Our team is building a new battery cart and we are thinking of getting this charger:
However, it charges at 10A, which I am pretty sure is too much for robot batteries. Does anyone know if there is a way to lower the amperage on these things?
Why not use the one AM sells?
I understand that it’s a bit more expensive, but it really works great and charges insanely fast.
Im not sure where but i believe i saw a charger similar to the andymark one but that charged 5 batteries instead of 3… it looked like it mounted on a wall too. Wish i knew where i saw it.
Yeah, the Dual Pro RS3 is our other option, but it is more expensive. This is another three-bank smart charger, I was just wondering if it is any good for robot batteries.
I recently bought the 4-bank version of the same charger. It appeared to be working well at first, but it isn’t really working for us. It declares a battery to be fully charged way too early, goes into trickle charge for a few minutes, then stops entirely. When this happens, it indicates full charge, no errors.
It is not specified to work on batteries as small as FRC batteries (it specs a range of 25-230 A-hr, our batteries are 18 A-hr). It was probably a mistake to have assumed that a “smart charger” would be smart enough to adjust itself to the size of our battery. Some on our team believe it ought to work anyway (might be a little harsh on the battery and possibly reduce lifetime, but it should still work), so ours might be defective. We’ve tried other experiments with it that suggest it isn’t really working correctly. I plan to call the company and ask about it. I doubt I can return it, because we already cut the wires to put Anderson connectors on.
The unit is completely sealed, so I don’t believe there is any way to adjust the current output. If I can’t return it, I might crack it open and see if there’s anything I can change.
I’ve looked for another charger that has 4 or more banks, with 6 Amp outputs, but I’ve had no luck so far. It looks like the Dual-Pro, sold by AndyMark, is the best choice. I’d like to hear from anyone who finds a good charger with >= 4 banks and 6A each. I’d even be willing to make a summer team project building one, if I found a good plan for it.
Ok, that’s what I needed to hear. I guess we will be getting the Dual Pro then.
The charger you linked is designed for batteries in the 25-300 amp hour capacity. Our battery is an 18 amp hour and neither of the manufacturers allow charging at over 6 amps. This charger may not be used for FRC batteries and may not be used in the pit.
(Quoting myself, to give an update)
We bought the Dual-Pro 3-bank charger, and used it at our second regional competition. We were very happy with it. Although we had brought a couple of standard single chargers as backup, the Dual-Pro was sufficient to carry us through the entire competition. We rotated through 5 competition-quality batteries, and this charger was able to keep them fully charged all weekend.
And, repeating my “challenge”:
I think this is the one i was thinking of before, not sure if it’s appropriate for the batteries we use. Can anyone with a better understanding verify if this would be a good option?
http://www.accumate.com/pro5/index.php
Steven,
While this charger would be safe to use on our batteries, the brochure shows it generating only 1.8 amps of charge current. This will charge the battery if you have a long time but in the heat of competition, this will not give you the results you hoped for.
I think this is the one i was thinking of before, not sure if it’s appropriate for the batteries we use. Can anyone with a better understanding verify if this would be a good option?
http://www.accumate.com/pro5/index.php
Yes Steven, the Accumate 5 is indeed a good charger!
Al, both my teams use the TecMate Accumate 5 and they work great. If you have 5 batteries on the go you will always have a couple ready for your next match. Both my teams run heavy draws on their batteries running 6 motor drivetrains and the Accumate keeps up just fine. With this charger you can also combine multiple charging ports to increase the charge rate ie: 1.8A from 3 bays = 5.4A if you need to get a battery charged FAST. They are a great charger and you can safely leave the batteries plugged in and charging as the unit is fully automatic and includes a long-term maintenance feature. It also has integrated diagnostics and has served invaluable in notifying us of defective batteries before they cost us a match. We picked up ours at a dealer cost of $239. The cybergnomes’ title sponsor, JT’s Snowmobile uses them for all their batteries and let us try it out for our competition in 2010. Since then we have never looked back.
Fox,
You are not saying you parallel the outputs into one battery are you?
Yes- as quoted from the product website:
•Two or more charging stations can be connected to the same battery when faster charging of larger capacity batteries is required.
That just sounds wrong to me. If the two chargers are not synced (and it is highly unlikely they are) and calibrated the exact same way, one may go into load test while the other is supplying current. If not closely calibrated, then one charger may go into secondary charging while the other is in primary charging.
Our team uses the 3-Bank chargers from AndyMark and they work great. We’ll actually be switching out the other 3 1-Bank chargers we have for two more when we get the money.
-Nick
That just sounds wrong to me. If the two chargers are not synced (and it is highly unlikely they are) and calibrated the exact same way, one may go into load test while the other is supplying current. If not closely calibrated, then one charger may go into secondary charging while the other is in primary charging.
I used four banks to charge the 100AH on-board battery on one of our carts and it seemed to work flawlessly. I don’t know that it is that hard to see multiple bays working together- The charger likely senses current to identify when a battery needs to be charged and when it has had enough. If they are all running in parallel, the current the battery will accept is split between them all and assuming all the transformers are identical, they all put out the same voltage and hence see the same current. When the current drops to a level that each individual bay is happy with, it shuts down into maintain mode which applies a slightly lower voltage to the battery. If that bay is seeing a higher voltage than its maintain cycle (ie other bays are still in charge mode) it likely just sits in maintain mode and each bay will eventually shut down as each one becomes content that the battery is drawing a low enough current to indicate fully charged. I never witnessed the entire charge cycle because it charged overnight but I would expect each bay would switch to maintain mode one at a time depending on their sensitivity and calibration so you would end up with a 7.2A > 5.4A > 3.6A > 1.8A main charge cycle as the battery approached full capacity.
Fox,
What I am thinking is that many smart chargers switch between charge and load during the charge cycle. This allows them to determine the state of charge in the cells. This switch cannot be synchronized between individual chargers. So if these chargers do indeed switch, they cannot all do that at the same time. In the better case, one charger feeds current into another and little or no current passes to the battery. In the worst case, the chargers become confused and add current when the battery is at a point where the charge current should back down. Damage would result over time in that second case. In the maintain mode, the switching is likely to play havoc with voltage sense. I would run some tests with a load current tester like the CBA III to determine the load characteristics of a battery charged under a three charger 5.4 amp run and that of a 6 amp one charger run.
What I am thinking is that many smart chargers switch between charge and load during the charge cycle.
I’ve had a fair bit of experience with batteries from being involved with radio control aircraft. The majority of chargers use current sensing to determine the charge condition of conventional batteries. For a specific voltage, current approaches 0 as the cell voltage approaches the applied charge voltage. When this happens the charger switches from a “charging voltage” in the case of the accumate 5, it is 14.3V as illustrated on the graph of charge schedule on their website. Once the current drops to a predetermined rate, the charger goes into a “mantain” or trickle charge mode where it applies 13.5V. It holds this voltage unless it senses the current draw to exceed a threshold indicating the battery is accepting more charge due to a depleted state. It then switches back to charge mode applying 14.3V. This is the same method used by the KOP battery chargers which have the yellow and green light that flip flops back and forth as the battery approaches a fully charged condition. The yellow light indicates a charge cycle, the green, a maintain cycle.
Should you use more than one of these chargers on a single battery, they will each apply a charging voltage. Power will not backfeed into the charger as I understand they are equipped with a diode to prevent this. When they are both applying their 14.3V charge voltage, if the total current being drawn by the battery is greater than the 2x the threshold current which kicks the chargers into their maintain cycle, they will continue holding a 14.3V charge cycle. As this current drops and approaches 2x the threshold current, the more sensitive of the two chargers will kick into maintain mode of 13.5V. Since the other charger is still applying 14.3V it will see a jump in current which will keep it in its charge cycle. When the current drops to the threshold limit again, the second charger should kick off and both will continue in their maintain mode.
http://www.accumate.com/pro5/images/product/ampro5_table.jpg
Why do you think that it is unlikely that the charge controllers on multiple banks are linked? They are all in the same housing, in the same unit.
I would think that if the manufacturer advertises that it is acceptable to bridge the banks, I would bet that the system has been designed to do this.
Fox,
The point at which the chargers are sampling cell voltage, applying charge current and checking for load conditions are made at the processor level within each smart charger. There is no easy way to sync those cycles within multi chargers. Multiport chargers in the majority of cases, are simply multiple chargers within the same enclosure, with a common power line connection. I know that our six port charger that is available from many sources including McMaster is connected this way.
In my discussions with MK lab personnel and the Battery Council International here in Chicago, there are many “recommendations” made by manufacturers that are simply not good practice. In the case of simple chargers, where no switching/monitoring/status takes place, multiple outputs can be combined IF the chargers are connected to the same power-line phase and the total current does not exceed the max charge current specification.
Please note that the curves shown above also demonstrate the charge current during and after the addition/removal of an additional load in parallel with the battery charger.
Al, what is this six port charger you speak of? Specs and/or link would be great.