please tell me what I'm going wrong

[margaret]

I'm 75 years old and live in gambia. I am stupid on technical issues.
I currently have a Su Kam falcon 2000 inverter and 4 x su kam powerbank batteries. I live in gambia, west africa, where we mostly get some sort of power cut 5 days a week - 3 - 6 hours. In rainy season they can last up to 15 hours+.
One of my batteries has had it, and I've been recommended to stick to the best of the 4 I've got with same inverter, but add 2 x tubular batteries - Luminous Inverlast 220 Ah.
Can I do this, or will 2 new and 2 older - connected 2 x 2 - ruin the new ones. Should I go for gel, or is the recommended tubular better?
Please help

 

[Hedges]

Mixing new and old lead-acid batteries may result in the bad ones pulling down voltage of the new ones.
Mixing different types could be a similar problem, especially if they are of different voltages.

Gel requires a different charge voltage from AGM, and FLA is yet another different voltage.

Cheapest high capacity is wet-cell FLA. Some have short life, while forklift batteries if properly maintained can last a long time.

How long does your power remain up with just the 3 good batteries?
How low does battery drain before shutting down? (Draining 100% accelerates wear of battery. Typically 50%, some types 80% DoD is recommended.)

Do you have solar panels? If not, that should help with extra hours operation during daylight.
PV panels may be cheaper than batteries, a better value. (Can't help much during rainy season, though!)

 

[MisterSandals]

I am stupid on technical issues.

You're ahead of most that come here and have proceeded to mess things up before asking questions!