Renogy Lithium Battery Question

Thanks so much, HarryN. You are the man. I spoke with the guy at Sterling and figured out what battery to battery charger would work (BB1230). I also looked into some options at Lifeline and other forums. Is it fair to say that the combo of a Sterling battery to battery charger and replacing the MB aux battery with 2 6v batteries from Lifeline will help remedy most of my problems?

elemental said:

Put this together, my rough estimate (not calculated, not expert opinion) is that a 100 AH battery with an average 10 amp draw would last maybe 4 hours (before the battery is down to 50% state of charge), and then takes several hours of vehicle operation if you want to repeat the same cycle. This isn't sustainable for multi-day usage even if the vehicle is operated 3 hours a day. Double the storage and reduce the average draw to 5 or so amps to have a sustainable system. If you can't double the storage, reduce the average draw to 2 1/2 amps or so, and avoid peak demands over 5 amps. Add in shore power and/or solar panels for charging if the vehicle isn't going to be operated for several hours each day.

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This is exactly what happened. We didn't have any issues at the beginning of our trip in Moab and the heater lasted through the night. As the kids and my wife realized how nice it was to turn on the lights, wash with hot water and run the heat right before bed, we started upping the avg amp draw. Because my kids are 2 and 4 years-old, we limited our driving.

I had a friend suggest adding an extra 220 alternator. Thoughts?

Kaly said:

This is exactly what happened. We didn't have any issues at the beginning of our trip in Moab and the heater lasted through the night. As the kids and my wife realized how nice it was to turn on the lights, wash with hot water and run the heat right before bed, we started upping the avg amp draw. Because my kids are 2 and 4 years-old, we limited our driving.

I had a friend suggest adding an extra 220 alternator. Thoughts?

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I don't think that the engine-driven power generation is the bottleneck in your system. Based solely on my incomplete understanding of your energy usage profile, it seems more like that your current system has a) insufficient storage and b) insufficient USABLE power generation in your context. I'm going to speculate wildly below; you (or someone you trust) need to perform some actual measurements and calculations in order to match your energy usage profile to a generation/capture and storage system. I suspect that tuning of your usage (i.e., cutting back) will be necessary to get everything to balance within your size and cost constraints.

As previously suggested (MidwestDrifter I think) you would benefit from 110 AH of usable battery storage as opposed to the 50 AH or so that you have now. That could be met with 220 AH of AGM batteries (such as two 6-volt 220 AH AGM golf cart batteries under the hood in place of your existing factory 100 AH battery - there are aftermarket battery trays that achieve this, they might require a change in position/orientation of your ECU if it currently under the factory battery tray). it could also be met with a 170 AH Lithium Ion battery (136 AH usable if you take it down to 20% state of charge), but the Lithium Ion should probably be stored inside your passenger cabin.

However, you need enough usable power generation to fill the storage back up as it is depleted. Batteries have limits on how fast you can charge them (and discharge them). Having an extra 220 amps from the engine through a dedicated alternator doesn't do you any good if you can't shove that energy into the battery quickly enough to capture it while the engine is running. With AGMs, I *think* a reasonable charge rate is something like 10 to 20 amps for a 100 AH battery, 20 to 40 amps for 200 AH. So it would still take on the order of 3 (or more) hours of engine running to charge up your AGM battery storage even if you have an extra 220 amp alternator. Lithium Ions have an advantage over AGMs here because they can accept a higher rate of charge (and if needed, can be discharged more quickly) so you could capture more power from the engine over a shorter period of engine run time. I do not know enough about them to guess at the charge rate/engine run time required with the Lithium Ions.

[If it sounds like I'm pushing Lithium Ion, I'm not, but I'm not arguing against it either. It is attractive because of its benefits, but it has drawbacks such as cost and temperature issues. Tradeoffs...]

Solar PV panels sound like a better fit for you (than a bigger engine alternator) because you don't plan on running the vehicle for hours each day, but the sun is up in the sky for hours each day (less in winter, more in summer, of course). The issue here is having enough panel generation capability to recover each day the energy you use each day. I'm not up enough on usable power generation per 100 watts of solar panels, but my gut is that you might need 300 to 400 (rated) watts of solar to comfortably recover 110 AH of power used. Hopefully someone else can chime in here with a better estimate. You have one 120 watt panel now; perhaps two 120 watt panels would get you close enough, but do you have the roof area to make that happen? If not, can you curtail your power usage to match what you can capture?

Finally, it sounds like you might not have any instrumentation on your power capture/storage/distribution system. That is like driving a car around without a working gas gauge. At a minimum, having a voltage-based state of charge indicator would give you a rough "gas gauge" for your stored electrical power, allowing you to tune your usage. Metering your charge and discharge rates would give you an even better understanding. An overbuilt system might not need instrumentation (just like you wouldn't need a gas gauge on a car that you only drive 50 miles between fill-ups if it got 20 MPG and had a 15 gallon tank) but your needs are a substantial fraction of the capabilities of a reasonably-priced system so having a measurement of your available energy and the rate at which you are using it is important. Unfortunately, good quality instrumentation isn't cheap so it does add to the cost of the system.

If there was a silver bullet for your situation I think someone would have suggested it; there is lots of good information in this thread. However, engineering RV-based electrical capture/storage/usage is a complex challenge once you start trying to make the most of what you can get.

Just so you know my background and can weigh the value of my comments - I'm not an expert; I'm just in the middle of solving this problem for my van and have read/learned a lot from this forum and other sources over the last 6 months. I've got a D2 heater, lights, 2 MaxxAir vent fans, a 130 liter refrigerator (Isotherm Cruise Elegance 12V DC-only), and a few other minor consumers. I don't have the factory aux battery, which I used to think was a drawback but now believe is a blessing in disguise. I'm in the middle of installing 220 AH of AGM storage (two 6-volt golf cart batteries in series) under the hood in an aftermarket battery tray that mounts in the same space as the factory aux battery option. I'm waiting for an Australian-made charging system that I like to go on sale in North America (takes power from solar, the vehicle (using a DC-to-DC charger), and 110 VAC); in the meantime I'm using a Blue Sea Systems ML-ACR (automatic charging relay) to charge the batteries directly off of the vehicle's alternator (similar to the factory aux battery charging). I'm working out some tight spacing for solar panels; I can easily fit three 100 watt panels but want to have four in between my two roof vent fans (I have a 170" so I have more roof area than the 144"). Until I have the solar I'll have to be very careful with my daily power usage; I believe I'll get two or three days sitting still before I have to move to charge up.

Kaly said:

Thanks so much, HarryN. You are the man. I spoke with the guy at Sterling and figured out what battery to battery charger would work (BB1230). I also looked into some options at Lifeline and other forums. Is it fair to say that the combo of a Sterling battery to battery charger and replacing the MB aux battery with 2 6v batteries from Lifeline will help remedy most of my problems?

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Hi, it is Thanksgiving weekend so I will keep this answer short.

No it won't. Look again at the specs for the 2x2 in the link.

Click on the photos and arrows to see the full specs.

RVCuisineScene said:

The set-up has been working great, however each night before hitting the hay I turn off the fridge and have only ran the Espar all night when I had the flu two weeks ago as I drove across the country, most nights I turn the heater off while sleeping and fire it up before I get out of bed. There are pics on my blog at http://kitchenhui.com/road-trip/

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looks like 'only ran espar at night' season is over after 2morow out this way... (up high anyway)

If you have a lot of regular (daily) charging capability, then you might get away with 150 - 200 amp-hrs of AGM.

If you wanting to not think about the charging "every day" concept, then it will take about 400 amp-hrs AGM or equivalent.

I would not go to LiFe unless you are really prepared to take take the time to understand them "before" you go in deep on them.

If lithium is a problem for you because of temperature, FLA batteries will/can have the same issues in freezing temperatures. As they discharge, they become more prone to freezing and the damage that may result. If cold weather camping is more your norm than warm, and lead acid is your choice, stick with AGMs of some sort. Better performance in cold/freezing temps. Another ?

I have a 2008 Winnebago View with 2 x 100 Amp AGM batteries. They are charged by 300 watts of solar through a Victron 100/30 MPPT charge controller. I recently acquired 2 x 100 Amp Renogy LifePO batteries, and wanted to install them. They are compatible with the solar system, but Renogy says my house battery charge converter might damage them. Does anyone have any experience with this? They said the standard converter would be a 4-step charger, and that lithium requires a 2-step charger.

I have read a reviewer online who has successfully used lithiums as direct replacements, but now I am not so sure it is worth it.


Any ideas?

DHH said:

I have a 2008 Winnebago View with 2 x 100 Amp AGM batteries. They are charged by 300 watts of solar through a Victron 100/30 MPPT charge controller. I recently acquired 2 x 100 Amp Renogy LifePO batteries, and wanted to install them. They are compatible with the solar system, but Renogy says my house battery charge converter might damage them. Does anyone have any experience with this? They said the standard converter would be a 4-step charger, and that lithium requires a 2-step charger.

I have read a reviewer online who has successfully used lithiums as direct replacements, but now I am not so sure it is worth it.


Any ideas?

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Besides the float charge in the 4 stage charger, I can't think of why it "might" damage them? Not even sure that that would bother them. The BMS in the Renogy should stop over/under charging by your converter/charger with your compatible solar charger being able to finish the charging job at the higher voltage, as I understand it. I have a similar setup that came with my Navion, a standard smart charger and a Zamp ZS-30A charge controller that has a lithium setting charge algorithm. Battle Born said I'd be fine with that setup. Lithium batteries typically have a built in BMS that protects them from damage of all types, including charge and temperature. At least Battle Born do. I would ask Renogy for a more precise explanation of why they think their batteries won't work for you.

Thanks. I’ll check the documentation with the battery. I was guessing it should work, but wanted to know if anyone else had tried it Have seen it done with batteborn, but not with renogy lithium.

DHH said:

Thanks. I’ll check the documentation with the battery. I was guessing it should work, but wanted to know if anyone else had tried it Have seen it done with batteborn, but not with renogy lithium.

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See post number 15 in this thread. I haven't actually tried it yet. I simply contacted BattleBorn support and gave them the details of my existing charging setup, and they replied that I'd be good to go with their products. I've since read other threads that suggest that BattleBorn lithium BMS systems essentially make them idiot proof.
So, I will be trying them when my current Napa OEMs start to shows signs of failure. They're still fairly new. If they clearly can't keep up with the demands of our rig overnight (we have a Norcold DC only fridge, for example), I may pull the trigger then, but for now, they're fine.
Call or email Renogy and get all the info first, including why they think your converter/charger might damage their product, would be my choice of action. Then decide what might work best for you.