Adding batteries

[wiseacre]

A little information is a dangerous thing and I know next to nothing.

I do know you can NOT add new batteries to a lead based bank. I assumed it also went for LiFePo4 batteries but after hours of reading the forum it appears that you can add new lithium batteries to build up a battery bank as long as the batteries match. For simplicity sake, adding a new battery of the same make and model would be OK?

As background I have an Eco Worthy (1k) kit.

• 6 pcs 195W Solar Panel
• 1 pc 3.5KW Inverter with Cable
• 1 pc 60A PMW Charge Controller
• 2 pcs 100AH Gel Battery
• I added a Eco combiner box and a Moes ATS set to switch at 24V (I think that's good for not over discharging the batteries below 50%)

The "battery box" is very well insulated with 2 inch foam and I've had no "known" problems with charging below 0 degree F.

As much as I would like to build my own LiFePo4 batteries I don't have the confidence to actually do it. I almost bought some Chin batteries but after seeing the reviews here I am not. Will's review of the SOK batteries sold me on them. (the low temp charge cut off is the cat's pajamas for my location in cold white north)

SO, basically I'm asking if I can add new SOK batteries as I can afford them.

 

[HRTKD]

A little information is a dangerous thing and I know next to nothing.

I do know you can NOT add new batteries to a lead based bank. I assumed it also went for LiFePo4 batteries but after hours of reading the forum it appears that you can add new lithium batteries to build up a battery bank as long as the batteries match. For simplicity sake, adding a new battery of the same make and model would be OK?

As background I have an Eco Worthy (1k) kit.

• 6 pcs 195W Solar Panel
• 1 pc 3.5KW Inverter with Cable
• 1 pc 60A PMW Charge Controller
• 2 pcs 100AH Gel Battery
• I added a Eco combiner box and a Moes ATS set to switch at 24V (I think that's good for not over discharging the batteries below 50%)

The "battery box" is very well insulated with 2 inch foam and I've had no "known" problems with charging below 0 degree F.

As much as I would like to build my own LiFePo4 batteries I don't have the confidence to actually do it. I almost bought some Chin batteries but after seeing the reviews here I am not. Will's review of the SOK batteries sold me on them. (the low temp charge cut off is the cat's pajamas for my location in cold white north)

SO, basically I'm asking if I can add new SOK batteries as I can afford them.

Do you mean charging below 32° F? That's the general cutoff for charging LiFePO4 cells. If you don't have adequate low temperature cutoff then an aftermarket warming system may be in order. The solar charge controller should know what the temperature of the battery is and stop charging below 32° F. The BMS is your last line of defense for low temperature.

 

[wiseacre]

No, I know better than to attempt charging below freezing.
I'd move the setup to my basement where freezing is not an issue although it would take some doing. (wife wouldn't let me put any type of lead acid in the house but she's OK with the LiFePo4).

A warming system is not as sure proof as moving them to a steady 60 F (15 C) location. Is there any down side to that temp?

What I want to do is expand my battery capacity. I'll have to ditch the Gel batteries since I assume you should not add new batteries to old ones. I may have misunderstood some of what I've read but it seems that adding new LiFePO4 to an existing bank is possible. At this moment I'm thinking (2) SOK 12v 206 batteries in series would greatly improve the capacity the pair of gel 100ah I'm now using considering the depletion levels of the 2 types besides the ah increase.

The $$$ building a battery bank all at once is beyond my means. If I could add new LiFePo4 batteries to an existing bank that is more doable. If it's possible I'll have more questions (12v vs 24v batteries) (series and parallel configuration limitations)

 

[HRTKD]

A warming system is not as sure proof as moving them to a steady 60 F (15 C) location. Is there any down side to that temp?

That is a good temperature for LiFePO4. Moving them into a predictable, 60° F location is always better than a warming system.

I only know what I read about adding LiFePO4 to a non-LiFePO4 battery bank. It works, but isn't ideal due to different charge profiles. One of them will end up less than happy.

 

[wiseacre]

I'll be getting rid of the Gel batteries. They'll become trolling motor batteries for my son-in-law. The battery bank for solar will be strictly the same battery.

What I'm looking at:
a single SOK 24v 100Ah is affordable and still gives me a boost in usable capacity over the gel.
I'd like a pair of 12v 206Ah which is a bit beyond my budget.

either way, can I add the exact same battery(s) at a later date (1 year) if they are still available?

 

[HRTKD]

either way, can I add the exact same battery(s) at a later date (1 year) if they are still available?

Oh, sure. The recommendation there is to make sure that the old and new batteries are at about the same state of charge when you introduce the new battery to the system.

 

[wiseacre]

Thanks HRTKD

I appreciate your help

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