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Topic: Hybrid lithium flooded lead acid expansion FYI (Read 522 times) previous topic - next topic
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Hybrid lithium flooded lead acid expansion FYI
In anticipation of converting a Dometic RM2663 3-way refrigerator to have a compressor cooling unit ($700) I wanted to expand the battery bank. Two hundred AmpHours of lithium and 225 AH of FLA would probably do it but since we had the room I have added another 200AH of lithium and another 80 amps of charging capability.

Total charging capability is 240 amps or approximately 3400 watts which makes good use of a 4kw generator. Generator run times are between 15 and thirty minutes and are expected to stay the same with the compressor fridge, expanded battery bank and added charging capability.

Both dinette benches were used in a 2006 Lazy Daze Rear Bath. The forward one contains two 100AH lithium batteries, two 60 amp chargers, 1500 watt inverter, transfer switch, DC to DC charger, cooling fan, and battery selector switch. The aft dinette bench has two more lithium batteries, 80 amp charger, and another vent fan. The aft bench retains the storage drawer added earlier.

The DC to DC charger is used to top off the FLA batteries from lithium to 100% when solar (200 watts) is not up to the job. $5500 pretty much covers the installation. It always amazes me how much work an electrical up grade requires. I will post when I find out what the maximum charging rate will be. With two lithiums and two six volt FLAs it was about 110 amps. One hundred eighty out of a theoretical maximum of 240 amps would be nice. Generator run times should be very short.

The refrigerator conversion is in the future tho I do have the compressor cooling unit.
Harry 2006RB
Re: Hybrid lithium flooded lead acid expansion FYI
Reply #1 –
What compressor cooling unit ($700) are you using?  Nice setup.

Ron
Re: Hybrid lithium flooded lead acid expansion FYI
Reply #2 –
Dometic 2652 Series Hvac 12/24V 7.5A 90W @ 12V ( F ) | JC Refrigeration

I haven't installed it yet so I can't vouch for it nor can I say how many amp hours per day it will use. I'm expecting somewhere between 50 and 100AH. Six hundred twenty five amp hours of battery is hopefully overkill.
Harry 2006RB
Re: Hybrid lithium flooded lead acid expansion FYI
Reply #3 –
Quote from: hbn7hj  - 
Both dinette benches were used in a 2006 Lazy Daze Rear Bath. The forward one contains two 100AH lithium batteries, two 60 amp chargers, 1500 watt inverter, transfer switch, DC to DC charger, cooling fan, and battery selector switch. The aft dinette bench has two more lithium batteries, 80 amp charger, and another vent fan. The aft bench retains the storage drawer added earlier.
The compartment in the picture looks crowded, which may prevent adequate cooling. Have you tested the installation under full load yet?
2005 Jayco 24SS
Re: Hybrid lithium flooded lead acid expansion FYI
Reply #4 –
Quote from: Eric Greenwell  - 
The compartment in the picture looks crowded, which may prevent adequate cooling. Have you tested the installation under full load yet?
Sure. You can’t see the squirrel cage fan below the battery switch that brings in outside air or the vent outlet at the top of the picture. The chargers have their own fans and they turn off when over temped. They have never turned off. Batteries heat also but I don't run A/C by battery so it isn't an issue. The inverter running the microwave is 100 amps short term. The inverter also has its own cooling fan and has never turned off. The forward battery compartment with chargers has been run for two years. I can feel warm air at the vent exit when charging. I finally have the fans turn on automatically when AC is applied to the chargers. Before it was manual and I sometimes forgot but things still didn't overheat and turn off.

All the heat generating items have internal fans. Combined with the cooling fan bringing air into the compartment it works tho crowded. The concern is a 12 volt fire caused by high current through a resistive connection. Occasionally I open it up under load looking for hotspots. Haven't found any yet. The batteries feed through 200 amp DC circuit breakers. All 12 volt connections are covered.

No doubt it is not a commercial quality installation. Wiring should be tied down more and tests would have to be run with temperature sensors. It works. All batteries are at 100% state of charge daily at sunset. This season, if it ever gets started, we will run the propane fridge. Not looking forward to the 100AH+ daily draw of the compressor fridge even tho I can support it. I am looking forward to hard ice cream and no leveling requirement!

The 40 amp DC charger for the FLA batteries is on the aft face of the front bench outside the compartment. Total charging capacity is 240 amps but it doesn't all go through a single point. The maximum would be the 80 amps from the aft charger before it splits off through a circuit breaker to the two batteries. Four gauge fine wire cable is used in high current areas. Six gauge everywhere else.

I cannot run the chargers from shore power as they are on the generator output line before the transfer switch.
Harry 2006RB
Re: Hybrid lithium flooded lead acid expansion FYI
Reply #5 –
Quote from: hbn7hj  - 
I cannot run the chargers from shore power as they are on the generator output line before the transfer switch.

With all the electrical modifications, why not installed a second transfer to allow charging on shore power to provide more flexibility?

Larry
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: Hybrid lithium flooded lead acid expansion FYI
Reply #6 –
Quote from: Larry W  - 
With all the electrical modifications, why not installed a second transfer to allow charging on shore power to provide more flexibility?

It already has two transfer switches, the second for the inverter. I do have a 20 amp power in receptacle through the floor by the battery box that the two 60 amp chargers can access. The 80 amp can’t get to it and it can’t handle the extra power anyhow. l put it in to use my Honda 1000 generator as a backup before I realized the little Honda can’t even power one 60 amp charger. It will power the Xantrex 40 amp charger and I can put the battery switch to both to charge the lithium. I don’t carry the Honda anymore. I can run a standard extension cord from a power pedestal if I have to.

The main reason it is configured that way is I couldn’t conveniently get to the shore power line. The generator line is right there. Now that I have accessed the aft bench the shore power is just on the other side of the wall. It would take a 30 amp switch and a transfer switch. I rarely plug in anymore.

The reason it was done is I signed off of RV parks when the long term rate went to $50 a day at my regular destination. I bet they would like to have my $25 a day now. It won’t last.

The main thing I’m missing is a way to charge from the alternator. A 50 amp DC to DC charger would do it. The system is for long term stays and I don’t miss it. If I daily travel I use a class B.
Harry 2006RB
Re: Hybrid lithium flooded lead acid expansion FYI
Reply #7 –
Quote from: Larry W  - 
With all the electrical modifications, why not installed a second transfer to allow charging on shore power to provide more flexibility?

After thinking about it all it takes is a 30 amp AC double throw double pole switch to get AC to the 80 amp charger from shore power. I’ll keep it in mind for the next mod session. Home Depot has the switch.
Harry 2006RB
Re: Hybrid lithium flooded lead acid expansion FYI
Reply #8 –
Maximum charge rate appears to be 110 amps into the lithium and 40 amps into the FLA which quickly tapers off. I had expected more into the lithium but that is the way it is.

One lithium battery with a 60 amp charger charges at 58 amps. Two batteries with two 60 amp chargers charges at 95 amps. Four batteries with 200 amps  of charge capability charges at 110 amps. Don't know why that is. Still results in pretty short generator run times.
Harry 2006RB
Re: Hybrid lithium flooded lead acid expansion FYI
Reply #9 –
Quote from: hbn7hj  - 
One lithium battery with a 60 amp charger charges at 58 amps. Two batteries with two 60 amp chargers charges at 95 amps. Four batteries with 200 amps  of charge capability charges at 110 amps. Don't know why that is. Still results in pretty short generator run times.
Perhaps the generator output voltage is falling as you add chargers to the system? Many chargers pull significant current near the peak of the voltage sine wave, causing the peak voltage to drop more than the average voltage you see on the a voltmeter, so each charger now puts less than when it was working alone. Generators can also have problems with microwave ovens, which also tend to draw a lot of current near the peak of the AC sine wave, but have no problems powering toasters, which draw power over the entire AC cycle.

I asked Onan support about this once, and the solution offered was "get a bigger generator". Possibly, an inverter generator would work better, but I'm not familiar with them.
2005 Jayco 24SS
 
Re: Hybrid lithium flooded lead acid expansion FYI
Reply #10 –
The generator is doing its part raising voltage as high as 125 volts as the chargers come online. The problem is probably in the interactions of the chargers as charging voltage is 13.8 volts with everything running, rising to 14.5 or so at full charge. I would expect something around 14.4 volts would give the expected charging rate. i have the instrumentation so will monitor charging voltage while switching on the chargers individually. Perhaps a single 200 amp charger, if available, would improve things.

110 amp charge rate is certainly adequate, 150 amp initial rate if you include the FLA charger. I just expected more.
Harry 2006RB