Tapping A Battery For Different Voltages, Non-Standard Batteries

[JeepHammer]

Very few seem to get the idea of 'Tapping' (or Taps) in battery strings.
A 'Tap' is pulling a specific voltage from a higher voltage battery, or Series wired string of batteries.

You CAN both charge and discharge a 24 or 48 volt battery string as 12 volt batteries,
And you can do that from anywhere in the Series string.

12 Volt Batteries,
2 ea. 12 volt chargers will do a fine job charging a 24 volt Series string.

6 Volt Batteries,
4 ea. 6 volt chargers will do a fine job charging a 24 volt Series string.

This is how we 'Charge Balanced' batteries still in a string before all the high end and multi-voltage equipment came along, and in some ways gives better balancing since each battery is 'Chased' by a single charger.

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Direct Current is a 'Closed Loop', a 'Circuit',
The electrical current will SEEK it's own source to complete it's own circuit, or closed loop, 'Ignoring' any other circuit connected to the same terminals.

Most people 'Assume' DC is like AC that will seek ANY 'Ground', the shortest path to 'Ground', that simply isn't the case with DC.
DC seeks it's OWN current source.

*IF* you need 12 volts from ANY battery in a 24, 36 or 48 volt Series string, you simply attach your positive & negative cables to a single 12 volt battery and draw 12 volts from it.
This WILL unbalance the batteries since you are drawing current from a single battery, but for small loads it will not unbalance the string enough to worry about.

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While I don't have any fork truck batteries anymore for pictures, fork truck batteries have exposed connections between cells.
These exposed connections (also called 'Bridges') you can very effectively charge a 24 or 48 volt battery with 6 volt or 12 volt chargers simply by connecting to the appropriate number of cells.

This is a fairly common battery used in race cars, it is 16 volts at the end terminals.
While the entire battery gets an 18 volt charge, there is a 12 volt 'Tap' for sensitive electronics.
Some racing ignition systems and electronic fuel injection systems won't tolerate 16 volts, so a 12 volt Tap is provided for that sensitive equipment.

Just throwing this out there for the guys that don't know about this...

 

[erik.calco]

@JeepHammer How does that 16V rebalance after you tap it?

BTW, have been trying to collect useful info like this into this thread.

 

[JeepHammer]

It's a Gel Cell, lead/acid, so just charging the battery as a 16 volt battery charges all cells.

If you were REALLY OCD you could charge/balance the 12 volt cells with a 12 volt charger,
Then charge between 12 volt terminal and 16 volt terminal with a 4 volt charger.

When connected (negative) at the 12 volt terminal, and (positive) at the 16 volt terminal, it's a closed DC circuit, and with a 4 volt charger you would only reach the last two cells in the battery.

 

[erik.calco]

It's a Gel Cell, lead/acid, so just charging the battery as a 16 volt battery charges all cells.

If you were REALLY OCD you could charge/balance the 12 volt cells with a 12 volt charger,
Then charge between 12 volt terminal and 16 volt terminal with a 4 volt charger.

When connected (negative) at the 12 volt terminal, and (positive) at the 16 volt terminal, it's a closed DC circuit, and with a 4 volt charger you would only reach the last two cells in the battery.

I was just wondering if it had a balancer in it. The obvious risk is you drain the 12V then charge the 16V. You saying that wouldn't be a problem because it is LA?

 

[SolarRat]

Excellent to know as when i change my 6v floodeds into a 24 system i can then hook-up the 12v inverter to a series of 2, plus run my 12 volt solar charger on THAT pair!

Cool!

An inverter is way too big of a load for doing what the OP s talking about. It would greatly throw off the balance between batteries. This tapping is just a work-around for very small loads only.

 

[erik.calco]

An inverter is way too big of a load for doing what the OP s talking about. It would greatly throw off the balance between batteries. This tapping is just a work-around for very small loads only.

And today's puzzle... how can you run two 12V batteries in series and parallel at the same time? lol

 

[JeepHammer]

I was just wondering if it had a balancer in it. The obvious risk is you drain the 12V then charge the 16V. You saying that wouldn't be a problem because it is LA?

Race car batteries get charged going in a circle (alternator) or between rounds (short & straight).

What I do when some dummy leave a switch on is draw down the last two cells, then charge the entire thing at 16+ volts.
You can also charge the 6 cells on a 12+ charger.
Lead/acid is quite forgiving.