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Hybrid Battery Bank – Introduction


Part 0 (Intro) – What is a Hybrid Battery Bank?

Generally, people install Lead Acid Batteries in their Recreational Vehicles and Boats to run the everyday Habitation/House services.

There is increased interest in Lithium Batteries (and particularly the LiFePO4 style of Lithium) as they offer various benefits and advantages over Lead – however up-front cost is definitely not one!

But what about the idea of using both at the same time, maybe taking advantage of both Lead and Lithium at the same time?  Wouldn’t that be cool if it were possible?   Well, maybe it is ….

This is a discussion about the concept of having a Hybrid Bank comprised of both Lithium and Lead Acid batteries, broken down into a number of hopefully logical sections in different posts to make it more manageable to read. The following is a brief description of what to expect in each part and a quick link to each one if you want to skip to a specific area



Part 1 – Concept and the Theory behind a working Hybrid Battery

A Lead Acid Battery when fully charge tends to settle at a voltage of around 12.8V. As the battery gets used, the voltage drops in a very linear fashion. 
A Lithium Battery has a very different voltage/Amp-hour pattern. The Lithium Battery’s voltage is pretty flat until it gets to a fairly high Depth of Discharge (DoD), at which point the voltage drop starts to increase and when the DoD starts to get close to 100%, the Voltage really drops away and maybe the Lead Acid would start to come into play?

So based on just the mathematics of Voltages and comparing the two sets of numbers, would a Hybrid Battery work?  

Ok, time for some pretty pictures now. 


Part 2 – Data Analysis of the Hybrid Battery in Operation

We start off with the batteries fully and 100% charged.  Then pull the AC Hookup Plug and see what happens…  This section is inevitably full of graphs and numbers but shows well just how the Lithium Battery and the Lead Battery interact, both in terms of delivering power & energy to the user and also when recharging.


Part 3 – Charging Considerations

A Lead Acid Battery and a Lithium Battery have different charging characteristics and requirements.

One requires a certain voltage and tends to charge quite slowly. 
The other typically wants a lower voltage and charges much faster.

So how can you manage both when they are physically connected together?   The answer might surprise you


Part 4 – Conclusions

The previous parts took you through the concept and theory of a Lithium + Lead Acid Combination to create a Hybrid Battery Bank; 
then through the Analysis of how this works in practice;
followed by some considerations on optimizing the charging.


VSDR Lithium Controller

This section discusses in detail the logic and operation of the VSDR-200 Lithium Controller


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