FLOATING BATTERIES ON 12volt SYSTEM

Submitted: Sunday, Jan 23, 2011 at 12:27

ThreadID: 83845 Views:3019 Replies:2 FollowUps:4

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kevmac

I have a 12volt(only) upright waeco fridge, powered by a Mobitronics rectifier when on 240 volts. Just trying to find out if anyone else has the same or suimilar setup and whether they float a 12 v battery across this to save having to unhook rectifier and hook up battery. Otherwise, does anyone have any ideas of how to set it up in an easy way, so that others with little knowledge could change over??? Appreciate any help or suggestions.

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Reply By: Battery Value Pty Ltd - Sunday, Jan 23, 2011 at 13:09

Sunday, Jan 23, 2011 at 13:09

hello,

if it's a simple transformer/rectifier, then the output voltage fluctuates with the mains 240V.
Check with a voltmeter if the output is around 13.8V and stable with fridge compressor cutting in and out.
If that's the case then yes, you can parallel a battery (don't forget to fuse near the positive battery terminal).
If battery gets discharged to less than 12.4V frequently (measured under load), it's recommended to use a proper three stage charger which adds an absorption stage to the charging process.
Generally, have the three stage charger work in power supply mode (13.6~13.8V) while the fridge is connected.
Once a week, or after a few discharges below 12.4V, put the charger in three stage charging mode which adds the much needed absorption stage.
Leaving the charger in three stage charging mode constantly while a fridge is connected may cause battery gassing.
While the method above does require some weekly user intervention, it guarantees maximum battery health.

cheers, Peter

AnswerID: 442799

Follow Up By: kevmac - Sunday, Jan 23, 2011 at 13:35

Sunday, Jan 23, 2011 at 13:35

Thx for that info much appreciated

FollowupID: 714820

Follow Up By: Member - Jason B (NSW) - Monday, Jan 24, 2011 at 12:02

Monday, Jan 24, 2011 at 12:02

Peter a quick question, on your post above I have 2 x engels running off 2 x 100amp AGM's I have a 3 stage 40amp charger and use it with a Honda 20ui when camping. I run the generator with the battery charger attached of an evening when camping for a number of hours (3 -6 hous).

From what you have said above to get the best battery life should I run the charger in power supply mode only of an evening, or should I just lets it charge as normal (work through the various programs) which is what I currently do. If its not to hot (temperature) I try and disconnect the fridges when the genny is running the charger of a night. When in a caravan park constantly hooked up to 240 I run it in the power supply mode.

Also is it advisable to leave the charger hooked up to the battery when at home as it has the float charge mode and it is apparently built to be left connected.

As with most of our fellow readers I whish to take the correct actions that prolong the life of the battery for as long as possible.

Thanks in advance.

FollowupID: 714926

Reply By: hazo - Sunday, Jan 23, 2011 at 14:29

Sunday, Jan 23, 2011 at 14:29

I have a Waeco HDC190 upright fridge freezer in my caravan also the Mobitronic unit.

There are a set of connections on my Mobitronic where the 12v batterys are connected permanently, the unit also plugs into 240v.

In my van it auto switches to the batterys if no shore power is available.

Also worth noting is the unit actually outputs 24v dc when on 240v and not 12vdc. The fridge is obviously designed this way and is probably slightly more efficient on 24v.

Unsure if there are two types of Mobitronic, but thats how mine is and its been working for 2 1/2 yrs now.

My batterys are charged by a full solar set up and a back up 3-stage smart charger.
It all works seamlessly in the background without any input from me apart from the odd check of the Led meter to see the batterys SOC.

AnswerID: 442802