Battery Charger help needed

[Norman_E]

I have a Waeco Mobitronic 925 012 battery charger, which is an automatic 25amp IUoU charger. It claims to charge to 14.4 volts then switch to float mode at 13.8 volts. All my batteries are "maintenance free" sealed lead acid, and I think they should be charged to a lower voltage (14.1?).

Does anyone know if I can adjust the charging voltage, if so how. I cannot find any manual for this fairly old model, and it has no switch for different battery types.

If it is not adjustable, what should I replace it with?

 

[pvb]

I have a Waeco Mobitronic 925 012 battery charger, which is an automatic 25amp IUoU charger. It claims to charge to 14.4 volts then switch to float mode at 13.8 volts. All my batteries are "maintenance free" sealed lead acid, and I think they should be charged to a lower voltage (14.1?).

Does anyone know if I can adjust the charging voltage, if so how. I cannot find any manual for this fairly old model, and it has no switch for different battery types.

If it is not adjustable, what should I replace it with?

Maintenance free batteries are fine being charged at 14.4 volts - don't worry about it.

The manual for the charger is here on the Waeco website.

 

[BabaYaga]

All my batteries are "maintenance free" sealed lead acid, and I think they should be charged to a lower voltage (14.1?).

Others might know better, but my understanding is that charging to 14,4 v is perfectly OK for sealed lead acid. This is also in line with recommendations from most charger manufacturers as far as I know.
What might be an issue for sealed lead acid is the amount of time that the voltage stays at 14,4, that is at what point the charger switches from absorbtion to float mode. Could be a fixed time or a current set point (or a combination).
There is a risk that the time on spent on high voltage gets too long and dries the batteries out. For instance if the power supply is interrupted (timer starts from zero again?) or if there is a load on while charging (current does not fall back to set point).

 

[Plevier]

Can you please clarify what you have? It makes a difference and it's an area with lots of confusion.

The car battery industry says "sealed maintenance free" to mean an ordinary wet battery but with a larger reserve of liquid in it and without apparent means of topping up. Often the vent plugs are just hidden by a label in fact. It's a marketing device not a real technical solution! In the small print you'll find "maintenance free" only applies if you limit the charging voltage to 13.8V or 14V or something like that, in your case maybe that's where the 14.1 comes from? This will give you a fairly slow recharge. If you exceed that with a multi rate charger to get a quicker charge you will eventually lose some water and then you will have to find out how to top up. Not usually difficult.

If you mean "valve regulated sealed lead acid" also known as AGM, AGR, or recombination, the sort with no free liquid in that you can turn upside down and so on, 14.4V is fine if not on permanently. Better to have a charger that senses voltage to go off boost rather than giving 4 or 5 hours boost every time you switch on regardless of the state of charge, so yours sounds fine.

 

[Georgio]

As others have stated 14.4 should not cause any gassing of the batteries.

 

[Norman_E]

Can you please clarify what you have? It makes a difference and it's an area with lots of confusion.

They are the wet type, but with completely sealed plugs and no way of ever topping up.

 

[ghostlymoron]

I've often wondered whether it would be possible to drill 2 small holes into each cell and top up a 'maintenance free' battery. Hmmmmmmmmmmm

 

[VicS]

I've often wondered whether it would be possible to drill 2 small holes into each cell and top up a 'maintenance free' battery. Hmmmmmmmmmmm

Sometimes you can remove the label on the top of the battery and then remove the top cover to access normal filling holes. But they don't take kindly to being removed too often

It would be a mistake to drill holes in a valve regulated battery!

Best solution IMHO is to buy conventional non sealed batteries that can be topped up when required.

Also confirming 14.4 is OK as the charging volts.

 

[Plevier]

They are the wet type, but with completely sealed plugs and no way of ever topping up.

That's unusual. No flush fitting lever out panel under a label on top? It has to be vented somewhere.
I would still stay at 14.4 personally as you have a voltage sensing not timed charger. Should be OK.
If you observe the water level dropping - can you see it? - in a year or so find how to top up or find how to turn down the wick in the charger.

 

[Norman_E]

I am getting a bit concerned about the charger. I have been checking voltage at the battery terminals with a digital voltmeter. Highest reading so far is 14.51 volts, so the charger is definitely not always going into float mode once 14.4 volts is reached. The charger does not appear to have any means of adjusting its switching point.

 

[pvb]

I am getting a bit concerned about the charger. I have been checking voltage at the battery terminals with a digital voltmeter. Highest reading so far is 14.51 volts, so the charger is definitely not always going into float mode once 14.4 volts is reached. The charger does not appear to have any means of adjusting its switching point.

If you look at the charger's user manual (the link I posted earlier), you'll see that it has the ability to select different periods for the "main charging phase". The options are 4 hours, 8 hours and continuous. Could it be that yours is set to continuous?

Regardless, 14.5 volts shouldn't harm your batteries.

 

[VicS]

I am getting a bit concerned about the charger. I have been checking voltage at the battery terminals with a digital voltmeter. Highest reading so far is 14.51 volts, so the charger is definitely not always going into float mode once 14.4 volts is reached. The charger does not appear to have any means of adjusting its switching point.

What is the current doing.

Mine ramps up ( soft start) to the max current that I have set ( depends on the size of battery)
It holds that maximum current until the volts reach 14.4 then it holds 14.4volts until the current has dropped to some figure I have not yet established but possibly depends on the max figure set.

Then it goes through testing phases and additional charging if necessary before eventually going into float mode. It seems to float at a fixed current rather than a fixed voltage which is odd.

I really have not figured out quite what it is doing some of the time but the point is charges at 14.4 until the current has dropped back to some predetermined level. Maybe you are not reaching that point.

The volts and amps displayed don't agree with my multimeter either!

 

[Plevier]

The manual shows that with an internal switch you can select for 14.4V or 14.8V, have you checked the setting?
It won't do any harm anyway, just use a little more water.

 

[William_H]

Battery charge voltage

If you are concerned about charge voltage and are willing to risk slower recharge (and you can't find the internal switch) then voltage can be reduced by .7 volts by fitting a series diode in the positive line.
This should be a silicon diode rated at more current than the charger. ie 20 amp diode. It will get a bit hot so mount it on some Aluminium plate or heat sink. A schotky diode would drop the voltage by about .3v if you can find one of high enough current rating. You might want to put it in a box with bypass switch or even fit a timer so the batteries get full voltage for a limited time. Or remember to switch back to diode in. The float voltage will be a lot lower also which probably is not a problem unless you are using a bit of current on services. Just a thought perhaps better than buying a new charger. good luck olewill