DC to DC charger for lithium

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DoughMyDays

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Hi Chaps.

After studying months of looking into lithium. (Not bought anything yet) One of the things I will need to protect my alternator is some form of Dc to DC charger.

I currently have a Yanmar gm10 with a standard alternator which outputs 35Amps. I am looking at 300Ah lithium in total. I know 35amp output may be nowhere near enough for this amount of Amp hours.

The issue is I can never find a straight answer for this area. Some say never get a 30+amp Dc charger as running your alternator nearly to its max current could fry the alternator? I understand I will also need something like an additional Alternator protector like what Sterling Power do. Or would I just need a much bigger alternator?

I also have solar panels currently installed on my boat too.
 
Victron Orion 30 amp DC to DC
Minimum of 60 amp alternator
Sterling Alternator Protect
Class-T main fuse
 
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Perhaps if you start from a different point and work out how much power you will use and then work out how long you will have to run the engine to replace the charge to the batteries. For example if you use 20Ah a day you could run the engine for 1 hour a day or 10 hours every 10 days (assuming a 20A charge rate). If the time is too long with the standard alternator you could look for a larger one if you can get one that will fit. There is a conversion for the 1GM10 that bolts on a second crankshaft pulley which could drive a second alternator.The total charging time is independent of battery capacity but a larger capacity means that you can run the engine less frequently but for longer. Again I assume you don't have any other means of charging.

I would doubt that the 1GM would handle a larger alternator without severely limiting the power available to the propellor. Unless of course you are just running the engine to recharge the batteries. Also I doubt that standard alternators are designed to output their maximum for extended periods without overheating.

If you have a small lead acid engine start battery you could always put a power diode across the isolator so that if the lithium charger shuts down, the alternator will send it's power to the engine battery.
I suspect that the alternator protector just consists of Transzorb power zeners that will limit any voltage spikes from an open circuit alternator. These only cost a few pennies each for a 1500W one.Transzorb
 
As I've said in numerous threads a drop-in LFP is simultaneously one of the most attractive but least suitable arrangements for marine installations. I won't repeat the arguments as we have the new Rod Collins paper (link above) and his original classic paper both of which should be essential reading. LiFePO4 Batteries On Boats - Marine How To

But just a note on the Sterling Alternator Protect. A battery to battery charger should protect the alternator from the high voltage spike caused by sudden disconnect. However it is recommended to fit a Sterling Alternator Protect as an additional back-up. Frankly they are currently so inexpensive, small and easy to fit that I think it a reasonable recommendation to protect all boat alternators whether the system is lead acid or LFP. You don't have a sudden BMS inspired disconnect with lead acid but there is always the possibility of accidental disconnect (especially if going the wrong way round a 1,2,both switch) or if the B+ terminal nut vibrates off.
Sterling Power Alternator Protection Device - APD12
 
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andsarkit said:
Again I assume you don't have any other means of charging.
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Yes I have a solar panel with a lithium ready victron charge controller installed.

andsarkit said:
If you have a small lead acid engine start battery you could always put a power diode across the isolator so that if the lithium charger shuts down, the alternator will send it's power to the engine battery.
I suspect that the alternator protector just consists of Transzorb power zeners that will limit any voltage spikes from an open circuit alternator. These only cost a few pennies each for a 1500W one.Transzorb
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This sounds like a dream if Im right in saying this. Would this allow me to keep my lead battery for my starter and seperate it from me being able to also have a lithium just for the purpose of my leisure battery?

I already have a duel battery isolator switch. But I cannot physically see how it is connected up.
 
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