by clouds.
5/ Peukert’s Losses
The faster that you discharge a lead acid battery of any type, the less energy you can get out of it. This effect can be calculated by applying Peukert’s Law (named after German scientist W. Peukert), and in practice this means that high current loads like an air conditioner, a microwave or an induction cooktop can result in a lead acid battery bank being able to actually deliver as little as 60% of its normal capacity. This is a huge loss in capacity when you need it most…
Aftermath of Peukert losses on Lead acid fast discharge
The above example shows specification of Concord AGM battery : this spec states that the battery can provide 100% of it’s rated capacity if discharged in 20 hours (C/20). If discharged in one hour (C/1), only 60% of rated capacity will be delivered by the battery. This is direct effect of Peukert losses.
At the end of the day, an AGM battery rated for 100Ah at C/20 will provide a 30Ah usable capacity when discharged in one hour as 30Ah = 100Ah x 50% DoD x 60% (Peukert losses).
6/ Placement issues
Flooded lead acid batteries release noxious acidic gas while they are charging, and must be contained in a sealed battery box that is vented to the outside. They also must be stored upright, to avoid battery acid spills.
AGM batteries do not have these constraints, and can be placed in unventilated areas – even inside your living space. This is one of the reasons that AGM batteries have become so popular with sailors.
6/ Maintenance Requirements
Flooded lead acid batteries must be periodically topped off with distilled water, which can be a cumbersome maintenance chore if your battery bays are difficult to get to.
AGM and gel cells though are truly maintenance free. Being maintenance free comes with a downside though – a flooded cell battery that is accidentally overcharged can often be salvaged by replacing the water that boiled off. A gel or AGM battery that is overcharged is often irreversibly destroyed.
7/ Voltage Sag
A fully charged 12-volt lead acid battery starts off around 12.8 volts, but as it is drained the voltage drops steadily. The voltage drops below 12 volts when the battery still has 35% of its total capacity remaining, but some electronics may fail to operate with less than a full 12 volt supply. This “sag” effect can also lead to lights dimming.
8/ Size & Weight
A typical 8D sized battery that is commonly used for large battery banks is 20.5″ x 10.5″ x 9.5″. To pick a specific 8D example, Trojan’s 8D-AGM weighs 167lbs, and provides just 230 amp-hours of total capacity – which leaves you with 115 amp hours truly usable, and only 70 for a high discharge applications!
If you are designing for extensive boon docking, you will want at least four 8D’s, or as many as eight. That is a LOT of weight to be carting around that impacts your fuel economy.

Thursday 15 February 2018

electric vehicle battery



1/ Limited “Useable” Capacity

It is typically considered wise to use just 30% – 50% of the rated capacity of typical lead acid “Deep Cycle” batteries. This means that a 600 amp hour battery bank in practice only provides, at best, 300 amp hours of real capacity.

If you even occasionally drain the batteries more than this their life will be drastically cut short.
2/ Limited Cycle Life

Even if you are going easy on your batteries and are careful to never overly drain them, even the best deep cycle lead acid batteries are typically only good for 500-1000 cycles. If you are frequently tapping into your battery bank, this could mean that your batteries may need replacement after less than 2 years use.

3/ Slow & Inefficient Charging

The final 20% of lead acid battery capacity can not be “fast” charged. The first 80% can be “Bulk Charged” by a smart three-stage charger quickly (particularly AGM batteries can handle a high bulk charging current), but then the “Absorption” phase begins and the charging current drops off dramatically.

Just like a software development project, the final 20% of the work can end up taking 80% of the time.

This isn’t a big deal if you are charging plugged in overnight, but it is a huge issue if you have to leave your generator running for hours (which can be rather noisy and expensive to run). And if you are depending on solar and the sun sets before that final 20% has been topped off, you can easily end up with batteries that never actually get fully charged.

Not fully charging the final few percent would not be much of a problem in practice, if it wasn’t for the fact that a failure to regularly fully charge lead acid batteries prematurely ages them.

4/ Wasted Energy

In addition to all that wasted generator time, lead acid batteries suffer another efficiency issue – they waste as much as 15% of the energy put into them via inherent charging inefficiency. So if you provide 100 amps of power, you’ve only storing 85 amp hours.
Electric Vehicle Battery This can be especially frustrating when charging via solar, when you are trying to squeeze as much efficiency out of every amp as possible before the sun goes down or gets covered up by clouds.

5/ Peukert’s Losses

The faster that you discharge a lead acid battery of any type, the less energy you can get out of it. This effect can be calculated by applying Peukert’s Law (named after German scientist W. Peukert), and in practice this means that high current loads like an air conditioner, a microwave or an induction cooktop can result in a lead acid battery bank being able to actually deliver as little as 60% of its normal capacity. This is a huge loss in capacity when you need it most…

Aftermath of Peukert losses on Lead acid fast discharge

The above example shows specification of Concord AGM battery : this spec states that the battery can provide 100% of it’s rated capacity if discharged in 20 hours (C/20). If discharged in one hour (C/1), only 60% of rated capacity will be delivered by the battery. This is direct effect of Peukert losses.

At the end of the day, an AGM battery rated for 100Ah at C/20 will provide a 30Ah usable capacity when discharged in one hour as 30Ah = 100Ah x 50% DoD x 60% (Peukert losses).
6/ Placement issues

Flooded lead acid batteries release noxious acidic gas while they are charging, and must be contained in a sealed battery box that is vented to the outside. They also must be stored upright, to avoid battery acid spills.

AGM batteries do not have these constraints, and can be placed in unventilated areas – even inside your living space. This is one of the reasons that AGM batteries have become so popular with sailors.
6/ Maintenance Requirements

Flooded lead acid batteries must be periodically topped off with distilled water, which can be a cumbersome maintenance chore if your battery bays are difficult to get to.

AGM and gel cells though are truly maintenance free. Being maintenance free comes with a downside though – a flooded cell battery that is accidentally overcharged can often be salvaged by replacing the water that boiled off. A gel or AGM battery that is overcharged is often irreversibly destroyed.

7/ Voltage Sag

A fully charged 12-volt lead acid battery starts off around 12.8 volts, but as it is drained the voltage drops steadily. The voltage drops below 12 volts when the battery still has 35% of its total capacity remaining, but some electronics may fail to operate with less than a full 12 volt supply. This “sag” effect can also lead to lights dimming.

8/ Size & Weight

A typical 8D sized battery that is commonly used for large battery banks is 20.5″ x 10.5″ x 9.5″. To pick a specific 8D example, Trojan’s 8D-AGM weighs 167lbs, and provides just 230 amp-hours of total capacity – which leaves you with 115 amp hours truly usable, and only 70 for a high discharge applications!

If you are designing for extensive boon docking, you will want at least four 8D’s, or as many as eight. That is a LOT of weight to be carting around that impacts your fuel economy.



LiFePO4 batteries


We do not recommend using Lithium Batteries (for cranking) to start your engines.  You need the good ole-fashioned Lead-Acid or Gel Batteries for cranking power.

However, if you have a setarate battery or battery bank for all the other applications on your boat (A WISE IDEA), you want LifePO4 batteries.  LifePO4 technology lets you draw down your batteries over 90% compared to Lead Acid which permits maybe 50% and then they won’t start your engine(s).  Add this to 10xs the life cycles of traditional batteries and this is exactly what you want.. 
CURRENTLY OUR BATTERIES ARE ONLY USED FOR MARINE STORAGE AND NOT ENGINE CRANKING. 

Advantages of Lithium vs AGM Lead Acid Batteries:  
Superior “Useable” Capacity: Unlike with lead acid batteries, it is considered practical to regularly use 90% or more of the rated capacity of a lithium battery bank, and occasionally more. Consider a 100 amp hour battery – if it was lead acid you would be wise to use just 30 to 50 amp hours of juice, but with lithium you could tap into 90 amp hours or more.

Extended Cycle Life: Expect to see 2,000 to 5,000 cycles out of a well cared for LiFePO4 battery bank, which means that a lithium ion battery bank has the potential to likely outlast your RV!  In contrast, even the best deep cycle lead acid batteries are typically only good for 500-1000 cycles.
Fast & Efficient Charging: LiFePO4 batteries can be “fast” charged to 100% of capacity. Unlike with lead acid, there is no need for an absorption phase to get the final 20% stored. This can save you hours of generator run time. And, if your charger is powerful enough, lithium batteries can also be charged insanely fast. If you can provide enough charging amps – you can actually fully charge a lithium ion battery just 20 minutes! But even if you don’t manage to fully top off to 100%, no worries – unlike with lead acid, a failure to regularly fully charge LFP batteries does not damage the batteries.

Very Little Wasted Energy: Lead acid batteries are less efficient at storing power than lithium ion batteries. Lithium batteries charge at nearly 100% efficiency, compared to the 85% efficiency of most lead acid batteries. This can be especially important when charging via solar, when you are trying to squeeze as much efficiency out of every amp as possible before the sun goes down or gets covered up by clouds.

This also translates to less fuel costs when running your generator to charge the batteries.
Fewer Placement Issues: LiFePO4 batteries do not need to be stored upright, or in a vented battery compartment. They can also fairly easily be assembled into odd shapes – an advantage if you are trying to squeeze as much power as possible into a small compartment. This is especially useful if you have an existing battery bay that is limited in size, but you want or need more capacity than lead acid is currently able to provide.

Little Maintenance Requirements: Lithium batteries are maintenance free. A well designed energy management system should (ideally) blance and keep bank maintenance free.
Peukert’s Losses & Voltage Sag Virtually Non Existent: GET THE SAME VOLTAGE ALL THE TIME. The discharge curve of lithium batteries (especially relative to lead acid) is essentially flat – meaning that a 20% charged battery will be providing nearly the same output voltage as an 80% charged battery.