One Bad Battery

[kbahus]

What do you guys do when when one of your dual batteries takes a dump? I have dual Duracell AGM Group 31's in my camper wired in parallel and was getting prepped for a trip and discovered one of the batteries is bad, practically has no charge and fails load testing. The other battery tests fine. Normally I would run down to the store and pick up and another, but these days a replacement AGM is $300 dollars. I could go with two new lead acid's from the Wal-Mart for $200, or eliminate the dual battery setup and go with a single Amazon LiFePO4 100ah. My pocket book can't handle the hit of either a new AGM or dual Lithium's. I am running all Victron power equipment and solar so adding a LiFePO4 is no problem. Any suggestions?

 

[crazysccrmd]

Lithium all the way unless you routinely camp in cold weather below freezing. A single 100AH lithium gives you as much usable power as the group 31s and weighs significantly less.

 

[kbahus]

I definitely can find myself camping in the cold/freezing a couple times a year. This would be a no go for Lithium batteries?

 

[crazysccrmd]

I definitely can find myself camping in the cold/freezing a couple times a year. This would be a no go for Lithium batteries?

For batteries that are not in a heated area or can self heat it is an issue. Lithiums won’t charge below freezing, most battery management systems will prevent charging to prevent damaging the battery. Self heated batteries work great (I have them) but they are out of the price range you posted.

 

[kbahus]

It would be a definite roll of the dice with weather, but I could run the Lithium and if it gets cold outside switch over to the single AGM. My 12 volt system runs lights, National Luna fridge/freezer, and a water pump so not much demand. The batteries are under the camper so no insulation/heat. Maybe this would be the answer.

 

[Sparse Gray Hackle]

My understanding, which may be faulty, is Lithium’s cold issue is with charging. Some Li batteries have some type of warming built in to enable them to be charged below freezing. You might be able to make it work for you.

 

[Dave in AZ]

Actually an AGM and LFP combo for cold weather isn't a bad option. You need to deal with slightly different voltage to charge. But an AGM can provide heat for the LFP in cold weather. Look at the charge profiles for your AGM, and for an LFP, they are close. My victron ip67 charger has profiles to do both. Worst case, get a Bluesea battery switch that lets you charge them separately, just select the profile desired on the charger. Use the LFP, keep agm topped up and available for cold weather bootstrapping.

There are plenty of 12v powered battery heaters! Even a reptile mat inside an insulated box works well.

 

[crazysccrmd]

My understanding, which may be faulty, is Lithium’s cold issue is with charging. Some Li batteries have some type of warming built in to enable them to be charged below freezing. You might be able to make it work for you.

Yep, only a problem for charging. Mine function fine down to -20°F but do take a while for them to warm themselves up enough the next day to start charging.

 

[rruff]

I definitely can find myself camping in the cold/freezing a couple times a year. This would be a no go for Lithium batteries?

As other's have said, you will ruin a LiFe battery if you charge it at a significant rate when the battery is below freezing. Discharging is fine at much colder temps.

If you will frequently be in much colder temps, it's best to get a battery with a heater built in, and a BMS that will divert incoming charge to the heater until the battery is sufficiently warm. I don't think these are that expensive anymore.

 

[FAW3]

I run our FWC Hawk on one Renology 100ah Lithium battery. Prior set up was two AGM's that just aged out. The single battery now weighs less and provides just as much power at the former set up with a much better voltage profile for voltage sensitive items like the furnace and refrigerator.

Hawk has the factory Zamp 30 solar controller set to L-ion, 160 watt panel on roof and I use a Bluetti PV120 portable solar panel as needed - such as when in shade/winter low sun angle. Normally fully re-charged by 10:00am.

Around 100 nights in the Hawk with this set up. Almost never use shore power, recharge with solar and the vehicle charge system as installed by FWC. Considered doing a dual 100 ah Lithium battery set up but just tried the one and never needed more battery.

The Lithium battery can be USED below freezing...just not charged. Buy one with a BMS. I heat up the camper with the furnace, then charge up in cold conditions.

 

[kbahus]

Great info from everyone, what a rabbit hole these Lithium batteries are. They seem to make sense and if I can get the same or similar performance from a single 100ah as my two AGM's. I don't know why I wouldn't give it a go aside from the cold weather aspect. I need to figure out which one to buy, it seems the brands are constantly changing on Amazon so a lot of the reviews are outdated. Also, what is everyone doing for battery terminals?

@FAW3, what furnace are you using in your Hawk?

 

[Hnoroian]

Where are you batteries stored? If it’s inside you shouldn’t have a problem at all.

Take the small hit in the $$$ lifepo4 all the way because you have the charging capabilities.

 

[FAW3]

The OEM Dometic LP furnace with the short section of flexible air ducting removed just behind the grill.

 

[kbahus]

I wish the batteries were more inside, they are in metal boxes that hang down on either side behind the wheels. Not ideal for a number of reasons, but that is where they put them. There is access from inside the camper, but they are fairly isolated under the floor.

 

[kbahus]

Are there any brands you guys can recommend?