More Class C upgrade questions

Grabcon

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I have more questions about an older Class C battery upgrade. As mentioned in previous post my power distribution panel has an integrated Parallax 7300 Converter.

Because of the design of the RV I cannot use the single house battery undercarriage storage for the new batteries. The new batteries will be located somewhere else. I also would initially like to keep the Generator. As like most RV's the house battery is charged from the engine alternator or the Converter/charger and is used to start the generator. The current system does not have an inverter so the only AC is from store or generator.

The plan for the new system is to tie the new inverter into the existing distribution panel for AC/DC. The inverter is a combination in inverter/charger/ATS. The integrated Converter in the distribution panel will be disabled as to not charge the lithium batteries. I really don't care if the NEW lithium batteries get charged from the engine alternator. Solar and the inverter will be used for their charging.

Hopefully this is a clear explanation. Now the real question.
What would be the recommendations as to how should I keep the original house battery charged and maintained so it can be used to start the generator?

NOTE: I know there will be a lot of questions about the details of the build but at this time they are really not important. What is important is that the new batteries will have a minimum of 20 feet of battery cable if I was to tie into the existing cables for the existing house battery. I really don't want to run that much large diameter battery cable.
 

HRTKD

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What would be the recommendations as to how should I keep the original house battery charged and maintained so it can be used to start the generator?

I think you're ignoring some important issues with your system, but I'll focus on this question. On my RV trailer, I separated the house and generator DC systems. I traced the circuits and found that by disconnecting the cables going into the main distribution panel from the original battery (on the tongue), I could create two separate systems. I put in a small lead acid battery on the tongue to start the generator. That battery also takes care of a couple other loads outside the trailer that aren't relevant to a motorhome.

The challenge for you, if you follow what I did, is that the charging of the generator starter battery may have been coming through the main distribution panel. Mine was. The AC-DC converter was located directly below the AC and DC fuses. When I disconnect the cables from the tongue, I lost the ability to charge the lead acid battery. I'm still working on a long term solution for that. I have a 150 watt solar panel that is dedicated to the lead acid battery, so I'm not in any hurry to fix the problem of using AC to charge the lead acid battery. I don't use my generator much, so that's another reason for my lack of urgency.

If you can take the wires from the original converter and wire them directly to the generator starter battery that should be a good start. However, charging that battery from the alternator would be good too, as long as that battery continues to be lead acid. My tongue battery does get a charge from the tow vehicle.
 

Grabcon

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Thanks. The battery that we speak of already gets charged from the alternator. Disconnecting the charging wires from the converter is also not an issue. The issue that I will need to trace out is if I disconnect the wires from the converter will the battery still get a charge from the alternator and will the generator still start.
 

HRTKD

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Pull the wires and see what happens. What's the worst that can happen?
smile.gif


You have a voltmeter handy, right?
 

mkaye

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i replaced my 12V LA with 280Ah LFP - starts the generator w/o any issues
in my case this fit under the steps where the LA battery was located
why can't you move/replace the generator 12V wire to your new LFP location?
 

jwelter99

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Best option is to install a selector switch with the house battery and starter battery as inputs, and the output to the generator starter. A Bluesea 300A works well for this. This way you can easily select what source to start the generator if you find yourself with one of those two banks depleted. Mine stays on house as the default. Any proper system design should also consider how to keep the starter battery charged from the house solar/shore/generator power input.

To solve your problem over locations from the new battery location you need to run:

1) Cable from new battery to original battery location to feed the generator start (or the input of the switch I reference above) and the original DC feed to the load center. Size accordingly for both loads.

2) Cable from the originally battery location that came from the alternator that you use to power a B2B or other suitable lithium battery joiner. I strongly suggest the B2B route. As this cable is the other input of the selector I reference above the ideal place for this selector is in the original battery box if you can get easy access to it for selecting generator start source. Typically under the entry steps so works fine.

These should be separate runs as you will want one controlled by the "charge ok" from the BMS and the other the "discharge ok" from the BMS in the future.
 

Whinny

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The generator may have it's own charging source. Put your voltmeter on the battery with everything turned off, start the gen and see if the voltage goes up on the battery to indicate a charge.
If not you may be able to isolate the converter/charger from the distribution panel and use it to charge the gen battery.
 

jwelter99

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The generator may have it's own charging source. Put your voltmeter on the battery with everything turned off, start the gen and see if the voltage goes up on the battery to indicate a charge.
If not you may be able to isolate the converter/charger from the distribution panel and use it to charge the gen battery.

I've not seen a class-c yet with a independent generator start battery -- does this exist?
 

Whinny

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I was trying to respond to this part of the question...
"What would be the recommendations as to how should I keep the original house battery charged and maintained so it can be used to start the generator?"
 

Grabcon

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Okay so we are operational with the new setup.

To answer a couple of questions for those that responded.
The generator uses the original house battery to start. In the original configuration the house battery was charged two ways, from the vehicle alternator and from the Converter on the Parallax 7300 Converter AC/DC distribution panel.

Now the original house battery only gets charged from the vehicles alternator.

The converter has been disconnected from the Parallax 7300 Converter. Also the battery disconnect switch has been set to the off position and is no longer tied to the distribution panel.

What got installed:
500 watts of solar with another 500 watts by weeks end
Outback FlexMax 80 MPPT SCC
AIMS Power inverter 2000 watt with charger and ATS
2 reBel LiFePO4 12v 100ZH 1280WH Batteries with 2 more by end of summer
New 30AMP shore power connection
Plus all of the fuses, breakers, disconnects, wire, Bus bars, etc.

Everything is operational and now needs off grid shake down test/stress test. That will start in earnest tomorrow.

Here is a diagram of the As built system. The only difference between diagram and what exists is the solar panel connection. Currently parallel, will be series/parallel the the other two are added.
 

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HRTKD

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The generator uses the original house battery to start. In the original configuration the house battery was charged two ways, from the vehicle alternator and from the Converter on the Parallax 7300 Converter AC/DC distribution panel.

Now the original house battery only gets charged from the vehicles alternator.

The converter has been disconnected from the Parallax 7300 Converter. Also the battery disconnect switch has been set to the off position and is no longer tied to the distribution panel.

The generator draws significant amps from the house battery to start the generator. There is much smaller ongoing draw while the generator is running. If you run the generator too long, the house battery could be drawn down quite a bit. This is the issue I was trying to highlight in post #2 of this thread.
 

Grabcon

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Thanks for the clarification of the house battery draw down while the generator is running. Like you maybe a small solar panel is an option and it is still tied to the alternator. A second voltmeter for the house battery may be handy too.
 

Grabcon

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Here is a photo of the final product.
 

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Grabcon

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Stress test one was successfully completed yesterday and today.

8:30 AM unplugged from shore power and we went about our business for 24 hours. Although we didn't have a lot of sun we were still charging. Cooked dinner in the toaster oven, 25 minutes at 350 F, Used the induction cook top at 360 F for 20 minutes, Made several cups of coffee and tea. Left the fridge on electric for 4 hours then turned over to gas. Used a 1500 watt electric heater for several hours, then went to the propane furnace. It was cold here in Denver last night so the furnace ran approximatley every 15 minutes throughout the night. All of our normal electronics and 12 volt systems that we normal use got used as normal. I am confident that we used more power than on a normal day. I am pleased with the out come. batteries were at 23% and 20% before I plugged back in to shore power. 12 hour charge time to 100%.

It is getting to 17 degrees tonight in Denver so we are staying plugged in for the night. I also picked up 2 more 250 watt solar panels today but the weather is not letting me install them.
 

HRTKD

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It is getting to 17 degrees tonight in Denver so we are staying plugged in for the night. I also picked up 2 more 250 watt solar panels today but the weather is not letting me install them.

Congratulations on the test run. It is indeed getting cold in the Denver area. I'm glad that I didn't turn off my battery warming system.
 

Grabcon

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Denver had a break in the weather Tuesday and I got the other 2 solar panels up and operational. Now the only thing left is 2 more batteries. Attached is the latest as built diagram of the system.
 

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HRTKD

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I would have combined the fuse and disconnect switch going to the inverter into a circuit breaker.

I don't see a shunt. How are you planning to gauge the state of charge?

A Class T fuse between the battery bank and the common bus bars is recommended.
 

Grabcon

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HRTKD This basic diagram has been posted since the 14th you should have said something a week ago, LOL

I would have combined the fuse and disconnect switch going to the inverter into a circuit breaker.
The rub I have with circuit breaker is that with these larger cables 1/0 and up is that they put a lot of pressure on the small studs and plastic frame and I have had them fracture in the past.

I don't see a shunt. How are you planning to gauge the state of charge?
I can get the info I need for my needs from the bluetooth BMS app. It may not be perfect but it works for my needs.
A Class T fuse between the battery bank and the common bus bars is recommended.
Are you saying that on every battery connection to the busbar there should be a fuse?
 

HRTKD

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HRTKD This basic diagram has been posted since the 14th you should have said something a week ago, LOL


The rub I have with circuit breaker is that with these larger cables 1/0 and up is that they put a lot of pressure on the small studs and plastic frame and I have had them fracture in the past.


I can get the info I need for my needs from the bluetooth BMS app. It may not be perfect but it works for my needs.

Are you saying that on every battery connection to the busbar there should be a fuse?

Sorry, late to the party. Been busy preparing for a trip.

If you have stress on your studs then you're doing your cables/lugs wrong. When I make my cables I do it so that there is close to zero stress on the studs. I preform the cable as well as orienting the lug to the stud. Once I'm done, I can practically lay the cable down and stays in the right shape. If there are multiple bends then that doesn't quite work.

Ideally, every battery should have a fuse. However, a lot of us cheat and run both batteries through a single fuse. That's what I did. Those Class T fuses aren't cheap!
 

Grabcon

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When I make my cables I do it so that there is close to zero stress on the studs. I preform the cable as well as orienting the lug to the stud. Once I'm done, I can practically lay the cable down and stays in the right shape. If there are multiple bends then that doesn't quite work.
I try to do the same but when dealing with large gauge and short runs of cable that task becomes more difficult. I have also found that on some of the breakers if you slightly over tighten the mounting screws the plastic will fracture too. If you try to mount the breaker to an uneven en surface it will break every time.

The space for the install also impacts what one can do. Although in my photo of the final install one would think that there is plenty of room but that just is not the case. Things are tight.
 
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