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james09 avatar image
james09 asked

Victron battery charger switching to float too soon

Hi - we are currently running a 1kw solar system with your Blue Solar MPPT 100/50 and have a manual generator backup with a BlueSmart IP65 15A charger. We notice that the BlueSmart keeps switching to float when the batteries are not fully charged (sometimes within 15mins when the 12v batteries are at around 11.5v). The same thing happens when we connect multiple chargers to the batteries in a ‘charger-bank’ setup. We are wondering whether the MPPT is confusing the Battery Charger and whether we need to switch it off to get it to work properly?

battery charging
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Mark avatar image
Mark answered ·

Up until the point that either of the 2 individual chargers reach their absorption voltage setpoint (during bulk phase) both chargers will simply charge together at max power.

The absorption voltage for a 12V battery should be somewhere in the range of 14.4V, so neither charger should be fooled into going into float phase prematurely by the other at ~11.5V...

I recommend that you check the absorption voltage set in the Bluesmart IP65 charger as a start. Something seems 'way off' to me.

Generally speaking you normally set the charge voltages in a MPPT about 0.2V higher than an AC charger, so that the MPPT finishes off the charge cycle with 'free' solar power (rather than the MPPT dropping off early and you having to run the generator for another 2 hours). But this can also get a bit complicated when voltage compensation due to temperature is involved.

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JohnC avatar image
JohnC answered ·

Hi James. There may be some 'interaction' of your chargers via the batt V, simply by virtue of their relevant target V settings. Expected.

But not at 11.5V. Is this a typo? Or you have some 'special' needs?

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james09 avatar image
james09 answered ·

Unfortunately it’s not a typo - the batteries were very flat when we hit charge. Do you know if other Victron products such as the solar MPPTs might have the same issue? For example we are worried that if we run a generator with a 30A battery charger the MPPT might interfere and reduce the charge?

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JohnC avatar image JohnC ♦ commented ·

They shouldn't interfere (and likely can't anyway) beyond batt V. To troubleshoot perhaps best to run them separately. Look well at your wiring too, a high resistance connection can foul the best intentions. Sorry I can't help more..

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adev avatar image adev commented ·

My understanding is that if you use two battery charges simultaneously the worst that will happen is one will see the battery as full as the other pushes voltage into it, and so the one may switch to float mode very quickly, but the other should carry on doing its thing as normal.

Mi could be way off the mark though and it probably very much depends on the two chargers in question. I’m not familiar with the two reviews you have mentioned.

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