New to the forum introduction plus 24v charger question

[John503]

TL;DR I need a lifepo4 24v20ah charger!

Hi! I'm new to the forum but happy to be here! I recently built the following system in my 27ft camper:

Battery: Two 200amp hour 12v lifepo4 Redodo batteries wired in series for 24v/200ah.

Chargers: Two EG4 24v/40ah chargers (80ah total) that I got from Signature Solar. They were advertised as 30ah but when they arrived I realized they were actually 40ah. I cannot find them on the internet ANYWHERE now, but here is a similar one at only 35ah https://signaturesolar.com/eg4-battery-charger-24v-35a-1/

Inverter: Vevor 24v 3500 watt pure sine wave inverter.

12v supply: Uxcell 24v to 12v voltage converter (60amp) to run all the 12v devices.

Generator: 3500 watt dual fuel Champion. I run it exclusively on propane and hope to never put a drop of gasoline in her.

Solar: Four 100 watt Renogy panels and a Renogy Rover 20 amp mppt. I also have a Renogy Rover 40 amp that is currently unused. I plan to massively increase my solar in the future. I have a full shop and like to fabricate stuff, so I will probably build my own adjustable mounts allowing me to angle the panels at will, mount panels to the sides of the RV that fold upwards, etc.

Question:
I setup relays/switches so I can turn the chargers on/off individually as to not overload a standard 120v outlet.

The generator has power to spare, so I would like to obtain an additional 20ah charger to increase charging from 80ah to 100ah.

There used to be an EG4 charger sold at Signature Solar that was in the realm of 20ah, but I don't see it for sale anymore. I don't see the 40ah chargers I purchased either

What other 20ah chargers should I consider?

Should I consider two 12v chargers and wire them to the batteries individually while simultaneously charging the string at 24v with my existing chargers? Sort of like a balancing system? Is that even possible?

 

[740GLE]

Victron 24V MultiPlus-II 3kVA 120V Inverter 70A Charger | Current Connected

Experience flexibility and adaptability with the Victron MultiPlus-II 24V Inverter, perfect for on and off-grid applications with industry-leading features.

www.currentconnected.com

Perfect unit, I’d set it to charge at 50a, plus it’ll solve a lot of your future problems ?

Battery Balancer - Victron Energy

Equalize the state of charge of two series connected 12V batteries using the Battery Balancer. Find a Victron Energy dealer near you.

www.victronenergy.com

Plus this to keep your 12v batteries happy

 

[John503]

Victron 24V MultiPlus-II 3kVA 120V Inverter 70A Charger | Current Connected

Experience flexibility and adaptability with the Victron MultiPlus-II 24V Inverter, perfect for on and off-grid applications with industry-leading features.

www.currentconnected.com

Perfect unit, I’d set it to charge at 50a, plus it’ll solve a lot of your future problems ?

What future problems are you implying? Everything is working flawlessly so far and we just got back from a 2.5 week road trip without shore power. I'm not sure why I would throw a grand at that Victron unit when I already have an inverter and 80 amps worth of charging ability. I just need an additional 20 amps worth of charging to max out my generator's capability. I'd prefer to run it for as short of time as possible since they are loud. Not disagreeing with you and Victron sure does make nice stuff, but can you explain why I should shell out another grand to basically replace what I already have?

I only drain my bats to 20% at most and I have a Shunt that keeps track of my SOC if that makes any difference.

 

[John503]

And as far as that balancer goes, I looked at this same unit a while ago but never bought it . Is it definitely worth using one? How important is balancing with two 12v in series? Obviously they both have their own internal BMS's and the manufacturer doesn't push using a balancer. But I definitely want to do everything I can within reason to protect my batteries.

 

[740GLE]

What future problems are you implying? Everything is working flawlessly so far and we just got back from a 2.5 week road trip without shore power. I'm not sure why I would throw a grand at that Victron unit when I already have an inverter and 80 amps worth of charging ability. I just need an additional 20 amps worth of charging to max out my generator's capability. I'd prefer to run it for as short of time as possible since they are loud. Not disagreeing with you and Victron sure does make nice stuff, but can you explain why I should shell out another grand to basically replace what I already have?

I only drain my bats to 20% at most and I have a Shunt that keeps track of my SOC if that makes any difference.

If you’ve used this set up and haven’t run into any issues starting motors or pumps them you’ll have smooth sailing for some time. I just perfer to have some reactive power capabilities, vs a HF inverter.

While I can understand running the generator as little a possible, have you thought about the lifespan of that generator running at full tilt? I’d personally would run it 1/2 power and get ten times the hours out of it before blow by starts becoming a problem.

 

[John503]

Yeah that's why I got an oversized 3500 watt inverter to run a 1400 watt air conditioner. It starts up fine even when running the microwave, not that I ever use the microwave, but I guess if I wanted to it wouldn't be an issue. Nothing else really runs on 120v in my RV.

The water pump is 12v so it doesn't run off the inverter.

The generator will be running around 90% output which seems fine to me, I'm not sure what blow by is. I run it on propane but it can put out another few hundred watts on gas if I need to, but I'd rather not.

I only use the RV for camping a handful of times per year, and will only need the generator for 2-3 hours per day to charge the batteries. If it craps out on me with such light usage I'll just buy a Honda.

Anyone else have suggestions on a good 24v 20 amp charger?

 

[John503]

Actually what I would really like is a 24v charger with adjustable output so I can dial it down, for example if I was at high altitude generators puts out considerably less power. Hmm

 

[Dynoman]

TL;DR I need a lifepo4 24v20ah charger!

Hi! I'm new to the forum but happy to be here! I recently built the following system in my 27ft camper:

Battery: Two 200amp hour 12v lifepo4 Redodo batteries wired in series for 24v/200ah.

Chargers: Two EG4 24v/40ah chargers (80ah total) that I got from Signature Solar. They were advertised as 30ah but when they arrived I realized they were actually 40ah. I cannot find them on the internet ANYWHERE now, but here is a similar one at only 35ah https://signaturesolar.com/eg4-battery-charger-24v-35a-1/

Inverter: Vevor 24v 3500 watt pure sine wave inverter.

12v supply: Uxcell 24v to 12v voltage converter (60amp) to run all the 12v devices.

Generator: 3500 watt dual fuel Champion. I run it exclusively on propane and hope to never put a drop of gasoline in her.

Solar: Four 100 watt Renogy panels and a Renogy Rover 20 amp mppt. I also have a Renogy Rover 40 amp that is currently unused. I plan to massively increase my solar in the future. I have a full shop and like to fabricate stuff, so I will probably build my own adjustable mounts allowing me to angle the panels at will, mount panels to the sides of the RV that fold upwards, etc.

Question:
I setup relays/switches so I can turn the chargers on/off individually as to not overload a standard 120v outlet.

The generator has power to spare, so I would like to obtain an additional 20ah charger to increase charging from 80ah to 100ah.

There used to be an EG4 charger sold at Signature Solar that was in the realm of 20ah, but I don't see it for sale anymore. I don't see the 40ah chargers I purchased either

What other 20ah chargers should I consider?

Should I consider two 12v chargers and wire them to the batteries individually while simultaneously charging the string at 24v with my existing chargers? Sort of like a balancing system? Is that even possible?

Don't have any good info for a 24 volt charger, but for the Renogy Rover suggest reading this post about configuring the Rover for Lifepo4 cells. After reading the post suggest reading the entire thread for additional information on the Rover.

Renogy 40a mppt Li settings

Thanks for the info, I get no heat from the 2 awg wire so that's good for me. Just ordered a 40a circuit breaker to go between the charge controller and batteries plus the Blue Sea 5191 terminal block and 200a fuse today. The 8 guage is less than 2 feet and I did find a little heat when the...

diysolarforum.com

 

[John503]

Thanks for the reply, but I am a little confused by the recommended user settings. My battery manufacturer recommends a charge voltage of 29.2v and the AC chargers I use are already charging at 29.2v, so why would I want to solar charge at a lower voltage? Wouldn't this decrease the speed at which I can charge from solar?

 

[TommySr]

Anyone else have suggestions on a good 24v 20 amp charger?

John503, the Powermax PM3-20-24LK has worked for me without issue(6 years so far).

Tommy
SE Wisconsin

 

[Dynoman]

Thanks for the reply, but I am a little confused by the recommended user settings. My battery manufacturer recommends a charge voltage of 29.2v and the AC chargers I use are already charging at 29.2v, so why would I want to solar charge at a lower voltage? Wouldn't this decrease the speed at which I can charge from solar?

From the Redodo web site:
"we recommend battery charger that supports LiFePO4 battery charging. To fully charge the battery, the DC charging voltage should be between 14.2V~14.6V, and charging current less than 100A. And we usually recommend 0.2C charging current"

This is a battery charger and the solar is less at 400ah(Batteries) / 60a (max of Rover 20 & 40) = 0.15C charge rate, but that is not a problem. With solar a charge rate of 0.10C is still good in my opinion.

So for 24 volt system it would be 28.4 volts to 29.2 Boost setting. Normally charging to the max of 29.2 is not recommended because the BMS in the battery may go into overvoltage protection at the max voltage shutting down the battery. Suggest trying 28.4 to 28.6 for a boost setting. The battery will still charge fast at 28.4 to 28.6 boost setting as it is in what's called the upper knee of the Lifepo4 charge voltage curve. Try a boost time of just 10 minutes to start and if the BMS does not go into over voltage protecting set the boost time to 20 minutes.

Suggest reading & studying the rest of the thread if have not already. In particular read about the tail or taper current and knowing when a battery bank is fully charged and how to keep them balanced.

Renogy 40a mppt Li settings

Thanks for the info, I get no heat from the 2 awg wire so that's good for me. Just ordered a 40a circuit breaker to go between the charge controller and batteries plus the Blue Sea 5191 terminal block and 200a fuse today. The 8 guage is less than 2 feet and I did find a little heat when the...

diysolarforum.com

 

[John503]

The two EG4 chargers I'm using are 40 amps each and 29.2v (.4c charge rate) and I'm not planning to stop using those. So my batteries see 29.2v regularly, regardless of my solar system settings...so I'm still confused why solar charging should be any different from non-solar charging.

Power is power, am I right? How would the batteries know the difference? Or are you saying that preferably all charging should be done at this lower voltage? I obviously cant control that since most non-solar chargers don't allow adjustment to their algorithms.

During non-critical times I plan to charge with just one charger and keep the batteries around 70%, but when I am out camping and charging with a generator and solar, I want to charge at the absolute fastest speed my system will allow me to. Obviously my batteries will last longer if I slow charge them and never charge above 80%, use lower voltages, etc, but I will only be camping a few times per year and want peak performance from them during those times. Think of it like a Tesla; slow charge at home but occasionally use a super charger when out on the road. I want my batteries to last, but I don't need them to last forever.

 

[John503]

This is a battery charger and the solar is less at 400ah(Batteries) / 60a (max of Rover 20 & 40) = 0.15C charge rate, but that is not a problem. With solar a charge rate of 0.10C is still good in my opinion.

Renogy 40a mppt Li settings

Thanks for the info, I get no heat from the 2 awg wire so that's good for me. Just ordered a 40a circuit breaker to go between the charge controller and batteries plus the Blue Sea 5191 terminal block and 200a fuse today. The 8 guage is less than 2 feet and I did find a little heat when the...

diysolarforum.com

My battery bank is 200ah 24v, so the rovers combined would be a charge rate of .3c right?

 

[Dynoman]

My battery bank is 200ah 24v, so the rovers combined would be a charge rate of .3c right?

Yes, that is correct. I misread your initial post. Although it may be difficult to get the full 60 amps from the 2 controllers it is possible.

 

[Dynoman]

The two EG4 chargers I'm using are 40 amps each and 29.2v (.4c charge rate) and I'm not planning to stop using those. So my batteries see 29.2v regularly, regardless of my solar system settings...so I'm still confused why solar charging should be any different from non-solar charging.

Power is power, am I right? How would the batteries know the difference? Or are you saying that preferably all charging should be done at this lower voltage? I obviously cant control that since most non-solar chargers don't allow adjustment to their algorithms.

During non-critical times I plan to charge with just one charger and keep the batteries around 70%, but when I am out camping and charging with a generator and solar, I want to charge at the absolute fastest speed my system will allow me to. Obviously my batteries will last longer if I slow charge them and never charge above 80%, use lower voltages, etc, but I will only be camping a few times per year and want peak performance from them during those times. Think of it like a Tesla; slow charge at home but occasionally use a super charger when out on the road. I want my batteries to last, but I don't need them to last forever.

My understanding is it is not good practice to charge the batteries to max which is 3.65 per cell. For the 12 volt batteries that is 3.65 x 4 = 14.6v and for the 2 12 volt batteries it is 29.2v. If the batteries were to be charged to 28.6 volts instead of 29.2 the batteries would still be essentially fully charged at around 98 to 99%.

Since the 2 EG4 chargers are charging to 29.2 volts it is what it is (this is not adjustable?). Suggest checking what the voltage is at each battery with a good voltmeter when the charging voltage is maximum. It may be found that the charger is actually charging to a lower voltage than 29.2 volts. Also I would check that the BMS is not disconnecting the battery from the charger due to overvoltage. When charging to a high voltage like 29.2 volts it is very possible the BMS will disconnect the battery from the charging source due to a single or multiple cells going over 3.65 volts.

Technically charging to max of 29.2v is OK, but I certainly would not recommend it and definitely not with the Rovers. The Rover output is not accurate enough to charge to 29.2v so I stand by my recommendation of 28.4 to 28.6 for a boost setting. If you want to push it further (say 28.8v boost) suggest measuring the voltage directly on each of the batteries with a good voltmeter (not the Rover voltmeter) while the Rovers are near the end of the boost cycle to ensure not over charging the batteries above 14.6v. But, is it really worth it for another 1 or 2%? Also I would check that the BMS is not disconnecting the battery from the Rover due to overvoltage.

The Speed of charge will be no different with the Rover Boost voltage set at 28.6 or 29.2 volts. It will only be are the batteries 99% charged (28.6v) or are they 100% (29.2v) charged.

In theory the BMS in the battery will protect it, but the BMS should be considered a fail safe and not used to stop the charging process.

 

[John503]

I think there's a misunderstanding here between charging voltage and battery full charge voltage.

My battery, like almost all lifepo4's, is considered full at 13.6v (27.2 for the pair in series).

My charger charges at 29.2v (14.6v per battery), but once they are full, it stops and the surface charge drops on its own to 27.2v (13.6 per bat).

Just like in most vehicles, the lead acid battery is full at 12.8, but the alternator "charges" at around 14v. Once you turn off the car and the alternator stops charging, the voltage drops back down to 12.8 within minutes.

Of course I don't rely on the mppt controllers for accurate readings, LOL. I use a klein multimeter and have a backup to test against. It's definitely accurate. I also have a clamp meter that doubles as a multimeter, and all three read the same.

 

[Tomthumb62]

Thanks for the reply, but I am a little confused by the recommended user settings.

I had a Renogy Rover 30A. It was a nightmare trying to get the settings right. I spent hours reading long threads about how to program it. You need the Bluetooth dongle to do it properly. In the end, I didn’t trust it wasn’t harming my brand new expensive lifepo4 battery, so I sold it and bought a Victron 100/30 to replace it. Not only was programming it a breeze, but I found a 15-30% increase in solar production. I never once had to fire up the generator in 2 months on the road and rarely had to plug into shore power.

I know you don’t want to spend money on replacements, but having had a full setup of Renogy gear, I am so glad to be done with that junk! Also, Victron massively lowered the price on their charge controllers last year, which makes it more price competitive.

 

[Dynoman]

I think there's a misunderstanding here between charging voltage and battery full charge voltage.

My battery, like almost all lifepo4's, is considered full at 13.6v (27.2 for the pair in series).

My charger charges at 29.2v (14.6v per battery), but once they are full, it stops and the surface charge drops on its own to 27.2v (13.6 per bat).

Just like in most vehicles, the lead acid battery is full at 12.8, but the alternator "charges" at around 14v. Once you turn off the car and the alternator stops charging, the voltage drops back down to 12.8 within minutes.

Of course I don't rely on the mppt controllers for accurate readings, LOL. I use a klein multimeter and have a backup to test against. It's definitely accurate. I also have a clamp meter that doubles as a multimeter, and all three read the same.

The issue with charging to 29.2 volts is it is very possible to have the BMS disconnect the battery from the charger due to a single cell in the battery going over voltage. A 12 volt battery has 4 cells and rarely do they stay in balance all the way up the upper charge knee to 14.6 volts.

When one cell gets to 3.65 volts first the BMS should disconnect the battery from the charger. The battery voltage (and cells voltage) will then slowly drop until the BMS reconnects to the charger when the over voltage condition no longer exists. This can go on and on (BMS disconnect then BMS connect) as long as the charger is charging at 29.2 and BMS is disconnecting due to over voltage.

This is not good for the battery, BMS or charger. The BMS will protect the battery (if it is a good BMS), but it is not good practice to have the BMS disconnecting the battery from the charger. Instead stop the charging say at Boost (absorb) at 28.4 volts (or before the BMS goes into over voltage) and then go to Float at 27.2 Volts.

That is my 2 cents worth...

 

[sunshine_eggo]

I think there's a misunderstanding here between charging voltage and battery full charge voltage.

My battery, like almost all lifepo4's, is considered full at 13.6v (27.2 for the pair in series).

Sorta. Certainly true for a resting voltage. Not so as a charging voltage.

Charging to 13.6V may require an extended absorption period with a tail current of near 0A to achieve close to full charge.