Battery Maintainer Float voltage

[rodster_67]

This may take a little work, you'll have to pull out the DVM and measure, but what is the battery voltage when tender/charger is in maintain mode?

Over the years I've had several brands a the voltage ranges from 12.7 vdc - 13.2 vdc.

I was told a good battery will have a voltage of ~12.6 vdc at rest with no tender attached.

Is there an optimum float voltage?

I'm curious what the better brands (NOCO, CTEK, Battery Tender) float at compared to the cheap units.

 

[MikeF2316]

You might want to give this thread a read.

 

[rodster_67]

Already did, I started that thread too.

The purpose of that thread was to alert people that their maintainer may not be even tho' the lights say it is. I noticed one of my maintainers was at less than 12.6vdc but indicator lights showed full charge.

The purpose of this thread is to find out what voltage people have noticed their maintainers hold in float mode.

My original post mentioned 13.2vdc but I also have one maintainer that holds at 13.55vdc.

My next step it to put a ammeter inline with the clamp to see what, if any, is the current draw is in float mode.

 

[MBfreak]

6 cell lead acid ( closed or vented) ( From an unitrode manual for UC 3906 chip)
Start by charging it with the rated Ah capacity divided by 10h. So a 60 Ah would be 6 A. This is the bulk charge in current limit mode.
When you get to around 12,5 V terminal voltage , use the same current limit and a voltage ref of 14,25 V.
When terminal voltage reached 14,25 and is held, the charging current will start to taper of. When it reaches 0,6 A switch voltage reference to 13,80 V for the float charge.
This way the battery will be fully charged with a minimum of hydrogen loss and the float charge of 13,85 will maintain it at full charge.

Ola

 

[MikeF2316]

Already did, I started that thread too.

The purpose of that thread was to alert people that their maintainer may not be even tho' the lights say it is. I noticed one of my maintainers was at less than 12.6vdc but indicator lights showed full charge.

The purpose of this thread is to find out what voltage people have noticed their maintainers hold in float mode.

My original post mentioned 13.2vdc but I also have one maintainer that holds at 13.55vdc.

My next step it to put a ammeter inline with the clamp to see what, if any, is the current draw is in float mode.

Haha, so you did. My maintainers get the summer off.

 

[redmondjp]

Some battery maintainers turn their outputs on and off (but monitor battery voltage continuously to determine when to turn back on). One must be aware of this when trying to monitor the output of the maintainer.

One way I would recommend to do it is to use a recording DVM such as a Fluke 189. You can easily see what is going on then over several hours without having to be there.

 

[Fretters]

Provided it's between 13.2V and 13.8V, you're fine. Older type batteries are fairly forgiving with regards to specifics. It's merely SLA's which are arsey beggars with regards voltage. Anything which is unregulated will always show a higher voltage off load, btw, and the newer "intelligent" chargers likely won't read anything off load.

 

[jkwilson]

Different battery technologies have different requirements. Float voltage is generally chosen to provide just a little current into the battery while remaining below the gassing point to avoid excessive water consumption. 13.2V to 13.4V is the common range.

Commonly available batteries vary from 12.64V to around 13.1V full charge voltage, so you'll see float voltages a little above that range.

An important thing to understand is that a charger goes into maintain mode based on battery current draw. If the battery is old, it may draw excess current and the charger may never switch to maintain mode. This will pretty quickly result in a dry battery. Often the failure is blamed on the charger when it was the battery that caused the charger to keep charging. The same thing can happen when there is a load on the battery during charging. Even something like a dome light in a car can draw enough current to keep the charger in charging mode and can lead to a damaged battery.