5 replies to this topic

[tbaxter]

We are getting a new truck camper that will come with 2) 6 volt AGM batteries. Would replacing these batteries with a single 12 volt lithium battery be a good move? There is additional cost with the lithium battery. I’m assuming the lithium will actually give me more power (amp hours).

[Charlie]

The capacity of the batteries is given by the Wh value, which is the voltage x Ah. For some reason, batteries are often specified in Ah. So, two 6V 100Ah batteries will be equivalent to one 12V 100Ah battery. And so forth. Pretty easy to calculate.

 

The advantages of lithium are:

 

 - the energy density is approx. twice that of lead acid (AGM) batteries, so you get the same energy capacity for half the weight and half the space. Ot twice the capacity in the same space (but you have to buy two expensive batteries).

 

 - The charge acceptance of lithium batteries is much higher than lead acid. This means that they charge much faster, as long as your charging system can provide enough power to charge them. Thus a solar system with good exposure, or a truck alternator when driving, will charge them quicker. Less sunlight and less driving required to bring them to full charge after a night of camping. This has been the biggest advantage for me when I switched from AGM to lithium. 

 

People will also point out that the number of cycles (i.e. from full charge to low charge) that the battery can take is several times greater for lithium versus AGM. Battery capacity slowly diminishes with number of cycles. Thus lithium will last several times longer than AGM batteries. This means that if you are starting from scratch, the cost difference is a wash over the life of the batteries. But you need to plan on using the batteries for many years for this logic to pay off.

Edited by Charlie, 20 August 2022 - 03:25 AM.

[ckent323]

A lithium battery of the same Ah as the combined 6v AGMs will give you more useable power and less overall weight and less volume (smaller footprint) for more money.

[searching for nowhere]

Disclaimer:  I don't understand electricity, I think it is a bit of a mystery that when I turn a switch a light comes on. 

 

Here is something to think about, or maybe this doesn't apply.  

 

I'm in the middle of ordering a camper van.  I asked if I could use my lithium house batteries to jump start the Mercedes van and I was told no.  Mercedes doesn't allow it because there is a potential for the voltage in the battery to damage the van's electrical system.  But Ford does allow it and has a switch for that use. 

[ckent323]

In general Lithium batteries are not suitable as starting batteries. 

As I understand it, the battery management system in most LiFePO4 batteries will shut down because they sense an overvoltage during the high current discharge of cranking over an engine. 

In addition, a problem may occur if the engine is running as soon as the BMS shuts off or when the battery is disconnected.  An instantaneous spike in your electrical system from the alternator before it catches up with the fact there’s no battery installed, even if it only lasts for a few milliseconds can be detrimental to your computer system your sensors any electrical circuit in your car.

I am not an expert on this so others may want to weigh in.

I think a lithium battery could be used as part of a system to recharge a depleted starting battery but it is my understanding you need a dc to dc charger.

Here is a reference:

https://www.eco-wort...s-start-battery

I hope this is helpful,

 

Craig

[tbaxter]

Thanks to all. I may spring for the single Lithium battery up front. This will be for a new truck camper my wife and I are looking to buy with solar.

Edited by tbaxter, 21 August 2022 - 10:04 PM.