I have this issue with lots of transformerless inverters and seem to be troubling.

I have a hobby building Batteries from 18650 Lithium-ion batteries and most times I build 3S (4.2v x 3 = 12.6v Full Charge) for friends but the small transformerless inverters I recommend to be used with the batteries only works from 11v - 15v which doesn't allow good use of the battery.

My 3S build has a range of 9V - 12.6V and 4S is 12V - 16.8V (3v - 4.2v per cell) These inverters couldn't fit properly into these two battery build.

Does anyone have an idea on how to hack these units to make it fit? Any link to a circuit?

Thanks.

 

It is difficult to make suggestions without knowing what it is that you would like to change. Can you post a schematic of your 3S?

 

It is difficult to make suggestions without knowing what it is that you would like to change. Can you post a schematic of your 3S?

Thank you Cappels.

1. What I would like to change is the "Operational voltage range" in which the inverter works.

2. 3S is just 3 x 18650 Cell connected in series to output 12v at 4.2v per Cell Voltage

So the regular 12v transformerless inverter works with batteries with voltages from 15v-full charge down to 11v-Low Battery. The batteries with these voltage ranges are Lead Acid batteries/LifePo4 but I easily build batteries out of Lithium-ion which voltage range is (12.6v-full down to 9v-Low for 3S Battery) and then (16.8v-full down to 12v-Low for 4S Battery)

The inverter with a 3S battery would shut down at 11v when there's still enough juice in the battery and would report over voltage at 16v with a 4S battery.

I hope you understand now. Thanks.

 

I guess I should have asked for a schematic of the circuit you want to modify, or would you like to build a new one.

You must be careful to not incorrectly charge or let your lithium batters fully discharge

 

I guess I should have asked for a schematic of the circuit you want to modify, or would you like to build a new one.

You must be careful to not incorrectly charge or let your lithium batters fully discharge

I don't have the Inverter schematic. I can look up one and share. I just thought maybe someone would have and have tried it.

My batteries are well built and managed so overcharging is always in-check.

 

I would guess that You want to be able to charge higher-Voltage-Batteries from
a nominal ~12-Volt Lead-Acid-Battery.
If this is the case,
then what You need is a "Buck-Boost-Regulator",
which can increase the Charging-Voltage higher than a nominal ~12-Volts.

BUT, this needs to be in the form of a proper, commercially-available, Hobby/RC Battery-Charger,
that will properly handle the required Balancing of the Cells,
and to carefully control the Charging-Current and Voltage,
so that You don't inadvertently start a FIRE that You can't put out.
.
.
.

 

I would guess that You want to be able to charge higher-Voltage-Batteries from
a nominal ~12-Volt Lead-Acid-Battery.

Thanks LowQCab.

I want the inverter to either work from 12v down to 9v dc voltage

OR

Accept DC voltage from 17v downwards

 

I'm still not exactly sure about what You are trying to accomplish.

However,
The wider the difference between the Input-Voltage and the Output-Voltage,
the more complex, costly, and less efficient, this conversion becomes.

A Toroidal-Transformer equipped, Push-Pull, Regulated-Power-Supply may be required.
And, it will be the most efficient solution,
but it will be larger and more expensive than a heavily compromised Buck-Boost-Converter,
and it will be Electrically less "Noisy", and have much greater stability.
.
.
.

 

What type of “inverter” are you talking about here? A 12V inverter normally refers to a device that takes in 12VDC and outputs 120 or 240VAC, but I doubt that is what you are talking about.

Can you link to an example of the device?

 

You would need to know the input circuitry of the inverter before you could decide if modification would be possible/straightforward. A lowered input voltage would require greater input current for a given output power, so might need beefier semiconductors, for example.

 

My 3S build has a range of 9V - 12.6V and 4S is 12V - 16.8V (3v - 4.2v per cell) These inverters couldn't fit properly into these two battery build.
Does anyone have an idea on how to hack these units to make it fit? Any link to a circuit?

3S 11.1V LiPo Battery USB 5V 500mA Balance Charger
$6.13

 

What type of “inverter” are you talking about here? A 12V inverter normally refers to a device that takes in 12VDC and outputs 120 or 240VAC, but I doubt that is what you are talking about.

Can you link to an example of the device?

I'm talking about the 12v DC - 220v AC inverters. (Pic attached)