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Sprinter RV's & Conversions Talk Common features found in Sprinter RV's and Conversions.


 
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Old 06-18-2011, 03:10 PM   #1
jmgasior
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Default electrical question

getting ready to install house battery on my 2008,but since i,m challanged i decided for a kiss idea.i have a inteli power 9200 in the rear and will install the battery in the engine comp and will connect the convertor to the battery directly with # 4 wire,when i have shore power the convertor will charge the battery and with no shore power will run off the house battery( only use is led lighting) when the battery gets down to 50 % or so and no shore power in sight,thought about making a # 2 jumper wire to put on the red jumping terminal to the + terminal on the house battery when i,m driving to charge the battery and when i get to the campground remove it so as n ot to draw down the engine battery,the reason for this idea is i read so many posts on isolater idea that i,m comp letly mystified on how to install it and screwing up the sprinter electronics,is this workable or am i missing something?hoping for some answers,thanks
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Old 06-18-2011, 04:30 PM   #2
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Default Re: electrical question

Makeshift connections like you propose always create a risk of melted wiring, shorted batteries or even a fire. It's easy to install an inexpensive continuous duty solenoid, actuated with a switch, to charge the auxiliary battery. Fuse all connections close to each battery, including the connection from the converter.

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Old 06-18-2011, 05:24 PM   #3
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Default Re: electrical question

I agree with Byron's comments re fusing and fires.

That said, looking at *just* your suggested hook-up, it would be a good idea to put an isolator relay in the #2 cable between the Jump post and your "house" battery's positive terminal, and make the wire a "permanent" item.
The isolator would connect the batteries together when the alternator was running, and disconnect them when it wasn't.
Putting a 150 or 200 amp fuse in that line would be good, too.
The signal telling the isolator when to "connect" would be tapped from any "D+" source in your fuse boxes.
(you may even have a set of terminals under the driver's seat which provide "battery, D+ and ground" for "aftermarket" accessories).

Putting in a wire that you have to manually connect and remove is a recipe for unwanted adventures....
(think:if when one end broke free when you drove across a pothole, what piece of metal in the engine compartment would the loose end of the wire weld itself to?)

--dick
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Old 06-18-2011, 05:34 PM   #4
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Default Re: electrical question

Read the "orton DIY -vehicle inverter installation" for a method of charging house battery from vehicle 12 volt system while driving. The vehicle inverter supplies 120 volt power for charging the house battery when engine is running.
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Old 06-18-2011, 06:25 PM   #5
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Default Re: electrical question

I don't understand why you would want to convert 12V DC to 120V AC with an inverter and then back to 12V DC with a charger. It can be done, but each voltage conversion introduces inefficiencies that don't occur with a direct connection from the alternator. In addition, it's much more complicated and expensive than simply using a solenoid to connect the two batteries together.

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Read the "orton DIY -vehicle inverter installation" for a method of charging house battery from vehicle 12 volt system while driving. The vehicle inverter supplies 120 volt power for charging the house battery when engine is running.
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Old 06-18-2011, 08:41 PM   #6
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Default Re: electrical question

while i appreciate the responses ,nowhere did i mention a invertor,the answers now are going in a different direction,thanks
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Old 06-19-2011, 01:48 AM   #7
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Default Re: electrical question

If you install an inverter powered by the Sprinter 12 volt system you can get 120 volt sine wave power when the engine is running. This allows you to charge the house battery while you are driving. The normal way to charge the house battery is to connect the house battery to the vehicle battery after the engine is running. There are several disadvantages to following the crowd. If you read about the proper way to charge a battery, the consensus is it is better to charge a battery with a 3 stage charger. The 3 stage charger has settings that adapt the charger to the battery. The ideal charge profile for a battery is related to the battery type, the battery size and even the battery manufacturer. When you connect to different size batteries of different types together you can not charge them correctly.
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Old 06-19-2011, 02:21 AM   #8
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Default Re: electrical question

Your method is excellent if it's going to be the primary way to charge an auxiliary battery, but the OP said his connection would only be used occasionally, when shore power wasn't available.

I use three different charging methods, primary is a three stage solar panel charge controller, secondary is a PD 9260 three stage converter when connected to shore power, and I can also use the alternator to charge the coach batteries for those times when it's raining and I'm not going to have shore power available. Since it's only done occasionally, it won't hurt the coach batteries, even though they're different than the chassis battery.

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Originally Posted by Graphite Dave View Post
If you install an inverter powered by the Sprinter 12 volt system you can get 120 volt sine wave power when the engine is running. This allows you to charge the house battery while you are driving. The normal way to charge the house battery is to connect the house battery to the vehicle battery after the engine is running. There are several disadvantages to following the crowd. If you read about the proper way to charge a battery, the consensus is it is better to charge a battery with a 3 stage charger. The 3 stage charger has settings that adapt the charger to the battery. The ideal charge profile for a battery is related to the battery type, the battery size and even the battery manufacturer. When you connect to different size batteries of different types together you can not charge them correctly.
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Old 06-20-2011, 03:45 AM   #9
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Default Re: electrical question

My primary method of charging the house battery is also by a 135 watt solar panel with a Morningstar MPPT controller. I have two secondary ways to charge the house battery with a 1000 watt Magnum inverter/charger/transfer switch. The Magnum can get 120 volt power either from a shore connection or from a 600 watt Xantrex pure sine inverter. The Xantrex gets its 12 volt power from the Sprinter. An isolation relay is installed between the Sprinter battery and the Xantrex to prevent the Xantrex from running if the engine is not running.
The advantage of this arrangement is that the house battery is always charged by a 3 stage charger. The disadvantage is that you waste 30% of the vehicle 12 volt power due to the 85% efficiencies of the Xantrex inverter and the Magnum charger. I figure the 12 volt power is free so I do not care about the efficiency loss.
The cost of this method is about $150.00 more than using the traditional "connect the two batteries" method. Wire cost is about the same, the isolation relay and the ACR relay are similar in cost. The cost of the 600 watt inverter is additional at $150.00. For the extra $150.00 I prefer to always charge the house battery with a 3 stage charger.

Has anyone used a Morningstar MPPT (or equal)controller plugged into one of the vehicle 12 volt receptacles? Seems you could get 3 stage charging with just the charge controller. Why
wouldn't this work? This might be an inexpensive option that would satisfy the original post.
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Old 06-20-2011, 04:32 AM   #10
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Default Re: electrical question

I think you may need a higher input voltage than the alternator can supply. Most solar panels output ~17V, which is then dropped to the correct voltage to charge the battery. If V in is too low, the charge controller may not function correctly.

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Quote:
Originally Posted by Graphite Dave View Post
Has anyone used a Morningstar MPPT (or equal)controller plugged into one of the vehicle 12 volt receptacles? Seems you could get 3 stage charging with just the charge controller. Why
wouldn't this work? This might be an inexpensive option that would satisfy the original post.
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