We have 4 brushless motor for a boat. That motor takes 15.1 Ampere at maximum throttle. Our ESC’s are 30A blheli. We would like to use two pieces 12V,7A rechargable lead acid battery bu connecting them parallel. Normally we are using 3S-25C-8000mah lipo battery. Can we use lead Acid Battery?
I would use one of the batteries, knowing that the discharge curve is different than that of a LiPO. See what you get.
Paralleling batteries should be approached with caution, especially parallel charging.
Thank you so much. I don’t know the discharge curve. I just check from internet the lead acid batteries are 0.5c so 3.5ampere but it is not enough for my motors. But I also saw some project that lead acid batteries were in use.
What is the model number of your battery? Generally you can draw 15A from a 7AH battery for some minutes - be aware that there is no danger point when discharging lead-acid, the voltage will fall right to zero if held under load - whereupon it must be immediately recharged and floated PER THE MANUFACTURES ADVICE, which varies. Do not leave lead-acid discharged, as that will damage them. Again, please reference the spec sheet for your specific battery. Refer to the discharge rate/time curves.
You will need to calibrate your voltage cut-off/failsafe based on how deeply you want to draw down the battery.
Been working with and living on off grid solar for over 20 years.
A few things to consider:
a) As mentioned by John, avoid using batteries in parallel. In the solar industry if it can’t be avoided then batteries are ordered specifically from the supplier / manufacturer for this. In that way they can be matched in regards to internal resistance as close as possible. If not you’re asking for trouble as they will “wear” each other out rather quickly.
b) Lead Acid Batteries don’t like to be discharged more than 20-30% of rated capacity. Even the deep cycle batteries will suffer if such deep discharge occurs multiple times. (It is widely accepted that a few deep discharges will reduce expected lifetime of battery by around 50%)
c) Also if exposed to temperatures above 35C° the lifetime will be greatly reduced.
You have mentioned motor will use 15.1A but also stated you have 4 motors.
So you need a battery that can cope with at least 61A current draw.
Something like a 60Ah car battery would do nicely and easy to get at low cost.
Better still a deep cycle battery of similar rating.
As to duration: If a 60Ah battery is being used you should only use about 20-30% capacity as mentioned above. So: 60Ah-20%=12Ah usable capacity. This will leave some reserves without affecting lifetime. Or you can go 25% = 15Ah still reasonable. With that above mentioned current draw in mind you would get approx. 15 minutes of usage out of such battery.
Wondering if it is 15A/motor or 15A total, as knowing exactly would have changed my response? Happy ‘Sailing’!