58 replies to this topic

[rando]

A DC-DC charger can be used instead of the ACR.   If you currently don't get enough charge current from your alternator, a DC-DC will fix that.   It will also address the issue (although I don't consider it an issue) of the higher lithium resting voltage keeping the ACR combined most of the time, at the expense of loosing solar charging of the truck battery.   

 

I sound like a broken record here, but would go with the Victron DC-DC over either the Redarc or Renogy options.   The two big advantages of the Victron is the configurable output (dial it in for lithium or whatever comes next) and the remote monitoring. 

[rando]

The difference between 13.5 and 13.2V is actually surprisingly little on LiFePO4.   The 13.5V reading is the 'surface charge' on the cells, and no real energy is stored here.   It is kind of like with a lead acid, when you take it off the charges it will sit at 13.xV for a while, but as soon as you load it, it drops to 12.6V.  

 

One of the advantages of lithium chemistries is that the voltage is constant as you discharge the battery.   A consequence of this is that reading the voltage tells you very little about the state of charge:

 

From: https://www.powerstream.com/LLLF.htm

 

 

Note this is for a single cell, multiply by 4 for a 12V battery.   There is only a few % in the drop from 13.6 - 13.2V, and then the voltage only changes by 0.1V over the next 70% of the battery capacity.

 

I think so !

I am always sure of one thing and that is I don't have enough knowledge on the subject. 

The difference between 13.2 and 13.5 is a lot of acvxzperage is it not with LiFePo4 batteries?

Sees to vanish... I wonder if it is not the fact that the DIY draws the Battleborn down. I have to balance 

often as one cell seems to always be the outlier.

Thanks Vic 

[buckland]

I need broken record to get it through to me! Once again thanks also for the graph. Pretty amazing difference. I think I’ll go to the dc dc charger as my ACR does not help much.

[nixfwc]

I just installed a Victron Orion DC-DC charger in my Alaskan, replacing my Blue Sea ACR as I had switched to Battleborn. My Victron version was not the smart version ( blue tooth) and had a potentiometer on the side to set the output voltage. A bit of a pain in the ass as I had to get my alternator to put out over 14 volts to set potentiometer to correct level. I set it at 14.2 volts. The smart versions were  back ordered when I got my Victron. So far it seems to be working out fine. Hopefully it will be a set it and forget it as I have to remove it to get to the potentiometer. Victron makes good products.

[buckland]

Rando 

Can I use the positive wire currently going to the ACR to go to the DC DC charger? 

[Vic Harder]

Blog post on PKYS.com regarding Lithium Batteries - https://shop.pkys.co..._eid=da0f9b5077

[buckland]

Thanks Vic ...I have been reading through ...all good

[smlobx]

 

I sound like a broken record here, but would go with the Victron DC-DC over either the Redarc or Renogy options.   The two big advantages of the Victron is the configurable output (dial it in for lithium or whatever comes next) and the remote monitoring. 

Rando does the Victron model allow a solar input along with the truck battery to charge the house battery? I didn’t see any mention of that.

Edited by smlobx, 25 August 2020 - 10:34 PM.

[rando]

The Victron is alternator charging only.   Generally the DC-DC chargers that support solar don't do a great job of it as the solar is an afterthought and is just repurposing the DC-DC electronics.  As a result they typically don't support series panels, and the MPPT algorithm isn't that good.   I guess it is kind of a free 'bonus' so you can't complain too much.