2 100 ah lithiums

[wireright]

I have one 100ah lithium battery in my rv. I have a 200 watt solar and mppt controller plus the lithium charger from my rv inverter. If I buy another lithium battery would there be any issue feeding each battery to a switch that selected one or the other rather than parallelling mismatched batteries? I would have the capacity but could only charge them separately with that configuration

 

[pollenface]

I don't see an issue with paralleling, unless you want redundancy.

 

[wireright]

I've been told by manufacturers that they do not suggest paralleling batteries unless they are the same age and manufacturer. The new battery will not be the same manufacturer.

 

[TampaSteve]

Yes you are correct you shouldn't parallel different batteries. Battleborns recommends the same battery up to 2 years old is ok

Of course your switch idea is fine. That's what boaters did for decades.

 

[rmaddy]

Will recently did a video showing his setup with different brand and different capacity batteries in parallel.

Bottom line seems to be that it is just fine, especially if you have low C rates via solar.

 

[MisterSandals]

would there be any issue feeding each battery to a switch that selected one or the other r

The potential problem i see is that the battery is what powers your SCC and removing power, especially when receiving solar power, is thought to be "suboptimal".

I would strongly consider a switch that connects from 1, to both, and then to the 2nd battery (and vice versa).

 

[RCinFLA]

The primary issue you have to be careful of when paralleling batteries is exceeding charge or discharge current on individual battery.

You can get one BMS shutdown while other remains active so one battery has to take the load or charge current.

If your load or charging is okay for lowest individual AH battery than it is okay for the two in parallel.

 

[Mike Mas]

You can do it either way however - You might be better off charging all the batteries together to keep the batteries cell voltages the same for voltage and amperage discharging.

Mike

 

[Bubba1]

Put a switch or breaker between solar panels and charge controller. Turn panels off before switching from one battery to the other then turn panels back on.

 

[mikefitz]

The batteries will give the longest service life if operating in the 20% to 80% where the voltage is between 13.0 and 13.3 volts. It will be easier to do this with the batteries connected continually in parallel, they will both be working is a low stress region. With a single battery in operation at any time it will suffer from higher charging and discharge stress.

Mike

 

[wireright]

I will have to read more and watch Will's videos. I thought it might work to parallel them but the batteries won't have the exact same specs and one will be older than the other. I can monitor them when connected separately to not go below 20 percent but normally charge to 100 percent each time. Thanks for any more information.

 

[MisterSandals]

I thought it might work to parallel them but the batteries won't have the exact same specs and one will be older than the other.

So what are your 2 batteries? Is it a secret?

 

[wireright]

No secret . I have a lifeblue 100ah with less than 20 cycles but haven't purchased the second battery yet. I'm looking at the Chin's or amperetime (same thing) They are so cheap now but don't want to damage my lifeblue by charging both at the same time. Does it make a difference that by charging with the converter in the rv I can push 30 or 40 amps into the batteries . Do I need to be concerned that the bms in the 2 batteries may not have the same parameters?

 

[MisterSandals]

Do I need to be concerned that the bms in the 2 batteries may not have the same parameters?

Since the BMS is a safety cutoff switch, its of most concern if you plan on operating at the extremes of the safety limits. As mentioned earlier, a conservative charge/discharge plan (at first at least) will probably be just fine. The capacity similarities and internal resistances of the 2 batteries will be what it comes down to. You can buy a similarly rated capacity battery but the IR is kind of a crapshoot unless you can get your current battery and one you purchase measured (pretty much unheard of, to me anyway).