Reed Muse 3C turntable

I’m very happy with the 12v battery that I’m using as a power supply but I do find that the speed fluctuates when the battery gets very low (after 6 hours of listening). I intend on buying a bigger battery (more amp hours) but I’m wondering if there are other parameters that I should be looking at when selecting a battery. Ideally the battery would deliver a high quality 12v at any point in its discharge cycle. Perhaps there is a battery brand that is the gold standard in terms of consistent power delivery?

exlibris, have you considered Lithium Polymer or Lithium Ion (Li-po / Li-ion)? I don't recall you mentioned battery tech of your existing 12v. Perhaps 2 batteries, one on charge when the other is in use?

Thank you for the recommendations I will investigate.  Details on the battery I have can be found by clicking the link in the message I posted above on 08/28/2015.

I looked into the various lithium-based batteries and they appear to be an excellent option.
The only hesitation I have is the protection circuitry that they contain.  
"They require protection from being over charged and discharged too far. In addition to this, they need to have the current maintained within safe limits. Accordingly one lithium ion battery disadvantage is that they require protection circuitry incorporated to ensure they are kept within their safe operating limits."
I'm just wondering if any of this circuitry can produce noise which could lead to speed fluctuations in the turntable(?)

Any owners in EU?