Can an inspector tell if lithium batteries are damaged or not?

KayoCan · March 23, 2019

Hello. I found a couple of used class B's I like online. One of them is located in a colder climate (I think that the low temp goes below freezing during winter) and their RV has been in the dealer's lot through the winter . They said that they had been maintaining the unit and that they would give me a 30 day warranty. I read that charging lithium batteries when the temperature is below freezing could permanently damage the batteries. My question is, can an inspector (or anyone) tell if the lithium batteries are damaged or not? I would imagine that it's pretty expensive to replace them.

Thanks in advance!

Kayo

Kirk W · March 23, 2019

There are tests for lithium batteries, but it isn't likely that all RV inspectors know how to test them. Part of the answer would depend on just what was wrong and how bad the damage is. If the RV you are considering has one, I would ask any inspector if he does test them.

KayoCan · March 23, 2019

The dealer says that the RV is in great condition, has been maintained, and nothing is wrong with it. I was just wondering if the lithium batteries could have been damaged since the RV has been there through the winter in a cold weather. I didn't want to find it out later if I were to buy it. I was wondering if the RV inspector could easily find it out before I buy it. The dealer is offering a 30 day warranty, so it seems like I should be okay, though.

Thanks again,

Kayo

Kirk W · March 23, 2019

2 minutes ago, KayoCan said:

The dealer says that the RV is in great condition, has been maintained, and nothing is wrong with it.

Would you expect any salesperson who only makes money if they sell something to say otherwise? The 30-day warranty does lend some credibility to that statement but I would ask them for a written warranty to read completely before you pay any money for it. Warranties very often have exclusions written into them to not cover some of the most expensive and high failure parts. The battery is quite possibly on that list. I suggest that you insist that the 30-day warranty cover every part of the RV. You have told us nothing of the age or mileage it has so we really can't say much about it.

KayoCan · March 23, 2019

Thanks, KirK, for the great advice about the warranty. I haven't made the offer on the RV so I don't want to be too specific about it just yet but the RV is a 2016 model and the lithium batteries came with the unit. It has over 45000 miles on it.

Kayo

Edited March 23, 2019 by KayoCan

Ronbo · March 24, 2019

Most lithium battery packs will have a BMS. If it is wired correctly, it will nit allow charging below a set temp.

KayoCan · March 24, 2019

16 hours ago, Ronbo said:

Most lithium battery packs will have a BMS. If it is wired correctly, it will nit allow charging below a set temp.

That's great to know. Thanks!

Kayo

Al F · March 27, 2019

This will be a outline for general testing, not a specific detailed process. It assumes you are knowledgeable about lithium batteries and the voltage the battery is at full charge and about what the voltage will be when mostly discharged.

The way I test batteries is:

-- First get the battery charged to 100% full

-- Put a constant load on the battery for a set period of time. The idea here is to use a set amount of AH's (amp hours) to take the lithium batteries down to about 20% full (80% discharged) while you monitor the battery voltage.

-- If the RV has an inverter then take an elect space heater and run it off the inverter. Most space heater come as 1500 watts, but usually have a low setting which is probably 750watts. If you have a 2000 watt inverter then use the high setting on the heater.

-- To do this test you really should have a battery monitor like a Trimetric which shows the total AH's used.

-- If you have 200AH of battery, then you would run the heater until about 160AH's if the battery power was used and then check the battery voltage w/o a load on the battery.

-- Lithium batteries have a pretty tight voltage to SOC (State of Charge) curve. A full 12V battery is about 13.3-13.4V. The battery discharged to 20% SOC will about 12.9-12.95V.

-- The key to the test is, if after only discharging about 50% of the AH capacity, the battery voltage is quite a bit lower than what you expect to see, then you probably have a battery which is poor condition.