Hello everyone

[Dr.Ken]

We have been living in our Featherlite coach for about four years now. I have learned a lot. Ours is a 2004 and we have converted lights to LED, re-designed our front cruse-air condensing units, replaced our tank monitoring systems, got rid of the AMX system, and my next thing to tackle are the house battery/inverter system. Has anybody converted to lithium-ion batteries? Any advise?

[Gil_J]

Without a lot of research I would suggest changing a single battery rather than a multi battery system out with Lithium should be easy. Where you may have a challenge with our typical battery arrangement of some number of batteries that have a midtap for 12V that's balanced with an equalizer. The two challenges I see is a need for battery management at each battery and then the impact on an imbalanced battery bank with the use of an equalizer. A lithium aware battery inverter/charger with a built-in battery management is not the sole answer. It may not be sensitive enough to detect a single battery or cell within a battery that needs to be removed from the bank. If it is it will shut down the entire battery bank, which may not be necessary. In the case of a single battery being taken out of the bank through it battery management system the resulting imbalance will potentially cause some real problems with the equalizer. The equalizer concern is easy to resolve, especially if you have changed your interior lighting to LEDs. A DC to DC converter or two can easily replace the equalizer thereby eliminating the midtap in the battery bank.

Your next challenge with changing the inverters is being able to support your Cruisair units through the new inverters. I'll be releasing a video on Microair's Easy Start softstart unit in the next few days. I really like what they do to reduce startup current. You may also have to consider larger or ganged inverters to overcome the startup current issue. I've always thought Victron made some good products. They are somewhat common in the yachting world, but I've only seen them in one coach.

[Dr.Ken]

�� I’m going to have to marinate on that a bit. I have 8 batteries mounted above the passenger side wheel well. I was looking at the batteries with the internal protection systems in them. But there are a lot of things in the mix between the batteries and my two 4K inverters.

[Joe Camper]

Hey Gill that's a clever idea pull the 12 volt loads off the 24 volt battery bank and powering everything DC with an AC to DC converter or two. That's thinking. So in effect when you were running on inverter and you had DC loads being used the power goes from DC, I.E. the battery Bank then it's converted to AC at the inverter and then converted back to DC at the converter and Bam, da lights go on!!!

That would be taking the long way around wouldn't it I love it. Thats efficiency Prevo style.

[Gil_J]

Joe,

DC to DC converters, not AC to DC. Equalizers and the 12V mid tap on the 24V battery bank can be eliminated. Instead a 24V to 12V converter can be used. I believe Victron makes units to 70A. It true, 2 may be necessary.

[Joe Camper]

Never even heard of such a device. Hmmmm. I could use one of those. I have a 24 volt inverter and have to jump through hoops to keep my battery bank equalized because I don't have either an equalizer or dc-to-dc converter. what's the cost on the 2? I was eventually going to have to break down and buy a Vanner I thought. Are the dc-to-dc converters less than a Vanner? I only need one.

[Gil_J]

Joe,

There are different electrical designs and high current styles. Here's the Victron unit I've seen used.
https://www.victronenergy.com/dc-dc-converters/orion-dc-dc-converters-12v-24v-48v-110v

[Joe Camper]

No Gill I do not have one I have a converter that makes AC into DC but I almost never use it anymore because it throws my battery Bank out of balance when I do I only use it very rarely anymore. In the end it's not even going to be on the camper I'm going to eliminate it.

Holy cow Batman I just went to look on Amazon those things are peanuts. I guess there's a reason why they're always not being used instead of a Vanner the cost is so much less what's the deal on that. Why not???

Tru2form there's a hundred different choices they're all over the board, pick me one out Gill. The only DC loads I've got is my water pump and a few miscellaneous 1156 light bulbs here and there. No rope lights yet.

[Gil_J]

Dr. Ken,

I did a little digging and you have a few options for batteries with built-in BMS. That's good news.

To maintain a balanced battery bank in the event a battery takes itself out of service you should built the bank with some number of series connected battery pairs so that each pair is 12V. Then connect these logical 24V batteries into your high current 24V bank. The rationale being that if a battery takes itself out of service it will effectively take out it's partner in the 24V pair. This wiring scheme is none that doesn't realistically support the use of an equalizer. As I said previously, no big deal just use 24V to 12V converters.

When it comes to sizing the bank, the bank should not be less than 500 amps with more being preferred. I recommend using smaller (50A) rather than larger capacity batteries. The rationale being if a battery takes itself out of service and you are using larger capacity batteries you may reduce your remaining capacity below that necessary to support your loads.

Here's the killer. A 600A 24V bank made up of 50A batteries will set you back around $13K. On annual basis that's about $1,300. Some more good news. The 600A bank comes in at a slender 425 pounds. That's a lot lighter than the 900+ to almost 1,300 pounds of most banks found on coaches today.