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Discussion Starter #1
Im going to be using an advanced 24v dc motor running between 36-48v to get a bit more speed &power. I'm wanting to make my system be able to disconnect li-ion batteries output when the generator system comes on so they only charge.
I was thinking to use a step down converter for the regular automotive components. I figured a buck booster/DC-DC converter between li-ion battery charger/balancer/protection board and a 48v lead acid batterypack (acting as capacitor) that'll be connected to the generator system and motor for operating while main system is recharging letting the generator takes over the power consumption by charging the battery pack I'm having trouble figuring out what to use to control this switch for me. I'm going to connect some alternators to a small engine with electric start I want it to come one when the battery cells get close to 2.7-2.8v I'm using 3.7v lithium ion cells in series parallel to get the needed power.. I seen something for solar systems that was somewhat similar to my needs it would disconnect from a power system if it received power from a different one so if the grid was down and being worked on the solar system would be activated and doesn't power the grid and electrocute the workers but i think it had to be manually switched back
 

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I'm not sure exactly what you are trying to achieve, but assuming that this is a series hybrid propulsion system, the normal approach is to use a single battery and let that battery "float", and not disconnect it from the drive system at all. It is certainly not normal or advisable to combine a lead-acid battery and a lithium-ion battery, both at the drive system voltage. This sounds like an attempt to build a very complex solution for a non-existent problem.
 

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I originally thought about a single battery lead acid to store generated power so the charger could pull off it and wouldn't have to run generator system as much because lithium batteries don't last as long the more current used to charge and I figured it would be alot of wasted energy created if batteries wouldn't take the amount created from the generator
 

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So if I didn't use a battery for capacitance of unused energy and bridge the generator system to give batteries what's required for charging and uses the remaining energy for motor consumption to lighten the load from batteries when charging. I'd need to find a one way circuit for the power so the batteries aren't feeding the generator when its not running
 

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Do you have a diagram of your system and what is this generator thing doing?

Nobody makes an EV that has a generator. There is a 12V aux battery for "starting" and running the auxillary loads. The Li battery pack supplies power for the traction motor. There is no unused energy.

So we don't understand about this generator unless you show and tell.
 

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Discussion Starter #6
The generator is a range extension basically just a way to keep power to the system when you can't pull up to a charge station or plug into your household system. And to dampen the damage of a extremely large amount of batteries to get any distance per charge. I guess if you guys don't travel much in order to need the ability to get more than 75 miles then it wouldn't make sense to have a portable inexpensive way to charge without plugging into a external power source
 

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The generator is a range extension basically just a way to keep power to the system when you can't pull up to a charge station or plug into your household system. And to dampen the damage of a extremely large amount of batteries to get any distance per charge. I guess if you guys don't travel much in order to need the ability to get more than 75 miles then it wouldn't make sense to have a portable inexpensive way to charge without plugging into a external power source
Generator and "inexpensive" do not belong in the same sentence - your fuel consumption when using the generator will be impressive - and NOT in a good way
 

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Discussion Starter #8
A small brigs and Stratton motor would run on a single gallon of gas for a long time turning alternators cheap, and inexpensive all things that I have already have and would not use anywhere near the gas a regular automobile would especially considering how many days I drive 60 +miles
 

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The plan appears to be for a series plug-in hybrid. It is fashionable to call such a system a electric vehicle with range extender when the vehicle usually runs from stored energy in the battery, but it's still really a series plug-in hybrid.

There are lots of series plug-in hybrids, or at least plug-in hybrids which run at least part of the time in a series mode. Most are buses, but the BMW i3 is one, and one of the Honda hybrid systems (used in the Accord) works this way. None of them juggle two battery systems, let alone two dissimilar battery systems.
 

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A small brigs and Stratton motor would run on a single gallon of gas for a long time turning alternators cheap, and inexpensive all things that I have already have and would not use anywhere near the gas a regular automobile would especially considering how many days I drive 60 +miles
It doesn't matter how long the generator set runs; it matters how much electrical energy the generator produces. For any given amount of electrical energy, the Briggs & Stratton will burn more fuel than a modern automotive engine (driving a generator) producing the same amount of energy.

Yes, if you rarely exceed the range possible with your battery capacity, you won't burn much gas. This is why relatively poor efficiency when burning gas is tolerated in battery-oriented series hybrids such as the BMW i3.

Of course this is a forum for DIY conversions, and 'things that I already have' is a valid consideration. :)
 

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Discussion Starter #13
I didn't mean to say inverter to charge the battery I think what I was trying to say was wouldn't need a inverter to run a ac motor because I was referring/thinking about using dc.. I understand every time energy is converted from one type to another it requires some to do so so it's a loss of energy like magnetic energy to electric from electric to kinetic and even ac to dc and vise versa but I am not sure how much the loss is for the different types of conversion or if its such little loss that it is pointless worrying about I'm trying to get a better understanding so I can do it the best way to be efficient.. I appreciate the help and easily comprehendible explanations
 

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So It would not be a good idea to take say a alternator and replace the voltage regulator with one of the same voltage as the system's battery pack and charge the batteries and whatever power(amps the bms doesn't use be used as needed by the motor) that is basically what I had been referring to earlier. Theoretically it's a good idea at least I thought so when it came to mind
 
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