Hi John:

The company no.co makes a family of Li batteries that's a form, fit and functional replacement for a classical flooded
lead acid battery for small gas engines, like a motorcycle or generator (4AH).
https://prc68.com/I/Gen.shtml#Replacement_Battery
The idea is that you do not need to use a Li specific charger.  They say there's a small capacity loss when using a
flooded lead acid charger compared to a Li specific charger.

There's a problem with Li batteries that I'm starting give a lot more weight and that's what happens when they catch
fire or vent. This is something that has a very low probability of happening but when it does the result is very very
very bad.  Fundamentally you can not put out a Li battery based fire and it vents toxic explosive gases.

The same company (no.co) has a family of smart chargers and I've been playing with on on a car battery that turns out to
be an AGM (I didn't know that when I started).
https://prc68.com/I/Cars.shtml#Noco_Genius_10

Today I'd recommend replacing the existing AGM batteries.

--
Have Fun,

Brooke Clarke
https://www.PRC68.com
axioms:

1. The extent to which you can fix or improve something will be limited by how well you understand how it works.
2. Everybody, with no exceptions, holds false beliefs.

-------- Original Message --------

All -- thanks for the responses!  They've been very helpful.

Just to summarize a couple of interesting/important things I've learned:

• Don't confuse generic "lithium" batteries with the specific LiFePo4
  type -- the other/earlier types have significant safety issues that the
  newer technology greatly moderates.

• I looked at inverter/charger options but most are much larger than I
  need (seems like 3KVA is about the smallest) and consequently a whole
  bunch more expensive.  If you ordinarily have mains power available, a
  traditional UPS seems to do the same thing in more reasonable sizes and
  for less money.

• Bob LaJeunesse suggested paralleling AC power supply with battery
  using Schottky diodes.  That allows the battery charger to be whatever
  it needs to be without having to power the load as well.  And it
  provides an additional redundancy in that you can disconnect the
  battery/charger for maintenance without affect the downstream gear.  I
  like that idea a lot and think I will do something along those lines.

Thanks!
John

On 5/27/24 11:38, paul swed via time-nuts wrote:

LiFePO4 batteries have a very steep cliff: a very flat voltage curve during discharge, followed by a sudden switch off performed by the BMS. So you cannot monitor battery state based on voltage.

I own a couple I use for /P hamradio. Experiences have been excellent.

Wilko

Instead of using Schotty diodes and possibly a relay a more modern
solution would be 2 ideal ideal diode circuits. Ideal diodes are simply
mosfets with an additional controller IC to switch them on as needed.
This removes most of the voltage drop of a diode and are they are very
robust in operation. I have used the LM74704 in a few designs. There are
also some modules available from ebay and other places if you don't want
to build the complete circuit.

Regards,
Denis

On 28/05/2024 11:52 am, John Ackermann N8UR via time-nuts wrote:

Actually, you can monitor voltage to determine when to start charging. I
have a 36V, 80AH LiFePO4 battery for a 600 Watt solar panel setup. When
the voltage is 39.7 or more, the battery will reliably hold up overnight.
Below that, I put it (and the load) on the charger (an 8 Amp, max unit
supplied with the battery). At 36.5 Volts and below, immediate charge
is advised and at 36.0 Volts, it is necessary (under 3 hours left).

I have added a 36 Volt DC power distribution system to the house. 5 Volt DC-DC
converters at the endpoints and a centralized 12 Volt DC-DC
converter (with its output also distributed with the 36 Volts to the
various endpoints) complete the system.

On Tue,28 May 2024 11:01:01 +0200 Wilko Bulte
via time-nuts time-nuts@lists.febo.com wrote:

On 5/27/24 11:59, Tom Van Baak via time-nuts wrote:

I've been using PowerPoles on everything DC for years.  Color coding
and/or keying for different voltages is interesting.  Red is universally
used for 12V, and it seems that orange is common for 24V and that's what
I use.  Beyond that, it's a free-for-all.  I've been using a lot of 5V
lately for SDRs, RPis, and such and have standardized on green for that.
I currently don't have anything running on 48 volts so am not sure if
there's a standard for that.  However I'm currently using yellow for
variable-voltage power supplies and general-purpose leads to indicate
"check me first".

When I built my current lab and had to put in AC power to various
places, I got a used 3.1KVA UPS with 220V input and split phase output,
and an external battery pack for extra run time.  It's semi-hardwired
into a closet in the basement with output going to a six 110V circuit
subpanel that drives outlets throughout the lab area.  It's "semi"
hardwired because there are RV-type mating connector pairs on input and
output that let the UPS be bypassed relatively easily.

That has worked very well, but after seven years all the batteries --
UPS, 24V, and 12V are about exhausted so it's a good time to re-engineer.

John

On 5/28/2024 7:54 AM, Stephen C. Menasian via time-nuts wrote:

In fact the  Li-Time 100A LiFePO4 battery I just got for my camper has
Bluetooth connectivity to the BCM, so  you can monitor state of charge
and other parameters at any time using an app on your phone.

73, Bob W9RAN

And LIFEPO4 12V 100AH  pre-made batteries  vary in quality

In general, the full encapsulated plastic nice looking types are built
with lots of B grade cylindrical cells.

The best are built with single prismatic cells. IE 4 cells for 12V , not
400 !

The cylindrical B grade cell type are about half the price, but they
never last as long.

Examples of quality battery brands  built with prismatic cells-

CALB, GBS, Thundersky. There's probably some US made, now, also.

On 29/05/2024 4:40 am, Robert Nickels via time-nuts wrote:

Hi

Ok, I have internet for at least a day ….

One example of a straight charger:

https://shop.pkys.com/ip44-charger-12-30-1+1

No, still not cheap, but not as wild as a 2KW hybrid.

https://shop.pkys.com/multiplus-12-2000-80-50-12vdc-120vac-ul

The gotcha with the diode approach is the inrush current on connect / disconnect. The diodes need to be pretty beefy to handle the typical surge.

Since the typical LiFePO4 has a BMS in it, the real point is hitting some very specific voltages. You need (say)  > 14. 25V and < 14.55V for the top end of your charge cycle. You need > 13.55 and < 13.75 for the “idle”part of the cycle. The BMS should take care of low voltage cutoff and it also should handle cell to cell equalization. The BMS also takes care of odd things like shorts ….

I’ve been running LiFePO4’s in the RV’s for about 7 years now. They do a very good job. I also run them at home for backup. Why?

1. They charge quickly. There is no “long tail” in the charge profile.

2. They hold charge very well ( like for a year …).

3. There is no outgassing to worry about

4. You get 100% of the “label amp hours” as opposed to roughy 50% for lead acid.

5. Cost wise, they beat good AGM’s in terms of cost for usable capacity.

Fun !!

Bob