This is not really a huge issue as the quiescent draw on decent charge controllers is low, typically 10 - 20mA, so it would take a looooong time to hit the LVD on a 105Ah battery. However, there is also no reason not to leave the solar panels in the system. As long as the panel voltage and the power supply voltage are close, you don't even need diodes.
solar charge controller as a dc-dc charger?
- Thread starter trae
- Start date
This is not really a huge issue as the quiescent draw on decent charge controllers is low, typically 10 - 20mA, so it would take a looooong time to hit the LVD on a 105Ah battery. However, there is also no reason not to leave the solar panels in the system. As long as the panel voltage and the power supply voltage are close, you don't even need diodes.
dreadlocks
Well-known member
With a 0.025A load (25mA) You'll lose ~20AH a month, just enough so that when you park it in October it's gonna be deeply discharged come April when you check on it again.. assuming its Lithium, when it comes to lead chemistry, storing it at anything but 100% SOC is bad for it, so its gonna be causing issues within a month and be below 50% SOC in less than 3 months.
LFP dont need a maintenance charge tho so there is little reason to leave it on a charger unattended.
LFP dont need a maintenance charge tho so there is little reason to leave it on a charger unattended.
Just to clarify the wording above
It is only lead that needs to sit topped up with a Float charge at 100% SoC for good longevity.
LFP should only be filled just before you need to start cycling, storage is best at a **low** SoC%
so long as you are sure not to let it drop down near 3.0Vpc
It is only lead that needs to sit topped up with a Float charge at 100% SoC for good longevity.
LFP should only be filled just before you need to start cycling, storage is best at a **low** SoC%
so long as you are sure not to let it drop down near 3.0Vpc
Just FYI in general
some PSUs have proper current limiting, so no problem if the SC / DCDC converter doesn't
But true if the former doesn't, the latter must
or at least something in the chain must.
I've used an ACR with that feature to allow charging from any source without having to worry.
Obviously once you start spending serious money on the SC you're better off with a proper DCDC charger e.g. Sterling or Kisae.
Other than the above OCP concern, and adjustability of the charging profile,
there is no advantage to using MPPT technology per se in this scenario.
For example, Bogart's BM has spectacular charge control options controlling slave SCs
which more than compensates for the fact that it's old school PWM tech.
But I dunno if that will accept inputs other than panels.
some PSUs have proper current limiting, so no problem if the SC / DCDC converter doesn't
But true if the former doesn't, the latter must
or at least something in the chain must.
I've used an ACR with that feature to allow charging from any source without having to worry.
Obviously once you start spending serious money on the SC you're better off with a proper DCDC charger e.g. Sterling or Kisae.
Other than the above OCP concern, and adjustability of the charging profile,
there is no advantage to using MPPT technology per se in this scenario.
For example, Bogart's BM has spectacular charge control options controlling slave SCs
which more than compensates for the fact that it's old school PWM tech.
But I dunno if that will accept inputs other than panels.
The big advantage is that he (and I) already have high quality fully configurable MPPT charge controllers that are configured for our batteries. With the addition of a $30 AC-DC power supply you have a high quality fully configurable shore power charger. For another $30 for a 12 - 24V boost converter, you can also have a high quality fully configurable DC-DC charger to charge off the alternator.
dreadlocks
Well-known member
If your using the SC for both Solar and Shore charging, there is money to be saved.. Say I already got my $320 50A VictronSmart Solar, I got a nice high end medical grade 750W 48v DC Power Supply, with PFC and Global Voltage Inputs for a whopping $60 and now I got 50A Fully Programmable, Remote Voltage/Temp Sensing (thanks to BMV) shore charger.. I'd like to know where I can buy a 50A Shore Charger with such features for anything less than a small fortune.
dreadlocks
Well-known member
Here's how I'm doing it:
First of all Solar panels and Shore Supply are isolated by two diodes so they can be wired up together at the same time:
This is the power supply I'm feeding it:
And here's the charge profile of my Lithium battery through it, holding max amps the whole way..
First of all Solar panels and Shore Supply are isolated by two diodes so they can be wired up together at the same time:
This is the power supply I'm feeding it:
And here's the charge profile of my Lithium battery through it, holding max amps the whole way..
dreadlocks
Well-known member
I suppose I do, the whole whopping 0.5v of either my 60v panel or 48v power supply at full rated load.. which seems to have negligible impact since both are capable of tapping out my solar charger at max output.. its not like my Solar Panels have 4 of these things built into it, oah wait.. it does!
Since its on the input side, it has no impact whatsoever on the charge voltage.
Yes, if you already have the expensive high-amp and full featured solar controller
and know for sure it's happy to accept "dumb" input from PSU / DC converter instead of panels
that really starts to make sense, especially since the solar "hub" handles the one scenario where energy efficiencies really matter.
Even better when a BM or BMS can remotely shut off the charging, or at least isolate the LFP from it, so hat bank doesn't get Floated, once voltage has reached your gentler defined "100% Full". No need to measure trailing amps a simple HVC is sufficient.
Some controllers also have load output terminals with bank protection LVC that can be programmed with a higher voltage cutoff for less essential circuits.
Some "boost" controllers on the market can charge 48+V banks from lower voltages too,
maybe a way forward for harnessing alt output, another source where efficiency losses are NBD.
and know for sure it's happy to accept "dumb" input from PSU / DC converter instead of panels
that really starts to make sense, especially since the solar "hub" handles the one scenario where energy efficiencies really matter.
Even better when a BM or BMS can remotely shut off the charging, or at least isolate the LFP from it, so hat bank doesn't get Floated, once voltage has reached your gentler defined "100% Full". No need to measure trailing amps a simple HVC is sufficient.
Some controllers also have load output terminals with bank protection LVC that can be programmed with a higher voltage cutoff for less essential circuits.
Some "boost" controllers on the market can charge 48+V banks from lower voltages too,
maybe a way forward for harnessing alt output, another source where efficiency losses are NBD.
Has it been confirmed that these are fine with non-panel inputs?
dreadlocks
Well-known member
electrons are electrons, its fine.. I'm not sure how a static power supply could could cause a SC to not be fine, if it can take a variable device like a solar panel, why wont it take a static one like a psu.
It does foobar my solar generation stats entirely.. oh well.
It does foobar my solar generation stats entirely.. oh well.
dreadlocks
Well-known member
I've been using it as a shore charger for nearly a year now.. its not gone up in a cloud of smoke if thats what your asking.. I'm also far from the only one doing this w/a Victron Smart Solar, I found dozens of other people doing same thing I am with a lil bit of google-****... IIRC there's a thread on victron's forum w/staff members involved.