question for anyone currently using a battery tank

garfin · 01-16-2004, 10:34 AM

I've purchased a 12 volt 5ah battery for my tank up at radioshack and have just made the logical realization that a charging lead-acid battery can release some pretty toxic/flamible fumes. Has anyone out there had any trouble with fumes or have any suggestions as to where it should be mounted? (should it have vents leading outside?)

shakes · 01-16-2004, 01:23 PM

well mine isn't installed yet ... but i put one in a guy's car and he hasn't complained yet

i don't think it'll be that big of a deal from one battery and the tiny bit of charging you'll be doing. it won't loose much power at all during cranking so it won't need to charge much.

I would put it somewhere in the dash or in the engine compartment/trunk if possible ... not around any air ducts

NightHunter · 01-16-2004, 01:27 PM

It is best to install it under the hood(engine compartment). IF there are any fumes, I dont think you want that uder your dash or in the trunk. All though I have seen a lot of setups with batteries in the trunk, especially with audio system and cars with hydraulics. But if you can fit it under the hood, it is the best place.

robiewp · 01-16-2004, 01:28 PM

Unless I'm msitakein anything from radio shack would be sealed... no worries there

sigma957 · 01-16-2004, 02:15 PM

From what I have read, no SLA battery is truly "sealed". They all have some sort of overflow valve that will vent gases if the battery is over charged or charged too rapidly. It should therefore only be charged in a ventilated area.

I have a small SLA battery that I've mounted right in the computer case. I have it isolated from the electrical system of the car by a diode, so it does not charge in the car. Every couple of weeks I take it out and connect it to a charger to top it off, but it rarely loses much charge since it is only drawn from when cranking.

garfin · 01-16-2004, 03:21 PM

Thanks for all of the great replies, I had not even considered putting it in the engine compartment, but that definetly sounds like the best place for a battery of this size.

VWTronics · 01-22-2004, 12:44 PM

Question of the day for you guy's...... if you have the battery setup up and running what did you end up using for a diode (ie. source and size) ???

shakes · 01-22-2004, 01:35 PM

MBR3045 or MBR6045 (i think those are the part numbers) ... search digikey.com for it

the 3045 has a lower voltage drop

VWTronics · 01-24-2004, 03:39 PM

Quote: Originally Posted by shakes

MBR3045 or MBR6045 (i think those are the part numbers) ... search digikey.com for it

the 3045 has a lower voltage drop

I have never used a MBR 3045 type diode before.... being that it looks like a regulator LM style regulator how do you conect to it? If any one has some pictures / drawings it would be much appriciated

T,
VWT

shakes · 01-24-2004, 04:24 PM

each package actually has 2 diodes in it ... the two outter pins are the annodes and the center pin is a common cathode.

so if you only need one diode you will only use the center pin and one outter pin.

you can sorta see something like this in the circuit i made here ... the center pin is bent abck and soldered to that red wire ... one of the outter pins (upper) is bent around connecting to the fuse, and one (lower) is bent conntected to the resistor. i needed both diodes for this circuit. you may only need one.

and you can get a datasheet for this diode from digikey.com ... it shows the pinout as well.

VWTronics · 01-26-2004, 10:54 AM

Shakes,
In your setup you are using a 25W, 20 Ohm resistor...
Not to be a pesk, but how did you come to that conclusion?
I was trying the math, and did not understand this one?

To give you my info:

Pw-70, ITPS, 12V 2.7Ah Battery, and the MBR3045 Diode.

By the way, thanx for the privous help and information.

T,
VWTronics

shakes · 01-26-2004, 11:48 AM

it's 20Ohm 20W ...

I have a 7Ah SLA ... ideal charging current for most SLAs are 1/10th the Ah rating. So i needed to trickle charge my battery at .7a (as pointed out to me by Ricky327 ... this should also be confirmed in your battery's datasheet)

so using our trusty v=ir ... 13.8v / .7a = 19.someodd ohms. 20 is close enough.

I used 13.8v bacause that is close to the voltage applied to the battery when the car is running. My alternator provides about 14.2v (if i remember right) when the car is running, and the diode i use has a .4v drop.

As for the watts ... just choose something high enough to allow for enough current to flow. with 20W i'll be able to pass 1.5a at 13.8v ... plenty.

VWTronics · 01-26-2004, 01:05 PM

Shakes,
Thanx for clarifying that one.....the reason for the question was that I ordered parts from Digi-key based on the diagram that is floating around for the battery tank circuit and it called out for a 68 Ohm 3Watt resistor…… this could work in a setup using a 2.7Ah battery, but would only give .203A under charging (less that the 1/10 rating). The max draw would be 2.8 Watt’s,

By the way, is your setup the same way as this one?

http://www.mp3car.com/vbulletin/atta...tid=1134&stc=1

shakes · 01-26-2004, 01:47 PM

mine isn't currently set up like the image you posted. that's Ricky's design that helps give your battery a little extra charging voltage because there's no diode between the source and the battery to drop the voltage. the downside is it's possible for your sla to drain a little back into your car's electrical system. Ricky's tested for this and found the issue to be minimal.

I'm using the design that looks like that with the exception that the top diode is before the resistor and both diodes are MBR 3045s.

you'll notice his drawing has a .8Ah battery ... so he needs less charging current.

You may be better off with a smaller resistor (closer to 50 Ohms) but if you've already made your order try it and see what happens. less charging current means it will just take longer to charge ... as long as the voltage is high enough you'll still be able to get a full charge. the SLA won't drain that much during crank.

just build it and test it ... you might be just fine.

Quote: Originally Posted by VWTronics

Shakes,
Thanx for clarifying that one.....the reason for the question was that I ordered parts from Digi-key based on the diagram that is floating around for the battery tank circuit and it called out for a 68 Ohm 3Watt resistor…… this could work in a setup using a 2.7Ah battery, but would only give .203A under charging (less that the 1/10 rating). The max draw would be 2.8 Watt’s,

By the way, is your setup the same way as this one?

http://www.mp3car.com/vbulletin/atta...tid=1134&stc=1

ayasystems · 05-07-2005, 08:00 AM

Quote: Originally Posted by sigma957

From what I have read, no SLA battery is truly "sealed". They all have some sort of overflow valve that will vent gases if the battery is over charged or charged too rapidly. It should therefore only be charged in a ventilated area.

I have a small SLA battery that I've mounted right in the computer case. I have it isolated from the electrical system of the car by a diode, so it does not charge in the car. Every couple of weeks I take it out and connect it to a charger to top it off, but it rarely loses much charge since it is only drawn from when cranking.

I have a same instalation... and I have the same problem the battery don't charge in a car. I don't Know how charge the SLA. Have you any circuit?

Greetings

(I'm from spain, sorry my bad english)