Hi Anne,
You are correct, "driving the boat from the charger" is supplying drive energy from a portable generator to the electric drive through your regular battery charger while underway. This is a common strategy for extending the range of your battery bank by members of this group.
I believe that Jim's comment was more related to the 100Ah size of the battery bank rather than the FLA chemistry. If your system can pull 180A, your drive could drain a fully charged 100Ah 48V FLA battery bank to 60% depth of discharge (DoD) in less than 8 minutes under full power (8640W load). Realistically, you wouldn't pull that kind of power for more than tens of seconds or less to get out of a tight spot, your regular cruising will be at much lower power levels.
But still, a 4.8kWh (100Ah x 48V) battery bank is fairly small for a boat your size. Assuming a load of 1500W (31A x 48V) for 4 knots in your boat, the FLA batteries would only last 73 minutes to 60% DoD, that works out to about 5nm on a regular charge. AGMs deliver more power per Ah and can be regularly discharged to 75-80%. The same size (4.8kWh) AGM battery bank would last more than 17 minutes at 180A to 75% DoD and 120 minutes at 31A to 75% DoD. That means that the AGM batteries with the same rated size (100Ah) extend your cruising range from 5 to 8nm.
Before anyone assumes that AGM provide 75% more range for the same size batteries, this math is specifically for a 100Ah bank. As you move into larger battery banks, the difference between chemistries becomes less dramatic. Double the size of the bank and it looks more like this:
9.6kWh (200Ah x 48V) FLA to 60% DoD = 19 minutes at 180A and 175 minutes at 31A.
9.6kWh (200Ah x 48V) AGM to 75% DoD = 37 minutes at 180A and 259 minutes at 31A.
This works out to 48% more range from the same size AGM bank at 31A. This is one example of why I recommend AGM for anyone that can afford them.
Fair winds,
Eric
Marina del Rey, CA
--- In electricboats@yahoogroups.com, amracel@... wrote:
>
> Thanks again for the suggestions, folks. A few more questions, however.
>
> Capt Mike and Eric, you both mention 'driving the boat from the
> charger'. I assume you mean running the boat with the generator
> connected to the charger?
>
> Jim, what do you mean the wet cells will get 'toasted in a hurry'?
> What happens?
>
> Mark, I'm definitely going to call about the refurbished units!
>
> Anne
>
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