question

hakanlarsson65 avatar image
hakanlarsson65 asked

Will the trickle charge disable when main charge is disabled?

I plan to control my multiplus 12/3000 charging via a BMV 712. So charging of my Lithium stops when reaching wanted voltage. Will this chat down the trickle charging to? I cannot find any information on this.

Multiplus-IIbattery chargingBMV Battery Monitor
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6 Answers
pwfarnell avatar image
pwfarnell answered ·

On my boat i have a 12V multiplus and a solar charger connected to the large house bank of AGM batteries and the trickle charger is connected to the start and bow thruster batteries. If the Multiplus is off or set to inverter only without any shore power, the engine start battery still gets charged by the trickle charger. My belief is the trickle charger takes power from the 12V DC connection regardless of what the main charger is doing.

i like this because I can return to the marina and not worry about having used the bow thruster, I can leave the solar panels to recharge those along with the house bank and not connect shore power.

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Stefanie avatar image
Stefanie answered ·

Hi @hakanlarsson65@gmail.com,

yes, trickle charge will be disabled when there is no AC IN.

Edit: I just made the ultimative test and must revert my answer above. Without AC IN I still can measure 13.35V between trickle charger output positive and battery minus on the MultiPlus. That suggests that trickle charging is still on.

I was under the assumption that as soon as the main charger goes off (no shore power or Inverter only mode), trickle charge will stop also because afaik the trickle charger follows the main charger. That's obviously not the case. Sorry for the confusion.

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Hi @Stefanie

Thanks for your reply. I meant if I control the main charge via the BMV 712 telling the Multiplus to discontinu charging. Still with AC IN. Will this control also disconnect the tricle charging?

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@hakanlarsson65@gmail.com,


please see my edit in the post above. I had to try it out because I've never used the trickle charger.

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kevgermany avatar image
kevgermany answered ·

@hakanlarsson65@gmail.com

Looks a bit confusing to me, if I understand it you want to use the BMV 712 to stop the Multiplus from charging your lithium, but without disconnecting the AC in.

And then the question is does this stop the trickle charge. Is this correct?

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hakanlarsson65 avatar image
hakanlarsson65 answered ·

Yes, that is correct. It’s not a big deal if lead is not continuing charging when Lithium is fully charged, but in the perfect world….

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Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

As far as I know the trickle charge is just a diode or transistor.

It is always on and has the same voltage as the main battery minus 0.3V (voltage drop over the diode/transistor) and as long as the aux battery voltage is lower than that there will be a current flow.

If the main battery is lithium and the aux battery is lead you will "discharge" the lithium battery into the lead battery because the lithium battery has a higher idle voltage.

But I'm not 100% sure because we also never use that feature.

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Sounds more plausible, Matthias.
But can't confirm the voltage drop of like 0.3V. Main battery voltage and aux battery voltage are within 10mV. But doesn't matter really.

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We used that feature just a few times many years ago, so maybe there are some changes.

And we also had the issue that the transistor dies if you connect it to a starter battery that is low and you start the engine because a high current is pulled through it.

Because of that we don't use it anymore and I don't recommend it to our customers.

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luphi avatar image
luphi answered ·

All,

I made the same experience with a MultiPlus 12/2000. Trickle charge seems always to be on, even if the Multi is completely switched off. My plan was to use it to charge the starter battery of a camper van, but don't want to bleed the leisure battery.

Just wondering if one could use the programmable relay directly to switch the trickle charge on only if AC in is connected.


Cheers,

luphi

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