My mother has a 2400va trolley inverter with 2 x 105ah batteries. 

I believe this system is not heavily loaded: decoder, smart TV (40 inch I think, no more than 44), occasional charging of phones. But with stage 4 becoming a regular thing, they are working harder. At some point they will need replacement. 

So what about the lithium drop in replacements that are available? Can they be discharged for longer? Do they take longer to charge? Does anybody care to reccomend a brand? 

They cost a lot more I know, but that box has made a difference, and I worry about those SLAs which are now in a discharge cycle two or three times every day. 

Do I need to replace both or can I / should I replace the two SALs with one lithium? 

I’m in the same boat as you are, also planning for battery replacement sometime soon, hope you don’t mind me piggybacking on your thread. 
 

There’s a massive thread on MYBB about these inverters and options available for battery replacement, among other things. 
Many guys recommend that the charge rate be changed to 10A for the lithium drop in batteries. But some have also reported that they’ve have issues with certain brands, and they don’t work properly with this inverter because of the way it charges, or rather, when it stops the charge cycle. 
 

Another thing that comes up quite a bit is using a battery balancer to make sure that both batteries charge at the same rate. 
 

There’s nothing configurable on the inverter aside from the charging rate 10/20A.

 

Hoping to hear more from some of the more knowledgeable guys. 

I haven't had a chance to play with them yet but a lot of people swear by Hubbles. I am currently talking on another thread about balancing issues when connecting lithiums like this so a balancer may be in order... The real issue here is that inverters that are designed to run AGM/SAL/Flooded batteries not only have a different bulk voltage but the float tends to change as well. Because of this, the batteries often end up charging incompletely which isn't great for the battery cycle life. If your trolley says explicitly that it supports lithium charging or if it lets you change these settings you will be fine, but if not you will need to add some hardware to make the charging work...

If you can offer the model of the trolley I'll be happy to look into it and check if it'll work for you?

9 minutes ago, Psy said:

I haven't had a chance to play with them yet but a lot of people swear by Hubbles. I am currently talking on another thread about balancing issues when connecting lithiums like this so a balancer may be in order... The real issue here is that inverters that are designed to run AGM/SAL/Flooded batteries not only have a different bulk voltage but the float tends to change as well. Because of this, the batteries often end up charging incompletely which isn't great for the battery cycle life. If your trolley says explicitly that it supports lithium charging or if it lets you change these settings you will be fine, but if not you will need to add some hardware to make the charging work...

If you can offer the model of the trolley I'll be happy to look into it and check if it'll work for you?

It's an old design. Doesn't have pure sine output. I think it's a Crystal Intellipower. As per @SudhirM 's post, there is a switch to set charging rate to 10A or 20A. There is nothing else configurable, so now I'm thinking maybe not if I won't be able to take good care of the LIFEs

Edited November 22, 20223 yr by Bobster.
correction

Yeah, I have had a few people ask me to fix old-school inverters like this. I often get asked about Lithium upgrades and I will say it can be done with a balancer or BMS to manage the charging, but the unit was designed for a specific type of battery and you'll have a much better time keeping the same type of battery. Check the model on the trolley and check the spec-sheet, it should state the float/bulk charging voltages. Take those figures with you if you are going to get new batteries and ask for batteries with similar voltages etc. It's the best way to make sure the money spent on new batteries doesn't get wasted by bad charging cycles.

1 hour ago, Psy said:

Yeah, I have had a few people ask me to fix old-school inverters like this. I often get asked about Lithium upgrades and I will say it can be done with a balancer or BMS to manage the charging, but the unit was designed for a specific type of battery and you'll have a much better time keeping the same type of battery. Check the model on the trolley and check the spec-sheet, it should state the float/bulk charging voltages. Take those figures with you if you are going to get new batteries and ask for batteries with similar voltages etc. It's the best way to make sure the money spent on new batteries doesn't get wasted by bad charging cycles.

The LIFE replacements usually have a BMS of sorts built in to the package, no?

25 minutes ago, Bobster. said:

The LIFE replacements usually have a BMS of sorts built in to the package, no?

Yes, but built-in BMS doesn't always work with AGM charging parameters. We are going through this stuff on this thread: 

Balancing and charging will be a headache, the BMS might not like the voltages used for charging and lead to incomplete charging cycles etc which isn't great for your battery life. To be fair, I haven't had time to play with these kinds of drop-in lithiums yet (I mostly deal with Pylontech type batteries) so this is mostly theoretical.

 

3 hours ago, Psy said:

Yes, but built-in BMS doesn't always work with AGM charging parameters. We are going through this stuff on this thread: 

Balancing and charging will be a headache, the BMS might not like the voltages used for charging and lead to incomplete charging cycles etc which isn't great for your battery life. To be fair, I haven't had time to play with these kinds of drop-in lithiums yet (I mostly deal with Pylontech type batteries) so this is mostly theoretical.

 

I suspect the BMS on these just takes care of basic tasks like too high a discharge rate etc. 

But thanks for your time and the information. I think they're not going to be worth it in my case.