12v system voltage tolerance and lithium/lead-acid differences

Dipodomys

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I'm probably overthinking this, but...

I'm planning to convert a camper's batteries from lead-acid to lithium. I've read many of the related threads, and haven't seen much discussion of one aspect that comes to my mind. That is, I understand that 12v systems generally have a tolerance for voltage deviation around 10%, i.e. they do fine with about 11-13v. However, I also understand that LiFePO4 batteries have a resting voltage when full around 13.6v and when full and when charging around 14.4v, a full 20% higher than the nominal system voltage. Does this have consequences for connected 12v systems?

My naive assumption is that it depends on the system in question. For example, led lights might glow just a little brighter and burn out just a little quicker, but maybe not enough to notice. However, sensitive electronic devices plugged into USB outlets might have problems if the USB outlet voltage is 20% higher than the 5v +/- 5% standard. Of course there are countless other use cases, some of which involve voltage conversions, some inversions, and some direct usage of battery voltage. So my question is really, are there common use cases that are problematic for using a lithium battery without a regulated 12v output? If so, then what equipment is available for regulating output and what sort of efficiency losses does it suffer?

Note: I'm kind of assuming that the absence of discussion of this issue here and on other web sites suggests that it isn't really an issue in practice. So maybe this is all academic.
 
Conventional battery alternators operate from around 10 v to 14.4 v. as a result most devices used in 12 v systems are fine between 9 v and 15 v. Voltage regulators for conventional systems are designed to accept 9 v to 14.4 v.

A conventional lead acid battery provides about 12.7 v to 12.8 v when fully charged. A lithium ion battery (depending on BMS setting) provides 13.2 v to 13.6 v when fully charged.

The operating range of most vehicle 12 v accessories falls within the output range of both types of batteries.

If you have an expensive item it would be wise to check the specs or with the manufacturer before connecting it.


https://battlebornbatteries.com/battery-voltage-explained/


I hope this is helpful,

Craig
 
ckent323 said:
Conventional battery alternators operate from around 10 v to 14.4 v. as a result most devices used in 12 v systems are fine between 9 v and 15 v. Voltage regulators for conventional systems are designed to accept 9 v to 14.4 v.

A conventional lead acid battery provides about 12.7 v to 12.8 v when fully charged. A lithium ion battery (depending on BMS setting) provides 13.2 v to 13.6 v when fully charged.

The operating range of most vehicle 12 v accessories falls within the output range of both types of batteries.

If you have an expensive item it would be wise to check the specs or with the manufacturer before connecting it.


https://battlebornbatteries.com/battery-voltage-explained/


I hope this is helpful,

Craig
Very helpful. Thanks!
 
Interesting question - good response from Craig. Wait until you start really figuring out the differences/implications for charging your camper’s battery (if you haven’t already). That is something important you will need to understand before making the switch to LiFePO4 batteries. Many people on this forum have been through the process of converting and there is good advice here and helpful people.
 
Humble Road has reported MaxxAir Fans having a problem with higher voltage. I use a Phillips BiPAP ASV and I get a voltage error when hooked to my Lithium, using the 12v plug/cord. I put in a 12v regulator and still got an error. Called Phillips and was told it needs around 13v. I am now using a small inverter and not my 2000w inverter.

I did switch from AGM to Lithium. 540 Ah of Battleborn. My solar and inverter/charger had setting for Lithium. I did add two 30 amp DC-DC Victron chargers to protect my smart alternator on the Ford Transit.
 
I converted to lithium a couple of years ago and have no regrets. I use my solar panels and Victron charge controller to charge my batteries.

In my experience the voltage problem usually happens the other way around from what the original poster mentions. My built-in original equipment WFCO Converter does not put out high enough voltage to completely charge the lithium batts. If I ever need to charge from shore power I'll need to upgrade that converter/load panel. Its a relatively inexpensive upgrade if you have a little electrical knowledge. I haven't done it because I mostly boondock and have not shore power anyway.
 

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