I think it would be a good idea if the participants of this site test some of the 12 volt chargers that are available on the market and enter the results here so we can decide which charger would be best for our uses.
I think we agree that series charging batteries can damage the batteries if one or some of the batteries are not the same resistance as the others. The only way this charging method works is if the batteries are a perfect match. Small differences can be compensated for with battery balancers. The other method is to use separate 12 volt battery chargers and charge each battery individually. I have purchased 5 different 12 volt chargers and I will be testing them and entering the result here. To test the chargers I will use a Kill-A-Watt meter and volt meter. In some cases I will also subject the chargers to different temperatures to see if they have any voltage compensation for temperature changes.
Eric Fisher
www.SiliconeBatteriesUSA.com
I purchased a Black & Decker 2 amp Charger Maintainer from WalMart for less than 20 dollars. Here is a site where you can see a picture of it.
http://boatandrvaccessories.com/VEC-080BD.htm
I tested the charger on two different batteries, a 4 year old 12 amp hour gel cell from a electric scooter and an 8 month old large 100 amp hour Greensaver silicone battery, normally used in an electric car. The results are as follows. The Charger has two settings, 2 watts or 1 watt. I chose the 2 watt setting. The Kill-a-Watt meter indicated 34 watts when I starting the charging. After sometime, the voltage came up to 14.4 volts and did not increase above that. As time went on, the watt meter indicated a drop in watts while the voltage stayed at 14.4 volts until it got to 13 watts. At that time the watt meter suddenly went to 1 watt and the chargers charging light went out. In time the voltage dropped down to 13 volts. The charger stayed at the 1 watt draw, not attempting to charge the battery. I put a load on the battery to make the voltage drop. Finally at 12.55 volts the charger turned back on and went through a charging cycle, back up to 14.4 volts. The results remained the same for either battery. I tried the 1 amp setting and found it started charging with a draw of 18 watts, all other result were the same. I am sure this charger does not have temperature voltage compensation so I did not test it at different temperatures.
Eric Fisher
www.SiliconeBatteriesUSA.com
The behavior of the charger looks about right for a typical CC-CV type charger.
The input watt meter declining as the voltage holds at 14.4 volts is just the charger going through a normal CV stage. The current declines as the battery approaches full charge, so the power used goes down. The 14.4 volts (2.40 volts per cell) you measured is a good warm-weather cutoff voltage (above 25C/77F). As far as the 13.0 volt value, this seems low for a float charging setting, as just a fully charged battery under no load would normally be 13.3 to 13.5 volts. Maybe the charger is just shutting off.
I was in Walmart looking at Chargers and saw a new one. This is a Schumacher SC-1200A. The cost only $43.74 so I bought one. Below is a link if you want to see one.
http://www.homeandbeyond.com/prod-0118913.html
This Charger is very light about 5 pounds. It has lots of features. You can select 3 battery types and 3 amperage setting. I did testing on several different batteries and discovered that there was no difference in the performance with different sizes of batteries. No matter what amperage setting you chose the charger would come up to a max voltage of 14.5 when selecting the Gel setting and 15.3 volts in the AGM setting and 15.6 volts in the normal setting. During charging the Kill-a-Watt meter would start as high as 210 watts in the 12 amp setting to 50 amps in the 2 amp setting. Regardless of the amperage setting, when the watts dropped to 22 watts the charger would suddenly stopped charging and the charge light would go out. The watt meter would then drop to 9 watts probably the amount it takes to keep the fan operating which runs all the time. After a few minutes the voltage drops to 13.5 volts and the watt meter went to 10 watts. This is the float voltage for this charger apparently. The charger never let the volt dropped below 13.5 volts. I tried to see if temperature would change the charging voltage by putting it in my oven with a controlled temperature of 120 degrees. This made no difference in the charging voltage.
Eric Fisher
www.SiliconeBatteriesUSA.com
It's best to use the Gel setting then. 15.3v is too high for most AGMs at room temperature, and 15.6v is way too high.
[url=/forum-topic/motorcycles-and-large-scooters/587-my-kz750-electric-motorcycle-project]KZ750 Motorcycle Conversion[/url]
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Pic from http://www.electri
I notice that some people were buying Battery Tender chargers so I went looking for one to try. I was hoping to find one in the 2 to 3 amp range. Well forget that it goes from 1.25 amp to 5 amp nothing in between. I went with the 5 amp model. It was a little expensive with shipping it was nearly 90 dollars. Here is a link below so you car see it.
http://www.batterymart.com/p-battery-tender-plus-12v-5a-wp-battery-charger.html
This is a heavy charger compared to the others I have tested it weighing about 4 lbs. I think this is an old design one without the new high frequency charging technology. I hooked it up to a battery and plugged it in. The Kill-a-Watt meter went up to 100 watts and stayed there for quit some time until the charge voltage came up to 14.7 volts. The voltage stayed there as the watt meter dropped until it reached 10 watts. At that time the charge light went out and the watt meter went to 1 watt. The voltage slowly dropped until reaching 13.35 volts. At this point the the watt meter went up to 2 watt. The voltage never went below 13.35 volts. I test it at different temperatures but it did make any difference in the way it charged.
Eric Fisher
www.SiliconeBatteriesUSA.com
I purchased a B&D 6/4/2 Charger some time ago at Walmart for $26.99. I charged a 70 amp hour battery that was at about 80% charged. I used the 6 amp setting. The voltage came up to about 14.0 volts initially and continued up to 14.8 volts but never went higher. At this point the Kill-a-watt meter started to drop from 120 watts until it got to 26 watts over a period of several hours. Moments after the watt meter reached 26 watts the charger beeped and showed a light that indicated that the charge was complete the watt meter went to 3 watts which was the power being used to run the fan that does not turn off. After about 5 min. the Voltage dropped to 13.35 volts. At that time the charge complete light went out and the charger started charging again. Within about one min. the voltage rose to 14.1 volts and the charger beeped and the charge complete light came on again. The cycling continued in this same pattern. This is how the float cycle works I guess.
I also tried this charger on a smaller battery but with the 2 amp charge setting. The results were similar with 40 watts at the start and the charge complete point at 26 watts and the float cycle was the same as the earlier test
Eric Fisher
www.Siliconebatteriesusa.com