husqvarna Gen 1 Automower pack

HELP needed. I have a Husqvarna Generation 1 auto mower that needs a new battery pack. The machine itself is a 99/00 model. I purchased a Husqvarna pack for about $300 4 years ago, and now need a new one - but its discontinued.
I brought it to Batteries Plus last Monday and they thought it would be 10 SUB Cs. The pack is stated as 12 Volt, 4.4Ah NIMH.
Now, my older pack appears to have 20 subcs, but my newer pack appears to have only 10. (older pack is the original from 99/00. The newer one is from 2014.

Attached are pictures of the older pack. The newer one is still at BatteriesPlus, which I'mgoing to gather back from them : The newer one has a slightly different plug on it that works with my board).

Does this appear to be a difficult build? Recommendations? Totally new to battery building! but seems like i could get help online vs B+...

(why would the older pack have 20 subc and the newer one have 10?) - Both packs are 12V and 4.4Ah

TIA!!!





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Not sure of how to answer the question, as I don't know why they'd go smaller, either.

But, I would personally get some LiFe cells and drop those in and slap a lithium bms on it and go to town with a conversion. In the end you'd have a much longer run time, faster charging, and the power of lithium.

Given that these Mowers are robotic, and charge themselves, I would stick to the original battery configuration. Otherwise I imagine issues will arise as the mower will not know its state of charge.

I think in this situation you will be stuck with the original configuration.

i expect that nimh charger will be part of the mower and nimh are charged very differently to lithium... does this have a chance to work properly?

on the other hand side, i replaced the nimh battery of my roomba with a li-ion pack, but it was prebuilt. i dont know any technical details of my new pack compared to nimh pack...

regards
karl