I have been researching the newer battery types in anticipation of buying a newish RV with a marine type DC compressor fridge rather than the more typical absorption fridge. With this change, the DC requirements of RVs become very similar to our boats. So the following is a review of the various battery types that are available today with pros and cons of each:
Traditional flooded cell golf cart batteries:
I have long advocated that GC batteries provide the most bang for the buck for marine use and for many applications that choice is still the best.
1. Can only be charged at .25C
2. Should not be discharged below .5C
2. Slow to charge beyond .85C
3. Heavy and require periodic water checking and addition
4. Will sulfate if left at a partial state of discharge
5. Cost about $100 for 100 Ahs at 12V, more for premium brands
AGM batteries:
1. Same as FLAs but don't require water checking.
2. Some say they can be charged a little faster and discharged a little further than FLAs
3. Cost about $200 for no name to $300+ for brand name 100Ah at 12V
Firefly carbon foam batteries:
1. Can be charged at .4C with no harm
2. Can be discharged to .2C routinely with no harm
3. No sulfation risks and no maintenance
4. Cost about $500 for 100 Ah at 12V
Lithium batteries with integral BMS*
1. Can be charged at 1C and discharged to near zero with no harm
2. No sulfation risk and no maintenance
3. Light, about 1/2 of the above types
4. LiFePO4 chemistry, the only kind considered for marine or RV, use has very low fire risk
5. Requires a lithium specific charger for best performance as well as correct parameters for an externally regulated alternator
6. Cost about $1,000 for 100 Ah at 12V
*The only kind I would consider for a boat. External BMS lithium battery systems are for the technogeek IMO.
So GC FLAs give the most usable Ahs for the buck 100*(.85-.5) = 35 Ah or .35Ah/$. AGMs provide .18 to .1 Ah/$. Both have risks leaving partially charged for long.
Fireflys provide (100*(.85-.2) = 65 usable Ahs or .13 Ah/$. Lithiums provide 90 usable Ahs or .09/$. Note that this doesn't consider charger or alternator upgrades that Lithiums may require.
So I would go with GCs if I had lots of room, weight wasn't a real consideration and had decent access for maintenance. AGMs if maintenance was an issue but Fireflys are also competitive if you consider usable Ahs. And Lithiums if room and weight were big considerations.
David
Traditional flooded cell golf cart batteries:
I have long advocated that GC batteries provide the most bang for the buck for marine use and for many applications that choice is still the best.
1. Can only be charged at .25C
2. Should not be discharged below .5C
2. Slow to charge beyond .85C
3. Heavy and require periodic water checking and addition
4. Will sulfate if left at a partial state of discharge
5. Cost about $100 for 100 Ahs at 12V, more for premium brands
AGM batteries:
1. Same as FLAs but don't require water checking.
2. Some say they can be charged a little faster and discharged a little further than FLAs
3. Cost about $200 for no name to $300+ for brand name 100Ah at 12V
Firefly carbon foam batteries:
1. Can be charged at .4C with no harm
2. Can be discharged to .2C routinely with no harm
3. No sulfation risks and no maintenance
4. Cost about $500 for 100 Ah at 12V
Lithium batteries with integral BMS*
1. Can be charged at 1C and discharged to near zero with no harm
2. No sulfation risk and no maintenance
3. Light, about 1/2 of the above types
4. LiFePO4 chemistry, the only kind considered for marine or RV, use has very low fire risk
5. Requires a lithium specific charger for best performance as well as correct parameters for an externally regulated alternator
6. Cost about $1,000 for 100 Ah at 12V
*The only kind I would consider for a boat. External BMS lithium battery systems are for the technogeek IMO.
So GC FLAs give the most usable Ahs for the buck 100*(.85-.5) = 35 Ah or .35Ah/$. AGMs provide .18 to .1 Ah/$. Both have risks leaving partially charged for long.
Fireflys provide (100*(.85-.2) = 65 usable Ahs or .13 Ah/$. Lithiums provide 90 usable Ahs or .09/$. Note that this doesn't consider charger or alternator upgrades that Lithiums may require.
So I would go with GCs if I had lots of room, weight wasn't a real consideration and had decent access for maintenance. AGMs if maintenance was an issue but Fireflys are also competitive if you consider usable Ahs. And Lithiums if room and weight were big considerations.
David