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Jasper7821 · 01-28-2014, 03:15 PM

I just bought a Onan 5500 propane generator and I'm building a 24v battery bank out of eight 6v 225ah batteries. This is for a concession trailer I'm building and wanted a few hours of quiet time running on batteries. Everything in the trailer runs on 110v.

I cannot somehow tap into the battery bank to get 12v out of it correct?

If I install a separate 12v automotive battery how do I charge the battery. Can it somehow be charged from my truck when hooked up to the trailer. And if so, how does the wiring go.

If not, I'd probably have to buy a trickle charger and plug it in overnight a few times a week right?

Thanks

Old Bounder · 01-28-2014, 04:40 PM

Quote:

Originally Posted by Jasper7821

I just bought a Onan 5500 propane generator and I'm building a 24v battery bank out of eight 6v 225ah batteries. This is for a concession trailer I'm building and wanted a few hours of quiet time running on batteries. Everything in the trailer runs on 110v.

I cannot somehow tap into the battery bank to get 12v out of it correct?

If I install a separate 12v automotive battery how do I charge the battery. Can it somehow be charged from my truck when hooked up to the trailer. And if so, how does the wiring go.

If not, I'd probably have to buy a trickle charger and plug it in overnight a few times a week right?

Thanks

Absolutely, you can tap off 12V from within your 24V battery array. But, that kind of knocks a hole in your statement that "Everything in the trailer runs on 110V".

EDIT - It just occurred to me that you are needing 12V to start the generator. A separate battery and charger may be the answer, but you could, indeed, tap into the array to obtain 12V for that purpose.

targaboat · 01-28-2014, 05:09 PM

Yes, you can get 12 volts from the bank. Charging the bank is then the question because you should take equal amps from all the batteries. If you are charging them with a 24v charger and if you are taking 12v from half of them, that portion of their charge will never be replaced. The Onan probably has a 12v tap which will keep a small starting battery charged. A voltage regulator would be required if that is not provided in the Onan system.

How are you charging and what are you using 24 volts for.

Jasper7821 · 01-29-2014, 12:23 AM

Thanks. I'm just trying to not have to buy another battery. My 8 battery bank will be charged from the generator when they get down to 20% used. I'll be using a 24v 4000 watt inverter. The total peak draw from the trailer with the appliances will be about 15 amps not including the AC since that will run off the generator only and the appliances will run off the batteries.

I guess it sounds a lot simpler to get a small 12v battery just to start the generator. I don't know if the generator charges that battery or not. If so that would be great. If not then I'll have to charge it somehow.

I know nothing about generators or battery bank systems or inverters. I just wanted my concession trailer not to gave to use the generator to power it all day long. I calculated that I'll be able to run the trailer off just the batteries for 3-4 hours and that will give me the quiet time I wanted. Of course in the summer the AC will be on the whole time so then the generator will also gave to run all day long.

NeilV · 01-29-2014, 03:27 AM

I would have gone with a 12 volt inverter/charger with generator autostart so you could just set is and forget it. It would then take care of any quiet times, monitor the air conditioning starting the generator automatically when the thermostat calls and monitor the charge on the batteries automatically starting the generator when they need to be topped off.

I can't imagine being without the Autostart now that I have gotten use to it.

targaboat · 01-29-2014, 05:06 AM

Still seems that you are not charging the 24v battery bank. The inverter is accounts for your 120v. You need a 24vDC converter. That converts the generator produced 120 AC to the 24v DC to charge the battery. It's possible what you call the inverter is dual function, converter and inverter combined, but the RV people seldom see 24 volts.

targaboat · 01-29-2014, 05:14 AM

Here is a 3600 watt inverter/converter for 36 volt battery.

APS3636VR | Tripp Lite

Jasper7821 · 01-29-2014, 01:07 PM

Quote:

Originally Posted by NeilV

I would have gone with a 12 volt inverter/charger with generator autostart so you could just set is and forget it. It would then take care of any quiet times, monitor the air conditioning starting the generator automatically when the thermostat calls and monitor the charge on the batteries automatically starting the generator when they need to be topped off.

I can't imagine being without the Autostart now that I have gotten use to it.

Thanks, I looked at that Autostart and it was pretty pricey. I haven't bought the batteries or inverter yet so I can install whichever I want. The RV dealer told me to use 24v since the inverter is the same price as 12v and I can use 1 ott wire instead of 4 ott wire and that will save money. And they also said it will be more efficient.

Jasper7821 · 01-29-2014, 01:14 PM

Quote:

Originally Posted by targaboat

Still seems that you are not charging the 24v battery bank. The inverter is accounts for your 120v. You need a 24vDC converter. That converts the generator produced 120 AC to the 24v DC to charge the battery. It's possible what you call the inverter is dual function, converter and inverter combined, but the RV people seldom see 24 volts.

The inverter is a converter and charger too and will charge the 24v battery bank.
4000 Watt 24 volt Low Frequency Inverter Charger

Again, I know nothing about generatos or battery banks. I'm just doing what the inverter and RV company suggested.

targaboat · 01-29-2014, 02:03 PM

Now that we have the whole story we are able to help. Here is a whole page of 24 to 12 volt converters which would be far better then a separate battery to have to worry about. We used these on newer airplanes which had 24 volt systems and older electronics and some of the controls such as flap motors which needed 12 volts.

24 volt to 12 volt DC/DC converters (fully regulated) from 100 to 700 Watts both non-isolated and isolated.

An they do not appear to be very expensive. Now we need to find out how many amps is required to start the generator. It maybe in the specs for the genny. Another way to approach this is to determine the size of the fuse in the starting circuit. Can not imagine it is more than 20 amps.

targaboat · 01-29-2014, 02:08 PM

Lets work on terminology, an inverter changes DC to AC, a converter changes AC to DE. The boxes which do both have both inverter and converter built in. What the English majors put in advertising copy does not count.

targaboat · 01-29-2014, 02:14 PM

You are building a neat system. I would like to see what solar panels would do for you. For that we really need information on your usage history which you probably do not have at this point. We would also need a better picture of your set up to even come close guessing your energy requirements.

Dr4Film · 01-29-2014, 02:55 PM

Quote:

Originally Posted by Jasper7821

I just bought a Onan 5500 propane generator and I'm building a 24v battery bank out of eight 6v 225ah batteries. This is for a concession trailer I'm building and wanted a few hours of quiet time running on batteries. Everything in the trailer runs on 110v.

I cannot somehow tap into the battery bank to get 12v out of it correct?

If I install a separate 12v automotive battery how do I charge the battery. Can it somehow be charged from my truck when hooked up to the trailer. And if so, how does the wiring go.

If not, I'd probably have to buy a trickle charger and plug it in overnight a few times a week right?

Thanks

Is this the LPG Generator model that you purchased? If so, here is the Specification Sheet for that model.

https://powersuite.cummins.com/PS5/P...ets/a-1425.pdf

WRT your 24 VDC Battery Bank by using eight 6 VDC Batteries, I assume that you are planning on connecting each of the four sets of 6 VDC batteries tied in series to form 24 VDC, then the 8 batteries will be connected in Parallel to give you the 24 VDC with about 450+ AH if using the Sam's Club Golf Cart GC-2 Batteries.

The 24 VDC 4000 Watt Inverter/Charger you have chosen will work well with your 24 VDC Battery Bank. I am assuming that the generator will be used to keep the battery bank charged or are you planning to use shore power?

You should NOT tap 12 VDC from your 24 VDC battery bank to start your generator. You will need a separate 12 VDC battery to use for starting the generator. That battery should be charged using either the generator and a 12 VDC battery maintainer or by using shore power. You can also charge the 24 VDC battery bank using the generator or shore power.

If you plan to use the generator for charging all of the batteries, figure on 3-4 hours of run time to do that. It is far more efficient to use shore power than generator power for charging batteries.

Here are a couple of documents that will help you with battery types, inverter's etc.

The 12volt Side of Life (Part 1)

The 12volt Side of Life Part 2

My final comment is regarding your statement about running the battery bank down to 20% BEFORE recharging. Where did you get your information regarding that data?

If you read the very first document listed above, it warns people NOT to use the battery bank to a lower level than 50% SOC. If you do, then the lifespan of your battery bank will be significantly reduced requiring you to purchase batteries far more often than you may want to.

Dr4Film ----- Richard

Old Bounder · 01-29-2014, 08:02 PM

I'm not sure why folks here are so opposed to tapping off 12v from your battery bank to start your generator. It's not likely that you would use that tap for more than a few seconds, once a day, and that would be just to start the gen and the recharging process. Where's the harm? It's the cheapest, best and most efficient way to go.

Note to Dr4film, I think the OP meant recharge at the 80% level. His words were "at 20% used".