Small electrical motor question. 12 volts 230 Watts on Peg-Perego power wheel jeep

A lead acid, or gel cell type battery, when rapidly discharged, it can sometimes have a temporary recovery effect. I cannot remember the theory of why this happens. I can only remember something about the internal heat making the acid more active. There is a complex theory behind this.

If you know the amp hour rating of the battery, and the average amount of current being pulled from the battery, you can then make an approximate prediction of how long the battery will last between charges.

If your motor is rated 350 Watts at 12 Volts under load, this means that the motor will draw about 30 amps. If your battery is rated at 60 amps, then it should last about 2 hours, considering all conditions being perfect.

When a motor starts under mechanical load, it will draw a very large surge of current compared to its normal operation. When it has very little mechanical load on it, will draw less current. Without doing a very in debt real time analysis of the motor's current consumption, it would be difficult to accurately predict how long the battery should last.

Testing a battery when not under load, will not give a true indication to what its real loaded voltage would be. In many cases, a battery will read nearly the full charged voltage, but when loaded, it will not supply.

When I test gel, or lead acid batteries, I use a dummy load for heavy duty type batteries. I have a dummy load that will pull 10 amps at 12 volts. To test the battery, I connect the 10 dummy load across the battery, and then I monitor the battery on a DVM for at least 5 to 10 minutes. The voltage will drop a little, and then remain fairly stable if the battery is properly holding its charge.

As for safety, it is very good that you bought a sealed gel cell. If you use a liquid lead acid battery in a toy car, and there is a spillage due to abrupt use, or a roll-over, the acid can be a very serious danger. Acid spills on skin is a very serious thing! Using a lead acid battery in a device that is going to have abrupt operation, such as an electric toy car is not a very good practice.

Never use a liquid lead acid battery in your home, unless there is proper ventilation. The acid fumes, and the hydrogen gas that can be given off is very dangerous. The battery will give off most of its fumes during the time of charging, or discharging.

--

JANA _____

To being with, please accept my apologies for the noobie questions I am about to make.

Heres the info.

1. Two small electrical motors rated 12volts 230 watts powers a Peg-Perego electrical jeep. it looks like one of them power wheels ride on toys. Since the original battery died, I started asking questions and reading previous usenet posts as to replacing the expensive power wheels battery for an ordinary car battery.

I received quite a few replies. Some were cons others pros regarding the car battery adaptation idea. Apparently this has been done sucessfully before my many people. Some replies were concern as to the safety etc. Following advice from this group as well as having read meny hours of googles :), I decided to install a new heavy duty deep cycle GEL battery. It cost me almost triple as much as buying a regular 12vs car battery. However, from my own personal research as other people advices as well, it looks like this was the way to go.

I also bought an inline 40a fuse and installed it on the positive cable.

My kid took out the jeep for a ride, and he was having a blast, until..... the jeep started slowing down. WAYYY down.. almost to a crawl. This is odd, i told myself.. it surely did not seem like the so called deep cycle battery lasted any longer that the orginal small power wheel jeep battery! we are talking like 40 minutes of play time with my kid going around for a ride or two.

So I popped the hood. Checked all the cables. The positive and negative cable were warm but not Hot.. good sign I guess. I touched the battery just to get a touchy feeling.. cold.. I went under the vehicle and touched both motors. I was thinking that maybe the motors were over heating or something as that, which might caused the jeep to crawl. They were warm , not hot at all.

Took out my volt meter. Checked the battery for power.

It was reading at 11.40 volts!. thats almost a full charge.!

now heres the really odd part.

left the jeep sitting there for about 40 minutes while i went to a local canadian tire to purchase a battery charger ( I didnt have one, and since I just bought this deep cycle.. arghh.. more money ) came back. I was unpacking the goodies and noticed that my son had already jumped back onto the truck and he was doing some wheelies! all of sudden the power came back for about 5 minutes before dropping to a crawl again. Check the battery's voltage. It was reading at 11.20 volts. Had my son drive the jeep until it wouldnt move anymore to see how fast the deep cycle battery drained.. when the jeep coulnt move anymore and I connected the volt meter, it read at 10.20 volts.

now here are my questions.

If the battery is reading at 11.40 volts ( almost a full charge ) why are the motors turning sooo slow.

I know that the motors are rated at 12v 230 watts.. so if the battery drops below 11 volts should this caused the motors to simply quit turning the wheel?

I didnt check for the battery Ah rating. I took it for granted that a deep cycle battery meant for a small boat, rideon lawn mover , or even a small vehicle should be enough to put out enough juice to run two

12v motors rated at 230watts... but maybe i am wrong?

the original batteries the jeep uses are 12v 10Ah....

Could it be that the deep cycle battery may be defective? could this explain the drop of power being supplied to the motors?

Finally.

whats the best setting to charge the deep cycle battery? My charger has a setting for 10a and 2a. I am currently using 2a setting. ( trickle charge )

One day rutman got dressed and committed to text

To me the figures dont quite 'gell', since 2 motors at 230watts in theory would pull 30amps or more dependant on the wire capacity (thickness). If the original batteries were 10a/h then if the motors were used at full capacity the they would not have lasted long (the 2 motors would take 30a/h). It probably would come down to the method of speed control used and very likely the total available power of the motors was not utilised. Also the symptoms described would fit the battery not being fully charged, you should be able to charge it at 10amps, monitor the volts and when when it is around 14v and very little current flowing it will be fully charged. Of course there is much more to charging than that but it is a rough and ready way to check. See

for more info on batteries. I think I would start with a known full charge and check again.

-- Regards ..... Rheilly Phoull

thank you!

since I had the battery back on the charger while reading at 10vs, I decided to charge i for 2 hours at 2a,

it now reads 12:40 volts

question. since its jsut over 12 volts.. is this good enough or a full charge?

Most info I have read on the net, including your posts says to charge it at around 14 volts.

Until the charge volts reach 14v the battery is not charged fully, 2hrs at 2 amps is not enough. When the terminal volts reaches 14v and the current drops below 1 amp the battery is very likely fully charged. Charge at

10maps. The battery should show at least 12.8v after being disconnected for 12 hrs. The current is the clue :-)

-- Regards ..... Rheilly Phoull

IIRC, for a SLA, the magic figure is 13.8 volts.

--
*Why don't sheep shrink when it rains?

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

Your understanding of batteries needs some help. There are many good battery tech web sites, some at manufacturer's web sites (trojanbattery, for instance), and some just out there, not associated with any manufacturer. I would suggest you might spend some time on

One of the first things these sites tell us is that "A fully charged sealed VRLA Gel Cell or AGM battery ... has a terminal voltage from

12.85 to 13.1 VDC. An open circuit terminal voltage of 12.8 volts represents complete discharge."

So your initial assumption that 11.4 volts represents almost a full charge is exactly wrong. It represents complete discharge.

Re charging of gel cells, these sites tell you that "This is probably the most sensitive cell in terms of adverse reactions to over-voltage charging....If the incorrect battery charger is used on a Gel Cell, battery poor performance and premature failure is certain." I would NOT use a cheap garage-style 10amp/2amp charger on a gel cell. These chargers are made for occasional use on flooded batteries.

Bounceback, which you described, is more properly known as "surface charge". A battery is a series of lead plates immersed in an electrolyte (acid). When you charge a battery, the concentration of electrolyte (specific gravity) increases; when you discharge it, the concentration decreases. This effect does not happen evenly throughout the battery - the electrolyte that is directly in contact with the plate changes first, so that there is a thin layer of high-concentration acid against the plates. This is "surface charge". Then, as the battery sits and rests, the electrolyte slowly mixes and the concentration evens out. As a result, if you charge a battery, then take the charger off and immediately measure the voltage, it will be artificially high, and will slowly drop to the proper reading over the next half hour or so. Similarly, if you discharge a battery, then measure the terminal voltage, it will be artificially low, and then will gradually rise. This process is slower in gel batteries than in flooded batteries, because the electrolyte doesn't mix quite as fast.

What did you determine the amp-hour rating of the battery to be? More particularly, what is the suggested discharge rate for the battery? Two of the applications you mentioned (small boat, lawn-mower) are not particularly similar to the way you are using it. A trolling motor on a small boat draws a relatively small but long-term current. In the lawn mower, the battery simply puts out of short jolt to the starting motor to get the gas engine running. Then there is no further discharge.

Hope this helps

Bill

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rutman wrote:

11.40 volts might sound like close to a full charge but that's actually quite dead for an unloaded lead-acid battery. Fully charged it should be close to 13V, and the voltage won't drop off much until the battery is rather depleted. Charge it up with the high setting on the charger overnight and see how it is, there's a good chance it wasn't fully charged when it was first installed.

If you have a 100 Amp hour battery, and the charger is 2 Amps rated, it will take 50 hours to charge the battery. For the large gel cell batteries, and lead acid batteries it is best to use an auto charger that can automatically go to a trickle charge after the battery is charged. These use an auto-sense. This avoids damaging the battery if it is left on.

Typically, a 10 Amp charger is good to use to charge large batteries. Typical auto batteries are rated at about 80 to 120 Amp hours. Divide the rating of the charger in to the Amp hours of the battery to know the minimum approximate time to charge the battery.

Fast charging is not good for these types of batteries. This can cause rapid internal heating of the cells, and thus reduce the life of the battery.

When charging any type of batteries, the minimum threshold charge current must be overcome. The nominal charge current rates are published from the manufacture. The environmental temperature also has an effect on the extremes of these specs.

For most batteries, a charge current of 25% of the Amp hour rating is the maximum that should be used. On the average, the minimum charge current should be in the area of about 5% of the Amp hour rating of the battery. This means that for a 100 Amp hour battery, a 5 Amp charger is the smallest size that should be used to charge it efficiently. The charge time would be

20 hours minimum.

For my auto batteries, I have a 15 Amp auto charger. It charges at 15 Amps maximum. After the battery is charged, it goes to a lower current. It auto senses the battery. It has a meter that reads out the charge rates. As the battery reaches full charge, I generally see it sinking down below 2 Amps. After about 24 hours, it is at about 1/4 of an Amp. If I leave it longer, I sometimes see it climb to about an Ampere for a while, and then sink down again. This is when it is doing what they call a float charge.

A typical 12 Volt acid type battery when tested with no load, should read about 13.2 to about 13.5 Volts right after the charger is removed. During the charging, it should read about 13.8 to about 14.5 Volts. These are approximate amounts. After the battery is sitting for 24 hours with no charger attached, the no load voltage should read about 12.5 to about 13.2 Volts average.

When the typical 12 Volt acid type battery is loaded to 25% of its capacity, it should typically read about 12.3 to about 12.7 Volts for about 50% of its rated capacity period. When the battery reaches 10% below its nominal rated voltage, it would be considered discharged. This would be about 11.2 to about 11.5 Volts for the average 12.5 Volt acid type battery.

I hope all of this explains things.

--

JANA _____

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thank you all for your informative replies. I have learned a lot in the last few days!

I am now read>A lead acid, or gel cell type battery, when rapidly discharged, it can

I wouldn't worry about it, you've got a line fuse that'll protect it from overload.

Thermal fuses are used to protect motors etc against overheating so should be mounted in contact with the windings.

--
*What hair colour do they put on the driver's license of a bald man? *

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.