Charging one battery using two Aldi / Didl smart chargers simultaneously

[CAPTAIN FANTASTIC]

What is your experience charging a 12 volt car type battery using two chargers simultaneously. The chargers are purchased from Lidl / Aldi; these are low cost smart automatic chargers which are good value for the money. I would like to know the effect of charging a typical car type battery using two of these chargers at the same time; would the battery receive charge from each charger or there would be a conflict between the chargers as they are "smart automatic" chargers. Have you tried?, what is your experience and thoughts?

 

[Sea Change]

Interesting question. Haven't tried it myself and I expect the result will depend on the settings on the chargers, and state of charge of the battery.
You absolutely can charge a battery from more than one source- e.g. solar and alternator together. So in principle it may work.

 

[Refueler]

This actually was a question I had but for slightly different setup.

My MoBo has two batts of about 90 A/hr each ... I run the boat with both ON and this parallels the two - they are not split as in one for Engine - other for Domestics ... they both feed same ... You can just decide one or both.

Because the main battery switches are buried deep in the transom and need to literally lay on stomach to get to them ... I usually leave both ON when boat is moored.
I have two LiDl chargers as you describe ... each one clipped to a battery.
This means that actually both batts are paralleled - effectively a single 180 A/hr ... the chargers don't seem to care ... each charges its battery as if its separate ...

In your case - I cannot see the point of two chargers - maybe you are trying to get a higher rate ? I don't think this will happen .. they will likely both see a high voltage based on other charger and reduce amps accordingly ??

I think try one on its own - see if that meets your needs ... keep the other for car etc ??

 

[CAPTAIN FANTASTIC]

Thanks for the replies. The aim is to speed up the charging by using two chargers, doubling the charge rate. It is difficult to tell whether the battery is charging faster or not.

 

[Stemar]

If you can separate your domestic and starter batteries, no problem, obviously, you can charge both at the same time, each on their own charger. Otherwise, I think Refueler is right. I fear the only solution to faster charging is a higher power charger.

 

[Alex_Blackwood]

Thanks for the replies. The aim is to speed up the charging by using two chargers, doubling the charge rate. It is difficult to tell whether the battery is charging faster or not.

Suspect that the chargers will "Fight" each other as being "Smart" they will each see the output of the other. No??

 

[KompetentKrew]

People charge with solar + shore power or solar + Sterling alternator regulator all the time with no problems.

I have a notion about two identical units being more likely to get confused because they have identical units for detecting state of charge (and dictating charging stage) but I have no idea whether or not this is rational.

It is difficult to tell whether the battery is charging faster or not.

Would be easy with a SmartShunt.

 

[rogerthebodger]

Suspect that the chargers will "Fight" each other as being "Smart" they will each see the output of the other. No??

I have done this with a "smart" charger. The chargers di not fight each other but will shut off in sequence depending on the exact switch off setting until the battery has reached both settings both will turn off.

I also have also duplicate controllers on my solar panels, and it works in the same way when 2 or more controllers feed a Single battery bank

 

[noelex]

Two smart chargers will not cause any damage and will charge the battery satisfactorily.

The charge rate may not be as high as one smart charger of double the capacity, and in some rarer cases, it may not be much higher than a smart single charger. This is because many smart car battery chargers incorporate a reasonably aggressive tail current setting as the primary means of terminating the absorption cycle. Marine solar MPPT controllers and alternator regulators either have less aggressive tail current settings or, in many cases, no tail current termination at all.

Tail current termination works well when there is no power draw and when the size of the battery bank is known to the charger manufacturer. This does not apply to most marine systems, hence the charge algorithm is different.

 

[Sandy]

People charge with solar + shore power or solar + Sterling alternator regulator all the time with no problems.

I have a notion about two identical units being more likely to get confused because they have identical units for detecting state of charge (and dictating charging stage) but I have no idea whether or not this is rational.


Would be easy with a SmartShunt.

If I am charging with solar and shore power the solar says - hey the shore power is taking the strain and has a rest.

 

[Refueler]

I read replies and I think what is missing from most :

The Lidl Smart Charger works by gauging the resistance against the chargers charge to the battery. This is mainly based on Voltage of battery vs the Chargers Voltage.

The Lidl chargers have no user adjustable settings - only fixed mode buttons. So putting two together will have identical outputs (subject to them being budget chargers of course) ... this means that both will be putting out higher voltage than the battery - but each charger will see the 'other' chargers voltage ... so charge rate will be reduced as it thinks battery is at high state.

I suggest that take away one charger and let remaining one do its job properly.

 

[Refueler]

People charge with solar + shore power or solar + Sterling alternator regulator all the time with no problems.

I have a notion about two identical units being more likely to get confused because they have identical units for detecting state of charge (and dictating charging stage) but I have no idea whether or not this is rational.


Would be easy with a SmartShunt.

My Solar controller shows high voltage state and very low amp rate when other charge sources are working .. it does not shut off to zero ... but basically believes it has nothing to do other than maintenance trickle charge.

 

[noelex]

My Solar controller shows high voltage state and very low amp rate when other charge sources are working .. it does not shut off to zero ... but basically believes it has nothing to do other than maintenance trickle charge.

If the battery voltage has reached the absorption voltage, the battery is being charged at the highest safe value. Chargers should throttle back at this stage to avoid damaging the battery. This does not indicate any problem or conflict. The limitation is governed by the battery, not the charge sources.

 

[Refueler]

If the battery voltage has reached the absorption voltage, the battery is being charged at the highest safe value. Chargers should throttle back at this stage to avoid damaging the battery. This does not indicate any problem or conflict. The limitation is governed by the battery, not the charge sources.

Think you missed the point - the controller sees a high voltage as if the battery is charged - therefore it drops into its maintenance mode. The controller has no way to know if the high voltage is battery or the other charge sources ... it just reacts to the high voltage.

 

[penberth3]

Suspect that the chargers will "Fight" each other as being "Smart" they will each see the output of the other. No??

That would be my worry. I don't understand smart chargers so I wouldn't try it. Solution is to buy a charger with a higher output if you want faster charging?

 

[noelex]

Think you missed the point - the controller sees a high voltage as if the battery is charged - therefore it drops into its maintenance mode. The controller has no way to know if the high voltage is battery or the other charge sources ... it just reacts to the high voltage.

If the battery voltage is high (presumably at the absorption voltage), one or more of the charge sources should reduce their output to maintain the maximum charging voltage acceptable for the battery. This is not a fault or a conflict; it is necessary to correctly charge the battery.

 

[Refueler]

If the battery voltage is high (presumably at the absorption voltage), one or more of the charge sources should reduce their output to maintain the maximum charging voltage acceptable for the battery. This is not a fault or a conflict; it is necessary to correctly charge the battery.

You still don't see the wood for the trees !!

If you have two chargers connected to one battery .... they will both be feeding charge to that battery ... but the voltage they are feeding at is over 13V and as far as one or both chargers are concerned - is full charge battery .. so what will the chargers do ??

Forget what level the battery is at ... its what each charger sees from other charger ...

 

[noelex]

You still don't see the wood for the trees !!

If you have two chargers connected to one battery .... they will both be feeding charge to that battery ... but the voltage they are feeding at is over 13V and as far as one or both chargers are concerned - is full charge battery .. so what will the chargers do ??

Forget what level the battery is at ... its what each charger sees from other charger ...

No, this is not how smart charging algorithms work.

The battery chargers will raise the battery voltage until the bulk/absorption charge limit is reached (typically 14.6-14.2V). They will not stop at 13V. 13V under charge is not a fully charged battery.

Having reached the absorption voltage, they will hold the battery at the absorption time (typically 1 to 2 hours) before dropping down to the float voltage (typically 13.8-13.6V). The exception for car battery chargers is if the "tail current settings" are reached (typically the absorption voltage with a current output of less than 1A). If these limits are reached, the charger will reduce charging until the float voltage is reached.

The above is only a quick summary; there are some variations, but when the output of one charger is reduced when a second charger is connected, this is usually simply because the battery is receiving the maximum safe charging rate.

 

[billskip]

No, this is not how smart charging algorithms work.

The battery chargers will raise the battery voltage until the bulk/absorption charge limit is reached (typically 14.6-14.2V). They will not stop at 13V. 13V under charge is not a fully charged battery.

Having reached the absorption voltage, they will hold the battery at the absorption time (typically 1 to 2 hours) before dropping down to the float voltage (typically 13.8-13.6V). The exception for car battery chargers is if the "tail current settings" are reached (typically the absorption voltage with a current output of less than 1A). If these limits are reached, the charger will reduce charging until the float voltage is reached.

The above is only a quick summary; there are some variations, but when the output of one charger is reduced when a second charger is connected, this is usually simply because the battery is receiving the maximum safe charging rate.

Ok a question, (or two)
If you put the smart charger on the battery terminals that where it gets its information correct?
If that battery allready has a charger connected wll that information be the same?

 

[noelex]

Ok a question, (or two)
If you put the smart charger on the battery terminals that where it gets its information correct?
If that battery allready has a charger connected wll that information be the same?

Battery chargers do not typically attempt to determine the SOC of a battery before commencing charging. They determine the SOC by the voltage (and sometimes the current) behaviour as they charge. They will attempt to maintain the bulk/ absorption voltage for the absorption time or until tail current values are reached. At this stage, they assume the battery is at 100% SOC and they drop to float voltage. The start voltage does not effect the charge profile.

There are some exceptions such as the Victron MPPT controllers, but even here, the start battery voltage simply modifies the absorption time, not the voltage set points, so the effect is small.