Randall is new to the forum but an experienced electrician

[RandallCothren]

Hi all, My Bride of 35 years and I are full-time RV people for 5 years now. We have a fifth wheel. We are camp hosts sometimes with full hookups. Sometimes we wander around the US. Sometimes we boondock. I have solar on the roof. a Renogy solar 40 amp rover controller and a 3,000-watt inverter. There is a honda 3000 on the dually. In the rig, the generator or the inverter or shore power is hardwired in via two transfer switches.

I want to list my equipment below then ask a question. I am an electrician by trade but I am new to lithium. Please keep replies to very technical. On some forums people will respond as follows: I don’t know much about what you’re saying but my guess would be …. I would really like to avoid those types of responses.



I recently purchased four 3.2v 280ah deep cycle lifepo4 battery cells lithium which I will connect in series. This will create 12.8 volts. I also purchased a 150 amp BMS already and I will hook it up properly.

I have a 2018 RV that came with a 75 amp Progressive Dynamics PD4575K118L charger which is a lead-acid only converter I have determined it does not have a lithium setting.

I contacted Progressive said I should just buy the PD4575LICSV replacement for 350.00. It is a single-stage charger that creates 14.6 volts.

I could buy it but that would not be so thrifty when my converter is brand new.

The core is the same for all these models but the profile is created by a circuit board.

120 volts AC in rectified to 120 volts DC out. Then a high wattage transformer goes from 120 v DC to

14.6 v DC.



I wanted to ask the forum what if I remove the converter and, on a bench, intercept the output wires + and - right when it becomes 14.6 volts DC. I could add a 14.6 voltage regulator in series. Then I apply this directly to the input of the BMS ( at this point, the BMS input, I will also tie in the #10 wire coming to my fifth wheel from the dually 14.5 alternator ) and it will feed the Lithium batteries.



If this is too direct I could intercept the output wires + and - right when it becomes 14.6 volts DC tie them to the alternator wire and use this as an input to a Renogy 30 amp rover on the lithium setting. If the charger can produce 75 amps and I wanted to use a 30 amp Rover would I just need to put a 30 amp breaker in series. The 70 amp rover is as expensive as the 350 gadget I am trying to avoid.

Randall

 

[sunshine_eggo]

I can't locate your converter manual based on the part number you supplied.

One does not need a "Lithium" charger for a Lithium battery. One needs a charger that is compatible with Lithium's requirements and is willing to live with any compromise that may be required.

IMHO, MANY "Lithium" options are actually a poor implementation.

Charge voltage of 14.6V or less and a float voltage of 13.6V or less, and that's it.

You can't feed a solar MPPT with battery voltage. In most cases, the input voltage needs to be 2-5V higher than the battery. They are step-down only.

 

[HRTKD]

^^^ What he said.

I am rarely connected to shore power, but to keep my system "correct" I switched to a converter with a LiFePO4 charge profile.

The ideal situation is to get an inverter/charger that is programmable. That way you can set the exact charge profile you want to match your batteries. But that's an expensive solution.

There are less expensive options than the Progressive Dynamics. I used IOTA Engineering. But, like said above, many of us aren't 100% happy with the (non-programmable) LiFePO4 charge profile that we get.

 

[corn18]

What I will say is do not buy the Progressive Dynamics replacement for $350. Outputting 14.6V only with no float is not worth it. Not sure why PD is so slow to adopt a proper LiFePO4 charger. I bought their fancy 9160ALV and all it does it crank out 14.6V for a while and then 13.6V. No way to adjust it. I think it is stupid. So don't buy the one they recommended for $350.

 

[SpongeboB Sinewave]

120 volts AC in rectified to 120 volts DC out. Then a high wattage transformer goes from 120 v DC to

14.6 v DC.

Randall

Welcome, Randall....

120 VAC will rectify and filter to just over 166 VDC or so including diode voltage drop so a 200V minimum input will be necessary.

AC isolation using a transformer is highly recommended for safety. Plus, a low Ohm power resistor might also be placed in series to buffer the low input impedance of the system and to make it act slightly more like a real PV array for the MPPT algorithm.

A real AC to DC charger would be much better than trying to do this but people have made it work.

boB

 

[Ampster]

I have determined it does not have a lithium setting.

As long as you can program the Constant Current and Constant Voltage settings you should be fine. Those are typically called Bulk and Absorb in Pb lingo.
As @sunshine_eggo mention you just need a charger that is compatable with Lithium requirements.

 

[Bob B]

As others said, I couldn't find the manual for the model you mentioned .... but a similar model .... indicates it has a switch to select battery type. https://www.etrailer.com/RV-Converters/Progressive-Dynamics/PD4575K18LS8.html

I don't like the idea of a constant 14.6 V.

There are a few threads on here about RV converters on here if you search. With the RV converter, the most important thing would be to make sure it isn't utilizing an equalization cycle designed for FLA batteries.
I would prefer an AGM profile to the constant 14.6

I would try to get Progressive Dynamics to provide me with a manual for the exact model I had .... and use an AGM profile .... or get something like a Victron Multiplus. Your 5th wheel should have a place to mount it.

 

[RandyP]

What I will say is do not buy the Progressive Dynamics replacement for $350. Outputting 14.6V only with no float is not worth it. Not sure why PD is so slow to adopt a proper LiFePO4 charger. I bought their fancy 9160ALV and all it does it crank out 14.6V for a while and then 13.6V. No way to adjust it. I think it is stupid. So don't buy the one they recommended for $350.

So you were able to purchase and physically have a PD9160ALV converter. I have not been able to purchase any PD LiFePO4 rated converter other than their single stage 14.6 volt model (I consider it to be a power supply, not a battery charger). I have seen many retailers show the 2-stage converter part numbers for sale, but when you view a pic of the label on top of the converters, the 'V' suffix is not included in the part number, and the specs they share show 14.6 v output continuous output, not two stage 14.6/13.6 v output.

1. Does the one you have include the V suffix in the part number on the converter label?
2. Have you actually measured 13.6 v output after it has been charging for a period of time ?

 

[RandallCothren]

So you were able to purchase and physically have a PD9160ALV converter. I have not been able to purchase any PD LiFePO4 rated converter other than their single stage 14.6 volt model (I consider it to be a power supply, not a battery charger). I have seen many retailers show the 2-stage converter part numbers for sale, but when you view a pic of the label on top of the converters, the 'V' suffix is not included in the part number, and the specs they share show 14.6 v output continuous output, not two stage 14.6/13.6 v output.

1. Does the one you have include the V suffix in the part number on the converter label?
2. Have you actually measured 13.6 v output after it has been charging for a period of time ?

I wanted to thank everybody for responding and would love to continue the conversation but I think I'm pretty good at this point.
I did not buy the actual converter I referred to I have the one that came with my 2018 RV which is for lead acid.

I think when I'm on Shore power and there is no sun which is rare I will allow the converter to charge the lithium batteries and it will be controlled with the brand new b m s I have bought.

I will turn it on the converter if needed it will charge for a bit and I will keep an eye on it with the Bluetooth and then just turn it off. The BMS will probably do all the thinking for me.

I think the biggest thing I will be mindful of is to whenever it appears to be charged to turn off the breaker to the converter so it doesn't try to go into a float mode which lithium does not like.

 

[sunshine_eggo]

I think the biggest thing I will be mindful of is to whenever it appears to be charged to turn off the breaker to the converter so it doesn't try to go into a float mode which lithium does not like.

If the float voltage is less than or equal to 13.6V, don't worry about it unless you expect to the on shore power for many days/weeks.

Make sure you set a 13.6V float voltage on your solar as well. You need it to force the solar to provide any loads after the battery is fully charged.