Is there such a thing as a variable current charger?

[l00semarble]

You question was based on an incorrect premise that a 12V charger uses its rated DC output in shorpower input amps. A 40A charger does not need 40A from shorepower....it needs more like 4A.

Others explained above how the current it needs from shorepower is about 1/10th that of its rated 12v output current. This means that you likely will have absolutely no use for a "variable current charger" unless you have some unusually large battery bank or extremely limited shorepower. Even if you are limited to 15A shorepower or a Honda suitcase generator that could easily power a 100A charger. Unless you are talking about a larger yacht or other special situation most recreational boats don't have chargers that big and most manufacturers don't make chargers larger than 100A for 12V systems.

So we still don't know what the batteries are (chemistry/size?). Or are we just talking in theory rather than a specific application.

Victron inverter/chargers do have a "Input Current Limit" settings which does exactly what you are asking about. You can tell it what current the present shorepower situation will support and it will scale charging appropriately to keep shorepower load within the limit you specify. It goes beyond just scaling charging - it will account for all the other AC loads on the boat and scale charging so that when added to the other loads the total AC load on showerer will be managed within set limit. It does a step further with "Power Assist" where the unit will scale down charing to zero and then "negative" charging which is inverting to actually add AC power to the limited shorepower to support loads when they exceed what shorepower can supply.

They also have some small chargers with Bluetooth that you could easily set for lower current charging if you want.

 

[jdege]

You question was based on an incorrect premise that a 12V charger uses its rated DC output in shorpower input amps.

No, it wasn't.

I have, for example, two 100Ah, 48VDC batteries, with chargers. Each of the chargers draws 12+A at 120VAC. I can run both off a single 30A pedestal, but I can't run much else.

I don't, as of yet, have a shore power connector, inverter/chargers, etc. I'm plugging AC chargers directly into the pedestal. The 12V charger for my 100Ah house battery doesn't draw more than 4A at 120VAC, but I can't run all three chargers at the same time.

There are places where shore power pedestals provide 30A at 120VAC, others that provide 50A of 60A. If you have sizable battery banks, you might well want to be able to take advantage of the additional power, while still being able to throttle back when less is available.

It might not be an issue for your typical diesel auxiliary boat, but for a full-electric setup, it's an issue.

 

[Warpspeed]

Only solution, as I mentioned earlier is to obtain the highest capacity charger that may be useful to you, and modify it in such a way that it can be "throttled back" to suit situations where shore power is limited.

Its all a rather unusual requirement, which is why there is likely nothing mass produced going to be available off the shelf to suit your needs.

 

[Daddy Tanuki]

No, it wasn't.

I have, for example, two 100Ah, 48VDC batteries, with chargers. Each of the chargers draws 12+A at 120VAC. I can run both off a single 30A pedestal, but I can't run much else.

I don't, as of yet, have a store power connector, inverter/chargers, etc. I'm plugging AC chargers directly into the pedestal. The 12V charger for my 100Ah house battery doesn't draw more than 4A at 120VAC, but I can't run all three chargers at the same time.

There are places where shore power pedestals provide 30A at 120VAC, others that provide 50A of 60A. If you have sizable battery banks, you might well want to be able to take advantage of the additional power, while still being able to throttle back when less is available.

It might not be an issue for your typical diesel auxiliary boat, but for a full-electric setup, it's an issue.

if thats the case then by the EG4 chargeverter. you can adjust its output to whatever level you want form minimum to its max. then can run on 100/110/120 or 200/220/240 single/split phase.

I run two fo these on a 3 phase genset one of them receives 208 form 2 poles and the 2nd unit receives 110 from the third pole and neutral. i use the adjustments on the units output and a clamp meter to ensure that all three legs are balanced.

you could do the same, take one unit (or two) put them on at 120 and then dial them down until they are only drawing the power you want to put into the charger. the balance could power other loads as needed.

 

[l00semarble]

Okay at the very least you were confusing and didn't give enough (any) detail to help you. Literally no one refers to the size of a battery charger by the AC input current.

Still my answer remains the same that Victron has features that do exactly what you want.

 

[SomethingAppropriate]

Just get a couple Eg4 18kPVs. You can control the charge rate from the app.