48v charger for 48v LiFePO4 battery - automatically charge?

[SuperD]

Current setup:
I am using a 48v battery (currently a 60Ah Litime 48v golf cart battery) to supply power to the XT60 solar inputs on an Anker Solix F3800 to supplement solar input on the OTHER XT60 port as the location of this setup gets poor solar coverage, especially this time of year. Yes, the Anker F3800 is NOT "DIY", but my overall setup "sort of" is, as you'll see. I do have a single AC circuit (15amp/1800w) to this location that is currently connected to a 10a 48v charger (from Litime) which is then connected to the 60Ah 48v Battery.

My issue:
The battery charges the F3800 with no issues, but the charger continually runs if I leave it alone (so I have it shut off currently), even after the battery is fully charged. Litime support confirms the charger doesn't know when the battery is fully charged, and I should just "manually turn it off".

My question:
I'm looking for an AC charger (10-15amps) that can be left connected to a 48v battery that can go into standby when the battery is full but will then come back on for a charge cycle when the battery has depleted to some point - not really concerned much with WHAT that point specifically is, just that the charger can keep the battery "topped off" over time without manually turning it off and on. Anyone have any suggestions on a 48v battery and charger setup that can meet this need? I thought the current setup I have would do this (as the standard golf-cart setups/chargers will go into standby when a cart is fully charged), but apparently not...

 

[wpns]

Does the golf cart charger turn itself off if you remove the load from the battery?

 

[SuperD]

Does the golf cart charger turn itself off if you remove the load from the battery?

I don't believe so, but I'll test it again.

I had fully drained the battery to calibrate a shunt/monitor, then pulled the XT60 connector from the anker and let the charger run for over 6 hours afterwards, then left it sitting for ~3 hours. The shunt/monitor I have on the battery showed 53.4v and 100% charge at that point. With the battery in this state, I turned the charger back on and it ran for an additional 1.5 hours or so, with the shunt/monitor still showing 100% battery charge, with input of 9.96a and 543w. Voltage climbed to 54.5v. I suspect the battery BMS was in overcharge protection at this point, but the charger continued to run until I manually shut it off.

When I explained the above scenario to Litime support, their response was:
"When the battery has been fully charged, it will still accep the charging from the charger. Therefore we would recommend you disconnect the charger in time when the battery has been fully charged.
If you hook it up with the battery and charger too long after they fully charged, the battery will start the over-charged protection. (It was not good to keep the battery health if your battery always start the over-discharged protection many times).
When the battery has been fully charged, the battery will accept the tail current from the charger. The 9.96A current detected by the shunt which was the charger output current but do not delivery to the battery."

 

[Rossman]

Dakota lithium charger maybe?

 

[SuperD]

UPDATE to my above post. I tried charging again today - no load on battery - battery had not been used in 4-5 days. Before charging start, battery voltage via the shunt/monitor read 100% and 52.8v - forgot to test voltage with multimeter. Battery full voltage (according to the LiTime battery manual is >= 53.32v. Ran charger for approx 1 hour delivering 547w at 10a - voltage read 54.6v via monitor and 55.0v via multimeter at terminals.
Charger never stopped.

 

[SuperD]

Dakota lithium charger maybe?

Reading the description on their website of their 48v 15amp charger at https://dakotalithium.com/product/4...o4-battery-charger-for-lithium-iron-batteries - it states "Simply plug the charger into the Anderson plug, and remove when done" so I don't think it would shut down afterwards either.

 

[Rossman]

Reading the description on their website of their 48v 15amp charger at https://dakotalithium.com/product/4...o4-battery-charger-for-lithium-iron-batteries - it states "Simply plug the charger into the Anderson plug, and remove when done" so I don't think it would shut down afterwards either.

Yeah it's not clear, you could ask them though. The reason I thought it might is because it says it has an LED that goes green when the battery is fully charged...that might just be the thing telling you to unplug tho.

 

[wpns]

UPDATE to my above post. I tried charging again today - no load on battery - battery had not been used in 4-5 days. Before charging start, battery voltage via the shunt/monitor read 100% and 52.8v - forgot to test voltage with multimeter. Battery full voltage (according to the LiTime battery manual is >= 53.32v. Ran charger for approx 1 hour delivering 547w at 10a - voltage read 54.6v via monitor and 55.0v via multimeter at terminals.
Charger never stopped.

No idea if the charger terminates at a particular voltage, or the BMS takes the battery completely offline, or just disables charge and leaves discharge enabled? Igotta say it feels like you are running blind. What do the charger leads read with no battery connected?

 

[wpns]

What voltage should LiFePO4 batteries be charged at? 57.6 volts is recommended for 48v Dakota Lithium (LiFePO4) batteries. This charger charges at 57.6 volts.

That’s 3.6V/cell, probably too high for most LFP batteries. Feels like their batteries BMS will take at least the charge FETs offline when they hit cell overvoltage, but depending on that might be less than ideal.

 

[ocular]

Riden power supplies RD60xx series wiii do this in their battery charging mode set the CV 55V and CC at 15amps and set so when the amps drop to 0.5A the unit will stop the charging and it will tell you how many watts it took to fully charge. It will not switch on at a prest voltage though. This will have to be done manually. You would need at least an RD6018 (60V 18A) This a create unit to have on the workshop bench for many tasks.

 

[chopper]

I recently purchased some DC HOUSE 48 volt (51.2) batteries with chargers and the chargers do cycle on and off batteries are at 54.5v and charger is idle showing 100% charge

 

[MakeMePower]

most lithium chargers go to 3.65 per cell, thats 58.4 of course the charger doesn't shut off below that, as far as I am concerned voltage is more of an indicator then any SOC meter. Every day we read how off SOC meters are. there is no issue with the charger, its going to hold the cells at 100%, if you want it to stop early, then get a dc voltage sensitive relay to cut the connection

 

[wilmeek]

The solution I came up with for my system was to use a Victron BMV-712 smart to monitor the battery as it has a programmable relay with dry contacts that can handle up to 1A at 60vdc. I run my system 12v to this relay to close a 120V 10A relay with a 12V coil. The 120V relay I have wired to an extension cord that I plug into a standard wall outlet. That energizes an off the shelf 15A 12v LFP charger from walmart that is plugged into the other side of the 120V relay.
I have mine programmed so that when battery voltage hit 12.8V, The BMV-712 closes its relay and that energizes the 12v coil of the 120V relay to power the charger. The charger starts on its own. The 12.8V roughly equates to 20% capacity. And the relay in the BMV-712 opens again at 13V or about 40% capacity. This opens the 120V relay. As the 15 amp charger only pulls about 2.5 amps at most, the 10 amp relay can interrupt this easily.
The relay in the BMV-712 smart can be programmed to many different parameters including a calculated capacity or even temperature and several other parameters.
And it has an audible alarm that can be set to many of those same parameters.
And it has Bluetooth so all of the monitoring and programming can be done on your phone.

The only difference you would need is a 120V relay with a 48vdc coil. And I would look for at least 10 amps like I have just for a bit of margin.
something like this

Temco 2X Industrial Ice Cube Plug-in Relay General Purpose 48 VDC 10A Contact 8 Pin (LY2 Format) w/Socket​