Q's about different versions of 100ah LiFePo4 batteries...

[DeniseAck]

Hi All--I have watched a bunch of Will's videos and plan to upgrade my old "Group 24" coach battery to Lithium. He mentions the LiTime brand and I'm totally on board with that and the one he recommends with the low-temp charge cutoff (https://bit.ly/3t4BvsW). But it's a few inches longer and fractionally taller and wider for the compartment it fits in under the floor panel. Does staying with that size really matter? The Group 24 one doesn't have a low-temperature cutoff (https://bit.ly/49Z6aJ2). Should I forget all about the compartment and just plan on using up some storage space? Do many people upgrade to 200ah and then the whole storage compartment issue is moot since they have to be connected? I want to future-proof this as much as possible. I'm not getting solar panels yet, but will at some point. It also mentions this on the Group 24 product page:

【Something You Should Know Before Purchasing】This 12V 100Ah Group24 battery is suitable for energy storage rather than start-up and supports a max. discharge current of 1C. *RECOMMENDATION FOR TROLLING MOTOR: LiTime’s new 12V 100Ah TM battery, is designed for use with all trolling motors.​

 

[Rocketman]

Group 24 size doesn’t matter - does it fit is what matters… can it get shoehorned in?

In an RV you NEED low voltage cutoff that works.

I cannot tell you how much power your RV will use - the biggest factor is the person in it. (The person in my MotorHome has a 544ah 12v battery and keeps wanting to make it bigger). But storage space is precious too. You may need to look at other brands.

Also is the battery basically outside? Do you often spring/fall camp when it will be below freezing? A battery heater may then be a needed accessory.

You need to make sure you have at least one charging source that will charge the lithium battery the way it wants to be charged.

Does your converter have a suitable lithium setting? Many do not, and some will destroy your battery if shore power is left on - most will just undercharge the lithium. An undercharging one will never let the cells get high enough for the bms to balance - so you can have troubles that way. If your converter undercharges then a good solar system is needed very soon.

Also, get a good shunt based battery monitor- I like and use the Victron Smartshunt or BMV712 (there are others).

If you get the Victron shunt get the battery temperature monitor cable and then the shunt can pass the battery temp to a Victron solar charge controller so it will not charge if the temp is too low. (That makes a nice double safeguard).

Good Luck with your project

 

[Rocketman]

Also, I went the DIY route to get as much battery in the space as I could (and could afford). That is also an option- but it will probably cost more.

 

[DeniseAck]

Group 24 size doesn’t matter - does it fit is what matters… can it get shoehorned in?

In an RV you NEED low voltage cutoff that works.

I cannot tell you how much power your RV will use - the biggest factor is the person in it. (The person in my MotorHome has a 544ah 12v battery and keeps wanting to make it bigger). But storage space is precious too. You may need to look at other brands.

Also is the battery basically outside? Do you often spring/fall camp when it will be below freezing? A battery heater may then be a needed accessory.

You need to make sure you have at least one charging source that will charge the lithium battery the way it wants to be charged.

Does your converter have a suitable lithium setting? Many do not, and some will destroy your battery if shore power is left on - most will just undercharge the lithium. An undercharging one will never let the cells get high enough for the bms to balance - so you can have troubles that way. If your converter undercharges then a good solar system is needed very soon.

Also, get a good shunt based battery monitor- I like and use the Victron Smartshunt or BMV712 (there are others).

If you get the Victron shunt get the battery temperature monitor cable and then the shunt can pass the battery temp to a Victron solar charge controller so it will not charge if the temp is too low. (That makes a nice double safeguard).

Good Luck with your project

Thanks Rocketman I will nix the group 24 size since it doesn't have the cutoff. I have a 1997 class B RoadTrek campervan, the battery compartment is a cutout below the underbed storage. So I guess that's basically outside, but I don't really cold camp.

I'm confused with the terminology "converter"-- is that the DC-DC charger? (https://bit.ly/49UHeST). The van has an "isolator" and Tripplite Inverter Charger

 

[12vDC]

you are wise to consider the future proof option of going with a bigger battery now if it will fit in the compartment. One big battery is so much easier to wire and less to worry about regarding balancing.

and yes you either need the battery to cut out from low temp or have a way to keep it warm when you hit freezing temps as you state, and also suggested above.

for those LiTime batteries they come in a 10 inch and 13 inch length which is the difference you are discussing. regarding the trolling motor that specific battery has a BMS which is more robust for that application. you can still use it for your RV. you just have to take into consideration one doesn’t have the low temp cut off.

 

[scrubjaysnest]

FYI a converter is a 120 vac to 12vdc device, most do a poor job of charging lead acid batteries. Many RV makers use group 24 batteries as a cost saver ASSUMING RV's are only used with shore power, 120 vac.
We use AGM's and will see how they fair through the winter with typical lows in the 20's. Left the solar on.

 

[Reed Cole]

For the low temp shut-off, at that price, don't even think about it, just buy them and find somewhere in your RV to put them. They're probably better off in a more temperature controlled location anyways.

 

[Aussieguy]

Converter in RV is a power supply /battery charger that can put out 40amps or more ....... into the 12v electrical system
that way you have enough power to continue using the 12v stuff while the converter also charges the batteries
it is usually located as part of the power center 12v fuse center.
Your converter will more than likely not be lithium capable...
you can add solar OR a small 20amp lithium charger you can turn on to do the final charging/balancing.

solar is a good option especially if you want to go off grid more. and not use generator a lot. look at around 400w of panels and a good mppt 30-40amp as a starter system that can still be upgraded.

Dc-DC can protect your alternator especially if the existing house and starting battery are connected via a BIM and larger cables.
you should disable the BIM so the two batteries are not paralleled if your alternator is not a large capacity type with better cooling fan


IF you don't drive a lot OR use campgrounds that always have 120 hookups you don't need a dc-dc
charge the house when you get to the shorepower.

if you need to parallel for emergency start, then you can simply use a small jumper cable on the BIM ... or reverse the changes you did to it

Lots of options depending on your style of camping.

 

[0truck0]

We need more info on what you plan to run, and for how many days.

Future proof means almost always starting with more than 100 or being set up to have more than 100. Maybe you will not use much battery, and maybe all your trips are a day or two, so 100 will be plenty.

I started with 200, then added another 200. My DC fridge gets a dedicated battery, and the camper gets the other battery. Two separate solar systems, the batts can be connected via a breaker switch, but I have not done so yet. Only the frigde batt is conn to the tow vehicle.

Is interesting that the camper battery gets run down faster than the fridge batt. Running a 0.5 fan all night adds up, I speed fan up to 3 amps during hot days, water pump, kitchen fans, lights, charging devices, running diesel heater rarely- all must be more amps than the fridge (the fridge has a LOT of extra insulation so runs way way way less than normal).

Also future proof it by planning that you will add solar one day.
How much solar depends on how much you will use in a day. If you burn up 50 amp hours a day off the batts, then you gotta replace 50 amp hrs a day with the solar to even out (not needed for short trips). Thats a lot of solar.

 

[Tomthumb62]

Lots of great replies here. I also encourage you to do an “energy audit”, to find out how much power you need per day. Then factor in days that might be low sun (if you go solar) and/or you don’t want to run the van’s engine to change the battery. And I’m not clear- do you have a way to plug in to an electrical outlet to charge the battery? This is what a converter does.

As for where your current battery is, yeah I would remove the battery holder. How big is the space with the holder removed? Height, width and depth.

We have a 200Ah Powerurus battery (has the low temp cutoff) that Will recommends on his website. Their customer service has been awesome answering all my newbie questions, and I’ve had no problems with the battery.

This battery mostly powers a 7.4 cubic foot 120v fridge (not a mini fridge but not full size either). Plus a few 12v items like the water pump, a few LED lights and the fan on the propane heater. This summer we camped for three days in dense forest (no solar charging) off grid, 50F at night, 70F during the day and the battery lasted about 50 hours. It never actually died, the battery reported 2% charge remaining when we got home. There was limited sun for charging on the way home, about a 2 hour drive. So that might give you some idea a 200Ah battery will last in such conditions. The fridge is by far the biggest use of energy and since we were parked in thick shade and the temps were moderate anyways, I expect that if it were hot inside the trailer, such as parked in direct sun or in a hot climate, that 50 hours of runtime might’ve been half that.