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DanDweller

Charging Coach Battery with Alternator

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Hello all, I am about to convert my TC 2015 XL for vandwelling and am looking at how to charge the 100ah lithium iron phosphate battery I plan on getting to power vent fan and lights.  In addition to solar panels, I also want the option to charge from the alternator.  What I learned from talking to a technician at Renogy (who makes the battery I'm going to buy) is that with an MPPT DC to DC charger, it will control both options.  But the one they sell draws 50 amps from the alternator and he advised me to find out if my alternator can handle the additional draw.  (Of course, calling Ford and Ford dealers has proved to be useless--as always, on any question.)  It is this one:

https://www.google.com/amp/s/www.renogy.com/amp/dcc50s-12v-50a-dc-dc-on-board-battery-charger-with-mppt/

 

I bet this is probably too much draw, but I don't really understand these things so well.  Can someone help me out here, or recommend another brand which has a similar DC to DC battery charger with MPPT but which draws less amps from the alternator (how many would be safe?), allowing to charge via alternator or solar panels?

Also, I understand from our conversation that I would also need an inverter charger to be able to connect to shore power, but the one Renogy sells is 2000 watts--more than I think I will need. (The inverter I would use to charge my electric shaver and use a laptop every now and then--not much at all).  Is there another brand someone could recommend, and that is for lithium iron phosphate batteries?

Thank you!

Edited by DanDweller

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I believe that the Transit Connect alternator is about 150 amps.  Or something like that.  Use a battery isolator.  

 

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I use an ArkPak 730 with my Battle Born 100Ah 12V LiFePO4 Deep Cycle Battery. It works great, but not inexpensive.

 

AP730_1024x1024_1fd2df61-9633-4889-ab7a-66707afa3a2a.thumb.jpg.0f16efbd1b174f5dcb1f913516498d0f.jpg

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11 hours ago, Fifty150 said:

I believe that the Transit Connect alternator is about 150 amps.  Or something like that.  Use a battery isolator.  

 

Battery isolators are definitely yesterdays technology  -  They use diodes which introduce a voltage drop so your aux battery never gets a full charge  -  The fact that they are mounted in a huge aluminum heat sink is a clue  -  The voltage drop creates lots of HEAT which must be dissipated somehow

 

A voltage controlled relay is a much better choice.   The relay senses the voltage at the input and when it rises above a certain level, indicating that a charge voltage is present, it closes the relay and connects the aux battery with no voltage drop . . . . and no heat.   A Blue Sea Systems ACR (Automatic Charging Relay) is a good choice.  Their model 7601 can handle 65 amps, so it should be good for the OP's installation.  You can get one from Amazon for less than $60

 

Don

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I guess I'm more confused now.  So does the wiring coming from the alternator-relay not go to a MPPT controller?  How does this interface with the solar charge controller?  I thought from prior conversations in a different forum that I needed to use a DC to DC charger to protect the alternator.  

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4 hours ago, Beta Don said:

A voltage controlled relay is a much better choice.   The relay senses the voltage at the input and when it rises above a certain level, indicating that a charge voltage is present, it closes the relay and connects the aux battery with no voltage drop . . . . and no heat.   A Blue Sea Systems ACR (Automatic Charging Relay) is a good choice.  Their model 7601 can handle 65 amps, so it should be good for the OP's installation.  You can get one from Amazon for less than $60

 

Don

 

A voltage sensing relay wont work with a MPPT charger, at least it didnt when I connected it with my setup because the charger did not show any voltage at the at the relay on the house side of the relay so the voltage sensing relay never turned on.  I had a Blue Sea Systems ACR and Bogart Engineering charger and battery monitor.  

 

I ended up using a 60 or 100 amp relay with an on delay timer set to a minute or two connected to an ignition on signal

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17 hours ago, DanDweller said:

Hello all, I am about to convert my TC 2015 XL for vandwelling and am looking at how to charge the 100ah lithium iron phosphate battery I plan on getting to power vent fan and lights.  In addition to solar panels, I also want the option to charge from the alternator.  What I learned from talking to a technician at Renogy (who makes the battery I'm going to buy) is that with an MPPT DC to DC charger, it will control both options.  But the one they sell draws 50 amps from the alternator and he advised me to find out if my alternator can handle the additional draw.  (Of course, calling Ford and Ford dealers has proved to be useless--as always, on any question.)  It is this one:

https://www.google.com/amp/s/www.renogy.com/amp/dcc50s-12v-50a-dc-dc-on-board-battery-charger-with-mppt/

 

I bet this is probably too much draw, but I don't really understand these things so well.  Can someone help me out here, or recommend another brand which has a similar DC to DC battery charger with MPPT but which draws less amps from the alternator (how many would be safe?), allowing to charge via alternator or solar panels?

Also, I understand from our conversation that I would also need an inverter charger to be able to connect to shore power, but the one Renogy sells is 2000 watts--more than I think I will need. (The inverter I would use to charge my electric shaver and use a laptop every now and then--not much at all).  Is there another brand someone could recommend, and that is for lithium iron phosphate batteries?

Thank you!

 

100ah lithium should be more than enough for small loads like lights, a power vent and a laptop.  With a solar panel you will probably have enough power to keep it charged.  

 

But if you do decide to charge from the alternator dont worry about the alternator capacity to much because if the lithium battery draws to much it will just take what it cant get from the vehicle battery and eventually charge everything to full anyway.  Just make sure you use adequate cable, you will need 6 or 4 awg wire to carry the current

 

It might be a better option it get a laptop charger that can be powered from 12vdc that way you wont have to deal with the losses of an inverter, also get a battery powered shaver that you can recharge occasionally because depending on what type of shaver you might need a true sine wave inverter for it to work anyway.

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1 hour ago, dinocarsfast said:

 

A voltage sensing relay wont work with a MPPT charger, at least it didnt when I connected it with my setup because the charger did not show any voltage at the at the relay on the house side of the relay so the voltage sensing relay never turned on.  I had a Blue Sea Systems ACR and Bogart Engineering charger and battery monitor.  

 

Your solar panels, controller and house battery bank should be wired up as normal  -  Connected together all the time.  The voltage sensing terminal of the relay would be attached to the van's starting battery, so when the alternator raises that battery's voltage up to 13 or so, the relay closes and adds alternator power to your solar controller.  Engine not running, the solar works as normal, Engine running, it adds in the alternator power to charge your house batteries

 

Don

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7 hours ago, Beta Don said:

 

Your solar panels, controller and house battery bank should be wired up as normal  -  Connected together all the time.  The voltage sensing terminal of the relay would be attached to the van's starting battery, so when the alternator raises that battery's voltage up to 13 or so, the relay closes and adds alternator power to your solar controller.  Engine not running, the solar works as normal, Engine running, it adds in the alternator power to charge your house batteries

 

Don

 

I dont have a solar panel, only charging from the alternator, and I thought it would work the way that you describe also but when the engine is off the charger did not allow the house battery voltage to get through to the voltage sensing relay.  So then I found that the voltage sensing relay would not close when the engine was on because it did not sense a voltage on the house battery side, maybe some sort of safety feature.  

 

IDK if this is the situation with all solar chargers not allowing voltage to the voltage sensing relay side or if having a solar panel connected will change the situation even when their is no sun but I had to get a relay and an on-delay-timer and my setup works 

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7 hours ago, Beta Don said:

 

Your solar panels, controller and house battery bank should be wired up as normal  -  Connected together all the time.  The voltage sensing terminal of the relay would be attached to the van's starting battery, so when the alternator raises that battery's voltage up to 13 or so, the relay closes and adds alternator power to your solar controller.  Engine not running, the solar works as normal, Engine running, it adds in the alternator power to charge your house batteries

 

Don

 

Now Im thinking you meant to connect the vehicle charging system to the ACR and then directly to the house battery, this would have worked but I didnt think it would be good enough for me because of the voltage drop in the lines to the house battery and the loss of charge capacity because of the lower voltage.  I connected the two batteries through a charger so that it could step up the voltage so that it would fully charge.  I also used a Lead Acid battery for my house battery. 

 

Back to the original post, I think the MPPT charger that was in the link would be a great option it is a "multi-Input charger" so you can connect the charger directly to the vehicle battery or alternator and it will not discharge the vehicle battery when the engine is not running so no need for a voltage sensing relay since it has an internal voltage sensing relay

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If you are satisfied with only partially charging that LiFePO4 battery (about 70% max), then go ahead and use the direct-connection charger methods talked about above. But, I assume you want it fully charged, so you'll need the proper MPPT DC-DC charger that is designed for lithium batteries. Lithium-based batteries charge very differently than old school SLA/AGM style batteries - which vehicle alternators are designed for. It's not as simple as "give it power to charge and it's good" when it comes to those batteries. As the saying goes "Anything worth doing, is worth doing right." 

 

Quote

Can I recharge my lithium battery from my vehicle alternator? – Yes, but not necessarily to full charge, due to the fact that most Alternators are adjusted for the lower voltage requirements of the vehicle Lead/Acid Battery (approximately 13.9-Volts).  Lithium Batteries require 14.4 to 14.6-Volts to fully charge.  That being said, you can get up to approximately a 70% charge, depending on the depth of discharge and distance driven while recharging from your vehicle alternator.

 

https://www.progressivedyn.com/frequently-asked-questions-on-converting-to-lithium-charging/ 

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8 hours ago, dinocarsfast said:

 

Now Im thinking you meant to connect the vehicle charging system to the ACR and then directly to the house battery, this would have worked but I didnt think it would be good enough for me because of the voltage drop in the lines to the house battery and the loss of charge capacity because of the lower voltage.  I connected the two batteries through a charger so that it could step up the voltage so that it would fully charge.  I also used a Lead Acid battery for my house battery. 

 

Back to the original post, I think the MPPT charger that was in the link would be a great option it is a "multi-Input charger" so you can connect the charger directly to the vehicle battery or alternator and it will not discharge the vehicle battery when the engine is not running so no need for a voltage sensing relay since it has an internal voltage sensing relay

So then back to the question of whether the 50A capacity will put too much strain on the alternator (or impact fuel economy)?

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On 10/10/2019 at 9:53 PM, DanDweller said:

So then back to the question of whether the 50A capacity will put too much strain on the alternator (or impact fuel economy)?

 

I think it would be fine but it would probably depend on things like like how you use the system, will you drain the battery fully down or is it only going to be topping it off, do you live in a hot area.

 

But if you burn the alternator out because its to high of a load you can always put a higher capacity alternator in.

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These work well and will handle the power with no voltage drop.

image.png

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