A different Lithium question?

[AJMike]

I currently have 3 BB 100AH Lithium batteries and almost 600 watts of solar with a 30 amp Victron MPPT controller and a 30 amp Victron DC-DC charger. This gives us enough power for all of our dry camping trips except one. That trip is to the NM mountains where there is a lot of foliage and we can only get about 90 minutes of good solar a day and where we can not run our generator as it is against the rules.

Our current batteries are now 5 years old and when I asked BB about adding another 100AH battery they said that doing so would immediately drop the new battery to the power levels of the existing parallel connected batteries. I know this, but I don't know what that really means in practical terms. How much power do my batteries still provide? And how do you measure that in the real world? And why would adding a 4th battery not still give me 33% more power? And would doing that damage the existing batteries? Or the new one? These are questions I don't know the answer to.

We make about 15 trips a year, most of them 2-3 nights and about 80-90% of those trips dry camping, although only about 50% of the yearly nights are dry camping as we make some longer trips in the summer when it is too hot to dry camp. My wife loves to use her electric tea kettle, toaster and microwave and that combined with the overhead of the coach means about 25% battery usage per day. So how low would the max power of our batteries have likely dropped in the last 5 years? And why would adding a new battery be a problem?

The alternative is to replace all of them and I don't really want to spend the $3000-$4000 if I don't really need to.

[Tony Ramirez]

I'm not sure about the "Actual" effects of adding old to new, everybody says don't do it. But if you end up deciding to replace the whole battery bank, there are A LOT of less expensive than options Battle Born. BB's are overpriced in my opinion.

I went w Epoch Essentials line, couldn't be happier.

[MRUSA14]

Originally Posted by AJMike

I currently have 3 BB 100AH Lithium batteries and almost 600 watts of solar with a 30 amp Victron MPPT controller and a 30 amp Victron DC-DC charger. This gives us enough power for all of our dry camping trips except one. That trip is to the NM mountains where there is a lot of foliage and we can only get about 90 minutes of good solar a day and where we can not run our generator as it is against the rules.

Our current batteries are now 5 years old and when I asked BB about adding another 100AH battery they said that doing so would immediately drop the new battery to the power levels of the existing parallel connected batteries. I know this, but I don't know what that really means in practical terms. How much power do my batteries still provide? And how do you measure that in the real world? And why would adding a 4th battery not still give me 33% more power? And would doing that damage the existing batteries? Or the new one? These are questions I don't know the answer to.

We make about 15 trips a year, most of them 2-3 nights and about 80-90% of those trips dry camping, although only about 50% of the yearly nights are dry camping as we make some longer trips in the summer when it is too hot to dry camp. My wife loves to use her electric tea kettle, toaster and microwave and that combined with the overhead of the coach means about 25% battery usage per day. So how low would the max power of our batteries have likely dropped in the last 5 years? And why would adding a new battery be a problem?

The alternative is to replace all of them and I don't really want to spend the $3000-$4000 if I don't really need to.

Prices have come way down. 4 new batteries should cost less than half of what you stated.

[SafariBen]

Originally Posted by AJMike

...Our current batteries are now 5 years old and when I asked BB about adding another 100AH battery they said that doing so would immediately drop the new battery to the power levels of the existing parallel connected batteries...

\


I'm not a battery engineer, but I don't know of any reason for that to be true, and a few reasons that is not true. I suspect you were not talking to the head of engineering, but a salesperson. The engineering dept does not make their scripts, the marketing dept does.


There are many valid reasons not to add new batteries to an old string. Specifically, a new battery or cell in an old SERIES string, WILL immediately drop to the capacity of the other cells or batteries, but will be unaffected in storage, that is, not charging or discharging.


In a parallel string, the voltages will match, and the amperages will add up. So most issues will be in storage or very slow charge/discharge. Combining a 300ah battery parallel with a 50ah of the same chemistry, while moderate charging or discharging will be FINE. Issues with lead would be in storage, I don't know what the potential would be with Li in storage, and I won't suggest disconnecting them because reconnecting them is not the same as lead.



To determine the capacity of your current batteries, put a known load on them and time the discharge. Might be that they are just as good as new, your usage has just crept up over time.

[MtCamper]

You can get a pair of 200 amp batteries from Redodo for about $800. Mine work great. Or you could add a 100 amp one for under $200. Or you could stay as is and learn how to limit your power consumption. Propane actually can be used to boil water, make toast and cook food.

[AJMike]

Originally Posted by Tony Ramirez

I'm not sure about the "Actual" effects of adding old to new, everybody says don't do it. But if you end up deciding to replace the whole battery bank, there are A LOT of less expensive than options Battle Born. BB's are overpriced in my opinion.

I went w Epoch Essentials line, couldn't be happier.

Yes.

When I spoke with the local installer to get estimates I mentioned that although I currently had BB batteries I was not "wedded" to them and would be happy to consider other options if I replaced all the batteries. I even asked about a couple of those really big batteries, 250-270AH each, in a pair.

[AJMike]

Originally Posted by SafariBen

\


I'm not a battery engineer, but I don't know of any reason for that to be true, and a few reasons that is not true. I suspect you were not talking to the head of engineering, but a salesperson. The engineering dept does not make their scripts, the marketing dept does.


There are many valid reasons not to add new batteries to an old string. Specifically, a new battery or cell in an old SERIES string, WILL immediately drop to the capacity of the other cells or batteries, but will be unaffected in storage, that is, not charging or discharging.


In a parallel string, the voltages will match, and the amperages will add up. So most issues will be in storage or very slow charge/discharge. Combining a 300ah battery parallel with a 50ah of the same chemistry, while moderate charging or discharging will be FINE. Issues with lead would be in storage, I don't know what the potential would be with Li in storage, and I won't suggest disconnecting them because reconnecting them is not the same as lead.



To determine the capacity of your current batteries, put a known load on them and time the discharge. Might be that they are just as good as new, your usage has just crept up over time.

The current batteries are connected in parallel and I would not add another single battery unless it was the same voltage. The existing ones are 12.8 volts and 100AH, as would be any replacement.

[AJMike]

Originally Posted by MtCamper

Propane actually can be used to boil water, make toast and cook food.

I have mentioned that to my wife, but she really likes using the electric appliances.

[Itinerant1]

Add another BB to the mix and be done with it.

By your stated use of 25% DOD. Going to high side of 15 trips x 3 day == 45 x 5 years or 225 or so days of 25% DOD. That's nothing in lfp lifespan/ use.

I'm at 3,100 days of using a 500ah lfp bank using 120v appliances everday at all levels of SOC including the air conditioner. The inverter has never been turned off.

[jimfishes]

Originally Posted by Tony Ramirez

But if you end up deciding to replace the whole battery bank, there are A LOT of less expensive than options Battle Born. BB's are overpriced in my opinion.

I went w Epoch Essentials line, couldn't be happier.

I have two 460ah Epoch Essentials. They’re gr8. Keep an eye on their website as they frequently have sales.

[chopity]

The simple way to try and understand mixing old and new batteries is that they will absorb energy at different rates. The older batteries will have an assumed higher resistance so they will absorb at a slightly higher voltage than the newer battery. Its not ideal, its also not going to explode. Options:

1. Add another cheap battery in parallel. (it doesnt have to be 100ah)
2. Buy a stand alone power bank and use that for items like the electric kettle. Can also use at home during a power outage.
3. Boil water and cook with propane when youre at the tree shaded campsite.

In terms of how much power your batteries still have? Comes down to usage, charging level and storage level. Its not good to store your batteries fully charged in a warm climate. Your solar charge controller is very programmable. Dont feel overwhelmed. First thing i would do is make sure its not fully charging every morning in storage.

[AJMike]

Originally Posted by Itinerant1

Add another BB to the mix and be done with it.
.

That is certainly the least expensive option, and my preferred one. But my question is whether or not mixing old and new batteries is really a problem. And if so, exactly what is the problem.

Part of me says that even if it lowers the lifetime of the battery pack and I have to replace all of them in 2 or 3 years I would still be ahead because lithium battery prices are probably going to continue to fall and the cost of one additional battery is not that high. I just don't want to damage any of the appliances in the RV or cause serious electrical issues in the RV components.

[AJMike]

Originally Posted by chopity

The simple way to try and understand mixing old and new batteries is that they will absorb energy at different rates. The older batteries will have an assumed higher resistance so they will absorb at a slightly higher voltage than the newer battery. Its not ideal, its also not going to explode. Options:

1. Add another cheap battery in parallel. (it doesnt have to be 100ah)
2. Buy a stand alone power bank and use that for items like the electric kettle. Can also use at home during a power outage.
3. Boil water and cook with propane when youre at the tree shaded campsite.

In terms of how much power your batteries still have? Comes down to usage, charging level and storage level. It's not good to store your batteries fully charged in a warm climate. Your solar charge controller is very programmable. Dont feel overwhelmed. First thing i would do is make sure it's not fully charging every morning in storage.

The RV is in covered storage so any solar charging is minimal. Still, there is no easy way for me to disconnect the batteries from the solar charging system because the battery disconnect does not do that. I think I would have to manually disconnect the wires to stop the (small) solar charge.

I live in southern Arizona so "warm" weather is about 9 months a year.

[chopity]

Originally Posted by AJMike

The RV is in covered storage so any solar charging is minimal. Still, there is no easy way for me to disconnect the batteries from the solar charging system because the battery disconnect does not do that. I think I would have to manually disconnect the wires to stop the (small) solar charge.

I live in southern Arizona so "warm" weather is about 9 months a year.

Oh yeah man next time at storage reprogram your SCC so that it lets the batteries just sit there and self discharge to a certain level until solar charges again. You can also limit the voltage it charges to.

I would search youtube videos or read the manual or make a thread asking for a cliff note version of programming the SCC so its not keeping the batteries fully charged out in AZ. Its no bueno in hot climate.