Dual Battery Question

[EricG]

Consider a roof or ground-deployed solar panel kit as an adjunct to extend your power capacity. You'll get ~~5A out of a panel and could combine with a max-fit flooded battery for about the price of an Odyssey AGM alone. And it will be power supplied when the fridge is using the most.

Thats what I wasnt sure of is the solar charging while the fridge was running.

 

[rayra]

Thats what I wasnt sure of is the solar charging while the fridge was running.

how so? The solar charge controller will pass the power and work to top up the battery it is connected to. I think the only case where it won't is with the engine running and your alternator providing a voltage level that the solar controller would interpret as 'battery is full'. Vehicle off, no other charge on the battery and any othe rloads on it, batter depleting, solar controller sees the voltage drop and applies juice at whatever rate it thinks is appropriate.

/grossly speaking, and on the low budget end of things. No idea how fancy the latest and greatest controllers are.

 

[Axlesup]

i have a 70 watt snow master fridge and it will deplete a 12v 70 ah AGM in about 2 days depending on temp and use. while my 60 AH 24v lithium ion pack will run it for a week easily. now that i have a 200 watt panel on the roof of my rig it never gets below 26 volts even after a couple of days of rain.

 

[BigSwede]

If you are just running a day or two I'm not sure dual batteries are worth the cost and weight and complexity. My Odyssey grp 34 runs my Engel fine for a day, can't even tell it is run down at all. You can always carry a little lithium jump starter as backup.

 

[Mil T]

Ditto what Big Swede said. My starting battery is an odyssey and keeps everything working fine. I did run a new #4 battery positive wire from the battery to the back of my jeep to a dedicated power port for the refrigerator in the back. I also have a 150 watt cigarette lighter inverter that runs the refer or whatever also. I've never run out of battery. I do carry a 1500 ma jumper incase I do run low. Works great.

 

[WSS]

i have a 70 watt snow master fridge and it will deplete a 12v 70 ah AGM in about 2 days depending on temp and use. while my 60 AH 24v lithium ion pack will run it for a week easily. now that i have a 200 watt panel on the roof of my rig it never gets below 26 volts even after a couple of days of rain.

So, the lifpo4 packs really do charge quicker /easier? Or is there another reason the lifepo4 batts are more efficient?

 

[BigSwede]

Different chemistry. One of the biggest differences is that a LiPO4 battery can be drawn down 80% or more without significant damage compared to 50% for lead acid, and recharged many times (10x?) more than lead acid before degradation becomes a problem. Plus they are much lighter/smaller.

 

[dreadlocks]

Any lead battery Fully Discharged (50% SOC) will take 7-8h to recharge at full rate.. A fully discharged LFP battery takes ~2.5h to recharge at its fastest "safe" rate, but it'll take more than that and charge even quicker if u give it enough power.

The biggest difference for Overlanding/Boondocking, is a LFP Battery will take full charge current all the way til its full.. A Lead battery spends most of the time absorbing a very tiny current.. When your primary charge source is Solar you getta stuff all the electrons you can gather into the LFP, with the Lead most of it is being wasted if your generating more power than the battery wants.. the efficiency gains are incredible with this in account.