Mobitronic 25amp battery charger

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zingaro

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Just been down to my mates boat with him and noticed that the 12V system was not working,the boat has been stored on hard standing for the winter and he left the battery's on board and left the Mobitronic battery charger on all the time as it is supposed to trickle charge the battery's once they are fully charged up. We looked at the battery charger and noticed that there are two positive supply's one going to the engine battery and the other going to the leisure battery's, and one negative supply.The battery's are totally flat when we tested them, the charger power light is on so it is getting AC power so we put a multi meter on one of the positive output cables from the charger and the other to the negative side and it gave a reading of 2.3V,the other one when tried gave us 0.6v, we were expecting to see over 12 volts if it was working properly as I would have thought it would try and put full charge into the battery's with them been flat, so we presumed that the battery charger is knackered that was until I spoke to someone in the marina who said that if the battery's are knackered this can stop your charger from charging to full capacity,now we don't know where to go from here,can anyone cast any light what we should try next, as I would hate for him to buy a battery charger when the one fitted to the boat is over £200 if it turns out to be the battery's that are gone and I presume they will cost a few pounds looking at the size of them.
 
zingaro said:
Just been down to my mates boat with him and noticed that the 12V system was not working,the boat has been stored on hard standing for the winter and he left the battery's on board and left the Mobitronic battery charger on all the time as it is supposed to trickle charge the battery's once they are fully charged up. We looked at the battery charger and noticed that there are two positive supply's one going to the engine battery and the other going to the leisure battery's, and one negative supply.The battery's are totally flat when we tested them, the charger power light is on so it is getting AC power so we put a multi meter on one of the positive output cables from the charger and the other to the negative side and it gave a reading of 2.3V,the other one when tried gave us 0.6v, we were expecting to see over 12 volts if it was working properly as I would have thought it would try and put full charge into the battery's with them been flat, so we presumed that the battery charger is knackered that was until I spoke to someone in the marina who said that if the battery's are knackered this can stop your charger from charging to full capacity,now we don't know where to go from here,can anyone cast any light what we should try next, as I would hate for him to buy a battery charger when the one fitted to the boat is over £200 if it turns out to be the battery's that are gone and I presume they will cost a few pounds looking at the size of them.
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Was the charger working (charging) OK when your mate left the boat for the winter i.e. was there a circuit to each battery (negative as well as positive) and more than 13V on the voltmeter? Some boats e.g. Bavarias, have the battery switch in the negative.

How long has the boat been left with the charger running unattended?

Did you check that there was still water in the batteries? They could have boiled dry if the charger was over charging (for weeks/months?).

Did you disconnect the battery charger from the batteries and see what open circuit voltage the charger gave?

I think we need a bit more info before a full diagnosis. :)
 
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Playtime said:
Was the charger working (charging) OK when your mate left the boat for the winter i.e. was there a circuit to each battery (negative as well as positive) and more than 13V on the voltmeter? Some boats e.g. Bavarias, have the battery switch in the negative.

How long has the boat been left with the charger running unattended?

Did you check that there was still water in the batteries? They could have boiled dry if the charger was over charging (for weeks/months?).

Did you disconnect the battery charger from the batteries and see what open circuit voltage the charger gave?

I think we need a bit more info before a full diagnosis. :)
Click to expand...

Everything seemed ok and worked when it was stored in December,never tested the voltage back then as we did not have a problem, all lights worked as well as the other 12v systems and it had been left on shore power only for the last few weeks before having it taken out of the water,the battery charger has been left on since them,not checked the water in the battery's will check when we next go down,we never disconnected the battery's from the charger would this give a higher reading if we did,is that what you have to do to check the charger is giving out the correct Voltage? Hope this helps in your diagnosis
 
zingaro said:
Everything seemed ok and worked when it was stored in December,never tested the voltage back then as we did not have a problem, all lights worked as well as the other 12v systems and it had been left on shore power only for the last few weeks before having it taken out of the water,the battery charger has been left on since them,not checked the water in the battery's will check when we next go down,we never disconnected the battery's from the charger would this give a higher reading if we did,is that what you have to do to check the charger is giving out the correct Voltage? Hope this helps in your diagnosis
Click to expand...

If you disconnect the charger from the batteries you will get some indication whether the charger is giving its correct output voltage. I would expect at least 14V on open circuit, possibly more depending on its design.

Regarding water in the batteries - obviously the water should cover the plates, assuming they are 'wet' batteries (not maintenance free) and you can see the water level when you remove the cap on each cell. If there is no water it indicates that the charger has been overcharging and 'boiled' them dry. This would explain the very low voltage readings you are now getting. You should immediately fill them (to the correct level) with distilled (or de-ionised) water and then charge them fully. Check the voltage from the charger before you leave them on charge. It should be 12V or higher but no higher than 14.5V. Give them 36 hours or so, disconnect the charger for an hour and then take a voltage reading. It should be 12.8V approx. if the batteries are not completed wrecked. You will then need to do some sort of load test to see if the batteries are holding their charge.

If you can report back when you've done the above, maybe we can help a bit more (with load test suggestions etc.).

Good luck.
 
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Any battery that has dropped so low is on the way out. They may appear to recharge, but I fear the plates may be damaged.
As for the charger, see if it charges the car battery for a minute or two ( you drove there didn't you?) It should read 13-ish volts as it comes out of the car, and 14.5 ish if the charger is working.
Again, it may appear to be working but something is obviously wrong with the result vis -a -vis the boat batteries
I would like to see an ammeter in circuit for the tests as one of the batteries could have shorted and caused an internal fault that went across to the other - all conjecture of course, as we need more info.
 
Two things to do then.

1] Get the charger onto at least 1 known good battery that has been discharged slightly. Monitor it, current and volts to see if it reacharges that. Try both outputs. Compare what you observe with the spec for the charger.

Any fuses on its outputs

2] Get the two batteries onto a good charger and see if they can be rescued. Then get them tested properly if they seem OK. .... Don't hold your breath.
 
zingaro said:
Just been down to my mates boat with him and noticed that the 12V system was not working,the boat has been stored on hard standing for the winter and he left the battery's on board and left the Mobitronic battery charger on all the time as it is supposed to trickle charge the battery's once they are fully charged up. We looked at the battery charger and noticed that there are two positive supply's one going to the engine battery and the other going to the leisure battery's, and one negative supply.The battery's are totally flat when we tested them, the charger power light is on so it is getting AC power so we put a multi meter on one of the positive output cables from the charger and the other to the negative side and it gave a reading of 2.3V,the other one when tried gave us 0.6v, we were expecting to see over 12 volts if it was working properly as I would have thought it would try and put full charge into the battery's with them been flat, so we presumed that the battery charger is knackered that was until I spoke to someone in the marina who said that if the battery's are knackered this can stop your charger from charging to full capacity,now we don't know where to go from here,can anyone cast any light what we should try next, as I would hate for him to buy a battery charger when the one fitted to the boat is over £200 if it turns out to be the battery's that are gone and I presume they will cost a few pounds looking at the size of them.
Click to expand...
On my old 351 bene the charger was a smart one, when connected to the mains the light would eventually start to flicker and then it would usually all settle down and 14.4 volts would come out of it to start the cycle. The prob arises if you try to measure the output of these smart chargers without a battery connected. It doesnt see a battery so it doesnt put out! Best to take a battery with you, disconnect the charger from both banks, measure the voltage on the battery, connect the charger and see if the voltage rises. That will tell you it is putting out or not. For what its worth I suspect that you have boiled the batteries dry, the charger cant see a battery now, so has stopped charging!
St
PS iof the batteries are dry then you can get him to buy new batteries anyway!
 
skipper_stu said:
. . . . The prob arises if you try to measure the output of these smart chargers without a battery connected. It doesnt see a battery so it doesnt put out! Best to take a battery with you, disconnect the charger from both banks, measure the voltage on the battery, connect the charger and see if the voltage rises. That will tell you it is putting out or not.
Click to expand...

FWIW I have just checked my Mastervolt Smartcharger on no load (i.e. battery disconnected) and it puts out a healthy 14.8V. I suspect most chargers do something similar.
 
I suspect most chargers do something similar.
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I think you will find some do some don't.
In the absence of detailed info on the way in which the charger in question works Stu's advice to connect it to a battery is sound advice.

I'd already said to test it on known good battery earlier in the discussion for that very reason!
 
Thanks everyone,I have been down to his boat with him again today,we checked the cells to see if the water was above the plates but could not see any, so we bought two gallon of distilled water,guess what, we only managed to top up 3 of the 4 battery's up with that amount of water. we are going to buy some more,we have removed 3 x110amp leisure battery's and are putting them one at a time on a 2 amp charger for a few hours then we will increase it to 12 volts,and the engine starter battery which looks at least twice the size of the leisure battery's seems to be now excepting a charge from the boat charger and was showing 14.6volts when tested with the charger switched on.We will fully charge them all then I will see if I can borrow my mates battery tester to see if they hold the charge when put under load. Fingers crossed that they plates have not warped and killed the battery's.
 
VicS said:
I think you will find some do some don't.
Click to expand...

Some specialist chargers (high efficiency constant current NiCad chargers for instance) do battery sensing and will shut off the output if there is no load. I have yet to hear of a wet cell lead acid charger that doesn't 'put out' some voltage on no load. However, maybe someone will correct me - from actual observation, please, not speculation :D :D

That said, the problem here appears to be that the charger has been putting out rather too much charge.

Zingaro I hope you manage to resurrect the batteries now you have given them a good drink. You may be lucky :)
 
Playtime said:
Some specialist chargers (high efficiency constant current NiCad chargers for instance) do battery sensing and will shut off the output if there is no load. I have yet to hear of a wet cell lead acid charger that doesn't 'put out' some voltage on no load. However, maybe someone will correct me - from actual observation, please, not speculation :D :D

That said, the problem here appears to be that the charger has been putting out rather too much charge.

Zingaro I hope you manage to resurrect the batteries now you have given them a good drink. You may be lucky :)
Click to expand...
OK
read my post again!
First hand knowledge, did it myself, spoke to the manufacturer, they said the same thing.
Stu
PS
If you carry on I will dub you THOMAS!
 
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