Li-ion replacement for FM1212 brick battery

[buenos]

Hi

I have a model vehicle that takes a 12v FM1212 brick sealed-lead-acid battery with F1-terminal contact.
Is there a Li-ion replacement available in the same form factor?
If the voltage is slightly different than it is not a problem, for example 10V-16V would be OK.
My problem is that when I am not using the model for 3 months or more, the battery dies and needs replacement, the max chargeability reduces to zero Ah. Probably a Li-ion or Li-polymer or even a Ni-Mh battery would last a lot longer than 3months.

 

[FvM]

LiFePO4 is a perfect replacement for 6 Ah sealed lead-acid batteries, but I'm not aware of an available form factor replacing the small 1.2 Ah type.

NiMH would be the next best choice, I think.

You can expect a fair lifetime of sealed lead-acid blocks if you don't store them in discharged state.

 

[buenos]

"if you don't store them in discharged state"
-the problem is that I might only use it once a year, and the standby circuits (maybe 1mA) will completely discharge the battery.
Would the NiMh die in these same conditions? What about LiPo? Do they all come with protection circuit built-in?

 

[FvM]

You didn't yet talk about standby circuits or 1 year standby time. In this case you would want to disconnect the battery...
NiMH can be expected to have considerable self-discharge, but isn't that sensitive to deep disacharge.

I have no full specification of LiFePO4 batteries. I assume that deep discharged should be avoid if possible.The charge behaviour is compatible with Pb batteries, they don't use built-in protection circuits,

 

[buenos]

the only problem with the standby is that it causes deep discharge that can damage some types of batteries. Before use I would charge up anyway, but I cannot charge an already dead battery.

 

[buenos]

OK, which type of battery can I leave untouched (zero-maintenance) for several months (with or without standby load)?

 

[FvM]

- Li-Ion with protection
- NiMH (if a certain lifetime reduction is acceptable)

Please consider that battery lifetime is counted in charge/-discharge cycles. So fully discharging a battery every 2 months will definitely reduce lifetime, and require recharge before using the device.

 

[buenos]

Every time I leave the system rest for a year, the lifetime would reduce by x%? That should be ok. I want to charge up maybe 1x-30x a year, and should last for 5 years.

How about charging a 4cell Lipo pack with a 2pin charger without a cell-charge-balancer?