shore power battery charger (ac to dc 100amp)

[bluecolumbia]

hello

i've got a newish installation on my sailboat, 12v, 380ah of lipo, 680w of solar, charging from 170amp alternator w/ external regulator), all works great. but i'm currently limited to a 20amp charger at the dock (just using the charger that came with the batteries), so if i come in to the slip with low batteries they charge very slowly on shore power. (especially since there is a constant load of 10-20 amps running). so i'd like to add a 100amp ac-dc charger for shore power.

i already have all of the inverter power i need, so i would not benefit from getting a charger/inverter combined unit.

i see that there is an extreme range of prices for ac/dc chargers, and i don't understand why. i'm looking at a <$200 charger intended for an rv, which appears to have the same features that the more expensive marine chargers have. equivalent marine chargers are 10x to 20x as much. (yes i understand the marine markup, just trying to understand if i'm missing something else here). all of the systems i'm looking at have a mode for lipo batteries.

2nd question - what i really want is a device that will charge the batteries, and isolate the batteries, and provide 12v power for the house while connected to shore power (and then connect the batteries to load when shower power is removed). it seems like the large superyacht/industrial systems do this, but it doesn't appear that even the more expensive marine systems do this at the size i need. do any of you isolate your batteries while on shore power (so that they are not running loads at the dock and constantly cycling)? i could accomplish this with some switches, but it seems like this would be a logical feature for a battery charger.

thank you for any advice
...bluecolumbia

 

[sunshine_eggo]

Doubt you'll get under $200, but you can get close.

I have a couple of these:

Powermax PM3-100LK

You can set the absorption voltage with a pot, or you can operate it as a constant voltage power supply set with the pot.

Why isolate the batteries? And how do you propose to isolate the batteries from the load while providing "12V" to the loads with the charger?

These chargers work on the float principle - fully charge and then hold at float powering loads and keeping the battery charged. With LFP it will be a little different. It might make sense to just run the charger at 13.8V constant.

 

[Consumerbot3418]

I have a couple of these:

Powermax PM3-100LK

You can set the absorption voltage with a pot, or you can operate it as a constant voltage power supply set with the pot.

I've been looking for a way to supplement the paltry 80a x 2 provided by my 12V split phase Multi setup. I've got a dozen parallel 12V LFP 100ah batteries, and they could handle up to 600a. Sometimes, my AC-coupled system is curtailed despite the battery being depleted, because I don't have a way to convert the excess power from AC to DC. So I've been looking at options like this. I'd really like to have something whose output could be remotely controlled, instead of simply being switched on and off. Best idea so far is several of these RV "converters" on smart sockets. Are you doing something similar?

@bluecolumbia, I think your idea is to minimize wear/tear via cycling. But if you have LFP/LiFePo4 (not "lipo" as per OP), I think I've heard @Will Prowse say that calendar aging will kill this chemistry quicker than cycling. In my case, I've decided not to worry about cycles, but I also don't have any 12V loads I could power directly--but my previous experience with an RV is that the converter powers loads, and charges the battery with any additional remaining power capacity. Once it's charged, it maintains float voltage, meaning that loads are powered by the converter up to its power capacity, and the battery isn't depleted nor experience cycling while on shore power, unless you draw a larger load than the converter can supply. If you decide to get a product that isn't intended for marine applications, you might want to keep a spare on hand, in a sealed bag--I understand that marine environments accelerate corrosion, so those 10-20x inflated prices may be (at least partially) justified, if the electronics are ruggedized, protected from corrosion (and engineered to handle the resulting heat dissipation concerns), etc.

 

[l00semarble]

I would get a marine grade charger that is fully programmable which is very different than "has a lithium setting." You need to be able to program the exact parameters that are required by the battery manufacturer. There is no single setting that is correct for all lithium batteries.

We are quite fond of the new Victron Phoenix Smart IP43 Charger which can be programmed via Victron Connect App via Bluetooth. Quite slick. The larger one is 50a so 2.5x the size of your 20a charger. You would benefit from even larger charger but usually if plugging into a dock you are going to be there a while so maybe 50a will do. Theoretically you could install two of them.

If you need 100a at 12v that is a pretty large and less common charger. It may be easier and cheaper to upgrade your inverter to an inverter/charger for this kind of higher output. Then you only need one set of large DC cables. This is what I would do if it were my boat.

And like the others said there is not reason to try to disconnect your batteries and have the charger support your loads because this is essentially what happens when the batteries are fully charged and the charger backs down to float voltage. At that time it will maintain the specified voltage and it will add/subtract currrent as necessary to support the loads while the battery will net close to zero input/output amps. This assumes a good quality marine charger meant for this kind of service. Some non-marine chargers are not smart enough to work this way and we see them go into a whole new charge cycle each time a significant load is placed on the DC system.

 

[bluecolumbia]

hi there thank you all for your replies.
so i went ahead and added a 12v 1000w power supply...

https://www.amazon.com/gp/product/B0BQD6SR4Z/ref=ppx_yo_dt_b_asin_title_o07_s00?ie=UTF8&psc=1

i have a perko a/b/both switch in my panel that i have not been using (because i converted my house to lithium and my engine battery is still lead acid - so the starter and engine battery were removed from the a/b/both switch and connected directly via another cutoff switch.

i now have my lithium house batteries on the [a] side of the switch and my new power supply on the (b) side of the switch. the chargers are connected to the battery, so they continue to charge the battery when the switch is set to (b). when the switch is set to [a] the house is powered by the batteries, when the switch is set to (b) the house is powered by the power supply. the transition through [both] works fine, with the loads (including inverters) switching from battery to power supply and back with no interruption in service.

i may still increase the size of my shore battery charger - though even with my existing small charger, now that 100% of the charge is going to the batteries, i can still charge to 100% in 24 hours, which is pretty good.

i'm not all that concerned about battery cycles... but i do want to be able to put 100% of the available charge into the batteries (instead of charging being slowed down by loads). i also like the idea of being able to work on my batteries/electrical system while keeping the house powered up via the power supply. very convenient. now that i see how well this seems to be working, i will probably replace the power supply with something more robust (since it will be running constantly when i'm on shore power).

thank you all again for your helpful advice - wondering what you think of my modifications.

...bluecolumbia

 

[l00semarble]

I would do a little research because I suspect this Chinesium power supply does not isolate AC Neutral and DC negative due to the use of a cheap single winding transformer. This is a BIG no no on boats as it can be a cause of major stray current which can both cause corrosion, will trip shore power ELCIs and can kill a swimmer near the boat.

I would be hesitant to not use this device until isolation is verified. The potential liability is tremendous.

 

[Pappion]

I would do a little research because I suspect this Chinesium power supply does not isolate AC Neutral and DC negative due to the use of a cheap single winding transformer. This is a BIG no no on boats as it can be a cause of major stray current which can both cause corrosion, will trip shore power ELCIs and can kill a swimmer near the boat.

I would be hesitant to not use this device until isolation is verified. The potential liability is tremendous.

There is a reason RVs are not plugged into a GFCI. They would trip it and people would be clipping the ground off the plug. It's considered a trunk line. It has to tolerate EMI filters with capacitors to Ground.

 

[sunshine_eggo]

I've been looking for a way to supplement the paltry 80a x 2 provided by my 12V split phase Multi setup. I've got a dozen parallel 12V LFP 100ah batteries, and they could handle up to 600a. Sometimes, my AC-coupled system is curtailed despite the battery being depleted, because I don't have a way to convert the excess power from AC to DC. So I've been looking at options like this. I'd really like to have something whose output could be remotely controlled, instead of simply being switched on and off. Best idea so far is several of these RV "converters" on smart sockets. Are you doing something similar?

I have a ~5 year old PM4-100LK (essentially same as PM3-100LK) on a WIFI remote plug for remote on/off.

 

[bluecolumbia]

I would do a little research because I suspect this Chinesium power supply does not isolate AC Neutral and DC negative due to the use of a cheap single winding transformer. This is a BIG no no on boats as it can be a cause of major stray current which can both cause corrosion, will trip shore power ELCIs and can kill a swimmer near the boat.

I would be hesitant to not use this device until isolation is verified. The potential liability is tremendous.

there is not continuity between ac neutral and dc negative.
the unit is plugged into a gfci outlet and has not tripped it.
the (translated) documentation says that it has 'leakage protection.'
the reviews for the manufacturer indicate good support.

i was considering getting a more rugged power supply for long term use, this particular unit was more for experimentation (since it is so inexpensive). however, i don't really see anything wrong with its operation, it runs cool.

how would you 'verify isolation?'

...bluecolumbia

 

[l00semarble]

The fact that it doesn't trip a GFCI is good.

 

[Pappion]

The fact that it doesn't trip a GFCI is good.

Unless the ground was not connected during the test. Try connecting case to GFCI gnd. Try connecting DC- to GFCI gnd.

 

[bluecolumbia]

Unless the ground was not connected during the test. Try connecting case to GFCI gnd. Try connecting DC- to GFCI gnd.

what should i be looking for when i try these things... current? or tripping the gfci?

also... the power supply has a ground on the ac side, which is plugged in properly to the gfci. there is no ground wire on the dc side... should the case and/or the dc- be connected to ground as part of the installation? or are you just suggesting this for testing?

thank you...
...bluecolumbia