Green Building Forum - Protecting battery chargers from overvoltage Sun, 10 May 2026 02:35:31 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 Protecting battery chargers from overvoltage https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9419&Focus=153200#Comment_153200 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9419&Focus=153200#Comment_153200 Sat, 04 Aug 2012 12:35:54 +0100 GBP-Keith
Here is the scenario:
I have a 2.5 wind turbine and a number of other renewable technologies charging large battery banks. Some energy from some of my generators (hydro and some solar) is added to the batteries via simple chargers. However when the wind blows gusty (often with sunny weather) I occasionally get spikes up to 30volts or even slightly higher. This is OK to some degree as it helps equalize the batteries but I have found that it can (and is) damaging some of the chargers. The automatic (3 stage) chargers seem more vulnerable as they seem unable to keep up with the rapidly changing voltages.

I thought that some sort of blocking diode would be the answer but one charger manufacturer said that the charger will fail to see the batteries.

Any ideas please- all suggestions welcome.
Cheers, Keith]]> Protecting battery chargers from overvoltage https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9419&Focus=153201#Comment_153201 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9419&Focus=153201#Comment_153201 Sat, 04 Aug 2012 13:19:50 +0100 DamonHD
1) Have an clipper/limiter on the turbine, eg as here: http://www.earth.org.uk/wind-power-pilot-autumn-2007-MotorWind.html

2) Add a large(r)/quick dump load to help keep the battery volts down earlier so you don't get to a stage where the spikes can occur (the battery will absorb them).

I do both on a small basis with my off-grid system, and size (1) up so that (2) doesn't happen much.

A variant on (1) is to have it upstream of the rectifiers and/or so it really is only clipping/shorting or a part cycle each time which is a bit kinder to the turbine itself (else it sounds like someone jammed a poker into the blades).

Rgds

Damon]]> Protecting battery chargers from overvoltage https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9419&Focus=153209#Comment_153209 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9419&Focus=153209#Comment_153209 Sat, 04 Aug 2012 20:56:25 +0100 CWatters Protecting battery chargers from overvoltage https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9419&Focus=153283#Comment_153283 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9419&Focus=153283#Comment_153283 Mon, 06 Aug 2012 12:57:17 +0100 GBP-Keith
I'll look into the product solutions that you mention though and report back if they look promising.]]> Protecting battery chargers from overvoltage https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9419&Focus=153284#Comment_153284 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9419&Focus=153284#Comment_153284 Mon, 06 Aug 2012 13:29:12 +0100 Ed Davies Posted By: GBP-KeithI thought that some sort of blocking diode would be the answer but one charger manufacturer said that the charger will fail to see the batteries.

Dunno, but if the charger has battery sense leads separate from the actual charging cables then a blocking diode might improve matters. You'd put the diode in the charge lead and connect the sense leads directly, of course. The charger would still get confused but might be less likely to be damaged.]]> Protecting battery chargers from overvoltage https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9419&Focus=153285#Comment_153285 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9419&Focus=153285#Comment_153285 Mon, 06 Aug 2012 13:57:36 +0100 davidfreeborough Posted By: Ed DaviesYou'd put the diode in the charge lead and connect the sense leads directly, of course. The charger would still get confused but might be less likely to be damaged.What kind of diode are you thinking of? A rectifier diode will protect against reverse voltage, but only drop 0.6-1V when conducting in the forward direction. A zener diode can dump current to ground, but this wastes energy & would probably interfere with the voltage sensing.

Posted By: GBP-KeithThe problem that I see with 'earlier' dump loading is that it can waste energy (by this I mean put it where it is not actually needed) and thus prevent the batteries from filling completely during the windy period.
The only solution which avoids any loss of energy is a switch mode charger which can handle the input voltage swings. What kind of power levels would it need to handle? Do you need to maintain charging when the voltage drops below 12V? Or is the input voltage range essentially 12-30V?

David]]> Protecting battery chargers from overvoltage https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9419&Focus=153305#Comment_153305 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9419&Focus=153305#Comment_153305 Mon, 06 Aug 2012 16:22:59 +0100 Ed Davies Posted By: davidfreeboroughWhat kind of diode are you thinking of? A rectifier diode will protect against reverse voltage, but only drop 0.6-1V when conducting in the forward direction.
That kind. Possibly less than 0.6 V if a Schottky diode.]]> Protecting battery chargers from overvoltage https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9419&Focus=153306#Comment_153306 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9419&Focus=153306#Comment_153306 Mon, 06 Aug 2012 16:26:16 +0100 davidfreeborough
David]]> Protecting battery chargers from overvoltage https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9419&Focus=153311#Comment_153311 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9419&Focus=153311#Comment_153311 Mon, 06 Aug 2012 17:12:50 +0100 Ed Davies
If the charger doesn't have separate battery sense leads then the problem would be that, during charging, it'd see the battery voltage plus the forward diode drop so would stop charging early thinking the battery has 0.6 V or whatever more charge than it really has.]]> Protecting battery chargers from overvoltage https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9419&Focus=153319#Comment_153319 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9419&Focus=153319#Comment_153319 Mon, 06 Aug 2012 18:16:59 +0100 davidfreeborough
David]]> Protecting battery chargers from overvoltage https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9419&Focus=153321#Comment_153321 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9419&Focus=153321#Comment_153321 Mon, 06 Aug 2012 19:15:40 +0100 GBP-Keith
The chargers that I am talking about are conventional car/truck chargers from mains quality voltage down to 24v]]> Protecting battery chargers from overvoltage https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9419&Focus=153351#Comment_153351 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9419&Focus=153351#Comment_153351 Tue, 07 Aug 2012 08:53:56 +0100 davidfreeborough
If the input to the chargers is 240V then what's causing the over-voltage? Is the 240V also going over-voltage or just the battery side? Are you trying to combine the outputs of multiple chargers to a common point which feeds multiple batteries? Or are all the chargers feeding separate batteries? Could you draw us a schematic diagram?

David]]> Protecting battery chargers from overvoltage https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9419&Focus=153363#Comment_153363 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9419&Focus=153363#Comment_153363 Tue, 07 Aug 2012 09:54:43 +0100 Ed Davies Posted By: davidfreeboroughThe generators connect to the batteries via the chargers.
Keith's description is really rather unclear - you're right to ask for a diagram.

What I was assuming was that the battery voltages were getting too high as a result of high input currents from the wind turbines which was then confusing/damaging the other charge controllers (e.g., for the PV). The diode would have been to protect the charge controllers which were not the source of the problem. From what Keith's just written I think my assumption might have been wrong but I really don't know.

Keith, is your system AC coupled? That is, with the various generators (wind turbine and PV arrays, etc) feeding 'grid-tie' style inverters on to an 240 V AC bus which is then used for battery charging? I am right in thinking you're completely off-grid, aren't I?]]> Protecting battery chargers from overvoltage https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9419&Focus=153385#Comment_153385 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9419&Focus=153385#Comment_153385 Tue, 07 Aug 2012 13:39:07 +0100 GBP-Keith
1. The home is offgrid and is powered from batteries via a Trace 4kw inverter connected to batteries. this system does not have hardwired grid connection.
2. I also have a grid tied solar PV array that essentially connects direct to the grid independently.

I charge my batteries from a number of inputs (AC and DC). The two AC inputs relevant to this discussion are:

A: from a small AC hydro generator which charges through a car battery charger
B: the standalone Grid tie system (mentioned above) from which I draw a portion of the AC current during sunny conditions only (triggered by contactors) through a another couple of car battery chargers.

I have three battery banks (2 of which are backup/secondary on dumploads)
The main battery bank has multiple inputs, as I said including, (depending on the weather conditions) the three (24v) car battery chargers. These all use the same combined route onto the battery bank.
These AC chargers are the ones that are being disrupted and/or damaged from some unexplained 'occurrence/phenomina/state' in the off-grid system and I suspect overvoltage of the batteries.

NONE of my DC chargers, PV, wind etc are affected (so i assume protected with inbuilt kit) and at present work perfectly.

I'll draw a diagram shortly and upload it.]]> Protecting battery chargers from overvoltage https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9419&Focus=153388#Comment_153388 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9419&Focus=153388#Comment_153388 Tue, 07 Aug 2012 14:40:10 +0100 DamonHD
Rgds

Damon]]>