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 > Lithium and DC-DC Charger?

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Ramblin' Ralph

Central California Coast

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Posted: 01/07/21 08:03pm Link  |  Quote  |  Print  |  Notify Moderator

My two group 27 lead acid batteries need replacing. Even though I'm too old to get maximum benefit from lithium longevity, I am thinking about going with a single 100 AH LifePO4 lithium. Doing some research it appears that a DC - DC charger is needed between the truck alternator and camper battery to protect the alternator. Would this still be required with only one 100 AH battery? Truck is a 2006 GMC 2500HD. Also have 125w of solar.

Thanks,
Ralph


Ralph
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pianotuna

Regina, SK, Canada

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Posted: 01/07/21 11:04pm Link  |  Quote  |  Print  |  Notify Moderator

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. No need for a special converter. No worries about going to 0 volts.


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.

time2roll

Southern California

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Posted: 01/07/21 11:17pm Link  |  Quote  |  Print  |  Notify Moderator

The fuse will open or the wire will melt before the alternator sustains any damage.
Assumes you are using the OEM charge connection.


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NRALIFR

Truck Camping Out West

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Posted: 01/08/21 05:52am Link  |  Quote  |  Print  |  Notify Moderator

I don’t get that “protect the alternator” advice at all. Assuming you were going to connect the Li battery directly to the alternator, wouldn’t you also install a fuse or CB to protect it?

But, the more important point is that if you are going to put the money into a lithium battery, a DC-DC charger will charge that battery better than connecting it to the alternator anyway. The DC charger will be connected to the starting batteries, and will just be another electrical load on the system. In fact, if SiO2’s are the drop in replacements they claim to be, a DC-DC charger (with a solar input in Ralph’s case) would be the best way to recharge them as well.

Even in a TC, the charging circuit to the camper batteries is surprisingly long, and while you can minimize the voltage drop, you can’t eliminate it. Install a DC-DC charger with adequately sized wires and forget about voltage drop entirely.

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ticki2

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Posted: 01/08/21 06:20am Link  |  Quote  |  Print  |  Notify Moderator

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 ?


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jaycocreek

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Posted: 01/08/21 06:24am 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. No need for a special converter. No worries about going to 0 volts.


The problem I have is that when you ad shipping on the site you linked,the price is right there with the less expensive lifepo4 batteries...Some of the cheapie lithium batteries are not bad at all as shown by Will P...SOC comes to mind.


1994 F-350 DRW /460/k&n intake /415# torque/lance 9.6/Engel compressor fridge/3 gr 27 batteries/Honda 2k/Honda 3K/WH Camo 2250/Reese solid bar extension/Buddy heater/3 inverters//Happi Jack tie downs /Firestone bags/Yamaha Rhino/Winch and Lockers

srschang

Western NY

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Posted: 01/08/21 06:49am 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 ?


The voltage curve on a lithium battery is way different then a lead acid. The lead acid voltage drops steadily as the charge is depleted. The lithium voltage stays virtually level throughout the discharge, then drops off a cliff when the battery is near completely discharged. That's why a volt meter works well on a lead acid battery to measure the charge, but on a lithium a voltage measurement won't help determine state of charge.

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* This post was edited 01/08/21 06:58am by srschang *


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toddb

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

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. This will keep the voltage stable as you don't want the BMS to disconnect on over or under voltage from the alt.

NRALIFR

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Posted: 01/08/21 09:30am Link  |  Quote  |  Print  |  Notify Moderator

Todd, just out of curiosity what size DC-DC charger were you able to run using the factory wiring? I know that’s typically called a 30 amp circuit, but I kinda doubt it can do 30 amps for long. Even a small DC charger could out perform solar though, unless you have a really big system.

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toddb

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Posted: 01/08/21 09:42am Link  |  Quote  |  Print  |  Notify Moderator

I use a victron 12/12 9, I think it's 120W so about the equivalent of 1 panel. The truck may be 10ga, hard to tell but I think in the camper and umbilical were 12 so this model is plenty safe. I get 7-7.5A out of it at 14.6V.

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