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Charging Choice


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#21 ClimberRob

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Posted 12 September 2019 - 03:55 AM

In all these scenarios, wouldn't the same current be flowing through the positive wire to the camper battery, and therefore be protected by the circuit breakers on that wire?  The only reason you would need a separate breaker on the negative would be in the case where you could have an (excessive) current flowing on the negative wire which is not also flowing on the positive wire.  I can't think of any scenarios where this would be the case.

 

Not trying to be argumentative here, but trying to make sure we are giving good advice.    A breaker on the negative for a dual battery is not something I have ever run across before, so I want to make sure it actually serves a purpose and that I am not missing something. 

 

It's OK if you don't get it. "We" are not giving advice. I'm giving my advice, and you're giving yours. You are, indeed, being argumentative. Stating that you're "not trying to be" doesn't have any effect on that. That's OK, too. 


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#22 ClimberRob

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Posted 12 September 2019 - 03:59 AM

 

 

A lead- acid battery's internal resistance will self limit the max actual charge rate. They're not super-capacitors. No knowledge if you're using one of the more advanced chemistry batteries.

 

Unfortunately, that's not how it works. You will fry a FLA battery by pushing too many amps into it.


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#23 ntsqd

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Posted 12 September 2019 - 01:10 PM

That's odd because that is what I was taught, repeatedly, in Auto Repair classes.


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#24 docalex

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Posted 12 September 2019 - 02:51 PM

I am no expert .....

I recently installed renogy 40 amp dc to dc charger.

I butchered a pair of 4awg jumper cables to run wire from the truck to the charger and battery in my truck bed next to my camper. There is a 50 amp inline fuse and cut off switch under the hood. The charger needs another 12 volt signal that activates  a built in relay switch to turn the unit on. I wired a switch into the cab of my truck. I have a battery monitor installed on my system. Now please understand I JUST installed this system, so this is not advice coming from experience. The system, when turned on, charges the battery at 40 amps then ramps down to 20 and finally a 2 amp trickle... It seems to work well and fast.

 

My only regret is that I did not buy the 20 amp model... I recently acquired  a lifepo4 battery that can only take 20 amps max. Looking for a solution ...

 

here is a link to video from my "lectric" Guru

 

 

Ps...

 

 

I installed this battery monitor... I cant imagine running my system without it.  


Edited by docalex, 12 September 2019 - 02:52 PM.

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#25 JaSAn

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Posted 12 September 2019 - 03:46 PM

Unfortunately, that's not how it works. You will fry a FLA battery by pushing too many amps into it.

 

That is how my 2 GC2s (6V FLA) work.  

 

I charge with a 35 amp adjustable battery charger (adjustable voltage).  My depleted batteries will accept max current as the voltage climbs to set voltage (for my batteries = 14.3V), then amps drop until battery will not take any more (~ 2 amp = 100% charged).

 

If the voltage is set too high (higher than manufacturers recommended bulk charge rate) I will boil my batteries and loose fluid quickly.

At the correct or lower voltage it would take months to loose enough fluid to damage the batteries.

 

Batteries are 5 Y.O. and still going strong.


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#26 Vic Harder

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Posted 12 September 2019 - 03:49 PM

Unfortunately, that's not how it works. You will fry a FLA battery by pushing too many amps into it.


i think my Rolls batteries in my previous camper could accept a 1C charge rate. they were 275AH. i don’t think many alternators are likely to fry FLA batteries
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#27 alano

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Posted 12 September 2019 - 09:21 PM

Update on my charging choice (re-hijacking my thread :)): I used 4 AWG welding wire and shortened the path from about 30 feet to just under 15 feet. Went with the Renogy 40amp DC/DC charger. On test drive after letting camper batteries get down to 12.3 volts with no load (lost the percent of full charge when rewiring the battery box I managed to trip the breaker) I got over 30 amps for a bit but then it settled to 24 amps as the voltage rose to something over 13.

 

Probably would have been happy with the 20amp DC/DC charger and saved some coin. Sooner or later really low batteries and a short driving day will make this one pay off I suspect. I used a low voltage protection circuit https://www.amazon.c...0?ie=UTF8&psc=1 to control the DC/DC converter so as to provide the same sort of extra protection to the truck battery that an isolator gives. I need to tune turn on and off voltages a little as things were bouncing early in the test drive. I also ran a control wire from the ignition back through the trolling motor connector in case this protection circuit proves problematic.

 

I considered a manual switch, but I am terrified that I would forget to turn it off without some sort alarm or knock on the head.

 

Thanks to all who offered advice. Pulling wire for the truck only took an hour or so although wiring up the battery box and securing everything back there took much longer. I had to take the camper off the truck to install the trolling motor connector, but a friend wanted to move a bed this past weekend so I had extra incentive to be a good friend and get the project going.

 

Alan


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#28 Vic Harder

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Posted 12 September 2019 - 10:44 PM

sounds like a good fit for you!
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Power considerations thread - https://www.wanderth...e-power-scotty/

 


#29 ClimberRob

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Posted 13 September 2019 - 12:08 AM

That's odd because that is what I was taught, repeatedly, in Auto Repair classes.

 

Batteries are specced with a max charge current. As Vic stated below you, many batteries can accept a 1C charge. That's not the same as self-regulating. For a 275AH battery, as in Vic's, or your, example, with a 1C charge rate, it's unlikely to be an issue. If someone hooks up a 35AH battery to their big diesel truck alternator, it's very likely to be a problem.

 

That is how my 2 GC2s (6V FLA) work.  

 

I charge with a 35 amp adjustable battery charger (adjustable voltage).  My depleted batteries will accept max current as the voltage climbs to set voltage (for my batteries = 14.3V), then amps drop until battery will not take any more (~ 2 amp = 100% charged).

 

If the voltage is set too high (higher than manufacturers recommended bulk charge rate) I will boil my batteries and loose fluid quickly.

At the correct or lower voltage it would take months to loose enough fluid to damage the batteries.

 

Batteries are 5 Y.O. and still going strong.

 

A 35 amp charger is charging those batteries very gently.


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#30 ClimberRob

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Posted 13 September 2019 - 12:08 AM

Update on my charging choice (re-hijacking my thread :)): I used 4 AWG welding wire and shortened the path from about 30 feet to just under 15 feet. Went with the Renogy 40amp DC/DC charger. On test drive after letting camper batteries get down to 12.3 volts with no load (lost the percent of full charge when rewiring the battery box I managed to trip the breaker) I got over 30 amps for a bit but then it settled to 24 amps as the voltage rose to something over 13.

 

Probably would have been happy with the 20amp DC/DC charger and saved some coin. Sooner or later really low batteries and a short driving day will make this one pay off I suspect. I used a low voltage protection circuit https://www.amazon.c...0?ie=UTF8&psc=1 to control the DC/DC converter so as to provide the same sort of extra protection to the truck battery that an isolator gives. I need to tune turn on and off voltages a little as things were bouncing early in the test drive. I also ran a control wire from the ignition back through the trolling motor connector in case this protection circuit proves problematic.

 

I considered a manual switch, but I am terrified that I would forget to turn it off without some sort alarm or knock on the head.

 

Thanks to all who offered advice. Pulling wire for the truck only took an hour or so although wiring up the battery box and securing everything back there took much longer. I had to take the camper off the truck to install the trolling motor connector, but a friend wanted to move a bed this past weekend so I had extra incentive to be a good friend and get the project going.

 

Alan

 

Nice!


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