I'm about to replace my boats house batteries and I'm considering lithium.
I wasn't necessarily going to go this route except that I've stumbled across a reasonable deal and my current battery charger is compatible to charge lithium. My concern is, do I need to also replace the alternator to a specific type, or will an 80 amp/h alt be sufficient to avoid over heating?
Select to expand quoteToph said..
I'm about to replace my boats house batteries and I'm considering lithium.
I wasn't necessarily going to go this route except that I've stumbled across a reasonable deal and my current battery charger is compatible to charge lithium. My concern is, do I need to also replace the alternator to a specific type, or will an 80 amp/h alt be sufficient to avoid over heating?
I looked into this but decided not to go lithium as I had one battery that I brought for testing fail. I purchased a victron 12 v to 12 volt charger so the lead acid start battery that takes the alternator charge can then charge the lithium house battery's at the required settings. I would recommend not purchasing cheap lithium battery's. 
wow thats scary ,looks like it could have been a lot worse .i also looked at it a few months ago but was worried about an explosive failure so decided to stick with agm. Last lot had lasted 10 years by the time they die i think pricing and reliability should settle down
Select to expand quoteToph said..
I'm about to replace my boats house batteries and I'm considering lithium.
I wasn't necessarily going to go this route except that I've stumbled across a reasonable deal and my current battery charger is compatible to charge lithium. My concern is, do I need to also replace the alternator to a specific type, or will an 80 amp/h alt be sufficient to avoid over heating?
Hiya Toph,
If you buy the car replacement style batteries it'll be fine as they have an integral BMS or controller. Your voltage reg will think its a normal lead acid in that instance.
But otherwise yes, you should have a controller. The alternator isn't the issue per se, it's more the voltage regulator. Lead acid has a much higher internal resistance than lithium so it can put up with a 'dumber' charging system. Lithium is easy to screw up if you don't control the charge rate.
Select to expand quotesouthace said..Toph said..
I'm about to replace my boats house batteries and I'm considering lithium.
I wasn't necessarily going to go this route except that I've stumbled across a reasonable deal and my current battery charger is compatible to charge lithium. My concern is, do I need to also replace the alternator to a specific type, or will an 80 amp/h alt be sufficient to avoid over heating?
I looked into this but decided not to go lithium as I had one battery that I brought for testing fail. I purchased a victron 12 v to 12 volt charger so the lead acid start battery that takes the alternator charge can then charge the lithium house battery's at the required settings. I would recommend not purchasing cheap lithium battery's.
That looks familar!
I have four lithium batteries here (not mine) and they all look like Southace's.
The problem with the Lithium drop in replacement batteries is you are relying on the bms to protect the battery, if it fails your battery is toast. Setting them up without relying on the bms for protection but as a secondary back up is a better way to go.
The bms in the cheaper lithium batteries are not very good and can fail easily when overcharged.
Lithium does not handle being overcharged well.
I have 4 x 200amp lithium batteries in my motorhome, 24v bank, set up to charge on solar, bulk charge only at 28v , no absorption or float and they are happy at that, anything over 28v they don't like.
You need to look at it from a cell level not whole battery level, cells 3.2v, max charge voltage 3.65v so set it back a little to account for system tolerances and charge at 3.5 or 3.4v and your batteries will last a long time and still be charged to 95-99%.
Hi Toph
I changed mine to lithium and wired in a victron Dc/dc converter the battery supplier told me that my alternator should be fine but I did it just as a precaution I've kept my house batteries seperate from the starter and I just have a switch to turn on the converter to charge the house with the engine if needed. seems to work well
Ok, thanks all for the replies. I wasn't even thinking about overheating the batteries (even though I new they could), but was more thinking about the alternator.
I was watching a clip where lithium batteries where being charged by a normal alternator and the alternator temp was being measured. I don't know what size alternator was being used in the test, but it burnt out when at idle speeds. It was significantly warm at higher RPMs, but didn't burn out as the cooling fins where doing their job. While the purpose of the clip was to sell a specific brand alternator replacement, it did leave me wondering if a larger alternator would handle the temperatures better, or would that create a higher charge rate and therefore overcharge/heat the batteries.
Southace, with your set up, have you mixed lithium and lead acid?? I didn't think that would be possible.
Select to expand quoteToph said..
Ok, thanks all for the replies. I wasn't even thinking about overheating the batteries (even though I new they could), but was more thinking about the alternator.
I was watching a clip where lithium batteries where being charged by a normal alternator and the alternator temp was being measured. I don't know what size alternator was being used in the test, but it burnt out when at idle speeds. It was significantly warm at higher RPMs, but didn't burn out as the cooling fins where doing their job. While the purpose of the clip was to sell a specific brand alternator replacement, it did leave me wondering if a larger alternator would handle the temperatures better, or would that create a higher charge rate and therefore overcharge/heat the batteries.
Southace, with your set up, have you mixed lithium and lead acid?? I didn't think that would be possible.
I watched the same clips regarding alternator burn outs hence why they recommending the Dc to Dc victron charger apparently to save the alternator more than the lithium battery. Im not sure about this part. my lithiums I brought for a test for $500 each I just put them on a trickle charge and one melted , I never hooked the 2 purchased batteries to the ship, one sat at 13.3 since it arrived and the other dropped to 3 volt with no load.
im just sitting on AGM at moment but need to make the choice soon.
