Re: [electricboats] House systems - separate or together with drive system?

Myles,

I'm following what you're saying, and appreciate improving the life of the lithium battery by not fully charging it to the max allowed voltage.  But would you be giving up a significant portion of the battery capacity?

And I guess all of this depends on the exact details...

There was one "12V" Lithium battery I peeked at:

https://www.amazon.com/ExpertPower-Rechargeable-2500-7000-lifetime-Applications/dp/B07X2TM8MF/ref=sr_1_4?dchild=1&keywords=12v+lithium+battery+50ah&qid=1593187731&sr=8-4

It's rated for a max charging voltage of 14.4V, with a standby voltage of 13.8V.

So I guess if your "48V to 12V" converter actually put out 13.5V (typical of many automotive systems),  then you'd probably be in pretty good shape.

If it only put out a true 12V, then your 50Ah battery (from above example) would never get close to being fully charged, and you'd get a significantly reduced fraction of the 50Ah life out of it before needing more charging.

Right?

John

On Friday, June 26, 2020, 11:03:56 AM CDT, Myles Twete <matwete@comcast.net> wrote:

There's another consideration here: the house battery 'type'.

What Reuben says is correct if one is using PbA batteries for the house battery (12v or 24v or…).  Lead acid batteries need to be charged much higher than their nominal voltage rating and need to ramp the charge current down as that voltage gets near the end and then halt current (or possibly provide a trickle or maintenance charge after cooling down).

However, if instead of PbA batteries, you were using lithium for your house pack and that the lithium battery was rated, say, as a replacement for 12v (PbA) batteries.  Most of these are rated to 14.4v or so and there is no penalty at all in charging them only to 12v.  In fact, the lifetime of the batteries is improved by keeping the voltage lower, so…  And so, in the case of lithium batteries used as the house battery, you would not need (nor maybe would it be advisable) to use a 48vDC-12vDC charger unit (unless it were configurable for lithium) but simply use a 48/12v DCDC and you'd be just fine.

 

From: electricboats@groups.io [mailto:electricboats@groups.io] On Behalf Of Reuben Trane via groups.io
Sent: Friday, June 26, 2020 7:37 AM
To: electricboats@groups.io
Subject: Re: [electricboats] House systems - separate or together with drive system?

 

A DC/DC converter (power supply) is NOT a charger. I mistakenly did the same as you, using DC/DC converters hooked up to my 12v batteries (2 separate systems). They eventually "killed" the batteries. That is why I researched the DC/DC battery charger. It works as a constant source of 12v while charging the battery. That power supply you bought works w/o a battery supplying a constant 12v. I use 500w Mean Well 48v/12v to supply 2 of my 12v panels. And I have 48VDC/12v battery chargers going to 12v batteries - one for the panel with the windlass (hi amps) and one to the panel with the generator (ditto). My DC/DC converters can't handle the higher amp loads.