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Old 01-23-2020, 10:46 PM   #1
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Default Temporary house battery setup using 24v

I would like to use the van for weekend trips while I plan out a full fledged electric setup. I will be going with 24v system and already have D2 heater from the past van and will be adding a Dometic CFX3 45 fridge. Looking for some ideas to create a temp setup that will help me to use the heater and the fridge.

The van comes with an 12V 95AH AGM aux battery setup which is under the passenger seat, I am thinking I can use a DC-DC charger and a simple charge controller to charge a 24v 100AH Lithium battery through alternator when the van is being driven. Rough schematic

Alternator>Main Battery>AUX Battery>DC-DC 12v to 24V charger>BMS>Lithium Battery

any thoughts if this would work.
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Old 01-23-2020, 10:50 PM   #2
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Default Re: Temporary house battery setup using 24v

Considering you are already having to deal with 24Vdc-12Vdc conversions, why have you chosen to use 24V at all?
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Old 01-23-2020, 10:54 PM   #3
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Default Re: Temporary house battery setup using 24v

My plan is to go with all native 24v appliances/accessories only use 12V where a 24v is unavailable (Fridge and heater which are key appliances are already available in 24v), also 24V due to planned split AC addition in the future.
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Old 01-24-2020, 12:41 PM   #4
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Default Re: Temporary house battery setup using 24v

I might be able to help you with a temporary 24 volt setup.

Not precisely what you have written, but would work while you figure out the rest of the details for your larger system.

Are you going to have solar panels right away or is that down the road a bit?

Is the van interior always going to be above ~ 40 F ? Usually people in your area go to mount hood in the winter.

The main risk of your plan is related to how much driving you will do vs the power draw of the fridge. My quick estimate is that your bank will run for ~ 3 days if things are left on and no solar.

I will send an email to you.

Harry
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Last edited by HarryN; 01-24-2020 at 12:57 PM.
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Old 01-24-2020, 06:41 PM   #5
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Default Re: Temporary house battery setup using 24v

Quote:
Originally Posted by HarryN View Post
I might be able to help you with a temporary 24 volt setup.

Not precisely what you have written, but would work while you figure out the rest of the details for your larger system.

Are you going to have solar panels right away or is that down the road a bit?

Is the van interior always going to be above ~ 40 F ? Usually people in your area go to mount hood in the winter.

The main risk of your plan is related to how much driving you will do vs the power draw of the fridge. My quick estimate is that your bank will run for ~ 3 days if things are left on and no solar.

I will send an email to you.

Harry
I am thinking to with with Victron buck-boost charger paired with a BMS and a couple of 200AH 12v Lithium battery pack in series. I would be driving minimum an hour a day to trailheads/camping spot to keep the charge topped off. of course heading from home to camp would involve 3-4 hrs of driving.
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Old 01-25-2020, 04:39 PM   #6
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Default Re: Temporary house battery setup using 24v

Quote:
Originally Posted by pdxhiker View Post
I would like to use the van for weekend trips while I plan out a full fledged electric setup. I will be going with 24v system and already have D2 heater from the past van and will be adding a Dometic CFX3 45 fridge. Looking for some ideas to create a temp setup that will help me to use the heater and the fridge.
My idea was a bit more simplistic and intended to help you make it through the 6 month gap between now and when you have the electrical system that you desire for running the air conditioning. It may or may not work for you.

We use two different size cases to build the products:
~ 20 x 30 x 12 H inch
~ 20 x 30 x 20 H inch

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The larger case systems have an insulated battery pack area, so they can be used with Li or AGM, 2 or 4 batteries. ( Lifeline size 27 or Battle born). Example:

https://wirlnet-inc.square.site/prod...stem/6?cs=true

I wouldn't knowingly put LiFe batteries into an uninsulated version if the customer is likely to use the system for use in areas that receive snow.

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The smaller case is the size of a full size suit case and can be used in any angle, but the battery pack area is not insulated, so it is really only for Lifeline size 24 AGM batteries.

Example:

https://wirlnet-inc.square.site/prod...ans/43?cs=true

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Depending on the application, we wire them 24 or 48 volts internally, then use DC - DC converters to make the desired regulated 13 volts, USB, etc on the output as needed.

I have one of these small case systems that I use as a demo unit in a 1x1 configuration.
- 1 kW inverter
- 1 kW-hr usable AGM capacity (2 x 80 amp-hr wired in series)

Since it is AGM based, there is a fundamental assumption that there will be some solar charging and ideally also some alternator / battery to battery based charging.

______________

My early morning coffee thoughts were to rent a 1x1 system to you for 6 months while you figure out what you actually need long term. I haven't done "rentals" before so it isn't a well formulated idea, just an idea.

__________

The pros of this idea is that it is quick and can power the items that you mentioned - even ski trips to Mt Hood.

The limitations of this concept is that AGM batteries really need fairly regular 3+ hr charge cycles. It would not be able to keep up with your fridge + heater without at least some solar power installed.

The amount of driving that you are talking about would not be enough to keep an AGM battery pack sufficiently charged.

If you temporarily mounted a couple of flex panels on the roof, that would help it work.

_______________

I don't have other "temporary" solutions, so if you are focused on going down a LiFe path right away, that would have to be purchased and built. That takes some time.
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Last edited by HarryN; 01-25-2020 at 04:41 PM.
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Old 01-25-2020, 06:10 PM   #7
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Default Re: Temporary house battery setup using 24v

Quote:
Originally Posted by pdxhiker View Post
I would like to use the van for weekend trips while I plan out a full fledged electric setup. I will be going with 24v system and already have D2 heater from the past van and will be adding a Dometic CFX3 45 fridge. Looking for some ideas to create a temp setup that will help me to use the heater and the fridge.

The van comes with an 12V 95AH AGM aux battery setup which is under the passenger seat, I am thinking I can use a DC-DC charger and a simple charge controller to charge a 24v 100AH Lithium battery through alternator when the van is being driven. Rough schematic

Alternator>Main Battery>AUX Battery>DC-DC 12v to 24V charger>BMS>Lithium Battery

any thoughts if this would work.
If you decide to stay within the 40 amp / ~ 500 watt rated draw of the sprinter body builder manual, then in 2 hrs of driving, that would be ~ 1 kW-hr.

As an example, if you did this with 2 battle born 100s, this would run the fridge and heater ~ 2-3 days. Doubling the number of batteries would only help if you turned off the fridge while not in use, or if you charged them up at home first before the trip.

This assumes that the batteries stay within the operating temperature range of course.
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Old 01-26-2020, 08:42 PM   #8
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Default Re: Temporary house battery setup using 24v

Hi Harry - thanks for the help, even if temporary for now. I am actually looking to buy the components that I can extend later in year or two hence going with Victron setup.
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Old 01-27-2020, 07:06 PM   #9
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Default Re: Temporary house battery setup using 24v

A straight victron set up can work. Other than their 5000 series inverters (which are very good) , the rest of their stuff is decent / average. Shouldn't be difficult to put a system together with it.

All of the blue sea and similar marine components are 24 volt rated.

It is all just a matter of investing the time to read the manuals, buying parts and focus.
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