Was there a technical reason for this charging setup ? - Page 1
Forum section: electronics / projects

author: Back2Volts
author_rank: Unknown
timestamp: April 16, 2017, 02:11:59 am
content: I have an electrical, battery powered wheelbarrow. I purchased it a couple of years ago; this will be the third season that it will help wife and me with the yard work. While it does have some design deficiencies, it does help moving loads around, specially up hill. My immediate concern relates to the battery charger attachment.The two 12V lead batteries are in a steel box under the bucket. The battery box has what looks like a regular IEC320 socket. During normal operation, a cable with a matching plug connects the battery box to the electronics box which is somewhere between the wheelbarrow handles. To charge the batteries, this cable has to be unplugged before a 24V, 1.2A charger is can be connected to the battery box. The socket is rather hard to access for me, having to get on my knees. For my wife, the real gardener, it becomes an impossible operation. We are not that young anymore...I have the feeling that the product was put together using parts for eBikes: motor, motor controller (24V/14A) and speed/direction handle control. I also have the feeling that "inventor" guy from Minneapolis had very little clue about electronics.My questions:1. Could there be a technical reason for this awkward charging requirement, having to disconnect the electronics while charging ?2. I would like to install a jack to facilitate charger hookup. Could there be problems inserting the charger without disconnecting the electronics? If yes, I may need something like a 30A relay to separate the circuit while charging.I hope I have explained properly the issue. If not I can post a picture.Edit: it uses lead batteries.

author: digsys
author_rank: Unknown
timestamp: April 16, 2017, 02:39:45 am
content: If it was built from EV parts, the requirement to unplug before charging is likely for safety reasons only. ie you can't drive off with the charger attached.As long as you don't accidentally run it while charging, you're good to go. There may be a small quiescent current draw by the electronics, and that should be ok as well.Chargers don't like large changing loads while they're trying to do their job. You won't need a Relay, just see if there is a power switch to the electronics, and maybe addone if it doesn't.

author: rstofer
author_rank: Super Contributor
timestamp: April 16, 2017, 03:52:34 pm
content: I imagine a situation where the battery bank is toast. One of the cells has opened up. When the charger is plugged in, there is no load on the charger and the output voltage is quite high. If the only load on the charger is the battery bank, no harm, no foul. But the drive electronics might not want to see a voltage much higher than the battery voltage and that's the reason for separating the drive electronics during charging.I'm supposing a battery charger with a very high open circuit output voltage (essentially unregulated voltage) and a drive that can't handle high voltage on the output. I don't know that this is the case but I would pretty much bet on it.

author: Ian.M
author_rank: Super Contributor
timestamp: April 16, 2017, 04:38:35 pm
content: Can you simply install a matching plug/socket pair inline at the handle end of the cable? Then you could connect the charger there instead of having to nearly crawl underneath it.

author: sahko123
author_rank: Frequent Contributor
timestamp: April 16, 2017, 06:36:28 pm
content: This also may be to make the battery easily replaceable and also to reiterate another reply it will be for safety and also to speed up the charging by disconnecting the load/electronics..in other words i don't see what would be wrong with having the electrics still intact when you plug in the charger. However the 1.2 amp charger may be overloaded.Try test to see if the electronics themselves run of the 24 volt or 12 volt.

author: Back2Volts
author_rank: Unknown
timestamp: April 16, 2017, 07:02:31 pm
content: Quote from: rstofer on April 16, 2017, 03:52:34 pmWith no load the charger provides 27.5V, which is 3.5V above the controller rating. It guess it could exceed the 24V rating of the generic controller. It may have 25V capacitors.

author: Back2Volts
author_rank: Unknown
timestamp: April 16, 2017, 07:22:04 pm
content: Quote from: digsys on April 16, 2017, 02:39:45 amIt has a switch. Originally one of those cheap Chinese toggle switches, round, nickel size, red plastic. It failed probably for being under rated and no weather proofing at all. I replaced it with one with silver contacts and rubber boot. It may be SDST, but I could replace it with SPDT and switch the battery line to the charger jack when in the OFF position.

author: Back2Volts
author_rank: Unknown
timestamp: April 16, 2017, 07:47:01 pm
content: Quote from: sahko123 on April 16, 2017, 06:36:28 pmNo doubt that having a connector on battery box is a good idea for serviceability. In fact the box is held in position by two spring loaded steel prongs and can be removed easily. What I object to, is having to crawl down to it for charging. Personally it also bothers me that they used an A/C plug for it. Just wonder what would happen if someone unfamiliar with it, tried to use a PC power cable plugged to mains. They should have engineered something more adequate for DC. More so that here in Minnesota, we are used to some heavy two prong connectors often used in boats. I guess the guy was not a fisherman.There are just two wires feeding the electronics. No center tap; it works at 24V.

author: Back2Volts
author_rank: Unknown
timestamp: April 16, 2017, 07:58:39 pm
content: Quote from: Ian.M on April 16, 2017, 04:38:35 pmYes, but once I extend / relocate it, I rather use regular DC power plug and jack, like a 2.5/5.5mm weatherproof plug and jack with a rubber stopper. It would not be the first time this wheelbarrow catches some rain.http://www.mouser.com/ProductDetail/Switchcraft/761KS15/?qs=sGAEpiMZZMtnOp%252bbbqA00%252bEHFRoiCocrqZwaRZOYUDY%3d

author: Zero999
author_rank: Super Contributor
timestamp: April 16, 2017, 10:42:23 pm
content: Quote from: Back2Volts on April 16, 2017, 07:02:31 pmThat's a pretty standard voltage for two 12V lead batteries in series. The electronics will certainly be able to handle 27.5V because that's what you'd expect when the batteries are hot off the charger. If they used components rated to anything less, then they're idiots. It's highly likely the electronics will be able to withstand 30V or higher.