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Open Roads Forum  >  Truck Campers

 > Lithium and DC-DC Charger?

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Ramblin' Ralph

Central California Coast

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Posted: 01/08/21 11:37am Link  |  Quote  |  Print  |  Notify Moderator

Thanks for the input. My “protect the alternator” question was because of the following video I saw from Victron. Evidently the lithiums can put a higher amp load on the alternator. In their lab study one of them started smoking because of insufficient cooling while charging a 300 AH lithium.
Video here

I was just checking to see if I might have the same problem with a single 100 AH. Thanks for the tip on the SiO2 batteries. I'll look into them.

Ralph


Ralph
2006 GMC 2500HD, XCab, SB, 6.0L w/2001 Lance 845
Bilstein Shocks, TorkLift Stable Loads, 125 watt solar
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time2roll

Southern California

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Posted: 01/08/21 11:45am Link  |  Quote  |  Print  |  Notify Moderator

Ramblin' Ralph wrote:

Thanks for the input. My “protect the alternator” question was because of the following video I saw from Victron. Evidently the lithiums can put a higher amp load on the alternator. In their lab study one of them started smoking because of insufficient cooling while charging a 300 AH lithium.
Video here

I was just checking to see if I might have the same problem with a single 100 AH. Thanks for the tip on the SiO2 batteries. I'll look into them.

Ralph
Not just the size of the battery but the size and length of the wire connecting the battery. I speculate the boat had relatively fat and short wire to reduce voltage drop to the previous lead acid batteries.


2001 F150 SuperCrew
2006 Keystone Springdale 249FWBHLS
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theoldwizard1

SE MI

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Posted: 01/08/21 12:15pm Link  |  Quote  |  Print  |  Notify Moderator

Ramblin' Ralph wrote:

I am thinking about going with a single 100 AH LifePO4 lithium.

The size of your RC battery bank depends on how much power you draw and for how long. Your pair of Group 2y batteries and deliver about 160 Ah. Is 100 Ah going to be adequate ? Only you know the answer.

Ramblin' Ralph wrote:

Doing some research it appears that a DC - DC charger is needed between the truck alternator and camper battery to protect the alternator.

Not exactly true. A DC-DC chargers does two jobs. It PROPERLY FULLY CHARGES your RV battery while you are driving and it isolates the RV from the engine starting battery so that the RV battery can not be drained by the vehicle (some DC-DC chargers have a temporary bypass to emergency engine starting).

Ramblin' Ralph wrote:

Also have 125w of solar.

If your solar is working well, my guess is one 100Ah lithium battery would be adequate.

* This post was edited 01/08/21 12:42pm by theoldwizard1 *

theoldwizard1

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Posted: 01/08/21 12:19pm Link  |  Quote  |  Print  |  Notify Moderator

pianotuna wrote:

Hi,

Try SiO2 100 amp-hours for about 50% of the cost.

https://azimuthsolarproducts.com/product/12v-100ah-sio2-battery/

No need for a dc to dc charger.

I don't understand how you can say that ! Straight from the product page

Azimuth Solar Products wrote:

Settings for your SiO2 battery if you are choosing custom programming on your charge controller:
Equalizing Voltage -> 14.6 or Shut off this function if available
Boost Voltage -> 14.6
Floating Charge Voltage -> 13.6

You will likely NEVER be able to achieve those voltages without a DC-DC charger !

* This post was edited 01/08/21 12:41pm by theoldwizard1 *

theoldwizard1

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Posted: 01/08/21 12:20pm Link  |  Quote  |  Print  |  Notify Moderator

duplicate

* This post was edited 01/08/21 12:41pm by theoldwizard1 *

theoldwizard1

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Posted: 01/08/21 12:23pm Link  |  Quote  |  Print  |  Notify Moderator

ticki2 wrote:

This is probably a dumb question , forgive my ignorance . I have been reading about these new technology batteries , lithium and now Sio2 that can be discharged to 80 and 100 percent . How do they power equipment that requires 12v to operate like a furnace sail switch , at this state of DOD ?

It depends on the equipment.

Most inverters will shutdown somewhere between 10V and 11V. Things like light (both incandescent and LED) will keep running below 10V. USB Chargers ?

theoldwizard1

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Posted: 01/08/21 12:40pm Link  |  Quote  |  Print  |  Notify Moderator

toddb wrote:

I went without vehicle charging for when I switched over, I only used solar. No problems until the fridge upgrade.
I use a small one now on factory wiring and would recommend it if you want vehicle charging.

Interesting point you bring up.

First, everyone needs to understand that DC compressor refrigerators actually have an inverter inside. They will shutdown at some pre-determined minimum voltage. You need to verify that yours will automatically restart.

Second, of your goal is to MAINTAIN your battery bank voltage, NOT RE-CHARGE a depleted bank, then you probably do not nee a DC-DC charger. Simply connecting you RVs battery to the starting battery connection at your 7 way, is probably adequate !

ONE EXCEPTION ! If you are running a 120VAC refrigerator from an inverter, will your inverter automatically re-start after a temporary low voltage event or do you have to press a button/flip a switch ? If YES, you want a DC-DC charger (because it will maintain proper battery voltage at all times the engine is running).

pianotuna

Regina, SK, Canada

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Posted: 01/08/21 02:28pm Link  |  Quote  |  Print  |  Notify Moderator

ticki2 wrote:

This is probably a dumb question , forgive my ignorance . I have been reading about these new technology batteries , lithium and now Sio2 that can be discharged to 80 and 100 percent . How do they power equipment that requires 12v to operate like a furnace sail switch , at this state of DOD ?


BFL13 has iirc run a microwave from an inverter powered by a single 100 amp-hour SiO2 at 20% state of charge. The sail switch would be a tiny load compared to that.


Regards, Don
My ride is a 28 foot Class C, 256 watts solar, soon to have SiO2 batteries, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

Tiger4x4RV

Inland Empire, Southern California

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Posted: 01/08/21 04:04pm Link  |  Quote  |  Print  |  Notify Moderator

I like to think that I belong to the "if it ain't broke, don't fix it" school of RV tech. That makes me wonder what your issue really is.

Have your power needs changed? If no, you might just consider putting in new batteries of the same type you have. If existing batteries are not AGM maybe upgrade to those if their physical size allows them to fit where the old batteries are now.

Maybe you just want a project? OK. That beats COVID boredom.

Wanting to try the newest trend? OK. No shame in that.

Want to add charging from the engine? My 2006 GM truck has an isolator under the hood to keep the coach batteries from drawing down on the engine battery when the engine is off. The engine alternator (heavy duty) and shore power are my only two choices of power for charging the coach batteries. I rarely have shore power and the engine has done the job just fine since 2006. Yes, the Tiger is not a TC and is not demountable like your Lance, but there is undoubtedly a way to hook an isolator (I think they may be called separators now) into your system.

Happy trails whichever path you choose!


2006 Tiger CX 4x4, 8.1 L gas V-8, Allison 6-speed


DiploStrat

Arlington VA

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Posted: 01/08/21 04:27pm Link  |  Quote  |  Print  |  Notify Moderator

Some comments on lithium (iron) and battery to battery chargers (B2B).

Lithium iron batteries will take a LOT of current. As a test, at a battery manufacturer's shop, I connected a fully discharged, 100Ah lithium iron battery directly to my Chevrolet based Tiger. Drew 100A and, more to the point, kept up that high draw for nearly an hour. Never see charge rates like that with AGM. With a 250A alternator, I was probably safe as I normally use about 125Ah over night, but imagine the draw of a 300Ah battery bank after two days of rain.

B2B first became popular for charging deep cycle lead acid batteries on vehicles whose alternators were set to 13.9v. (E.g. many Toyota, Mercedes, etc.) Most B2B were relatively low amp (i.e. 20-30A) devices, but because they had proper charging voltages of over 14v, they worked much better.

Most American pickups already have charging circuits that run at over 14v, so their utility was limited. But with the new Euro standard and other energy saving circuits, they are experiencing a renaissance.

For lithium they can be ideal as, assuming the proper profile, they can provide the correct voltage and, since they cannot draw more than a certain amount of current (typically 10-20% above their rated output) they can prevent an overload of the factory alternator.

Hope this is useful.



DiploStrat

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1990 Mercedes Benz 917/XPCamper

Website: https://diplostrat.net/



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