NiMh and Minus Delta V -Δ Circuit or a Smart Charger directly to a solar panel

[nuambenzina]

As regarding NiMh and Solar Panels I have some questions in my mind and I can not find the answer by myself, and I had browsing the web from about 6-8 moths now for nimh+solar panels comobo, circuits, devices, but I haven’t found the answers to my questions.
If you know the answer, please have patience to write a reply…

Thank You in advance!

Using Solar Panel, NiMh and Minus Delta V -Δ v Circuit or “Smart” Charger

A)
If between the solar panel and a 1.2V NiMh cell is a diode and a Minus Delta V -Δ v circuit will prevent the overcharging?

B)
I have seen a lot of “Fast” and “Smart” NiMh chargers, from various manufactures like Varta, Maha, etc. which use the Minus Delta V -Δ v, Time Countdown, Temperature Sensor, Trickle charge, They could charge one NiMh cell from 15 minutes to 2 hours or maybe more.

It is OK to connect a NiMh Charger DIRECTLY to a Solar panel, with the NiMh batteries in it and LEAVE IT for a while, 1 week, 1 month, 6 months, 1 year, 2 years, etc with the batteries inside?

- The solar panel can be 5-6V or a solar panel which gives 12V-17V
- The NiMh charger will have Minus Delta V -Δ v, and Temperature sensor as a nimh with time control will “reset” every night, so is usless or that time control is set at 15minutes to 16 hours varying by the model.

The NiMh charger it can be connected directly to a solar panel (plus a diode) and can be left with batteries inside for undefined period of time?

Varta Professional Line Digital USB Type 57048
The Url to the charger

http://www.varta-consumer.com/en/Products/Chargers-12/Professional-Line/V-MAN-Home.aspx#Digital-USB

An image with the back of the charger from the internet




I have saw cool and very good NiMh chargers that but they require 100-110V, so they are excluded as I wish a solar panel with NiMh and a tension of 4.5v, 5V, 5.5V, 12V. Maybe maximum 24V, but for sure Not 100-110V or 220V.

[Sunking]

It is OK to connect a NiMh Charger DIRECTLY to a Solar panel, with the NiMh batteries in it and LEAVE IT for a while, 1 week, 1 month, 6 months, 1 year, 2 years, etc with the batteries inside?

Yes as long as the Panel Imp is C/10 or less. See your other post for detailed answer.

[inetdog]

[CENTER]
The NiMh charger it can be connected directly to a solar panel (plus a diode) and can be left with batteries inside for undefined period of time?

Varta Professional Line Digital USB Type 57048

1. Depending on the details of the charger, it may be damaged by the ~18 volt open circuit voltage of a nominal 12 volt panel if there are no batteries in the charger.
2. The circuitry of the charger may be confused and not run a proper charging cycle if the voltage from the panel drops because a shadow falls on the panel or a cloud goes by.
The delta-v detection circuitry in the charger may not work properly is the input voltage is very unstable.

[PNjunction]

Both of those points hit the nail on the head.

To the op: Get serious and at least look at the manuals and faqs for Maha / Powerex nimh chargers. They do it right, and freely document how and why they do it. Then reevalute the shortcuts the other chargers take (both high and low end), and you'll be good to go. One of the first things one discovers is that in order to make the cell generate a decent delta-v signal, you have to charge it at the C/5 rate. Anything less and you are risking running into one of the other safeguards (time, temperature, over-voltage etc) unless you are doing a dumb timed slow charge that doesn't generate this signal.

Also note that a great chargers with CRAP batteries is a waste of time. I'd also recommend visiting Candlepower forums for further study.

[nuambenzina]

I've read all what is written here in the replays, and I'm not confused about this combo anymore.

Thank you all for your input!

[Sunking]

I've read all what is written here in the replays, and I'm not confused about this combo anymore.

Thank you all for your input!

Sorry you got confused but maybe this will help.

You can leave a NiCd or NiMh battery on a constat current charge forever if the charge current is C/10 or less. At C/10 or less it will not overheat or vent, just remain full charged. For example cordless phones and a lot of power tools that have NiCd or NiMh batteries in them have constant current chargers in the C/20 range so they can remain in their charger bases forever and stay charged up ready to use. Higher end power tools that have fast chargers have some smarts built into them to charge quickly then either sut off or fold back charge current when charged up.

OK a solar panel is a current source, not a voltage source. So if you select a solar panel with a Imp of C/10 or less of the chosen battery it is real simple to make a NiCD charger. All you need ius a diode to prevent the battery from back feeding the panel and from discharging the battery at night or when cloudy. So for example lets say you want to charge 6 NiCd cells in series and the cells are rated at 10 AH. You want to find a solar panel with a Imp = 1 amp or less and a high enough voltage to continuously push 1 amp into the batteries. In this example you are looking for a standard 12 volt battery panel rated at 10 to 17 watts. A 10 watt panel can only deliver a maximum of .6 amps while a 17 watt panel can only generate a max of 1 amp. You could even go as low as a 5 watt panel.

The only compromise of charging at C/10 or lower is longer recharge times. For a fully discharged battery could take 2 or 3 days in summer and up to a week in winter depending on your location.