Float charger? Cut off at 13.5v rest until 12.5v before switch on?

[danielwritesbac]

Would not a simple fixed current charger circuit help?
say.. something around 20-50 mA? That should be close to float charging, charge current would be close to the batterys own discharge current.

That appears to be the answer for achieving the lowest cost energy bills.
I probably need to make a subminiature Class 5 SMPS powered charger capable of adjustable voltage and current.

Adding this will cause the bigger charger to never reach switch on voltage until somebody turns on a light or other appliance.

Thanks for the tip!! Yes, I do happen to need multi-stage charging because of electri$ity bill$.

 

[doctordata]

Conrad ladeautomatik kit

I use a couple of window comperators on my batteries and they work great ! I bought them in Germany at Conrad . Conrad 10A automatic charger kit buy now - Conrad Electronic SE Battery charger kits & modules Electronics Online Store . Go to details and download the V2 manual . It's in German , but the schematic is included .
You can adjust the lower and upper voltage of the window comparator .
I have 6 of them and my batteries love them . The V1 also works great , but the IC's are hard to get

Cheers ,

Rens

 

[danielwritesbac]

The majority of chargers have many really inefficient options and typically, the battery monitors that will pull the battery down to damage voltages whenever the RV is unplugged for a long time.

Now looking for an alternative plan involving an SMPS.

 

[Nico Ras]

Daniel,
that charging information comes from the battery manufacturer.
Do not expect the charger manufacturer to know what every manufacturer and every model from each of those manufacturers needs as a charging requirement.

Go to your battery manufacturer and ask them what your battery needs !!!!!!!!!!

That would be about the best advice anyone can offer. A battery charger manufacturer would tune his chargers to the average most popular but this is not an absolute. An AGM requires slightly different voltage to a refillable Lead Calcium or a gel type, etc. If you want to charge at the accuracy that you require the battery manufacturer would provide you with the required charge voltages and temperature curves.

If they cannot tell you these characteristics then they are not battery manufacturers but purely product branders and the batteries could be anything really.

 

[Nico Ras]

Daniel, as a matter of interest, a $130 battery is not going to give you much more that 300 - 400 of deep charge /discharge cycles.

A deep cycle battery that would give you a life of 3000 - 4000 cycles will cost you much more than that.

This is probably one of the most complete battery information sites available: Battery Information Table of Contents, Basic to Advanced
it may give you a better understanding of what you want to do.

 

[danielwritesbac]

. . .what you want to do.

Thanks for the link.

I've actually learned more about what I want to do.
1). SMPS very low amperage float charger for maintenance.
2). Engage a bigger stronger charger, on demand, during periods of high demand, but no connection during low demand (need to combat energy bill troubles).
3). Disconnect battery monitors from chargers when AC is unplugged (as is expected of RV use, the charger is "installed" and may spend periods of time unplugged.)

The Hawkins charger, once outfitted with strong SCR, and 10-turn trimmers, did a fine job with the voltage needs, is strong enough for charge-while-run and has a very clean output, with just 0.42v of AC content--far cleaner than most chargers. To turn off the battery monitor drain when the mains are unplugged, I've added an additional half-wave rectifier and smoothing caps to the transformer to power a 40a automotive type relay that will disconnect the charger from the battery.

Unfortunately for electricity bills, the always hot transformer wasn't the answer I was looking for. Scaling up the current capacity also scaled up the energy usage. I tried it on an old battery, and working overnight it did manage to restore the battery and the transformer was less hot, the next day, after the battery was maintaining charge as if brand new.

The Hawkins charger has many excellent features, but I don't need all that going on full-time 24/7 boosting the energy bills up. I suppose it needs a miniature friend and an override circuit that can disconnect the Hawkins charger from mains until needed.

It is excellent news that the Hawkins charger has clean output. This makes it compatible with Elvee's monitor. But, the cycles are too frequent for relays to last, so I need to figure out how to do it all with solid state switch. And on that I've no idea.

Seems like multi-stage with the "little stage" an SMPS based miniature float charger. I made it already. Now I've got a little digital float charger and a big linear float charger.
I'm just a bit puzzled on adapting Elvee's circuit to Solid State switch.

 

[ChrisA]

Thanks for the link.

I've actually learned more about what I want to do.
1). SMPS very low amperage float charger for maintenance.
2). Engage a bigger stronger charger, on demand, during periods of high demand, but no connection during low demand (need to combat energy bill troubles).
3). Disconnect battery monitors from chargers when AC is unplugged (as is expected of RV use, the charger is "installed" and may spend periods of time unplugged.)
...

I don't think you need two SMPS. A larger one can work without much energy loss at very low average currents. You can use one SMPS to supply tens of amps and also a few milliamps. The key word is "average". What you do is switch the SMPS on for a few minutes every hour and then off. So to create a 10mA average you run it at 200mA for one of every 20 minutes. I think(?) this is actually better for the battery too.

The charger can use some controller uP that runs on literally micro watts this pro can be gotten from the battery during those 19 minutes when the SMPS is off.

A typical carger controller is a tiny single chip uP with three analog inputs to measure current (and and out of the battery) and voltage and temperature. It would control the SMPS. I think -pins is enough for all of that. They cost under a buck.

The main point is that to reduce the cost of float charging you can go to exactly zero mains power input during most minutes. You can reduce the power used by more than an order of magnitude that way. If you monitor the process with a uP the charger self-adapts to various size batteries.

 

[t-head]

Iota 12 Volt 15 Amp w/IQ-4

these switchmode supply/chargers work great and have proper float stage that will not kill your battery...several amperages are available...

 

[t-head]

or these that turn off at full charge and turn on again at 12.6v...they will not act as a power supply though...they will not 'boil' your battery dry...

Dual Pro 12 Volt 15 Amp