Battery charger (1 Viewer)

Eggs

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Jan 3, 2018
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*Newbie alert*, I've recently bought an old Mercedes 811 and I'm having trouble with my leisure batteries. I'm pretty sure they are dead, I took them off and charged them for 2 days and got them to 14.4v. Last night they failed drastically, I've disconnected them this morning and they are reading 9.5v, so done for?

My question is: how do I check if my on board zig unit is charging correctly?

Tia.
 
May 7, 2016
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When I had a Zig it never charged anything properly but newer ones might be quite different. If you can check what voltage the Zig is delivering it might be useful.
 
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Jul 5, 2013
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Best to tell us the year of your van and who the converter is. It will be them that fitted the Zig unit not Mercedes

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Eggs

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When I had a Zig it never charged anything properly but newer ones might be quite different. If you can check what voltage the Zig is delivering it might be useful.

How do I test the voltage from the Zig, Is it as simple as taking the charging leads off to check what voltage I'm getting there?
 
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Jan 19, 2014
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How do I test the voltage from the Zig, Is it as simple as taking the charging leads off to check what voltage I'm getting there?
Put a multimeter on the battery terminals when the charger is on. It should show 13+ volts dc.

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May 31, 2015
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Ok, I was hoping not to start pulling it apart until spring...

What charger would you recommend?

I’m afraid I’m not at all qualified to answer that but but I’m sure someone will shortly...(y)

But it definitely looks like your charger is goosed ..
 
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May 7, 2016
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The duff battery may be pulling the voltage down. Suggest you try a second voltage test with the battery disconnected.
 
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Jan 19, 2014
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Check there is a mains supply to your charger with the multimeter set to AC.

If you need a new one, these get good reviews..

Amazon product

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Jan 28, 2008
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any 20 amp intelligent charger will do, if its going to be permanently connected make sure its the type that holds the previous settings ive got an aldi/lidl one which works fine but you have to select the battery type every time
 
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Eggs

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Please don't laugh... I've sussed it, maybe too late to save the batteries?

There is a switch on the Zig unit to swap between towing and EHU. I'd got it set to towing, I've switched over and I have 12.9v at the batteries. Am I living in hope that I haven't 'cooked' them?

The Zig unit is warm/hot, is this normal?
 
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two

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You may be OK. Wait and see. Zig will get warm.
Sometimes bad batteries will kill a charger, so keep an eye on the lot.
I'm not sure if the charger is 'intelligent' so I'd consider upgrading at some stage, especially if buying new batteries.

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May 7, 2016
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My old Zig was far from intelligent, in fact I would say it was remedial but that is probably not a pc way to descibe anything these days. In truth it was not really a battery charger at all, it was just a fixed12v power supply to run things whilst on a hook up. The maximum voltage was only about 13.4v which is not high enough to properly charge a lead acid battery or protect it from damage.

If you value your batteries I would be looking for a device that is designed to stage charge the batteries and provide a stable supply when they are full. Sterling, Victron and Votronic are manufacturers that come to mind as having been recommended quite often on this site.
 
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Jan 19, 2014
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My old Zig was far from intelligent, in fact I would say it was remedial but that is probably not a pc way to descibe anything these days. In truth it was not really a battery charger at all, it was just a fixed12v power supply to run things whilst on a hook up. The maximum voltage was only about 13.4v which is not high enough to properly charge a lead acid battery or protect it from damage.

If you value your batteries I would be looking for a device that is designed to stage charge the batteries and provide a stable supply when they are full. Sterling, Victron and Votronic are manufacturers that come to mind as having been recommended quite often on this site.
Our charger is the same, just a 13.8v fixed power supply fitted by Elddis from new. Rarely use it now I've fitted the Votronic Duo 250 solar regulator. But it's there for emergencies.
 
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May 7, 2016
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Our charger is the same, just a 13.8v fixed power supply fitted by Elddis from new. Rarely use it now I've fitted the Votronic Duo 250 solar regulator. But it's there for emergencies.
For many years some manufacturers installed these power supplies that weren’t designed to reach charging voltages and left the battery manufacturers to take the flak for the short life of leisure batteries.

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Apr 27, 2016
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In the days before smart chargers, they only had fixed voltage. There were basically two choices. 14.4 volts charges the battery completely but cooks it if left on when the battery is charged. 13.8 volts doesn't completely charge the battery but is safe to leave connected indefinitely.

Smart chargers monitor current and voltage continuously. First a high current until the voltage rises to 14.4 volts. Then fix the voltage at 14.4 volts until the current drops to a predetermined low value. Then about 13.8 volts to trickle charge the battery and keep it topped up.

Then there's the motorhome problem. A smart charger can't tell if the current is charging the battery or powering a light, so it can get confused in some circumstances, but a fixed voltage charger just stays fixed.

Nowadays smart chargers are almost univeral, and some people also have a battery charge monitor to check the percentage charge state as the current goes into and out of the battery.

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May 7, 2016
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My Sterling charger has bulk, float and maintenance phases. A truly smart charger designed for boat or motorhome use will manage the phases to make sure that there is no overcharging. A simple 2 stage charger of the type designed for recharging car batteries may not do this because it is not really designed to provide a power supply.

IMHO you need to match the charger to the size of the battery bank and the type of battery. Too little and it may never achieve a full charge and too big it may be pushing in more amps than is good for the battery.

I believe there are a number of cases where chargers have failed because battery banks have been extended and worked the original equipment too hard. I am pretty sure that this was the cause of a failure on a Knaus I once owned. I extended the battery bank to 220ah and a few months later the charger went kaput.
 
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