Best way to upgrade existing battery bank

[AJMike]

Sorry for the long post, but there is a lot to explain.

We bought a new (to us) RV about 6 months ago and transferred our 2 100AH BB Lithium batteries to it, along with our DC-DC charger, and all of that is working just fine. The problem is that the new RV, nice as it is, is not very efficient and we find we use a lot more power when dry camping or boondocking, which is what we mostly do. In addition my wife loves to use her electric tea kettle and toaster so often I find our battery down to perhaps 55 or 60% after breakfast. Add to that the fact that the solar, which is maxed out, just doesn't produce all that much power.

I can, of course, run the generator, and that is what I do if I have to, but I much prefer a quiet campsite and want to keep our noise down as much as possible. Given that my thoughts have been moving to increasing the amount of battery power we have.

It seems to me that we have only a few choices. Replace our 2 BB batteries with a 320AH Lithionics, or replace them with 2 130AH batteries, or add some additional BB Lithium batteries. The first Lithionics solution costs a lot at about $4500 plus installation, the second Lithionics solution costs only slightly less at about $3000 and only yields me an additional 60AH so I keep coming back to adding more BB batteries.

The problem is that BB says that you should not mix new Lithium batteries with batteries more than 2 years old and ours are probably about 2 1/2 years old even if they were brand new when installed, which I am not sure was the case. So, here are my questions:

1) How much of an issue would it be mixing 1 or 2 more BB batteries with our existing 2? And why? What is the issue with mixing new and used Lithium batteries?

2) I could look for used BB batteries, but then I would not know how old they were and how they were used. Does it matter how old Lithium batteries were used? Or is used just used? My guess it that it matters how much and how they were used, but I don't really know.

3) Is there a market for used BB Lithium batteries? The final solution that I can see would be to sell my batteries and buy 3 ore 4 new ones, but that would be potentially expensive as I don't know how much used BB Lithium batteries are worth.

Any suggestions as to the best course? I would like to have at least 300AH but 400 would be even better. And yes, I have thought about the issue of charging them, but then I would probably just replace our current 30 amp DC-DC charger with a 40 or 60 amp charger and since we generally only camp at one location for 2 days the power should be enough to charge them on our drive to the next campsite, or home.

[creativepart]

Assuming your current BBs are being fully charged and the BMS is keeping everything balanced it would seem - maybe - that adding two more wouldn't be that big a deal.

I know that adding new batteries to an old battery bank can just make the new batteries as "worn out" as the old batteries, but with Lithium???

I'm sure you could sell your existing batteries, but do you really have to? I know that's the question you are asking. But I'm not sure I'd worry about it.

[creativepart]

Why is the solar maxed out? No room for more panels? Are the existing panels low wattage? Is it a charge controller issue?

Can you change out the existing panels for something more powerful? Can you add a portable suitcase? Is the wiring adequate? Are you losing too much power from long cable runs of too small of a gauge?

[AJMike]

Originally Posted by creativepart

Why is the solar maxed out? No room for more panels? Are the existing panels low wattage? Is it a charge controller issue?

Can you change out the existing panels for something more powerful? Can you add a portable suitcase? Is the wiring adequate? Are you losing too much power from long cable runs of too small of a gauge?

All good questions.

The RV is a B+ and so pretty small. The 4 panels on the roof take up almost all the space available.

More powerful? They are 100 watt panels and I am not sure any other 100 watt panels would produce more power. And given that it is almost Winter I don’t get much sunlight.

The power usage is due to the way the RV is designed. Keeping the propane on uses 2 amps/hour. Turning on the inverter uses another 2 amps/hour. You can’t charge your cell phone without the inverter. And on and on.

The RV is very nice and my wife loves the floor plan, but it was not designed for dry camping or boondocking. It is a shore power type of RV.

I was waiting for the EKKO 24C model and then it was cancelled. Wife saw this one and said that was what she wanted and there was not much I could say in response.

[BobC]

I'd find out more from Battleborn about mixing batteries so you clearly understand the downside. I can't imagine that if 2 year old batteries are OK, mixing in 2.5 year old batteries is going to be catastrophic.

Another alternative is to create a second battery bank and install a switch to change from bank 1 to bank 2. That way you're never mixing your batteries. You might need to get creative with charging.

[DavidM]

Originally Posted by AJMike

All good questions.
The power usage is due to the way the RV is designed. Keeping the propane on uses 2 amps/hour. Turning on the inverter uses another 2 amps/hour. You can’t charge your cell phone without the inverter. And on and on.

I would look at reducing your long term DC loads as follows:

The propane solenoid draws about 1 amp typically and I am surprised by 2 amps. But in any case a capacitor and resistor installed at the switch should reduce that to 0.1-0.2 amps. Google propane on off valve power reduction and you will find articles on this. Basically you install a resistor in series with the switch to drop the current and a capacitor to provide a few milliseconds of boost at full power to pull the solenoid in. Once the solenoid is pulled in, it takes a fraction of the power to keep it in.

Sure you can recharge cell phones, tablets, etc without an inverter. Look for an existing cigarette lighter outlet or even a single USB outlet. Replace he outlet with multiple USBs with the 12V supply. Here is the one I installed in place of a single USB outlet: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1. I use a cigarette lighter plug with two USB outlets to give me 4 USBs.

With this panel cellphones and tablets draw an amp or two while charging but after a couple of hours it drops to a fraction of an amp. Turn off the panel when not in use.

By concentrating on parasitic DC loads you can drop 2 amps for the propane valve and 2 amps for the inverter to about a half an amp. That drops your daily usage from almost 100 amp hours down to maybe 12.

David

[AJMike]

All of those are good ideas, so thank you.

As for charging cell phones and other small electronic devices, I bring along a couple of portable battery banks and use those, not the RV power, when I need to recharge. It allows me to carry the devices around and use them while they are being recharged and it is one less device drawing on the RV power. I mentioned about having to have the inverter on to charge small devices only to explain just how poorly the RV is designed regarding saving power. It is a very nice and comfortable RV, but it is not designed for dry camping.

The main power problem we have has to do with DW's kitchen appliances, and the inverter, while a nuisance drawing 2 amps, is only a minor issue. Given that my wife likes to use the electric tea kettle perhaps 4 or 5 times a day (850 watts), the toaster 2 or 3 times a day (800 watts), the TV and DVD player, electric fans and the like, we easily use 100AH in 24 hours, sometimes more, and in the Winter it is hard to get decent solar charging where we live.

When we returned from our trip (yesterday) I called BattleBorn to ask just how much leeway I had in mixing batteries and was told that the 2 year rule really applies to batteries that have been heavily used and subject to a large number of cycles. When I explained how often we camp (perhaps 60 days/year) and how long we had the batteries he said that he did not see any problem in adding one or two more batteries, so that is what I will probably do.

BB 100AH (no internal heater) batteries have dropped in price again, now down to about $800, so for perhaps $1200 I can add one more battery and have 300AH or for perhaps $2000 I can add two more batteries and have 400AH. That would solve my problem for the foreseeable future. I will have to plan for a larger DC-DC charger, but I already have a 40 amp and a 60 amp sitting around not being used, so I don't see that as a major concern.