Adding a 4th Renogy 100ah smart battery later down the track in parrallel, do they have to all be new?

[Mousie]

Hi Folks, first post and have been reading wide so as to upgrade my caravan as ready to change from AGM to Lithium Batts. Currently 720w Solar through MPPT lithium ready ( currently 12v AGM's), 60a AC to DC Lithium ready chager. I do have a quality Mean well 3000w inverter 12 to 240v that I picked up at the right price. Usage is the occasional Hair Dryer, Microwave as the heavy items and rest is normal low to medium power stuff.

Now the Renogy smart 100ah Lithium Batts have the balancing interconnect links and price is sharp so can I just buy 3 and put in now. Then later if I actually need more capacity then just buy the same type again and put in to make a 4th in parallel. I was thinking if the Renogy technology is linked and provides a balancing function between then say in theory 3 are one year old and then I add a new one, would anyone see an issue with this approach. I have space for 3 and if I need to can rework to fit a 4th.

 

[Wjm1964]

This from renogy website -

• DO NOT string the battery in series. It is made ONLY for 12V parallel connections using the batteries of the same manufacturer and model.
• Please avoid too high a voltage difference between paralleled batteries, despite the auto-balancing function, to avoid triggering the over-current protection.

So as long as the voltage range is close (nominal is 12.8v & voltage range is 10v - 14.8) i don't see any issue as voltage stays the same, but Ah goes up.

 

[Bobert]

Hi Folks, first post and have been reading wide so as to upgrade my caravan as ready to change from AGM to Lithium Batts. Currently 720w Solar through MPPT lithium ready ( currently 12v AGM's), 60a AC to DC Lithium ready chager. I do have a quality Mean well 3000w inverter 12 to 240v that I picked up at the right price. Usage is the occasional Hair Dryer, Microwave as the heavy items and rest is normal low to medium power stuff.

Now the Renogy smart 100ah Lithium Batts have the balancing interconnect links and price is sharp so can I just buy 3 and put in now. Then later if I actually need more capacity then just buy the same type again and put in to make a 4th in parallel. I was thinking if the Renogy technology is linked and provides a balancing function between then say in theory 3 are one year old and then I add a new one, would anyone see an issue with this approach. I have space for 3 and if I need to can rework to fit a 4th.

It is not unusual for people to add additional lifepo4 batteries later. You just need to make sure the batteries are at the same state of charge before connecting them together and that the batteries are identical.

 

[Mousie]

Thanks for this and another question. If I parallel 4 then they auto-balance but if I have 5 in parallel, I take it the fifth just does it own thing in charging up. Surprisingly Renogy say up to 4 recommended, yet in Australia they are advertising as "unlimited parallel' connections (ebay au). I take it so long as I have my AC charger setup properly, just run the 5 without harm? Or has anyone linked more than 4 batts on the network side of things. I'm thinking the DC home may be the limiting factor here. Long shot but I thought I would ask.

 

[Bobert]

Assuming that they are properly wired the tendency for batteries in parallel to balance each other is the same no matter how many are in parallel. If I understand correctly the issue is if the bms can handle the additional amperage should something short out on one of the batteries. The paralleling of batteries keeps the voltage the same and increases the number of amp hours available and The batteries I use tend to have bms failure if they are in a greater than 4p arraignment. If your batteries say up to 4 parallel I doubt the manufacture will honor their warranty. I would suggest that you contact them before going with a 5p arrangement.