Adding 2nd rv 12v lithium battery

[jefMort]

I want to add a 2nd 12v lithium battery to my RV. I sent the following email below to ExpertPower (content abbreviated) asking opininion about adding to barely used 12v lithium battery bought last July. Any comments?
Ok Brian, thanks for the update and prompt response. You said " If the battery was left on the charger and remained charged, while also being continuously charged from its self-discharge, then the battery cells would’ve been continuously stimulated and have most likely degraded a bit."

The ExpertPower battery was connected only to shore power and once fully charged last July was never unplugged from shore power until October. That means that my RV drew any power through its shore power connection.

Then in October I disconnected the battery and brought it into my basement. Any self- discharge was minimal. In actual fact of usage it was connected, all the time to shore power, for 3 months. Your website states a second battery should be added within six months. I seriously doubt my first battery has anywhere close to six months of activity on it. It was not plugged in while in the basement storage.

Jef

On Tue, Jun 15, 2021, 2:20 PM Bryan <support@expertpower.us> wrote:

Hey, Jef

Thanks for reaching out to us. We would not recommend it. If the battery was left on the charger and remained charged, while also being continuously charged from its self-discharge, then the battery cells would’ve been continuously stimulated and have most likely degraded a bit. I would estimate that you’d run into issues within the first two years of use with a second battery.

Bryan
ExpertPower


Sent: Tuesday, June 15, 2021 9:56 AM
To: support@expertpower.us
Subject: Adding Second 100amp 12v in series to RV

I bought an expert power 100amp battery in July 2020. I connected it to my upgraded RV converter and fully charged it using shore power. The battery never depleted, It was always connected to shore power until October sitting in my back yard. I did not use my RV last year. I pulled the Battery in October and stored it in my basement for the winter. I pulled it from the basement yesterday and hooked it up to my RV for the 1st time this year. Shore power is running to my RV and the battery.

I now want to add a second expertpower 100 amp RV battery in series. Can I expect any issues? I read that another battery should be added within six months but I have basically not run the first battery on it's own with load so far. What do you think? Will my total available maps decrease?

Jef

 

[Bob142]

I want to add a 2nd 12v lithium battery to my RV. I sent the following email below to ExpertPower (content abbreviated) asking opininion about adding to barely used 12v lithium battery bought last July. Any comments?
Ok Brian, thanks for the update and prompt response. You said " If the battery was left on the charger and remained charged, while also being continuously charged from its self-discharge, then the battery cells would’ve been continuously stimulated and have most likely degraded a bit."

The ExpertPower battery was connected only to shore power and once fully charged last July was never unplugged from shore power until October. That means that my RV drew any power through its shore power connection.

Then in October I disconnected the battery and brought it into my basement. Any self- discharge was minimal. In actual fact of usage it was connected, all the time to shore power, for 3 months. Your website states a second battery should be added within six months. I seriously doubt my first battery has anywhere close to six months of activity on it. It was not plugged in while in the basement storage.

Jef

On Tue, Jun 15, 2021, 2:20 PM Bryan <support@expertpower.us> wrote:

Welcome!

Add the second battery and don't look back!

If we go with Bryan's assumption that there's been some degradation (capacity loss) in your original battery:

• Your battery bank will be limited by the capacity of the weakest battery (presumably your original one).
• Well, your current bank (of one battery) is limited to its capacity. So 100Ah or fewer. Let's pretend it's now 95Ah.
• Adding a second battery in parallel means you will have 2x95Ah = 190Ah. 190Ah is a lot more than 95Ah!
• The second battery in parallel shares the load. So your original battery won't have to work as hard as it does now unless you plan to double your load (adding more devices?)

I can't see a downside to adding another battery in parallel. Especially given it's the same battery model, so presumably it has the same BMS as your original. It can't get much more compatible.

Just remember to wire it up with the positive and negative connections going to a different battery. That way each battery will supply the same current under load. (It is uneven if you connect positive and negatives to the same battery. See the FAQ)