ESPcat Battery Bullshit

What with Trump being President, we have come to expect regular doses of bullshit.  Even so, I still get angry when someone lies to me.  Suppose you were to go to the gas station to fill up your car.  You pay for a full tank of gas but only get 1/3rd of a tank.  Would you be satisfied?  Would you feel at all cheated?  Is this the way God intended the world to operate?  I don’t think she would be pleased at all.

Well here is the thing about batteries for your boat.  If you go to your local marine supply store and purchase a 100 amp-hour, deep cycle battery; guess what? You only can use that battery to get 30 amp-hours (maybe 50 if you accept a short life) because if you try to use anywhere near its rated capacity, it will very quickly die!  So it’s not really a 100 amp-hour battery; its a 30 amp-hour battery.  Now that’s what I call “battery bullshit”!

“How can that be” I hear you ask.  Is Trump selling those batteries?  Well “no” we can’t blame this one on Trump.  Have a look at this graph:*
Battery Cycle LifeThis graph compares lithium battery (like in the Tesla electric car) to an AGM battery (the really expensive, deep cycle, lead-acid battery the marine shop sells).  Even using the AGM battery at 30% of its rated capacity, it will still only last half as long as a lithium battery discharging to 75% of its rated capacity.

Here is what I might expect my amp-hour usage on Borderline to be if I use a 12V battery:
1 – VHF Radio      0.8
2 – Stereo              10
3 – Cabin Lights   15.8
4 – refrigerator     42 (I will try to get an efficient fridge that is better than this)
total                        68.6 **

If I’m going to use 68.6 amp hours per day, I need a bullshit battery capacity of something like 229 amp-hours.  If I use a lithium rather than a lead-acid, my capacity needs only to be 91 amp-hours.  So why isn’t everyone using lithium batteries in their boats?

The lithium battery is more expensive at around $NZ 1,860 compared to around $NZ 700 for the equivalent, lead-acid battery.   The lithium battery has to have a built-in BMS (battery monitoring system) or it will die when it gets either over-charged or under-charged.   The lead-acid battery will weigh around 50kg while the lithium battery weighs about 12.6 kg or about 1/4th the weight of the lead-acid battery.  If it weren’t for the BMS, the lithium battery would only cost around $NZ 886 rather than $NZ 1860 for one with the BMS built into it.

I’m building my own BMS of course and mine will be better than the built-in one.  I am in the process of designing something I will call the ESP Energy Box.  ESP Energy Box will have the 91 amp-hour, lithium battery, the BMS, the solar charge controller and a 2,000W, 240VAC inverter.    200W worth of solar panels will keep it charged.
ESP Energy Box enclosureSolar Panels
If it works well, I will offer the complete package for sale to all my blog buddies and their friends and anyone else who wants solar power for their boat, RV or whatever.  It’s all part of my master plan to change the world!

** multiply these amp-hour numbers by 12 to get watt hours


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