Upgrading to single lithium battery?

[Raven52]

Our current system is quite simple. A 3 year old group 27 lead acid battery, 100 watt solar panel, Honda 2000 genie, a 500 watt energizer Arc5 solar generator, for Cpap, tv.
Our rig is stationary, off grid, only 20 min. drive from home. We are looking for a better battery as for the last 2 years we would drive to rig often to make sure battery had not depleted more than 50%. Also, the portable solar panel needs to be moved to grab the sun. We use no more than 5 amps daily. Would a single lithium 100ah battery be sufficient for this setup? Also would the charger need to be replaced? Any suggestions would be greatly appreciated.

[PbdBlue]

Originally Posted by Raven52

Our current system is quite simple. A 3 year old group 27 lead acid battery, 100 watt solar panel, Honda 2000 genie, a 500 watt energizer Arc5 solar generator, for Cpap, tv.
Our rig is stationary, off grid, only 20 min. drive from home. We are looking for a better battery as for the last 2 years we would drive to rig often to make sure battery had not depleted more than 50%. Also, the portable solar panel needs to be moved to grab the sun. We use no more than 5 amps daily. Would a single lithium 100ah battery be sufficient for this setup? Also would the charger need to be replaced? Any suggestions would be greatly appreciated.

I would think so. A single 100ah battery is going to double your capacity. In addition the LifePO4 will charge must faster than your current LA battery. You may want to add some more solar. I'm questioning that you use 5 amps daily? That seems extremely low and do you mean amp-hours? How did you measure that?

[Raven52]

Thanks for your reply. I should’ve said that the 5 amps is for the phantom loads when we are not there. When we are at trailer, our amp usage fluctuates between 20-50 amps depending on a variety of usages.

[creativepart]

Why not simply disconnect the battery cables and leave your simple solar setup connected. There will be no draw and the existing battery will be fully charged every time you arrive on site?

[Raven52]

Does the rv propane fridge not require the battery to be hooked up?

[creativepart]

Originally Posted by Raven52

Does the rv propane fridge not require the battery to be hooked up?

It does, if you are leaving the fridge on, then my suggestion isn’t applicable.

And the fridge isn’t a “phantom load” by the way. Just a FYI.

[JHinman]

One battery is enough for a lot of users. I replaced two Group 27 lead acid batteries with one 100AH Battleborne battery, and camped for three days in the summer and drew the battery down about 50%.

I use a disconnect switch, because even the tiny parasitic loads add up over time. My camper is under a roof, so the solar panel does not offset the parasitic loads.

Whether your charger must be replaced or not depends on the charger. I had a Progressive Dynamics charger with Charge Wizard when I bought my Li battery. Instead of replacing the charger I added the Charge Wizard pendant ($19), which allowed me to set the charge rate adequate for the lithium battery. See what options your charger has before you replace it.

Bear in mind that a long run of thin wire will fool your charger. It puts out the voltage needed to charge your battery, but losses may mean your battery never sees that voltage.

I really like my lithium batteries, and I think you will like them also.

[twinboat]

Originally Posted by Raven52

Thanks for your reply. I should’ve said that the 5 amps is for the phantom loads when we are not there. When we are at trailer, our amp usage fluctuates between 20-50 amps depending on a variety of usages.

You draw amps instantaneously, you use Amp Hours or AHs depending on amp draw per hour.

50 amps will kill your battery in 2 hours.

50 AH is a measurement of capacity used over a time period.

[Raven52]

I will certainly look into the charge wizard. I am spending this winter doing the research for a battery upgrade. We live in a snow belt so there is lots of time to plan!

[hclarkx]

5 amps is a lot of phantom loads. Fridge controller, propane detector, CO detector, a couple of 12V USB chargers, space heater thermostat, etc. in my RV total well under 1 amp.

My WFCP 8955 converter would never engage bulk mode after I switched to lithium. The voltage never got low enough to trigger bulk mode. I went with progressive Dynamics.

[treeoflib]

I agree that 5 amps is a lot of phantom load. For our 31 ft FW, our resting load with everything off is 0.8 amps. Our 540w of solar and 260 ah of useable battery easily overcome this.

[Tomahawk]

Originally Posted by hclarkx

5 amps is a lot of phantom loads. Fridge controller, propane detector, CO detector, a couple of 12V USB chargers, space heater thermostat, etc. in my RV total well under 1 amp.

My WFCP 8955 converter would never engage bulk mode after I switched to lithium. The voltage never got low enough to trigger bulk mode. I went with progressive Dynamics.

I am just starting to look into this also. I also have the WFCO WF-8955REP converter. The website says this is compatible with LIPO but eludes to it not being ideal. They sell a special LIPO compatible converter. Reading the manual it looks like it just defaults to 4 hours of 14.6V charging anytime the AC power is disconnected and re-connected. Does that mean the BMS cuts off the charging once he battery is Full? After the 4 hours it drops the voltage to 13.6V.

Back to my current converter. Three stage Bulk (14.4), absorption (13.6) and float (13.2). It only goes into bulk if the voltage drops below some preset value and I think the absorption also switches over at some preset voltage. If I understand it right (big if), the LiPO never gets low enough to trip the bulk charging and probably not the absorption and the 13.6 and 13.2 are too low to charge the LiPO to 100% SOC (or is it too low to charge it at all). Thanks for any education.
I am most curious about the options. Like I think I could leave the converter alone and just get a LIPO charger and never rely on the converter to charge the battery. Not ideal but simple enough. I also have solar that is currently setup as portable, I can configure the MPPT charge controller to charge the LiPO, skip plugging in at home and setup the panel. Ideally, there would be something could be added between the converter and battery to take the converter output and regulate to what the LiPO needs.

[hclarkx]

The four hours of 14.6V is indicated as "absorb" stage, right? Most LiFePo4 batteries do not require time in absorb mode. Some call for 15 minutes, probably to finish balancing, or to get that last quarter percent charge into the battery. Additionally, 14.6V is at the high end of most manufacturers charging spec.

The BMS is not helpful here. The BMS provides several functions but all are simply to protect the battery from damage from errant use. Examples include too high charge voltage (usually 15V or a bit above), charging with the battery too cold (0F or a bit lower), discharging too deeply (11V or thereabouts), etc. None of the BMS functions will protect the battery from something like a too long absorb stage. If you can get the WFCO 8955 into bulk mode and disconnect it when the voltage hits 14.4V or a bit more, that would be okay. Otherwise IMHO it's not very useful for LiFePo4.

The converter that does 14.4V, 13.6V, and 13.2V is a somewhat closer fit, but still not right for the job. Taking the LiFePo4 to 14.4V in the bulk stage is fine. Switching to 13.6 in absorb is fine because this is an ideal float voltage for the LiFePo4. But, when the converter goes to 13.2V, that's below the LiFePo4's full-charge voltage of about 13.3V. In fact at 13.2V the LiFePo4 is down around 50-60% charge. So, this converter won't start covering the loads in float mode until the LiFePo4 is well-down charge-wise. So, not very useful.

13.6V will charge an LiFePo4 but it will take multiple days depending on SOC. Only dumping in as much current as is available until voltage rises to 14.4V can charge in a timely manner. This might be an all-day process with modest solar, but that's fine.

During storage, ideally, you don't want solar or anything else charging the LiFePo4 battery. You want the LiFePo4 down around 50% SOC (about 13.2V) and disconnected. That's not practical in your case since you want to keep the parasitic loads alive.

Assuming your phantom or "parasitic" load is under an amp, it will use roughly 10 Ah overnight. A solar panel will need to replenish that 10 Ah and cover the daytime parasitic load, roughly another 10 Ah. So you'll need about 20 Ah from the panel(s). A 100W panel might be sufficient. It will provide about 5 amps mid-day and less in the off-peak hours. But, it might be a bit marginal, maybe not keeping up through some cloudy days. I'd suggest 200W to have some margin.

If the parasitic load is actually a half amp, 100W would be enough. But, with 200W you will surely have enough and won't need to re-orient the panel(s) more than once a month. You might want to get a better calibration on the parasitic load so you can be sure you have enough panel.

H

[PbdBlue]

Originally Posted by hclarkx

But, when the converter goes to 13.2V, that's below the LiFePo4's full-charge voltage of about 13.3V. In fact at 13.2V the LiFePo4 is down around 50-60% charge. So, this converter won't start covering the loads in float mode until the LiFePo4 is well-down charge-wise. So, not very useful.

H

Why would you want to float at 100% charge level? It's not particularly good for the batteries. I find 13.2V float is 74% charge on my system which IMO is ideal. Battery stays at a very safe charge level and the loads are covered. I've had this setup for over a year and it works great. In fact I store the MH here at the S&B plugged in floating at 13.2V with the solar turned off as the solar will run the batteries up to 100% every day and when storing I don't want that. Solar is set bulk 14.4v and float 13.5V which I use when I'm actually out camping.